feat: merge develop into hare/develop

crates/agen/src/engine.rs

@@ -2275,6 +2275,9 @@ impl<C: LlmClient, S: EngineState, A: Send + Sync> Engine<C, S, A> {
                         info!("Paused during response stream");
                     }
                     self.timeline.abort_current_block();
+                    // Preserve any UsageEvent already received for billing, but
+                    // do not treat this paused request as a normal completion.
+                    self.timeline.flush_usage();
                     return Err(EngineError::PauseRequested);
                 }
                 cancel = self.cancel_rx.recv() => {

crates/agen/tests/engine_state_test.rs

@@ -7,6 +7,7 @@ mod common;
 
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex};
+use std::time::Duration;
 
 use agen::Item;
 use agen::interceptor::{
@@ -18,16 +19,67 @@ use agen::interceptor::{
 };
 use agen::llm_client::{
     ClientError, LlmClient, Request, ResponseStream,
-    event::{Event, ResponseStatus, StatusEvent},
+    event::{Event, ResponseStatus, StatusEvent, UsageEvent},
 };
 use agen::tool::{Tool, ToolDefinition, ToolError, ToolMeta, ToolOutput};
 use agen::{Engine, EngineError, EngineRunExit, History, RunInterruptionReason};
 use async_trait::async_trait;
 use common::MockLlmClient;
+use futures::StreamExt;
 
-// =============================================================================
-// Mutable State Tests
-// =============================================================================
+#[derive(Clone)]
+struct UsageThenPendingClient;
+
+#[async_trait]
+impl LlmClient for UsageThenPendingClient {
+    fn clone_boxed(&self) -> Box<dyn LlmClient> {
+        Box::new(self.clone())
+    }
+
+    async fn stream(&self, _request: Request) -> Result<ResponseStream, ClientError> {
+        let usage = Event::Usage(UsageEvent {
+            input_tokens: Some(90),
+            output_tokens: Some(2),
+            total_tokens: Some(92),
+            cache_read_input_tokens: Some(0),
+            cache_creation_input_tokens: Some(0),
+        });
+        Ok(Box::pin(
+            futures::stream::once(async move { Ok(usage) })
+                .chain(futures::stream::pending::<Result<Event, ClientError>>()),
+        ))
+    }
+}
+
+#[tokio::test]
+async fn pause_during_response_stream_flushes_observed_usage() {
+    let observed = Arc::new(Mutex::new(Vec::new()));
+    let observed_for_callback = Arc::clone(&observed);
+    let mut engine = Engine::new(UsageThenPendingClient);
+    engine.on_usage(move |usage| {
+        observed_for_callback.lock().unwrap().push(usage.clone());
+    });
+    let pause = engine.pause_sender();
+    let mut history = History::new();
+    let mut engine = engine.lock(&history);
+
+    tokio::spawn(async move {
+        tokio::time::sleep(Duration::from_millis(20)).await;
+        pause.send(()).await.unwrap();
+    });
+
+    let exit = tokio::time::timeout(
+        Duration::from_secs(2),
+        engine.run(&mut history, "pause after usage"),
+    )
+    .await
+    .expect("run should observe pause");
+    assert!(matches!(exit, EngineRunExit::Paused));
+    let observed = observed.lock().unwrap();
+    assert_eq!(observed.len(), 1);
+    assert_eq!(observed[0].input_tokens, Some(90));
+    assert_eq!(observed[0].output_tokens, Some(2));
+}
 
 /// Verify that system prompt can be set in Mutable state
 #[test]

crates/client/src/backend_runtime.rs

@@ -943,7 +943,7 @@ mod tests {
             profile: Some("builtin:coder".to_string()),
             ticket_assignment: None,
             initial_submit: Vec::new(),
-            working_directory: None,
+            workdir_attachments: Vec::new(),
             control_operation_id: None,
         };
 
@@ -964,7 +964,7 @@ mod tests {
         assert_eq!(body["display_name"], "Coder one");
         assert_eq!(body["profile"], "builtin:coder");
         assert_eq!(body["initial_submit"], serde_json::json!([]));
-        assert_eq!(body["working_directory"], serde_json::Value::Null);
+        assert_eq!(body["workdir_attachments"], serde_json::json!([]));
     }
 
     #[test]
@@ -1014,29 +1014,35 @@ mod tests {
             "state": "idle",
             "implementation": {"kind": "worker", "display_hint": "Coder"},
             "capabilities": {"can_stop": true, "can_spawn_followup": false},
-            "working_directory": {
-                "working_directory_id": "wd-1",
-                "repository_key": "main",
-                "materializer_kind": "runtime_git_clone",
-                "status": "active",
-                "occupied_by": {
-                    "runtime_id": "arcadia",
-                    "worker_id": "worker-opaque-64",
-                    "display_name": "Coder",
-                    "linked_at": "2026-08-12T00:00:00Z"
+            "workdir_attachments": [{
+                "alias": "checkout",
+                "working_directory": {
+                    "working_directory_id": "wd-1",
+                    "repository_key": "main",
+                    "materializer_kind": "runtime_git_clone",
+                    "status": "active",
+                    "occupied_by": {
+                        "runtime_id": "arcadia",
+                        "worker_id": "worker-opaque-64",
+                        "display_name": "Coder",
+                        "linked_at": "2026-08-12T00:00:00Z"
+                    }
                 }
-            }
+            }]
         });
 
         let worker: BackendWorkerSummary = serde_json::from_value(payload.clone()).unwrap();
-        let workdir = worker.working_directory.unwrap();
+        let attachment = worker.workdir_attachments.into_iter().next().unwrap();
+        assert_eq!(attachment.alias, "checkout");
+        let workdir = attachment.working_directory;
         assert_eq!(workdir.repository_key, "main");
         let occupied_by = workdir.occupied_by.expect("occupied Workdir");
         assert_eq!(occupied_by.runtime_id, "arcadia");
         assert_eq!(occupied_by.worker_id, "worker-opaque-64");
 
         let mut stale = payload;
-        stale["working_directory"]["occupied_by"]["runtime_worker_id"] = serde_json::json!(64);
+        stale["workdir_attachments"][0]["working_directory"]["occupied_by"]["runtime_worker_id"] =
+            serde_json::json!(64);
         assert!(serde_json::from_value::<BackendWorkerSummary>(stale).is_err());
     }
 

crates/client/src/workspace_product.rs

@@ -312,7 +312,7 @@ impl BackendWorkspaceProductClient {
             initial_submit: vec![protocol::Segment::Text {
                 content: format!("Please handle intake for Ticket {ticket_id}."),
             }],
-            working_directory: None,
+            workdir_attachments: Vec::new(),
             control_operation_id: None,
         };
         let response: BrowserCreateWorkerResponse =

crates/protocol/src/subscription.rs

@@ -572,6 +572,41 @@ pub enum SubscriptionWorkerAvailability {
     Unavailable,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+pub struct SubscriptionWorkerWorkdirAttachment {
+    /// Stable Worker-local routing alias.
+    pub alias: String,
+    /// Runtime-internal Repository id. Workspace-facing TypeScript contracts
+    /// omit this field and require `repository_key` from the Server projection.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[cfg_attr(feature = "typescript", ts(skip))]
+    pub repository_id: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub repository_key: Option<String>,
+    pub working_directory_id: SubscriptionWorkdirId,
+}
+
+impl SubscriptionWorkerWorkdirAttachment {
+    pub fn validate(&self) -> Result<(), SubscriptionValidationError> {
+        validate_identifier(
+            "workdir_attachment_alias",
+            &self.alias,
+            MAX_RESOURCE_ID_BYTES,
+        )?;
+        self.working_directory_id.validate()?;
+        match (&self.repository_id, &self.repository_key) {
+            (Some(repository_id), None) => {
+                validate_identifier("repository_id", repository_id, MAX_RESOURCE_ID_BYTES)
+            }
+            (None, Some(repository_key)) => validate_repository_key(repository_key),
+            _ => Err(SubscriptionValidationError::InvalidIdentifier {
+                field: "repository_authority",
+            }),
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
 pub struct SubscriptionWorker {
@@ -604,15 +639,8 @@ pub struct SubscriptionWorker {
     pub display_name: Option<String>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub profile: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    #[cfg_attr(feature = "typescript", ts(skip))]
-    pub repository_id: Option<String>,
-    /// Workspace-facing Repository key. Runtime producers leave this unset and
-    /// Workspace Server projections replace `repository_id` with this field.
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub repository_key: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory_id: Option<SubscriptionWorkdirId>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachments: Vec<SubscriptionWorkerWorkdirAttachment>,
 }
 
 impl SubscriptionWorker {
@@ -624,19 +652,20 @@ impl SubscriptionWorker {
         if let Some(resource_key) = &self.resource_key {
             validate_identifier("resource_key", resource_key, MAX_RESOURCE_ID_BYTES)?;
         }
-        if let Some(repository_id) = &self.repository_id {
-            validate_identifier("repository_id", repository_id, MAX_RESOURCE_ID_BYTES)?;
-        }
-        if let Some(repository_key) = &self.repository_key {
-            validate_repository_key(repository_key)?;
-        }
-        if self.repository_id.is_some() && self.repository_key.is_some() {
-            return Err(SubscriptionValidationError::InvalidIdentifier {
-                field: "repository_authority",
-            });
-        }
-        if let Some(working_directory_id) = &self.working_directory_id {
-            working_directory_id.validate()?;
+        let mut aliases = HashSet::new();
+        let mut workdir_ids = HashSet::new();
+        for attachment in &self.workdir_attachments {
+            attachment.validate()?;
+            if !aliases.insert(attachment.alias.as_str()) {
+                return Err(SubscriptionValidationError::InvalidIdentifier {
+                    field: "workdir_attachment_alias",
+                });
+            }
+            if !workdir_ids.insert(attachment.working_directory_id.as_str()) {
+                return Err(SubscriptionValidationError::InvalidIdentifier {
+                    field: "working_directory_id",
+                });
+            }
         }
         Ok(())
     }
@@ -654,8 +683,6 @@ pub struct SubscriptionWorkdir {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub repository_key: Option<String>,
     pub state: String,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub primary_worker_id: Option<SubscriptionWorkerId>,
 }
 
 impl SubscriptionWorkdir {
@@ -673,9 +700,6 @@ impl SubscriptionWorkdir {
             }
         }
         validate_identifier("workdir_state", &self.state, MAX_RESOURCE_ID_BYTES)?;
-        if let Some(worker_id) = &self.primary_worker_id {
-            worker_id.validate()?;
-        }
         Ok(())
     }
 }
@@ -688,8 +712,6 @@ pub struct WorkspaceSubscriptionWorkdir {
     pub working_directory_id: SubscriptionWorkdirId,
     pub repository_key: String,
     pub state: String,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub primary_worker_id: Option<SubscriptionWorkerId>,
 }
 
 impl WorkspaceSubscriptionWorkdir {
@@ -697,9 +719,6 @@ impl WorkspaceSubscriptionWorkdir {
         self.working_directory_id.validate()?;
         validate_repository_key(&self.repository_key)?;
         validate_identifier("workdir_state", &self.state, MAX_RESOURCE_ID_BYTES)?;
-        if let Some(worker_id) = &self.primary_worker_id {
-            worker_id.validate()?;
-        }
         Ok(())
     }
 }
@@ -903,36 +922,58 @@ mod tests {
             workspace_id: Some("workspace-1".to_string()),
             display_name: Some(format!("Worker {value}")),
             profile: Some("builtin:coder".to_string()),
-            repository_id: None,
-            repository_key: None,
-            working_directory_id: None,
+            workdir_attachments: Vec::new(),
         }
     }
 
     #[test]
     fn runtime_and_workspace_repository_identity_projections_do_not_alias() {
         let mut runtime_worker = worker("worker-1");
-        runtime_worker.repository_id = Some("01890f47-3c22-7cc0-98c4-dc0c0c07398f".to_string());
+        runtime_worker
+            .workdir_attachments
+            .push(SubscriptionWorkerWorkdirAttachment {
+                alias: "checkout".to_string(),
+                repository_id: Some("01890f47-3c22-7cc0-98c4-dc0c0c07398f".to_string()),
+                repository_key: None,
+                working_directory_id: SubscriptionWorkdirId::new("workdir-1").unwrap(),
+            });
         runtime_worker.validate().unwrap();
         let runtime_json = serde_json::to_value(&runtime_worker).unwrap();
         assert_eq!(
-            runtime_json["repository_id"],
+            runtime_json["workdir_attachments"][0]["repository_id"],
             "01890f47-3c22-7cc0-98c4-dc0c0c07398f"
         );
-        assert!(runtime_json.get("repository_key").is_none());
+        assert!(
+            runtime_json["workdir_attachments"][0]
+                .get("repository_key")
+                .is_none()
+        );
 
         let mut workspace_worker = worker("worker-1");
-        workspace_worker.repository_key = Some("main".to_string());
+        workspace_worker
+            .workdir_attachments
+            .push(SubscriptionWorkerWorkdirAttachment {
+                alias: "checkout".to_string(),
+                repository_id: None,
+                repository_key: Some("main".to_string()),
+                working_directory_id: SubscriptionWorkdirId::new("workdir-1").unwrap(),
+            });
         workspace_worker.validate().unwrap();
         let workspace_json = serde_json::to_value(&workspace_worker).unwrap();
-        assert_eq!(workspace_json["repository_key"], "main");
-        assert!(workspace_json.get("repository_id").is_none());
+        assert_eq!(
+            workspace_json["workdir_attachments"][0]["repository_key"],
+            "main"
+        );
+        assert!(
+            workspace_json["workdir_attachments"][0]
+                .get("repository_id")
+                .is_none()
+        );
 
         let workspace_workdir = WorkspaceSubscriptionWorkdir {
             working_directory_id: SubscriptionWorkdirId::new("workdir-1").unwrap(),
             repository_key: "main".to_string(),
             state: "active".to_string(),
-            primary_worker_id: Some(worker_id("worker-1")),
         };
         workspace_workdir.validate().unwrap();
         let workdir_json = serde_json::to_value(&workspace_workdir).unwrap();

crates/protocol/src/typescript.rs

@@ -22,7 +22,8 @@ use crate::{
         SubscriptionRequestId, SubscriptionResponse, SubscriptionSnapshot,
         SubscriptionTerminationCode, SubscriptionWorkdirId, SubscriptionWorker,
         SubscriptionWorkerAvailability, SubscriptionWorkerId, SubscriptionWorkerIds,
-        SubscriptionWorkerProtocolMethod, SubscriptionWorkerState, WorkspaceSubscriptionWorkdir,
+        SubscriptionWorkerProtocolMethod, SubscriptionWorkerState,
+        SubscriptionWorkerWorkdirAttachment, WorkspaceSubscriptionWorkdir,
     },
 };
 
@@ -114,6 +115,7 @@ pub fn generated_protocol_types() -> String {
     push_decl::<SubscriptionWorkerState>(&cfg, &mut output);
     push_decl::<SubscriptionWorkerAvailability>(&cfg, &mut output);
     push_decl::<EventSubscriptionSelector>(&cfg, &mut output);
+    push_decl::<SubscriptionWorkerWorkdirAttachment>(&cfg, &mut output);
     push_decl::<SubscriptionWorker>(&cfg, &mut output);
     push_decl::<WorkspaceSubscriptionWorkdir>(&cfg, &mut output);
     push_decl::<SubscriptionSnapshot>(&cfg, &mut output);

crates/runtime-api/src/lib.rs

@@ -335,6 +335,8 @@ pub struct RepositoryMaterializationContext {
 #[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
 pub struct WorkingDirectoryRequest {
     pub repository: WorkingDirectoryRepository,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub display_name: Option<String>,
     #[serde(default)]
     pub materializer: MaterializerKind,
     #[serde(default, skip_serializing_if = "Option::is_none")]
@@ -344,12 +346,31 @@ pub struct WorkingDirectoryRequest {
 }
 
 #[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
-pub struct WorkingDirectoryClaim {
+pub struct WorkingDirectoryAttachmentClaim {
+    /// Stable Worker-local routing key. This is not a Workdir id or display name.
+    pub alias: workdir::WorkdirAttachmentAlias,
     pub working_directory_id: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub relative_cwd: Option<String>,
 }
 
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub struct WorkerWorkdirAttachmentsRequest {
+    pub workdir_attachments: Vec<WorkingDirectoryAttachmentClaim>,
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub struct WorkingDirectoryAttachmentRequest {
+    pub alias: workdir::WorkdirAttachmentAlias,
+    pub working_directory: WorkingDirectoryRequest,
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub struct WorkingDirectoryAttachmentStatus {
+    pub alias: workdir::WorkdirAttachmentAlias,
+    pub working_directory: WorkingDirectoryStatus,
+}
+
 #[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
 pub struct WorkingDirectoryStatus {
     pub summary: RuntimeWorkingDirectorySummary,
@@ -387,10 +408,10 @@ pub struct CreateWorkerRequest {
     pub config_bundle: Option<ConfigBundleRef>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub initial_input: Option<WorkerInput>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory_request: Option<WorkingDirectoryRequest>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory: Option<WorkingDirectoryClaim>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachment_requests: Vec<WorkingDirectoryAttachmentRequest>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachments: Vec<WorkingDirectoryAttachmentClaim>,
     #[serde(default, skip_serializing_if = "std::ops::Not::not")]
     pub worker_observation_enabled: bool,
     #[serde(default, skip_serializing_if = "Vec::is_empty")]
@@ -413,8 +434,8 @@ pub struct WorkerSummary {
     pub worker_state: Option<WorkerStateSnapshot>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub workspace_id: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory: Option<WorkingDirectoryStatus>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachments: Vec<WorkingDirectoryAttachmentStatus>,
     pub profile: ProfileSelector,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub display_name: Option<String>,
@@ -726,6 +747,17 @@ pub trait RuntimeApi {
         #[body] request: WorkerWorkspaceApiRequest,
     ) -> Result<WorkerResponse, RuntimeApiError>;
 
+    #[post(
+        "/v1/workers/{worker_id}/workdir-attachments",
+        status = 200,
+        error_status = 400
+    )]
+    async fn replace_worker_workdir_attachments(
+        &self,
+        #[path] worker_id: String,
+        #[body] request: WorkerWorkdirAttachmentsRequest,
+    ) -> Result<WorkerResponse, RuntimeApiError>;
+
     #[post(
         "/v1/workers/{worker_id}/completions",
         status = 200,
@@ -1002,6 +1034,13 @@ mod tests {
         ) -> Result<WorkerResponse, RuntimeApiError> {
             Err(test_error(501))
         }
+        async fn replace_worker_workdir_attachments(
+            &self,
+            _worker_id: String,
+            _request: WorkerWorkdirAttachmentsRequest,
+        ) -> Result<WorkerResponse, RuntimeApiError> {
+            Err(test_error(501))
+        }
         async fn complete_worker_arguments(
             &self,
             _worker_id: String,
@@ -1072,7 +1111,7 @@ mod tests {
     #[test]
     fn contract_inventory_is_complete_and_unique() {
         let operations = RuntimeApiMetadata::OPERATIONS;
-        assert_eq!(operations.len(), 15);
+        assert_eq!(operations.len(), 16);
         let mut routes = operations
             .iter()
             .map(|operation| (format!("{:?}", operation.method), operation.path))

crates/server-api/src/lib.rs

@@ -1583,6 +1583,9 @@ pub struct RuntimeWorkingDirectoryCleanupTarget {
 #[serde(deny_unknown_fields)]
 pub struct RuntimeWorkingDirectorySummary {
     pub working_directory_id: String,
+    /// Optional human-facing label, never a routing key.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub display_name: Option<String>,
     pub repository_id: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub creation_selector: Option<String>,
@@ -1606,8 +1609,6 @@ pub struct RuntimeWorkingDirectorySummary {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub cleanliness: Option<String>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub primary_worker_id: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
     pub occupied_by: Option<WorkingDirectoryOccupancy>,
 }
 
@@ -1618,6 +1619,9 @@ pub struct RuntimeWorkingDirectorySummary {
 #[serde(deny_unknown_fields)]
 pub struct WorkingDirectorySummary {
     pub working_directory_id: String,
+    /// Optional human-facing label, never a routing key.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub display_name: Option<String>,
     pub repository_key: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub creation_selector: Option<String>,
@@ -1641,8 +1645,6 @@ pub struct WorkingDirectorySummary {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub cleanliness: Option<String>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub primary_worker_id: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
     pub occupied_by: Option<WorkingDirectoryOccupancy>,
 }
 
@@ -1713,6 +1715,7 @@ impl From<workdir::workspace::RuntimeWorkingDirectorySummary> for RuntimeWorking
     fn from(value: workdir::workspace::RuntimeWorkingDirectorySummary) -> Self {
         Self {
             working_directory_id: value.working_directory_id,
+            display_name: value.display_name,
             repository_id: value.repository_id,
             creation_selector: value.creation_selector,
             creation_ref: value.creation_ref,
@@ -1725,7 +1728,6 @@ impl From<workdir::workspace::RuntimeWorkingDirectorySummary> for RuntimeWorking
             cleanup_target: value.cleanup_target.map(Into::into),
             status: value.status.into(),
             cleanliness: value.cleanliness,
-            primary_worker_id: value.primary_worker_id,
             occupied_by: value.occupied_by.map(Into::into),
         }
     }
@@ -1735,6 +1737,7 @@ impl From<workdir::workspace::WorkingDirectorySummary> for WorkingDirectorySumma
     fn from(value: workdir::workspace::WorkingDirectorySummary) -> Self {
         Self {
             working_directory_id: value.working_directory_id,
+            display_name: value.display_name,
             repository_key: value.repository_key,
             creation_selector: value.creation_selector,
             creation_ref: value.creation_ref,
@@ -1747,7 +1750,6 @@ impl From<workdir::workspace::WorkingDirectorySummary> for WorkingDirectorySumma
             cleanup_target: value.cleanup_target.map(Into::into),
             status: value.status.into(),
             cleanliness: value.cleanliness,
-            primary_worker_id: value.primary_worker_id,
             occupied_by: value.occupied_by.map(Into::into),
         }
     }
@@ -1765,6 +1767,9 @@ impl From<workdir::workspace::WorkingDirectorySummary> for WorkingDirectorySumma
 pub struct WorkingDirectoryCreateRequest {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub runtime_id: Option<String>,
+    /// Optional human-facing label, independent of every Worker attachment alias.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub display_name: Option<String>,
     pub repository_key: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub selector: Option<String>,
@@ -2445,6 +2450,24 @@ pub struct WorkspaceWorkerDiscoveryPage {
     pub next_cursor: Option<String>,
 }
 
+/// One Workspace Worker Workdir attachment. `alias` is the stable Worker-local
+/// routing key; the nested Workdir id and display name are inventory metadata.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+#[serde(deny_unknown_fields)]
+pub struct WorkerWorkdirAttachmentSummary {
+    pub alias: String,
+    pub working_directory: WorkingDirectorySummary,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+#[serde(deny_unknown_fields)]
+pub struct RuntimeWorkerWorkdirAttachmentSummary {
+    pub alias: String,
+    pub working_directory: RuntimeWorkingDirectorySummary,
+}
+
 /// Workspace-authoritative Worker projection.
 ///
 /// `resource_key` is required here even though Runtime-internal Worker summaries
@@ -2478,8 +2501,8 @@ pub struct WorkerSummary {
     pub retention_state: String,
     pub implementation: WorkerImplementationSummary,
     pub capabilities: WorkerCapabilitySummary,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory: Option<WorkingDirectorySummary>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachments: Vec<WorkerWorkdirAttachmentSummary>,
     #[serde(default)]
     pub diagnostics: Vec<Diagnostic>,
 }
@@ -2507,9 +2530,8 @@ pub struct WorkerLaunchWorkerSummary {
     pub retention_state: String,
     pub implementation: WorkerImplementationSummary,
     pub capabilities: WorkerCapabilitySummary,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    #[cfg_attr(feature = "typescript", ts(optional = nullable))]
-    pub working_directory: Option<RuntimeWorkingDirectorySummary>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachments: Vec<RuntimeWorkerWorkdirAttachmentSummary>,
     #[serde(default)]
     pub diagnostics: Vec<Diagnostic>,
 }
@@ -2563,6 +2585,8 @@ pub struct WorkingDirectoryRepositoryOption {
 #[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
 #[serde(deny_unknown_fields)]
 pub struct BrowserWorkerWorkingDirectorySelection {
+    /// Stable Worker-local routing alias.
+    pub alias: String,
     pub working_directory_id: String,
     #[serde(default)]
     pub relative_cwd: Option<String>,
@@ -2589,7 +2613,7 @@ pub struct CreateWorkspaceWorkerRequest {
     #[serde(default)]
     pub initial_submit: Vec<protocol::Segment>,
     #[serde(default)]
-    pub working_directory: Option<BrowserWorkerWorkingDirectorySelection>,
+    pub workdir_attachments: Vec<BrowserWorkerWorkingDirectorySelection>,
     /// Backend idempotency key used only for authenticated Worker-owned spawn/control.
     #[serde(default)]
     pub control_operation_id: Option<String>,
@@ -3663,6 +3687,7 @@ pub fn worker_launch_api_typescript() -> String {
         WorkerWorkspaceSummary::decl(&config),
         WorkerImplementationSummary::decl(&config),
         WorkerCapabilitySummary::decl(&config),
+        RuntimeWorkerWorkdirAttachmentSummary::decl(&config),
         WorkerLaunchWorkerSummary::decl(&config),
         WorkerLaunchRuntimeOption::decl(&config),
         WorkerLaunchProfileCandidate::decl(&config),
@@ -4100,7 +4125,7 @@ mod tests {
                 can_stop: true,
                 can_spawn_followup: false,
             },
-            working_directory: None,
+            workdir_attachments: Vec::new(),
             diagnostics: Vec::new(),
         }
     }
@@ -4178,7 +4203,7 @@ mod tests {
             profile: None,
             ticket_assignment: None,
             initial_submit: Vec::new(),
-            working_directory: None,
+            workdir_attachments: Vec::new(),
             control_operation_id: None,
         })
         .unwrap();
@@ -4190,7 +4215,7 @@ mod tests {
                 "profile": null,
                 "ticket_assignment": null,
                 "initial_submit": [],
-                "working_directory": null,
+                "workdir_attachments": [],
                 "control_operation_id": null,
             })
         );
@@ -5097,6 +5122,7 @@ mod tests {
     fn workdir_summary_omits_absent_optional_fields_on_the_wire() {
         let value = serde_json::to_value(WorkingDirectorySummary {
             working_directory_id: "workdir-1".into(),
+            display_name: None,
             repository_key: "main".into(),
             creation_selector: None,
             creation_ref: None,
@@ -5109,7 +5135,6 @@ mod tests {
             cleanup_target: None,
             status: WorkingDirectoryStatusKind::Active,
             cleanliness: None,
-            primary_worker_id: None,
             occupied_by: None,
         })
         .expect("serialize Workdir summary");
@@ -5125,7 +5150,6 @@ mod tests {
             "observed_at_epoch_seconds",
             "cleanup_target",
             "cleanliness",
-            "primary_worker_id",
             "occupied_by",
         ] {
             assert!(

crates/tools/src/bash.rs

@@ -6,7 +6,9 @@ use agen::tool::{Tool, ToolDefinition, ToolError, ToolMeta, ToolOutput};
 use async_trait::async_trait;
 use schemars::JsonSchema;
 use serde::Deserialize;
-use workdir::{CommandHandle, CommandOutputRequest, CommandRequest, WorkdirSessionHandle};
+use workdir::{
+    CommandHandle, CommandOutputRequest, CommandRequest, WorkdirSessionHandle, WorkdirSessionRouter,
+};
 
 const DEFAULT_TIMEOUT_SECS: u64 = 120;
 const MAX_TIMEOUT_SECS: u64 = 600;
@@ -14,13 +16,16 @@ const INLINE_BYTE_BUDGET: usize = 12 * 1024;
 
 #[derive(Debug, Deserialize, JsonSchema)]
 struct BashParams {
+    /// Worker-local alias of the Workdir attachment to use.
+    #[serde(default)]
+    target_workdir: Option<String>,
     command: String,
     #[serde(default)]
     timeout: Option<u64>,
 }
 
 pub(crate) struct BashTool {
-    session: WorkdirSessionHandle,
+    router: Arc<WorkdirSessionRouter>,
     output_dir: PathBuf,
     state: Arc<Mutex<BashExecutionState>>,
 }
@@ -29,6 +34,7 @@ pub(crate) struct BashTool {
 struct ActiveCommand {
     call_id: String,
     execution_nonce: u64,
+    session: WorkdirSessionHandle,
     handle: CommandHandle,
 }
 
@@ -93,6 +99,12 @@ impl Tool for BashTool {
     ) -> Result<ToolOutput, ToolError> {
         let params: BashParams = serde_json::from_str(input_json)
             .map_err(|error| ToolError::InvalidArgument(format!("invalid Bash input: {error}")))?;
+        let selected = crate::routing::resolve_session(
+            &self.router,
+            params.target_workdir.as_deref(),
+            workdir::WorkdirSessionCapability::Command,
+        )?;
+        let session = selected.session;
         let timeout_secs = params
             .timeout
             .unwrap_or(DEFAULT_TIMEOUT_SECS)
@@ -106,14 +118,13 @@ impl Tool for BashTool {
             state.next_execution_nonce
         };
         let mut guard = CommandGuard {
-            session: self.session.clone(),
+            session: session.clone(),
             state: self.state.clone(),
             execution_id: execution_id.clone(),
             execution_nonce,
             handle: None,
         };
-        let handle = self
-            .session
+        let handle = session
             .start_command(CommandRequest {
                 command: params.command,
                 timeout_secs,
@@ -131,6 +142,7 @@ impl Tool for BashTool {
                 ActiveCommand {
                     call_id: call_id.clone(),
                     execution_nonce,
+                    session: session.clone(),
                     handle: handle.clone(),
                 },
             );
@@ -139,13 +151,12 @@ impl Tool for BashTool {
         };
         guard.handle = Some(handle.clone());
         if cancel_after_start {
-            self.session
+            session
                 .cancel_command(handle.clone())
                 .await
                 .map_err(crate::ToolsError::from)?;
         }
-        let output = self
-            .session
+        let output = session
             .command_output(CommandOutputRequest {
                 handle,
                 cursor: 0,
@@ -222,12 +233,13 @@ impl Tool for BashTool {
                 .active
                 .values()
                 .filter(|active| active.call_id == call_id)
-                .map(|active| active.handle.clone())
+                .cloned()
                 .collect::<Vec<_>>()
         };
-        for handle in handles {
-            self.session
-                .cancel_command(handle)
+        for active in handles {
+            active
+                .session
+                .cancel_command(active.handle)
                 .await
                 .map_err(crate::ToolsError::from)?;
         }
@@ -242,14 +254,12 @@ impl Tool for BashTool {
         let handle = {
             let mut state = self.state.lock().unwrap();
             state.cancellation_requested.insert(execution_id.clone());
-            state
-                .active
-                .get(&execution_id)
-                .map(|active| active.handle.clone())
+            state.active.get(&execution_id).cloned()
         };
-        if let Some(handle) = handle {
-            self.session
-                .cancel_command(handle)
+        if let Some(active) = handle {
+            active
+                .session
+                .cancel_command(active.handle)
                 .await
                 .map_err(crate::ToolsError::from)?;
         }
@@ -268,13 +278,20 @@ fn truncate_for_summary(command: &str) -> String {
 }
 
 pub fn bash_tool(session: WorkdirSessionHandle, output_dir: PathBuf) -> ToolDefinition {
+    routed_bash_tool(crate::routing::singleton_router(session), output_dir)
+}
+
+pub(crate) fn routed_bash_tool(
+    router: Arc<WorkdirSessionRouter>,
+    output_dir: PathBuf,
+) -> ToolDefinition {
     Arc::new(move || {
         let schema = schemars::schema_for!(BashParams);
         let meta = ToolMeta::new("Bash")
-            .description("Execute a shell command in the bound Workdir. Process start, bounded inline output, full-output spill, timeout and cancellation are owned by the WorkdirSession provider. This is not a sandbox.")
+            .description("Execute a shell command in one selected Workdir. Process start, bounded inline output, full-output spill, timeout and cancellation are owned by that WorkdirSession provider. This is not a sandbox.")
             .input_schema(serde_json::to_value(schema).expect("Bash schema serialization"));
         let tool: Arc<dyn Tool> = Arc::new(BashTool {
-            session: session.clone(),
+            router: router.clone(),
             output_dir: output_dir.clone(),
             state: Arc::new(Mutex::new(BashExecutionState::default())),
         });

crates/tools/src/edit.rs

@@ -9,15 +9,18 @@ use serde::Deserialize;
 
 use crate::error::ToolsError;
 use crate::tracker::Tracker;
-use workdir::{EditRequest, WorkdirPath, WorkdirSessionHandle};
+use workdir::{EditRequest, WorkdirPath, WorkdirSessionHandle, WorkdirSessionRouter};
 
-const DESCRIPTION: &str = "Replace a substring in an existing file. By default \
+const DESCRIPTION: &str = "Replace a substring in an existing file in the selected Workdir attachment. By default \
 `old_string` must be unique in the file; set `replace_all: true` to replace \
-every occurrence. The file must have been read first (via the Read tool) in \
-this session. Paths are relative to the bound Workdir.";
+every occurrence. The file must have been read first through the same attachment. \
+When exactly one Workdir is attached, target_workdir may be omitted.";
 
 #[derive(Debug, Deserialize, schemars::JsonSchema)]
 pub(crate) struct EditParams {
+    /// Worker-local alias of the Workdir attachment to use.
+    #[serde(default)]
+    pub target_workdir: Option<String>,
     /// Logical path relative to the bound Workdir root.
     pub file_path: String,
     /// String to replace. Must be unique in the file unless `replace_all` is true.
@@ -30,7 +33,7 @@ pub(crate) struct EditParams {
 }
 
 pub(crate) struct EditTool {
-    session: WorkdirSessionHandle,
+    router: Arc<WorkdirSessionRouter>,
     tracker: Tracker,
 }
 
@@ -44,6 +47,14 @@ impl Tool for EditTool {
         let params: EditParams = serde_json::from_str(input_json)
             .map_err(|e| ToolError::InvalidArgument(format!("invalid Edit input: {e}")))?;
 
+        let selected = crate::routing::resolve_session(
+            &self.router,
+            params.target_workdir.as_deref(),
+            workdir::WorkdirSessionCapability::Edit,
+        )?;
+        let tracker = self
+            .tracker
+            .scoped_attachment(&selected.alias, selected.generation);
         let path = WorkdirPath::new(&params.file_path).map_err(ToolsError::from)?;
         tracing::debug!(path = %path, replace_all = params.replace_all, "Edit");
 
@@ -59,9 +70,9 @@ impl Tool for EditTool {
         }
 
         let mutation_key = PathBuf::from(path.as_str());
-        let _mutation_permit = self.tracker.acquire_mutation(&mutation_key, &ctx).await;
-        let expected_hash = self.tracker.expected_workdir_hash(&path)?;
-        let result = self
+        let _mutation_permit = tracker.acquire_mutation(&mutation_key, &ctx).await;
+        let expected_hash = tracker.expected_workdir_hash(&path)?;
+        let result = selected
             .session
             .edit(EditRequest {
                 path: path.clone(),
@@ -73,7 +84,7 @@ impl Tool for EditTool {
             .await
             .map_err(ToolsError::from)?;
         let replacements = result.replacements;
-        self.tracker.record_workdir_edit(
+        tracker.record_workdir_edit(
             &path,
             result.content_hash,
             replacements,
@@ -122,8 +133,15 @@ fn make_preview(text: &str, needle: &str) -> String {
     out
 }
 
-/// Factory for the `Edit` tool.
+/// Factory for the `Edit` tool bound to one compatibility session.
 pub fn edit_tool(session: WorkdirSessionHandle, tracker: Tracker) -> ToolDefinition {
+    routed_edit_tool(crate::routing::singleton_router(session), tracker)
+}
+
+pub(crate) fn routed_edit_tool(
+    router: Arc<WorkdirSessionRouter>,
+    tracker: Tracker,
+) -> ToolDefinition {
     Arc::new(move || {
         let schema = schemars::schema_for!(EditParams);
         let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
@@ -131,7 +149,7 @@ pub fn edit_tool(session: WorkdirSessionHandle, tracker: Tracker) -> ToolDefinit
             .description(DESCRIPTION)
             .input_schema(schema_value);
         let tool: Arc<dyn Tool> = Arc::new(EditTool {
-            session: session.clone(),
+            router: router.clone(),
             tracker: tracker.clone(),
         });
         (meta, tool)

crates/tools/src/glob.rs

@@ -4,7 +4,7 @@ use agen::tool::{Tool, ToolDefinition, ToolError, ToolMeta, ToolOutput};
 use async_trait::async_trait;
 use schemars::JsonSchema;
 use serde::Deserialize;
-use workdir::{GlobRequest, WorkdirPath, WorkdirSessionHandle};
+use workdir::{GlobRequest, WorkdirPath, WorkdirSessionHandle, WorkdirSessionRouter};
 
 use crate::ToolsError;
 
@@ -12,6 +12,9 @@ const RESULT_LIMIT: usize = 1000;
 
 #[derive(Debug, Deserialize, JsonSchema)]
 struct GlobParams {
+    /// Worker-local alias of the Workdir attachment to use.
+    #[serde(default)]
+    target_workdir: Option<String>,
     /// Glob pattern, for example `**/*.rs` or `src/**/test_*.py`.
     pattern: String,
     /// Logical Workdir-relative directory. Defaults to the Workdir root.
@@ -20,7 +23,7 @@ struct GlobParams {
 }
 
 struct GlobTool {
-    session: WorkdirSessionHandle,
+    router: Arc<WorkdirSessionRouter>,
 }
 
 #[async_trait]
@@ -32,13 +35,18 @@ impl Tool for GlobTool {
     ) -> Result<ToolOutput, ToolError> {
         let params: GlobParams = serde_json::from_str(input_json)
             .map_err(|error| ToolError::InvalidArgument(format!("invalid Glob input: {error}")))?;
+        let selected = crate::routing::resolve_session(
+            &self.router,
+            params.target_workdir.as_deref(),
+            workdir::WorkdirSessionCapability::Glob,
+        )?;
         let path = match params.path {
             Some(path) => WorkdirPath::new(&path).map_err(ToolsError::from)?,
             None => WorkdirPath::root(),
         };
         let pattern = params.pattern;
         tracing::debug!(%pattern, %path, "Glob");
-        let result = self
+        let result = selected
             .session
             .glob(GlobRequest {
                 pattern: pattern.clone(),
@@ -75,13 +83,17 @@ impl Tool for GlobTool {
 }
 
 pub fn glob_tool(session: WorkdirSessionHandle) -> ToolDefinition {
+    routed_glob_tool(crate::routing::singleton_router(session))
+}
+
+pub(crate) fn routed_glob_tool(router: Arc<WorkdirSessionRouter>) -> ToolDefinition {
     Arc::new(move || {
         let schema = schemars::schema_for!(GlobParams);
         let meta = ToolMeta::new("Glob")
-            .description("Find files matching a glob pattern inside the bound Workdir. Results are sorted and capped at 1000 entries. Paths are Workdir-relative.")
+            .description("Find files matching a glob pattern inside the selected Workdir. Results are sorted and capped at 1000 entries. Paths are Workdir-relative.")
             .input_schema(serde_json::to_value(schema).expect("Glob schema serialization"));
         let tool: Arc<dyn Tool> = Arc::new(GlobTool {
-            session: session.clone(),
+            router: router.clone(),
         });
         (meta, tool)
     })

crates/tools/src/grep.rs

@@ -4,7 +4,9 @@ use agen::tool::{Tool, ToolDefinition, ToolError, ToolMeta, ToolOutput};
 use async_trait::async_trait;
 use schemars::JsonSchema;
 use serde::Deserialize;
-use workdir::{GrepOutputMode, GrepRequest, WorkdirPath, WorkdirSessionHandle};
+use workdir::{
+    GrepOutputMode, GrepRequest, WorkdirPath, WorkdirSessionHandle, WorkdirSessionRouter,
+};
 
 use crate::ToolsError;
 
@@ -21,6 +23,9 @@ enum OutputMode {
 
 #[derive(Debug, Deserialize, JsonSchema)]
 struct GrepParams {
+    /// Worker-local alias of the Workdir attachment to use.
+    #[serde(default)]
+    target_workdir: Option<String>,
     pattern: String,
     /// Workdir-relative path, or an absolute path covered by readable scope. Defaults to the Workdir root.
     #[serde(default)]
@@ -48,7 +53,7 @@ struct GrepParams {
 }
 
 struct GrepTool {
-    session: WorkdirSessionHandle,
+    router: Arc<WorkdirSessionRouter>,
 }
 
 #[async_trait]
@@ -60,6 +65,11 @@ impl Tool for GrepTool {
     ) -> Result<ToolOutput, ToolError> {
         let params: GrepParams = serde_json::from_str(input_json)
             .map_err(|error| ToolError::InvalidArgument(format!("invalid Grep input: {error}")))?;
+        let selected = crate::routing::resolve_session(
+            &self.router,
+            params.target_workdir.as_deref(),
+            workdir::WorkdirSessionCapability::Grep,
+        )?;
         let path = match params.path {
             Some(path) => WorkdirPath::new_scoped(&path).map_err(ToolsError::from)?,
             None => WorkdirPath::root(),
@@ -74,7 +84,7 @@ impl Tool for GrepTool {
             .map(|context| (context, context))
             .unwrap_or((params.before.unwrap_or(0), params.after.unwrap_or(0)));
         let head_limit = params.head_limit.unwrap_or(DEFAULT_HEAD_LIMIT);
-        let result = self
+        let result = selected
             .session
             .grep(GrepRequest {
                 pattern: params.pattern,
@@ -126,13 +136,17 @@ impl Tool for GrepTool {
 }
 
 pub fn grep_tool(session: WorkdirSessionHandle) -> ToolDefinition {
+    routed_grep_tool(crate::routing::singleton_router(session))
+}
+
+pub(crate) fn routed_grep_tool(router: Arc<WorkdirSessionRouter>) -> ToolDefinition {
     Arc::new(move || {
         let schema = schemars::schema_for!(GrepParams);
         let meta = ToolMeta::new("Grep")
-            .description("Search a Workdir file or directory with a regex. Content results group lines by file; `>` marks matching lines and unmarked lines are context. Directory traversal executes inside the WorkdirSession provider. Results are bounded and Workdir-relative.")
+            .description("Search a file or directory in the selected Workdir with a regex. Content results group lines by file; `>` marks matching lines and unmarked lines are context. Directory traversal executes inside the WorkdirSession provider. Results are bounded and Workdir-relative.")
             .input_schema(serde_json::to_value(schema).expect("Grep schema serialization"));
         let tool: Arc<dyn Tool> = Arc::new(GrepTool {
-            session: session.clone(),
+            router: router.clone(),
         });
         (meta, tool)
     })

crates/tools/src/lib.rs

@@ -17,6 +17,7 @@ mod edit;
 mod glob;
 mod grep;
 mod read;
+mod routing;
 mod view_image;
 mod web;
 mod write;
@@ -28,11 +29,11 @@ pub use glob::glob_tool;
 pub use grep::grep_tool;
 pub use read::read_tool;
 pub use tracker::{ChangeStat, Tracker};
-pub use view_image::view_image_tool;
+pub use view_image::{routed_view_image_tool, view_image_tool};
 pub use web::{web_fetch_tool, web_search_tool};
 pub use write::write_tool;
 
-/// Build the local filesystem/command tool surface implemented by a WorkdirSession.
+/// Build the filesystem/command tool surface for a single Workdir session.
 /// Profile/manifest policy may narrow this set further in the Engine.
 pub fn core_builtin_tools(
     session: workdir::WorkdirSessionHandle,
@@ -42,24 +43,75 @@ pub fn core_builtin_tools(
     use workdir::WorkdirSessionCapability;
 
     let capabilities = session.capabilities();
+    let router = routing::singleton_router(session);
     let mut tools = Vec::with_capacity(6);
     if capabilities.supports(WorkdirSessionCapability::Read) {
-        tools.push(read_tool(session.clone(), tracker.clone()));
+        tools.push(read::routed_read_tool(router.clone(), tracker.clone()));
     }
     if capabilities.supports(WorkdirSessionCapability::Write) {
-        tools.push(write_tool(session.clone(), tracker.clone()));
+        tools.push(write::routed_write_tool(router.clone(), tracker.clone()));
     }
     if capabilities.supports(WorkdirSessionCapability::Edit) {
-        tools.push(edit_tool(session.clone(), tracker));
+        tools.push(edit::routed_edit_tool(router.clone(), tracker));
     }
     if capabilities.supports(WorkdirSessionCapability::Glob) {
-        tools.push(glob_tool(session.clone()));
+        tools.push(glob::routed_glob_tool(router.clone()));
     }
     if capabilities.supports(WorkdirSessionCapability::Grep) {
-        tools.push(grep_tool(session.clone()));
+        tools.push(grep::routed_grep_tool(router.clone()));
     }
     if capabilities.supports(WorkdirSessionCapability::Command) {
-        tools.push(bash_tool(session, bash_output_dir));
+        tools.push(bash::routed_bash_tool(router, bash_output_dir));
+    }
+    tools
+}
+
+/// Build the stable routed tool surface for a Worker's live attachment set.
+///
+/// The definitions remain installed while the set is empty or changes at runtime;
+/// each invocation resolves `target_workdir` against the router and then lets the
+/// selected provider enforce its capabilities.
+pub fn routed_builtin_tools(
+    router: std::sync::Arc<workdir::WorkdirSessionRouter>,
+    tracker: Tracker,
+    bash_output_dir: std::path::PathBuf,
+) -> Vec<agen::tool::ToolDefinition> {
+    vec![
+        read::routed_read_tool(router.clone(), tracker.clone()),
+        write::routed_write_tool(router.clone(), tracker.clone()),
+        edit::routed_edit_tool(router.clone(), tracker),
+        glob::routed_glob_tool(router.clone()),
+        grep::routed_grep_tool(router.clone()),
+        bash::routed_bash_tool(router, bash_output_dir),
+    ]
+}
+
+pub fn routed_builtin_tools_for_current_capabilities(
+    router: std::sync::Arc<workdir::WorkdirSessionRouter>,
+    tracker: Tracker,
+    bash_output_dir: std::path::PathBuf,
+) -> Vec<agen::tool::ToolDefinition> {
+    use workdir::WorkdirSessionCapability;
+
+    let capabilities = router.capabilities();
+    let mut tools = Vec::with_capacity(6);
+    if capabilities.supports(WorkdirSessionCapability::Read) {
+        tools.push(read::routed_read_tool(router.clone(), tracker.clone()));
+    }
+    if capabilities.supports(WorkdirSessionCapability::Write) {
+        tools.push(write::routed_write_tool(router.clone(), tracker.clone()));
+    }
+    if capabilities.supports(WorkdirSessionCapability::Edit) {
+        tools.push(edit::routed_edit_tool(router.clone(), tracker));
+    }
+    if capabilities.supports(WorkdirSessionCapability::Glob) {
+        tools.push(glob::routed_glob_tool(router.clone()));
+    }
+    if capabilities.supports(WorkdirSessionCapability::Grep) {
+        tools.push(grep::routed_grep_tool(router.clone()));
+    }
+    if capabilities.supports(WorkdirSessionCapability::Command) {
+        tools.push(bash::routed_bash_tool(router, bash_output_dir));
     }
     tools
 }
@@ -75,6 +127,29 @@ pub fn read_only_builtin_tools(
     core_builtin_tools(session, Tracker::new(), std::path::PathBuf::new())
 }
 
+pub fn read_only_routed_builtin_tools(
+    source: std::sync::Arc<workdir::WorkdirSessionRouter>,
+) -> Vec<agen::tool::ToolDefinition> {
+    let router = std::sync::Arc::new(workdir::WorkdirSessionRouter::new());
+    for alias in source.aliases() {
+        let Ok(selected) = source.resolve(Some(alias.as_str())) else {
+            continue;
+        };
+        router
+            .attach(
+                alias,
+                std::sync::Arc::new(workdir::ReadOnlyWorkdirSession::new(selected.session)),
+            )
+            .expect("read-only projection preserves unique aliases");
+    }
+    let tracker = Tracker::new();
+    vec![
+        read::routed_read_tool(router.clone(), tracker),
+        glob::routed_glob_tool(router.clone()),
+        grep::routed_grep_tool(router),
+    ]
+}
+
 pub fn web_builtin_tools(
     web_config: Option<manifest::WebConfig>,
 ) -> Vec<agen::tool::ToolDefinition> {

crates/tools/src/read.rs

@@ -8,18 +8,22 @@ use serde::Deserialize;
 
 use crate::error::ToolsError;
 use crate::tracker::Tracker;
-use workdir::{ReadRequest, WorkdirPath, WorkdirSessionHandle};
+use workdir::{ReadRequest, WorkdirPath, WorkdirSessionHandle, WorkdirSessionRouter};
 
-const DESCRIPTION: &str = "Read a text file from the local filesystem. \
+const DESCRIPTION: &str = "Read a text file from a Workdir attachment selected by its Worker-local alias. \
 Supports offset/limit for large files. Returns line-numbered output (1-based). \
 Directories cannot be read. The file must be read before Write or Edit can \
-modify it. Paths are Workdir-relative unless an absolute path is explicitly readable.";
+modify it. Paths are Workdir-relative unless an absolute path is explicitly readable. \
+When exactly one Workdir is attached, target_workdir may be omitted.";
 
 const DEFAULT_LIMIT: usize = 2000;
 const PROVIDER_BYTE_LIMIT: usize = 256 * 1024;
 
 #[derive(Debug, Deserialize, schemars::JsonSchema)]
 pub(crate) struct ReadParams {
+    /// Worker-local alias of the Workdir attachment to use.
+    #[serde(default)]
+    pub target_workdir: Option<String>,
     /// Workdir-relative path, or an absolute path covered by readable scope.
     pub file_path: String,
     /// 0-based line offset from the start. Defaults to 0.
@@ -31,7 +35,7 @@ pub(crate) struct ReadParams {
 }
 
 pub(crate) struct ReadTool {
-    session: WorkdirSessionHandle,
+    router: Arc<WorkdirSessionRouter>,
     tracker: Tracker,
 }
 
@@ -44,13 +48,21 @@ impl Tool for ReadTool {
     ) -> Result<ToolOutput, ToolError> {
         let params: ReadParams = serde_json::from_str(input_json)
             .map_err(|e| ToolError::InvalidArgument(format!("invalid Read input: {e}")))?;
+        let selected = crate::routing::resolve_session(
+            &self.router,
+            params.target_workdir.as_deref(),
+            workdir::WorkdirSessionCapability::Read,
+        )?;
+        let tracker = self
+            .tracker
+            .scoped_attachment(&selected.alias, selected.generation);
         let offset = params.offset.unwrap_or(0);
         let limit = params.limit.unwrap_or(DEFAULT_LIMIT).max(1);
 
         let path = WorkdirPath::new_scoped(&params.file_path).map_err(ToolsError::from)?;
         tracing::debug!(path = %path, offset, limit, "Read");
 
-        let result = self
+        let result = selected
             .session
             .read(ReadRequest {
                 path: path.clone(),
@@ -60,7 +72,7 @@ impl Tool for ReadTool {
             })
             .await
             .map_err(ToolsError::from)?;
-        self.tracker.record_workdir_hash(&path, result.content_hash);
+        tracker.record_workdir_hash(&path, result.content_hash);
 
         let text = String::from_utf8_lossy(&result.bytes).into_owned();
         let rendered = render_provider_read(
@@ -144,8 +156,15 @@ fn render_numbered(text: &str, offset: usize, limit: usize) -> Rendered {
     }
 }
 
-/// Factory for the `Read` tool.
+/// Factory for the `Read` tool bound to one compatibility session.
 pub fn read_tool(session: WorkdirSessionHandle, tracker: Tracker) -> ToolDefinition {
+    routed_read_tool(crate::routing::singleton_router(session), tracker)
+}
+
+pub(crate) fn routed_read_tool(
+    router: Arc<WorkdirSessionRouter>,
+    tracker: Tracker,
+) -> ToolDefinition {
     Arc::new(move || {
         let schema = schemars::schema_for!(ReadParams);
         let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
@@ -153,7 +172,7 @@ pub fn read_tool(session: WorkdirSessionHandle, tracker: Tracker) -> ToolDefinit
             .description(DESCRIPTION)
             .input_schema(schema_value);
         let tool: Arc<dyn Tool> = Arc::new(ReadTool {
-            session: session.clone(),
+            router: router.clone(),
             tracker: tracker.clone(),
         });
         (meta, tool)
@@ -199,6 +218,7 @@ mod tests {
         // History recorded
         assert!(
             tracker
+                .scoped_attachment(&workdir::WorkdirAttachmentAlias::new("workdir").unwrap(), 0,)
                 .expected_workdir_hash(&WorkdirPath::new("a.txt").unwrap())
                 .is_ok()
         );
@@ -229,7 +249,7 @@ mod tests {
 
     #[tokio::test]
     async fn read_tool_missing_file() {
-        let (dir, fs, tracker) = setup();
+        let (_dir, fs, tracker) = setup();
         let def = read_tool(fs, tracker);
         let (_, tool) = def();
         let input = serde_json::json!({

crates/tools/src/routing.rs

@@ -0,0 +1,32 @@
+use std::sync::Arc;
+
+use agen::tool::ToolError;
+use workdir::{
+    ResolvedWorkdirSession, WorkdirAttachmentAlias, WorkdirSessionCapability, WorkdirSessionHandle,
+    WorkdirSessionRouter,
+};
+
+pub(crate) fn singleton_router(session: WorkdirSessionHandle) -> Arc<WorkdirSessionRouter> {
+    let router = Arc::new(WorkdirSessionRouter::new());
+    router
+        .attach(
+            WorkdirAttachmentAlias::new("workdir").expect("static attachment alias is valid"),
+            session,
+        )
+        .expect("fresh singleton router accepts its session");
+    router
+}
+
+pub(crate) fn resolve_session(
+    router: &WorkdirSessionRouter,
+    target_workdir: Option<&str>,
+    required: WorkdirSessionCapability,
+) -> Result<ResolvedWorkdirSession, ToolError> {
+    let selected = router
+        .resolve(target_workdir)
+        .map_err(|error| ToolError::InvalidArgument(error.to_string()))?;
+    if !selected.session.capabilities().supports(required) {
+        return Err(crate::ToolsError::from(workdir::WorkdirError::Unsupported(required)).into());
+    }
+    Ok(selected)
+}

crates/tools/src/tracker.rs

@@ -65,9 +65,15 @@ fn hash_bytes(bytes: &[u8]) -> ContentHash {
     hasher.finalize().into()
 }
 
+#[derive(Clone, Debug, Eq, Hash, PartialEq)]
+struct TrackedPath {
+    namespace: Option<Arc<str>>,
+    path: PathBuf,
+}
+
 #[derive(Debug, Clone, Default)]
 struct FileMutationCoordinator {
-    locks: Arc<tokio::sync::Mutex<HashMap<PathBuf, Arc<tokio::sync::Mutex<()>>>>>,
+    locks: Arc<tokio::sync::Mutex<HashMap<TrackedPath, Arc<tokio::sync::Mutex<()>>>>>,
 }
 
 pub(crate) struct FileMutationPermit {
@@ -75,8 +81,7 @@ pub(crate) struct FileMutationPermit {
 }
 
 impl FileMutationCoordinator {
-    async fn acquire(&self, path: &Path) -> FileMutationPermit {
-        let key = file_mutation_key(path);
+    async fn acquire(&self, key: TrackedPath) -> FileMutationPermit {
         let lock = {
             let mut locks = self.locks.lock().await;
             locks
@@ -127,12 +132,12 @@ pub struct ChangeStat {
 
 #[derive(Debug, Default)]
 struct Inner {
-    /// Hash of each file's last observed contents, keyed by canonical path.
-    hashes: HashMap<PathBuf, ContentHash>,
+    /// Hash of each file's last observed contents, keyed by attachment and canonical path.
+    hashes: HashMap<TrackedPath, ContentHash>,
     /// Line count paired with observations that included the file content.
-    line_counts: HashMap<PathBuf, usize>,
+    line_counts: HashMap<TrackedPath, usize>,
     /// LRU list of touched files. Front = most recently touched.
-    recency: VecDeque<PathBuf>,
+    recency: VecDeque<TrackedPath>,
     /// Successful Write/Edit mutations attributed to this session's tools.
     change_stat: ChangeStat,
 }
@@ -146,6 +151,7 @@ struct Inner {
 pub struct Tracker {
     inner: Arc<Mutex<Inner>>,
     mutations: FileMutationCoordinator,
+    namespace: Option<Arc<str>>,
 }
 
 impl Tracker {
@@ -154,6 +160,33 @@ impl Tracker {
         Self::default()
     }
 
+    /// Return a view whose read-before-mutation state is isolated to one
+    /// attachment incarnation (the Worker-local alias plus router generation),
+    /// while aggregate recency/change statistics remain shared with the Worker
+    /// tracker.
+    pub fn scoped(&self, namespace: impl Into<String>) -> Self {
+        Self {
+            inner: self.inner.clone(),
+            mutations: self.mutations.clone(),
+            namespace: Some(Arc::from(namespace.into())),
+        }
+    }
+
+    pub(crate) fn scoped_attachment(
+        &self,
+        alias: &workdir::WorkdirAttachmentAlias,
+        generation: u64,
+    ) -> Self {
+        self.scoped(format!("{}#{generation}", alias.as_str()))
+    }
+
+    fn key(&self, path: PathBuf) -> TrackedPath {
+        TrackedPath {
+            namespace: self.namespace.clone(),
+            path,
+        }
+    }
+
     /// Acquire the per-target-file mutation guard shared by `Write` and `Edit`.
     ///
     /// The guard is keyed by canonical target path where possible so equivalent
@@ -170,7 +203,9 @@ impl Tracker {
             call_index = ctx.call_index,
             "acquire file mutation guard"
         );
-        self.mutations.acquire(path).await
+        self.mutations
+            .acquire(self.key(file_mutation_key(path)))
+            .await
     }
 
     /// Record that `path` has been observed with the given content bytes.
@@ -182,7 +217,7 @@ impl Tracker {
     /// Also bumps `path` to the front of the recency list. If the list
     /// grows past [`RECENCY_CAPACITY`], the oldest entry is evicted.
     pub fn record(&self, path: &Path, bytes: &[u8]) {
-        let key = canonicalize_or_owned(path);
+        let key = self.key(canonicalize_or_owned(path));
         let hash = hash_bytes(bytes);
         let mut inner = self.inner.lock().unwrap_or_else(|e| e.into_inner());
         inner.hashes.insert(key.clone(), hash);
@@ -198,7 +233,7 @@ impl Tracker {
     }
 
     pub fn record_workdir_content(&self, path: &workdir::WorkdirPath, content: &[u8]) {
-        let key = PathBuf::from(path.as_str());
+        let key = self.key(PathBuf::from(path.as_str()));
         let hash = hash_bytes(content);
         let line_count = String::from_utf8_lossy(content).lines().count();
         let mut inner = self.inner.lock().unwrap_or_else(|e| e.into_inner());
@@ -212,16 +247,17 @@ impl Tracker {
     }
 
     pub fn observed_workdir_line_count(&self, path: &workdir::WorkdirPath) -> Option<usize> {
+        let key = self.key(PathBuf::from(path.as_str()));
         self.inner
             .lock()
             .unwrap_or_else(|e| e.into_inner())
             .line_counts
-            .get(Path::new(path.as_str()))
+            .get(&key)
             .copied()
     }
 
     pub fn record_workdir_hash(&self, path: &workdir::WorkdirPath, hash: workdir::ContentHash) {
-        let key = PathBuf::from(path.as_str());
+        let key = self.key(PathBuf::from(path.as_str()));
         let mut inner = self.inner.lock().unwrap_or_else(|e| e.into_inner());
         inner.hashes.insert(key.clone(), hash);
         inner.recency.retain(|candidate| candidate != &key);
@@ -253,7 +289,7 @@ impl Tracker {
     ) {
         let added = added_lines_per_replacement.saturating_mul(replacements);
         let deleted = deleted_lines_per_replacement.saturating_mul(replacements);
-        let key = PathBuf::from(path.as_str());
+        let key = self.key(PathBuf::from(path.as_str()));
         let mut inner = self.inner.lock().unwrap_or_else(|e| e.into_inner());
         inner.change_stat.added = inner.change_stat.added.saturating_add(added as u64);
         inner.change_stat.deleted = inner.change_stat.deleted.saturating_add(deleted as u64);
@@ -279,14 +315,14 @@ impl Tracker {
         &self,
         path: &workdir::WorkdirPath,
     ) -> Result<workdir::ContentHash, ToolsError> {
-        let key = PathBuf::from(path.as_str());
+        let key = self.key(PathBuf::from(path.as_str()));
         self.inner
             .lock()
             .unwrap_or_else(|error| error.into_inner())
             .hashes
             .get(&key)
             .copied()
-            .ok_or_else(|| ToolsError::NotRead(key))
+            .ok_or_else(|| ToolsError::NotRead(key.path.clone()))
     }
 
     /// Verify that `path` was previously recorded and its current bytes
@@ -296,7 +332,7 @@ impl Tracker {
     /// - If the current content hashes differ from the recorded value,
     ///   returns [`ToolsError::ExternallyModified`].
     pub fn verify(&self, path: &Path, current_bytes: &[u8]) -> Result<(), ToolsError> {
-        let key = canonicalize_or_owned(path);
+        let key = self.key(canonicalize_or_owned(path));
         let guard = self.inner.lock().unwrap_or_else(|e| e.into_inner());
         let recorded = guard
             .hashes
@@ -316,13 +352,18 @@ impl Tracker {
     /// can pass them as default references to the compaction worker.
     pub fn recent_files(&self, n: usize) -> Vec<PathBuf> {
         let inner = self.inner.lock().unwrap_or_else(|e| e.into_inner());
-        inner.recency.iter().take(n).cloned().collect()
+        inner
+            .recency
+            .iter()
+            .take(n)
+            .map(|key| key.path.clone())
+            .collect()
     }
 
     /// Returns true if `path` has a history entry. Test-only.
     #[cfg(test)]
     pub(crate) fn has(&self, path: &Path) -> bool {
-        let key = canonicalize_or_owned(path);
+        let key = self.key(canonicalize_or_owned(path));
         self.inner
             .lock()
             .unwrap_or_else(|e| e.into_inner())
@@ -420,6 +461,22 @@ mod tests {
         }
     }
 
+    #[test]
+    fn attachment_namespaces_do_not_share_read_state() {
+        let tracker = Tracker::new();
+        let left = tracker.scoped("left");
+        let right = tracker.scoped("right");
+        let path = workdir::WorkdirPath::new("same.txt").unwrap();
+
+        left.record_workdir_content(&path, b"left");
+
+        assert!(left.expected_workdir_hash(&path).is_ok());
+        assert!(matches!(
+            right.expected_workdir_hash(&path),
+            Err(ToolsError::NotRead(_))
+        ));
+    }
+
     #[test]
     fn clone_shares_state() {
         let dir = TempDir::new().unwrap();

crates/tools/src/view_image.rs

@@ -7,24 +7,28 @@ use agen::tool::{
 };
 use async_trait::async_trait;
 use serde::Deserialize;
-use workdir::{ReadRequest, WorkdirPath, WorkdirSessionHandle};
+use workdir::{ReadRequest, WorkdirPath, WorkdirSessionHandle, WorkdirSessionRouter};
 
 use crate::error::ToolsError;
 
 /// Maximum image body accepted for one model request.
 pub const MAX_IMAGE_BYTES: usize = 10 * 1024 * 1024;
 
-const DESCRIPTION: &str = "Attach an image from the bound Workdir to the next model request. \
-The path must be logical and Workdir-relative. Supported formats: PNG, JPEG, GIF, and WebP.";
+const DESCRIPTION: &str = "Attach an image from the selected Workdir attachment to the next model request. \
+The path must be logical and Workdir-relative. Supported formats: PNG, JPEG, GIF, and WebP. \
+When exactly one Workdir is attached, target_workdir may be omitted.";
 
 #[derive(Debug, Deserialize, schemars::JsonSchema)]
 struct ViewImageParams {
+    /// Worker-local alias of the Workdir attachment to use.
+    #[serde(default)]
+    target_workdir: Option<String>,
     /// Logical path relative to the bound Workdir root.
     path: String,
 }
 
 struct ViewImageTool {
-    session: WorkdirSessionHandle,
+    router: Arc<WorkdirSessionRouter>,
 }
 
 #[async_trait]
@@ -37,8 +41,13 @@ impl Tool for ViewImageTool {
         let input: ViewImageParams = serde_json::from_str(input_json).map_err(|error| {
             ToolError::InvalidArgument(format!("invalid ViewImage input: {error}"))
         })?;
+        let selected = crate::routing::resolve_session(
+            &self.router,
+            input.target_workdir.as_deref(),
+            workdir::WorkdirSessionCapability::Read,
+        )?;
         let path = WorkdirPath::new(&input.path).map_err(ToolsError::from)?;
-        let result = self
+        let result = selected
             .session
             .read(ReadRequest {
                 path: path.clone(),
@@ -75,6 +84,10 @@ impl Tool for ViewImageTool {
 }
 
 pub fn view_image_tool(session: WorkdirSessionHandle) -> ToolDefinition {
+    routed_view_image_tool(crate::routing::singleton_router(session))
+}
+
+pub fn routed_view_image_tool(router: Arc<WorkdirSessionRouter>) -> ToolDefinition {
     Arc::new(move || {
         let schema = schemars::schema_for!(ViewImageParams);
         let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
@@ -82,7 +95,7 @@ pub fn view_image_tool(session: WorkdirSessionHandle) -> ToolDefinition {
             .description(DESCRIPTION)
             .input_schema(schema_value);
         let tool: Arc<dyn Tool> = Arc::new(ViewImageTool {
-            session: session.clone(),
+            router: router.clone(),
         });
         (meta, tool)
     })

crates/tools/src/write.rs

@@ -9,15 +9,20 @@ use serde::Deserialize;
 
 use crate::error::ToolsError;
 use crate::tracker::Tracker;
-use workdir::{StatRequest, WorkdirError, WorkdirPath, WorkdirSessionHandle, WriteRequest};
+use workdir::{
+    StatRequest, WorkdirError, WorkdirPath, WorkdirSessionHandle, WorkdirSessionRouter,
+    WriteRequest,
+};
 
-const DESCRIPTION: &str = "Create a new file or overwrite an existing one with \
-the given content. Missing parent directories within scope are created \
-automatically. Existing files must have been read first (via the Read tool) \
-in this session. Paths are relative to the bound Workdir.";
+const DESCRIPTION: &str = "Create a new file or overwrite an existing one in the selected Workdir attachment. \
+Missing parent directories within scope are created automatically. Existing files must have been read first \
+through the same attachment. When exactly one Workdir is attached, target_workdir may be omitted.";
 
 #[derive(Debug, Deserialize, schemars::JsonSchema)]
 pub(crate) struct WriteParams {
+    /// Worker-local alias of the Workdir attachment to use.
+    #[serde(default)]
+    pub target_workdir: Option<String>,
     /// Logical path relative to the bound Workdir root.
     pub file_path: String,
     /// Full content to write. Overwrites any existing content.
@@ -25,7 +30,7 @@ pub(crate) struct WriteParams {
 }
 
 pub(crate) struct WriteTool {
-    session: WorkdirSessionHandle,
+    router: Arc<WorkdirSessionRouter>,
     tracker: Tracker,
 }
 
@@ -39,19 +44,31 @@ impl Tool for WriteTool {
         let params: WriteParams = serde_json::from_str(input_json)
             .map_err(|e| ToolError::InvalidArgument(format!("invalid Write input: {e}")))?;
 
+        let selected = crate::routing::resolve_session(
+            &self.router,
+            params.target_workdir.as_deref(),
+            workdir::WorkdirSessionCapability::Write,
+        )?;
+        let tracker = self
+            .tracker
+            .scoped_attachment(&selected.alias, selected.generation);
         let path = WorkdirPath::new(&params.file_path).map_err(ToolsError::from)?;
         tracing::debug!(path = %path, bytes = params.content.len(), "Write");
 
         let mutation_key = PathBuf::from(path.as_str());
-        let _mutation_permit = self.tracker.acquire_mutation(&mutation_key, &ctx).await;
-        let expected_hash = match self.session.stat(StatRequest { path: path.clone() }).await {
-            Ok(_) => Some(self.tracker.expected_workdir_hash(&path)?),
+        let _mutation_permit = tracker.acquire_mutation(&mutation_key, &ctx).await;
+        let expected_hash = match selected
+            .session
+            .stat(StatRequest { path: path.clone() })
+            .await
+        {
+            Ok(_) => Some(tracker.expected_workdir_hash(&path)?),
             Err(WorkdirError::NotFound(_)) => None,
             Err(error) => return Err(ToolsError::from(error).into()),
         };
 
-        let old_line_count = self.tracker.observed_workdir_line_count(&path).unwrap_or(0);
-        let outcome = self
+        let old_line_count = tracker.observed_workdir_line_count(&path).unwrap_or(0);
+        let outcome = selected
             .session
             .write(WriteRequest {
                 path: path.clone(),
@@ -61,10 +78,8 @@ impl Tool for WriteTool {
             .await
             .map_err(ToolsError::from)?;
 
-        self.tracker
-            .record_change(params.content.lines().count(), old_line_count);
-        self.tracker
-            .record_workdir_content(&path, params.content.as_bytes());
+        tracker.record_change(params.content.lines().count(), old_line_count);
+        tracker.record_workdir_content(&path, params.content.as_bytes());
 
         let summary = format!(
             "{} {} ({} bytes)",
@@ -84,8 +99,15 @@ impl Tool for WriteTool {
     }
 }
 
-/// Factory for the `Write` tool.
+/// Factory for the `Write` tool bound to one compatibility session.
 pub fn write_tool(session: WorkdirSessionHandle, tracker: Tracker) -> ToolDefinition {
+    routed_write_tool(crate::routing::singleton_router(session), tracker)
+}
+
+pub(crate) fn routed_write_tool(
+    router: Arc<WorkdirSessionRouter>,
+    tracker: Tracker,
+) -> ToolDefinition {
     Arc::new(move || {
         let schema = schemars::schema_for!(WriteParams);
         let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
@@ -93,7 +115,7 @@ pub fn write_tool(session: WorkdirSessionHandle, tracker: Tracker) -> ToolDefini
             .description(DESCRIPTION)
             .input_schema(schema_value);
         let tool: Arc<dyn Tool> = Arc::new(WriteTool {
-            session: session.clone(),
+            router: router.clone(),
             tracker: tracker.clone(),
         });
         (meta, tool)

crates/tools/tests/integration.rs

@@ -14,8 +14,12 @@ use agen::tool::{
 use manifest::{Permission, Scope, ScopeConfig, ScopeRule};
 use serde_json::json;
 use tempfile::TempDir;
-use tools::{Tracker, core_builtin_tools, view_image_tool};
-use workdir::{LocalWorkdirSession, WorkdirSessionHandle};
+use tools::{
+    Tracker, core_builtin_tools, routed_builtin_tools, routed_view_image_tool, view_image_tool,
+};
+use workdir::{
+    LocalWorkdirSession, WorkdirAttachmentAlias, WorkdirSessionHandle, WorkdirSessionRouter,
+};
 
 fn scope_with_spill(workspace: &Path, spill: &Path) -> Scope {
     let base = Scope::writable(workspace).unwrap();
@@ -66,6 +70,30 @@ fn setup() -> (TempDir, TempDir, Registry) {
     (dir, spill, reg)
 }
 
+fn setup_routed() -> (
+    TempDir,
+    TempDir,
+    TempDir,
+    Arc<WorkdirSessionRouter>,
+    Registry,
+) {
+    let left = TempDir::new().unwrap();
+    let right = TempDir::new().unwrap();
+    let spill = TempDir::new().unwrap();
+    let router = Arc::new(WorkdirSessionRouter::new());
+    for (alias, dir) in [("left", &left), ("right", &right)] {
+        let scope = scope_with_spill(dir.path(), spill.path());
+        let session: WorkdirSessionHandle =
+            Arc::new(LocalWorkdirSession::new(scope, dir.path().to_path_buf()));
+        router
+            .attach(WorkdirAttachmentAlias::new(alias).unwrap(), session)
+            .unwrap();
+    }
+    let definitions =
+        routed_builtin_tools(router.clone(), Tracker::new(), spill.path().to_path_buf());
+    (left, right, spill, router, Registry::new(definitions))
+}
+
 async fn call(tool: &Arc<dyn Tool>, input: serde_json::Value) -> agen::tool::ToolOutput {
     tool.execute(&input.to_string(), Default::default())
         .await
@@ -104,6 +132,273 @@ fn meta_has_description_and_schema() {
     }
 }
 
+#[test]
+fn routed_tool_schemas_share_optional_target_workdir() {
+    let (_left, _right, _spill, router, mut reg) = setup_routed();
+    reg.entries.push(routed_view_image_tool(router)());
+    for (meta, _) in &reg.entries {
+        let target = &meta.input_schema["properties"]["target_workdir"];
+        assert!(target.is_object(), "{} lacks target_workdir", meta.name);
+        assert_eq!(target["type"], json!(["string", "null"]));
+    }
+}
+
+#[tokio::test]
+async fn routed_tools_require_alias_only_when_attachment_set_is_ambiguous() {
+    let (_left, _right, _spill, router, reg) = setup_routed();
+    let error = call_err(&reg.get("Read"), json!({ "file_path": "same.txt" })).await;
+    let message = error.to_string();
+    assert!(message.contains("target_workdir_required"), "{message}");
+    assert!(message.contains("left"), "{message}");
+    assert!(message.contains("right"), "{message}");
+
+    let unknown = call_err(
+        &reg.get("Glob"),
+        json!({ "target_workdir": "missing", "pattern": "*" }),
+    )
+    .await
+    .to_string();
+    assert!(unknown.contains("unknown_target_workdir"), "{unknown}");
+    assert!(unknown.contains("available_aliases"), "{unknown}");
+
+    router.close_all().await.unwrap();
+}
+
+#[tokio::test]
+async fn empty_routed_surface_returns_no_attachment_error() {
+    let router = Arc::new(WorkdirSessionRouter::new());
+    let reg = Registry::new(routed_builtin_tools(
+        router,
+        Tracker::new(),
+        Path::new("unused").to_path_buf(),
+    ));
+    let message = call_err(&reg.get("Read"), json!({ "file_path": "file.txt" }))
+        .await
+        .to_string();
+    assert!(message.contains("no_workdir_attached"), "{message}");
+}
+
+#[tokio::test]
+async fn target_alias_routes_each_tool_and_isolates_read_before_edit() {
+    let (left, right, _spill, router, mut reg) = setup_routed();
+    std::fs::write(left.path().join("same.txt"), "left value\n").unwrap();
+    std::fs::write(right.path().join("same.txt"), "right value\n").unwrap();
+    std::fs::write(left.path().join("only-left.log"), "LEFT-NEEDLE\n").unwrap();
+    std::fs::write(right.path().join("only-right.log"), "RIGHT-NEEDLE\n").unwrap();
+
+    let read = reg.get("Read");
+    let left_read = call(
+        &read,
+        json!({ "target_workdir": "left", "file_path": "same.txt" }),
+    )
+    .await;
+    assert!(left_read.content.unwrap().contains("left value"));
+
+    let edit = reg.get("Edit");
+    let isolated = call_err(
+        &edit,
+        json!({
+            "target_workdir": "right",
+            "file_path": "same.txt",
+            "old_string": "right",
+            "new_string": "edited"
+        }),
+    )
+    .await;
+    assert!(isolated.to_string().contains("has not been read"));
+    call(
+        &read,
+        json!({ "target_workdir": "right", "file_path": "same.txt" }),
+    )
+    .await;
+    call(
+        &edit,
+        json!({
+            "target_workdir": "right",
+            "file_path": "same.txt",
+            "old_string": "right",
+            "new_string": "edited"
+        }),
+    )
+    .await;
+    assert_eq!(
+        std::fs::read_to_string(right.path().join("same.txt")).unwrap(),
+        "edited value\n"
+    );
+    assert_eq!(
+        std::fs::read_to_string(left.path().join("same.txt")).unwrap(),
+        "left value\n"
+    );
+
+    let glob = call(
+        &reg.get("Glob"),
+        json!({ "target_workdir": "left", "pattern": "*.log" }),
+    )
+    .await;
+    assert!(glob.content.unwrap().contains("only-left.log"));
+    let grep = call(
+        &reg.get("Grep"),
+        json!({
+            "target_workdir": "right",
+            "pattern": "RIGHT-NEEDLE",
+            "output_mode": "content"
+        }),
+    )
+    .await;
+    assert!(grep.content.unwrap().contains("only-right.log"));
+
+    let bash = call(
+        &reg.get("Bash"),
+        json!({ "target_workdir": "right", "command": "pwd" }),
+    )
+    .await;
+    assert_eq!(
+        std::fs::canonicalize(bash.content.unwrap().trim()).unwrap(),
+        std::fs::canonicalize(right.path()).unwrap()
+    );
+
+    let png = b"\x89PNG\r\n\x1a\nrouted";
+    std::fs::write(left.path().join("image.png"), png).unwrap();
+    reg.entries.push(routed_view_image_tool(router.clone())());
+    let image = call(
+        &reg.get("ViewImage"),
+        json!({ "target_workdir": "left", "path": "image.png" }),
+    )
+    .await;
+    let agen::tool::Attachment::Image(image) = &image.attachments[0];
+    assert_eq!(image.data(), png);
+
+    router.close_all().await.unwrap();
+}
+
+#[tokio::test]
+async fn selected_attachment_capability_is_checked_without_fallback() {
+    let left = TempDir::new().unwrap();
+    let right = TempDir::new().unwrap();
+    let spill = TempDir::new().unwrap();
+    let router = Arc::new(WorkdirSessionRouter::new());
+    router
+        .attach(
+            WorkdirAttachmentAlias::new("writable").unwrap(),
+            Arc::new(LocalWorkdirSession::new(
+                scope_with_spill(left.path(), spill.path()),
+                left.path().to_path_buf(),
+            )),
+        )
+        .unwrap();
+    router
+        .attach(
+            WorkdirAttachmentAlias::new("readonly").unwrap(),
+            Arc::new(LocalWorkdirSession::materialized_bound(
+                workdir::Workdir::new("readonly"),
+                right.path().to_path_buf(),
+                right.path().to_path_buf(),
+                manifest::SharedScope::new(scope_with_spill(right.path(), spill.path())),
+                workdir::WorkdirSessionCapabilities::READ_ONLY,
+            )),
+        )
+        .unwrap();
+    let reg = Registry::new(routed_builtin_tools(
+        router.clone(),
+        Tracker::new(),
+        spill.path().to_path_buf(),
+    ));
+
+    let message = call_err(
+        &reg.get("Write"),
+        json!({
+            "target_workdir": "readonly",
+            "file_path": "created.txt",
+            "content": "must not be routed elsewhere"
+        }),
+    )
+    .await
+    .to_string();
+    assert!(message.contains("does not support Write"), "{message}");
+    assert!(!left.path().join("created.txt").exists());
+    assert!(!right.path().join("created.txt").exists());
+
+    router.close_all().await.unwrap();
+}
+
+#[tokio::test]
+async fn routed_tools_observe_detach_after_registration() {
+    let (_left, _right, _spill, router, reg) = setup_routed();
+    let alias = WorkdirAttachmentAlias::new("left").unwrap();
+    router.detach(&alias).await.unwrap();
+
+    let message = call_err(
+        &reg.get("Glob"),
+        json!({ "target_workdir": "left", "pattern": "*" }),
+    )
+    .await
+    .to_string();
+    assert!(message.contains("unknown_target_workdir"), "{message}");
+    assert!(message.contains("right"), "{message}");
+
+    router.close_all().await.unwrap();
+}
+
+#[tokio::test]
+async fn detach_and_reattach_same_alias_requires_a_fresh_read() {
+    let first = TempDir::new().unwrap();
+    let second = TempDir::new().unwrap();
+    let spill = TempDir::new().unwrap();
+    std::fs::write(first.path().join("same.txt"), "same bytes\n").unwrap();
+    std::fs::write(second.path().join("same.txt"), "same bytes\n").unwrap();
+
+    let router = Arc::new(WorkdirSessionRouter::new());
+    let alias = WorkdirAttachmentAlias::new("checkout").unwrap();
+    router
+        .attach(
+            alias.clone(),
+            Arc::new(LocalWorkdirSession::new(
+                scope_with_spill(first.path(), spill.path()),
+                first.path().to_path_buf(),
+            )),
+        )
+        .unwrap();
+    let reg = Registry::new(routed_builtin_tools(
+        router.clone(),
+        Tracker::new(),
+        spill.path().to_path_buf(),
+    ));
+    call(
+        &reg.get("Read"),
+        json!({ "target_workdir": "checkout", "file_path": "same.txt" }),
+    )
+    .await;
+
+    router.detach(&alias).await.unwrap();
+    router
+        .attach(
+            alias.clone(),
+            Arc::new(LocalWorkdirSession::new(
+                scope_with_spill(second.path(), spill.path()),
+                second.path().to_path_buf(),
+            )),
+        )
+        .unwrap();
+
+    let error = call_err(
+        &reg.get("Edit"),
+        json!({
+            "target_workdir": "checkout",
+            "file_path": "same.txt",
+            "old_string": "same",
+            "new_string": "changed"
+        }),
+    )
+    .await;
+    assert!(error.to_string().contains("has not been read"), "{error}");
+    assert_eq!(
+        std::fs::read_to_string(second.path().join("same.txt")).unwrap(),
+        "same bytes\n"
+    );
+
+    router.close_all().await.unwrap();
+}
+
 #[tokio::test]
 async fn view_image_reads_scoped_bytes_into_durable_tool_detail() {
     let dir = TempDir::new().unwrap();

crates/tui/src/backend_spawn.rs

@@ -164,7 +164,7 @@ fn request_from_selection(selection: Selection) -> BackendCreateWorkerRequest {
         display_name: selection.display_name,
         profile: Some(selection.profile),
         initial_submit: Vec::new(),
-        working_directory: None,
+        workdir_attachments: Vec::new(),
         ticket_assignment: None,
         control_operation_id: None,
     }
@@ -477,7 +477,7 @@ mod tests {
         assert_eq!(request.display_name, "Coder one");
         assert_eq!(request.profile.as_deref(), Some("builtin:coder"));
         assert!(request.initial_submit.is_empty());
-        assert!(request.working_directory.is_none());
+        assert!(request.workdir_attachments.is_empty());
         assert!(request.ticket_assignment.is_none());
     }
 }

crates/tui/src/backend_worker_picker.rs

@@ -408,10 +408,22 @@ fn short_worker_id(worker: &BackendWorkerSummary) -> String {
 }
 
 fn working_directory_text(worker: &BackendWorkerSummary) -> String {
-    let Some(wd) = worker.working_directory.as_ref() else {
+    if worker.workdir_attachments.is_empty() {
         return "wd:—".to_string();
-    };
-    format!("wd:{}・{}", wd.repository_key, wd.working_directory_id)
+    }
+    if worker.workdir_attachments.len() > 1 {
+        return format!("wd:{} attachments", worker.workdir_attachments.len());
+    }
+    let attachment = &worker.workdir_attachments[0];
+    let directory = &attachment.working_directory;
+    let label = directory
+        .display_name
+        .as_deref()
+        .unwrap_or(&directory.repository_key);
+    format!(
+        "wd:{}:{}・{}",
+        attachment.alias, label, directory.working_directory_id
+    )
 }
 
 #[cfg(test)]
@@ -456,7 +468,7 @@ mod tests {
                 can_stop: true,
                 can_spawn_followup: false,
             },
-            working_directory: None,
+            workdir_attachments: Vec::new(),
             diagnostics: Vec::new(),
         }
     }
@@ -529,22 +541,26 @@ mod tests {
         worker.label = "Coder · T-585".to_string();
         worker.state = "stopped".to_string();
         worker.worker_state = None;
-        worker.working_directory = Some(
+        worker.workdir_attachments = vec![
             serde_json::from_value(serde_json::json!({
-                "working_directory_id": "001a06a9f0202000000",
-                "repository_key": "main",
-                "materializer_kind": "runtime_git_clone",
-                "status": "active",
-                "cleanliness": "clean"
+                "alias": "checkout",
+                "working_directory": {
+                    "working_directory_id": "001a06a9f0202000000",
+                    "display_name": "Checkout",
+                    "repository_key": "main",
+                    "materializer_kind": "runtime_git_clone",
+                    "status": "active",
+                    "cleanliness": "clean"
+                }
             }))
             .unwrap(),
-        );
+        ];
         let widths = WorkerColumnWidths::from_workers(std::slice::from_ref(&worker));
         let text = row_text(&worker, &widths);
 
         assert_eq!(
             text,
-            "  W-90  Coder · T-585  [stopped]  wd:main・001a06a9f0202000000"
+            "  W-90  Coder · T-585  [stopped]  wd:checkout:Checkout・001a06a9f0202000000"
         );
         assert!(!text.contains("profile:"));
         assert!(!text.contains("active clean"));
@@ -570,15 +586,18 @@ mod tests {
         long.worker_state = None;
 
         for worker in [&mut short, &mut long] {
-            worker.working_directory = Some(
+            worker.workdir_attachments = vec![
                 serde_json::from_value(serde_json::json!({
-                    "working_directory_id": "workdir-1",
-                    "repository_key": "main",
-                    "materializer_kind": "runtime_git_clone",
-                    "status": "active"
+                    "alias": "checkout",
+                    "working_directory": {
+                        "working_directory_id": "workdir-1",
+                        "repository_key": "main",
+                        "materializer_kind": "runtime_git_clone",
+                        "status": "active"
+                    }
                 }))
                 .unwrap(),
-            );
+            ];
         }
 
         let workers = vec![short, long];
@@ -595,8 +614,8 @@ mod tests {
             display_column(&second, "[stopped]")
         );
         assert_eq!(
-            display_column(&first, "wd:main"),
-            display_column(&second, "wd:main")
+            display_column(&first, "wd:checkout:main"),
+            display_column(&second, "wd:checkout:main")
         );
     }
 

crates/workdir/src/lib.rs

@@ -8,6 +8,7 @@
 pub mod http;
 mod local;
 mod operation;
+mod router;
 mod scope;
 pub mod workspace;
 
@@ -27,10 +28,14 @@ pub use local::{
     LocalWorkdirSession, SymlinkInfo, WorkdirSessionResource, direct_symlink, first_symlink,
 };
 pub use operation::*;
+pub use router::{
+    ResolvedWorkdirSession, RoutedWorkdirSession, WorkdirAttachmentAlias, WorkdirRouteError,
+    WorkdirRouteErrorCode, WorkdirSessionRouter,
+};
 pub use scope::{
     ReadOnlyWorkdirSession, WorkdirScopeAuthorizationRequest, WorkdirScopeLease,
-    WorkdirScopeOverlapRequest, WorkdirToolBroker, WorkdirToolScope, WorkdirToolScopePermission,
-    WorkdirToolScopeRule,
+    WorkdirScopeLeaseSet, WorkdirScopeOverlapRequest, WorkdirToolBroker, WorkdirToolBrokerRouter,
+    WorkdirToolScope, WorkdirToolScopePermission, WorkdirToolScopeRule,
 };
 
 /// Persistent, opaque identity of one materialized Workdir.
@@ -122,6 +127,12 @@ impl WorkdirSessionCapabilities {
         bits: Self::READ | Self::GLOB | Self::GREP,
     };
 
+    pub const fn union(self, other: Self) -> Self {
+        Self {
+            bits: self.bits | other.bits,
+        }
+    }
+
     pub const fn supports(self, capability: WorkdirSessionCapability) -> bool {
         let bit = match capability {
             WorkdirSessionCapability::Read => Self::READ,

crates/workdir/src/router.rs

@@ -0,0 +1,796 @@
+//! Alias-keyed Worker Workdir session routing.
+//!
+//! The router owns live provider sessions without exposing whether a session is
+//! local or transported over HTTP.  Attachment aliases are Worker-local stable
+//! identities; provider Workdir ids and human display names are deliberately not
+//! routing keys.
+
+use std::collections::{BTreeMap, HashSet};
+use std::sync::atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering};
+use std::sync::{Arc, Mutex, RwLock};
+
+use async_trait::async_trait;
+use serde::{Deserialize, Serialize};
+use tokio::sync::broadcast;
+
+use crate::{
+    CommandEvent, CommandHandle, CommandOutput, CommandOutputRequest, CommandRequest,
+    CommandSnapshot, CommandStatus, EditRequest, EditResult, GlobRequest, GlobResult, GrepRequest,
+    GrepResult, ListRequest, ListResult, ReadRequest, ReadResult, StatRequest, StatResult, Workdir,
+    WorkdirError, WorkdirScopeAuthorizationRequest, WorkdirScopeOverlapRequest, WorkdirSession,
+    WorkdirSessionCapabilities, WorkdirSessionHandle, WriteRequest, WriteResult,
+};
+
+/// Stable Worker-local routing key for one attached Workdir.
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize)]
+#[serde(transparent)]
+pub struct WorkdirAttachmentAlias(String);
+
+impl WorkdirAttachmentAlias {
+    pub fn new(value: impl Into<String>) -> Result<Self, WorkdirError> {
+        let value = value.into();
+        let valid = !value.is_empty()
+            && value.len() <= 64
+            && value.bytes().enumerate().all(|(index, byte)| match byte {
+                b'a'..=b'z' | b'A'..=b'Z' | b'0'..=b'9' => true,
+                b'_' | b'-' | b'.' => index > 0,
+                _ => false,
+            });
+        if !valid {
+            return Err(WorkdirError::InvalidArgument(
+                "attachment alias must be 1-64 ASCII letters, digits, '.', '_' or '-', and start with a letter or digit"
+                    .to_string(),
+            ));
+        }
+        Ok(Self(value))
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+}
+
+impl<'de> Deserialize<'de> for WorkdirAttachmentAlias {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let value = String::deserialize(deserializer)?;
+        Self::new(value).map_err(serde::de::Error::custom)
+    }
+}
+
+impl std::fmt::Display for WorkdirAttachmentAlias {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        formatter.write_str(&self.0)
+    }
+}
+
+/// Stable machine-readable reason why a tool target could not be resolved.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum WorkdirRouteErrorCode {
+    NoWorkdirAttached,
+    TargetWorkdirRequired,
+    UnknownTargetWorkdir,
+}
+
+/// Provider-neutral attachment routing failure returned before an operation starts.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize)]
+pub struct WorkdirRouteError {
+    pub code: WorkdirRouteErrorCode,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub target_workdir: Option<String>,
+    pub available_aliases: Vec<String>,
+}
+
+impl std::fmt::Display for WorkdirRouteError {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let encoded = serde_json::to_string(self).map_err(|_| std::fmt::Error)?;
+        formatter.write_str(&encoded)
+    }
+}
+
+impl std::error::Error for WorkdirRouteError {}
+
+/// One attachment selected for a single tool invocation.
+#[derive(Clone)]
+pub struct ResolvedWorkdirSession {
+    pub alias: WorkdirAttachmentAlias,
+    pub generation: u64,
+    pub session: WorkdirSessionHandle,
+}
+
+impl std::fmt::Debug for ResolvedWorkdirSession {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        formatter
+            .debug_struct("ResolvedWorkdirSession")
+            .field("alias", &self.alias)
+            .field("generation", &self.generation)
+            .field("workdir", self.session.workdir())
+            .finish_non_exhaustive()
+    }
+}
+
+#[derive(Debug)]
+struct RoutedSessionState {
+    session: WorkdirSessionHandle,
+    generation: u64,
+    detached: AtomicBool,
+    active_operations: AtomicUsize,
+    active_commands: Mutex<HashSet<CommandHandle>>,
+}
+
+impl RoutedSessionState {
+    fn enter(&self) -> Result<ActiveOperation<'_>, WorkdirError> {
+        if self.detached.load(Ordering::Acquire) {
+            return Err(WorkdirError::Unavailable(
+                "Workdir attachment is detached".to_string(),
+            ));
+        }
+        self.active_operations.fetch_add(1, Ordering::AcqRel);
+        if self.detached.load(Ordering::Acquire) {
+            self.active_operations.fetch_sub(1, Ordering::AcqRel);
+            return Err(WorkdirError::Unavailable(
+                "Workdir attachment is detaching".to_string(),
+            ));
+        }
+        Ok(ActiveOperation(self))
+    }
+
+    fn is_busy(&self) -> bool {
+        if self.active_operations.load(Ordering::Acquire) != 0 {
+            return true;
+        }
+        self.reconcile_terminal_commands(&self.session.command_snapshot());
+        !self
+            .active_commands
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .is_empty()
+    }
+
+    async fn is_busy_for_detach(&self) -> bool {
+        if self.active_operations.load(Ordering::Acquire) != 0 {
+            return true;
+        }
+        self.reconcile_terminal_commands(&self.session.command_snapshot());
+        let handles = self
+            .active_commands
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .iter()
+            .cloned()
+            .collect::<Vec<_>>();
+        for handle in handles {
+            match self.session.command_status(handle.clone()).await {
+                Ok(status) => self.mark_terminal(&handle, status),
+                Err(WorkdirError::UnknownCommand(_)) => {
+                    self.active_commands
+                        .lock()
+                        .unwrap_or_else(std::sync::PoisonError::into_inner)
+                        .remove(&handle);
+                }
+                Err(_) => {}
+            }
+        }
+        self.active_operations.load(Ordering::Acquire) != 0
+            || !self
+                .active_commands
+                .lock()
+                .unwrap_or_else(std::sync::PoisonError::into_inner)
+                .is_empty()
+    }
+
+    fn reconcile_terminal_commands(&self, snapshots: &[CommandSnapshot]) {
+        let terminal = snapshots
+            .iter()
+            .filter(|snapshot| snapshot.status != CommandStatus::Running)
+            .map(|snapshot| snapshot.command_id.as_str())
+            .collect::<HashSet<_>>();
+        if terminal.is_empty() {
+            return;
+        }
+        self.active_commands
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .retain(|handle| !terminal.contains(handle.0.as_str()));
+    }
+
+    fn mark_terminal(&self, handle: &CommandHandle, status: CommandStatus) {
+        if status != CommandStatus::Running {
+            self.active_commands
+                .lock()
+                .unwrap_or_else(std::sync::PoisonError::into_inner)
+                .remove(handle);
+        }
+    }
+}
+
+struct ActiveOperation<'a>(&'a RoutedSessionState);
+
+impl Drop for ActiveOperation<'_> {
+    fn drop(&mut self) {
+        self.0.active_operations.fetch_sub(1, Ordering::AcqRel);
+    }
+}
+
+/// A session handle bound to one alias in a [`WorkdirSessionRouter`].
+#[derive(Debug, Clone)]
+pub struct RoutedWorkdirSession {
+    state: Arc<RoutedSessionState>,
+}
+
+#[async_trait]
+impl WorkdirSession for RoutedWorkdirSession {
+    fn workdir(&self) -> &Workdir {
+        self.state.session.workdir()
+    }
+
+    fn capabilities(&self) -> WorkdirSessionCapabilities {
+        self.state.session.capabilities()
+    }
+
+    async fn authorize_scope_path(
+        &self,
+        request: WorkdirScopeAuthorizationRequest,
+    ) -> Result<(), WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.authorize_scope_path(request).await
+    }
+
+    async fn scope_rules_overlap(
+        &self,
+        request: WorkdirScopeOverlapRequest,
+    ) -> Result<bool, WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.scope_rules_overlap(request).await
+    }
+
+    async fn stat(&self, request: StatRequest) -> Result<StatResult, WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.stat(request).await
+    }
+
+    async fn read(&self, request: ReadRequest) -> Result<ReadResult, WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.read(request).await
+    }
+
+    async fn write(&self, request: WriteRequest) -> Result<WriteResult, WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.write(request).await
+    }
+
+    async fn edit(&self, request: EditRequest) -> Result<EditResult, WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.edit(request).await
+    }
+
+    async fn list(&self, request: ListRequest) -> Result<ListResult, WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.list(request).await
+    }
+
+    async fn glob(&self, request: GlobRequest) -> Result<GlobResult, WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.glob(request).await
+    }
+
+    async fn grep(&self, request: GrepRequest) -> Result<GrepResult, WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.grep(request).await
+    }
+
+    async fn start_command(&self, request: CommandRequest) -> Result<CommandHandle, WorkdirError> {
+        let _active = self.state.enter()?;
+        let handle = self.state.session.start_command(request).await?;
+        self.state
+            .active_commands
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .insert(handle.clone());
+        Ok(handle)
+    }
+
+    async fn command_status(&self, handle: CommandHandle) -> Result<CommandStatus, WorkdirError> {
+        let _active = self.state.enter()?;
+        let status = self.state.session.command_status(handle.clone()).await?;
+        self.state.mark_terminal(&handle, status);
+        Ok(status)
+    }
+
+    async fn command_output(
+        &self,
+        request: CommandOutputRequest,
+    ) -> Result<CommandOutput, WorkdirError> {
+        let _active = self.state.enter()?;
+        let handle = request.handle.clone();
+        let output = self.state.session.command_output(request).await?;
+        self.state.mark_terminal(&handle, output.status);
+        Ok(output)
+    }
+
+    async fn cancel_command(&self, handle: CommandHandle) -> Result<(), WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.cancel_command(handle.clone()).await?;
+        self.state
+            .active_commands
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .remove(&handle);
+        Ok(())
+    }
+
+    fn subscribe_command_events(&self) -> Option<broadcast::Receiver<CommandEvent>> {
+        self.state.session.subscribe_command_events()
+    }
+
+    fn command_snapshot(&self) -> Vec<CommandSnapshot> {
+        let snapshots = self.state.session.command_snapshot();
+        self.state.reconcile_terminal_commands(&snapshots);
+        snapshots
+    }
+
+    async fn close(&self) -> Result<(), WorkdirError> {
+        if self.state.is_busy() {
+            return Err(WorkdirError::Conflict(
+                "Workdir attachment has active operations or commands".to_string(),
+            ));
+        }
+        self.state.session.close().await
+    }
+}
+
+/// Worker-owned map of stable attachment aliases to provider-neutral sessions.
+#[derive(Debug, Default)]
+pub struct WorkdirSessionRouter {
+    sessions: RwLock<BTreeMap<WorkdirAttachmentAlias, Arc<RoutedSessionState>>>,
+    next_generation: AtomicU64,
+}
+
+impl WorkdirSessionRouter {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn aliases(&self) -> Vec<WorkdirAttachmentAlias> {
+        self.sessions
+            .read()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .keys()
+            .cloned()
+            .collect()
+    }
+
+    pub fn capabilities(&self) -> WorkdirSessionCapabilities {
+        self.sessions
+            .read()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .values()
+            .fold(WorkdirSessionCapabilities::EMPTY, |capabilities, state| {
+                capabilities.union(state.session.capabilities())
+            })
+    }
+
+    pub fn len(&self) -> usize {
+        self.sessions
+            .read()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    /// Resolve one model-visible target without exposing provider identity.
+    ///
+    /// Omission is accepted only for the unambiguous single-attachment case.
+    /// Every error includes the current alias snapshot so callers can recover
+    /// without consulting Workdir ids, display names, or transport metadata.
+    pub fn resolve(
+        &self,
+        target_workdir: Option<&str>,
+    ) -> Result<ResolvedWorkdirSession, WorkdirRouteError> {
+        let sessions = self
+            .sessions
+            .read()
+            .unwrap_or_else(std::sync::PoisonError::into_inner);
+        let available_aliases = sessions
+            .keys()
+            .map(|alias| alias.as_str().to_owned())
+            .collect::<Vec<_>>();
+        let selected = match target_workdir {
+            Some(target) => sessions
+                .iter()
+                .find(|(alias, _)| alias.as_str() == target)
+                .map(|(alias, state)| (alias.clone(), state.clone()))
+                .ok_or_else(|| WorkdirRouteError {
+                    code: WorkdirRouteErrorCode::UnknownTargetWorkdir,
+                    target_workdir: Some(target.to_owned()),
+                    available_aliases: available_aliases.clone(),
+                })?,
+            None if sessions.is_empty() => {
+                return Err(WorkdirRouteError {
+                    code: WorkdirRouteErrorCode::NoWorkdirAttached,
+                    target_workdir: None,
+                    available_aliases,
+                });
+            }
+            None if sessions.len() > 1 => {
+                return Err(WorkdirRouteError {
+                    code: WorkdirRouteErrorCode::TargetWorkdirRequired,
+                    target_workdir: None,
+                    available_aliases,
+                });
+            }
+            None => {
+                let (alias, state) = sessions
+                    .first_key_value()
+                    .expect("single attachment exists after cardinality checks");
+                (alias.clone(), state.clone())
+            }
+        };
+        Ok(ResolvedWorkdirSession {
+            alias: selected.0,
+            generation: selected.1.generation,
+            session: Arc::new(RoutedWorkdirSession { state: selected.1 }),
+        })
+    }
+
+    pub fn attach(
+        &self,
+        alias: WorkdirAttachmentAlias,
+        session: WorkdirSessionHandle,
+    ) -> Result<WorkdirSessionHandle, WorkdirError> {
+        let mut sessions = self.sessions.write().map_err(|_| {
+            WorkdirError::Unavailable("Workdir attachment router is poisoned".to_string())
+        })?;
+        if sessions.contains_key(&alias) {
+            return Err(WorkdirError::Conflict(format!(
+                "Workdir attachment alias `{alias}` already exists"
+            )));
+        }
+        let state = Arc::new(RoutedSessionState {
+            session,
+            generation: self.next_generation.fetch_add(1, Ordering::AcqRel),
+            detached: AtomicBool::new(false),
+            active_operations: AtomicUsize::new(0),
+            active_commands: Mutex::new(HashSet::new()),
+        });
+        sessions.insert(alias, state.clone());
+        Ok(Arc::new(RoutedWorkdirSession { state }))
+    }
+
+    pub fn session(&self, alias: &WorkdirAttachmentAlias) -> Option<WorkdirSessionHandle> {
+        self.sessions
+            .read()
+            .ok()?
+            .get(alias)
+            .cloned()
+            .map(|state| Arc::new(RoutedWorkdirSession { state }) as WorkdirSessionHandle)
+    }
+
+    /// Compatibility projection used only while filesystem tool schemas have no
+    /// `target_workdir`: exactly one attachment is unambiguous; zero or multiple
+    /// attachments expose no implicit primary.
+    pub fn only_session(&self) -> Option<WorkdirSessionHandle> {
+        let sessions = self.sessions.read().ok()?;
+        if sessions.len() != 1 {
+            return None;
+        }
+        sessions
+            .values()
+            .next()
+            .cloned()
+            .map(|state| Arc::new(RoutedWorkdirSession { state }) as WorkdirSessionHandle)
+    }
+
+    pub fn can_detach(&self, alias: &WorkdirAttachmentAlias) -> Result<(), WorkdirError> {
+        let state = self
+            .sessions
+            .read()
+            .map_err(|_| {
+                WorkdirError::Unavailable("Workdir attachment router is poisoned".to_string())
+            })?
+            .get(alias)
+            .cloned()
+            .ok_or_else(|| WorkdirError::NotFound(alias.as_str().into()))?;
+        if state.detached.load(Ordering::Acquire) {
+            return Err(WorkdirError::Unavailable(
+                "Workdir attachment is already detaching".to_string(),
+            ));
+        }
+        if state.is_busy() {
+            return Err(WorkdirError::Conflict(format!(
+                "Workdir attachment `{alias}` has active operations or commands"
+            )));
+        }
+        Ok(())
+    }
+
+    /// Atomically fence new operations before an external detach transaction begins.
+    pub async fn begin_detach(&self, alias: &WorkdirAttachmentAlias) -> Result<(), WorkdirError> {
+        let state = self
+            .sessions
+            .read()
+            .map_err(|_| {
+                WorkdirError::Unavailable("Workdir attachment router is poisoned".to_string())
+            })?
+            .get(alias)
+            .cloned()
+            .ok_or_else(|| WorkdirError::NotFound(alias.as_str().into()))?;
+        if state.detached.swap(true, Ordering::AcqRel) {
+            return Err(WorkdirError::Unavailable(
+                "Workdir attachment is already detaching".to_string(),
+            ));
+        }
+        if state.is_busy_for_detach().await {
+            state.detached.store(false, Ordering::Release);
+            return Err(WorkdirError::Conflict(format!(
+                "Workdir attachment `{alias}` has active operations or commands"
+            )));
+        }
+        Ok(())
+    }
+
+    /// Reopen a route after the external detach transaction failed before commit.
+    pub fn cancel_detach(&self, alias: &WorkdirAttachmentAlias) {
+        if let Ok(sessions) = self.sessions.read()
+            && let Some(state) = sessions.get(alias)
+        {
+            state.detached.store(false, Ordering::Release);
+        }
+    }
+
+    pub async fn finish_detach(
+        &self,
+        alias: &WorkdirAttachmentAlias,
+    ) -> Result<WorkdirSessionHandle, WorkdirError> {
+        let state = {
+            let sessions = self.sessions.read().map_err(|_| {
+                WorkdirError::Unavailable("Workdir attachment router is poisoned".to_string())
+            })?;
+            sessions
+                .get(alias)
+                .cloned()
+                .ok_or_else(|| WorkdirError::NotFound(alias.as_str().into()))?
+        };
+        if !state.detached.load(Ordering::Acquire) {
+            return Err(WorkdirError::Conflict(format!(
+                "Workdir attachment `{alias}` was not prepared for detach"
+            )));
+        }
+        if state.is_busy_for_detach().await {
+            state.detached.store(false, Ordering::Release);
+            return Err(WorkdirError::Conflict(format!(
+                "Workdir attachment `{alias}` has active operations or commands"
+            )));
+        }
+        if let Err(error) = state.session.close().await {
+            state.detached.store(false, Ordering::Release);
+            return Err(error);
+        }
+        let mut sessions = self.sessions.write().map_err(|_| {
+            WorkdirError::Unavailable("Workdir attachment router is poisoned".to_string())
+        })?;
+        if sessions
+            .get(alias)
+            .is_some_and(|current| Arc::ptr_eq(current, &state))
+        {
+            sessions.remove(alias);
+        }
+        Ok(state.session.clone())
+    }
+
+    pub async fn detach(
+        &self,
+        alias: &WorkdirAttachmentAlias,
+    ) -> Result<WorkdirSessionHandle, WorkdirError> {
+        self.begin_detach(alias).await?;
+        self.finish_detach(alias).await
+    }
+
+    /// Close every attachment during Worker shutdown or startup rollback.
+    ///
+    /// Unlike [`Self::detach`], lifecycle teardown is authoritative and delegates
+    /// cancellation or draining of active commands to each provider session.
+    pub async fn close_all(&self) -> Result<(), WorkdirError> {
+        let aliases = self.aliases();
+        for alias in aliases {
+            let state = {
+                let sessions = self.sessions.read().map_err(|_| {
+                    WorkdirError::Unavailable("Workdir attachment router is poisoned".to_string())
+                })?;
+                sessions.get(&alias).cloned()
+            };
+            let Some(state) = state else {
+                continue;
+            };
+            state.detached.store(true, Ordering::Release);
+            if let Err(error) = state.session.close().await {
+                state.detached.store(false, Ordering::Release);
+                return Err(error);
+            }
+            let mut sessions = self.sessions.write().map_err(|_| {
+                WorkdirError::Unavailable("Workdir attachment router is poisoned".to_string())
+            })?;
+            if sessions
+                .get(&alias)
+                .is_some_and(|current| Arc::ptr_eq(current, &state))
+            {
+                sessions.remove(&alias);
+            }
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::LocalWorkdirSession;
+    use manifest::Scope;
+    use tempfile::TempDir;
+
+    fn session(id: &str, dir: &TempDir) -> WorkdirSessionHandle {
+        Arc::new(LocalWorkdirSession::materialized_bound(
+            Workdir::new(id),
+            dir.path().to_path_buf(),
+            dir.path().to_path_buf(),
+            manifest::SharedScope::new(Scope::writable(dir.path()).unwrap()),
+            WorkdirSessionCapabilities::ALL,
+        ))
+    }
+
+    #[tokio::test]
+    async fn router_holds_multiple_aliases_without_implicit_primary() {
+        let left = TempDir::new().unwrap();
+        let right = TempDir::new().unwrap();
+        let router = WorkdirSessionRouter::new();
+        router
+            .attach(
+                WorkdirAttachmentAlias::new("left").unwrap(),
+                session("wd-left", &left),
+            )
+            .unwrap();
+        router
+            .attach(
+                WorkdirAttachmentAlias::new("right").unwrap(),
+                session("wd-right", &right),
+            )
+            .unwrap();
+        assert_eq!(
+            router
+                .aliases()
+                .iter()
+                .map(WorkdirAttachmentAlias::as_str)
+                .collect::<Vec<_>>(),
+            ["left", "right"]
+        );
+        assert!(router.only_session().is_none());
+        let missing = router.resolve(None).unwrap_err();
+        assert_eq!(missing.code, WorkdirRouteErrorCode::TargetWorkdirRequired);
+        assert_eq!(missing.available_aliases, ["left", "right"]);
+        assert_eq!(
+            router
+                .resolve(Some("right"))
+                .unwrap()
+                .session
+                .workdir()
+                .id()
+                .as_str(),
+            "wd-right"
+        );
+        let unknown = router.resolve(Some("display-name")).unwrap_err();
+        assert_eq!(unknown.code, WorkdirRouteErrorCode::UnknownTargetWorkdir);
+        assert_eq!(unknown.target_workdir.as_deref(), Some("display-name"));
+        assert_eq!(unknown.available_aliases, ["left", "right"]);
+        router.close_all().await.unwrap();
+    }
+
+    #[test]
+    fn empty_router_returns_structured_no_attachment_error() {
+        let error = WorkdirSessionRouter::new().resolve(None).unwrap_err();
+        assert_eq!(error.code, WorkdirRouteErrorCode::NoWorkdirAttached);
+        assert!(error.available_aliases.is_empty());
+        assert_eq!(
+            serde_json::to_value(error).unwrap(),
+            serde_json::json!({
+                "code": "no_workdir_attached",
+                "available_aliases": []
+            })
+        );
+    }
+
+    #[tokio::test]
+    async fn detach_allows_naturally_completed_command_without_final_poll() {
+        let dir = TempDir::new().unwrap();
+        let router = WorkdirSessionRouter::new();
+        let alias = WorkdirAttachmentAlias::new("checkout").unwrap();
+        let underlying = session("wd", &dir);
+        let routed = router
+            .attach(alias.clone(), Arc::clone(&underlying))
+            .unwrap();
+        let handle = routed
+            .start_command(CommandRequest {
+                command: "printf done".to_string(),
+                timeout_secs: 5,
+                output_limit: 1024,
+                cwd: None,
+                spill_dir: None,
+                tool_call_id: None,
+            })
+            .await
+            .unwrap();
+        let deadline = tokio::time::Instant::now() + std::time::Duration::from_secs(2);
+        loop {
+            let completed = underlying.command_snapshot().iter().any(|snapshot| {
+                snapshot.command_id == handle.0 && snapshot.status != CommandStatus::Running
+            });
+            if completed {
+                break;
+            }
+            assert!(tokio::time::Instant::now() < deadline);
+            tokio::time::sleep(std::time::Duration::from_millis(10)).await;
+        }
+
+        router.detach(&alias).await.unwrap();
+        assert!(router.is_empty());
+    }
+
+    #[tokio::test]
+    async fn lifecycle_close_all_closes_sessions_with_active_commands() {
+        let dir = TempDir::new().unwrap();
+        let router = WorkdirSessionRouter::new();
+        let alias = WorkdirAttachmentAlias::new("checkout").unwrap();
+        let underlying = session("wd", &dir);
+        let routed = router.attach(alias, Arc::clone(&underlying)).unwrap();
+        let handle = routed
+            .start_command(CommandRequest {
+                command: "sleep 30".to_string(),
+                timeout_secs: 60,
+                output_limit: 1024,
+                cwd: None,
+                spill_dir: None,
+                tool_call_id: None,
+            })
+            .await
+            .unwrap();
+
+        router.close_all().await.unwrap();
+
+        assert!(router.is_empty());
+        assert!(matches!(
+            underlying.command_status(handle).await,
+            Err(WorkdirError::Unavailable(_))
+        ));
+    }
+
+    #[tokio::test]
+    async fn detach_rejects_active_command_until_cancelled() {
+        let dir = TempDir::new().unwrap();
+        let router = WorkdirSessionRouter::new();
+        let alias = WorkdirAttachmentAlias::new("checkout").unwrap();
+        let routed = router.attach(alias.clone(), session("wd", &dir)).unwrap();
+        let handle = routed
+            .start_command(CommandRequest {
+                command: "sleep 30".to_string(),
+                timeout_secs: 60,
+                output_limit: 1024,
+                cwd: None,
+                spill_dir: None,
+                tool_call_id: None,
+            })
+            .await
+            .unwrap();
+        assert!(matches!(
+            router.detach(&alias).await,
+            Err(WorkdirError::Conflict(_))
+        ));
+        routed.cancel_command(handle).await.unwrap();
+        router.detach(&alias).await.unwrap();
+        assert!(router.is_empty());
+    }
+}

crates/workdir/src/scope.rs

@@ -1,4 +1,4 @@
-use std::collections::{HashMap, HashSet};
+use std::collections::{BTreeMap, HashMap, HashSet};
 use std::path::Path;
 use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
 use std::sync::{Arc, Mutex, Weak};
@@ -284,6 +284,204 @@ impl Drop for WorkdirScopeLease {
     }
 }
 
+/// Alias-keyed parent authority used to attenuate one or more Workdir
+/// attachments for an Internal SubWorker.
+#[derive(Clone)]
+pub struct WorkdirToolBrokerRouter {
+    sessions: Arc<crate::WorkdirSessionRouter>,
+    brokers: Arc<Mutex<BTreeMap<crate::WorkdirAttachmentAlias, (u64, WorkdirToolBroker)>>>,
+}
+
+impl std::fmt::Debug for WorkdirToolBrokerRouter {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        formatter
+            .debug_struct("WorkdirToolBrokerRouter")
+            .field("aliases", &self.sessions.aliases())
+            .finish_non_exhaustive()
+    }
+}
+
+impl WorkdirToolBrokerRouter {
+    pub fn from_single(
+        alias: crate::WorkdirAttachmentAlias,
+        session: WorkdirSessionHandle,
+    ) -> Result<Self, WorkdirError> {
+        let sessions = Arc::new(crate::WorkdirSessionRouter::new());
+        sessions.attach(alias, session)?;
+        Ok(Self::new(sessions))
+    }
+
+    pub fn new(sessions: Arc<crate::WorkdirSessionRouter>) -> Self {
+        Self {
+            sessions,
+            brokers: Arc::new(Mutex::new(BTreeMap::new())),
+        }
+    }
+
+    pub fn sessions(&self) -> Arc<crate::WorkdirSessionRouter> {
+        self.sessions.clone()
+    }
+
+    pub fn resolve_alias(
+        &self,
+        target_workdir: Option<&str>,
+    ) -> Result<crate::WorkdirAttachmentAlias, crate::WorkdirRouteError> {
+        self.sessions
+            .resolve(target_workdir)
+            .map(|selected| selected.alias)
+    }
+
+    fn broker(
+        &self,
+        alias: &crate::WorkdirAttachmentAlias,
+    ) -> Result<WorkdirToolBroker, WorkdirError> {
+        let selected = self
+            .sessions
+            .resolve(Some(alias.as_str()))
+            .map_err(|error| WorkdirError::InvalidArgument(error.to_string()))?;
+        let mut brokers = self.brokers.lock().map_err(|_| {
+            WorkdirError::Unavailable("Workdir tool broker router is poisoned".to_string())
+        })?;
+        if let Some((generation, broker)) = brokers.get(alias)
+            && *generation == selected.generation
+        {
+            return Ok(broker.clone());
+        }
+        let broker = WorkdirToolBroker::new(selected.session);
+        brokers.insert(alias.clone(), (selected.generation, broker.clone()));
+        Ok(broker)
+    }
+
+    pub async fn scope(
+        &self,
+        targets: Vec<(crate::WorkdirAttachmentAlias, WorkdirToolScope)>,
+    ) -> Result<WorkdirScopeLeaseSet, WorkdirError> {
+        if targets.is_empty() {
+            return Err(WorkdirError::InvalidArgument(
+                "at least one Workdir attachment scope is required".to_string(),
+            ));
+        }
+        let child_sessions = Arc::new(crate::WorkdirSessionRouter::new());
+        let mut child_brokers = BTreeMap::new();
+        let mut leases = Vec::with_capacity(targets.len());
+        for (alias, request) in targets {
+            if leases.iter().any(
+                |(existing, _): &(crate::WorkdirAttachmentAlias, WorkdirScopeLease)| {
+                    existing == &alias
+                },
+            ) {
+                for (_, lease) in &leases {
+                    let _ = lease.close().await;
+                }
+                return Err(WorkdirError::InvalidArgument(format!(
+                    "duplicate Workdir attachment scope `{alias}`"
+                )));
+            }
+            let lease = match self.broker(&alias)?.scope(request).await {
+                Ok(lease) => lease,
+                Err(error) => {
+                    for (_, lease) in &leases {
+                        let _ = lease.close().await;
+                    }
+                    return Err(error);
+                }
+            };
+            if let Err(error) = child_sessions.attach(alias.clone(), lease.tool_session()) {
+                let _ = lease.close().await;
+                for (_, existing) in &leases {
+                    let _ = existing.close().await;
+                }
+                return Err(error);
+            }
+            let child_generation = child_sessions
+                .resolve(Some(alias.as_str()))
+                .expect("newly attached child route resolves")
+                .generation;
+            child_brokers.insert(alias.clone(), (child_generation, lease.broker()));
+            leases.push((alias, lease));
+        }
+        Ok(WorkdirScopeLeaseSet {
+            broker_router: WorkdirToolBrokerRouter {
+                sessions: child_sessions,
+                brokers: Arc::new(Mutex::new(child_brokers)),
+            },
+            leases,
+        })
+    }
+}
+
+pub struct WorkdirScopeLeaseSet {
+    broker_router: WorkdirToolBrokerRouter,
+    leases: Vec<(crate::WorkdirAttachmentAlias, WorkdirScopeLease)>,
+}
+
+impl std::fmt::Debug for WorkdirScopeLeaseSet {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        formatter
+            .debug_struct("WorkdirScopeLeaseSet")
+            .field(
+                "aliases",
+                &self
+                    .leases
+                    .iter()
+                    .map(|(alias, _)| alias)
+                    .collect::<Vec<_>>(),
+            )
+            .field("active", &self.is_active())
+            .finish()
+    }
+}
+
+impl WorkdirScopeLeaseSet {
+    pub fn from_single(
+        alias: crate::WorkdirAttachmentAlias,
+        lease: WorkdirScopeLease,
+    ) -> Result<Self, WorkdirError> {
+        let sessions = Arc::new(crate::WorkdirSessionRouter::new());
+        sessions.attach(alias.clone(), lease.tool_session())?;
+        let generation = sessions
+            .resolve(Some(alias.as_str()))
+            .expect("newly attached single route resolves")
+            .generation;
+        let brokers = BTreeMap::from([(alias.clone(), (generation, lease.broker()))]);
+        Ok(Self {
+            broker_router: WorkdirToolBrokerRouter {
+                sessions,
+                brokers: Arc::new(Mutex::new(brokers)),
+            },
+            leases: vec![(alias, lease)],
+        })
+    }
+
+    pub fn broker_router(&self) -> WorkdirToolBrokerRouter {
+        self.broker_router.clone()
+    }
+
+    pub fn session_router(&self) -> Arc<crate::WorkdirSessionRouter> {
+        self.broker_router.sessions()
+    }
+
+    pub async fn close(&self) -> Result<(), WorkdirError> {
+        let mut first_error = None;
+        for (_, lease) in &self.leases {
+            if let Err(error) = lease.close().await {
+                first_error.get_or_insert(error);
+            }
+        }
+        first_error.map_or(Ok(()), Err)
+    }
+
+    pub fn is_active(&self) -> bool {
+        self.leases.iter().all(|(_, lease)| lease.is_active())
+    }
+
+    pub fn revoke(&self) {
+        for (_, lease) in &self.leases {
+            lease.revoke();
+        }
+    }
+}
+
 #[derive(Debug)]
 struct SessionValidity {
     active: AtomicBool,
@@ -2303,6 +2501,69 @@ mod tests {
         child.close().await.unwrap();
     }
 
+    #[tokio::test]
+    async fn broker_router_delegates_multiple_aliases_without_namespace_mixing() {
+        let left = TempDir::new().unwrap();
+        let right = TempDir::new().unwrap();
+        fs::write(left.path().join("same.txt"), "left").unwrap();
+        fs::write(right.path().join("same.txt"), "right").unwrap();
+        let sessions = Arc::new(crate::WorkdirSessionRouter::new());
+        sessions
+            .attach(
+                crate::WorkdirAttachmentAlias::new("left").unwrap(),
+                Arc::new(crate::LocalWorkdirSession::new(
+                    manifest::Scope::writable(left.path()).unwrap(),
+                    left.path().to_path_buf(),
+                )),
+            )
+            .unwrap();
+        sessions
+            .attach(
+                crate::WorkdirAttachmentAlias::new("right").unwrap(),
+                Arc::new(crate::LocalWorkdirSession::new(
+                    manifest::Scope::writable(right.path()).unwrap(),
+                    right.path().to_path_buf(),
+                )),
+            )
+            .unwrap();
+        let brokers = WorkdirToolBrokerRouter::new(sessions);
+        let leases = brokers
+            .scope(vec![
+                (
+                    crate::WorkdirAttachmentAlias::new("left").unwrap(),
+                    request("", WorkdirToolScopePermission::Read),
+                ),
+                (
+                    crate::WorkdirAttachmentAlias::new("right").unwrap(),
+                    request("", WorkdirToolScopePermission::Read),
+                ),
+            ])
+            .await
+            .unwrap();
+
+        let child = leases.session_router();
+        let left_content = child
+            .resolve(Some("left"))
+            .unwrap()
+            .session
+            .read(read("same.txt"))
+            .await
+            .unwrap();
+        let right_content = child
+            .resolve(Some("right"))
+            .unwrap()
+            .session
+            .read(read("same.txt"))
+            .await
+            .unwrap();
+        assert_eq!(left_content.bytes, b"left");
+        assert_eq!(right_content.bytes, b"right");
+        assert!(child.resolve(None).is_err());
+
+        leases.close().await.unwrap();
+        assert!(!leases.is_active());
+    }
+
     #[tokio::test]
     async fn closing_parent_invalidates_scoped_tools() {
         let root = TempDir::new().unwrap();

crates/workdir/src/workspace.rs

@@ -70,6 +70,9 @@ pub struct RuntimeWorkingDirectoryCleanupTarget {
 #[serde(deny_unknown_fields)]
 pub struct RuntimeWorkingDirectorySummary {
     pub working_directory_id: String,
+    /// Optional human-facing label. Never used for routing or identity.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub display_name: Option<String>,
     pub repository_id: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub creation_selector: Option<String>,
@@ -92,8 +95,6 @@ pub struct RuntimeWorkingDirectorySummary {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub cleanliness: Option<String>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub primary_worker_id: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
     pub occupied_by: Option<WorkingDirectoryOccupancy>,
 }
 
@@ -101,6 +102,9 @@ pub struct RuntimeWorkingDirectorySummary {
 #[serde(deny_unknown_fields)]
 pub struct WorkingDirectorySummary {
     pub working_directory_id: String,
+    /// Optional human-facing label. Never used for attachment routing.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub display_name: Option<String>,
     pub repository_key: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub creation_selector: Option<String>,
@@ -123,8 +127,6 @@ pub struct WorkingDirectorySummary {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub cleanliness: Option<String>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub primary_worker_id: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
     pub occupied_by: Option<WorkingDirectoryOccupancy>,
 }
 
@@ -184,8 +186,6 @@ pub struct WorkingDirectoryCurrentObservation {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub cleanliness: Option<String>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub primary_worker_id: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
     pub occupied_by: Option<WorkingDirectoryOccupancy>,
 }
 
@@ -214,6 +214,7 @@ mod tests {
     fn working_directory_summary_preserves_server_projection_wire_shape() {
         let summary = WorkingDirectorySummary {
             working_directory_id: "wd-1".to_string(),
+            display_name: Some("Checkout".to_string()),
             repository_key: "repo-1".to_string(),
             creation_selector: None,
             creation_ref: None,
@@ -226,7 +227,6 @@ mod tests {
             cleanup_target: None,
             status: WorkingDirectoryStatusKind::Active,
             cleanliness: None,
-            primary_worker_id: None,
             occupied_by: None,
         };
         let value = serde_json::to_value(summary).unwrap();
@@ -240,5 +240,7 @@ mod tests {
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct WorkspaceWorkdirSessionOperationRequest {
+    /// Worker-local attachment alias selected by the calling tool router.
+    pub target_workdir: String,
     pub operation: crate::http::WorkdirSessionOperation,
 }

crates/worker-runtime/src/catalog.rs

@@ -161,6 +161,8 @@ pub struct WorkingDirectoryRepositoryAccessRequest {
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub struct WorkingDirectoryRequest {
     pub repository: WorkingDirectoryRepository,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub display_name: Option<String>,
     #[serde(default)]
     pub materializer: MaterializerKind,
     /// Backend-assigned stable Workdir id. Runtimes use this when present so the
@@ -197,12 +199,25 @@ pub struct RepositoryRefObservation {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
-pub struct WorkingDirectoryClaim {
+pub struct WorkingDirectoryAttachmentClaim {
+    pub alias: workdir::WorkdirAttachmentAlias,
     pub working_directory_id: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub relative_cwd: Option<String>,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct WorkingDirectoryAttachmentRequest {
+    pub alias: workdir::WorkdirAttachmentAlias,
+    pub working_directory: WorkingDirectoryRequest,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct WorkingDirectoryAttachmentStatus {
+    pub alias: workdir::WorkdirAttachmentAlias,
+    pub working_directory: WorkingDirectoryStatus,
+}
+
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub struct WorkingDirectoryStatus {
     pub summary: WorkingDirectorySummary,
@@ -247,10 +262,10 @@ pub struct CreateWorkerRequest {
     pub config_bundle: Option<ConfigBundleRef>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub initial_input: Option<WorkerInput>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory_request: Option<WorkingDirectoryRequest>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory: Option<WorkingDirectoryClaim>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachment_requests: Vec<WorkingDirectoryAttachmentRequest>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachments: Vec<WorkingDirectoryAttachmentClaim>,
     /// Backend-only feature enablement. Grants still define local Runtime peers;
     /// the Workspace provider reauthorizes its dynamic set per operation.
     #[serde(default, skip_serializing_if = "is_false")]
@@ -308,8 +323,8 @@ pub struct WorkerSummary {
     pub worker_state: Option<protocol::WorkerStateSnapshot>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub workspace_id: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory: Option<WorkingDirectoryStatus>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachments: Vec<WorkingDirectoryAttachmentStatus>,
     pub profile: ProfileSelector,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub display_name: Option<String>,
@@ -333,8 +348,8 @@ pub struct WorkerDetail {
     pub worker_state: Option<protocol::WorkerStateSnapshot>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub workspace_id: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory: Option<WorkingDirectoryStatus>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachments: Vec<WorkingDirectoryAttachmentStatus>,
     pub profile: ProfileSelector,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub display_name: Option<String>,

crates/worker-runtime/src/execution.rs

@@ -12,6 +12,7 @@ use crate::observation::WorkerObservationEvent;
 use crate::working_directory::{WorkingDirectoryBinding, WorkingDirectoryDiagnostic};
 use protocol::{Method, UploadedFileRef};
 use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
 use std::fmt;
 use std::sync::Arc;
 use workdir::WorkdirSessionHandle;
@@ -246,7 +247,7 @@ pub struct WorkerExecutionSpawnRequest {
     pub request: crate::catalog::CreateWorkerRequest,
     pub workspace_scope: Option<crate::runtime::RuntimeWorkspaceScope>,
     pub context: WorkerExecutionContext,
-    pub working_directory: Option<WorkingDirectoryBinding>,
+    pub workdir_attachments: BTreeMap<workdir::WorkdirAttachmentAlias, WorkingDirectoryBinding>,
     pub config_bundle: Option<ConfigBundle>,
 }
 
@@ -257,8 +258,8 @@ pub struct WorkerExecutionRestoreRequest {
     pub request: crate::catalog::CreateWorkerRequest,
     pub workspace_scope: Option<crate::runtime::RuntimeWorkspaceScope>,
     pub context: WorkerExecutionContext,
-    pub previous_working_directory: Option<WorkingDirectoryStatus>,
-    pub working_directory: Option<WorkingDirectoryBinding>,
+    pub previous_workdir_attachments: Vec<crate::catalog::WorkingDirectoryAttachmentStatus>,
+    pub workdir_attachments: BTreeMap<workdir::WorkdirAttachmentAlias, WorkingDirectoryBinding>,
     pub config_bundle: Option<ConfigBundle>,
 }
 
@@ -284,7 +285,7 @@ pub enum WorkerExecutionSpawnResult {
     Connected {
         handle: WorkerExecutionHandle,
         worker_state: protocol::WorkerStateSnapshot,
-        working_directory: Option<WorkingDirectoryStatus>,
+        workdir_attachments: Vec<crate::catalog::WorkingDirectoryAttachmentStatus>,
     },
     /// A read-only preflight rejected the operation before live work started.
     Rejected(WorkerExecutionResult),
@@ -297,7 +298,7 @@ pub enum WorkerExecutionSpawnResult {
         result: WorkerExecutionResult,
         handle: Option<WorkerExecutionHandle>,
         worker_state: Option<protocol::WorkerStateSnapshot>,
-        working_directory: Option<WorkingDirectoryStatus>,
+        workdir_attachments: Vec<crate::catalog::WorkingDirectoryAttachmentStatus>,
     },
     /// Legacy spawn failure. Restore implementations must use `RolledBack` or
     /// `ReconciliationRequired` after crossing their live side-effect boundary.
@@ -308,12 +309,12 @@ impl WorkerExecutionSpawnResult {
     pub fn connected(
         handle: WorkerExecutionHandle,
         worker_state: protocol::WorkerStateSnapshot,
-        working_directory: Option<WorkingDirectoryStatus>,
+        workdir_attachments: Vec<crate::catalog::WorkingDirectoryAttachmentStatus>,
     ) -> Self {
         Self::Connected {
             handle,
             worker_state,
-            working_directory,
+            workdir_attachments,
         }
     }
 }

crates/worker-runtime/src/fs_store.rs

@@ -1,6 +1,7 @@
 use crate::catalog::{
     ConfigBundleRef, CreateWorkerRequest, ProfileSelector, WorkerRestoreIntent, WorkerStatus,
-    WorkingDirectoryStatus,
+    WorkingDirectoryAttachmentClaim, WorkingDirectoryAttachmentRequest,
+    WorkingDirectoryAttachmentStatus, WorkingDirectoryRequest,
 };
 use crate::config_bundle::ConfigBundle;
 use crate::diagnostics::{DiagnosticSeverity, RuntimeDiagnostic};
@@ -442,7 +443,7 @@ pub(crate) struct PersistedWorkerRecord {
     pub(crate) status: WorkerStatus,
     pub(crate) execution_state: PersistedWorkerExecutionState,
     pub(crate) workspace_id: Option<String>,
-    pub(crate) working_directory: Option<WorkingDirectoryStatus>,
+    pub(crate) workdir_attachments: Vec<WorkingDirectoryAttachmentStatus>,
 }
 
 fn runtime_io_error(operation: &'static str, path: &Path, source: std::io::Error) -> RuntimeError {
@@ -1685,11 +1686,18 @@ struct WorkerIdentityRecord {
     status: WorkerStatus,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     workspace_id: Option<String>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    working_directory: Option<WorkingDirectoryStatus>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    workdir_attachments: Vec<WorkingDirectoryAttachmentStatus>,
+    /// Schema-v8 compatibility input. New records serialize only `workdir_attachments`.
+    #[serde(
+        default,
+        rename = "working_directory",
+        skip_serializing_if = "Option::is_none"
+    )]
+    legacy_working_directory: Option<crate::catalog::WorkingDirectoryStatus>,
 }
 
-#[derive(Clone, Debug, Serialize, Deserialize)]
+#[derive(Clone, Debug, Serialize)]
 #[serde(deny_unknown_fields)]
 struct WorkerExecutionRecord {
     schema_version: u32,
@@ -1699,6 +1707,72 @@ struct WorkerExecutionRecord {
     restore_intent: WorkerRestoreIntent,
 }
 
+#[derive(Deserialize)]
+#[serde(deny_unknown_fields)]
+struct RawWorkerExecutionRecord {
+    schema_version: u32,
+    request: serde_json::Value,
+    #[serde(default)]
+    binding: Option<PersistedWorkerExecutionBinding>,
+    restore_intent: WorkerRestoreIntent,
+}
+
+#[derive(Deserialize)]
+#[serde(deny_unknown_fields)]
+struct LegacyWorkingDirectoryClaim {
+    working_directory_id: String,
+    #[serde(default)]
+    relative_cwd: Option<String>,
+}
+
+impl<'de> Deserialize<'de> for WorkerExecutionRecord {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let raw = RawWorkerExecutionRecord::deserialize(deserializer)?;
+        let mut request_value = raw.request;
+        let request_object = request_value
+            .as_object_mut()
+            .ok_or_else(|| serde::de::Error::custom("Worker create request must be an object"))?;
+        let legacy_request = request_object.remove("working_directory_request");
+        let legacy_claim = request_object.remove("working_directory");
+        let mut request: CreateWorkerRequest =
+            serde_json::from_value(request_value).map_err(serde::de::Error::custom)?;
+        if request.workdir_attachment_requests.is_empty() && request.workdir_attachments.is_empty()
+        {
+            let alias = workdir::WorkdirAttachmentAlias::new("workdir")
+                .expect("static compatibility alias is valid");
+            if let Some(value) = legacy_request.filter(|value| !value.is_null()) {
+                let working_directory: WorkingDirectoryRequest =
+                    serde_json::from_value(value).map_err(serde::de::Error::custom)?;
+                request
+                    .workdir_attachment_requests
+                    .push(WorkingDirectoryAttachmentRequest {
+                        alias,
+                        working_directory,
+                    });
+            } else if let Some(value) = legacy_claim.filter(|value| !value.is_null()) {
+                let claim: LegacyWorkingDirectoryClaim =
+                    serde_json::from_value(value).map_err(serde::de::Error::custom)?;
+                request
+                    .workdir_attachments
+                    .push(WorkingDirectoryAttachmentClaim {
+                        alias,
+                        working_directory_id: claim.working_directory_id,
+                        relative_cwd: claim.relative_cwd,
+                    });
+            }
+        }
+        Ok(Self {
+            schema_version: raw.schema_version,
+            request,
+            binding: raw.binding,
+            restore_intent: raw.restore_intent,
+        })
+    }
+}
+
 impl WorkerIdentityRecord {
     fn from_persisted(worker: &PersistedWorkerRecord) -> Self {
         Self {
@@ -1712,7 +1786,8 @@ impl WorkerIdentityRecord {
             created_at_ms: worker.created_at_ms,
             status: worker.status,
             workspace_id: worker.workspace_id.clone(),
-            working_directory: worker.working_directory.clone(),
+            workdir_attachments: worker.workdir_attachments.clone(),
+            legacy_working_directory: None,
         }
     }
 
@@ -1760,6 +1835,19 @@ impl WorkerIdentityRecord {
         self,
         execution_state: PersistedWorkerExecutionState,
     ) -> PersistedWorkerRecord {
+        let workdir_attachments = if self.workdir_attachments.is_empty() {
+            self.legacy_working_directory
+                .map(|working_directory| {
+                    vec![WorkingDirectoryAttachmentStatus {
+                        alias: workdir::WorkdirAttachmentAlias::new("workdir")
+                            .expect("static compatibility alias is valid"),
+                        working_directory,
+                    }]
+                })
+                .unwrap_or_default()
+        } else {
+            self.workdir_attachments
+        };
         PersistedWorkerRecord {
             worker_ref: self.worker_ref,
             worker_id: self.worker_id,
@@ -1771,7 +1859,7 @@ impl WorkerIdentityRecord {
             status: self.status,
             execution_state,
             workspace_id: self.workspace_id,
-            working_directory: self.working_directory,
+            workdir_attachments,
         }
     }
 }
@@ -2215,6 +2303,72 @@ mod tests {
         document
     }
 
+    #[test]
+    fn schema_v8_singular_workdir_fields_normalize_to_one_attachment() {
+        let worker_id = WorkerId::now_v7();
+        let workdir_status = serde_json::json!({
+            "summary": {
+                "working_directory_id": "wd-legacy",
+                "repository_id": "repo",
+                "materializer_kind": "runtime_git_clone",
+                "status": "active"
+            }
+        });
+        let identity: WorkerIdentityRecord = serde_json::from_value(serde_json::json!({
+            "schema_version": SCHEMA_VERSION,
+            "worker_ref": { "worker_id": worker_id },
+            "worker_id": worker_id,
+            "profile": { "kind": "builtin", "value": "builtin:coder" },
+            "display_name": null,
+            "profile_source": {
+                "id": "archive-1",
+                "digest": "sha256:archive",
+                "size_bytes": 0,
+                "source_graph": {
+                    "source_count": 0,
+                    "total_source_bytes": 0,
+                    "entrypoints": {},
+                    "import_count": 0
+                }
+            },
+            "config_bundle": null,
+            "status": "stopped",
+            "working_directory": workdir_status
+        }))
+        .unwrap();
+        let persisted = identity.into_persisted(PersistedWorkerExecutionState::Unavailable);
+        assert_eq!(persisted.workdir_attachments.len(), 1);
+        assert_eq!(persisted.workdir_attachments[0].alias.as_str(), "workdir");
+        assert_eq!(
+            persisted.workdir_attachments[0]
+                .working_directory
+                .summary
+                .working_directory_id,
+            "wd-legacy"
+        );
+
+        let mut request = schema_v7_worker_document(worker_id)["request"].clone();
+        request["working_directory"] = serde_json::json!({
+            "working_directory_id": "wd-legacy",
+            "relative_cwd": "crates/yoi"
+        });
+        let execution: WorkerExecutionRecord = serde_json::from_value(serde_json::json!({
+            "schema_version": SCHEMA_VERSION,
+            "request": request,
+            "binding": null,
+            "restore_intent": "explicit"
+        }))
+        .unwrap();
+        assert!(execution.request.workdir_attachment_requests.is_empty());
+        assert_eq!(execution.request.workdir_attachments.len(), 1);
+        let attachment = &execution.request.workdir_attachments[0];
+        assert_eq!(attachment.alias.as_str(), "workdir");
+        assert_eq!(attachment.working_directory_id, "wd-legacy");
+        assert_eq!(attachment.relative_cwd.as_deref(), Some("crates/yoi"));
+        let serialized = serde_json::to_value(execution).unwrap();
+        assert!(serialized["request"].get("working_directory").is_none());
+    }
+
     #[test]
     fn startup_recovers_staging_created_before_source_backup() {
         let temp = tempfile::tempdir().unwrap();

crates/worker-runtime/src/http_server.rs

@@ -2282,7 +2282,11 @@ fn required_runtime_permission(method: &Method, path: &str) -> Option<&'static s
     if path.ends_with("/workspace-api") {
         return Some("workers:create");
     }
-    if path.ends_with("/input") || path.ends_with("/restore") || path.contains("/attachments") {
+    if path.ends_with("/input")
+        || path.ends_with("/restore")
+        || path.contains("/attachments")
+        || path.contains("/workdir-attachments")
+    {
         return Some("workers:input");
     }
     if path.ends_with("/stop") || path.ends_with("/cancel") {
@@ -3072,8 +3076,8 @@ mod tests {
                 digest: bundle.metadata.digest,
             }),
             initial_input: None,
-            working_directory_request: None,
-            working_directory: None,
+            workdir_attachment_requests: Vec::new(),
+            workdir_attachments: Vec::new(),
             worker_observation_enabled: false,
             worker_observation_grants: Vec::new(),
             workspace_api: None,
@@ -3319,10 +3323,16 @@ mod tests {
                 worker_state: protocol::WorkerStateSnapshot {
                     ..protocol::WorkerStatus::Idle.into()
                 },
-                working_directory: request
-                    .working_directory
-                    .as_ref()
-                    .map(|binding| binding.status()),
+                workdir_attachments: request
+                    .workdir_attachments
+                    .iter()
+                    .map(
+                        |(alias, binding)| crate::catalog::WorkingDirectoryAttachmentStatus {
+                            alias: alias.clone(),
+                            working_directory: binding.status(),
+                        },
+                    )
+                    .collect(),
             }
         }
 
@@ -3335,7 +3345,7 @@ mod tests {
                 worker_state: protocol::WorkerStateSnapshot {
                     ..protocol::WorkerStatus::Idle.into()
                 },
-                working_directory: request.previous_working_directory,
+                workdir_attachments: request.previous_workdir_attachments,
             }
         }
 
@@ -3907,10 +3917,16 @@ mod ws_tests {
                 worker_state: protocol::WorkerStateSnapshot {
                     ..protocol::WorkerStatus::Idle.into()
                 },
-                working_directory: request
-                    .working_directory
-                    .as_ref()
-                    .map(|binding| binding.status()),
+                workdir_attachments: request
+                    .workdir_attachments
+                    .iter()
+                    .map(
+                        |(alias, binding)| crate::catalog::WorkingDirectoryAttachmentStatus {
+                            alias: alias.clone(),
+                            working_directory: binding.status(),
+                        },
+                    )
+                    .collect(),
             }
         }
 
@@ -4020,8 +4036,8 @@ mod ws_tests {
                 digest: bundle.metadata.digest,
             }),
             initial_input: None,
-            working_directory_request: None,
-            working_directory: None,
+            workdir_attachment_requests: Vec::new(),
+            workdir_attachments: Vec::new(),
             worker_observation_enabled: false,
             worker_observation_grants: Vec::new(),
             workspace_api: None,

crates/worker-runtime/src/http_server/runtime_management_api.rs

@@ -423,6 +423,31 @@ impl runtime_api::RuntimeApi for RuntimeManagementApi {
         Ok(runtime_api::WorkerResponse { worker })
     }
 
+    async fn replace_worker_workdir_attachments(
+        &self,
+        worker_id: String,
+        value: runtime_api::WorkerWorkdirAttachmentsRequest,
+    ) -> Result<runtime_api::WorkerResponse, runtime_api::RuntimeApiError> {
+        let attachments = request(value.workdir_attachments)?;
+        let worker_ref = worker_ref_for(&self.state.runtime, worker_id).map_err(api_error)?;
+        let worker = match auth_workspace_scope(&self.state, auth_extension().as_ref())
+            .map_err(api_error)?
+        {
+            Some(scope) => self
+                .state
+                .runtime
+                .replace_worker_workdir_attachments_scoped(&scope, &worker_ref, attachments),
+            None => self
+                .state
+                .runtime
+                .replace_worker_workdir_attachments(&worker_ref, attachments),
+        }
+        .map_err(RuntimeHttpRestError::runtime)
+        .map_err(api_error)?;
+        let worker = response(worker)?;
+        Ok(runtime_api::WorkerResponse { worker })
+    }
+
     async fn complete_worker_arguments(
         &self,
         worker_id: String,

crates/worker-runtime/src/runtime.rs

@@ -1,7 +1,8 @@
 use crate::catalog::{
     ConfigBundleRef, CreateWorkerRequest, ProfileSelector, ProfileSourceArchiveSource,
     RepositoryRefObservation, RepositoryRefObservationRequest, WorkerDetail, WorkerLifecycleAck,
-    WorkerRestoreIntent, WorkerStatus, WorkerSummary, WorkingDirectoryRepositoryAccessRequest,
+    WorkerRestoreIntent, WorkerStatus, WorkerSummary, WorkingDirectoryAttachmentClaim,
+    WorkingDirectoryAttachmentStatus, WorkingDirectoryRepositoryAccessRequest,
     WorkingDirectoryRequest, WorkingDirectoryStatus as CatalogWorkingDirectoryStatus,
     WorkspaceApiRef,
 };
@@ -43,7 +44,7 @@ use crate::retention::{
 use protocol::subscription::{
     EventSubscriptionSelector, SubscriptionEventPayload, SubscriptionSnapshot,
     SubscriptionValidationError, SubscriptionWorkdirId, SubscriptionWorker, SubscriptionWorkerId,
-    SubscriptionWorkerState,
+    SubscriptionWorkerState, SubscriptionWorkerWorkdirAttachment,
 };
 use protocol::{Event, Method};
 use server_api::WorkerRestoreState;
@@ -729,8 +730,9 @@ impl Runtime {
                     .get(&worker_ref.worker_id)
                     .is_some_and(|worker| {
                         worker.belongs_to_workspace(&scope.workspace_id)
-                            && worker.working_directory.as_ref().is_some_and(|status| {
-                                status.summary.working_directory_id == working_directory_id
+                            && worker.workdir_attachments.iter().any(|attachment| {
+                                attachment.working_directory.summary.working_directory_id
+                                    == working_directory_id
                             })
                     });
                 if !owns_workdir {
@@ -764,7 +766,7 @@ impl Runtime {
         let backend = {
             let state = self.lock()?;
             state.ensure_running()?;
-            if let Some(worker_id) = state.primary_worker_id_for_workdir(working_directory_id) {
+            if let Some(worker_id) = state.worker_id_for_workdir(working_directory_id) {
                 return Err(RuntimeError::InvalidRequest(format!(
                     "working directory {working_directory_id} is assigned to worker {worker_id}"
                 )));
@@ -792,12 +794,8 @@ impl Runtime {
 
     fn annotate_working_directory_status(
         &self,
-        mut status: CatalogWorkingDirectoryStatus,
+        status: CatalogWorkingDirectoryStatus,
     ) -> Result<CatalogWorkingDirectoryStatus, RuntimeError> {
-        let state = self.lock()?;
-        status.summary.primary_worker_id = state
-            .primary_worker_id_for_workdir(status.summary.working_directory_id.as_str())
-            .map(|worker_id| worker_id.to_string());
         Ok(status)
     }
 
@@ -1023,10 +1021,8 @@ impl Runtime {
                 return Ok(existing.detail());
             }
             state.validate_worker_config_boundary(&request)?;
-            if let Some(working_directory_id) = requested_primary_workdir_id(&request) {
-                if let Some(owner_worker_id) =
-                    state.primary_worker_id_for_workdir(working_directory_id)
-                {
+            for working_directory_id in requested_workdir_ids(&request) {
+                if let Some(owner_worker_id) = state.worker_id_for_workdir(working_directory_id) {
                     return Err(RuntimeError::InvalidRequest(format!(
                         "working directory {working_directory_id} is already assigned to worker {owner_worker_id}"
                     )));
@@ -1064,7 +1060,7 @@ impl Runtime {
                 execution_metadata_available: true,
                 execution_bound: true,
                 restore_intent: WorkerRestoreIntent::Explicit,
-                working_directory: None,
+                workdir_attachments: Vec::new(),
                 execution_handle: None,
                 internal_workers: InternalWorkerActivityProjection::default(),
             };
@@ -1076,19 +1072,19 @@ impl Runtime {
                 request,
                 workspace_scope: scope.cloned(),
                 context: self.execution_context(worker_ref.clone()),
-                working_directory: None,
+                workdir_attachments: BTreeMap::new(),
                 config_bundle,
             };
             (backend, worker_ref, spawn_request)
         };
 
         let spawn_result = backend.spawn_worker(spawn_request);
-        let (handle, initial_worker_state, working_directory) = match spawn_result {
+        let (handle, initial_worker_state, workdir_attachments) = match spawn_result {
             WorkerExecutionSpawnResult::Connected {
                 handle,
                 worker_state,
-                working_directory,
-            } => (handle, worker_state, working_directory),
+                workdir_attachments,
+            } => (handle, worker_state, workdir_attachments),
             WorkerExecutionSpawnResult::Rejected(result)
             | WorkerExecutionSpawnResult::RolledBack(result)
             | WorkerExecutionSpawnResult::Errored(result) => {
@@ -1101,8 +1097,30 @@ impl Runtime {
                     result,
                 });
             }
-            WorkerExecutionSpawnResult::ReconciliationRequired { result, .. } => {
-                self.rollback_failed_create(&worker_ref)?;
+            WorkerExecutionSpawnResult::ReconciliationRequired {
+                result,
+                handle,
+                worker_state,
+                workdir_attachments,
+            } => {
+                let retain_result =
+                    if let (Some(handle), Some(worker_state)) = (handle, worker_state) {
+                        self.retain_restore_execution_evidence(
+                            &worker_ref,
+                            handle,
+                            worker_state,
+                            workdir_attachments,
+                        )
+                    } else {
+                        self.retain_create_reconciliation_pending(&worker_ref, workdir_attachments)
+                    };
+                if let Err(error) = retain_result {
+                    tracing::error!(
+                        worker_id = %worker_ref.worker_id,
+                        %error,
+                        "failed to persist Worker create reconciliation evidence"
+                    );
+                }
                 return Err(RuntimeError::WorkerExecutionRejected {
                     worker_id: worker_ref.worker_id.clone(),
                     operation: result.operation,
@@ -1160,7 +1178,7 @@ impl Runtime {
                 &worker_ref,
                 handle.clone(),
                 initial_worker_state.clone(),
-                working_directory,
+                workdir_attachments,
                 dispatch_result,
             ) {
                 Ok(detail) => detail,
@@ -1179,7 +1197,7 @@ impl Runtime {
                 &worker_ref,
                 handle.clone(),
                 initial_worker_state,
-                working_directory,
+                workdir_attachments,
                 WorkerExecutionResult::accepted(WorkerExecutionOperation::Spawn),
             ) {
                 Ok(detail) => Ok(detail),
@@ -1425,6 +1443,119 @@ impl Runtime {
         Ok(state.worker(worker_ref)?.detail())
     }
 
+    pub fn replace_worker_workdir_attachments_scoped(
+        &self,
+        scope: &RuntimeWorkspaceScope,
+        worker_ref: &WorkerRef,
+        attachments: Vec<WorkingDirectoryAttachmentClaim>,
+    ) -> Result<WorkerDetail, RuntimeError> {
+        self.ensure_worker_in_workspace(scope, worker_ref)?;
+        self.replace_worker_workdir_attachments(worker_ref, attachments)
+    }
+
+    /// Persist the exact current attachment set used by live mutation and future restore.
+    pub fn replace_worker_workdir_attachments(
+        &self,
+        worker_ref: &WorkerRef,
+        mut attachments: Vec<WorkingDirectoryAttachmentClaim>,
+    ) -> Result<WorkerDetail, RuntimeError> {
+        let operation_lock = self.worker_operation_lock(worker_ref.worker_id)?;
+        let _operation_guard = operation_lock
+            .lock()
+            .map_err(|_| RuntimeError::StatePoisoned)?;
+
+        let backend = {
+            let state = self.lock()?;
+            let worker = state.worker(worker_ref)?;
+            if worker.execution_handle.is_none() || !worker.status.is_active() {
+                return Err(RuntimeError::WorkerExecutionUnavailable {
+                    worker_id: worker.worker_id,
+                    message: "Workdir attachments can only be changed for a live Worker"
+                        .to_string(),
+                });
+            }
+            let request = worker.request.as_ref().ok_or_else(|| {
+                RuntimeError::WorkerExecutionUnavailable {
+                    worker_id: worker.worker_id,
+                    message: "persisted Worker restore request is unavailable".to_string(),
+                }
+            })?;
+            for attachment in &mut attachments {
+                if attachment.relative_cwd.is_none()
+                    && let Some(previous) = request.workdir_attachments.iter().find(|previous| {
+                        previous.alias == attachment.alias
+                            && previous.working_directory_id == attachment.working_directory_id
+                    })
+                {
+                    attachment.relative_cwd = previous.relative_cwd.clone();
+                }
+            }
+            let mut candidate = request.clone();
+            candidate.workdir_attachment_requests.clear();
+            candidate.workdir_attachments = attachments.clone();
+            validate_create_worker_request(&candidate)?;
+            state.execution_backend.clone().ok_or_else(|| {
+                RuntimeError::ExecutionBackendUnavailable {
+                    message: "Workdir attachment mutation requires an execution backend"
+                        .to_string(),
+                }
+            })?
+        };
+
+        let statuses = attachments
+            .iter()
+            .map(|attachment| {
+                backend
+                    .working_directory(&attachment.working_directory_id)
+                    .map(|working_directory| WorkingDirectoryAttachmentStatus {
+                        alias: attachment.alias.clone(),
+                        working_directory,
+                    })
+                    .map_err(RuntimeError::from)
+            })
+            .collect::<Result<Vec<_>, RuntimeError>>()?;
+        if let Some(inactive) = statuses.iter().find(|attachment| {
+            attachment.working_directory.summary.status
+                != workdir::workspace::WorkingDirectoryStatusKind::Active
+        }) {
+            return Err(RuntimeError::InvalidRequest(format!(
+                "working directory {} is not active ({})",
+                inactive.working_directory.summary.working_directory_id,
+                inactive.working_directory.summary.status
+            )));
+        }
+
+        let mut state = self.lock()?;
+        for attachment in &attachments {
+            if let Some(owner_worker_id) =
+                state.worker_id_for_workdir(&attachment.working_directory_id)
+                && owner_worker_id != worker_ref.worker_id
+            {
+                return Err(RuntimeError::InvalidRequest(format!(
+                    "working directory {} is already assigned to worker {owner_worker_id}",
+                    attachment.working_directory_id
+                )));
+            }
+        }
+        let previous = state.worker(worker_ref)?.clone();
+        {
+            let worker = state.worker_mut(worker_ref)?;
+            let request = worker
+                .request
+                .as_mut()
+                .expect("restore request checked above");
+            request.workdir_attachment_requests.clear();
+            request.workdir_attachments = attachments;
+            worker.workdir_attachments = statuses;
+        }
+        if let Err(error) = state.persist_worker(&worker_ref.worker_id) {
+            state.workers.insert(worker_ref.worker_id, previous);
+            return Err(error);
+        }
+        state.publish_worker_upsert(worker_ref.worker_id)?;
+        Ok(state.worker(worker_ref)?.detail())
+    }
+
     /// Observe a Worker's live protocol availability or its retained Session.
     /// The same lifecycle lock used by stop/restore fences the decision and read.
     pub fn worker_session_scoped(
@@ -1570,8 +1701,8 @@ impl Runtime {
                 request: worker_request,
                 workspace_scope,
                 context: self.execution_context(worker_ref.clone()),
-                previous_working_directory: worker.working_directory.clone(),
-                working_directory: None,
+                previous_workdir_attachments: worker.workdir_attachments.clone(),
+                workdir_attachments: BTreeMap::new(),
                 config_bundle: None,
             };
             (backend, request)
@@ -1589,14 +1720,14 @@ impl Runtime {
             WorkerExecutionSpawnResult::Connected {
                 handle,
                 worker_state,
-                working_directory,
+                workdir_attachments,
             } => {
                 let commit = self.commit_restored_worker_execution(
                     worker_ref,
                     handle.clone(),
                     worker_state.clone(),
                     WorkerStatus::Idle,
-                    working_directory.clone(),
+                    workdir_attachments.clone(),
                 );
                 match commit {
                     Ok(worker) => Ok(RuntimeWorkerRestoreResult::accepted(worker)),
@@ -1625,7 +1756,7 @@ impl Runtime {
                                     worker_ref,
                                     handle,
                                     worker_state,
-                                    working_directory,
+                                    workdir_attachments,
                                 ) {
                                     tracing::error!(
                                         worker_id = %worker_ref.worker_id,
@@ -1663,14 +1794,14 @@ impl Runtime {
                 result: _result,
                 handle,
                 worker_state,
-                working_directory,
+                workdir_attachments,
             } => {
                 if let (Some(handle), Some(worker_state)) = (handle, worker_state) {
                     if let Err(retain_error) = self.retain_restore_execution_evidence(
                         worker_ref,
                         handle,
                         worker_state,
-                        working_directory,
+                        workdir_attachments,
                     ) {
                         tracing::error!(
                             worker_id = %worker_ref.worker_id,
@@ -2079,7 +2210,7 @@ impl Runtime {
         worker_ref: &WorkerRef,
         handle: WorkerExecutionHandle,
         initial_worker_state: protocol::WorkerStateSnapshot,
-        working_directory: Option<CatalogWorkingDirectoryStatus>,
+        workdir_attachments: Vec<crate::catalog::WorkingDirectoryAttachmentStatus>,
         result: WorkerExecutionResult,
     ) -> Result<WorkerDetail, RuntimeError> {
         let mut state = self.lock()?;
@@ -2094,7 +2225,7 @@ impl Runtime {
                 let _ = worker.apply_worker_state(snapshot);
             }
             worker.restore_intent = restore_intent_for_status(worker.status);
-            worker.working_directory = working_directory;
+            worker.workdir_attachments = workdir_attachments;
             worker.detail()
         };
         state.publish_worker_upsert(worker_ref.worker_id)?;
@@ -2367,9 +2498,13 @@ impl Runtime {
             state.ensure_running()?;
             state.ensure_worker_ref(worker_ref)?;
             let worker = state.worker(worker_ref)?;
-            if worker.execution_handle.is_some() && worker.status.is_active() {
+            if worker.status.is_active()
+                && (worker.execution_handle.is_some()
+                    || (!worker.execution_metadata_available
+                        && !worker.workdir_attachments.is_empty()))
+            {
                 return Err(RuntimeError::InvalidRequest(format!(
-                    "worker {} is running and must be stopped before deletion",
+                    "worker {} is active or requires reconciliation and must be stopped before deletion",
                     worker_ref.worker_id
                 )));
             }
@@ -2398,9 +2533,12 @@ impl Runtime {
         state.ensure_running()?;
         state.ensure_worker_ref(worker_ref)?;
         let worker = state.worker(worker_ref)?;
-        if worker.execution_handle.is_some() && worker.status.is_active() {
+        if worker.status.is_active()
+            && (worker.execution_handle.is_some()
+                || (!worker.execution_metadata_available && !worker.workdir_attachments.is_empty()))
+        {
             return Err(RuntimeError::InvalidRequest(format!(
-                "worker {} became active before deletion",
+                "worker {} became active or reconciliation-required before deletion",
                 worker_ref.worker_id
             )));
         }
@@ -2662,7 +2800,7 @@ impl Runtime {
         handle: WorkerExecutionHandle,
         worker_state: protocol::WorkerStateSnapshot,
         status: WorkerStatus,
-        working_directory: Option<CatalogWorkingDirectoryStatus>,
+        workdir_attachments: Vec<crate::catalog::WorkingDirectoryAttachmentStatus>,
     ) -> Result<WorkerDetail, RuntimeError> {
         let mut state = self.lock()?;
         state.ensure_worker_ref(worker_ref)?;
@@ -2679,7 +2817,7 @@ impl Runtime {
         candidate.status = status;
         let _ = candidate.apply_worker_state(&worker_state);
         candidate.restore_intent = restore_intent_for_status(candidate.status);
-        candidate.working_directory = working_directory;
+        candidate.workdir_attachments = workdir_attachments;
 
         // Validate the exact subscription projection before persistence. The
         // subsequent publish uses the same pure projection while the Worker
@@ -2708,7 +2846,7 @@ impl Runtime {
         worker_ref: &WorkerRef,
         handle: WorkerExecutionHandle,
         worker_state: protocol::WorkerStateSnapshot,
-        working_directory: Option<CatalogWorkingDirectoryStatus>,
+        workdir_attachments: Vec<crate::catalog::WorkingDirectoryAttachmentStatus>,
     ) -> Result<(), RuntimeError> {
         let mut state = self.lock()?;
         let mut candidate = state.worker(worker_ref)?.clone();
@@ -2718,7 +2856,26 @@ impl Runtime {
         candidate.status = WorkerStatus::Idle;
         let _ = candidate.apply_worker_state(&worker_state);
         candidate.restore_intent = WorkerRestoreIntent::Automatic;
-        candidate.working_directory = working_directory;
+        candidate.workdir_attachments = workdir_attachments;
+        state.workers.insert(worker_ref.worker_id, candidate);
+        state.publish_worker_upsert(worker_ref.worker_id)?;
+        state.persist_worker(&worker_ref.worker_id)?;
+        Ok(())
+    }
+
+    fn retain_create_reconciliation_pending(
+        &self,
+        worker_ref: &WorkerRef,
+        workdir_attachments: Vec<crate::catalog::WorkingDirectoryAttachmentStatus>,
+    ) -> Result<(), RuntimeError> {
+        let mut state = self.lock()?;
+        let mut candidate = state.worker(worker_ref)?.clone();
+        candidate.execution_handle = None;
+        candidate.execution_metadata_available = false;
+        candidate.execution_bound = true;
+        candidate.status = WorkerStatus::Idle;
+        candidate.restore_intent = WorkerRestoreIntent::Explicit;
+        candidate.workdir_attachments = workdir_attachments;
         state.workers.insert(worker_ref.worker_id, candidate);
         state.publish_worker_upsert(worker_ref.worker_id)?;
         state.persist_worker(&worker_ref.worker_id)?;
@@ -3078,7 +3235,7 @@ impl RuntimeState {
                     execution_metadata_available,
                     execution_bound,
                     restore_intent,
-                    working_directory: worker.working_directory,
+                    workdir_attachments: worker.workdir_attachments,
                     execution_handle: None,
                     internal_workers: InternalWorkerActivityProjection::default(),
                 },
@@ -3394,18 +3551,25 @@ impl RuntimeState {
     ) -> Result<SubscriptionWorker, RuntimeError> {
         let worker_id = SubscriptionWorkerId::new(worker.worker_id.to_string())
             .map_err(subscription_validation_error)?;
-        let repository_id = worker
-            .working_directory
-            .as_ref()
-            .map(|working_directory| working_directory.summary.repository_id.clone());
-        let working_directory_id = worker
-            .working_directory
-            .as_ref()
-            .map(|working_directory| {
-                SubscriptionWorkdirId::new(working_directory.summary.working_directory_id.clone())
-                    .map_err(subscription_validation_error)
+        let workdir_attachments = worker
+            .workdir_attachments
+            .iter()
+            .map(|attachment| {
+                Ok(SubscriptionWorkerWorkdirAttachment {
+                    alias: attachment.alias.to_string(),
+                    repository_id: Some(attachment.working_directory.summary.repository_id.clone()),
+                    repository_key: None,
+                    working_directory_id: SubscriptionWorkdirId::new(
+                        attachment
+                            .working_directory
+                            .summary
+                            .working_directory_id
+                            .clone(),
+                    )
+                    .map_err(subscription_validation_error)?,
+                })
             })
-            .transpose()?;
+            .collect::<Result<Vec<_>, RuntimeError>>()?;
         let profile = match &worker.profile {
             ProfileSelector::Builtin(name) | ProfileSelector::Named(name) => Some(name.clone()),
         };
@@ -3425,9 +3589,7 @@ impl RuntimeState {
             workspace_id: worker.workspace_id.clone(),
             display_name: worker.display_name.clone(),
             profile,
-            repository_id,
-            repository_key: None,
-            working_directory_id,
+            workdir_attachments,
         })
     }
 
@@ -3525,22 +3687,15 @@ impl RuntimeState {
         }
     }
 
-    fn primary_worker_id_for_workdir(&self, working_directory_id: &str) -> Option<WorkerId> {
+    fn worker_id_for_workdir(&self, working_directory_id: &str) -> Option<WorkerId> {
         self.workers.values().find_map(|worker| {
-            if worker
-                .working_directory
-                .as_ref()
-                .is_some_and(|binding| binding.summary.working_directory_id == working_directory_id)
-                || worker
-                    .request
-                    .as_ref()
-                    .and_then(requested_primary_workdir_id)
-                    == Some(working_directory_id)
-            {
-                Some(worker.worker_id)
-            } else {
-                None
-            }
+            let has_status = worker.workdir_attachments.iter().any(|attachment| {
+                attachment.working_directory.summary.working_directory_id == working_directory_id
+            });
+            let has_request = worker.request.as_ref().is_some_and(|request| {
+                requested_workdir_ids(request).contains(&working_directory_id)
+            });
+            (has_status || has_request).then_some(worker.worker_id)
         })
     }
 
@@ -3976,7 +4131,7 @@ struct WorkerRecord {
     execution_metadata_available: bool,
     execution_bound: bool,
     restore_intent: WorkerRestoreIntent,
-    working_directory: Option<CatalogWorkingDirectoryStatus>,
+    workdir_attachments: Vec<crate::catalog::WorkingDirectoryAttachmentStatus>,
     execution_handle: Option<WorkerExecutionHandle>,
     internal_workers: InternalWorkerActivityProjection,
 }
@@ -3999,7 +4154,7 @@ impl WorkerRecord {
             execution_metadata_available: self.execution_metadata_available,
             worker_state: self.worker_state.clone(),
             workspace_id: self.workspace_id.clone(),
-            working_directory: self.working_directory.clone(),
+            workdir_attachments: self.workdir_attachments.clone(),
             profile: self.profile.clone(),
             display_name: self.display_name.clone(),
             profile_source: self.profile_source.clone(),
@@ -4016,7 +4171,7 @@ impl WorkerRecord {
             execution_metadata_available: self.execution_metadata_available,
             worker_state: self.worker_state.clone(),
             workspace_id: self.workspace_id.clone(),
-            working_directory: self.working_directory.clone(),
+            workdir_attachments: self.workdir_attachments.clone(),
             profile: self.profile.clone(),
             display_name: self.display_name.clone(),
             profile_source: self.profile_source.clone(),
@@ -4049,7 +4204,7 @@ impl WorkerRecord {
             status: self.status,
             execution_state,
             workspace_id: self.workspace_id.clone(),
-            working_directory: self.working_directory.clone(),
+            workdir_attachments: self.workdir_attachments.clone(),
         }
     }
 }
@@ -4100,25 +4255,28 @@ fn repository_resource_error(error: BackendResourceError) -> RuntimeError {
 
 fn durable_create_worker_request(request: &CreateWorkerRequest) -> CreateWorkerRequest {
     let mut durable = request.clone();
-    if let Some(working_directory) = durable.working_directory_request.as_mut()
-        && let Some(materialization) = working_directory.materialization.as_mut()
-    {
-        materialization.ssh = None;
+    for attachment in &mut durable.workdir_attachment_requests {
+        if let Some(materialization) = attachment.working_directory.materialization.as_mut() {
+            materialization.ssh = None;
+        }
     }
     durable
 }
 
-fn requested_primary_workdir_id(request: &CreateWorkerRequest) -> Option<&str> {
+fn requested_workdir_ids(request: &CreateWorkerRequest) -> Vec<&str> {
     request
-        .working_directory
-        .as_ref()
+        .workdir_attachments
+        .iter()
         .map(|claim| claim.working_directory_id.as_str())
-        .or_else(|| {
+        .chain(
             request
-                .working_directory_request
-                .as_ref()
-                .and_then(|request| request.backend_workdir_id.as_deref())
-        })
+                .workdir_attachment_requests
+                .iter()
+                .filter_map(|attachment| {
+                    attachment.working_directory.backend_workdir_id.as_deref()
+                }),
+        )
+        .collect()
 }
 
 fn validate_create_worker_request(request: &CreateWorkerRequest) -> Result<(), RuntimeError> {
@@ -4127,6 +4285,42 @@ fn validate_create_worker_request(request: &CreateWorkerRequest) -> Result<(), R
             "create_fingerprint must not be empty".to_string(),
         ));
     }
+    let mut aliases = std::collections::BTreeSet::new();
+    let mut workdir_ids = std::collections::BTreeSet::new();
+    for (alias, workdir_id) in request
+        .workdir_attachments
+        .iter()
+        .map(|attachment| {
+            (
+                &attachment.alias,
+                Some(attachment.working_directory_id.as_str()),
+            )
+        })
+        .chain(
+            request
+                .workdir_attachment_requests
+                .iter()
+                .map(|attachment| {
+                    (
+                        &attachment.alias,
+                        attachment.working_directory.backend_workdir_id.as_deref(),
+                    )
+                }),
+        )
+    {
+        if !aliases.insert(alias.as_str()) {
+            return Err(RuntimeError::InvalidRequest(format!(
+                "duplicate Workdir attachment alias `{alias}`"
+            )));
+        }
+        if let Some(workdir_id) = workdir_id
+            && !workdir_ids.insert(workdir_id)
+        {
+            return Err(RuntimeError::InvalidRequest(format!(
+                "working directory `{workdir_id}` cannot be attached more than once"
+            )));
+        }
+    }
     match &request.profile_source {
         crate::catalog::ProfileSourceArchiveSource::Embedded { archive } => {
             archive.verify().map_err(|err| {
@@ -4420,8 +4614,8 @@ mod tests {
     use crate::catalog::{
         ConfigBundleRef, MaterializerKind, ProfileSelector, RepositoryMaterializationContext,
         RepositorySshCredentialCandidate, RepositorySshMaterializationAccess, SensitiveString,
-        WorkingDirectoryClaim, WorkingDirectoryRepository, WorkingDirectoryRequest,
-        WorkspaceApiRef,
+        WorkingDirectoryAttachmentClaim, WorkingDirectoryAttachmentRequest,
+        WorkingDirectoryRepository, WorkingDirectoryRequest, WorkspaceApiRef,
     };
     use crate::config_bundle::{
         ConfigBundle, ConfigBundleMetadata, ConfigBundleProvenance, ConfigDeclaration,
@@ -4913,8 +5107,8 @@ mod tests {
                 digest: bundle.metadata.digest,
             }),
             initial_input: None,
-            working_directory_request: None,
-            working_directory: None,
+            workdir_attachment_requests: Vec::new(),
+            workdir_attachments: Vec::new(),
             worker_observation_enabled: false,
             worker_observation_grants: Vec::new(),
             workspace_api: None,
@@ -4929,60 +5123,64 @@ mod tests {
     #[test]
     fn durable_worker_request_omits_repository_credentials() {
         let mut request = task_request("worker-secret-redaction");
-        request.working_directory_request = Some(WorkingDirectoryRequest {
-            repository: WorkingDirectoryRepository {
-                id: "repository-1".to_string(),
-                provider: "git".to_string(),
-                source: server_api::RepositorySource {
-                    kind: server_api::RepositorySourceKind::Ssh,
-                    uri: "ssh://git@example.test/repo.git".to_string(),
+        request.workdir_attachment_requests = vec![WorkingDirectoryAttachmentRequest {
+            alias: workdir::WorkdirAttachmentAlias::new("checkout").unwrap(),
+            working_directory: WorkingDirectoryRequest {
+                repository: WorkingDirectoryRepository {
+                    id: "repository-1".to_string(),
+                    provider: "git".to_string(),
+                    source: server_api::RepositorySource {
+                        kind: server_api::RepositorySourceKind::Ssh,
+                        uri: "ssh://git@example.test/repo.git".to_string(),
+                    },
+                    source_revision: 1,
+                    source_fingerprint: "sha256:source".to_string(),
+                    selector: None,
                 },
-                source_revision: 1,
-                source_fingerprint: "sha256:source".to_string(),
-                selector: None,
-            },
-            materializer: MaterializerKind::RuntimeGitClone,
-            backend_workdir_id: Some("working-directory-1".to_string()),
-            materialization: Some(RepositoryMaterializationContext {
-                workspace_id: "workspace-1".to_string(),
-                runtime_id: "runtime-1".to_string(),
-                operation_id: "operation-1".to_string(),
-                config_revision: 1,
-                config_projection_digest: "sha256:projection".to_string(),
-                ssh: Some(RepositorySshMaterializationAccess {
-                    credential_candidates: vec![RepositorySshCredentialCandidate {
-                        credential_id: "credential-1".to_string(),
-                        credential_revision: 1,
-                        private_key: SensitiveString::new("private-key-bytes"),
-                    }],
-                    host_trust_id: "host-trust-1".to_string(),
-                    host_trust_revision: 1,
-                    access: server_api::RepositoryAccessMode::ReadOnly,
-                    expires_at_epoch_seconds: u64::MAX,
-                    repository_id: "repository-1".to_string(),
-                    repository_source_fingerprint: "sha256:source".to_string(),
-                    repository_uri: "ssh://git@example.test/repo.git".to_string(),
-                    secret_resource: repository_resource_handle(),
-                    known_hosts_entry: SensitiveString::new("known-hosts-entry"),
+                display_name: None,
+                materializer: MaterializerKind::RuntimeGitClone,
+                backend_workdir_id: Some("working-directory-1".to_string()),
+                materialization: Some(RepositoryMaterializationContext {
+                    workspace_id: "workspace-1".to_string(),
+                    runtime_id: "runtime-1".to_string(),
+                    operation_id: "operation-1".to_string(),
+                    config_revision: 1,
+                    config_projection_digest: "sha256:projection".to_string(),
+                    ssh: Some(RepositorySshMaterializationAccess {
+                        credential_candidates: vec![RepositorySshCredentialCandidate {
+                            credential_id: "credential-1".to_string(),
+                            credential_revision: 1,
+                            private_key: SensitiveString::new("private-key-bytes"),
+                        }],
+                        host_trust_id: "host-trust-1".to_string(),
+                        host_trust_revision: 1,
+                        access: server_api::RepositoryAccessMode::ReadOnly,
+                        expires_at_epoch_seconds: u64::MAX,
+                        repository_id: "repository-1".to_string(),
+                        repository_source_fingerprint: "sha256:source".to_string(),
+                        repository_uri: "ssh://git@example.test/repo.git".to_string(),
+                        secret_resource: repository_resource_handle(),
+                        known_hosts_entry: SensitiveString::new("known-hosts-entry"),
+                    }),
                 }),
-            }),
-        });
+            },
+        }];
 
         let durable = durable_create_worker_request(&request);
 
         assert!(
             request
-                .working_directory_request
-                .as_ref()
-                .and_then(|working_directory| working_directory.materialization.as_ref())
+                .workdir_attachment_requests
+                .first()
+                .and_then(|attachment| attachment.working_directory.materialization.as_ref())
                 .and_then(|materialization| materialization.ssh.as_ref())
                 .is_some()
         );
         assert!(
             durable
-                .working_directory_request
-                .as_ref()
-                .and_then(|working_directory| working_directory.materialization.as_ref())
+                .workdir_attachment_requests
+                .first()
+                .and_then(|attachment| attachment.working_directory.materialization.as_ref())
                 .and_then(|materialization| materialization.ssh.as_ref())
                 .is_none()
         );
@@ -5172,6 +5370,7 @@ mod tests {
                 source_fingerprint: "sha256:source".to_string(),
                 selector: None,
             },
+            display_name: None,
             materializer: MaterializerKind::RuntimeGitClone,
             backend_workdir_id: Some("working-directory-1".to_string()),
             materialization: Some(RepositoryMaterializationContext {
@@ -5342,6 +5541,7 @@ mod tests {
 
     #[derive(Default)]
     struct TestExecutionBackend {
+        spawn_result: Mutex<Option<WorkerExecutionSpawnResult>>,
         dispatch_result: Mutex<Option<WorkerExecutionResult>>,
         stop_result: Mutex<Option<WorkerExecutionResult>>,
         stop_gate: Mutex<Option<Arc<RestoreGate>>>,
@@ -5447,6 +5647,9 @@ mod tests {
         }
 
         fn spawn_worker(&self, request: WorkerExecutionSpawnRequest) -> WorkerExecutionSpawnResult {
+            if let Some(result) = self.spawn_result.lock().unwrap().take() {
+                return result;
+            }
             self.config_bundles
                 .lock()
                 .unwrap()
@@ -5460,10 +5663,16 @@ mod tests {
                 worker_state: protocol::WorkerStateSnapshot {
                     ..protocol::WorkerStatus::Idle.into()
                 },
-                working_directory: request
-                    .working_directory
-                    .as_ref()
-                    .map(|binding| binding.status()),
+                workdir_attachments: request
+                    .workdir_attachments
+                    .iter()
+                    .map(
+                        |(alias, binding)| crate::catalog::WorkingDirectoryAttachmentStatus {
+                            alias: alias.clone(),
+                            working_directory: binding.status(),
+                        },
+                    )
+                    .collect(),
             }
         }
 
@@ -5502,10 +5711,16 @@ mod tests {
                 worker_state: protocol::WorkerStateSnapshot {
                     ..protocol::WorkerStatus::Idle.into()
                 },
-                working_directory: request
-                    .working_directory
-                    .as_ref()
-                    .map(|binding| binding.status()),
+                workdir_attachments: request
+                    .workdir_attachments
+                    .iter()
+                    .map(
+                        |(alias, binding)| crate::catalog::WorkingDirectoryAttachmentStatus {
+                            alias: alias.clone(),
+                            working_directory: binding.status(),
+                        },
+                    )
+                    .collect(),
             }
         }
 
@@ -6263,10 +6478,11 @@ mod tests {
         let runtime = runtime_with_backend();
         let mut request = task_request("idempotent");
         request.create_fingerprint = "sha256:input-1".to_string();
-        request.working_directory = Some(WorkingDirectoryClaim {
+        request.workdir_attachments = vec![WorkingDirectoryAttachmentClaim {
+            alias: workdir::WorkdirAttachmentAlias::new("workdir").unwrap(),
             working_directory_id: "workdir-idempotent".to_string(),
             relative_cwd: None,
-        });
+        }];
 
         let first = runtime.create_worker(request.clone()).unwrap();
         let workdir_count_after_first = runtime.list_working_directories().unwrap().len();
@@ -6631,6 +6847,49 @@ mod tests {
         assert!(runtime.list_workers().unwrap().is_empty());
     }
 
+    #[test]
+    fn reconciliation_required_create_retains_durable_worker_evidence() {
+        let (runtime, backend) = runtime_and_backend();
+        runtime.store_config_bundle(test_bundle()).unwrap();
+        *backend.spawn_result.lock().unwrap() =
+            Some(WorkerExecutionSpawnResult::ReconciliationRequired {
+                result: WorkerExecutionResult::errored(
+                    WorkerExecutionOperation::Spawn,
+                    "Workdir cleanup could not be proven",
+                ),
+                handle: None,
+                worker_state: None,
+                workdir_attachments: vec![WorkingDirectoryAttachmentStatus {
+                    alias: workdir::WorkdirAttachmentAlias::new("checkout").unwrap(),
+                    working_directory: serde_json::from_value(serde_json::json!({
+                        "summary": {
+                            "working_directory_id": "wd-uncertain",
+                            "repository_id": "repo",
+                            "materializer_kind": "runtime_git_clone",
+                            "status": "active"
+                        }
+                    }))
+                    .unwrap(),
+                }],
+            });
+        let request = task_request("uncertain create cleanup");
+        let worker_ref = WorkerRef::new(request.worker_id);
+
+        let error = runtime.create_worker(request).unwrap_err();
+
+        assert!(matches!(
+            error,
+            RuntimeError::WorkerExecutionRejected { .. }
+        ));
+        let retained = runtime.worker_detail(&worker_ref).unwrap();
+        assert_eq!(retained.status, WorkerStatus::Idle);
+        assert!(!retained.execution_metadata_available);
+        assert!(matches!(
+            runtime.delete_worker(&worker_ref),
+            Err(RuntimeError::InvalidRequest(_))
+        ));
+    }
+
     #[test]
     fn create_worker_without_execution_backend_is_rejected_and_not_persisted() {
         let runtime = Runtime::new_memory();
@@ -6804,10 +7063,16 @@ mod tests {
                 worker_state: protocol::WorkerStateSnapshot {
                     ..protocol::WorkerStatus::Idle.into()
                 },
-                working_directory: request
-                    .working_directory
-                    .as_ref()
-                    .map(|binding| binding.status()),
+                workdir_attachments: request
+                    .workdir_attachments
+                    .iter()
+                    .map(
+                        |(alias, binding)| crate::catalog::WorkingDirectoryAttachmentStatus {
+                            alias: alias.clone(),
+                            working_directory: binding.status(),
+                        },
+                    )
+                    .collect(),
             }
         }
 
@@ -7667,7 +7932,7 @@ mod tests {
                 ),
                 handle: None,
                 worker_state: None,
-                working_directory: None,
+                workdir_attachments: Vec::new(),
             },
         );
 

crates/worker-runtime/src/worker_backend.rs

@@ -7,7 +7,7 @@
 //! socket paths, session paths, manifests, credentials, or handles leave this
 //! module.
 
-use std::collections::HashMap;
+use std::collections::{BTreeMap, HashMap};
 use std::future::Future;
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
@@ -17,8 +17,9 @@ use std::time::Duration;
 use crate::auth::{BACKEND_RESOURCE_FETCH_PERMISSION, RuntimeIdentityMaterial};
 use crate::catalog::{
     CreateWorkerRequest, ProfileSourceArchiveSource, RepositoryRefObservation,
-    RepositoryRefObservationRequest, WorkingDirectoryRepositoryAccessRequest,
-    WorkingDirectoryRequest, WorkingDirectoryStatus, WorkingDirectoryStatusKind,
+    RepositoryRefObservationRequest, WorkingDirectoryAttachmentStatus,
+    WorkingDirectoryRepositoryAccessRequest, WorkingDirectoryRequest, WorkingDirectoryStatus,
+    WorkingDirectoryStatusKind,
 };
 use crate::config_bundle::{ConfigBundle, workspace_config_etag};
 use crate::execution::{
@@ -44,6 +45,45 @@ use protocol::{Event, Method, Segment, WorkerCommandEnvelope};
 
 static NEXT_INTERNAL_COMMAND_ID: AtomicU64 = AtomicU64::new(1);
 
+fn rollback_materialized_spawn_workdirs(
+    materializer: &dyn WorkingDirectoryMaterializer,
+    bindings: &BTreeMap<WorkdirAttachmentAlias, WorkingDirectoryBinding>,
+    workdir_ids: &[String],
+    failure_context: &str,
+) -> Result<(), WorkerExecutionSpawnResult> {
+    let mut cleanup_failures = Vec::new();
+    let mut uncertain_attachments = Vec::new();
+    for workdir_id in workdir_ids.iter().rev() {
+        if let Err(error) = materializer.cleanup_working_directory(workdir_id) {
+            cleanup_failures.push(format!("{workdir_id}: {error}"));
+            if let Some((alias, binding)) = bindings
+                .iter()
+                .find(|(_, binding)| binding.working_directory.id == *workdir_id)
+            {
+                uncertain_attachments.push(WorkingDirectoryAttachmentStatus {
+                    alias: alias.clone(),
+                    working_directory: binding.status(),
+                });
+            }
+        }
+    }
+    if cleanup_failures.is_empty() {
+        return Ok(());
+    }
+    Err(WorkerExecutionSpawnResult::ReconciliationRequired {
+        result: WorkerExecutionResult::errored(
+            WorkerExecutionOperation::Spawn,
+            format!(
+                "{failure_context}; Workdir cleanup could not be proven: {}",
+                cleanup_failures.join("; ")
+            ),
+        ),
+        handle: None,
+        worker_state: None,
+        workdir_attachments: uncertain_attachments,
+    })
+}
+
 fn next_internal_command(
     state: &RwLock<protocol::WorkerStateSnapshot>,
 ) -> Result<WorkerCommandEnvelope, String> {
@@ -68,7 +108,10 @@ use session_store::{FsStore, FsWorkerStore};
 use tokio::runtime::Runtime;
 #[cfg(feature = "ws-server")]
 use tokio::sync::broadcast;
-use workdir::{LocalWorkdirSession, Workdir, WorkdirSessionCapabilities, WorkdirSessionHandle};
+use workdir::{
+    LocalWorkdirSession, Workdir, WorkdirAttachmentAlias, WorkdirSessionCapabilities,
+    WorkdirSessionHandle, WorkdirSessionRouter,
+};
 
 #[cfg(test)]
 use worker::WorkerController;
@@ -730,6 +773,29 @@ fn runtime_local_workdir_session(
     ))
 }
 
+fn runtime_local_workdir_router(
+    attachments: &BTreeMap<WorkdirAttachmentAlias, WorkingDirectoryBinding>,
+    scope: manifest::SharedScope,
+) -> Result<Arc<WorkdirSessionRouter>, String> {
+    let router = Arc::new(WorkdirSessionRouter::new());
+    for (alias, binding) in attachments {
+        router
+            .attach(
+                alias.clone(),
+                runtime_local_workdir_session(
+                    &binding.working_directory.id,
+                    binding.root(),
+                    binding.cwd(),
+                    scope.clone(),
+                    binding.command_environment(),
+                    binding.session_resources(),
+                ),
+            )
+            .map_err(|error| format!("bind Workdir attachment `{alias}`: {error}"))?;
+    }
+    Ok(router)
+}
+
 fn bind_workspace_memory_settings(
     manifest: &mut manifest::WorkerManifest,
     request: &CreateWorkerRequest,
@@ -845,15 +911,14 @@ impl RuntimeWorkerFactory for ProfileRuntimeWorkerFactory {
     ) -> Result<RuntimeWorkerController, String> {
         let worker_name = Self::runtime_worker_name(&request);
         let profile = Self::runtime_profile(&request);
-        let has_local_filesystem = request.working_directory.is_some();
-        let worker_root = request
-            .working_directory
-            .as_ref()
+        let has_local_filesystem = request.workdir_attachments.len() == 1;
+        let only_binding = (request.workdir_attachments.len() == 1)
+            .then(|| request.workdir_attachments.values().next())
+            .flatten();
+        let worker_root = only_binding
             .map(|binding| binding.root().to_path_buf())
             .unwrap_or_else(|| self.profile_base_dir.clone());
-        let filesystem_authority = request
-            .working_directory
-            .as_ref()
+        let filesystem_authority = only_binding
             .map(|binding| {
                 WorkerFilesystemAuthority::local(
                     binding.root().to_path_buf(),
@@ -965,18 +1030,10 @@ impl RuntimeWorkerFactory for ProfileRuntimeWorkerFactory {
         })?;
         let worker = prepared.worker_mut();
         validate_worker_memory_settings(worker.manifest(), &request.request)?;
-        if let Some(binding) = request.working_directory.as_ref() {
-            worker.bind_workdir_session(Some(runtime_local_workdir_session(
-                &binding.working_directory.id,
-                binding.root(),
-                binding.cwd(),
-                worker.scope().clone(),
-                binding.command_environment(),
-                binding.session_resources(),
-            )));
-        } else {
-            worker.bind_workdir_session(None);
-        }
+        worker.bind_workdir_sessions(runtime_local_workdir_router(
+            &request.workdir_attachments,
+            worker.scope().clone(),
+        )?);
         if let (Some(runtime_id), Some(workspace_id)) =
             (observation_runtime_id, observation_workspace_id.clone())
             && observation_enabled
@@ -1095,9 +1152,10 @@ impl RuntimeWorkerFactory for ProfileRuntimeWorkerFactory {
         request: WorkerExecutionRestoreRequest,
     ) -> Result<RuntimeWorkerController, String> {
         let worker_name = Self::runtime_worker_name_for_ref(&request.worker_ref);
-        let filesystem_authority = request
-            .working_directory
-            .as_ref()
+        let only_binding = (request.workdir_attachments.len() == 1)
+            .then(|| request.workdir_attachments.values().next())
+            .flatten();
+        let filesystem_authority = only_binding
             .map(|binding| {
                 WorkerFilesystemAuthority::local(
                     binding.root().to_path_buf(),
@@ -1201,18 +1259,10 @@ impl RuntimeWorkerFactory for ProfileRuntimeWorkerFactory {
         };
         validate_worker_memory_settings(worker.manifest(), &request.request)?;
         let flow_transition_enabled = worker.manifest().feature.flow.enabled;
-        if let Some(binding) = request.working_directory.as_ref() {
-            worker.bind_workdir_session(Some(runtime_local_workdir_session(
-                &binding.working_directory.id,
-                binding.root(),
-                binding.cwd(),
-                worker.scope().clone(),
-                binding.command_environment(),
-                binding.session_resources(),
-            )));
-        } else {
-            worker.bind_workdir_session(None);
-        }
+        worker.bind_workdir_sessions(runtime_local_workdir_router(
+            &request.workdir_attachments,
+            worker.scope().clone(),
+        )?);
         if let (Some(runtime_id), Some(workspace_id)) =
             (observation_runtime_id, observation_workspace_id.clone())
             && observation_enabled
@@ -1738,7 +1788,7 @@ where
         handle: WorkerHandle,
         shutdown: Arc<tokio::sync::Mutex<Option<worker::ShutdownReceiver>>>,
         controller_task: tokio::task::JoinHandle<()>,
-        working_directory: Option<WorkingDirectoryBinding>,
+        workdir_attachments: BTreeMap<WorkdirAttachmentAlias, WorkingDirectoryBinding>,
         workspace_client: Option<Arc<dyn WorkspaceClient>>,
     ) -> WorkerExecutionSpawnResult {
         #[cfg(feature = "ws-server")]
@@ -1818,8 +1868,13 @@ where
                             Err(_) => {
                                 let retained_state =
                                     worker_state.read().ok().map(|state| state.clone());
-                                let retained_working_directory =
-                                    working_directory.as_ref().map(|binding| binding.status());
+                                let retained_workdir_attachments = workdir_attachments
+                                    .iter()
+                                    .map(|(alias, binding)| crate::catalog::WorkingDirectoryAttachmentStatus {
+                                        alias: alias.clone(),
+                                        working_directory: binding.status(),
+                                    })
+                                    .collect();
                                 let retained_handle = self
                                     .retain_uncertain_unconnected_controller(
                                         &worker_ref,
@@ -1834,7 +1889,7 @@ where
                                     result,
                                     handle: retained_handle,
                                     worker_state: retained_state,
-                                    working_directory: retained_working_directory,
+                                    workdir_attachments: retained_workdir_attachments,
                                 }
                             }
                         }
@@ -1878,7 +1933,7 @@ where
                         result,
                         handle: Some(existing_handle),
                         worker_state: existing_worker_state,
-                        working_directory: None,
+                        workdir_attachments: Vec::new(),
                     },
                 }
             } else {
@@ -1904,7 +1959,15 @@ where
         WorkerExecutionSpawnResult::Connected {
             handle: WorkerExecutionHandle::new(worker_ref, self.backend_id()),
             worker_state: connected_worker_state,
-            working_directory: working_directory.map(|binding| binding.status()),
+            workdir_attachments: workdir_attachments
+                .into_iter()
+                .map(
+                    |(alias, binding)| crate::catalog::WorkingDirectoryAttachmentStatus {
+                        alias,
+                        working_directory: binding.status(),
+                    },
+                )
+                .collect(),
         }
     }
 }
@@ -2118,67 +2181,134 @@ where
         }
 
         let mut request = request;
-        let mut rollback_working_directory = None;
-        let working_directory = match (
-            request.request.working_directory_request.as_ref(),
-            request.request.working_directory.as_ref(),
-        ) {
-            (Some(_), Some(_)) => {
+        let Some(materializer) = self.working_directory_materializer.as_ref().or_else(|| {
+            (request.request.workdir_attachment_requests.is_empty()
+                && request.request.workdir_attachments.is_empty())
+            .then_some(())
+            .and(None)
+        }) else {
+            if request.request.workdir_attachment_requests.is_empty()
+                && request.request.workdir_attachments.is_empty()
+            {
+                // No provider is needed for a Workdir-less Worker.
+                let factory = self.factory.clone();
+                let bridge_context = request.context.clone();
+                let worker_ref = request.worker_ref.clone();
+                let spawn_result = self
+                    .run_cancellable_on_adapter_runtime(self.spawn_restore_timeout, async move {
+                        factory.spawn_controller(request).await
+                    });
+                let controller = match spawn_result {
+                    Ok(controller) => controller,
+                    Err(message) => {
+                        return WorkerExecutionSpawnResult::Errored(
+                            WorkerExecutionResult::errored(
+                                WorkerExecutionOperation::Spawn,
+                                message,
+                            ),
+                        );
+                    }
+                };
+                return self.connect_handle(
+                    WorkerExecutionOperation::Spawn,
+                    worker_ref,
+                    bridge_context,
+                    controller.handle,
+                    controller.shutdown,
+                    controller.controller_task,
+                    BTreeMap::new(),
+                    Some(controller.workspace_client),
+                );
+            }
+            return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
+                WorkerExecutionOperation::Spawn,
+                "Workdir attachments were requested, but no materializer is configured for this Runtime backend",
+            ));
+        };
+        let mut rollback_workdirs: Vec<String> = Vec::new();
+        for attachment in request.request.workdir_attachment_requests.clone() {
+            if request.workdir_attachments.contains_key(&attachment.alias) {
+                let message = format!("duplicate Workdir attachment alias `{}`", attachment.alias);
+                if let Err(result) = rollback_materialized_spawn_workdirs(
+                    materializer.as_ref(),
+                    &request.workdir_attachments,
+                    &rollback_workdirs,
+                    &message,
+                ) {
+                    return result;
+                }
                 return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
                     WorkerExecutionOperation::Spawn,
-                    "worker spawn cannot specify both working_directory_request and working_directory",
+                    message,
                 ));
             }
-            (Some(working_directory_request), None) => {
-                let Some(materializer) = self.working_directory_materializer.as_ref() else {
+            match materializer.materialize(&request.worker_ref, &attachment.working_directory) {
+                Ok(binding) => {
+                    rollback_workdirs.push(binding.working_directory.id.clone());
+                    request
+                        .workdir_attachments
+                        .insert(attachment.alias, binding);
+                }
+                Err(error) => {
+                    let message = error.to_string();
+                    if let Err(result) = rollback_materialized_spawn_workdirs(
+                        materializer.as_ref(),
+                        &request.workdir_attachments,
+                        &rollback_workdirs,
+                        &message,
+                    ) {
+                        return result;
+                    }
                     return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
                         WorkerExecutionOperation::Spawn,
-                        "working directory materialization requested, but no materializer is configured for this runtime backend",
+                        message,
                     ));
-                };
-                match materializer.materialize(&request.worker_ref, working_directory_request) {
-                    Ok(binding) => {
-                        request.working_directory = Some(binding.clone());
-                        rollback_working_directory = Some(binding.clone());
-                        Some(binding)
-                    }
-                    Err(error) => {
-                        return WorkerExecutionSpawnResult::Rejected(
-                            WorkerExecutionResult::rejected(
-                                WorkerExecutionOperation::Spawn,
-                                error.to_string(),
-                            ),
-                        );
-                    }
                 }
             }
-            (None, Some(working_directory)) => {
-                let Some(materializer) = self.working_directory_materializer.as_ref() else {
-                    return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
-                        WorkerExecutionOperation::Spawn,
-                        "working directory working_directory requested, but no materializer is configured for this runtime backend",
-                    ));
-                };
-                match materializer.bind_working_directory(
-                    &working_directory.working_directory_id,
-                    working_directory.relative_cwd.as_deref(),
+        }
+        for attachment in request.request.workdir_attachments.clone() {
+            if request.workdir_attachments.contains_key(&attachment.alias) {
+                let message = format!("duplicate Workdir attachment alias `{}`", attachment.alias);
+                if let Err(result) = rollback_materialized_spawn_workdirs(
+                    materializer.as_ref(),
+                    &request.workdir_attachments,
+                    &rollback_workdirs,
+                    &message,
                 ) {
-                    Ok(binding) => {
-                        request.working_directory = Some(binding.clone());
-                        Some(binding)
-                    }
-                    Err(error) => {
-                        return WorkerExecutionSpawnResult::Rejected(
-                            WorkerExecutionResult::rejected(
-                                WorkerExecutionOperation::Spawn,
-                                error.to_string(),
-                            ),
-                        );
+                    return result;
+                }
+                return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
+                    WorkerExecutionOperation::Spawn,
+                    message,
+                ));
+            }
+            match materializer.bind_working_directory(
+                &attachment.working_directory_id,
+                attachment.relative_cwd.as_deref(),
+            ) {
+                Ok(binding) => {
+                    request
+                        .workdir_attachments
+                        .insert(attachment.alias, binding);
+                }
+                Err(error) => {
+                    let message = error.to_string();
+                    if let Err(result) = rollback_materialized_spawn_workdirs(
+                        materializer.as_ref(),
+                        &request.workdir_attachments,
+                        &rollback_workdirs,
+                        &message,
+                    ) {
+                        return result;
                     }
+                    return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
+                        WorkerExecutionOperation::Spawn,
+                        message,
+                    ));
                 }
             }
-            (None, None) => None,
-        };
+        }
+        let workdir_attachments = request.workdir_attachments.clone();
 
         let factory = self.factory.clone();
         let bridge_context = request.context.clone();
@@ -2191,11 +2321,13 @@ where
         let controller = match spawn_result {
             Ok(controller) => controller,
             Err(message) => {
-                if let (Some(materializer), Some(binding)) = (
-                    self.working_directory_materializer.as_ref(),
-                    rollback_working_directory.as_ref(),
+                if let Err(result) = rollback_materialized_spawn_workdirs(
+                    materializer.as_ref(),
+                    &workdir_attachments,
+                    &rollback_workdirs,
+                    &message,
                 ) {
-                    let _ = materializer.cleanup_working_directory(&binding.working_directory.id);
+                    return result;
                 }
                 return WorkerExecutionSpawnResult::Errored(WorkerExecutionResult::errored(
                     WorkerExecutionOperation::Spawn,
@@ -2211,7 +2343,7 @@ where
             controller.handle,
             controller.shutdown,
             controller.controller_task,
-            working_directory,
+            workdir_attachments,
             Some(controller.workspace_client),
         )
     }
@@ -2232,46 +2364,56 @@ where
         }
         drop(workers);
 
-        if let Some(previous) = request.previous_working_directory.as_ref() {
+        if !request.previous_workdir_attachments.is_empty() {
             let materializer = self
                 .working_directory_materializer
                 .as_ref()
                 .ok_or_else(|| {
                     WorkerExecutionResult::rejected(
                         WorkerExecutionOperation::Restore,
-                        "Persisted Worker Workdir binding cannot be restored by this Runtime",
+                        "Persisted Worker Workdir attachments cannot be restored by this Runtime",
                     )
                 })?;
-            let current = materializer
-                .working_directory_status(&previous.summary.working_directory_id)
-                .map_err(|message| {
-                    WorkerExecutionResult::rejected(
+            for previous in &request.previous_workdir_attachments {
+                let current = materializer
+                    .working_directory_status(
+                        &previous.working_directory.summary.working_directory_id,
+                    )
+                    .map_err(|message| {
+                        WorkerExecutionResult::rejected(
+                            WorkerExecutionOperation::Restore,
+                            format!(
+                                "Persisted Worker Workdir attachment `{}` is unavailable: {message}",
+                                previous.alias
+                            ),
+                        )
+                    })?;
+                if current.summary.status != WorkingDirectoryStatusKind::Active {
+                    return Err(WorkerExecutionResult::rejected(
                         WorkerExecutionOperation::Restore,
-                        format!("Persisted Worker Workdir is unavailable: {message}"),
-                    )
-                })?;
-            if current.summary.status != WorkingDirectoryStatusKind::Active {
-                return Err(WorkerExecutionResult::rejected(
-                    WorkerExecutionOperation::Restore,
-                    "Persisted Worker Workdir is not active",
-                ));
+                        format!(
+                            "Persisted Worker Workdir attachment `{}` is not active",
+                            previous.alias
+                        ),
+                    ));
+                }
             }
         }
-        if request.previous_working_directory.is_none()
-            && request.request.working_directory_request.is_some()
+        if request.previous_workdir_attachments.is_empty()
+            && !request.request.workdir_attachment_requests.is_empty()
         {
             return Err(WorkerExecutionResult::rejected(
                 WorkerExecutionOperation::Restore,
-                "Persisted Worker Workdir allocation is unavailable",
+                "Persisted Worker Workdir allocations are unavailable",
             ));
         }
-        if request.previous_working_directory.is_none()
-            && request.request.working_directory.is_some()
+        if request.previous_workdir_attachments.is_empty()
+            && !request.request.workdir_attachments.is_empty()
             && self.working_directory_materializer.is_none()
         {
             return Err(WorkerExecutionResult::rejected(
                 WorkerExecutionOperation::Restore,
-                "Persisted Worker Workdir claim cannot be restored by this Runtime",
+                "Persisted Worker Workdir claims cannot be restored by this Runtime",
             ));
         }
         if let Some(workspace_api) = request.request.workspace_api.as_ref() {
@@ -2321,58 +2463,40 @@ where
         }
         drop(workers);
 
-        let working_directory = match request.previous_working_directory.clone() {
-            Some(status) => {
-                let Some(materializer) = self.working_directory_materializer.as_ref() else {
-                    return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
-                        WorkerExecutionOperation::Restore,
-                        "persisted worker has a working directory binding, but no materializer is configured for this runtime backend",
-                    ));
-                };
-                let relative_cwd = request
-                    .request
-                    .working_directory
-                    .as_ref()
-                    .and_then(|working_directory| working_directory.relative_cwd.as_deref());
-                match materializer
-                    .bind_working_directory(&status.summary.working_directory_id, relative_cwd)
-                {
-                    Ok(binding) => {
-                        request.working_directory = Some(binding.clone());
-                        Some(binding)
-                    }
-                    Err(error) => {
-                        return WorkerExecutionSpawnResult::Rejected(
-                            WorkerExecutionResult::rejected(
-                                WorkerExecutionOperation::Restore,
-                                error.to_string(),
-                            ),
-                        );
-                    }
-                }
-            }
-            None if request.request.working_directory_request.is_some() => {
+        let mut workdir_attachments = BTreeMap::new();
+        if !request.previous_workdir_attachments.is_empty() {
+            let Some(materializer) = self.working_directory_materializer.as_ref() else {
                 return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
                     WorkerExecutionOperation::Restore,
-                    "persisted worker requested a working directory, but no persisted working directory binding is available to restore",
+                    "persisted Worker has Workdir attachments, but no materializer is configured for this Runtime backend",
                 ));
-            }
-            None if request.request.working_directory.is_some() => {
-                let Some(materializer) = self.working_directory_materializer.as_ref() else {
-                    return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
-                        WorkerExecutionOperation::Restore,
-                        "persisted worker has a working directory claim, but no materializer is configured for this runtime backend",
-                    ));
-                };
-                let working_directory =
-                    request.request.working_directory.as_ref().expect("checked");
+            };
+            for status in request.previous_workdir_attachments.clone() {
+                let relative_cwd = request
+                    .request
+                    .workdir_attachments
+                    .iter()
+                    .find(|claim| claim.alias == status.alias)
+                    .and_then(|claim| claim.relative_cwd.as_deref());
                 match materializer.bind_working_directory(
-                    &working_directory.working_directory_id,
-                    working_directory.relative_cwd.as_deref(),
+                    &status.working_directory.summary.working_directory_id,
+                    relative_cwd,
                 ) {
                     Ok(binding) => {
-                        request.working_directory = Some(binding.clone());
-                        Some(binding)
+                        if workdir_attachments
+                            .insert(status.alias.clone(), binding)
+                            .is_some()
+                        {
+                            return WorkerExecutionSpawnResult::Rejected(
+                                WorkerExecutionResult::rejected(
+                                    WorkerExecutionOperation::Restore,
+                                    format!(
+                                        "duplicate persisted Workdir attachment alias `{}`",
+                                        status.alias
+                                    ),
+                                ),
+                            );
+                        }
                     }
                     Err(error) => {
                         return WorkerExecutionSpawnResult::Rejected(
@@ -2384,8 +2508,43 @@ where
                     }
                 }
             }
-            None => None,
-        };
+        } else if !request.request.workdir_attachments.is_empty() {
+            let Some(materializer) = self.working_directory_materializer.as_ref() else {
+                return WorkerExecutionSpawnResult::Rejected(WorkerExecutionResult::rejected(
+                    WorkerExecutionOperation::Restore,
+                    "persisted Worker has Workdir claims, but no materializer is configured for this Runtime backend",
+                ));
+            };
+            for claim in request.request.workdir_attachments.clone() {
+                match materializer.bind_working_directory(
+                    &claim.working_directory_id,
+                    claim.relative_cwd.as_deref(),
+                ) {
+                    Ok(binding) => {
+                        if workdir_attachments
+                            .insert(claim.alias.clone(), binding)
+                            .is_some()
+                        {
+                            return WorkerExecutionSpawnResult::Rejected(
+                                WorkerExecutionResult::rejected(
+                                    WorkerExecutionOperation::Restore,
+                                    format!("duplicate Workdir attachment alias `{}`", claim.alias),
+                                ),
+                            );
+                        }
+                    }
+                    Err(error) => {
+                        return WorkerExecutionSpawnResult::Rejected(
+                            WorkerExecutionResult::rejected(
+                                WorkerExecutionOperation::Restore,
+                                error.to_string(),
+                            ),
+                        );
+                    }
+                }
+            }
+        }
+        request.workdir_attachments = workdir_attachments.clone();
 
         let factory = self.factory.clone();
         let bridge_context = request.context.clone();
@@ -2405,7 +2564,7 @@ where
                     ),
                     handle: None,
                     worker_state: None,
-                    working_directory: None,
+                    workdir_attachments: Vec::new(),
                 };
             }
         };
@@ -2417,7 +2576,7 @@ where
             controller.handle,
             controller.shutdown,
             controller.controller_task,
-            working_directory,
+            workdir_attachments,
             Some(controller.workspace_client),
         )
     }
@@ -2739,8 +2898,8 @@ mod tests {
     use crate::Runtime as EmbeddedRuntime;
     use crate::catalog::{
         ConfigBundleRef, CreateWorkerRequest, MaterializerKind, ProfileSelector,
-        RepositorySelector, WorkingDirectoryClaim, WorkingDirectoryRepository,
-        WorkingDirectoryRequest, WorkspaceApiRef,
+        RepositorySelector, WorkingDirectoryAttachmentClaim, WorkingDirectoryAttachmentRequest,
+        WorkingDirectoryRepository, WorkingDirectoryRequest, WorkspaceApiRef,
     };
     use crate::execution::WorkerExecutionContext;
     use crate::identity::WorkerId;
@@ -3279,18 +3438,17 @@ mod tests {
                 FsStore::new(&self.store_dir).map_err(|err| err.to_string())?,
                 FsWorkerStore::new(&self.worker_metadata_dir).map_err(|err| err.to_string())?,
             );
-            let filesystem_authority = request
-                .working_directory
-                .as_ref()
+            let only_workdir = (request.workdir_attachments.len() == 1)
+                .then(|| request.workdir_attachments.values().next())
+                .flatten();
+            let filesystem_authority = only_workdir
                 .map(|binding| {
                     let cwd = binding.cwd().to_path_buf();
                     self.observed_cwds.lock().unwrap().push(cwd.clone());
                     WorkerFilesystemAuthority::local(binding.root().to_path_buf(), cwd)
                 })
                 .unwrap_or(WorkerFilesystemAuthority::None);
-            let scope_root = request
-                .working_directory
-                .as_ref()
+            let scope_root = only_workdir
                 .map(|binding| binding.root().to_path_buf())
                 .unwrap_or_else(|| self.cwd.clone());
             let workspace_backend_ref = RuntimeWorkspaceBackendRef::from_worker_request(
@@ -3348,7 +3506,7 @@ mod tests {
                 request: request.request,
                 workspace_scope: request.workspace_scope,
                 context: request.context,
-                working_directory: request.working_directory,
+                workdir_attachments: request.workdir_attachments,
                 config_bundle: request.config_bundle,
             };
             self.spawn_controller(request).await
@@ -3513,8 +3671,8 @@ mod tests {
                 digest: bundle.metadata.digest,
             }),
             initial_input: None,
-            working_directory_request: None,
-            working_directory: None,
+            workdir_attachment_requests: Vec::new(),
+            workdir_attachments: Vec::new(),
             worker_observation_enabled: false,
             worker_observation_grants: Vec::new(),
             workspace_api: None,
@@ -3595,6 +3753,7 @@ mod tests {
                 source_fingerprint: "sha256:test".to_string(),
                 selector: Some(RepositorySelector::from("HEAD")),
             },
+            display_name: None,
             materializer: MaterializerKind::RuntimeGitClone,
             backend_workdir_id: None,
             materialization: None,
@@ -3698,7 +3857,7 @@ mod tests {
             request: create_request("1"),
             workspace_scope: None,
             context: test_execution_context(worker_ref),
-            working_directory: None,
+            workdir_attachments: BTreeMap::new(),
             config_bundle: None,
         };
 
@@ -3830,8 +3989,8 @@ mod tests {
                     "server-main",
                 )),
                 context: test_execution_context(worker_ref),
-                previous_working_directory: None,
-                working_directory: None,
+                previous_workdir_attachments: Vec::new(),
+                workdir_attachments: BTreeMap::new(),
                 config_bundle: None,
             })
             .await
@@ -3920,8 +4079,8 @@ mod tests {
                 request: create_request("embedded restore"),
                 workspace_scope: None,
                 context: test_execution_context(worker_ref),
-                previous_working_directory: None,
-                working_directory: None,
+                previous_workdir_attachments: Vec::new(),
+                workdir_attachments: BTreeMap::new(),
                 config_bundle: None,
             })
             .await
@@ -3988,7 +4147,7 @@ mod tests {
             &[
                 "WorkerBootstrap::new(",
                 ".prepare()",
-                "worker.bind_workdir_session(",
+                "worker.bind_workdir_sessions(",
                 "worker.bind_worker_observation_provider(",
                 "install_runtime_flow_transition_feature()",
                 "prepared.start()",
@@ -3998,7 +4157,7 @@ mod tests {
             restore,
             &[
                 "Worker::restore_from_worker_metadata_with_context(",
-                "worker.bind_workdir_session(",
+                "worker.bind_workdir_sessions(",
                 "worker.bind_worker_observation_provider(",
                 "install_runtime_flow_transition_feature()",
                 "PreparedWorker::new(",
@@ -4354,7 +4513,10 @@ mod tests {
                 .unwrap();
         runtime.store_config_bundle(test_bundle()).unwrap();
         let mut request = create_request("chat");
-        request.working_directory_request = Some(working_directory_request(repo.path()));
+        request.workdir_attachment_requests = vec![WorkingDirectoryAttachmentRequest {
+            alias: workdir::WorkdirAttachmentAlias::new("checkout").unwrap(),
+            working_directory: working_directory_request(repo.path()),
+        }];
 
         let detail = runtime.create_worker(request).unwrap();
         runtime
@@ -4376,7 +4538,7 @@ mod tests {
             );
         }
 
-        assert!(detail.working_directory.is_some());
+        assert_eq!(detail.workdir_attachments.len(), 1);
         let cwds = observed_cwds.lock().unwrap();
         assert_eq!(cwds.len(), 1);
         let cwd = &cwds[0];
@@ -4387,6 +4549,71 @@ mod tests {
             observed_workspace_clients.lock().unwrap().as_slice(),
             &[("unavailable".to_string(), None, false)]
         );
+
+        let workdir_id = detail.workdir_attachments[0]
+            .working_directory
+            .summary
+            .working_directory_id
+            .clone();
+        let second = runtime.create_worker(create_request("second")).unwrap();
+        let conflict = runtime
+            .replace_worker_workdir_attachments(
+                &second.worker_ref,
+                vec![WorkingDirectoryAttachmentClaim {
+                    alias: workdir::WorkdirAttachmentAlias::new("conflict").unwrap(),
+                    working_directory_id: workdir_id.clone(),
+                    relative_cwd: None,
+                }],
+            )
+            .unwrap_err();
+        assert!(matches!(
+            conflict,
+            crate::error::RuntimeError::InvalidRequest(_)
+        ));
+        let inactive = runtime
+            .create_working_directory(working_directory_request(repo.path()))
+            .unwrap();
+        let inactive_id = inactive.summary.working_directory_id;
+        runtime.cleanup_working_directory(&inactive_id).unwrap();
+        let inactive_error = runtime
+            .replace_worker_workdir_attachments(
+                &second.worker_ref,
+                vec![WorkingDirectoryAttachmentClaim {
+                    alias: workdir::WorkdirAttachmentAlias::new("inactive").unwrap(),
+                    working_directory_id: inactive_id,
+                    relative_cwd: None,
+                }],
+            )
+            .unwrap_err();
+        assert!(matches!(
+            inactive_error,
+            crate::error::RuntimeError::InvalidRequest(_)
+                | crate::error::RuntimeError::WorkingDirectory(_)
+        ));
+
+        let detached = runtime
+            .replace_worker_workdir_attachments(&detail.worker_ref, Vec::new())
+            .unwrap();
+        assert!(detached.workdir_attachments.is_empty());
+        runtime.stop_worker(&detail.worker_ref, None).unwrap();
+        let restored_without_workdir = runtime.restore_worker(&detail.worker_ref).unwrap();
+        assert!(restored_without_workdir.workdir_attachments.is_empty());
+
+        let alias = workdir::WorkdirAttachmentAlias::new("restored").unwrap();
+        runtime
+            .replace_worker_workdir_attachments(
+                &detail.worker_ref,
+                vec![WorkingDirectoryAttachmentClaim {
+                    alias: alias.clone(),
+                    working_directory_id: workdir_id,
+                    relative_cwd: None,
+                }],
+            )
+            .unwrap();
+        runtime.stop_worker(&detail.worker_ref, None).unwrap();
+        let stopped = runtime.worker_detail(&detail.worker_ref).unwrap();
+        assert_eq!(stopped.workdir_attachments.len(), 1);
+        assert_eq!(stopped.workdir_attachments[0].alias, alias);
     }
 
     #[test]
@@ -4620,12 +4847,13 @@ mod tests {
                 .unwrap();
         runtime.store_config_bundle(test_bundle()).unwrap();
         let mut request = create_request("chat");
-        request.working_directory_request = Some(working_directory_request(repo.path()));
+        request.workdir_attachment_requests = vec![WorkingDirectoryAttachmentRequest {
+            alias: workdir::WorkdirAttachmentAlias::new("checkout").unwrap(),
+            working_directory: working_directory_request(repo.path()),
+        }];
         let detail = runtime.create_worker(request).unwrap();
-        let workdir_id = detail
+        let workdir_id = detail.workdir_attachments[0]
             .working_directory
-            .as_ref()
-            .unwrap()
             .summary
             .working_directory_id
             .clone();
@@ -4642,7 +4870,6 @@ mod tests {
             crate::catalog::WorkingDirectoryStatusKind::Active
         );
         assert_eq!(status.summary.cleanliness.as_deref(), Some("clean"));
-        assert_eq!(status.summary.primary_worker_id, None);
     }
 
     #[test]
@@ -4663,10 +4890,11 @@ mod tests {
         let clone_root = materialized_clone_root(runtime_base.path(), &workdir_id);
         assert!(clone_root.join("README.md").exists());
         let mut request = create_request("chat");
-        request.working_directory = Some(WorkingDirectoryClaim {
+        request.workdir_attachments = vec![WorkingDirectoryAttachmentClaim {
+            alias: workdir::WorkdirAttachmentAlias::new("workdir").unwrap(),
             working_directory_id: workdir_id.clone(),
             relative_cwd: None,
-        });
+        }];
 
         let error = runtime.create_worker(request).unwrap_err();
 
@@ -4691,7 +4919,17 @@ mod tests {
                 .unwrap();
         runtime.store_config_bundle(test_bundle()).unwrap();
         let mut request = create_request("chat");
-        request.working_directory_request = Some(working_directory_request(repo.path()));
+        let second_repo = create_clean_repo();
+        request.workdir_attachment_requests = vec![
+            WorkingDirectoryAttachmentRequest {
+                alias: workdir::WorkdirAttachmentAlias::new("checkout").unwrap(),
+                working_directory: working_directory_request(repo.path()),
+            },
+            WorkingDirectoryAttachmentRequest {
+                alias: workdir::WorkdirAttachmentAlias::new("docs").unwrap(),
+                working_directory: working_directory_request(second_repo.path()),
+            },
+        ];
 
         let error = runtime.create_worker(request).unwrap_err();
 
@@ -4708,4 +4946,41 @@ mod tests {
         assert_eq!(remaining_workdirs, 0);
         assert!(!working_directories_root.join(".repository-cache").exists());
     }
+
+    #[test]
+    fn second_materialization_failure_rolls_back_first_attachment() {
+        let runtime_base = tempfile::tempdir().unwrap();
+        let repo = create_clean_repo();
+        let missing_repo = runtime_base.path().join("missing-repository");
+        let backend = WorkerRuntimeExecutionBackend::new(FailingFactory)
+            .unwrap()
+            .with_working_directory_materializer(RuntimeGitMaterializer::new(runtime_base.path()));
+        let runtime =
+            EmbeddedRuntime::with_execution_backend(RuntimeOptions::default(), Arc::new(backend))
+                .unwrap();
+        runtime.store_config_bundle(test_bundle()).unwrap();
+        let mut request = create_request("chat");
+        request.workdir_attachment_requests = vec![
+            WorkingDirectoryAttachmentRequest {
+                alias: workdir::WorkdirAttachmentAlias::new("checkout").unwrap(),
+                working_directory: working_directory_request(repo.path()),
+            },
+            WorkingDirectoryAttachmentRequest {
+                alias: workdir::WorkdirAttachmentAlias::new("docs").unwrap(),
+                working_directory: working_directory_request(&missing_repo),
+            },
+        ];
+
+        let error = runtime.create_worker(request).unwrap_err();
+        assert!(format!("{error:?}").contains("repository"));
+        let remaining_workdirs = fs::read_dir(runtime_base.path())
+            .map(|entries| {
+                entries
+                    .flatten()
+                    .filter(|entry| !entry.file_name().to_string_lossy().starts_with('.'))
+                    .count()
+            })
+            .unwrap_or(0);
+        assert_eq!(remaining_workdirs, 0);
+    }
 }

crates/worker-runtime/src/working_directory.rs

@@ -57,6 +57,8 @@ pub struct WorkingDirectoryEvidence {
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub struct WorkingDirectory {
     pub id: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub display_name: Option<String>,
     pub repository_id: String,
     pub materializer_kind: MaterializerKind,
     pub evidence: WorkingDirectoryEvidence,
@@ -68,6 +70,7 @@ impl WorkingDirectory {
     pub fn status_summary(&self) -> WorkingDirectorySummary {
         WorkingDirectorySummary {
             working_directory_id: self.id.clone(),
+            display_name: self.display_name.clone(),
             repository_id: self.repository_id.clone(),
             creation_selector: self.evidence.requested_selector.clone(),
             creation_ref: Some(self.evidence.resolved_commit.clone()),
@@ -80,7 +83,6 @@ impl WorkingDirectory {
             cleanup_target: Some(self.cleanup_target.clone()),
             status: self.status.clone(),
             cleanliness: None,
-            primary_worker_id: None,
             occupied_by: None,
         }
     }
@@ -717,6 +719,7 @@ impl RuntimeGitMaterializer {
         WorkingDirectoryStatus {
             summary: WorkingDirectorySummary {
                 working_directory_id: working_directory_id.to_string(),
+                display_name: None,
                 repository_id: "unknown".to_string(),
                 creation_selector: None,
                 creation_ref: None,
@@ -733,7 +736,6 @@ impl RuntimeGitMaterializer {
                 }),
                 status: WorkingDirectoryStatusKind::Corrupted,
                 cleanliness: Some("unknown".to_string()),
-                primary_worker_id: None,
                 occupied_by: None,
             },
         }
@@ -1072,6 +1074,7 @@ impl RuntimeGitMaterializer {
         let context = request.materialization.as_ref();
         let working_directory = WorkingDirectory {
             id: working_directory_id.clone(),
+            display_name: request.display_name.clone(),
             repository_id: request.repository.id.clone(),
             materializer_kind: MaterializerKind::RuntimeGitClone,
             evidence: WorkingDirectoryEvidence {
@@ -1211,6 +1214,7 @@ impl WorkingDirectoryMaterializer for RuntimeGitMaterializer {
 
         let working_request = WorkingDirectoryRequest {
             repository: request.repository.clone(),
+            display_name: None,
             materializer: MaterializerKind::RuntimeGitClone,
             backend_workdir_id: None,
             materialization: request.materialization.clone(),
@@ -3316,6 +3320,7 @@ mod tests {
                 source_fingerprint: "sha256:test".to_string(),
                 selector: Some(RepositorySelector::from("HEAD")),
             },
+            display_name: None,
             materializer: MaterializerKind::RuntimeGitClone,
             backend_workdir_id: None,
             materialization: None,

crates/worker/src/bootstrap.rs

@@ -145,7 +145,7 @@ where
         .map_err(WorkerBootstrapError::Worker)?;
 
         if let Some(workdir_session) = self.workdir_session {
-            worker.bind_workdir_session(Some(workdir_session));
+            worker.bind_single_workdir_session(Some(workdir_session));
         }
         Ok(PreparedWorker::new(worker, self.layout, self.transport))
     }
@@ -168,7 +168,7 @@ where
             .map_err(WorkerBootstrapError::Worker)?;
 
         if let Some(workdir_session) = self.workdir_session {
-            worker.bind_workdir_session(Some(workdir_session));
+            worker.bind_single_workdir_session(Some(workdir_session));
         }
         Ok(PreparedWorker::new(worker, self.layout, self.transport))
     }
@@ -222,7 +222,7 @@ where
     C: LlmClient + Clone + 'static,
     St: Store + WorkerMetadataStore + Clone + Send + Sync + 'static,
 {
-    let cleanup_session = worker.workdir_session().cloned();
+    let cleanup_sessions = worker.workdir_sessions();
     let controller = match layout {
         WorkerBootstrapLayout::Direct {
             runtime_base,
@@ -257,10 +257,7 @@ where
             controller_task,
         }),
         Err(source) => {
-            let cleanup_failed = match cleanup_session {
-                Some(session) => session.close().await.is_err(),
-                None => false,
-            };
+            let cleanup_failed = cleanup_sessions.close_all().await.is_err();
             Err(WorkerBootstrapError::Controller {
                 source,
                 cleanup_failed,

crates/worker/src/compact/metrics_tracker.rs

@@ -2,9 +2,8 @@
 //! Engine callbacks (which run synchronously and cannot themselves
 //! perform `async` store writes).
 //!
-//! Worker drains this buffer in `persist_turn` and writes each metric via
-//! `session_metrics::record_metric`, alongside the regular `LlmUsage`
-//! entries.
+//! Worker drains this buffer at the next successful request accounting
+//! boundary, with terminal `persist_turn` as a fallback.
 
 use std::sync::Mutex;
 
@@ -21,12 +20,12 @@ impl MetricsTracker {
         }
     }
 
-    /// Queue a metric for the next `persist_turn` flush.
+    /// Queue a metric for the next request or terminal accounting flush.
     pub(crate) fn push(&self, metric: Metric) {
         self.pending.lock().unwrap().push(metric);
     }
 
-    /// Drain all queued metrics. Called by Worker after a run completes.
+    /// Drain all queued metrics at an accounting boundary.
     pub(crate) fn drain(&self) -> Vec<Metric> {
         std::mem::take(&mut *self.pending.lock().unwrap())
     }

crates/worker/src/compact/usage_tracker.rs

@@ -7,17 +7,24 @@
 //! - **`on_usage` callback** (sync closure): receives the aggregated final
 //!   `UsageEvent` for that request after the stream completes.
 //!
-//! Pairing the two yields one `UsageRecord` per LLM call. Worker drains them
-//! in `persist_turn` and writes them as `LogEntry::LlmUsage` entries.
+//! Pairing the two yields one `UsageRecord` per LLM call. Worker commits
+//! successful requests from the assistant-turn boundary and uses terminal
+//! `persist_turn` only for records that have not already crossed that boundary.
 //!
 //! Multiple LLM calls per Worker run (tool loop) are supported: each call
 //! produces its own `(history_len, UsageEvent)` pair, and the records are
 //! buffered in chronological order.
 
+use std::collections::VecDeque;
 use std::sync::Mutex;
 
 use agen::UsageRecord;
 use agen::timeline::event::UsageEvent;
+use session_metrics::Metric;
+use session_store::{LogEntry, StoreError, segment_log};
+
+use crate::compact::state::CompactState;
+use crate::compact::telemetry::correlated_post_request_metric;
 
 /// The metric emitted after the next measured provider request.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -41,11 +48,15 @@ pub(crate) struct PostRequestLink {
     pub(crate) metric: PostRequestMetric,
 }
 
-/// One drained measurement and its causal metric links.
+/// One measured request and its causal metric links.
 #[derive(Debug, Clone)]
 pub(crate) struct RecordedUsage {
     pub(crate) record: UsageRecord,
     pub(crate) post_requests: Vec<PostRequestLink>,
+    /// True only when the provider stream completed normally and reported an
+    /// input occupancy. Partial/error/cancelled streams remain billable usage
+    /// records, but cannot satisfy a post-compaction rearm.
+    pub(crate) completed_with_occupancy: bool,
 }
 
 #[derive(Debug, Clone, Default, PartialEq, Eq)]
@@ -56,29 +67,52 @@ pub(crate) struct UsageSnapshot {
     pub(crate) output_tokens: u64,
 }
 
+#[derive(Debug)]
+struct PendingRequest {
+    id: u64,
+    history_len: usize,
+    usage_recorded: bool,
+}
+
+#[derive(Debug)]
+struct PendingRecordedUsage {
+    request_id: u64,
+    has_input_occupancy: bool,
+    usage: RecordedUsage,
+}
+
+#[derive(Debug, Default)]
+struct UsageTrackerState {
+    next_request_id: u64,
+    pending_request: Option<PendingRequest>,
+    pending_correlations: Vec<PostRequestLink>,
+    pending_records: VecDeque<PendingRecordedUsage>,
+}
+
 /// Shared between the pre-request hook, the `on_usage` callback, and Worker.
 pub(crate) struct UsageTracker {
-    /// `history.len()` captured at the most recent `pre_llm_request`.
-    /// Cleared when paired with an incoming `on_usage` event.
-    pending_history_len: Mutex<Option<usize>>,
-    /// Optional causal link consumed by the next measured request.
-    pending_correlations: Mutex<Vec<PostRequestLink>>,
-    /// Records accumulated during the current run; drained by Worker.
-    pending_records: Mutex<Vec<RecordedUsage>>,
+    state: Mutex<UsageTrackerState>,
 }
 
 impl UsageTracker {
     pub(crate) fn new() -> Self {
         Self {
-            pending_history_len: Mutex::new(None),
-            pending_correlations: Mutex::new(Vec::new()),
-            pending_records: Mutex::new(Vec::new()),
+            state: Mutex::new(UsageTrackerState::default()),
         }
     }
 
     /// Called from a `pre_llm_request` hook with the current history length.
+    /// Replacing an older pending request classifies that request as incomplete;
+    /// any partial usage already recorded for it remains available for billing.
     pub(crate) fn note_request(&self, history_len: usize) {
-        *self.pending_history_len.lock().unwrap() = Some(history_len);
+        let mut state = self.state.lock().unwrap();
+        let id = state.next_request_id;
+        state.next_request_id = state.next_request_id.wrapping_add(1);
+        state.pending_request = Some(PendingRequest {
+            id,
+            history_len,
+            usage_recorded: false,
+        });
     }
 
     /// Pair a prune event with the next provider request.
@@ -92,25 +126,31 @@ impl UsageTracker {
     }
 
     fn note_post_request(&self, id: String, metric: PostRequestMetric) {
-        let mut pending = self.pending_correlations.lock().unwrap();
-        pending.retain(|link| link.metric != metric);
-        pending.push(PostRequestLink {
+        let mut state = self.state.lock().unwrap();
+        state
+            .pending_correlations
+            .retain(|link| link.metric != metric);
+        state.pending_correlations.push(PostRequestLink {
             correlation_id: id,
             metric,
         });
     }
 
     /// Called from the `on_usage` callback with the aggregated final
-    /// UsageEvent. If a `history_len` was previously stashed via
-    /// `note_request`, builds a `RecordedUsage` and pushes it onto the
-    /// buffer. If not (e.g. test code that fires Usage outside a request),
-    /// drops the event.
+    /// UsageEvent. The record remains associated with the current request until
+    /// [`Self::request_completed`] proves that the provider stream completed
+    /// normally. Error/cancel paths still retain the measurement for billing.
     pub(crate) fn record_usage(&self, event: &UsageEvent) {
-        let history_len = match self.pending_history_len.lock().unwrap().take() {
-            Some(n) => n,
-            None => return,
+        let mut state = self.state.lock().unwrap();
+        let Some(pending) = state.pending_request.as_mut() else {
+            return;
         };
-        let post_requests = std::mem::take(&mut *self.pending_correlations.lock().unwrap());
+        if pending.usage_recorded {
+            return;
+        }
+        pending.usage_recorded = true;
+        let request_id = pending.id;
+        let history_len = pending.history_len;
         // UsageEvent.input_tokens は scheme 層で「占有量（プロンプト全長）」に
         // 正規化済みである前提（Anthropic は cache_read + cache_creation を
         // 加算して emit する）。
@@ -118,35 +158,166 @@ impl UsageTracker {
         let cache_read = event.cache_read_input_tokens.unwrap_or(0);
         let cache_write = event.cache_creation_input_tokens.unwrap_or(0);
         let output = event.output_tokens.unwrap_or(0);
-        self.pending_records.lock().unwrap().push(RecordedUsage {
-            record: UsageRecord {
-                history_len,
-                input_total_tokens: input_total,
-                cache_read_tokens: cache_read,
-                cache_write_tokens: cache_write,
-                output_tokens: output,
+        state.pending_records.push_back(PendingRecordedUsage {
+            request_id,
+            has_input_occupancy: event.input_tokens.is_some(),
+            usage: RecordedUsage {
+                record: UsageRecord {
+                    history_len,
+                    input_total_tokens: input_total,
+                    cache_read_tokens: cache_read,
+                    cache_write_tokens: cache_write,
+                    output_tokens: output,
+                },
+                post_requests: Vec::new(),
+                completed_with_occupancy: false,
             },
-            post_requests,
         });
     }
 
-    /// Return a clone of the accumulated `UsageRecord`s without clearing them.
+    /// Mark the current request as normally completed. A post-request causal
+    /// link is consumed only when that exact request also reported a valid
+    /// input occupancy; callbacks from partial/error/cancelled streams cannot
+    /// rearm the compaction guard.
+    pub(crate) fn request_completed(&self) {
+        let mut state = self.state.lock().unwrap();
+        let Some(pending) = state.pending_request.take() else {
+            return;
+        };
+        let Some(recorded_index) = state
+            .pending_records
+            .iter()
+            .rposition(|recorded| recorded.request_id == pending.id)
+        else {
+            return;
+        };
+        let has_occupancy = state.pending_records[recorded_index].has_input_occupancy;
+        if !has_occupancy {
+            return;
+        }
+        let post_requests = std::mem::take(&mut state.pending_correlations);
+        let recorded = &mut state.pending_records[recorded_index].usage;
+        recorded.completed_with_occupancy = true;
+        recorded.post_requests = post_requests;
+    }
+
+    /// Return a clone of accumulated measurements without clearing them.
     /// Used by request-time circuit breakers that need the same occupancy
     /// projection as Worker persistence while the run is still active.
     pub(crate) fn records(&self) -> Vec<UsageRecord> {
-        self.pending_records
+        self.state
             .lock()
             .unwrap()
+            .pending_records
             .iter()
-            .map(|r| r.record.clone())
+            .map(|r| r.usage.record.clone())
             .collect()
     }
 
-    /// Drain accumulated records. Called by Worker after a run completes,
-    /// before persisting the turn.
-    pub(crate) fn drain(&self) -> Vec<RecordedUsage> {
-        std::mem::take(&mut *self.pending_records.lock().unwrap())
+    /// Number of measurements that have not crossed the durable commit
+    /// boundary. Session rewrites must not activate a replacement Segment while
+    /// this is non-zero, because their history coordinates belong to the current
+    /// Segment.
+    pub(crate) fn pending_record_count(&self) -> usize {
+        self.state.lock().unwrap().pending_records.len()
     }
+
+    /// Remove the oldest measurement for one durable commit attempt.
+    pub(crate) fn take_next(&self) -> Option<RecordedUsage> {
+        self.state
+            .lock()
+            .unwrap()
+            .pending_records
+            .pop_front()
+            .map(|recorded| recorded.usage)
+    }
+
+    /// Restore a measurement after its durable commit failed.
+    pub(crate) fn restore_front(&self, usage: RecordedUsage) {
+        self.state
+            .lock()
+            .unwrap()
+            .pending_records
+            .push_front(PendingRecordedUsage {
+                // Persist ordering is the only remaining identity requirement.
+                request_id: u64::MAX,
+                has_input_occupancy: usage.completed_with_occupancy,
+                usage,
+            });
+    }
+
+    /// Drain accumulated records at a terminal Worker boundary.
+    pub(crate) fn drain(&self) -> Vec<RecordedUsage> {
+        let mut state = self.state.lock().unwrap();
+        state.pending_request = None;
+        state
+            .pending_records
+            .drain(..)
+            .map(|recorded| recorded.usage)
+            .collect()
+    }
+}
+
+/// Commit all currently measured usage records in request order.
+///
+/// A record is removed from the tracker only after its `LlmUsage` append
+/// succeeds. This is the single accounting boundary shared by the in-run
+/// interceptor and terminal `persist_turn`, preventing both loss on append
+/// failure and duplicate terminal writes. Correlated metrics are handed to the
+/// same commit boundary so they stay on the usage record's Segment; the return
+/// value is only useful as test/diagnostic evidence and must not be re-emitted.
+pub(crate) fn persist_pending_usage(
+    tracker: &UsageTracker,
+    usage_history: &Mutex<Vec<UsageRecord>>,
+    compact_state: Option<&CompactState>,
+    mut commit: impl FnMut(LogEntry, &mut dyn FnMut(), &[Metric]) -> Result<(), StoreError>,
+) -> Result<Vec<Metric>, StoreError> {
+    let mut metrics = Vec::new();
+    while let Some(recorded) = tracker.take_next() {
+        let RecordedUsage {
+            record,
+            post_requests,
+            completed_with_occupancy,
+        } = recorded;
+        let post_metrics = post_requests
+            .iter()
+            .map(|link| correlated_post_request_metric(link.metric, &link.correlation_id, &record))
+            .collect::<Vec<_>>();
+        let usage_entry = LogEntry::LlmUsage {
+            ts: segment_log::now_millis(),
+            history_len: record.history_len,
+            input_total_tokens: record.input_total_tokens,
+            cache_read_tokens: record.cache_read_tokens,
+            cache_write_tokens: record.cache_write_tokens,
+            output_tokens: record.output_tokens,
+        };
+        let mut publish_committed_usage = || {
+            usage_history
+                .lock()
+                .expect("usage_history poisoned")
+                .push(record.clone());
+
+            if completed_with_occupancy
+                && post_requests
+                    .iter()
+                    .any(|link| link.metric == PostRequestMetric::Compaction)
+            {
+                if let Some(state) = compact_state {
+                    state.post_compact_request_committed();
+                }
+            }
+        };
+        if let Err(error) = commit(usage_entry, &mut publish_committed_usage, &post_metrics) {
+            tracker.restore_front(RecordedUsage {
+                record,
+                post_requests,
+                completed_with_occupancy,
+            });
+            return Err(error);
+        }
+        metrics.extend(post_metrics);
+    }
+    Ok(metrics)
 }
 
 #[cfg(test)]
@@ -230,6 +401,7 @@ mod tests {
         tracker.note_correlation_id("prune-id".into());
         tracker.note_request(5);
         tracker.record_usage(&make_event(100, 10, 2, 20));
+        tracker.request_completed();
 
         let records = tracker.drain();
         assert_eq!(records[0].post_requests.len(), 2);
@@ -248,9 +420,11 @@ mod tests {
         tracker.note_correlation_id("abc".into());
         tracker.note_request(5);
         tracker.record_usage(&make_event(100, 0, 0, 20));
+        tracker.request_completed();
         // Next request without a fresh stash → no correlation_id.
         tracker.note_request(10);
         tracker.record_usage(&make_event(200, 50, 0, 30));
+        tracker.request_completed();
 
         let records = tracker.drain();
         assert_eq!(records.len(), 2);
@@ -259,4 +433,130 @@ mod tests {
         assert_eq!(records[0].post_requests[0].metric, PostRequestMetric::Prune);
         assert!(records[1].post_requests.is_empty());
     }
+
+    #[test]
+    fn partial_usage_does_not_consume_post_compact_link() {
+        let tracker = UsageTracker::new();
+        tracker.note_compaction_correlation_id("compact-id".into());
+        tracker.note_request(5);
+        tracker.record_usage(&make_event(90, 0, 0, 2));
+
+        // Starting another request proves the prior stream did not complete.
+        tracker.note_request(6);
+        tracker.record_usage(&make_event(100, 0, 0, 3));
+        tracker.request_completed();
+
+        let records = tracker.drain();
+        assert_eq!(records.len(), 2);
+        assert!(!records[0].completed_with_occupancy);
+        assert!(records[0].post_requests.is_empty());
+        assert!(records[1].completed_with_occupancy);
+        assert_eq!(records[1].post_requests.len(), 1);
+        assert_eq!(records[1].post_requests[0].correlation_id, "compact-id");
+    }
+
+    #[test]
+    fn completed_request_without_input_occupancy_does_not_consume_link() {
+        let tracker = UsageTracker::new();
+        tracker.note_compaction_correlation_id("compact-id".into());
+        tracker.note_request(5);
+        let mut missing_input = make_event(0, 0, 0, 2);
+        missing_input.input_tokens = None;
+        tracker.record_usage(&missing_input);
+        tracker.request_completed();
+
+        tracker.note_request(6);
+        tracker.record_usage(&make_event(100, 0, 0, 3));
+        tracker.request_completed();
+
+        let records = tracker.drain();
+        assert!(!records[0].completed_with_occupancy);
+        assert!(records[0].post_requests.is_empty());
+        assert!(records[1].completed_with_occupancy);
+        assert_eq!(records[1].post_requests[0].correlation_id, "compact-id");
+    }
+
+    #[test]
+    fn completed_request_without_usage_does_not_complete_previous_partial_record() {
+        let tracker = UsageTracker::new();
+        tracker.note_compaction_correlation_id("compact-id".into());
+        tracker.note_request(5);
+        tracker.record_usage(&make_event(90, 0, 0, 2));
+
+        tracker.note_request(6);
+        tracker.request_completed();
+
+        let records = tracker.drain();
+        assert_eq!(records.len(), 1);
+        assert!(!records[0].completed_with_occupancy);
+        assert!(records[0].post_requests.is_empty());
+    }
+
+    #[test]
+    fn failed_commit_can_restore_record_without_reordering() {
+        let tracker = UsageTracker::new();
+        tracker.note_request(1);
+        tracker.record_usage(&make_event(10, 0, 0, 1));
+        tracker.request_completed();
+        tracker.note_request(2);
+        tracker.record_usage(&make_event(20, 0, 0, 2));
+        tracker.request_completed();
+
+        let first = tracker.take_next().expect("first record");
+        tracker.restore_front(first);
+        let records = tracker.drain();
+        assert_eq!(records.len(), 2);
+        assert_eq!(records[0].record.input_total_tokens, 10);
+        assert_eq!(records[1].record.input_total_tokens, 20);
+    }
+
+    #[test]
+    fn compaction_rearms_only_after_usage_append_succeeds() {
+        use crate::compact::state::{AutomaticCompactDecision, CompactionOutcome};
+
+        let tracker = UsageTracker::new();
+        let state = CompactState::new(None, Some(10), 0);
+        assert!(matches!(
+            state.evaluate_request(11),
+            AutomaticCompactDecision::Start(_)
+        ));
+        assert!(state.complete_automatic(CompactionOutcome::Succeeded));
+
+        tracker.note_compaction_correlation_id("compact-id".into());
+        tracker.note_request(1);
+        tracker.record_usage(&make_event(5, 0, 0, 1));
+        tracker.request_completed();
+        let usage_history = Mutex::new(Vec::new());
+
+        let error = persist_pending_usage(&tracker, &usage_history, Some(&state), |_, _, _| {
+            Err(StoreError::Io(std::io::Error::other("synthetic failure")))
+        })
+        .expect_err("usage append must fail");
+        assert!(error.to_string().contains("synthetic failure"));
+        assert!(usage_history.lock().unwrap().is_empty());
+        assert!(matches!(
+            state.evaluate_request(11),
+            AutomaticCompactDecision::Block(_)
+        ));
+
+        let mut entries = Vec::new();
+        let metrics = persist_pending_usage(
+            &tracker,
+            &usage_history,
+            Some(&state),
+            |entry, after_commit, _post_metrics| {
+                entries.push(entry);
+                after_commit();
+                Ok(())
+            },
+        )
+        .expect("retry should commit");
+        assert_eq!(entries.len(), 1);
+        assert_eq!(usage_history.lock().unwrap().len(), 1);
+        assert_eq!(metrics.len(), 1);
+        assert!(matches!(
+            state.evaluate_request(11),
+            AutomaticCompactDecision::Start(_)
+        ));
+    }
 }

crates/worker/src/controller.rs

@@ -617,7 +617,7 @@ impl WorkerController {
         C: LlmClient + Clone + 'static,
         St: Store + WorkerMetadataStore + Clone + Send + Sync + 'static,
     {
-        let session = worker.workdir_session().cloned();
+        let sessions = worker.workdir_sessions();
         let result = Self::spawn_initialized(
             worker,
             runtime_base,
@@ -628,10 +628,9 @@ impl WorkerController {
         )
         .await;
         if result.is_err()
-            && let Some(session) = session
-            && let Err(error) = session.close().await
+            && let Err(error) = sessions.close_all().await
         {
-            tracing::warn!(%error, "Workdir session close after controller startup failure failed");
+            tracing::warn!(%error, "Workdir sessions close after controller startup failure failed");
         }
         result
     }
@@ -1144,7 +1143,7 @@ pub(crate) async fn register_worker_tools<C, St>(
     runtime_base: PathBuf,
     spawned_registry: Arc<SpawnedWorkerRegistry>,
     parent_method_tx: Option<mpsc::WeakSender<Method>>,
-    inherited_workdir_tool_broker: Option<workdir::WorkdirToolBroker>,
+    inherited_workdir_tool_broker: Option<workdir::WorkdirToolBrokerRouter>,
 ) -> std::io::Result<Option<workdir::WorkdirSessionHandle>>
 where
     C: LlmClient + Clone + 'static,
@@ -1153,26 +1152,13 @@ where
     // Worker-immutable snapshots taken before the mutable worker borrow
     // below so the worker borrow doesn't conflict with reads on `worker`.
     let feature_config = worker.manifest().feature.clone();
-    let mut workdir_tool_broker = inherited_workdir_tool_broker;
-    if feature_config.manage_workdir.enabled && worker.workdir_session().is_none() {
-        let workspace_client = worker.workspace_client_handle();
-        let broker = workdir::WorkdirToolBroker::new(
-            crate::feature::builtin::manage_workdir::WorkspaceAttachedWorkdirSession::handle(
-                workspace_client,
-            ),
-        );
-        worker.bind_workdir_session(Some(broker.tool_session()));
-        workdir_tool_broker = Some(broker);
-    } else if workdir_tool_broker.is_none()
-        && let Some(existing) = worker.workdir_session().cloned()
-    {
-        let broker = workdir::WorkdirToolBroker::new(existing);
-        worker.bind_workdir_session(Some(broker.tool_session()));
-        workdir_tool_broker = Some(broker);
-    }
-    let worker_workdir = workdir_tool_broker
-        .as_ref()
-        .map(workdir::WorkdirToolBroker::tool_session);
+    let workdir_sessions = worker.workdir_sessions();
+    let restrict_workdir_tools_to_current_capabilities = inherited_workdir_tool_broker.is_some();
+    let workdir_tool_broker = Some(
+        inherited_workdir_tool_broker
+            .unwrap_or_else(|| workdir::WorkdirToolBrokerRouter::new(workdir_sessions.clone())),
+    );
+    let workdir_for_view = workdir_sessions.only_session();
     let local_filesystem = worker.local_working_directory().cloned();
     let local_workspace_root = local_filesystem.as_ref().map(|local| local.root.clone());
     let task_feature = worker.task_feature();
@@ -1207,28 +1193,29 @@ where
             paste_store,
             paste_session_id,
         ));
-    // Resolve the existing Worker–Workdir binding into the domain provider.
-    // Tools only consume the provider handle; they do not own its root, cwd,
-    // scope, or lifecycle. No-workdir Workers expose no local tools.
-    let (workdir_for_view, tracker) = if let Some(workdir) = worker_workdir {
-        let tracker = tools::Tracker::new();
+    // Keep the alias-routed schemas installed for the Worker lifetime. The
+    // attachment set may be empty or mutate after registration, so target
+    // resolution and provider capability checks happen per invocation.
+    let tracker = tools::Tracker::new();
+    let workdir_tools = if restrict_workdir_tools_to_current_capabilities {
+        tools::routed_builtin_tools_for_current_capabilities(
+            workdir_sessions.clone(),
+            tracker.clone(),
+            bash_output_dir.clone(),
+        )
+    } else {
+        tools::routed_builtin_tools(
+            workdir_sessions.clone(),
+            tracker.clone(),
+            bash_output_dir.clone(),
+        )
+    };
+    worker.engine_mut().register_tools(workdir_tools);
+    if feature_config.image.enabled && model_supports_image_attachments(&spawner_manifest.model) {
         worker
             .engine_mut()
-            .register_tools(tools::core_builtin_tools(
-                workdir.clone(),
-                tracker.clone(),
-                bash_output_dir.clone(),
-            ));
-        if feature_config.image.enabled && model_supports_image_attachments(&spawner_manifest.model)
-        {
-            worker
-                .engine_mut()
-                .register_tool(tools::view_image_tool(workdir.clone()));
-        }
-        (Some(workdir), Some(tracker))
-    } else {
-        (None, None)
-    };
+            .register_tool(tools::routed_view_image_tool(workdir_sessions));
+    }
     if feature_config.web.enabled {
         worker
             .engine_mut()
@@ -1344,6 +1331,7 @@ where
         feature_registry.add_module(
             crate::feature::builtin::manage_workdir::ManageWorkdirFeature::with_child_lifecycle(
                 workspace_client,
+                worker.workdir_sessions(),
                 Arc::new(move || {
                     let child_registry = shutdown_registry.clone();
                     Box::pin(async move { child_registry.shutdown_internal().await })
@@ -1485,9 +1473,7 @@ where
     if let Some((resident_summary, system_prompt_override)) = memory_prompt_contribution {
         worker.install_system_prompt_contribution(resident_summary, system_prompt_override);
     }
-    if let Some(tracker) = tracker {
-        worker.attach_tracker(tracker);
-    }
+    worker.attach_tracker(tracker);
     Ok(workdir_for_view)
 }
 
@@ -2610,14 +2596,13 @@ async fn controller_loop<C, St>(
         }
     }
 
-    if let Some(session) = worker.workdir_session() {
-        loop {
-            match session.close().await {
-                Ok(()) => break,
-                Err(error) => {
-                    tracing::warn!(%error, "Workdir session close failed; retrying");
-                    tokio::time::sleep(std::time::Duration::from_millis(100)).await;
-                }
+    let sessions = worker.workdir_sessions();
+    while !sessions.is_empty() {
+        match sessions.close_all().await {
+            Ok(()) => break,
+            Err(error) => {
+                tracing::warn!(%error, "Workdir session set close failed; retrying");
+                tokio::time::sleep(std::time::Duration::from_millis(100)).await;
             }
         }
     }

crates/worker/src/feature/builtin/manage_workdir.rs

@@ -52,9 +52,9 @@ const DETACH_TOOL: &str = "WorkdirDetach";
 const DELETE_TOOL: &str = "WorkdirDelete";
 
 const LIST_DESCRIPTION: &str = "List persistent Workdirs in the current Workspace through Backend Workspace API authority. The result contains safe summaries and diagnostics, never host paths or Runtime connection details.";
-const CREATE_DESCRIPTION: &str = "Materialize a persistent Workdir on a selected Runtime from a Workspace repository and optional selector. This does not change this Worker's attachment; use WorkdirAttach explicitly after creation.";
-const ATTACH_DESCRIPTION: &str = "Attach this Worker to one existing Workdir. The Backend enforces one active Workdir per Worker and one active Worker per Workdir, then opens an ephemeral operation session.";
-const DETACH_DESCRIPTION: &str = "Detach this Worker from its active Workdir and release Workdir occupancy. Any ephemeral operation session is closed.";
+const CREATE_DESCRIPTION: &str = "Materialize a persistent Workdir with an optional human-facing display name on a selected Runtime from a Workspace repository and optional selector. The display name is independent of attachment aliases. This does not change this Worker's attachment; use WorkdirAttach explicitly after creation.";
+const ATTACH_DESCRIPTION: &str = "Attach one existing Workdir to this Worker under a stable Worker-local alias. The Backend preserves one active Worker per Workdir while allowing this Worker to own multiple aliases.";
+const DETACH_DESCRIPTION: &str = "Detach one Workdir attachment by its Worker-local alias. Active operations, commands, or Internal SubWorkers cause safe rejection rather than implicit authority loss.";
 pub(crate) type BeforeWorkdirRelease =
     Arc<dyn Fn() -> Pin<Box<dyn Future<Output = std::io::Result<()>> + Send>> + Send + Sync>;
 pub(crate) type AfterWorkdirAttach = Arc<dyn Fn() + Send + Sync>;
@@ -64,6 +64,7 @@ const DELETE_DESCRIPTION: &str = "Request removal of one persistent Workdir by i
 #[derive(Clone)]
 pub struct ManageWorkdirFeature {
     client: Arc<dyn WorkspaceClient>,
+    session_router: Arc<workdir::WorkdirSessionRouter>,
     before_workdir_release: Option<BeforeWorkdirRelease>,
     after_workdir_attach: Option<AfterWorkdirAttach>,
 }
@@ -82,6 +83,7 @@ impl ManageWorkdirFeature {
     pub fn new(client: Arc<dyn WorkspaceClient>) -> Self {
         Self {
             client,
+            session_router: Arc::new(workdir::WorkdirSessionRouter::new()),
             before_workdir_release: None,
             after_workdir_attach: None,
         }
@@ -89,11 +91,13 @@ impl ManageWorkdirFeature {
 
     pub(crate) fn with_child_lifecycle(
         client: Arc<dyn WorkspaceClient>,
+        session_router: Arc<workdir::WorkdirSessionRouter>,
         before_workdir_release: BeforeWorkdirRelease,
         after_workdir_attach: AfterWorkdirAttach,
     ) -> Self {
         Self {
             client,
+            session_router,
             before_workdir_release: Some(before_workdir_release),
             after_workdir_attach: Some(after_workdir_attach),
         }
@@ -116,10 +120,12 @@ impl FeatureModule for ManageWorkdirFeature {
     }
 
     fn install(&self, context: &mut FeatureInstallContext<'_>) -> Result<(), FeatureInstallError> {
-        let backend = WorkspaceHttpWorkdirBackend::new(self.client.clone()).with_child_lifecycle(
-            self.before_workdir_release.clone(),
-            self.after_workdir_attach.clone(),
-        );
+        let backend = WorkspaceHttpWorkdirBackend::new(self.client.clone())
+            .with_session_router(self.session_router.clone())
+            .with_child_lifecycle(
+                self.before_workdir_release.clone(),
+                self.after_workdir_attach.clone(),
+            );
         for (name, definition) in [
             (
                 LIST_TOOL,
@@ -183,6 +189,8 @@ impl FeatureModule for ManageWorkdirFeature {
 #[derive(Clone)]
 struct WorkspaceHttpWorkdirBackend {
     client: Arc<dyn WorkspaceClient>,
+    session_router: Arc<workdir::WorkdirSessionRouter>,
+    attachment_mutation_lock: Arc<tokio::sync::Mutex<()>>,
     before_workdir_release: Option<BeforeWorkdirRelease>,
     after_workdir_attach: Option<AfterWorkdirAttach>,
 }
@@ -205,14 +213,27 @@ impl std::fmt::Debug for WorkspaceHttpWorkdirBackend {
 #[derive(Debug)]
 pub struct WorkspaceAttachedWorkdirSession {
     client: Arc<dyn WorkspaceClient>,
+    target_workdir: String,
     workdir: Workdir,
 }
 
 impl WorkspaceAttachedWorkdirSession {
-    pub fn handle(client: Arc<dyn WorkspaceClient>) -> WorkdirSessionHandle {
+    pub fn handle(
+        client: Arc<dyn WorkspaceClient>,
+        target_workdir: impl Into<String>,
+    ) -> WorkdirSessionHandle {
+        Self::handle_for_workdir(client, target_workdir, "workspace-attachment")
+    }
+
+    pub fn handle_for_workdir(
+        client: Arc<dyn WorkspaceClient>,
+        target_workdir: impl Into<String>,
+        workdir_id: impl Into<String>,
+    ) -> WorkdirSessionHandle {
         Arc::new(Self {
             client,
-            workdir: Workdir::new("workspace-attachment"),
+            target_workdir: target_workdir.into(),
+            workdir: Workdir::new(workdir_id),
         })
     }
 
@@ -229,13 +250,15 @@ impl WorkspaceAttachedWorkdirSession {
                 "/api/w/{}/workers/self/workdir-session/operations",
                 encode_path_segment(workspace_id)
             ),
-            serde_json::to_string(&WorkspaceWorkdirSessionOperationRequest { operation }).map_err(
-                |error| {
-                    WorkdirError::Transport(format!(
-                        "failed to encode Workspace Workdir operation: {error}"
-                    ))
-                },
-            )?,
+            serde_json::to_string(&WorkspaceWorkdirSessionOperationRequest {
+                target_workdir: self.target_workdir.clone(),
+                operation,
+            })
+            .map_err(|error| {
+                WorkdirError::Transport(format!(
+                    "failed to encode Workspace Workdir operation: {error}"
+                ))
+            })?,
         );
         let response = self
             .client
@@ -399,11 +422,18 @@ impl WorkspaceHttpWorkdirBackend {
     fn new(client: Arc<dyn WorkspaceClient>) -> Self {
         Self {
             client,
+            session_router: Arc::new(workdir::WorkdirSessionRouter::new()),
+            attachment_mutation_lock: Arc::new(tokio::sync::Mutex::new(())),
             before_workdir_release: None,
             after_workdir_attach: None,
         }
     }
 
+    fn with_session_router(mut self, session_router: Arc<workdir::WorkdirSessionRouter>) -> Self {
+        self.session_router = session_router;
+        self
+    }
+
     fn with_child_lifecycle(
         mut self,
         before_workdir_release: Option<BeforeWorkdirRelease>,
@@ -449,10 +479,12 @@ impl WorkspaceHttpWorkdirBackend {
             .transpose()?;
         let repository_key =
             validate_identity(&input.repository_key, CREATE_TOOL, "repository_key")?;
+        let display_name = validate_optional_display_name(input.display_name)?;
         let selector = validate_optional_selector(input.selector)?;
         let workspace_id = encode_path_segment(self.workspace_id()?);
         let request = WorkdirCreateRequest {
             runtime_id: runtime_id.map(str::to_string),
+            display_name,
             repository_key: repository_key.to_string(),
             selector,
             operation_id: Some(operation_id),
@@ -472,32 +504,71 @@ impl WorkspaceHttpWorkdirBackend {
     }
 
     fn attach(&self, input: WorkdirAttachInput) -> Result<ToolOutput, ToolError> {
-        let workdir_id = validate_identity(&input.workdir_id, ATTACH_TOOL, "workdir_id")?;
-        let response = self.attach_response(workdir_id)?;
-        workdir_output(format!("Attached to Workdir {workdir_id}"), &response)
+        let alias = validate_identity(&input.alias, ATTACH_TOOL, "alias")?;
+        workdir::WorkdirAttachmentAlias::new(alias)
+            .map_err(|error| ToolError::InvalidArgument(error.to_string()))?;
+        let working_directory_id = validate_identity(
+            &input.working_directory_id,
+            ATTACH_TOOL,
+            "working_directory_id",
+        )?;
+        let alias_key = workdir::WorkdirAttachmentAlias::new(alias)
+            .map_err(|error| ToolError::InvalidArgument(error.to_string()))?;
+        if self.session_router.session(&alias_key).is_some() {
+            return Err(ToolError::InvalidArgument(format!(
+                "attachment alias `{alias}` already exists"
+            )));
+        }
+        let response = self.attach_response(alias, working_directory_id)?;
+        if let Err(error) = self.session_router.attach(
+            alias_key.clone(),
+            WorkspaceAttachedWorkdirSession::handle_for_workdir(
+                self.client.clone(),
+                alias,
+                working_directory_id,
+            ),
+        ) {
+            let _ = self.detach(alias);
+            return Err(ToolError::ExecutionFailed(format!(
+                "attach Workdir session route: {error}"
+            )));
+        }
+        workdir_output(
+            format!("Attached Workdir {working_directory_id} as {alias}"),
+            &response,
+        )
     }
 
-    fn attach_response(&self, workdir_id: &str) -> Result<WorkdirAttachmentResponse, ToolError> {
+    fn attach_response(
+        &self,
+        alias: &str,
+        working_directory_id: &str,
+    ) -> Result<WorkdirAttachmentResponse, ToolError> {
         let workspace_id = encode_path_segment(self.workspace_id()?);
         self.execute_json::<WorkdirAttachmentResponse>(WorkspaceRequest::json(
             WorkspaceRequestMethod::Post,
-            format!("/api/w/{workspace_id}/workers/self/workdir-attachment"),
+            format!("/api/w/{workspace_id}/workers/self/workdir-attachments"),
             serde_json::to_string(&WorkdirAttachRequest {
-                workdir_id: workdir_id.to_string(),
+                alias: alias.to_string(),
+                working_directory_id: working_directory_id.to_string(),
             })
             .map_err(decode_error)?,
         ))
     }
 
-    fn detach(&self) -> Result<ToolOutput, ToolError> {
+    fn detach(&self, alias: &str) -> Result<ToolOutput, ToolError> {
         let workspace_id = encode_path_segment(self.workspace_id()?);
+        let alias_path = encode_path_segment(alias);
         let response = self.execute_json::<WorkdirAttachmentResponse>(WorkspaceRequest {
             method: WorkspaceRequestMethod::Delete,
-            path: format!("/api/w/{workspace_id}/workers/self/workdir-attachment"),
+            path: format!("/api/w/{workspace_id}/workers/self/workdir-attachments/{alias_path}"),
             body: None,
         })?;
         workdir_output(
-            format!("Detached from Workdir {}", response.workdir_id),
+            format!(
+                "Detached Workdir {} ({})",
+                response.working_directory_id, response.alias
+            ),
             &response,
         )
     }
@@ -590,6 +661,7 @@ impl Tool for WorkspaceHttpWorkdirTool {
                 ctx.call_id.to_string(),
             ),
             WorkdirOperation::Attach => {
+                let _mutation_guard = self.backend.attachment_mutation_lock.lock().await;
                 let result = self
                     .backend
                     .attach(parse_input::<WorkdirAttachInput>(input_json)?);
@@ -601,15 +673,41 @@ impl Tool for WorkspaceHttpWorkdirTool {
                 result
             }
             WorkdirOperation::Detach => {
-                let _input = parse_input::<WorkdirDetachInput>(input_json)?;
-                if let Some(before_release) = &self.backend.before_workdir_release {
-                    before_release().await.map_err(|error| {
+                let _mutation_guard = self.backend.attachment_mutation_lock.lock().await;
+                let input = parse_input::<WorkdirDetachInput>(input_json)?;
+                let alias = validate_identity(&input.alias, DETACH_TOOL, "alias")?;
+                let alias_key = workdir::WorkdirAttachmentAlias::new(alias)
+                    .map_err(|error| ToolError::InvalidArgument(error.to_string()))?;
+                self.backend
+                    .session_router
+                    .begin_detach(&alias_key)
+                    .await
+                    .map_err(|error| ToolError::ExecutionFailed(error.to_string()))?;
+                if let Some(before_release) = &self.backend.before_workdir_release
+                    && let Err(error) = before_release().await
+                {
+                    self.backend.session_router.cancel_detach(&alias_key);
+                    return Err(ToolError::ExecutionFailed(format!(
+                        "stop Internal SubWorkers before Workdir detach: {error}"
+                    )));
+                }
+                let result = match self.backend.detach(alias) {
+                    Ok(result) => result,
+                    Err(error) => {
+                        self.backend.session_router.cancel_detach(&alias_key);
+                        return Err(error);
+                    }
+                };
+                self.backend
+                    .session_router
+                    .finish_detach(&alias_key)
+                    .await
+                    .map_err(|error| {
                         ToolError::ExecutionFailed(format!(
-                            "stop Internal SubWorkers before Workdir detach: {error}"
+                            "detach Workdir session route after Backend release: {error}"
                         ))
                     })?;
-                }
-                self.backend.detach()
+                Ok(result)
             }
             WorkdirOperation::Delete => self
                 .backend
@@ -672,6 +770,25 @@ fn validate_delete_reason(reason: &str) -> Result<&str, ToolError> {
     Ok(reason)
 }
 
+fn validate_optional_display_name(
+    display_name: Option<String>,
+) -> Result<Option<String>, ToolError> {
+    let Some(display_name) = display_name else {
+        return Ok(None);
+    };
+    let display_name = display_name.trim();
+    if display_name.is_empty()
+        || display_name.len() > 80
+        || display_name.chars().any(char::is_control)
+    {
+        return Err(ToolError::InvalidArgument(
+            "WorkdirCreate display_name must be non-empty, contain no control characters, and be at most 80 bytes"
+                .to_string(),
+        ));
+    }
+    Ok(Some(display_name.to_string()))
+}
+
 fn validate_optional_selector(selector: Option<String>) -> Result<Option<String>, ToolError> {
     let Some(selector) = selector else {
         return Ok(None);
@@ -725,6 +842,7 @@ fn create_schema() -> serde_json::Value {
         "required": ["repository_key"],
         "properties": {
             "runtime_id": {"type": ["string", "null"], "minLength": 1},
+            "display_name": {"type": ["string", "null"], "minLength": 1, "maxLength": 80},
             "repository_key": {"type": "string", "minLength": 1},
             "selector": {"type": ["string", "null"], "minLength": 1}
         }
@@ -735,15 +853,23 @@ fn attach_schema() -> serde_json::Value {
     json!({
         "type": "object",
         "additionalProperties": false,
-        "required": ["workdir_id"],
+        "required": ["alias", "working_directory_id"],
         "properties": {
-            "workdir_id": {"type": "string", "minLength": 1}
+            "alias": {"type": "string", "minLength": 1, "maxLength": 64},
+            "working_directory_id": {"type": "string", "minLength": 1}
         }
     })
 }
 
 fn detach_schema() -> serde_json::Value {
-    list_schema()
+    json!({
+        "type": "object",
+        "additionalProperties": false,
+        "required": ["alias"],
+        "properties": {
+            "alias": {"type": "string", "minLength": 1, "maxLength": 64}
+        }
+    })
 }
 
 fn delete_schema() -> serde_json::Value {
@@ -767,6 +893,8 @@ struct WorkdirListInput {}
 struct WorkdirCreateInput {
     #[serde(default)]
     runtime_id: Option<String>,
+    #[serde(default)]
+    display_name: Option<String>,
     repository_key: String,
     #[serde(default)]
     selector: Option<String>,
@@ -775,22 +903,27 @@ struct WorkdirCreateInput {
 #[derive(Debug, Deserialize)]
 #[serde(deny_unknown_fields)]
 struct WorkdirAttachInput {
-    workdir_id: String,
+    alias: String,
+    working_directory_id: String,
 }
 
 #[derive(Debug, Deserialize)]
 #[serde(deny_unknown_fields)]
-struct WorkdirDetachInput {}
+struct WorkdirDetachInput {
+    alias: String,
+}
 
 #[derive(Debug, Serialize)]
 struct WorkdirAttachRequest {
-    workdir_id: String,
+    alias: String,
+    working_directory_id: String,
 }
 
 #[derive(Debug, Serialize, Deserialize, PartialEq, Eq)]
 struct WorkdirAttachmentResponse {
     workspace_id: String,
-    workdir_id: String,
+    alias: String,
+    working_directory_id: String,
     attached: bool,
 }
 
@@ -1021,7 +1154,10 @@ mod tests {
         );
         assert!(create["properties"].get("path").is_none());
         assert!(create["properties"].get("session_id").is_none());
-        assert_eq!(attach_schema()["required"], json!(["workdir_id"]));
+        assert_eq!(
+            attach_schema()["required"],
+            json!(["alias", "working_directory_id"])
+        );
         assert!(attach_schema()["properties"].get("session_id").is_none());
         assert_eq!(
             delete_schema()["required"],
@@ -1057,12 +1193,14 @@ mod tests {
             })),
             response(json!({
                 "workspace_id": "workspace/test",
-                "workdir_id": "wd-created",
+                "alias": "checkout",
+                "working_directory_id": "wd-created",
                 "attached": true
             })),
             response(json!({
                 "workspace_id": "workspace/test",
-                "workdir_id": "wd-created",
+                "alias": "checkout",
+                "working_directory_id": "wd-created",
                 "attached": false
             })),
             response(json!({
@@ -1089,6 +1227,7 @@ mod tests {
             .create(
                 WorkdirCreateInput {
                     runtime_id: Some("runtime/one".to_string()),
+                    display_name: Some("Review checkout".to_string()),
                     repository_key: "main".to_string(),
                     selector: Some("refs/heads/topic".to_string()),
                 },
@@ -1106,10 +1245,11 @@ mod tests {
         assert_eq!(client.requests().len(), 2);
         backend
             .attach(WorkdirAttachInput {
-                workdir_id: "wd-created".to_string(),
+                alias: "checkout".to_string(),
+                working_directory_id: "wd-created".to_string(),
             })
             .unwrap();
-        backend.detach().unwrap();
+        backend.detach("checkout").unwrap();
         backend
             .delete(WorkdirDeleteInput {
                 working_directory_id: "wd-created".to_string(),
@@ -1132,16 +1272,17 @@ mod tests {
             serde_json::from_str(requests[1].body.as_deref().unwrap()).unwrap();
         assert_eq!(body["repository_key"], "main");
         assert_eq!(body["runtime_id"], "runtime/one");
+        assert_eq!(body["display_name"], "Review checkout");
         assert_eq!(body["operation_id"], "call-create-1");
         assert_eq!(body["selector"], "refs/heads/topic");
         assert_eq!(
             requests[2].path,
-            "/api/w/workspace%2Ftest/workers/self/workdir-attachment"
+            "/api/w/workspace%2Ftest/workers/self/workdir-attachments"
         );
         assert_eq!(requests[2].method, WorkspaceRequestMethod::Post);
         assert_eq!(
             requests[3].path,
-            "/api/w/workspace%2Ftest/workers/self/workdir-attachment"
+            "/api/w/workspace%2Ftest/workers/self/workdir-attachments/checkout"
         );
         assert_eq!(requests[3].method, WorkspaceRequestMethod::Delete);
         assert_eq!(
@@ -1160,7 +1301,7 @@ mod tests {
             "operation": "stat",
             "result": {"path": "visible.txt", "kind": "file", "size": 8}
         }))]));
-        let session = WorkspaceAttachedWorkdirSession::handle(client.clone());
+        let session = WorkspaceAttachedWorkdirSession::handle(client.clone(), "workdir");
         let result = session
             .stat(StatRequest {
                 path: workdir::WorkdirPath::new("visible.txt").unwrap(),
@@ -1176,6 +1317,7 @@ mod tests {
         );
         let body: serde_json::Value =
             serde_json::from_str(requests[0].body.as_deref().unwrap()).unwrap();
+        assert_eq!(body["target_workdir"], "workdir");
         assert_eq!(body["operation"]["operation"], "stat");
         assert!(body.get("expected_session_fence").is_none());
         assert!(body.get("runtime_id").is_none());
@@ -1188,7 +1330,7 @@ mod tests {
             "operation": "command_start",
             "result": "command-1"
         }))]));
-        let session = WorkspaceAttachedWorkdirSession::handle(client.clone());
+        let session = WorkspaceAttachedWorkdirSession::handle(client.clone(), "workdir");
 
         let handle = session
             .start_command(CommandRequest {
@@ -1226,7 +1368,7 @@ mod tests {
             workdir::http::WorkdirTransportErrorCode::InvalidRequest,
             "Workdir operation request is invalid",
         )]));
-        let session = WorkspaceAttachedWorkdirSession::handle(client);
+        let session = WorkspaceAttachedWorkdirSession::handle(client, "workdir");
 
         let error = session
             .glob(workdir::GlobRequest {
@@ -1246,7 +1388,7 @@ mod tests {
             status: 502,
             body: "secret token and /host/private/path".to_string(),
         }]));
-        let session = WorkspaceAttachedWorkdirSession::handle(client);
+        let session = WorkspaceAttachedWorkdirSession::handle(client, "workdir");
 
         let error = session
             .stat(StatRequest {
@@ -1273,6 +1415,7 @@ mod tests {
         ]));
         let broker = workdir::WorkdirToolBroker::new(WorkspaceAttachedWorkdirSession::handle(
             client.clone(),
+            "workdir",
         ));
         let scoped = broker
             .scope(workdir::WorkdirToolScope {
@@ -1323,6 +1466,7 @@ mod tests {
             .create(
                 WorkdirCreateInput {
                     runtime_id: None,
+                    display_name: None,
                     repository_key: "main".to_string(),
                     selector: None,
                 },
@@ -1348,6 +1492,7 @@ mod tests {
             .create(
                 WorkdirCreateInput {
                     runtime_id: Some(" ".to_string()),
+                    display_name: None,
                     repository_key: "main".to_string(),
                     selector: None,
                 },
@@ -1363,9 +1508,17 @@ mod tests {
     async fn detach_stops_internal_subworkers_before_backend_release() {
         let client = Arc::new(RecordingWorkspaceClient::new(vec![response(json!({
             "workspace_id": "workspace/test",
-            "workdir_id": "wd-attached",
+            "alias": "checkout",
+            "working_directory_id": "wd-attached",
             "attached": false
         }))]));
+        let router = Arc::new(workdir::WorkdirSessionRouter::new());
+        router
+            .attach(
+                workdir::WorkdirAttachmentAlias::new("checkout").unwrap(),
+                WorkspaceAttachedWorkdirSession::handle(client.clone(), "workdir"),
+            )
+            .unwrap();
         let cleanup_calls = Arc::new(AtomicUsize::new(0));
         let cleanup_calls_for_guard = cleanup_calls.clone();
         let before_release: BeforeWorkdirRelease = Arc::new(move || {
@@ -1377,11 +1530,12 @@ mod tests {
         });
         let tool = WorkspaceHttpWorkdirTool {
             backend: WorkspaceHttpWorkdirBackend::new(client.clone())
+                .with_session_router(router)
                 .with_child_lifecycle(Some(before_release), None),
             operation: WorkdirOperation::Detach,
         };
 
-        tool.execute("{}", ToolExecutionContext::default())
+        tool.execute(r#"{"alias":"checkout"}"#, ToolExecutionContext::default())
             .await
             .unwrap();
 
@@ -1389,23 +1543,31 @@ mod tests {
         assert_eq!(client.requests().len(), 1);
         assert_eq!(
             client.requests()[0].path,
-            "/api/w/workspace%2Ftest/workers/self/workdir-attachment"
+            "/api/w/workspace%2Ftest/workers/self/workdir-attachments/checkout"
         );
     }
 
     #[tokio::test]
     async fn detach_does_not_release_backend_when_child_cleanup_fails() {
         let client = Arc::new(RecordingWorkspaceClient::new(Vec::new()));
+        let router = Arc::new(workdir::WorkdirSessionRouter::new());
+        router
+            .attach(
+                workdir::WorkdirAttachmentAlias::new("checkout").unwrap(),
+                WorkspaceAttachedWorkdirSession::handle(client.clone(), "workdir"),
+            )
+            .unwrap();
         let before_release: BeforeWorkdirRelease =
             Arc::new(|| Box::pin(async { Err(std::io::Error::other("child cleanup failed")) }));
         let tool = WorkspaceHttpWorkdirTool {
             backend: WorkspaceHttpWorkdirBackend::new(client.clone())
+                .with_session_router(router)
                 .with_child_lifecycle(Some(before_release), None),
             operation: WorkdirOperation::Detach,
         };
 
         let error = tool
-            .execute("{}", ToolExecutionContext::default())
+            .execute(r#"{"alias":"checkout"}"#, ToolExecutionContext::default())
             .await
             .unwrap_err();
 
@@ -1413,11 +1575,77 @@ mod tests {
         assert!(client.requests().is_empty());
     }
 
+    #[tokio::test]
+    async fn detach_reconciles_naturally_completed_workspace_command() {
+        let client = Arc::new(RecordingWorkspaceClient::new(vec![
+            response(json!({
+                "workspace_id": "workspace/test",
+                "alias": "checkout",
+                "working_directory_id": "wd-attached",
+                "attached": true
+            })),
+            response(json!({
+                "operation": "command_start",
+                "result": "command-1"
+            })),
+            response(json!({
+                "operation": "command_status",
+                "result": "completed"
+            })),
+            response(json!({
+                "workspace_id": "workspace/test",
+                "alias": "checkout",
+                "working_directory_id": "wd-attached",
+                "attached": false
+            })),
+        ]));
+        let backend = WorkspaceHttpWorkdirBackend::new(client.clone());
+        backend
+            .attach(WorkdirAttachInput {
+                alias: "checkout".to_string(),
+                working_directory_id: "wd-attached".to_string(),
+            })
+            .unwrap();
+        let alias = workdir::WorkdirAttachmentAlias::new("checkout").unwrap();
+        backend
+            .session_router
+            .session(&alias)
+            .unwrap()
+            .start_command(CommandRequest {
+                command: "printf done".to_string(),
+                timeout_secs: 5,
+                output_limit: 1024,
+                cwd: None,
+                spill_dir: None,
+                tool_call_id: None,
+            })
+            .await
+            .unwrap();
+        let tool = WorkspaceHttpWorkdirTool {
+            backend,
+            operation: WorkdirOperation::Detach,
+        };
+
+        tool.execute(r#"{"alias":"checkout"}"#, ToolExecutionContext::default())
+            .await
+            .unwrap();
+
+        let requests = client.requests();
+        assert_eq!(requests.len(), 4);
+        assert!(
+            requests[2]
+                .body
+                .as_deref()
+                .is_some_and(|body| body.contains("command_status"))
+        );
+    }
+
     #[tokio::test]
     async fn successful_attach_reopens_internal_subworker_admission() {
         let client = Arc::new(RecordingWorkspaceClient::new(vec![response(json!({
             "workspace_id": "workspace/test",
-            "workdir_id": "wd-attached",
+            "alias": "checkout",
+            "working_directory_id": "wd-attached",
             "attached": true
         }))]));
         let reopen_calls = Arc::new(AtomicUsize::new(0));
@@ -1432,7 +1660,7 @@ mod tests {
         };
 
         tool.execute(
-            r#"{"workdir_id":"wd-attached"}"#,
+            r#"{"alias":"checkout","working_directory_id":"wd-attached"}"#,
             ToolExecutionContext::default(),
         )
         .await

crates/worker/src/internal_worker.rs

@@ -165,7 +165,7 @@ where
     })?;
     worker.disable_manifest_lifecycle_features();
     if let Some(session) = inherited_workdir_session {
-        worker.bind_workdir_session(Some(session));
+        worker.bind_single_workdir_session(Some(session));
     }
 
     let install_report = worker.install_features(features);
@@ -608,7 +608,7 @@ pub(crate) async fn spawn_internal_worker_session(
     })?;
     worker.disable_manifest_lifecycle_features();
     if let Some(session) = inherited_workdir_session {
-        worker.bind_workdir_session(Some(session));
+        worker.bind_single_workdir_session(Some(session));
     }
     let install_report = worker.install_features(features);
     let installed_tools = install_report.installed_tool_names();
@@ -701,7 +701,7 @@ pub(crate) fn prepare_internal_worker_from_spec(
         })?;
         worker.disable_manifest_lifecycle_features();
         if let Some(session) = inherited_workdir_session {
-            worker.bind_workdir_session(Some(session));
+            worker.bind_single_workdir_session(Some(session));
         }
         let install_report = worker.install_features(features);
         let installed_tools = install_report.installed_tool_names();
@@ -772,7 +772,7 @@ pub(crate) async fn prepare_internal_worker_session(
     visibility: InternalWorkerVisibility,
     child_registry: Option<Arc<SpawnedWorkerRegistry>>,
     on_turn_end: Option<Arc<dyn Fn(InternalWorkerSessionStatus) + Send + Sync>>,
-    command_event_broker: Option<workdir::WorkdirToolBroker>,
+    command_event_broker: Option<workdir::WorkdirToolBrokerRouter>,
 ) -> Result<InternalWorkerSessionHandle, InternalWorkerSessionError> {
     let (event_tx, _event_rx) = broadcast::channel(256);
     let sink = worker.sink();
@@ -780,9 +780,14 @@ pub(crate) async fn prepare_internal_worker_session(
     let alerter = Alerter::new(event_tx.clone());
     let in_flight = InFlightEvents::new(event_tx.clone());
     if let Some(broker) = command_event_broker.as_ref() {
-        wire_workdir_command_events(&broker.tool_session(), &in_flight);
+        let sessions = broker.sessions();
+        for alias in sessions.aliases() {
+            if let Ok(selected) = sessions.resolve(Some(alias.as_str())) {
+                wire_workdir_command_events(&selected.session, &in_flight);
+            }
+        }
     } else if let Some(session) = worker.workdir_session() {
-        wire_workdir_command_events(session, &in_flight);
+        wire_workdir_command_events(&session, &in_flight);
     }
     let actor_in_flight = in_flight.clone();
     worker.attach_alerter(alerter.clone());

crates/worker/src/ipc/interceptor.rs

@@ -23,11 +23,12 @@ use agen::interceptor::{
 use agen::tool::ToolOutput;
 use arc_swap::ArcSwap;
 use async_trait::async_trait;
-use tracing::info;
+use tracing::{info, warn};
 
+use crate::compact::metrics_tracker::MetricsTracker;
 use crate::compact::state::{AutomaticCompactDecision, CompactState};
-use crate::compact::usage_tracker::UsageTracker;
-use session_store::SystemItem;
+use crate::compact::usage_tracker::{UsageTracker, persist_pending_usage};
+use session_store::{SystemItem, segment_log};
 
 use crate::hook::{
     HookEventKind, HookPostToolAction, HookPreRequestAction, HookPreToolAction, HookPromptAction,
@@ -81,6 +82,10 @@ pub(crate) struct WorkerInterceptor {
     /// persisted into `usage_history`. Subsequent tool-loop LLM calls must
     /// see these records during pre-request safety accounting.
     usage_tracker: Option<Arc<UsageTracker>>,
+    /// Metrics produced synchronously while projecting the request (notably
+    /// prune.fire/skip). Flushed before the matching request usage so metric
+    /// correlation order remains stable at the in-run commit boundary.
+    metrics_tracker: Option<Arc<MetricsTracker>>,
     /// Pending-notification buffer drained into `worker.history`
     /// via [`Self::pending_history_appends`] just before the next LLM
     /// request. The Engine `extend`s these into its persistent history
@@ -152,6 +157,7 @@ impl WorkerInterceptor {
             compact_state,
             usage_history,
             usage_tracker: None,
+            metrics_tracker: None,
             pending_notifies,
             pending_attachments,
             prompts,
@@ -168,6 +174,11 @@ impl WorkerInterceptor {
         self
     }
 
+    pub(crate) fn with_metrics_tracker(mut self, metrics_tracker: Arc<MetricsTracker>) -> Self {
+        self.metrics_tracker = Some(metrics_tracker);
+        self
+    }
+
     pub(crate) fn with_prompt_workspace_id(mut self, workspace_id: Option<String>) -> Self {
         self.prompt_workspace_id = workspace_id;
         self
@@ -272,6 +283,56 @@ impl WorkerInterceptor {
             }
         }
     }
+    fn try_persist_metric(writer: &Arc<dyn SystemItemCommitter>, metric: &session_metrics::Metric) {
+        let payload = serde_json::to_value(metric).expect("Metric is Serialize");
+        if writer
+            .commit_log_entry(session_store::LogEntry::Extension {
+                ts: segment_log::now_millis(),
+                domain: session_metrics::DOMAIN.into(),
+                payload,
+            })
+            .is_err()
+        {
+            warn!(name = %metric.name, "failed to record session metric; dropping");
+        }
+    }
+
+    fn persist_completed_request_usage(&self) -> InterceptorResult<()> {
+        let Some(tracker) = self.usage_tracker.as_ref() else {
+            return Ok(());
+        };
+        tracker.request_completed();
+
+        let (Some(writer), Some(usage_history)) =
+            (self.log_writer.as_ref(), self.usage_history.as_ref())
+        else {
+            // Low-level Worker tests may omit the type-erased writer. Their
+            // terminal persist_turn remains the durable fallback.
+            return Ok(());
+        };
+        if let Some(metrics_tracker) = self.metrics_tracker.as_ref() {
+            for metric in metrics_tracker.drain() {
+                Self::try_persist_metric(writer, &metric);
+            }
+        }
+
+        persist_pending_usage(
+            tracker,
+            usage_history,
+            self.compact_state.as_deref(),
+            |entry, after_commit, post_metrics| {
+                writer.commit_usage_boundary(entry, after_commit, post_metrics)
+            },
+        )
+        .map_err(|error| {
+            InterceptorError::new(
+                InterceptorErrorCategory::Dependency,
+                format!("usage persistence failed: {error}"),
+            )
+        })?;
+        Ok(())
+    }
+
     fn attach_prompt_provenance(&self, items: &mut [SystemItem]) {
         let prompts = self.prompts.load();
         let projection = prompts.projection();
@@ -596,6 +657,11 @@ impl Interceptor<SessionHistoryMetadata> for WorkerInterceptor {
         &self,
         context: AssistantTurnEndContext<'_, SessionHistoryMetadata>,
     ) -> InterceptorResult<TurnEndAction> {
+        // `on_assistant_turn_end` is reached only after a normal provider
+        // stream completed and its usage callback was flushed. Commit that
+        // exact request before tools can extend the same logical run.
+        self.persist_completed_request_usage()?;
+
         let history = context.history;
         let final_text_preview = history
             .iter()
@@ -752,6 +818,25 @@ mod tests {
         }
     }
 
+    struct FailingUsageCommitter {
+        attempts: Arc<AtomicUsize>,
+    }
+
+    impl SystemItemCommitter for FailingUsageCommitter {
+        fn commit_log_entry(
+            &self,
+            entry: session_store::LogEntry,
+        ) -> Result<(), session_store::StoreError> {
+            if matches!(entry, session_store::LogEntry::LlmUsage { .. }) {
+                self.attempts.fetch_add(1, Ordering::SeqCst);
+                return Err(session_store::StoreError::Io(std::io::Error::other(
+                    "synthetic usage failure",
+                )));
+            }
+            Ok(())
+        }
+    }
+
     struct AppendingPreRequestHook {
         saw_handle: Arc<AtomicBool>,
     }
@@ -955,6 +1040,68 @@ mod tests {
         );
     }
 
+    #[tokio::test]
+    async fn completed_request_usage_failure_stops_before_rearm() {
+        use crate::compact::state::{AutomaticCompactDecision, CompactionOutcome};
+
+        let registry = Arc::new(HookRegistryBuilder::new().build());
+        let state = Arc::new(CompactState::new(None, Some(10), 0));
+        assert!(matches!(
+            state.evaluate_request(11),
+            AutomaticCompactDecision::Start(_)
+        ));
+        assert!(state.complete_automatic(CompactionOutcome::Succeeded));
+
+        let usage_history = Arc::new(Mutex::new(Vec::new()));
+        let tracker = Arc::new(UsageTracker::new());
+        tracker.note_compaction_correlation_id("compact-id".into());
+        tracker.note_request(1);
+        tracker.record_usage(&agen::event::UsageEvent {
+            input_tokens: Some(5),
+            output_tokens: Some(1),
+            total_tokens: Some(6),
+            cache_read_input_tokens: Some(0),
+            cache_creation_input_tokens: Some(0),
+        });
+        let attempts = Arc::new(AtomicUsize::new(0));
+        let interceptor = WorkerInterceptor::new(
+            registry,
+            Some(Arc::clone(&state)),
+            Some(Arc::clone(&usage_history)),
+            NotifyBuffer::new(),
+            Arc::new(Mutex::new(Vec::new())),
+            test_prompts(),
+            Some(Arc::new(FailingUsageCommitter {
+                attempts: Arc::clone(&attempts),
+            })),
+        )
+        .with_usage_tracker(Arc::clone(&tracker));
+
+        let error = interceptor
+            .on_assistant_turn_end(AssistantTurnEndContext {
+                invocation: Default::default(),
+                assistant_entries: &[],
+                history: &[],
+                tool_calls: &[],
+            })
+            .await
+            .expect_err("usage storage failure must stop the request boundary");
+
+        assert_eq!(error.category(), InterceptorErrorCategory::Dependency);
+        assert!(error.diagnostic().contains("usage persistence failed"));
+        assert_eq!(attempts.load(Ordering::SeqCst), 1);
+        assert_eq!(
+            tracker.records().len(),
+            1,
+            "failed record must remain pending"
+        );
+        assert!(usage_history.lock().unwrap().is_empty());
+        assert!(matches!(
+            state.evaluate_request(11),
+            AutomaticCompactDecision::Block(_)
+        ));
+    }
+
     #[tokio::test]
     async fn pre_llm_request_counts_in_flight_usage_records() {
         let registry = Arc::new(HookRegistryBuilder::new().build());

crates/worker/src/spawn/registry.rs

@@ -27,7 +27,7 @@ use session_store::{
 };
 use tokio::sync::{Notify, broadcast};
 use tracing::warn;
-use workdir::WorkdirScopeLease;
+use workdir::WorkdirScopeLeaseSet;
 
 use crate::internal_worker::{InternalWorkerSessionHandle, InternalWorkerVisibility};
 use crate::runtime::dir::{RuntimeDir, SpawnedWorkerRecord};
@@ -70,7 +70,7 @@ pub(crate) struct SubWorkerStopSummary {
 pub(crate) struct InternalSpawnedWorkerRecord {
     pub worker_name: String,
     pub scope_delegated: Vec<ScopeRule>,
-    pub workdir_tool_scope: Arc<WorkdirScopeLease>,
+    pub workdir_tool_scope: Arc<WorkdirScopeLeaseSet>,
     #[cfg(test)]
     pub installed_tools: Arc<[String]>,
     pub session: InternalWorkerSessionHandle,
@@ -89,7 +89,7 @@ impl InternalSpawnedWorkerRecord {
     pub(crate) fn new(
         worker_name: String,
         scope_delegated: Vec<ScopeRule>,
-        workdir_tool_scope: WorkdirScopeLease,
+        workdir_tool_scope: WorkdirScopeLeaseSet,
         #[cfg(test)] installed_tools: Vec<String>,
         session: InternalWorkerSessionHandle,
         child_registry: Arc<SpawnedWorkerRegistry>,
@@ -1179,7 +1179,11 @@ mod tests {
             InternalSpawnedWorkerRecord::new(
                 name.into(),
                 Vec::new(),
-                delegation,
+                workdir::WorkdirScopeLeaseSet::from_single(
+                    workdir::WorkdirAttachmentAlias::new("workdir").unwrap(),
+                    delegation,
+                )
+                .unwrap(),
                 Vec::new(),
                 session,
                 registry(),

crates/worker/src/spawn/tool.rs

@@ -5,6 +5,7 @@
 //! in-process Internal Worker session actor. No Runtime Worker record, OS process, PID, Unix socket,
 //! or machine-wide child allocation is created.
 
+use std::collections::BTreeMap;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
@@ -22,7 +23,7 @@ use manifest::{
 use serde::Deserialize;
 use tokio::sync::mpsc;
 use workdir::{
-    WorkdirToolBroker, WorkdirToolScope, WorkdirToolScopePermission, WorkdirToolScopeRule,
+    WorkdirToolBrokerRouter, WorkdirToolScope, WorkdirToolScopePermission, WorkdirToolScopeRule,
 };
 
 use crate::PromptCatalogSource;
@@ -81,6 +82,10 @@ struct ReviewerHandoffInput {
 
 #[derive(Debug, Deserialize, schemars::JsonSchema)]
 struct ScopeRuleInput {
+    /// Worker-local alias of the parent Workdir attachment. May be omitted only
+    /// when the parent has exactly one attachment.
+    #[serde(default)]
+    target_workdir: Option<String>,
     /// Logical Workdir-relative target such as `.` or `src`. Absolute host
     /// paths and parent traversal are rejected.
     target: String,
@@ -310,7 +315,7 @@ pub struct SubWorkerSpawnTool {
     /// Directory the spawned SubWorker's tools should use when the LLM did not
     /// override it. Defaults to the spawner's cwd.
     /// Parent-owned broker for scoped Workdir tool execution.
-    workdir_tool_broker: Option<WorkdirToolBroker>,
+    workdir_tool_broker: Option<WorkdirToolBrokerRouter>,
     /// Parent-owned in-memory registry shared by the five SubWorker tools.
     registry: Arc<SpawnedWorkerRegistry>,
     /// Spawner's resolved Manifest. `profile = "inherit"` derives the
@@ -337,7 +342,7 @@ impl SubWorkerSpawnTool {
         runtime_base: PathBuf,
         bash_output_dir: PathBuf,
         workspace_root: PathBuf,
-        workdir_tool_broker: Option<WorkdirToolBroker>,
+        workdir_tool_broker: Option<WorkdirToolBrokerRouter>,
         registry: Arc<SpawnedWorkerRegistry>,
         spawner_manifest: WorkerManifest,
         prompt_loader: PromptCatalogSource,
@@ -428,14 +433,19 @@ impl Tool for SubWorkerSpawnTool {
                 ))
             })?;
         let workdir_tool_broker = require_workdir_tool_broker(self.workdir_tool_broker.as_ref())?;
-        let tool_scope = workdir_tool_scope(input.cwd.as_deref(), workdir_rules, input.command)?;
+        let tool_scopes = routed_workdir_tool_scopes(
+            workdir_tool_broker,
+            input.cwd.as_deref(),
+            workdir_rules,
+            input.command,
+        )?;
         let workdir_scope = workdir_tool_broker
-            .scope(tool_scope)
+            .scope(tool_scopes)
             .await
             .map_err(|error| {
                 ToolError::InvalidArgument(format!("scope parent-owned Workdir tools: {error}"))
             })?;
-        let child_workdir_tool_broker = workdir_scope.broker();
+        let child_workdir_tool_broker = workdir_scope.broker_router();
 
         let spawn_selector =
             parse_spawn_profile_selector(input.profile.as_deref()).map_err(|msg| {
@@ -537,6 +547,7 @@ impl Tool for SubWorkerSpawnTool {
                 ))
             })?;
         let child_scope = child.scope().clone();
+        child.bind_workdir_sessions(workdir_scope.session_router());
         let child_registry = SpawnedWorkerRegistry::new_internal(input.name.clone(), child_scope);
         register_worker_tools(
             &mut child,
@@ -717,22 +728,27 @@ fn logical_workdir_path(value: &str, field: &str) -> Result<FsPath, ToolError> {
     })
 }
 
-fn parse_workdir_scope(rules: &[ScopeRuleInput]) -> Result<Vec<WorkdirToolScopeRule>, ToolError> {
+fn parse_workdir_scope(
+    rules: &[ScopeRuleInput],
+) -> Result<Vec<(Option<String>, WorkdirToolScopeRule)>, ToolError> {
     if rules.is_empty() {
         return Err(ToolError::InvalidArgument("scope must not be empty".into()));
     }
     rules
         .iter()
         .map(|rule| {
-            Ok(WorkdirToolScopeRule {
-                target: logical_workdir_path(&rule.target, "scope.target")?,
-                permission: match rule.permission {
-                    PermissionInput::Read => WorkdirToolScopePermission::Read,
-                    PermissionInput::Write => WorkdirToolScopePermission::Write,
+            Ok((
+                rule.target_workdir.clone(),
+                WorkdirToolScopeRule {
+                    target: logical_workdir_path(&rule.target, "scope.target")?,
+                    permission: match rule.permission {
+                        PermissionInput::Read => WorkdirToolScopePermission::Read,
+                        PermissionInput::Write => WorkdirToolScopePermission::Write,
+                    },
+                    recursive: rule.recursive,
+                    symlink_policy: rule.symlink_policy.into(),
                 },
-                recursive: rule.recursive,
-                symlink_policy: rule.symlink_policy.into(),
-            })
+            ))
         })
         .collect()
 }
@@ -749,9 +765,28 @@ fn workdir_tool_scope(
     })
 }
 
+fn routed_workdir_tool_scopes(
+    broker: &WorkdirToolBrokerRouter,
+    cwd: Option<&str>,
+    rules: Vec<(Option<String>, WorkdirToolScopeRule)>,
+    command: bool,
+) -> Result<Vec<(workdir::WorkdirAttachmentAlias, WorkdirToolScope)>, ToolError> {
+    let mut grouped = BTreeMap::<workdir::WorkdirAttachmentAlias, Vec<WorkdirToolScopeRule>>::new();
+    for (target_workdir, rule) in rules {
+        let alias = broker
+            .resolve_alias(target_workdir.as_deref())
+            .map_err(|error| ToolError::InvalidArgument(error.to_string()))?;
+        grouped.entry(alias).or_default().push(rule);
+    }
+    grouped
+        .into_iter()
+        .map(|(alias, rules)| workdir_tool_scope(cwd, rules, command).map(|scope| (alias, scope)))
+        .collect()
+}
+
 fn require_workdir_tool_broker(
-    broker: Option<&WorkdirToolBroker>,
-) -> Result<&WorkdirToolBroker, ToolError> {
+    broker: Option<&WorkdirToolBrokerRouter>,
+) -> Result<&WorkdirToolBrokerRouter, ToolError> {
     broker.ok_or_else(|| {
         ToolError::InvalidArgument(
             "SubWorkerSpawn requires parent-owned Workdir tools; attach a Workdir before granting filesystem access"
@@ -992,7 +1027,7 @@ pub(crate) fn sub_worker_spawn_tool(
     runtime_base: PathBuf,
     bash_output_dir: PathBuf,
     workspace_root: PathBuf,
-    workdir_tool_broker: Option<WorkdirToolBroker>,
+    workdir_tool_broker: Option<WorkdirToolBrokerRouter>,
     registry: Arc<SpawnedWorkerRegistry>,
     spawner_manifest: WorkerManifest,
     prompts: Arc<ArcSwap<PromptCatalog>>,
@@ -1018,7 +1053,7 @@ fn sub_worker_spawn_tool_impl(
     runtime_base: PathBuf,
     bash_output_dir: PathBuf,
     workspace_root: PathBuf,
-    workdir_tool_broker: Option<WorkdirToolBroker>,
+    workdir_tool_broker: Option<WorkdirToolBrokerRouter>,
     registry: Arc<SpawnedWorkerRegistry>,
     spawner_manifest: WorkerManifest,
     prompts: Arc<ArcSwap<PromptCatalog>>,
@@ -1096,12 +1131,14 @@ mod tests {
     fn workdir_scope_uses_logical_relative_paths() {
         let rules = parse_workdir_scope(&[
             ScopeRuleInput {
+                target_workdir: None,
                 target: ".".to_string(),
                 permission: PermissionInput::Read,
                 recursive: true,
                 symlink_policy: Default::default(),
             },
             ScopeRuleInput {
+                target_workdir: Some("checkout".to_string()),
                 target: "src".to_string(),
                 permission: PermissionInput::Write,
                 recursive: false,
@@ -1109,12 +1146,14 @@ mod tests {
             },
         ])
         .unwrap();
-        assert_eq!(rules[0].target.as_str(), "");
-        assert_eq!(rules[1].target.as_str(), "src");
-        assert_eq!(rules[0].symlink_policy, SymlinkPolicy::Resolved);
-        assert_eq!(rules[1].symlink_policy, SymlinkPolicy::Logical);
+        assert_eq!(rules[0].1.target.as_str(), "");
+        assert_eq!(rules[1].0.as_deref(), Some("checkout"));
+        assert_eq!(rules[1].1.target.as_str(), "src");
+        assert_eq!(rules[0].1.symlink_policy, SymlinkPolicy::Resolved);
+        assert_eq!(rules[1].1.symlink_policy, SymlinkPolicy::Logical);
         for target in ["/host/path", "../escape"] {
             let error = parse_workdir_scope(&[ScopeRuleInput {
+                target_workdir: None,
                 target: target.to_string(),
                 permission: PermissionInput::Read,
                 recursive: true,
@@ -1278,15 +1317,17 @@ enabled = false
         let fail_requests = Arc::new(AtomicBool::new(false));
         let prompt_loader = PromptCatalogSource::builtins_only();
         let (parent_method_tx, mut parent_method_rx) = mpsc::channel(8);
-        let workdir_tool_broker = workdir::WorkdirToolBroker::new(Arc::new(
-            workdir::LocalWorkdirSession::materialized_bound(
+        let workdir_tool_broker = workdir::WorkdirToolBrokerRouter::from_single(
+            workdir::WorkdirAttachmentAlias::new("workdir").unwrap(),
+            Arc::new(workdir::LocalWorkdirSession::materialized_bound(
                 workdir::Workdir::new("test-workdir"),
                 workspace_root.clone(),
                 workspace_root.clone(),
                 spawner_scope.clone(),
                 workdir::WorkdirSessionCapabilities::ALL,
-            ),
-        ));
+            )),
+        )
+        .unwrap();
         let tool = SubWorkerSpawnTool::new(
             "parent".into(),
             workspace_context,
@@ -1528,9 +1569,11 @@ enabled = false
             Arc::new(AvailableWorkspaceClient),
         );
         let remote_client = Arc::new(StrictRemoteWorkdirWorkspaceClient::default());
-        let workdir_tool_broker = workdir::WorkdirToolBroker::new(
-            WorkspaceAttachedWorkdirSession::handle(remote_client.clone()),
-        );
+        let workdir_tool_broker = workdir::WorkdirToolBrokerRouter::from_single(
+            workdir::WorkdirAttachmentAlias::new("workdir").unwrap(),
+            WorkspaceAttachedWorkdirSession::handle(remote_client.clone(), "workdir"),
+        )
+        .unwrap();
         let calls = Arc::new(AtomicUsize::new(0));
         let (parent_method_tx, _parent_method_rx) = mpsc::channel(8);
         let tool = SubWorkerSpawnTool::new(
@@ -1607,6 +1650,7 @@ enabled = false
         assert!(properties.contains_key("command"), "schema: {schema}");
         let schema_text = serde_json::to_string(&schema).unwrap();
         assert!(schema_text.contains("symlink_policy"), "schema: {schema}");
+        assert!(schema_text.contains("target_workdir"), "schema: {schema}");
         assert!(schema_text.contains("logical"), "schema: {schema}");
         let required = schema
             .get("required")

crates/worker/src/worker.rs

@@ -45,9 +45,9 @@ use crate::compact::state::{
 };
 use crate::compact::telemetry::{
     CompactAttempt, CompactFailureCategory, CompactMode, CompactSuccessStats,
-    CompactThresholdPolicy, correlated_post_request_metric, new_compact_metric_correlation_id,
+    CompactThresholdPolicy, new_compact_metric_correlation_id,
 };
-use crate::compact::usage_tracker::UsageTracker;
+use crate::compact::usage_tracker::{UsageTracker, persist_pending_usage};
 use crate::feature::background::{BackgroundTaskRewriteGuard, FeatureBackgroundTaskRegistry};
 use crate::feature::builtin::memory::WorkspaceMemoryBackendError;
 use crate::feature::builtin::{TaskFeature, WorkerObservationProvider};
@@ -374,7 +374,8 @@ use protocol::{
 use tokio::net::UnixStream;
 use tokio::sync::broadcast;
 use workdir::{
-    LocalWorkdirSession, ReadOnlyWorkdirSession, WorkdirSessionCapabilities, WorkdirSessionHandle,
+    LocalWorkdirSession, ReadOnlyWorkdirSession, WorkdirAttachmentAlias,
+    WorkdirSessionCapabilities, WorkdirSessionHandle, WorkdirSessionRouter,
 };
 
 const RESTORE_RECONCILIATION_REACHABILITY_TIMEOUT: Duration = Duration::from_millis(500);
@@ -1946,6 +1947,28 @@ impl PendingSubmissionHandle<session_store::FsStore> {
 pub trait SystemItemCommitter: Send + Sync {
     fn commit_log_entry(&self, entry: LogEntry) -> Result<(), StoreError>;
 
+    /// Commit one authoritative usage record while holding the same append
+    /// barrier across its in-memory publication, guard rearm, and correlated
+    /// post-request metrics. Metric appends remain best-effort.
+    fn commit_usage_boundary(
+        &self,
+        entry: LogEntry,
+        after_commit: &mut dyn FnMut(),
+        post_metrics: &[session_metrics::Metric],
+    ) -> Result<(), StoreError> {
+        self.commit_log_entry(entry)?;
+        after_commit();
+        for metric in post_metrics {
+            let payload = serde_json::to_value(metric).expect("Metric is Serialize");
+            let _ = self.commit_log_entry(LogEntry::Extension {
+                ts: segment_log::now_millis(),
+                domain: session_metrics::DOMAIN.into(),
+                payload,
+            });
+        }
+        Ok(())
+    }
+
     fn commit_system_item_with_extensions(
         &self,
         item: SystemItem,
@@ -1977,6 +2000,30 @@ where
     fn commit_log_entry(&self, entry: LogEntry) -> Result<(), StoreError> {
         self.append_entry(entry)
     }
+
+    fn commit_usage_boundary(
+        &self,
+        entry: LogEntry,
+        after_commit: &mut dyn FnMut(),
+        post_metrics: &[session_metrics::Metric],
+    ) -> Result<(), StoreError> {
+        let _append_guard = self
+            .state
+            .append_lock
+            .lock()
+            .expect("segment append lock poisoned");
+        self.append_entry_locked(entry)?;
+        after_commit();
+        for metric in post_metrics {
+            let payload = serde_json::to_value(metric).expect("Metric is Serialize");
+            let _ = self.append_entry_locked(LogEntry::Extension {
+                ts: segment_log::now_millis(),
+                domain: session_metrics::DOMAIN.into(),
+                payload,
+            });
+        }
+        Ok(())
+    }
 }
 
 struct SessionFlowRuntimeStateCommitter<St: Store + Clone> {
@@ -2128,9 +2175,9 @@ pub struct Worker<C: LlmClient, St: Store> {
     /// Explicit local filesystem authority, or `None` for Workers with no
     /// local cwd and no filesystem/Bash tool surface.
     filesystem_authority: WorkerFilesystemAuthority,
-    /// Live WorkdirSession provider derived once from the Worker–Workdir binding.
-    /// Local tools, file views, and compaction workers clone this handle.
-    workdir_session: Option<WorkdirSessionHandle>,
+    /// Alias-keyed live Workdir sessions. Provider transport remains hidden
+    /// behind each handle and no attachment is designated primary.
+    workdir_sessions: Arc<WorkdirSessionRouter>,
     /// Path-free workspace identity/client context injected by Runtime/host.
     /// This never grants local filesystem authority.
     workspace_context: WorkerWorkspaceContext,
@@ -2154,16 +2201,16 @@ pub struct Worker<C: LlmClient, St: Store> {
     /// Shared compaction state (present when threshold is configured).
     compact_state: Option<Arc<CompactState>>,
     /// Per-LLM-request Usage tracker. Always present after construction.
-    /// Captures `(history_len, UsageEvent)` pairs during a run; drained
-    /// in `persist_turn` and persisted as `LogEntry::LlmUsage` entries.
+    /// Captures `(history_len, UsageEvent)` pairs until their authoritative
+    /// request-boundary or terminal `LlmUsage` append succeeds.
     usage_tracker: Arc<UsageTracker>,
     /// Sync-side buffer for `Metric` values queued from inside Engine
-    /// callbacks (currently the prune observer). Drained in `persist_turn`
-    /// and written via `session_metrics::record_metric` alongside
-    /// `LogEntry::LlmUsage`. Always present after construction.
+    /// callbacks (currently the prune observer). Drained at the same request
+    /// boundary as usage, with terminal `persist_turn` as the fallback.
     metrics_tracker: Arc<crate::compact::metrics_tracker::MetricsTracker>,
     /// Cumulative Usage measurement timeline, one entry per LLM call.
-    /// Restored from session log on `restore`, appended on each persist.
+    /// Restored from session log on `restore`, appended after each durable
+    /// request-boundary usage commit.
     /// Read by token-accounting APIs (`Worker::total_tokens`, etc.).
     ///
     /// Wrapped in `Arc<Mutex>` so that callbacks injected into the
@@ -2464,7 +2511,7 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
         let prompts = Arc::new(ArcSwap::from(PromptCatalog::builtins_only()?));
         DelegationScope::from_config(&manifest.delegation_scope).map_err(WorkerError::Scope)?;
         let scope = SharedScope::new(scope);
-        let workdir_session = workdir_session_from_authority(&filesystem_authority, &scope);
+        let workdir_sessions = workdir_sessions_from_authority(&filesystem_authority, &scope);
         let mut worker = Self {
             manifest,
             engine: Some(worker),
@@ -2475,7 +2522,7 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
             worker_metadata_segment_cas: None,
             segment_state: SegmentState::new(session_id, segment_id, 0),
             filesystem_authority,
-            workdir_session,
+            workdir_sessions,
             workspace_context,
             flow_runtime_state: Arc::new(Mutex::new(None)),
             flow_feature_enabled: false,
@@ -2652,15 +2699,36 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
         self.filesystem_authority.as_local()
     }
 
-    pub fn workdir_session(&self) -> Option<&WorkdirSessionHandle> {
-        self.workdir_session.as_ref()
+    /// Compatibility projection for tool schemas that do not yet carry a
+    /// target alias. It is available only when the attachment set has exactly
+    /// one member, so multiple attachments never acquire an implicit primary.
+    pub fn workdir_session(&self) -> Option<WorkdirSessionHandle> {
+        self.workdir_sessions.only_session()
     }
 
-    /// Replace the constructor fallback with the provider binding resolved by
-    /// the owning Runtime. Runtime calls this before the Worker controller is
-    /// spawned, so tools only ever observe the Runtime-bound handle.
-    pub fn bind_workdir_session(&mut self, workdir_session: Option<WorkdirSessionHandle>) {
-        self.workdir_session = workdir_session;
+    pub fn workdir_sessions(&self) -> Arc<WorkdirSessionRouter> {
+        self.workdir_sessions.clone()
+    }
+
+    /// Replace the constructor fallback with the complete alias-keyed provider
+    /// set resolved by the owning Runtime before controller startup.
+    pub fn bind_workdir_sessions(&mut self, workdir_sessions: Arc<WorkdirSessionRouter>) {
+        self.workdir_sessions = workdir_sessions;
+    }
+
+    /// Bind one session for direct/Internal Worker construction. Runtime Worker
+    /// creation uses [`Self::bind_workdir_sessions`] with the complete set.
+    pub fn bind_single_workdir_session(&mut self, workdir_session: Option<WorkdirSessionHandle>) {
+        let router = Arc::new(WorkdirSessionRouter::new());
+        if let Some(session) = workdir_session {
+            router
+                .attach(
+                    WorkdirAttachmentAlias::new("workdir").expect("static alias is valid"),
+                    session,
+                )
+                .expect("fresh Workdir router accepts its only attachment");
+        }
+        self.workdir_sessions = router;
     }
 
     /// Path-free workspace identity, if Runtime/host associated this Worker
@@ -2928,12 +2996,7 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
             location.session_id,
             location.segment_id,
         );
-        let read_only_tools = self
-            .workdir_session
-            .clone()
-            .map(|source| Arc::new(ReadOnlyWorkdirSession::new(source)) as WorkdirSessionHandle)
-            .map(tools::read_only_builtin_tools)
-            .unwrap_or_default();
+        let read_only_tools = tools::read_only_routed_builtin_tools(self.workdir_sessions());
         let client = self
             .engine
             .as_ref()
@@ -3309,8 +3372,8 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
     /// Handle to the synchronous `MetricsTracker` buffer.
     ///
     /// Engine callbacks (e.g. the prune observer) clone this `Arc` and
-    /// `.push(metric)` into it; Worker drains it in `persist_turn` and
-    /// writes each metric via `session_metrics::record_metric`.
+    /// `.push(metric)` into it; Worker drains it at the next request accounting
+    /// boundary, with terminal persistence as fallback.
     pub(crate) fn metrics_tracker_handle(
         &self,
     ) -> Arc<crate::compact::metrics_tracker::MetricsTracker> {
@@ -3546,6 +3609,7 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
                 self.pending_committed_history.clone(),
             )
             .with_usage_tracker(self.usage_tracker.clone())
+            .with_metrics_tracker(self.metrics_tracker.clone())
             .with_prompt_workspace_id(
                 self.workspace_context
                     .workspace_id()
@@ -4061,7 +4125,7 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
     /// unresolved placeholder stays in the flattened user message so the LLM
     /// still sees the intent.
     async fn resolve_file_refs(&self, segments: &[Segment]) -> Vec<SystemItem> {
-        let Some(workdir) = self.workdir_session.clone() else {
+        let Some(workdir) = self.workdir_session() else {
             for seg in segments {
                 if let Segment::FileRef { path } = seg {
                     self.alert(
@@ -4431,6 +4495,15 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
         self.handle_worker_result(result, history_before).await
     }
 
+    fn ensure_no_pending_usage_for_segment_replacement(&self) -> Result<(), WorkerError> {
+        let pending_records = self.usage_tracker.pending_record_count();
+        if pending_records == 0 {
+            Ok(())
+        } else {
+            Err(WorkerError::PendingUsagePersistence { pending_records })
+        }
+    }
+
     /// Ensure the session exists and the writer's tally still matches
     /// the on-disk entry count.
     ///
@@ -4472,6 +4545,7 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
         if store_count == entries_written {
             return Ok(());
         }
+        self.ensure_no_pending_usage_for_segment_replacement()?;
         // Auto-fork within the same Session: mint a fresh Segment and
         // switch to it. The source segment is left immutable (no terminal
         // marker is written back); the fork relationship is recorded
@@ -5008,45 +5082,38 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
             self.try_record_metric(&metric);
         }
 
-        // Persist any LLM Usage measurements collected during this run.
-        // One LogEntry::LlmUsage per LLM call (the tool loop may have run
-        // many calls within a single Worker::run). Each is also appended to
-        // the in-memory `usage_history` so token-accounting APIs see it
-        // before the next run. Records carrying a `correlation_id` (set
-        // by an upstream observer such as the prune projection) also get
-        // a paired `prune.post_request` metric so cache_read/write can be
-        // joined back to the originating event.
-        let usage_records = self.usage_tracker.drain();
-        for recorded in usage_records {
-            let crate::compact::usage_tracker::RecordedUsage {
-                record,
-                post_requests,
-            } = recorded;
-            let committed_post_compact_request = post_requests.iter().any(|link| {
-                link.metric == crate::compact::usage_tracker::PostRequestMetric::Compaction
-            });
-            self.commit_entry(LogEntry::LlmUsage {
-                ts: segment_log::now_millis(),
-                history_len: record.history_len,
-                input_total_tokens: record.input_total_tokens,
-                cache_read_tokens: record.cache_read_tokens,
-                cache_write_tokens: record.cache_write_tokens,
-                output_tokens: record.output_tokens,
-            })?;
-            if committed_post_compact_request {
-                if let Some(state) = &self.compact_state {
-                    state.post_compact_request_committed();
-                }
-            }
-            for link in post_requests {
-                let metric =
-                    correlated_post_request_metric(link.metric, &link.correlation_id, &record);
+        // Persist any request measurements that did not already cross the
+        // in-run request boundary (for example partial usage from an errored or
+        // cancelled stream, or low-level Workers without an attached writer).
+        // `persist_pending_usage` removes each record only after its authoritative
+        // LlmUsage append succeeds, so the in-run and terminal paths cannot
+        // double-write or silently lose a failed append.
+        let usage_tracker = self.usage_tracker.clone();
+        let usage_history = self.usage_history.clone();
+        let compact_state = self.compact_state.clone();
+        if let Some(writer) = self.log_writer.clone() {
+            let _ = persist_pending_usage(
+                &usage_tracker,
+                &usage_history,
+                compact_state.as_deref(),
+                |entry, after_commit, post_metrics| {
+                    writer.commit_usage_boundary(entry, after_commit, post_metrics)
+                },
+            )?;
+        } else {
+            let post_request_metrics = persist_pending_usage(
+                &usage_tracker,
+                &usage_history,
+                compact_state.as_deref(),
+                |entry, after_commit, _post_metrics| {
+                    self.commit_entry(entry)?;
+                    after_commit();
+                    Ok(())
+                },
+            )?;
+            for metric in post_request_metrics {
                 self.try_record_metric(&metric);
             }
-            self.usage_history
-                .lock()
-                .expect("usage_history poisoned")
-                .push(record);
         }
 
         let interrupted = matches!(
@@ -5106,6 +5173,7 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
         mut cancel: Option<tokio::sync::watch::Receiver<bool>>,
         trigger: CompactionTrigger,
     ) -> Result<SegmentId, WorkerError> {
+        self.ensure_no_pending_usage_for_segment_replacement()?;
         self.release_pending_compaction_service().await?;
         let _rewrite_guard = self
             .prepare_session_rewrite(SessionRewriteKind::Compact)
@@ -5380,11 +5448,14 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
         // Default references: the N most-recently-touched files in the
         // session, surfaced so the compact worker can inspect them and
         // decide which (if any) the next session needs.
-        let default_refs: Vec<PathBuf> = self
-            .tracker
-            .as_ref()
-            .map(|t| t.recent_files(manifest::defaults::COMPACT_DEFAULT_REFERENCE_COUNT))
-            .unwrap_or_default();
+        let default_refs: Vec<PathBuf> = if self.workdir_sessions.len() == 1 {
+            self.tracker
+                .as_ref()
+                .map(|t| t.recent_files(manifest::defaults::COMPACT_DEFAULT_REFERENCE_COUNT))
+                .unwrap_or_default()
+        } else {
+            Vec::new()
+        };
 
         // Input text fed to the compact worker. Includes the default
         // references, current TaskStore snapshot, current TaskStore snapshot, and the (pruned) conversation text.
@@ -5428,7 +5499,7 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
 
         // Build a normal parent-owned Internal Worker over a pinned immutable
         // capture. Only SessionExplore and compaction output tools are installed.
-        let workdir = self.workdir_session.clone();
+        let workdir = self.workdir_session();
         let read_only_workdir = workdir.clone().map(|session| {
             Arc::new(ReadOnlyWorkdirSession::new(session)) as workdir::WorkdirSessionHandle
         });
@@ -6139,7 +6210,8 @@ where
         let worker_metadata_writer = Some(worker_metadata_writer_for_store(&store));
         let worker_metadata_segment_cas = Some(worker_metadata_segment_cas_for_store(&store));
         let scope = SharedScope::new(common.scope);
-        let workdir_session = workdir_session_from_authority(&common.filesystem_authority, &scope);
+        let workdir_sessions =
+            workdir_sessions_from_authority(&common.filesystem_authority, &scope);
 
         let mut worker = Self {
             manifest,
@@ -6151,7 +6223,7 @@ where
             worker_metadata_segment_cas,
             segment_state: SegmentState::new(session_id, segment_id, 0),
             filesystem_authority: common.filesystem_authority,
-            workdir_session,
+            workdir_sessions,
             workspace_context: common.workspace_context,
             flow_runtime_state: Arc::new(Mutex::new(None)),
             flow_feature_enabled: false,
@@ -6228,7 +6300,8 @@ where
         apply_worker_manifest(&mut engine, &manifest.engine);
         engine.set_cache_key(Some(segment_id.to_string()));
         let scope = SharedScope::new(common.scope);
-        let workdir_session = workdir_session_from_authority(&common.filesystem_authority, &scope);
+        let workdir_sessions =
+            workdir_sessions_from_authority(&common.filesystem_authority, &scope);
         let mut worker = Self {
             manifest,
             engine: Some(engine),
@@ -6239,7 +6312,7 @@ where
             worker_metadata_segment_cas: None,
             segment_state: SegmentState::new(session_id, segment_id, 0),
             filesystem_authority: common.filesystem_authority,
-            workdir_session,
+            workdir_sessions,
             workspace_context: common.workspace_context,
             flow_runtime_state: Arc::new(Mutex::new(None)),
             flow_feature_enabled: false,
@@ -6350,7 +6423,8 @@ where
         let worker_metadata_writer = Some(worker_metadata_writer_for_store(&store));
         let worker_metadata_segment_cas = Some(worker_metadata_segment_cas_for_store(&store));
         let scope = SharedScope::new(common.scope);
-        let workdir_session = workdir_session_from_authority(&common.filesystem_authority, &scope);
+        let workdir_sessions =
+            workdir_sessions_from_authority(&common.filesystem_authority, &scope);
 
         let mut worker = Self {
             manifest,
@@ -6362,7 +6436,7 @@ where
             worker_metadata_segment_cas,
             segment_state: SegmentState::new(session_id, segment_id, 0),
             filesystem_authority: common.filesystem_authority,
-            workdir_session,
+            workdir_sessions,
             workspace_context: common.workspace_context,
             flow_runtime_state: Arc::new(Mutex::new(None)),
             flow_feature_enabled: false,
@@ -6726,7 +6800,8 @@ where
         let worker_metadata_writer = Some(worker_metadata_writer_for_store(&store));
         let worker_metadata_segment_cas = Some(worker_metadata_segment_cas_for_store(&store));
         let scope = SharedScope::new(common.scope);
-        let workdir_session = workdir_session_from_authority(&common.filesystem_authority, &scope);
+        let workdir_sessions =
+            workdir_sessions_from_authority(&common.filesystem_authority, &scope);
 
         let mut worker = Self {
             manifest,
@@ -6738,7 +6813,7 @@ where
             worker_metadata_segment_cas,
             segment_state: SegmentState::new(session_id, segment_id, state.entries_count),
             filesystem_authority: common.filesystem_authority,
-            workdir_session,
+            workdir_sessions,
             workspace_context: common.workspace_context,
             flow_runtime_state: Arc::new(Mutex::new(restored_flow_runtime_state(
                 &state.extensions,
@@ -7413,7 +7488,9 @@ fn compact_failure_category(error: &WorkerError) -> CompactFailureCategory {
         | WorkerError::SegmentActivationIncomplete { .. } => {
             CompactFailureCategory::ActiveSegmentCommit
         }
-        WorkerError::Store(_) => CompactFailureCategory::Storage,
+        WorkerError::Store(_) | WorkerError::PendingUsagePersistence { .. } => {
+            CompactFailureCategory::Storage
+        }
         WorkerError::InvalidState(_) | WorkerError::Engine(_) => {
             CompactFailureCategory::InternalWorker
         }
@@ -7477,6 +7554,11 @@ pub enum WorkerError {
     #[error(transparent)]
     Provider(#[from] crate::model_client::ProviderError),
 
+    #[error(
+        "cannot replace the active Segment while {pending_records} usage record(s) await durable persistence"
+    )]
+    PendingUsagePersistence { pending_records: usize },
+
     #[error("active Segment changed before compaction commit")]
     CompactActiveSegmentChanged,
 
@@ -7580,18 +7662,26 @@ pub enum WorkerError {
     },
 }
 
-fn workdir_session_from_authority(
+fn workdir_sessions_from_authority(
     authority: &WorkerFilesystemAuthority,
     scope: &SharedScope,
-) -> Option<WorkdirSessionHandle> {
-    authority.as_local().map(|local| {
-        Arc::new(LocalWorkdirSession::materialized(
+) -> Arc<WorkdirSessionRouter> {
+    let router = Arc::new(WorkdirSessionRouter::new());
+    if let Some(local) = authority.as_local() {
+        let session = Arc::new(LocalWorkdirSession::materialized(
             local.root.clone(),
             local.cwd.clone(),
             scope.clone(),
             WorkdirSessionCapabilities::ALL,
-        )) as WorkdirSessionHandle
-    })
+        )) as WorkdirSessionHandle;
+        router
+            .attach(
+                WorkdirAttachmentAlias::new("workdir").expect("static alias is valid"),
+                session,
+            )
+            .expect("fresh Workdir router accepts its only attachment");
+    }
+    router
 }
 
 /// Bundle of resources that every high-level Worker constructor needs:
@@ -8534,6 +8624,117 @@ mod build_summary_prompt_tests {
         }
     }
 
+    #[tokio::test]
+    async fn failed_usage_append_fences_segment_rotation_until_retry_commits_once() {
+        let dir = tempfile::tempdir().unwrap();
+        let store = session_store::FsStore::new(dir.path().join("sessions")).unwrap();
+        let mut worker = Worker::new(
+            minimal_manifest(),
+            Engine::<_, Mutable, SessionHistoryMetadata>::new_annotated(NoopClient),
+            store.clone(),
+            WorkerWorkspaceContext::no_workspace(),
+            WorkerFilesystemAuthority::None,
+            Scope::empty(),
+        )
+        .await
+        .unwrap();
+        worker.ensure_segment_head().await.unwrap();
+        let session_id = worker.session_id();
+        let source_segment = worker.segment_id();
+
+        worker
+            .usage_tracker
+            .note_compaction_correlation_id("compact-id".into());
+        worker.usage_tracker.note_request(1);
+        worker.usage_tracker.record_usage(&agen::event::UsageEvent {
+            input_tokens: Some(10),
+            output_tokens: Some(1),
+            total_tokens: Some(11),
+            cache_read_input_tokens: Some(0),
+            cache_creation_input_tokens: Some(0),
+        });
+        worker.usage_tracker.request_completed();
+
+        let append_error = persist_pending_usage(
+            &worker.usage_tracker,
+            &worker.usage_history,
+            worker.compact_state.as_deref(),
+            |_, _, _| Err(StoreError::Io(std::io::Error::other("synthetic failure"))),
+        )
+        .expect_err("first usage append must fail");
+        assert!(append_error.to_string().contains("synthetic failure"));
+        assert_eq!(worker.usage_tracker.pending_record_count(), 1);
+
+        // Simulate another writer extending the active Segment. The normal run
+        // prelude must not auto-fork while the failed record still belongs to
+        // this Segment.
+        store
+            .append(
+                session_id,
+                source_segment,
+                &LogEntry::TurnEnd {
+                    ts: segment_log::now_millis(),
+                    turn_count: 99,
+                },
+            )
+            .unwrap();
+        let run_error = worker
+            .run_text("must stop before provider ownership")
+            .await
+            .expect_err("head drift must not fork past pending usage");
+        assert!(matches!(
+            run_error,
+            WorkerError::PendingUsagePersistence { pending_records: 1 }
+        ));
+        assert_eq!(worker.segment_id(), source_segment);
+        assert_eq!(
+            store.list_segments(session_id).unwrap(),
+            vec![source_segment]
+        );
+
+        let error = worker
+            .compact(0)
+            .await
+            .expect_err("pending usage must fence Segment replacement");
+        assert!(matches!(
+            error,
+            WorkerError::PendingUsagePersistence { pending_records: 1 }
+        ));
+        assert_eq!(worker.segment_id(), source_segment);
+        assert_eq!(
+            store.list_segments(session_id).unwrap(),
+            vec![source_segment]
+        );
+
+        let metrics = persist_pending_usage(
+            &worker.usage_tracker,
+            &worker.usage_history,
+            worker.compact_state.as_deref(),
+            |entry, after_commit, _| {
+                store.append(session_id, source_segment, &entry)?;
+                after_commit();
+                Ok(())
+            },
+        )
+        .expect("retry should commit on the originating Segment");
+        assert_eq!(worker.usage_tracker.pending_record_count(), 0);
+        assert_eq!(worker.usage_history.lock().unwrap().len(), 1);
+        assert_eq!(metrics.len(), 1, "correlation must be emitted once");
+        assert_eq!(metrics[0].name, "compact.post_request");
+
+        let usage_entries = store
+            .read_all(session_id, source_segment)
+            .unwrap()
+            .into_iter()
+            .filter(|entry| matches!(entry, LogEntry::LlmUsage { .. }))
+            .count();
+        assert_eq!(usage_entries, 1, "retry must not duplicate accounting");
+        assert_eq!(
+            store.list_segments(session_id).unwrap(),
+            vec![source_segment]
+        );
+    }
+
     #[tokio::test]
     async fn fresh_run_clears_interrupted_budget_before_pre_run_compaction() {
         let dir = tempfile::tempdir().unwrap();

crates/worker/tests/compact_events_test.rs

@@ -7,15 +7,16 @@
 //!   (driven by `compact_request_threshold` → `PreRequestAction::Yield`)
 
 use std::pin::Pin;
-use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
+use std::sync::{Arc, Mutex};
 
 use agen::Engine;
 use agen::llm_client::event::{Event as LlmEvent, ResponseStatus, StatusEvent, UsageEvent};
 use agen::llm_client::types::Item;
 use agen::llm_client::{ClientError, LlmClient, Request};
+use agen::tool::{Tool, ToolDefinition, ToolError, ToolMeta, ToolOutput};
 use async_trait::async_trait;
-use futures::Stream;
+use futures::{Stream, StreamExt};
 use protocol::{Event, Method, RunResult};
 use session_store::{
     CombinedStore, FsStore, FsWorkerStore, LogEntry, Store, WorkerMetadata, WorkerMetadataStore,
@@ -125,10 +126,13 @@ fn annotated(item: Item) -> session_store::LoggedHistoryEntry {
     }
 }
 
+type CallObserver = Arc<dyn Fn(usize) + Send + Sync>;
+
 #[derive(Clone)]
 struct MockClient {
     responses: Arc<Vec<Vec<LlmEvent>>>,
     call_count: Arc<AtomicUsize>,
+    observer: Arc<Mutex<Option<CallObserver>>>,
 }
 
 impl MockClient {
@@ -136,8 +140,13 @@ impl MockClient {
         Self {
             responses: Arc::new(responses),
             call_count: Arc::new(AtomicUsize::new(0)),
+            observer: Arc::new(Mutex::new(None)),
         }
     }
+
+    fn set_observer(&self, observer: impl Fn(usize) + Send + Sync + 'static) {
+        *self.observer.lock().unwrap() = Some(Arc::new(observer));
+    }
 }
 
 #[async_trait]
@@ -152,6 +161,9 @@ impl LlmClient for MockClient {
     ) -> Result<Pin<Box<dyn Stream<Item = Result<LlmEvent, ClientError>> + Send>>, ClientError>
     {
         let count = self.call_count.fetch_add(1, Ordering::SeqCst);
+        if let Some(observer) = self.observer.lock().unwrap().clone() {
+            observer(count);
+        }
         if count >= self.responses.len() {
             return Err(ClientError::Config("mock client exhausted".into()));
         }
@@ -161,6 +173,90 @@ impl LlmClient for MockClient {
     }
 }
 
+#[derive(Clone)]
+struct PauseAfterUsageClient {
+    responses: Arc<Vec<Vec<LlmEvent>>>,
+    call_count: Arc<AtomicUsize>,
+    hanging_call: usize,
+}
+
+impl PauseAfterUsageClient {
+    fn new(responses: Vec<Vec<LlmEvent>>, hanging_call: usize) -> Self {
+        Self {
+            responses: Arc::new(responses),
+            call_count: Arc::new(AtomicUsize::new(0)),
+            hanging_call,
+        }
+    }
+}
+
+#[async_trait]
+impl LlmClient for PauseAfterUsageClient {
+    fn clone_boxed(&self) -> Box<dyn LlmClient> {
+        Box::new(self.clone())
+    }
+
+    async fn stream(
+        &self,
+        _request: Request,
+    ) -> Result<Pin<Box<dyn Stream<Item = Result<LlmEvent, ClientError>> + Send>>, ClientError>
+    {
+        let count = self.call_count.fetch_add(1, Ordering::SeqCst);
+        let events = self
+            .responses
+            .get(count)
+            .cloned()
+            .ok_or_else(|| ClientError::Config("pause mock client exhausted".into()))?;
+        let finite = futures::stream::iter(events.into_iter().map(Ok));
+        if count == self.hanging_call {
+            Ok(Box::pin(finite.chain(futures::stream::pending())))
+        } else {
+            Ok(Box::pin(finite))
+        }
+    }
+}
+
+#[derive(Clone)]
+struct GrowTool;
+
+#[async_trait]
+impl Tool for GrowTool {
+    async fn execute(
+        &self,
+        _input: &str,
+        _ctx: agen::tool::ToolExecutionContext,
+    ) -> Result<ToolOutput, ToolError> {
+        Ok(ToolOutput {
+            summary: "grew context".into(),
+            content: Some("x".repeat(400_000)),
+            attachments: Vec::new(),
+        })
+    }
+}
+
+fn grow_tool_definition() -> ToolDefinition {
+    Arc::new(|| {
+        (
+            ToolMeta::new("grow")
+                .description("test tool that grows request context")
+                .input_schema(serde_json::json!({"type": "object"})),
+            Arc::new(GrowTool) as Arc<dyn Tool>,
+        )
+    })
+}
+
+fn grow_tool_use_events(call_id: &str, input_tokens: u64) -> Vec<LlmEvent> {
+    vec![
+        LlmEvent::tool_use_start(0, call_id, "grow"),
+        LlmEvent::tool_input_delta(0, "{}"),
+        LlmEvent::tool_use_stop(0),
+        LlmEvent::usage(input_tokens, 1),
+        LlmEvent::Status(StatusEvent {
+            status: ResponseStatus::Completed,
+        }),
+    ]
+}
+
 #[derive(Clone)]
 struct BlockingCompactClient {
     calls: Arc<AtomicUsize>,
@@ -365,12 +461,13 @@ where
     let scope = worker::Scope::writable(&pwd).unwrap();
     std::mem::forget(pwd_tmp);
 
-    let worker =
+    let mut engine =
         Engine::<_, agen::state::Mutable, worker::SessionHistoryMetadata>::new_annotated(client);
+    engine.register_tool(grow_tool_definition());
     let observed_store = store.clone();
     let mut worker = Worker::new(
         manifest,
-        worker,
+        engine,
         store,
         worker::WorkerWorkspaceContext::local_filesystem(None),
         worker::WorkerFilesystemAuthority::local(pwd.clone(), pwd.clone()),
@@ -379,6 +476,7 @@ where
     .await
     .unwrap();
     worker.enable_worker_metadata_write_through().unwrap();
+    worker.attach_log_writer(Arc::new(worker.log_writer_handle()));
     (worker, observed_store)
 }
 
@@ -1057,6 +1155,289 @@ async fn request_threshold_compact_publishes_runtime_progress() {
     assert_eq!(post.metric.correlation_id.as_deref(), Some(correlation_id));
 }
 
+#[tokio::test]
+async fn completed_post_compact_usage_rearms_within_one_tool_loop() {
+    let client = MockClient::new(vec![
+        text_events_with_usage("seed", 100_000),
+        write_summary_tool_use_events("compact-1", "first summary"),
+        single_text_events("done"),
+        grow_tool_use_events("grow-1", 1_000),
+        write_summary_tool_use_events("compact-2", "second summary"),
+        single_text_events("done"),
+        text_events_with_usage("finished", 800),
+    ]);
+    let call_count = Arc::clone(&client.call_count);
+    let observed_client = client.clone();
+    let manifest = MID_TURN_MANIFEST_TOML.replace(
+        "compact_request_threshold = 100",
+        "compact_threshold = 80000\ncompact_request_threshold = 50000",
+    );
+    let (mut worker, store) = make_worker_with_manifest_and_store(&manifest, client).await;
+    let session_id = worker.session_id();
+    let durable_at_next_request = Arc::new(AtomicBool::new(false));
+    let observed_barrier = Arc::clone(&durable_at_next_request);
+    let observed_store = store.clone();
+    observed_client.set_observer(move |call_index| {
+        if call_index != 4 {
+            return;
+        }
+        let usage_is_durable = observed_store
+            .list_segments(session_id)
+            .unwrap()
+            .into_iter()
+            .flat_map(|segment_id| observed_store.read_all(session_id, segment_id).unwrap())
+            .any(|entry| {
+                matches!(
+                    entry,
+                    LogEntry::LlmUsage {
+                        input_total_tokens: 1_000,
+                        ..
+                    }
+                )
+            });
+        assert!(
+            usage_is_durable,
+            "the first post-compact usage must be durable before the next provider request"
+        );
+        observed_barrier.store(true, Ordering::SeqCst);
+    });
+
+    worker.run_text("seed input").await.unwrap();
+    worker
+        .run_text("continue through two compactions")
+        .await
+        .expect("a successful post-compact request must rearm before the tool-loop threshold");
+
+    assert_eq!(
+        call_count.load(Ordering::SeqCst),
+        7,
+        "both compactor cycles and both normal post-compact requests must run"
+    );
+    assert!(durable_at_next_request.load(Ordering::SeqCst));
+
+    let metrics = session_metrics::read_session_metrics(&store, session_id).unwrap();
+    let compact_starts = metrics
+        .iter()
+        .filter(|record| record.metric.name == "compact.start")
+        .collect::<Vec<_>>();
+    assert_eq!(compact_starts.len(), 2);
+    assert!(compact_starts.iter().any(|record| {
+        record.metric.dimensions.get("trigger").map(String::as_str) == Some("pre_run")
+    }));
+    assert!(compact_starts.iter().any(|record| {
+        record.metric.dimensions.get("trigger").map(String::as_str) == Some("request_threshold")
+    }));
+    let compact_posts = metrics
+        .iter()
+        .filter(|record| record.metric.name == "compact.post_request")
+        .collect::<Vec<_>>();
+    assert_eq!(compact_posts.len(), 2);
+    assert_ne!(
+        compact_posts[0].metric.correlation_id,
+        compact_posts[1].metric.correlation_id
+    );
+
+    let usage = store
+        .list_segments(session_id)
+        .unwrap()
+        .into_iter()
+        .flat_map(|segment_id| store.read_all(session_id, segment_id).unwrap())
+        .filter_map(|entry| match entry {
+            LogEntry::LlmUsage {
+                input_total_tokens, ..
+            } => Some(input_total_tokens),
+            _ => None,
+        })
+        .collect::<Vec<_>>();
+    assert_eq!(usage.iter().filter(|tokens| **tokens == 1_000).count(), 1);
+    assert_eq!(usage.iter().filter(|tokens| **tokens == 800).count(), 1);
+
+    let restored = session_store::restore(&store, session_id, worker.segment_id()).unwrap();
+    assert_eq!(restored.usage_history.len(), 1);
+    assert_eq!(restored.usage_history[0].input_total_tokens, 800);
+}
+
+#[tokio::test]
+async fn post_compact_pause_bills_partial_without_rearming_or_consuming_correlation() {
+    let client = PauseAfterUsageClient::new(
+        vec![
+            text_events_with_usage("seed", 100_000),
+            write_summary_tool_use_events("manual-compact", "pause test summary"),
+            single_text_events("done"),
+            vec![
+                LlmEvent::text_block_start(0),
+                LlmEvent::text_delta(0, "partial"),
+                LlmEvent::usage(90, 2),
+            ],
+            grow_tool_use_events("grow-after-resume", 80),
+            write_summary_tool_use_events("automatic-compact", "rearmed summary"),
+            single_text_events("done"),
+            text_events_with_usage("finished", 50),
+        ],
+        3,
+    );
+    let call_count = Arc::clone(&client.call_count);
+    let manifest = MID_TURN_MANIFEST_TOML.replace(
+        "compact_request_threshold = 100",
+        "compact_threshold = 80000\ncompact_request_threshold = 50000",
+    );
+    let (worker, store) = make_worker_with_manifest_and_store(&manifest, client).await;
+    let session_id = worker.session_id();
+
+    let runtime_tmp = tempfile::tempdir().unwrap();
+    let bash_output_dir = runtime_tmp.path().join("bash-output");
+    let (handle, shutdown_receiver) =
+        WorkerController::spawn(worker, runtime_tmp.path(), &bash_output_dir)
+            .await
+            .unwrap();
+    let mut rx = handle.subscribe();
+    handle
+        .send(Method::submit_text(
+            protocol::new_submission_request_id(),
+            "seed history",
+        ))
+        .await
+        .unwrap();
+    loop {
+        if matches!(
+            tokio::time::timeout(std::time::Duration::from_secs(2), rx.recv())
+                .await
+                .expect("timeout waiting for seed")
+                .expect("event"),
+            Event::RunEnd {
+                result: RunResult::Finished
+            }
+        ) {
+            break;
+        }
+    }
+    handle
+        .send(Method::submit_text(
+            protocol::new_submission_request_id(),
+            "pause the first post-compact request",
+        ))
+        .await
+        .unwrap();
+
+    tokio::time::timeout(std::time::Duration::from_secs(2), async {
+        while call_count.load(Ordering::SeqCst) < 4 {
+            tokio::task::yield_now().await;
+        }
+    })
+    .await
+    .expect("post-compact provider request should start");
+    handle
+        .send(Method::Pause {
+            command: protocol::WorkerCommandEnvelope::new(1),
+        })
+        .await
+        .unwrap();
+    loop {
+        let event = tokio::time::timeout(std::time::Duration::from_secs(2), rx.recv())
+            .await
+            .expect("timeout waiting for pause")
+            .expect("event");
+        if matches!(
+            event,
+            Event::RunEnd {
+                result: RunResult::Paused
+            }
+        ) {
+            break;
+        }
+    }
+
+    let paused_usage = store
+        .list_segments(session_id)
+        .unwrap()
+        .into_iter()
+        .flat_map(|segment_id| store.read_all(session_id, segment_id).unwrap())
+        .filter_map(|entry| match entry {
+            LogEntry::LlmUsage {
+                input_total_tokens, ..
+            } => Some(input_total_tokens),
+            _ => None,
+        })
+        .collect::<Vec<_>>();
+    assert_eq!(
+        paused_usage.iter().filter(|tokens| **tokens == 90).count(),
+        1
+    );
+    let paused_metrics = session_metrics::read_session_metrics(&store, session_id).unwrap();
+    assert!(
+        paused_metrics
+            .iter()
+            .all(|record| record.metric.name != "compact.post_request"),
+        "partial Pause usage must not consume compact correlation or rearm"
+    );
+
+    handle
+        .send(Method::Resume {
+            command: protocol::WorkerCommandEnvelope::new(2),
+        })
+        .await
+        .unwrap();
+    loop {
+        if matches!(
+            tokio::time::timeout(std::time::Duration::from_secs(2), rx.recv())
+                .await
+                .expect("timeout waiting for resume completion")
+                .expect("event"),
+            Event::RunEnd {
+                result: RunResult::Finished
+            }
+        ) {
+            break;
+        }
+    }
+
+    assert_eq!(
+        call_count.load(Ordering::SeqCst),
+        8,
+        "the completed resumed request must rearm and permit request-threshold compaction"
+    );
+    let metrics = session_metrics::read_session_metrics(&store, session_id).unwrap();
+    let compact_starts = metrics
+        .iter()
+        .filter(|record| record.metric.name == "compact.start")
+        .collect::<Vec<_>>();
+    assert_eq!(compact_starts.len(), 2);
+    let pre_run_correlation = compact_starts
+        .iter()
+        .find(|record| {
+            record.metric.dimensions.get("trigger").map(String::as_str) == Some("pre_run")
+        })
+        .and_then(|record| record.metric.correlation_id.as_deref())
+        .expect("pre-run automatic compact correlation");
+    let pre_run_posts = metrics
+        .iter()
+        .filter(|record| {
+            record.metric.name == "compact.post_request"
+                && record.metric.correlation_id.as_deref() == Some(pre_run_correlation)
+        })
+        .collect::<Vec<_>>();
+    assert_eq!(pre_run_posts.len(), 1);
+    assert_eq!(
+        pre_run_posts[0].metric.dimensions["input_total_tokens"],
+        "80"
+    );
+    assert!(metrics.iter().all(|record| {
+        record.metric.name != "compact.post_request"
+            || record.metric.dimensions["input_total_tokens"] != "90"
+    }));
+
+    handle
+        .send(Method::Shutdown {
+            command: protocol::WorkerCommandEnvelope::new(3),
+        })
+        .await
+        .unwrap();
+    tokio::time::timeout(std::time::Duration::from_secs(2), shutdown_receiver)
+        .await
+        .expect("controller shutdown timeout")
+        .expect("shutdown confirmation");
+}
+
 #[tokio::test]
 async fn compacted_context_above_request_threshold_fails_before_provider_request() {
     let client = MockClient::new(vec![

crates/worker/tests/controller_test.rs

@@ -3,7 +3,9 @@ use std::sync::atomic::{AtomicU64, AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex};
 
 use agen::Engine;
-use agen::llm_client::event::{ErrorEvent, Event as LlmEvent, ResponseStatus, StatusEvent};
+use agen::llm_client::event::{
+    ErrorEvent, Event as LlmEvent, ResponseStatus, StatusEvent, UsageEvent,
+};
 use agen::llm_client::types::Item;
 use agen::llm_client::{ClientError, LlmClient, Request};
 use agen::tool::{Tool, ToolDefinition, ToolError, ToolMeta, ToolOutput};
@@ -349,7 +351,7 @@ async fn shutdown_closes_bound_workdir_session() {
         })
         .await
         .unwrap();
-    worker.bind_workdir_session(Some(Arc::clone(&session)));
+    worker.bind_single_workdir_session(Some(Arc::clone(&session)));
 
     let runtime_base = tempfile::tempdir().unwrap();
     let bash_output_dir = runtime_base.path().join("bash-output");
@@ -384,7 +386,7 @@ async fn controller_projects_workdir_command_events_and_snapshot_state() {
         worker.scope().clone(),
         WorkdirSessionCapabilities::ALL,
     ));
-    worker.bind_workdir_session(Some(Arc::clone(&session)));
+    worker.bind_single_workdir_session(Some(Arc::clone(&session)));
     let handle = spawn_controller(worker).await;
     let mut events = handle.subscribe();
 
@@ -495,7 +497,7 @@ async fn controller_refreshes_command_snapshot_after_high_output_provider_lag()
         worker.scope().clone(),
         WorkdirSessionCapabilities::ALL,
     ));
-    worker.bind_workdir_session(Some(Arc::clone(&session)));
+    worker.bind_single_workdir_session(Some(Arc::clone(&session)));
     let handle = spawn_controller(worker).await;
 
     // Local command telemetry uses 8 KiB chunks and a 256-event channel. One
@@ -572,7 +574,7 @@ async fn controller_startup_failure_closes_bound_workdir_session() {
         worker.scope().clone(),
         WorkdirSessionCapabilities::ALL,
     ));
-    worker.bind_workdir_session(Some(Arc::clone(&session)));
+    worker.bind_single_workdir_session(Some(Arc::clone(&session)));
     let runtime_base = tempfile::tempdir().unwrap();
     let invalid_runtime_base = runtime_base.path().join("not-a-directory");
     std::fs::write(&invalid_runtime_base, "file").unwrap();
@@ -2580,18 +2582,32 @@ async fn drain_until<F: FnMut(&Event) -> bool>(
 /// the interrupted turn's history consistency.
 #[tokio::test]
 async fn pause_then_resume_preserves_notifications_and_history_consistency() {
-    // Response 1: hang after opening a text block (no stop / completed),
-    // so the Engine is parked inside the stream read and `cancel_rx`
-    // races it cleanly on Method::Pause.
+    // Response 1: report billable partial usage, then hang after opening a text
+    // block (no stop / completed). Pause must flush that usage without treating
+    // the provider request as normally completed.
     let hang = MockResponse::Hang(vec![
         LlmEvent::text_block_start(0),
         LlmEvent::text_delta(0, "partial..."),
+        LlmEvent::Usage(UsageEvent {
+            input_tokens: Some(90),
+            output_tokens: Some(2),
+            total_tokens: Some(92),
+            cache_read_input_tokens: Some(0),
+            cache_creation_input_tokens: Some(0),
+        }),
     ]);
     // Response 2: a clean assistant reply delivered on Resume.
     let ok = MockResponse::Complete(vec![
         LlmEvent::text_block_start(0),
         LlmEvent::text_delta(0, "resumed output"),
         LlmEvent::text_block_stop(0, None),
+        LlmEvent::Usage(UsageEvent {
+            input_tokens: Some(100),
+            output_tokens: Some(3),
+            total_tokens: Some(103),
+            cache_read_input_tokens: Some(0),
+            cache_creation_input_tokens: Some(0),
+        }),
         LlmEvent::Status(StatusEvent {
             status: ResponseStatus::Completed,
         }),
@@ -2645,6 +2661,23 @@ async fn pause_then_resume_preserves_notifications_and_history_consistency() {
 
     tokio::time::sleep(std::time::Duration::from_millis(50)).await;
     assert_eq!(handle.shared_state.catalog_status(), WorkerStatus::Paused);
+    let (paused_entries, _) = handle.sink.subscribe_with_snapshot();
+    let paused_usage = paused_entries
+        .iter()
+        .filter_map(|entry| match entry {
+            LogEntry::LlmUsage {
+                input_total_tokens,
+                output_tokens,
+                ..
+            } => Some((*input_total_tokens, *output_tokens)),
+            _ => None,
+        })
+        .collect::<Vec<_>>();
+    assert_eq!(
+        paused_usage,
+        vec![(90, 2)],
+        "Pause must durably account for usage already observed on the interrupted request"
+    );
 
     handle
         .send(Method::Notify {
@@ -2729,6 +2762,23 @@ async fn pause_then_resume_preserves_notifications_and_history_consistency() {
         })
         .unwrap_or_default();
     assert_eq!(assistant_text, "resumed output");
+    let (final_entries, _) = handle.sink.subscribe_with_snapshot();
+    let final_usage = final_entries
+        .iter()
+        .filter_map(|entry| match entry {
+            LogEntry::LlmUsage {
+                input_total_tokens,
+                output_tokens,
+                ..
+            } => Some((*input_total_tokens, *output_tokens)),
+            _ => None,
+        })
+        .collect::<Vec<_>>();
+    assert_eq!(
+        final_usage,
+        vec![(90, 2), (100, 3)],
+        "the paused request must remain a distinct billing record rather than merging into resume"
+    );
     let has_tool_call = history.iter().any(|i| i.is_tool_call());
     assert!(!has_tool_call, "no orphan tool_call in history");
 }

crates/workspace-server/src/hosts.rs

@@ -32,8 +32,9 @@ use worker_runtime::catalog::{
     ConfigBundleRef, CreateWorkerRequest, ProfileSelector, ProfileSourceArchiveSource,
     RepositoryRefObservation, RepositoryRefObservationRequest,
     WorkerDetail as EmbeddedWorkerDetail, WorkerStatus as EmbeddedWorkerStatus,
-    WorkingDirectoryClaim, WorkingDirectoryRepositoryAccessRequest, WorkingDirectoryRequest,
-    WorkingDirectoryStatus, WorkingDirectorySummary, WorkspaceApiRef,
+    WorkingDirectoryAttachmentClaim, WorkingDirectoryAttachmentRequest,
+    WorkingDirectoryAttachmentStatus, WorkingDirectoryRepositoryAccessRequest,
+    WorkingDirectoryRequest, WorkingDirectoryStatus, WorkspaceApiRef,
 };
 use worker_runtime::config_bundle::{ConfigBundle, ConfigBundleAvailability, ConfigBundleSummary};
 #[cfg(test)]
@@ -270,8 +271,8 @@ pub struct WorkerSummary {
     pub retention_state: String,
     pub implementation: WorkerImplementationSummary,
     pub capabilities: WorkerCapabilitySummary,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory: Option<WorkingDirectorySummary>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachments: Vec<WorkingDirectoryAttachmentStatus>,
     pub diagnostics: Vec<RuntimeDiagnostic>,
 }
 
@@ -336,7 +337,7 @@ impl From<RuntimeSummary> for server_api::RuntimeSummary {
 pub(crate) fn workspace_worker_summary(
     summary: WorkerSummary,
     resource_key: String,
-    working_directory: Option<server_api::WorkingDirectorySummary>,
+    workdir_attachments: Vec<server_api::WorkerWorkdirAttachmentSummary>,
 ) -> server_api::WorkerSummary {
     server_api::WorkerSummary {
         runtime_id: summary.worker.runtime_id,
@@ -366,7 +367,7 @@ pub(crate) fn workspace_worker_summary(
             can_stop: summary.capabilities.can_stop,
             can_spawn_followup: summary.capabilities.can_spawn_followup,
         },
-        working_directory,
+        workdir_attachments,
         diagnostics: summary.diagnostics.into_iter().map(Into::into).collect(),
     }
 }
@@ -483,6 +484,13 @@ pub struct WorkerCreateBinding {
     pub create_fingerprint: String,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(deny_unknown_fields)]
+pub struct WorkerSpawnWorkingDirectoryAttachmentRequest {
+    pub alias: workdir::WorkdirAttachmentAlias,
+    pub working_directory: WorkerSpawnWorkingDirectoryRequest,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 #[serde(deny_unknown_fields)]
 pub struct WorkerSpawnRequest {
@@ -495,15 +503,13 @@ pub struct WorkerSpawnRequest {
     pub ticket_assignment: Option<WorkerTicketAssignmentRequest>,
     #[serde(default, skip_serializing_if = "Vec::is_empty")]
     pub initial_submit: Vec<Segment>,
-    /// Optional safe working-directory creation request. The Workspace server resolves
-    /// this into a runtime-internal `WorkingDirectoryRequest` from configured
-    /// repositories before calling a host.
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub working_directory_request: Option<WorkerSpawnWorkingDirectoryRequest>,
+    /// Safe working-directory materialization requests, keyed by stable Worker-local aliases.
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub workdir_attachment_requests: Vec<WorkerSpawnWorkingDirectoryAttachmentRequest>,
     #[serde(skip, default)]
-    pub resolved_working_directory_request: Option<WorkingDirectoryRequest>,
+    pub resolved_workdir_attachment_requests: Vec<WorkingDirectoryAttachmentRequest>,
     #[serde(skip, default)]
-    pub resolved_working_directory: Option<WorkingDirectoryClaim>,
+    pub resolved_workdir_attachments: Vec<WorkingDirectoryAttachmentClaim>,
     #[serde(skip, default)]
     pub resolved_config_bundle: Option<ConfigBundle>,
     #[serde(skip, default)]
@@ -905,6 +911,24 @@ pub trait WorkspaceWorkerRuntime: Send + Sync {
         }
     }
 
+    fn replace_worker_workdir_attachments(
+        &self,
+        worker_id: &str,
+        _attachments: Vec<WorkingDirectoryAttachmentClaim>,
+    ) -> WorkerWorkspaceApiResult {
+        WorkerWorkspaceApiResult {
+            state: WorkerOperationState::Unsupported,
+            worker: None,
+            diagnostics: vec![diagnostic(
+                "worker_workdir_attachments_replace_unsupported",
+                DiagnosticSeverity::Info,
+                format!(
+                    "runtime does not support replacing Workdir attachments for worker `{worker_id}`"
+                ),
+            )],
+        }
+    }
+
     fn create_working_directory(
         &self,
         _request: WorkingDirectoryRequest,
@@ -1489,6 +1513,19 @@ impl RuntimeRegistry {
         Ok(runtime.replace_worker_workspace_api(worker_id, workspace_api))
     }
 
+    pub fn replace_worker_workdir_attachments(
+        &self,
+        worker: &RuntimeWorkerRef,
+        attachments: Vec<WorkingDirectoryAttachmentClaim>,
+    ) -> Result<WorkerWorkspaceApiResult, RuntimeRegistryError> {
+        let runtime_id = worker.runtime_id.as_str();
+        let worker_id = worker.worker_id.as_str();
+        validate_backend_identifier("runtime_id", runtime_id)?;
+        validate_backend_identifier("worker_id", worker_id)?;
+        let runtime = self.runtime(runtime_id)?;
+        Ok(runtime.replace_worker_workdir_attachments(worker_id, attachments))
+    }
+
     pub fn observe_workspace_prompt_projection(
         &self,
         projection: worker::WorkspacePromptProjection,
@@ -2176,7 +2213,7 @@ impl EmbeddedWorkerRuntime {
                     && self.can_stop_embedded_worker(summary.status),
                 can_spawn_followup: false,
             },
-            working_directory: summary.working_directory.map(|status| status.summary),
+            workdir_attachments: summary.workdir_attachments,
             diagnostics: embedded_worker_projection_diagnostics(
                 summary.execution_metadata_available,
             ),
@@ -2220,7 +2257,7 @@ impl EmbeddedWorkerRuntime {
                     && self.can_stop_embedded_worker(detail.status),
                 can_spawn_followup: false,
             },
-            working_directory: detail.working_directory.map(|status| status.summary),
+            workdir_attachments: detail.workdir_attachments,
             diagnostics: embedded_worker_projection_diagnostics(
                 detail.execution_metadata_available,
             ),
@@ -2429,6 +2466,39 @@ impl WorkspaceWorkerRuntime for EmbeddedWorkerRuntime {
         }
     }
 
+    fn replace_worker_workdir_attachments(
+        &self,
+        worker_id: &str,
+        attachments: Vec<WorkingDirectoryAttachmentClaim>,
+    ) -> WorkerWorkspaceApiResult {
+        let Some(worker_ref) = self.worker_ref(worker_id) else {
+            return WorkerWorkspaceApiResult {
+                state: WorkerOperationState::Rejected,
+                worker: None,
+                diagnostics: vec![diagnostic(
+                    "embedded_worker_id_invalid",
+                    DiagnosticSeverity::Warning,
+                    "Worker id was empty and cannot change Workdir attachments".to_string(),
+                )],
+            };
+        };
+        match self
+            .runtime
+            .replace_worker_workdir_attachments(&worker_ref, attachments)
+        {
+            Ok(detail) => WorkerWorkspaceApiResult {
+                state: WorkerOperationState::Accepted,
+                worker: Some(self.map_worker_detail(detail)),
+                diagnostics: Vec::new(),
+            },
+            Err(err) => WorkerWorkspaceApiResult {
+                state: WorkerOperationState::Rejected,
+                worker: None,
+                diagnostics: vec![embedded_runtime_diagnostic(&err)],
+            },
+        }
+    }
+
     fn create_working_directory(
         &self,
         _request: WorkingDirectoryRequest,
@@ -2491,8 +2561,8 @@ impl WorkspaceWorkerRuntime for EmbeddedWorkerRuntime {
         request: WorkerSpawnRequest,
     ) -> WorkerSpawnResult {
         let mut diagnostics = Vec::new();
-        if request.resolved_working_directory_request.is_some()
-            || request.resolved_working_directory.is_some()
+        if !request.resolved_workdir_attachment_requests.is_empty()
+            || !request.resolved_workdir_attachments.is_empty()
         {
             diagnostics.push(embedded_workdir_unsupported_diagnostic());
             return WorkerSpawnResult {
@@ -2573,8 +2643,8 @@ impl WorkspaceWorkerRuntime for EmbeddedWorkerRuntime {
             config_bundle,
             profile_source,
             initial_input: initial_worker_input(&request.initial_submit),
-            working_directory_request: request.resolved_working_directory_request.clone(),
-            working_directory: request.resolved_working_directory.clone(),
+            workdir_attachment_requests: request.resolved_workdir_attachment_requests.clone(),
+            workdir_attachments: request.resolved_workdir_attachments.clone(),
             worker_observation_enabled: request.resolved_worker_observation_enabled,
             worker_observation_grants: request.resolved_worker_observation_grants.clone(),
             workspace_api: Some(workspace_api),
@@ -3982,7 +4052,7 @@ impl RemoteWorkerRuntime {
                     && runtime_worker_can_stop(true, summary.status),
                 can_spawn_followup: false,
             },
-            working_directory: summary.working_directory.map(|status| status.summary),
+            workdir_attachments: summary.workdir_attachments,
             diagnostics: remote_worker_projection_diagnostics(summary.execution_metadata_available),
         }
     }
@@ -4024,7 +4094,7 @@ impl RemoteWorkerRuntime {
                     && runtime_worker_can_stop(true, detail.status),
                 can_spawn_followup: false,
             },
-            working_directory: detail.working_directory.map(|status| status.summary),
+            workdir_attachments: detail.workdir_attachments,
             diagnostics: remote_worker_projection_diagnostics(detail.execution_metadata_available),
         }
     }
@@ -4388,6 +4458,51 @@ impl WorkspaceWorkerRuntime for RemoteWorkerRuntime {
         }
     }
 
+    fn replace_worker_workdir_attachments(
+        &self,
+        worker_id: &str,
+        attachments: Vec<WorkingDirectoryAttachmentClaim>,
+    ) -> WorkerWorkspaceApiResult {
+        let workdir_attachments = match runtime_contract_convert(attachments) {
+            Ok(attachments) => attachments,
+            Err(diagnostic) => {
+                return WorkerWorkspaceApiResult {
+                    state: WorkerOperationState::Rejected,
+                    worker: None,
+                    diagnostics: vec![diagnostic],
+                };
+            }
+        };
+        let request = runtime_api::WorkerWorkdirAttachmentsRequest {
+            workdir_attachments,
+        };
+        let worker_id = worker_id.to_string();
+        match self
+            .run_runtime_api(
+                self.request_timeout,
+                MAX_REMOTE_RUNTIME_RESPONSE_BYTES,
+                move |client| async move {
+                    client
+                        .replace_worker_workdir_attachments(worker_id, request)
+                        .await
+                },
+            )
+            .and_then(|value| {
+                runtime_contract_convert::<_, worker_runtime::catalog::WorkerDetail>(value.worker)
+            }) {
+            Ok(response) => WorkerWorkspaceApiResult {
+                state: WorkerOperationState::Accepted,
+                worker: Some(self.map_worker_detail(response)),
+                diagnostics: Vec::new(),
+            },
+            Err(diagnostic) => WorkerWorkspaceApiResult {
+                state: WorkerOperationState::Rejected,
+                worker: None,
+                diagnostics: vec![diagnostic],
+            },
+        }
+    }
+
     fn create_working_directory(
         &self,
         request: WorkingDirectoryRequest,
@@ -4567,8 +4682,8 @@ impl WorkspaceWorkerRuntime for RemoteWorkerRuntime {
             config_bundle,
             profile_source,
             initial_input: initial_worker_input(&request.initial_submit),
-            working_directory_request: request.resolved_working_directory_request.clone(),
-            working_directory: request.resolved_working_directory.clone(),
+            workdir_attachment_requests: request.resolved_workdir_attachment_requests.clone(),
+            workdir_attachments: request.resolved_workdir_attachments.clone(),
             worker_observation_enabled: request.resolved_worker_observation_enabled,
             worker_observation_grants: request.resolved_worker_observation_grants.clone(),
             workspace_api: Some(workspace_api),
@@ -5724,7 +5839,7 @@ pub fn placeholder_worker(host_id: impl Into<String>) -> WorkerSummary {
             can_stop: false,
             can_spawn_followup: false,
         },
-        working_directory: None,
+        workdir_attachments: Vec::new(),
         diagnostics: vec![diagnostic(
             "runtime_capability_unsupported",
             DiagnosticSeverity::Info,
@@ -6265,10 +6380,16 @@ mod tests {
                 worker_state: protocol::WorkerStateSnapshot {
                     ..protocol::WorkerStatus::Idle.into()
                 },
-                working_directory: request
-                    .working_directory
-                    .as_ref()
-                    .map(|binding| binding.status()),
+                workdir_attachments: request
+                    .workdir_attachments
+                    .iter()
+                    .map(|(alias, binding)| {
+                        worker_runtime::catalog::WorkingDirectoryAttachmentStatus {
+                            alias: alias.clone(),
+                            working_directory: binding.status(),
+                        }
+                    })
+                    .collect(),
             }
         }
 
@@ -6360,7 +6481,7 @@ mod tests {
                         can_stop: false,
                         can_spawn_followup: false,
                     },
-                    working_directory: None,
+                    workdir_attachments: Vec::new(),
                     diagnostics: Vec::new(),
                 }],
                 observed_prompt_revisions: Arc::new(Mutex::new(Vec::new())),
@@ -6650,9 +6771,9 @@ mod tests {
             profile: ProfileSelector::Builtin("builtin:coder".to_string()),
             ticket_assignment: None,
             initial_submit: Vec::new(),
-            working_directory_request: None,
-            resolved_working_directory_request: None,
-            resolved_working_directory: None,
+            workdir_attachment_requests: Vec::new(),
+            resolved_workdir_attachment_requests: Vec::new(),
+            resolved_workdir_attachments: Vec::new(),
             resolved_config_bundle: None,
             resolved_worker_observation_enabled: false,
             resolved_worker_observation_grants: Vec::new(),
@@ -6890,9 +7011,9 @@ mod tests {
                     profile: ProfileSelector::Builtin("builtin:coder".to_string()),
                     ticket_assignment: None,
                     initial_submit: Vec::new(),
-                    working_directory_request: None,
-                    resolved_working_directory_request: None,
-                    resolved_working_directory: None,
+                    workdir_attachment_requests: Vec::new(),
+                    resolved_workdir_attachment_requests: Vec::new(),
+                    resolved_workdir_attachments: Vec::new(),
                     resolved_config_bundle: None,
                     resolved_worker_observation_enabled: false,
                     resolved_worker_observation_grants: Vec::new(),
@@ -6990,9 +7111,9 @@ mod tests {
                     profile: ProfileSelector::Builtin("builtin:coder".to_string()),
                     ticket_assignment: None,
                     initial_submit: Vec::new(),
-                    working_directory_request: None,
-                    resolved_working_directory_request: None,
-                    resolved_working_directory: None,
+                    workdir_attachment_requests: Vec::new(),
+                    resolved_workdir_attachment_requests: Vec::new(),
+                    resolved_workdir_attachments: Vec::new(),
                     resolved_config_bundle: None,
                     resolved_worker_observation_enabled: false,
                     resolved_worker_observation_grants: Vec::new(),
@@ -7029,9 +7150,9 @@ mod tests {
                     profile: ProfileSelector::Builtin("builtin:companion".to_string()),
                     ticket_assignment: None,
                     initial_submit: Vec::new(),
-                    working_directory_request: None,
-                    resolved_working_directory_request: None,
-                    resolved_working_directory: None,
+                    workdir_attachment_requests: Vec::new(),
+                    resolved_workdir_attachment_requests: Vec::new(),
+                    resolved_workdir_attachments: Vec::new(),
                     resolved_config_bundle: None,
                     resolved_worker_observation_enabled: false,
                     resolved_worker_observation_grants: Vec::new(),

crates/workspace-server/src/latest_schema.sql

@@ -667,6 +667,7 @@ CREATE TABLE workdir_create_credential_revision_retentions (
 CREATE TABLE "workdir_registry" (
     workspace_id TEXT NOT NULL,
     workdir_id TEXT NOT NULL,
+    display_name TEXT,
     runtime_id TEXT NOT NULL,
     repository_id TEXT NOT NULL,
     creation_selector TEXT,
@@ -859,10 +860,10 @@ CREATE TABLE "worker_workdir_links" (
             runtime_id TEXT NOT NULL,
             worker_id TEXT NOT NULL,
             workdir_id TEXT NOT NULL,
-            role TEXT NOT NULL,
+            alias TEXT NOT NULL,
             linked_at TEXT NOT NULL,
             unlinked_at TEXT,
-            PRIMARY KEY (workspace_id, worker_id, workdir_id, role),
+            PRIMARY KEY (workspace_id, worker_id, workdir_id, alias),
             FOREIGN KEY (workspace_id, worker_id)
                 REFERENCES "worker_registry"(workspace_id, worker_id) ON DELETE CASCADE,
             FOREIGN KEY (workspace_id, workdir_id)
@@ -1093,8 +1094,8 @@ CREATE INDEX worker_removal_operations_worker_idx ON worker_removal_operations(w
 CREATE UNIQUE INDEX worker_workdir_links_active_workdir_unique
             ON worker_workdir_links(workspace_id, workdir_id)
             WHERE unlinked_at IS NULL;
-CREATE UNIQUE INDEX worker_workdir_links_active_worker_unique
-            ON worker_workdir_links(workspace_id, worker_id)
+CREATE UNIQUE INDEX worker_workdir_links_active_alias_unique
+            ON worker_workdir_links(workspace_id, worker_id, alias)
             WHERE unlinked_at IS NULL;
 CREATE INDEX worker_workdir_links_workdir
             ON worker_workdir_links(workspace_id, workdir_id);

crates/workspace-server/src/retention.rs

@@ -2,7 +2,10 @@
 //! Runtime receives only resolved dispositions and stable ids; policy authority
 //! never comes from prompts, profiles, or model input.
 
-use crate::{Error as StoreError, store::SqliteWorkspaceStore};
+use crate::{
+    Error as StoreError,
+    store::{SqliteWorkspaceStore, WorkerRemovalCommit, commit_worker_catalog_removal},
+};
 use chrono::Utc;
 use rusqlite::{Connection, OptionalExtension, TransactionBehavior, params};
 use serde::{Deserialize, Serialize};
@@ -417,13 +420,19 @@ impl SqliteWorkspaceStore {
         operation_id: &str,
         fp: &str,
         result: &WorkerRetentionExecutionResult,
-    ) -> Result<WorkerRemovalPlan, WorkerRetentionError> {
+    ) -> Result<WorkerRemovalCommit, WorkerRetentionError> {
         self.with_conn_mut(|conn|{
             let tx=conn.transaction_with_behavior(TransactionBehavior::Immediate)?;
             let mut plan=load_plan_op(&tx,operation_id)?.ok_or_else(||StoreError::InvalidInput("operation missing".into()))?;
             if plan.workspace_id!=workspace_id{return Err(StoreError::InvalidInput("cross-workspace".into()));}
             if plan.input_fingerprint!=fp||result.input_fingerprint!=fp||result.operation_id!=operation_id{return Err(StoreError::InvalidInput(format!("fingerprint:{operation_id}")));}
-            if plan.state==WorkerRemovalPlanState::Succeeded{tx.commit()?;return Ok(plan);}
+            if plan.state==WorkerRemovalPlanState::Succeeded{
+                // Repair projection fences left by the pre-atomic implementation and
+                // return a replayable change for a broadcast missed after commit.
+                let catalog=commit_worker_catalog_removal(&tx,workspace_id,&plan.worker)?;
+                tx.commit()?;
+                return Ok(WorkerRemovalCommit { plan, catalog });
+            }
             if plan.state != WorkerRemovalPlanState::Executing {
                 return Err(StoreError::InvalidInput(format!("stale:{}:plan state {} is not committable", plan.plan_id, state_s(plan.state))));
             }
@@ -460,12 +469,14 @@ impl SqliteWorkspaceStore {
             if plan.metadata_disposition==MetadataDisposition::Tombstone{
                 tx.execute("INSERT OR IGNORE INTO worker_tombstones(workspace_id,runtime_id,worker_id,display_name,profile,worker_created_at,removed_at,archive_id,policy_id,policy_revision,operation_id) VALUES(?1,?2,?3,?4,?5,?6,?7,?8,?9,?10,?11)",params![workspace_id,plan.worker.runtime_id,plan.worker.worker_id,worker.display_name,worker.profile,worker.created_at,now,plan.archive_id,plan.policy_id,plan.policy_revision,operation_id])?;
             }
+            tx.execute("UPDATE worker_workdir_links SET unlinked_at=?4 WHERE workspace_id=?1 AND runtime_id=?2 AND worker_id=?3 AND unlinked_at IS NULL",params![workspace_id,plan.worker.runtime_id,plan.worker.worker_id,now])?;
             let deleted=tx.execute("DELETE FROM worker_registry WHERE workspace_id=?1 AND runtime_id=?2 AND worker_id=?3 AND updated_at=?4",params![workspace_id,plan.worker.runtime_id,plan.worker.worker_id,plan.worker_revision])?;
             tx.execute("UPDATE worker_create_reservations SET state='removed',updated_at=?4 WHERE workspace_id=?1 AND runtime_id=?2 AND worker_id=?3 AND state='created'",params![workspace_id,plan.worker.runtime_id,plan.worker.worker_id,now])?;
             if deleted!=1{return Err(StoreError::InvalidInput(format!("stale:{}:removal fence changed",plan.plan_id)));}
+            let catalog=commit_worker_catalog_removal(&tx,workspace_id,&plan.worker)?;
             tx.execute("UPDATE worker_removal_operations SET state='succeeded',failure_category=NULL,updated_at=?1 WHERE operation_id=?2",params![now,operation_id])?;
             tx.execute("INSERT OR IGNORE INTO worker_retention_audit_events(event_id,operation_id,workspace_id,event_kind,detail,created_at) VALUES(?1,?2,?3,'worker_removed',?4,?5)",params![stable("wre",operation_id),operation_id,workspace_id,format!("runtime_id={} worker_id={} session={} metadata={} diagnostics={}",plan.worker.runtime_id,plan.worker.worker_id,sess(plan.session_disposition),meta(plan.metadata_disposition),diag(plan.diagnostics_disposition)),now])?;
-            tx.commit()?;plan.state=WorkerRemovalPlanState::Succeeded;plan.updated_at=now;Ok(plan)
+            tx.commit()?;plan.state=WorkerRemovalPlanState::Succeeded;plan.updated_at=now;Ok(WorkerRemovalCommit { plan, catalog })
         }).map_err(map_error)
     }
 
@@ -948,7 +959,9 @@ fn parse_state(v: &str) -> rusqlite::Result<WorkerRemovalPlanState> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::store::{ControlPlaneStore, TicketCoderAssignmentRecord, WorkerRegistryRecord};
+    use crate::store::{
+        ControlPlaneStore, TicketCoderAssignmentRecord, WorkerCatalogChange, WorkerRegistryRecord,
+    };
     use worker_runtime::identity::WorkerId;
     fn worker_id() -> WorkerId {
         WorkerId::from_legacy_u64(1)
@@ -1203,6 +1216,7 @@ mod tests {
         assert_eq!(
             s.commit_worker_removal("w", &p.operation_id, &p.input_fingerprint, &result)
                 .unwrap()
+                .plan
                 .state,
             WorkerRemovalPlanState::Succeeded
         );
@@ -1219,6 +1233,7 @@ mod tests {
         assert_eq!(
             s.commit_worker_removal("w", &p.operation_id, &p.input_fingerprint, &result)
                 .unwrap()
+                .plan
                 .state,
             WorkerRemovalPlanState::Succeeded
         );
@@ -1351,6 +1366,98 @@ mod tests {
             .unwrap();
         assert!(s.worker_tombstone("w", &p.worker).unwrap().is_none());
     }
+    #[test]
+    fn terminal_catalog_failure_rolls_back_removal_projection_and_operation() {
+        let store = setup();
+        let purge = WorkerRetentionPolicyUpdate {
+            policy_id: "purge".into(),
+            session_disposition: SessionDisposition::Purge,
+            metadata_disposition: MetadataDisposition::Tombstone,
+            archive_retention: ArchiveRetention::Forever,
+            diagnostics_disposition: DiagnosticsDisposition::Purge,
+            diagnostics_retention_seconds: None,
+        };
+        store
+            .update_worker_retention_policy("w", 1, &purge)
+            .unwrap();
+        let plan = store.plan_worker_removal(&req(), &inv()).unwrap();
+        store
+            .prepare_worker_removal_execution("w", &plan.plan_id, &plan.input_fingerprint)
+            .unwrap();
+        let result = WorkerRetentionExecutionResult {
+            operation_id: plan.operation_id.clone(),
+            input_fingerprint: plan.input_fingerprint.clone(),
+            expected_worker_revision: plan.worker_revision.clone(),
+            worker_id: worker_id(),
+            session_disposition: SessionDisposition::Purge,
+            diagnostics_disposition: DiagnosticsDisposition::Purge,
+            archive: None,
+            source_removed: true,
+            diagnostics_retained: false,
+        };
+        store
+            .with_conn(|conn| {
+                conn.execute_batch(
+                    "CREATE TRIGGER fail_worker_projection_removal
+                     BEFORE INSERT ON worker_registry_projection_removals
+                     BEGIN SELECT RAISE(ABORT, 'injected projection failure'); END;",
+                )?;
+                Ok(())
+            })
+            .unwrap();
+
+        assert!(
+            store
+                .commit_worker_removal("w", &plan.operation_id, &plan.input_fingerprint, &result,)
+                .is_err()
+        );
+        let (registry, removal, state, tombstone): (i64, i64, String, i64) = store
+            .with_conn(|conn| {
+                Ok((
+                    conn.query_row(
+                        "SELECT COUNT(*) FROM worker_registry WHERE workspace_id='w' AND runtime_id='r' AND worker_id=?1",
+                        [worker_id().to_string()],
+                        |row| row.get(0),
+                    )?,
+                    conn.query_row(
+                        "SELECT COUNT(*) FROM worker_registry_projection_removals WHERE workspace_id='w' AND runtime_id='r' AND worker_id=?1",
+                        [worker_id().to_string()],
+                        |row| row.get(0),
+                    )?,
+                    conn.query_row(
+                        "SELECT state FROM worker_removal_operations WHERE operation_id=?1",
+                        [&plan.operation_id],
+                        |row| row.get(0),
+                    )?,
+                    conn.query_row(
+                        "SELECT COUNT(*) FROM worker_tombstones WHERE workspace_id='w' AND runtime_id='r' AND worker_id=?1",
+                        [worker_id().to_string()],
+                        |row| row.get(0),
+                    )?,
+                ))
+            })
+            .unwrap();
+        assert_eq!(registry, 1, "catalog deletion must roll back");
+        assert_eq!(removal, 0, "removal fence must not partially commit");
+        assert_eq!(state, "executing", "operation must remain recoverable");
+        assert_eq!(tombstone, 0, "retention metadata must roll back");
+
+        store
+            .with_conn(|conn| {
+                conn.execute_batch("DROP TRIGGER fail_worker_projection_removal;")?;
+                Ok(())
+            })
+            .unwrap();
+        let committed = store
+            .commit_worker_removal("w", &plan.operation_id, &plan.input_fingerprint, &result)
+            .unwrap();
+        assert!(matches!(
+            committed.catalog.changes.as_slice(),
+            [WorkerCatalogChange::Removed(worker)] if worker == &plan.worker
+        ));
+        assert_eq!(committed.plan.state, WorkerRemovalPlanState::Succeeded);
+    }
+
     #[test]
     fn commit_requires_executing_state_and_exact_runtime_result() {
         let store = setup();
@@ -1597,6 +1704,26 @@ mod tests {
                 .unwrap()
                 .is_none()
         );
+        s.with_conn(|conn| {
+            conn.execute(
+                "DELETE FROM worker_registry_projection_removals WHERE workspace_id='w' AND runtime_id='r' AND worker_id=?1",
+                [worker_id().to_string()],
+            )?;
+            Ok(())
+        })
+        .unwrap();
+        let repaired = s
+            .recover_succeeded_worker_removal_catalog("w", &request.worker)
+            .unwrap();
+        assert!(matches!(
+            repaired.changes.as_slice(),
+            [WorkerCatalogChange::Removed(worker)] if worker == &request.worker
+        ));
+        assert!(
+            s.get_worker_registry("w", &request.worker)
+                .unwrap()
+                .is_none()
+        );
         let recovered = s
             .recover_worker_removal_execution("w", &request.worker)
             .unwrap()

crates/workspace-server/src/runtime_subscription_tests.rs

@@ -22,7 +22,7 @@ impl WorkerExecutionBackend for TestExecutionBackend {
             protocol::WorkerStateSnapshot {
                 ..protocol::WorkerStatus::Idle.into()
             },
-            None,
+            Vec::new(),
         )
     }
 
@@ -64,8 +64,8 @@ fn create_request(name: &str) -> CreateWorkerRequest {
             .unwrap(),
         },
         initial_input: None,
-        working_directory_request: None,
-        working_directory: None,
+        workdir_attachment_requests: Vec::new(),
+        workdir_attachments: Vec::new(),
         worker_observation_enabled: false,
         worker_observation_grants: Vec::new(),
         workspace_api: None,

crates/workspace-server/src/workdir_create_operations.rs

@@ -25,6 +25,7 @@ pub fn request_fingerprint(
     repository_id: &str,
     selector: Option<&str>,
     requested_runtime_id: Option<&str>,
+    display_name: Option<&str>,
     repository_source_fingerprint: &str,
     repository_source_revision: u64,
 ) -> String {
@@ -33,6 +34,7 @@ pub fn request_fingerprint(
         Some(repository_id),
         selector,
         requested_runtime_id,
+        display_name,
         Some(repository_source_fingerprint),
     ] {
         match value {
@@ -569,6 +571,7 @@ mod tests {
                 "main",
                 Some("develop"),
                 None,
+                None,
                 "sha256:test",
                 1,
             ),
@@ -718,7 +721,7 @@ mod tests {
         );
         let mut changed_input = record.clone();
         changed_input.request_fingerprint =
-            request_fingerprint("main", Some("main"), None, "sha256:test", 1);
+            request_fingerprint("main", Some("main"), None, None, "sha256:test", 1);
         assert!(
             store
                 .reserve_workdir_create_operation(&changed_input)

crates/workspace-server/src/workdir_removal.rs

@@ -716,7 +716,7 @@ fn load_workdir_record(
     workdir_id: &str,
 ) -> Result<Option<WorkdirRegistryRecord>> {
     conn.query_row(
-        r#"SELECT workspace_id, workdir_id, runtime_id, repository_id,
+        r#"SELECT workspace_id, workdir_id, display_name, runtime_id, repository_id,
                   creation_selector, creation_ref, creation_tree,
                   current_selector, current_ref, current_tree, observed_at_epoch_seconds,
                   materialization_status, cleanliness, created_at, updated_at
@@ -726,19 +726,20 @@ fn load_workdir_record(
             Ok(WorkdirRegistryRecord {
                 workspace_id: row.get(0)?,
                 workdir_id: row.get(1)?,
-                runtime_id: row.get(2)?,
-                repository_id: row.get(3)?,
-                creation_selector: row.get(4)?,
-                creation_ref: row.get(5)?,
-                creation_tree: row.get(6)?,
-                current_selector: row.get(7)?,
-                current_ref: row.get(8)?,
-                current_tree: row.get(9)?,
-                observed_at_epoch_seconds: row.get::<_, Option<i64>>(10)?.map(|value| value as u64),
-                materialization_status: row.get(11)?,
-                cleanliness: row.get(12)?,
-                created_at: row.get(13)?,
-                updated_at: row.get(14)?,
+                display_name: row.get(2)?,
+                runtime_id: row.get(3)?,
+                repository_id: row.get(4)?,
+                creation_selector: row.get(5)?,
+                creation_ref: row.get(6)?,
+                creation_tree: row.get(7)?,
+                current_selector: row.get(8)?,
+                current_ref: row.get(9)?,
+                current_tree: row.get(10)?,
+                observed_at_epoch_seconds: row.get::<_, Option<i64>>(11)?.map(|value| value as u64),
+                materialization_status: row.get(12)?,
+                cleanliness: row.get(13)?,
+                created_at: row.get(14)?,
+                updated_at: row.get(15)?,
             })
         },
     )
@@ -934,6 +935,7 @@ mod tests {
         let workdir = WorkdirRegistryRecord {
             workspace_id: "workspace-a".to_string(),
             workdir_id: "workdir-a".to_string(),
+            display_name: None,
             runtime_id: "runtime-a".to_string(),
             repository_id: "repository-a".to_string(),
             creation_selector: Some("refs/heads/develop".to_string()),

crates/workspace-server/src/worker_projection.rs

@@ -11,18 +11,12 @@ use tokio::task::JoinHandle;
 use crate::runtime_subscription::{
     BrokerSubscriptionEvent, RuntimeSubscriptionBroker, RuntimeSubscriptionBrokerError,
 };
-use crate::store::{
-    ControlPlaneStore, WorkerRegistryProjectionCommit, WorkerRegistryProjectionRecord,
-};
+use crate::store::{ControlPlaneStore, WorkerCatalogChange, WorkerRegistryProjectionCommit};
 use worker_runtime::identity::RuntimeWorkerRef;
 
 const PROJECTION_EVENT_CAPACITY: usize = 256;
 
-#[derive(Debug, Clone)]
-pub enum WorkerProjectionChange {
-    Upsert(WorkerRegistryProjectionRecord),
-    Removed(RuntimeWorkerRef),
-}
+pub type WorkerProjectionChange = WorkerCatalogChange;
 
 #[derive(Debug, Clone)]
 pub struct WorkerProjectionEvent {
@@ -144,27 +138,13 @@ impl WorkerProjectionService {
         self.publish_commit(commit)
     }
 
-    pub fn publish_catalog_change(&self, worker: &RuntimeWorkerRef) -> crate::Result<()> {
+    pub fn refresh(&self, worker: &RuntimeWorkerRef) -> crate::Result<()> {
         let commit = self
             .store
-            .publish_worker_registry_catalog_change(self.workspace_id.as_str(), worker)?;
+            .commit_worker_registry_projection_refresh(self.workspace_id.as_str(), worker)?;
         self.publish_commit(commit)
     }
 
-    pub fn publish_removed(&self, worker: RuntimeWorkerRef) -> crate::Result<()> {
-        let commit = self
-            .store
-            .publish_worker_registry_removal(self.workspace_id.as_str(), &worker)?;
-        if commit.changed_workers.is_empty() {
-            return Ok(());
-        }
-        let _ = self.events.send(WorkerProjectionEvent {
-            revision: commit.revision,
-            changes: vec![WorkerProjectionChange::Removed(worker)],
-        });
-        Ok(())
-    }
-
     async fn apply_broker_event(
         &self,
         runtime_id: &str,
@@ -236,38 +216,21 @@ impl WorkerProjectionService {
         self.publish_commit(commit)
     }
 
-    fn publish_commit(&self, commit: WorkerRegistryProjectionCommit) -> crate::Result<()> {
-        if commit.changed_workers.is_empty() {
+    /// Broadcast an already committed catalog payload. Persistence always happens
+    /// before this call; a process crash therefore closes subscribers, whose next
+    /// subscription starts from the durable snapshot. Retrying a removal returns
+    /// the same durable change and can heal an in-process missed broadcast.
+    pub(crate) fn publish_commit(
+        &self,
+        commit: WorkerRegistryProjectionCommit,
+    ) -> crate::Result<()> {
+        if commit.changes.is_empty() {
             return Ok(());
         }
-        let changes = commit
-            .changed_workers
-            .iter()
-            .filter_map(|worker| {
-                match self
-                    .store
-                    .worker_registry_projection(self.workspace_id.as_str(), worker)
-                {
-                    Ok(Some(record)) => Some(WorkerProjectionChange::Upsert(record)),
-                    Ok(None) => None,
-                    Err(error) => {
-                        tracing::warn!(
-                            runtime_id = %worker.runtime_id,
-                            worker_id = %worker.worker_id,
-                            error = %error,
-                            "failed to load committed Worker projection"
-                        );
-                        None
-                    }
-                }
-            })
-            .collect::<Vec<_>>();
-        if !changes.is_empty() {
-            let _ = self.events.send(WorkerProjectionEvent {
-                revision: commit.revision,
-                changes,
-            });
-        }
+        let _ = self.events.send(WorkerProjectionEvent {
+            revision: commit.revision,
+            changes: commit.changes,
+        });
         Ok(())
     }
 }

crates/workspace-server/src/workspace_deletion.rs

@@ -1198,7 +1198,7 @@ mod tests {
         );
 
         assert!(
-            store
+            !store
                 .delete_worker_registry(
                     &workspace_id,
                     &worker_runtime::identity::RuntimeWorkerRef {
@@ -1207,6 +1207,8 @@ mod tests {
                     },
                 )
                 .expect("remove worker registry")
+                .changes
+                .is_empty()
         );
         let state: String = store
             .with_conn(|conn| {

crates/workspace-server/src/workspace_subscription.rs

@@ -413,9 +413,7 @@ fn project_registry_worker(
             workspace_id: Some(record.registry.workspace_id.clone()),
             display_name: Some(record.registry.display_name.clone()),
             profile: record.registry.profile.clone(),
-            repository_id: None,
-            repository_key: None,
-            working_directory_id: None,
+            workdir_attachments: Vec::new(),
         }
     };
     worker.runtime_id = Some(runtime_id);
@@ -440,20 +438,30 @@ fn project_working_directory(
     else {
         return false;
     };
-    if let Some(link) = links.first() {
-        let Ok(Some(workdir)) = api
-            .store
-            .get_workdir_registry(&api.config.workspace_id, &link.workdir_id)
-        else {
-            return false;
-        };
-        let Ok(working_directory_id) =
-            protocol::subscription::SubscriptionWorkdirId::new(workdir.workdir_id)
-        else {
-            return false;
-        };
-        worker.repository_id = Some(workdir.repository_id);
-        worker.working_directory_id = Some(working_directory_id);
+    if !links.is_empty() {
+        let mut attachments = Vec::with_capacity(links.len());
+        for link in links {
+            let Ok(Some(workdir)) = api
+                .store
+                .get_workdir_registry(&api.config.workspace_id, &link.workdir_id)
+            else {
+                return false;
+            };
+            let Ok(working_directory_id) =
+                protocol::subscription::SubscriptionWorkdirId::new(workdir.workdir_id)
+            else {
+                return false;
+            };
+            attachments.push(
+                protocol::subscription::SubscriptionWorkerWorkdirAttachment {
+                    alias: link.alias,
+                    repository_id: Some(workdir.repository_id),
+                    repository_key: None,
+                    working_directory_id,
+                },
+            );
+        }
+        worker.workdir_attachments = attachments;
     } else {
         let Ok(has_link_history) = api
             .store
@@ -462,26 +470,28 @@ fn project_working_directory(
             return false;
         };
         if has_link_history {
-            worker.repository_id = None;
-            worker.repository_key = None;
-            worker.working_directory_id = None;
+            worker.workdir_attachments.clear();
         }
     }
-    project_repository_key(api, worker)
+    project_repository_keys(api, worker)
 }
 
-fn project_repository_key(api: &WorkspaceApi, worker: &mut SubscriptionWorker) -> bool {
-    let Some(repository_id) = worker.repository_id.take() else {
-        worker.repository_key = None;
-        return true;
-    };
-    let Ok(Some(repository)) = api
-        .store
-        .get_repository(&api.config.workspace_id, &repository_id)
-    else {
-        return false;
-    };
-    worker.repository_key = Some(repository.repository_key);
+fn project_repository_keys(api: &WorkspaceApi, worker: &mut SubscriptionWorker) -> bool {
+    for attachment in &mut worker.workdir_attachments {
+        let Some(repository_id) = attachment.repository_id.take() else {
+            if attachment.repository_key.is_none() {
+                return false;
+            }
+            continue;
+        };
+        let Ok(Some(repository)) = api
+            .store
+            .get_repository(&api.config.workspace_id, &repository_id)
+        else {
+            return false;
+        };
+        attachment.repository_key = Some(repository.repository_key);
+    }
     true
 }
 

web/workspace/src/lib/generated/protocol.ts

@@ -236,6 +236,12 @@ export type SubscriptionWorkerAvailability = "observed" | "unavailable";
 
 export type EventSubscriptionSelector = { "topic": "runtime_workers" } | { "topic": "worker_lifecycle", worker_ids: SubscriptionWorkerIds, } | { "topic": "worker_protocol", worker_id: SubscriptionWorkerId, runtime_id?: string | null, } | { "topic": "workspace_workers" } | { "topic": "workspace_workdirs" };
 
+export type SubscriptionWorkerWorkdirAttachment = {
+/**
+ * Stable Worker-local routing alias.
+ */
+alias: string, repository_key?: string | null, working_directory_id: SubscriptionWorkdirId, };
+
 export type SubscriptionWorker = { worker_id: SubscriptionWorkerId,
 /**
  * Set by the Workspace Server when projecting a Runtime-owned Worker to clients.
@@ -264,14 +270,9 @@ worker_state?: WorkerStateSnapshot | null,
 /**
  * Runtime catalog lifecycle compatibility projection; not foreground-state authority.
  */
-state: SubscriptionWorkerState, has_running_internal_workers: boolean, workspace_id?: string | null, display_name?: string | null, profile?: string | null,
-/**
- * Workspace-facing Repository key. Runtime producers leave this unset and
- * Workspace Server projections replace `repository_id` with this field.
- */
-repository_key?: string | null, working_directory_id?: SubscriptionWorkdirId | null, };
+state: SubscriptionWorkerState, has_running_internal_workers: boolean, workspace_id?: string | null, display_name?: string | null, profile?: string | null, workdir_attachments?: Array<SubscriptionWorkerWorkdirAttachment>, };
 
-export type WorkspaceSubscriptionWorkdir = { working_directory_id: SubscriptionWorkdirId, repository_key: string, state: string, primary_worker_id?: SubscriptionWorkerId | null, };
+export type WorkspaceSubscriptionWorkdir = { working_directory_id: SubscriptionWorkdirId, repository_key: string, state: string, };
 
 export type SubscriptionSnapshot = { "topic": "workers", "data": { workers: Array<SubscriptionWorker>, } } | { "topic": "worker_protocol", "data": { worker_id: SubscriptionWorkerId, events: Array<Event>, } } | { "topic": "workspace_workdirs", "data": { workdirs: Array<WorkspaceSubscriptionWorkdir>, } };
 

web/workspace/src/lib/generated/workdir-api.ts

@@ -13,9 +13,17 @@ export type WorkingDirectoryCleanupTarget = { kind: string, working_directory_id
 
 export type WorkingDirectoryOccupancy = { runtime_id: string, worker_id: string, display_name: string, linked_at: string, };
 
-export type WorkingDirectorySummary = { working_directory_id: string, repository_key: string, creation_selector?: string | null, creation_ref?: string | null, creation_tree?: string | null, current_selector?: string | null, current_ref?: string | null, current_tree?: string | null, observed_at_epoch_seconds?: number | null, materializer_kind: WorkingDirectoryMaterializerKind, cleanup_target?: WorkingDirectoryCleanupTarget | null, status: WorkingDirectoryStatusKind, cleanliness?: string | null, primary_worker_id?: string | null, occupied_by?: WorkingDirectoryOccupancy | null, };
+export type WorkingDirectorySummary = { working_directory_id: string,
+/**
+ * Optional human-facing label, never a routing key.
+ */
+display_name?: string | null, repository_key: string, creation_selector?: string | null, creation_ref?: string | null, creation_tree?: string | null, current_selector?: string | null, current_ref?: string | null, current_tree?: string | null, observed_at_epoch_seconds?: number | null, materializer_kind: WorkingDirectoryMaterializerKind, cleanup_target?: WorkingDirectoryCleanupTarget | null, status: WorkingDirectoryStatusKind, cleanliness?: string | null, occupied_by?: WorkingDirectoryOccupancy | null, };
 
-export type WorkingDirectoryCreateRequest = { runtime_id?: string | null, repository_key: string, selector?: string | null, operation_id?: string | null, };
+export type WorkingDirectoryCreateRequest = { runtime_id?: string | null,
+/**
+ * Optional human-facing label, independent of every Worker attachment alias.
+ */
+display_name?: string | null, repository_key: string, selector?: string | null, operation_id?: string | null, };
 
 export type WorkingDirectoryListResponse = { workspace_id: string, items: Array<WorkingDirectorySummary>, diagnostics: Array<Diagnostic>, };
 

web/workspace/src/lib/generated/worker-launch-api.ts

@@ -15,11 +15,19 @@ export type WorkingDirectoryCleanupTarget = { kind: string, working_directory_id
 
 export type RuntimeWorkingDirectoryCleanupTarget = { kind: string, working_directory_id: string, repository_id: string, };
 
-export type RuntimeWorkingDirectorySummary = { working_directory_id: string, repository_id: string, creation_selector?: string | null, creation_ref?: string | null, creation_tree?: string | null, current_selector?: string | null, current_ref?: string | null, current_tree?: string | null, observed_at_epoch_seconds?: number | null, materializer_kind: WorkingDirectoryMaterializerKind, cleanup_target?: RuntimeWorkingDirectoryCleanupTarget | null, status: WorkingDirectoryStatusKind, cleanliness?: string | null, primary_worker_id?: string | null, occupied_by?: WorkingDirectoryOccupancy | null, };
+export type RuntimeWorkingDirectorySummary = { working_directory_id: string,
+/**
+ * Optional human-facing label, never a routing key.
+ */
+display_name?: string | null, repository_id: string, creation_selector?: string | null, creation_ref?: string | null, creation_tree?: string | null, current_selector?: string | null, current_ref?: string | null, current_tree?: string | null, observed_at_epoch_seconds?: number | null, materializer_kind: WorkingDirectoryMaterializerKind, cleanup_target?: RuntimeWorkingDirectoryCleanupTarget | null, status: WorkingDirectoryStatusKind, cleanliness?: string | null, occupied_by?: WorkingDirectoryOccupancy | null, };
 
 export type WorkingDirectoryOccupancy = { runtime_id: string, worker_id: string, display_name: string, linked_at: string, };
 
-export type WorkingDirectorySummary = { working_directory_id: string, repository_key: string, creation_selector?: string | null, creation_ref?: string | null, creation_tree?: string | null, current_selector?: string | null, current_ref?: string | null, current_tree?: string | null, observed_at_epoch_seconds?: number | null, materializer_kind: WorkingDirectoryMaterializerKind, cleanup_target?: WorkingDirectoryCleanupTarget | null, status: WorkingDirectoryStatusKind, cleanliness?: string | null, primary_worker_id?: string | null, occupied_by?: WorkingDirectoryOccupancy | null, };
+export type WorkingDirectorySummary = { working_directory_id: string,
+/**
+ * Optional human-facing label, never a routing key.
+ */
+display_name?: string | null, repository_key: string, creation_selector?: string | null, creation_ref?: string | null, creation_tree?: string | null, current_selector?: string | null, current_ref?: string | null, current_tree?: string | null, observed_at_epoch_seconds?: number | null, materializer_kind: WorkingDirectoryMaterializerKind, cleanup_target?: WorkingDirectoryCleanupTarget | null, status: WorkingDirectoryStatusKind, cleanliness?: string | null, occupied_by?: WorkingDirectoryOccupancy | null, };
 
 export type WorkerWorkspaceSummary = { visibility: string, identity: string, workspace_id?: string | null, };
 
@@ -27,7 +35,9 @@ export type WorkerImplementationSummary = { kind: string, display_hint: string,
 
 export type WorkerCapabilitySummary = { can_stop: boolean, can_spawn_followup: boolean, };
 
-export type WorkerLaunchWorkerSummary = { runtime_id: string, worker_id: string, host_id: string, display_name: string, label: string, profile: string | null, singleton_key: string | null, tags: Array<string>, workspace: WorkerWorkspaceSummary, state: string, last_seen_at: string | null, pinned: boolean, retention_state: string, implementation: WorkerImplementationSummary, capabilities: WorkerCapabilitySummary, working_directory?: RuntimeWorkingDirectorySummary | null, diagnostics: Array<Diagnostic>, };
+export type RuntimeWorkerWorkdirAttachmentSummary = { alias: string, working_directory: RuntimeWorkingDirectorySummary, };
+
+export type WorkerLaunchWorkerSummary = { runtime_id: string, worker_id: string, host_id: string, display_name: string, label: string, profile: string | null, singleton_key: string | null, tags: Array<string>, workspace: WorkerWorkspaceSummary, state: string, last_seen_at: string | null, pinned: boolean, retention_state: string, implementation: WorkerImplementationSummary, capabilities: WorkerCapabilitySummary, workdir_attachments?: Array<RuntimeWorkerWorkdirAttachmentSummary>, diagnostics: Array<Diagnostic>, };
 
 export type WorkerLaunchRuntimeOption = { runtime_id: string, display_name: string, built_in: boolean, worker_creation_available: boolean, working_directory_required: boolean, status: string, diagnostics: Array<Diagnostic>, };
 
@@ -37,11 +47,15 @@ export type WorkingDirectoryRepositoryOption = { repository_key: string, default
 
 export type WorkerLaunchOptionsResponse = { workspace_id: string, runtimes: Array<WorkerLaunchRuntimeOption>, default_profile: string | null, profiles: Array<WorkerLaunchProfileCandidate>, repositories: Array<WorkingDirectoryRepositoryOption>, working_directories: Array<WorkingDirectorySummary>, diagnostics: Array<Diagnostic>, };
 
-export type BrowserWorkerWorkingDirectorySelection = { working_directory_id: string, relative_cwd: string | null, };
+export type BrowserWorkerWorkingDirectorySelection = {
+/**
+ * Stable Worker-local routing alias.
+ */
+alias: string, working_directory_id: string, relative_cwd: string | null, };
 
 export type CreateWorkspaceWorkerTicketAssignmentRequest = { ticket_id: string, operation_id: string, };
 
-export type CreateWorkspaceWorkerRequest = { runtime_id: string, display_name: string, profile: string | null, ticket_assignment: CreateWorkspaceWorkerTicketAssignmentRequest | null, initial_submit: Array<Segment>, working_directory: BrowserWorkerWorkingDirectorySelection | null,
+export type CreateWorkspaceWorkerRequest = { runtime_id: string, display_name: string, profile: string | null, ticket_assignment: CreateWorkspaceWorkerTicketAssignmentRequest | null, initial_submit: Array<Segment>, workdir_attachments: Array<BrowserWorkerWorkingDirectorySelection>,
 /**
  * Backend idempotency key used only for authenticated Worker-owned spawn/control.
  */

web/workspace/src/lib/workspace/api/workdirs.ts

@@ -11,6 +11,7 @@ import type {
 
 const SUMMARY_KEYS = new Set([
   "working_directory_id",
+  "display_name",
   "repository_key",
   "creation_selector",
   "creation_ref",
@@ -23,11 +24,11 @@ const SUMMARY_KEYS = new Set([
   "cleanup_target",
   "status",
   "cleanliness",
-  "primary_worker_id",
   "occupied_by",
 ]);
 const CREATE_REQUEST_KEYS = new Set([
   "runtime_id",
+  "display_name",
   "repository_key",
   "selector",
   "operation_id",
@@ -84,6 +85,7 @@ export function validateWorkingDirectoryCreateRequest(
     repository_key: stringField(record, "repository_key"),
   };
   assignOptionalString(request, record, "runtime_id");
+  assignOptionalString(request, record, "display_name");
   assignOptionalString(request, record, "selector");
   assignOptionalString(request, record, "operation_id");
   return request;
@@ -124,6 +126,7 @@ export function parseWorkingDirectorySummary(
       "unknown",
     ]),
   };
+  assignOptionalString(summary, record, "display_name");
   assignOptionalString(summary, record, "creation_selector");
   assignOptionalString(summary, record, "creation_ref");
   assignOptionalString(summary, record, "creation_tree");
@@ -131,7 +134,6 @@ export function parseWorkingDirectorySummary(
   assignOptionalString(summary, record, "current_ref");
   assignOptionalString(summary, record, "current_tree");
   assignOptionalString(summary, record, "cleanliness");
-  assignOptionalString(summary, record, "primary_worker_id");
   if (record.observed_at_epoch_seconds !== undefined) {
     const observedAt = record.observed_at_epoch_seconds;
     if (observedAt === null) {

web/workspace/src/lib/workspace/api/workers.test.ts

@@ -139,10 +139,11 @@ Deno.test("Worker create request parser requires the complete shared request", (
       { kind: "text", content: "Implement T-565." },
       { kind: "flow", selector: "builtin:coder-review" },
     ],
-    working_directory: {
+    workdir_attachments: [{
+      alias: "source",
       working_directory_id: "workdir-a",
       relative_cwd: null,
-    },
+    }],
     control_operation_id: null,
   };
 

web/workspace/src/lib/workspace/api/workers.ts

@@ -8,6 +8,7 @@ import type {
   DiagnosticSeverity,
   RuntimeWorkingDirectoryCleanupTarget,
   RuntimeWorkingDirectorySummary,
+  RuntimeWorkerWorkdirAttachmentSummary,
   WorkerCapabilitySummary,
   WorkerImplementationSummary,
   WorkerLaunchOptionsResponse,
@@ -261,6 +262,7 @@ function runtimeWorkingDirectory(
     item,
     [
       "working_directory_id",
+      "display_name",
       "repository_id",
       "creation_selector",
       "creation_ref",
@@ -273,7 +275,6 @@ function runtimeWorkingDirectory(
       "cleanup_target",
       "status",
       "cleanliness",
-      "primary_worker_id",
       "occupied_by",
     ],
     label,
@@ -318,6 +319,11 @@ function runtimeWorkingDirectory(
       item.working_directory_id,
       `${label}.working_directory_id`,
     ),
+    display_name: optional(
+      item.display_name,
+      `${label}.display_name`,
+      string,
+    ),
     repository_id: string(item.repository_id, `${label}.repository_id`),
     creation_selector: optional(
       item.creation_selector,
@@ -350,15 +356,25 @@ function runtimeWorkingDirectory(
     ),
     status: status as RuntimeWorkingDirectorySummary["status"],
     cleanliness: optional(item.cleanliness, `${label}.cleanliness`, string),
-    primary_worker_id: optional(
-      item.primary_worker_id,
-      `${label}.primary_worker_id`,
-      string,
-    ),
     occupied_by: occupied,
   };
 }
 
+function runtimeWorkdirAttachment(
+  value: unknown,
+  label: string,
+): RuntimeWorkerWorkdirAttachmentSummary {
+  const item = record(value, label);
+  exact(item, ["alias", "working_directory"], label);
+  return {
+    alias: string(item.alias, `${label}.alias`),
+    working_directory: runtimeWorkingDirectory(
+      item.working_directory,
+      `${label}.working_directory`,
+    ),
+  };
+}
+
 function workerSummary(
   value: unknown,
   label: string,
@@ -382,7 +398,7 @@ function workerSummary(
       "retention_state",
       "implementation",
       "capabilities",
-      "working_directory",
+      "workdir_attachments",
       "diagnostics",
     ],
     label,
@@ -406,11 +422,13 @@ function workerSummary(
       `${label}.implementation`,
     ),
     capabilities: capabilitySummary(item.capabilities, `${label}.capabilities`),
-    working_directory: optional(
-      item.working_directory,
-      `${label}.working_directory`,
-      runtimeWorkingDirectory,
-    ),
+    workdir_attachments: item.workdir_attachments === undefined
+      ? undefined
+      : array(
+        item.workdir_attachments,
+        `${label}.workdir_attachments`,
+        runtimeWorkdirAttachment,
+      ),
     diagnostics: array(item.diagnostics, `${label}.diagnostics`, diagnostic),
   };
 }
@@ -464,8 +482,9 @@ function workingDirectorySelection(
   label: string,
 ): BrowserWorkerWorkingDirectorySelection {
   const item = record(value, label);
-  exact(item, ["working_directory_id", "relative_cwd"], label);
+  exact(item, ["alias", "working_directory_id", "relative_cwd"], label);
   return {
+    alias: string(item.alias, `${label}.alias`),
     working_directory_id: string(
       item.working_directory_id,
       `${label}.working_directory_id`,
@@ -638,7 +657,7 @@ export function parseCreateWorkspaceWorkerRequest(
       "profile",
       "ticket_assignment",
       "initial_submit",
-      "working_directory",
+      "workdir_attachments",
       "control_operation_id",
     ],
     "Worker create request",
@@ -651,9 +670,11 @@ export function parseCreateWorkspaceWorkerRequest(
       ? null
       : ticketAssignment(item.ticket_assignment, "ticket_assignment"),
     initial_submit: array(item.initial_submit, "initial_submit", segment),
-    working_directory: item.working_directory === null
-      ? null
-      : workingDirectorySelection(item.working_directory, "working_directory"),
+    workdir_attachments: array(
+      item.workdir_attachments,
+      "workdir_attachments",
+      workingDirectorySelection,
+    ),
     control_operation_id: nullableString(
       item.control_operation_id,
       "control_operation_id",

web/workspace/src/lib/workspace/console/worker-console.ui.test.ts

@@ -256,8 +256,10 @@ Deno.test("workspace Worker list lives on the dedicated Workers page", async ()
       workersNav.includes("worker.display_name || worker.label") &&
       workersNav.includes("worker-status-dot") &&
       workersNav.includes("worker-status-spinner") &&
-      workersNav.includes("worker.repository_key ?? '—'") &&
-      workersNav.includes("worker.working_directory_id ?? '—'") &&
+      workersNav.includes("workdirMeta(worker)") &&
+      workersNav.includes("attachment.alias") &&
+      workersNav.includes("attachment.repository_key ?? '—'") &&
+      workersNav.includes("attachment.working_directory_id") &&
       !workersNav.includes('aria-disabled="true"'),
     "Workers sidebar should link to the Worker list page and show state indicators with repository/workdir metadata",
   );

web/workspace/src/lib/workspace/sidebar/WorkersNavSection.svelte

@@ -37,6 +37,14 @@
     Math.max(0, workers.length - COLLAPSED_WORKER_COUNT),
   );
 
+  function workdirMeta(worker: SidebarWorker): string {
+    const attachments = worker.workdir_attachments;
+    if (attachments.length === 0) return '—';
+    return attachments
+      .map((attachment) => `${attachment.alias}: ${attachment.repository_key ?? '—'}・${attachment.working_directory_id}`)
+      .join(', ');
+  }
+
   function workerKey(worker: SidebarWorker): string {
     return `${worker.runtime_id}:${worker.worker_id}`;
   }
@@ -190,7 +198,7 @@
             </span>
             <span class="worker-nav-label">{label}</span>
             <small class="worker-nav-meta">
-              {worker.repository_key ?? '—'}・{worker.working_directory_id ?? '—'}
+              {workdirMeta(worker)}
             </small>
           </a>
           <button

web/workspace/src/lib/workspace/sidebar/types.ts

@@ -89,6 +89,11 @@ export type WorkerCapabilities = {
   can_spawn_followup: boolean;
 };
 
+export type WorkerWorkdirAttachment = {
+  alias: string;
+  working_directory: WorkingDirectorySummary;
+};
+
 export type Worker = {
   runtime_id: string;
   worker_id: string;
@@ -107,7 +112,7 @@ export type Worker = {
   last_seen_at?: string | null;
   implementation: { kind: string; display_hint: string };
   capabilities: WorkerCapabilities;
-  working_directory?: WorkingDirectorySummary | null;
+  workdir_attachments?: WorkerWorkdirAttachment[];
   diagnostics: Diagnostic[];
 };
 

web/workspace/src/lib/workspace/sidebar/worker-actions.ts

@@ -7,13 +7,14 @@ import type {
 } from "./types";
 
 type FetchFn = typeof fetch;
+type WorkerActionTarget = Pick<Worker, "runtime_id" | "worker_id" | "state">;
 
 type WorkerLifecycleResponse = {
   state: string;
   diagnostics?: Diagnostic[];
 };
 
-function workerPath(workspaceId: string, worker: Worker): string {
+function workerPath(workspaceId: string, worker: WorkerActionTarget): string {
   return workspaceApiPath(
     workspaceId,
     `/runtimes/${encodeURIComponent(worker.runtime_id)}/workers/${
@@ -45,13 +46,13 @@ function diagnosticMessage(
     fallback;
 }
 
-export function canDeleteSidebarWorker(worker: Worker): boolean {
+export function canDeleteSidebarWorker(worker: WorkerActionTarget): boolean {
   return worker.state === "stopped";
 }
 
 export async function stopSidebarWorker(
   workspaceId: string,
-  worker: Worker,
+  worker: WorkerActionTarget,
   fetchFn: FetchFn = fetch,
 ): Promise<void> {
   const response = await fetchFn(`${workerPath(workspaceId, worker)}/stop`, {
@@ -71,7 +72,7 @@ export async function stopSidebarWorker(
 
 export async function deleteSidebarWorker(
   workspaceId: string,
-  worker: Worker,
+  worker: WorkerActionTarget,
   fetchFn: FetchFn = fetch,
 ): Promise<void> {
   const runtimePath = `/runtimes/${encodeURIComponent(worker.runtime_id)}`;

web/workspace/src/lib/workspace/sidebar/worker-launch.test.ts

@@ -1,6 +1,7 @@
 import {
   buildCreateWorkspaceWorkerRequest,
   defaultWorkerLaunchForm,
+  workerLaunchAttachmentError,
 } from "./worker-launch.ts";
 import type { WorkerLaunchOptionsResponse } from "./types.ts";
 
@@ -8,6 +9,262 @@ declare const Deno: {
   test(name: string, fn: () => Promise<void> | void): void;
 };
 
+Deno.test("defaultWorkerLaunchForm uses the Backend-published defaults and initial Workdir", () => {
+  const form = defaultWorkerLaunchForm(
+    options,
+    emptyForm({ initial_text: "hello" }),
+  );
+
+  assertEquals(form.runtime_id, "remote");
+  assertEquals(form.display_name, "Worker");
+  assertEquals(form.profile, "builtin:coder");
+  assertEquals(form.initial_text, "hello");
+  assertEquals(form.workdir_attachments, [{
+    alias: "workdir",
+    working_directory_id: "wd-1-repo",
+    relative_cwd: "",
+  }]);
+  assertEquals(form.working_directory_repository_key, "repo");
+  assertEquals(form.working_directory_selector, "HEAD");
+});
+
+Deno.test("defaultWorkerLaunchForm preserves an available Ticket role profile", () => {
+  const reviewerOptions = {
+    ...options,
+    profiles: [
+      ...options.profiles,
+      { id: "builtin:reviewer", label: "Reviewer", description: "review" },
+    ],
+  };
+  const form = defaultWorkerLaunchForm(
+    reviewerOptions,
+    emptyForm({
+      display_name: "Review worker",
+      profile: "builtin:reviewer",
+      initial_text: "Review the ticket.",
+      working_directory_repository_key: "repo",
+      working_directory_selector: "HEAD",
+    }),
+  );
+
+  assertEquals(form.profile, "builtin:reviewer");
+});
+
+Deno.test("defaultWorkerLaunchForm skips occupied Workdirs and leaves an editable attachment", () => {
+  const form = defaultWorkerLaunchForm(
+    {
+      ...options,
+      working_directories: [{
+        ...options.working_directories[0],
+        occupied_by: {
+          runtime_id: "embedded",
+          worker_id: "0198f82e-6d90-7f15-a121-174a02e10e77",
+          display_name: "Worker 12",
+          linked_at: "2026-07-24T00:00:00Z",
+        },
+      }],
+    },
+    emptyForm({ initial_text: "hello" }),
+  );
+
+  assertEquals(form.workdir_attachments, [{
+    alias: "workdir",
+    working_directory_id: "",
+    relative_cwd: "",
+  }]);
+});
+
+Deno.test("defaultWorkerLaunchForm preserves a Ticket repository target", () => {
+  const form = defaultWorkerLaunchForm(
+    {
+      ...options,
+      repositories: [
+        ...options.repositories,
+        { repository_key: "ticket-repo", default_selector: "main" },
+      ],
+      working_directories: [
+        options.working_directories[0],
+        {
+          ...options.working_directories[0],
+          working_directory_id: "ticket-workdir",
+          repository_key: "ticket-repo",
+          creation_selector: "work/ticket",
+        },
+      ],
+    },
+    emptyForm({
+      display_name: "Ticket worker",
+      profile: "builtin:coder",
+      initial_text: "Work on a ticket.",
+      working_directory_repository_key: "ticket-repo",
+      working_directory_selector: "work/ticket",
+    }),
+  );
+
+  assertEquals(form.workdir_attachments, [{
+    alias: "workdir",
+    working_directory_id: "ticket-workdir",
+    relative_cwd: "",
+  }]);
+  assertEquals(form.working_directory_repository_key, "ticket-repo");
+  assertEquals(form.working_directory_selector, "work/ticket");
+});
+
+Deno.test("defaultWorkerLaunchForm clears attachments for a Workdir-less Runtime", () => {
+  const form = defaultWorkerLaunchForm(
+    options,
+    emptyForm({
+      runtime_id: "embedded",
+      workdir_attachments: [{
+        alias: "checkout",
+        working_directory_id: "wd-1-repo",
+        relative_cwd: "src",
+      }],
+    }),
+  );
+
+  assertEquals(form.workdir_attachments, []);
+});
+
+Deno.test("buildCreateWorkspaceWorkerRequest emits multiple aliased attachments", () => {
+  const request = buildCreateWorkspaceWorkerRequest(emptyForm({
+    runtime_id: "remote",
+    display_name: "Worker",
+    profile: "builtin:coder",
+    initial_text: "go",
+    workdir_attachments: [
+      {
+        alias: " checkout ",
+        working_directory_id: "wd-1-repo",
+        relative_cwd: "crates/yoi",
+      },
+      {
+        alias: "docs",
+        working_directory_id: "wd-2-docs",
+        relative_cwd: "  ",
+      },
+    ],
+  }));
+
+  assertEquals(request, {
+    runtime_id: "remote",
+    display_name: "Worker",
+    profile: "builtin:coder",
+    ticket_assignment: null,
+    initial_submit: [{ kind: "text", content: "go" }],
+    workdir_attachments: [
+      {
+        alias: "checkout",
+        working_directory_id: "wd-1-repo",
+        relative_cwd: "crates/yoi",
+      },
+      {
+        alias: "docs",
+        working_directory_id: "wd-2-docs",
+        relative_cwd: null,
+      },
+    ],
+    control_operation_id: null,
+  });
+});
+
+Deno.test("buildCreateWorkspaceWorkerRequest validates attachment aliases and selections", () => {
+  assertEquals(
+    workerLaunchAttachmentError([attachment("invalid/alias", "wd-1-repo")]),
+    "Attachment 1 alias must be 1–64 ASCII letters, digits, dots, underscores, or hyphens, and start with a letter or digit.",
+  );
+  assertThrows(
+    () =>
+      buildCreateWorkspaceWorkerRequest(emptyForm({
+        workdir_attachments: [
+          attachment("checkout", "wd-1-repo"),
+          attachment("checkout", "wd-2-docs"),
+        ],
+      })),
+    "Attachment alias “checkout” is used more than once.",
+  );
+  assertThrows(
+    () =>
+      buildCreateWorkspaceWorkerRequest(emptyForm({
+        workdir_attachments: [
+          attachment("checkout", "wd-1-repo"),
+          attachment("docs", "wd-1-repo"),
+        ],
+      })),
+    "A Workdir cannot be attached more than once to one Worker.",
+  );
+  assertThrows(
+    () =>
+      buildCreateWorkspaceWorkerRequest(emptyForm({
+        workdir_attachments: [attachment("checkout", "")],
+      })),
+    "Attachment 1 must select a Workdir.",
+  );
+  assertThrows(
+    () =>
+      buildCreateWorkspaceWorkerRequest(emptyForm({
+        workdir_attachments: [{
+          ...attachment("checkout", "wd-1-repo"),
+          relative_cwd: "../outside",
+        }],
+      })),
+    "Attachment 1 relative cwd must stay inside the selected Workdir.",
+  );
+});
+
+Deno.test("buildCreateWorkspaceWorkerRequest sends no initial segments for an empty draft", () => {
+  const request = buildCreateWorkspaceWorkerRequest(emptyForm({
+    runtime_id: "embedded",
+    profile: "builtin:companion",
+    initial_text: "   ",
+  }));
+
+  assertEquals(request.initial_submit, []);
+});
+
+Deno.test("buildCreateWorkspaceWorkerRequest emits an empty attachment list for Workdir-less launches", () => {
+  const request = buildCreateWorkspaceWorkerRequest(emptyForm({
+    runtime_id: "embedded",
+    display_name: "Worker",
+    profile: "builtin:companion",
+    initial_text: "chat",
+  }));
+
+  assertEquals(request, {
+    runtime_id: "embedded",
+    display_name: "Worker",
+    profile: "builtin:companion",
+    ticket_assignment: null,
+    initial_submit: [{ kind: "text", content: "chat" }],
+    workdir_attachments: [],
+    control_operation_id: null,
+  });
+});
+
+function emptyForm(
+  overrides: Partial<Parameters<typeof buildCreateWorkspaceWorkerRequest>[0]> =
+    {},
+): Parameters<typeof buildCreateWorkspaceWorkerRequest>[0] {
+  return {
+    runtime_id: "",
+    display_name: "",
+    profile: "",
+    initial_text: "",
+    workdir_attachments: [],
+    working_directory_repository_key: "",
+    working_directory_selector: "",
+    ...overrides,
+  };
+}
+
+function attachment(alias: string, workingDirectoryId: string) {
+  return {
+    alias,
+    working_directory_id: workingDirectoryId,
+    relative_cwd: "",
+  };
+}
+
 function assertEquals<T>(actual: T, expected: T): void {
   const actualJson = JSON.stringify(actual);
   const expectedJson = JSON.stringify(expected);
@@ -16,6 +273,18 @@ function assertEquals<T>(actual: T, expected: T): void {
   }
 }
 
+function assertThrows(fn: () => unknown, expectedMessage: string): void {
+  try {
+    fn();
+  } catch (error) {
+    if (error instanceof Error && error.message === expectedMessage) return;
+    throw new Error(
+      `Expected error ${JSON.stringify(expectedMessage)}, got ${String(error)}`,
+    );
+  }
+  throw new Error(`Expected error ${JSON.stringify(expectedMessage)}`);
+}
+
 const options: WorkerLaunchOptionsResponse = {
   workspace_id: "workspace",
   runtimes: [
@@ -57,7 +326,6 @@ const options: WorkerLaunchOptionsResponse = {
       materializer_kind: "runtime_git_clone",
       status: "active",
       cleanliness: "clean",
-      primary_worker_id: null,
       cleanup_target: {
         kind: "runtime_git_clone",
         working_directory_id: "wd-1-repo",
@@ -67,179 +335,3 @@ const options: WorkerLaunchOptionsResponse = {
   ],
   diagnostics: [],
 };
-
-Deno.test("defaultWorkerLaunchForm uses the Backend-published Workspace default profile", () => {
-  const form = defaultWorkerLaunchForm(options, {
-    runtime_id: "",
-    display_name: "",
-    profile: "",
-    initial_text: "hello",
-    working_directory_id: "",
-    working_directory_repository_key: "",
-    working_directory_selector: "",
-    relative_cwd: "",
-  });
-
-  assertEquals(form.runtime_id, "remote");
-  assertEquals(form.display_name, "Worker");
-  assertEquals(form.profile, "builtin:coder");
-  assertEquals(form.initial_text, "hello");
-  assertEquals(form.working_directory_id, "wd-1-repo");
-  assertEquals(form.working_directory_repository_key, "repo");
-  assertEquals(form.working_directory_selector, "HEAD");
-});
-
-Deno.test("defaultWorkerLaunchForm preserves an available Ticket role profile", () => {
-  const reviewerOptions = {
-    ...options,
-    profiles: [
-      ...options.profiles,
-      { id: "builtin:reviewer", label: "Reviewer", description: "review" },
-    ],
-  };
-  const form = defaultWorkerLaunchForm(reviewerOptions, {
-    runtime_id: "",
-    display_name: "Review worker",
-    profile: "builtin:reviewer",
-    initial_text: "Review the ticket.",
-    working_directory_id: "",
-    working_directory_repository_key: "repo",
-    working_directory_selector: "HEAD",
-    relative_cwd: "",
-  });
-
-  assertEquals(form.profile, "builtin:reviewer");
-});
-
-Deno.test("defaultWorkerLaunchForm skips occupied working directories", () => {
-  const form = defaultWorkerLaunchForm(
-    {
-      ...options,
-      working_directories: [
-        {
-          ...options.working_directories[0],
-          occupied_by: {
-            runtime_id: "embedded",
-            worker_id: "0198f82e-6d90-7f15-a121-174a02e10e77",
-            display_name: "Worker 12",
-            linked_at: "2026-07-24T00:00:00Z",
-          },
-        },
-      ],
-    },
-    {
-      runtime_id: "",
-      display_name: "",
-      profile: "",
-      initial_text: "hello",
-      working_directory_id: "",
-      working_directory_repository_key: "",
-      working_directory_selector: "",
-      relative_cwd: "",
-    },
-  );
-
-  assertEquals(form.working_directory_id, "");
-});
-
-Deno.test("defaultWorkerLaunchForm preserves a Ticket repository target", () => {
-  const form = defaultWorkerLaunchForm(
-    {
-      ...options,
-      repositories: [
-        ...options.repositories,
-        {
-          repository_key: "ticket-repo",
-          default_selector: "main",
-        },
-      ],
-      working_directories: [
-        options.working_directories[0],
-        {
-          ...options.working_directories[0],
-          working_directory_id: "ticket-workdir",
-          repository_key: "ticket-repo",
-          creation_selector: "work/ticket",
-        },
-      ],
-    },
-    {
-      runtime_id: "",
-      display_name: "Ticket worker",
-      profile: "builtin:coder",
-      initial_text: "Work on a ticket.",
-      working_directory_id: "",
-      working_directory_repository_key: "ticket-repo",
-      working_directory_selector: "work/ticket",
-      relative_cwd: "",
-    },
-  );
-
-  assertEquals(form.working_directory_id, "ticket-workdir");
-  assertEquals(form.working_directory_repository_key, "ticket-repo");
-  assertEquals(form.working_directory_selector, "work/ticket");
-});
-
-Deno.test("buildCreateWorkspaceWorkerRequest sends working_directory id and relative cwd only", () => {
-  const request = buildCreateWorkspaceWorkerRequest({
-    runtime_id: "embedded",
-    display_name: "Worker",
-    profile: "builtin:coder",
-    initial_text: "go",
-    working_directory_id: "wd-1-repo",
-    working_directory_repository_key: "repo",
-    working_directory_selector: "main",
-    relative_cwd: "crates/yoi",
-  });
-
-  assertEquals(request, {
-    runtime_id: "embedded",
-    display_name: "Worker",
-    profile: "builtin:coder",
-    ticket_assignment: null,
-    initial_submit: [{ kind: "text", content: "go" }],
-    working_directory: {
-      working_directory_id: "wd-1-repo",
-      relative_cwd: "crates/yoi",
-    },
-    control_operation_id: null,
-  });
-});
-
-Deno.test("buildCreateWorkspaceWorkerRequest sends no initial segments for an empty draft", () => {
-  const request = buildCreateWorkspaceWorkerRequest({
-    runtime_id: "embedded",
-    display_name: "Worker",
-    profile: "builtin:companion",
-    initial_text: "   ",
-    working_directory_id: "",
-    working_directory_repository_key: "",
-    working_directory_selector: "",
-    relative_cwd: "",
-  });
-
-  assertEquals(request.initial_submit, []);
-});
-
-Deno.test("buildCreateWorkspaceWorkerRequest emits null for embedded no-workdir launches", () => {
-  const request = buildCreateWorkspaceWorkerRequest({
-    runtime_id: "embedded",
-    display_name: "Worker",
-    profile: "builtin:companion",
-    initial_text: "chat",
-    working_directory_id: "",
-    working_directory_repository_key: "",
-    working_directory_selector: "",
-    relative_cwd: "",
-  });
-
-  assertEquals(request, {
-    runtime_id: "embedded",
-    display_name: "Worker",
-    profile: "builtin:companion",
-    ticket_assignment: null,
-    initial_submit: [{ kind: "text", content: "chat" }],
-    working_directory: null,
-    control_operation_id: null,
-  });
-});

web/workspace/src/lib/workspace/sidebar/worker-launch.ts

@@ -1,19 +1,29 @@
-import type { CreateWorkspaceWorkerRequest } from "$lib/generated/worker-launch-api";
+import type {
+  BrowserWorkerWorkingDirectorySelection,
+  CreateWorkspaceWorkerRequest,
+} from "$lib/generated/worker-launch-api";
 import { parseCreateWorkspaceWorkerRequest } from "$lib/workspace/api/workers";
 
 import type { WorkerLaunchOptionsResponse } from "./types";
 
+export type WorkerLaunchAttachmentFormState = {
+  alias: string;
+  working_directory_id: string;
+  relative_cwd: string;
+};
+
 export type WorkerLaunchFormState = {
   runtime_id: string;
   display_name: string;
   profile: string;
   initial_text: string;
-  working_directory_id: string;
+  workdir_attachments: WorkerLaunchAttachmentFormState[];
   working_directory_repository_key: string;
   working_directory_selector: string;
-  relative_cwd: string;
 };
 
+const WORKDIR_ALIAS_PATTERN = /^[A-Za-z0-9][A-Za-z0-9._-]{0,63}$/;
+
 export function defaultWorkerLaunchForm(
   options: WorkerLaunchOptionsResponse | null,
   current: WorkerLaunchFormState,
@@ -31,7 +41,6 @@ export function defaultWorkerLaunchForm(
     options?.working_directories.filter((directory) =>
       directory.status === "active" &&
       directory.cleanliness === "clean" &&
-      directory.primary_worker_id == null &&
       directory.occupied_by == null
     ) ?? [];
   const selectedRuntime = current.runtime_id
@@ -60,6 +69,27 @@ export function defaultWorkerLaunchForm(
       repository.repository_key === current.working_directory_repository_key
     ) ??
       options?.repositories[0];
+  const availableWorkdirIds = new Set(
+    availableWorkingDirectories.map((directory) =>
+      directory.working_directory_id
+    ),
+  );
+  const currentAttachments = workdirlessRuntime
+    ? []
+    : current.workdir_attachments.filter((attachment) =>
+      availableWorkdirIds.has(attachment.working_directory_id)
+    );
+  const workdirAttachments = currentAttachments.length > 0
+    ? currentAttachments
+    : preferredWorkingDirectory
+    ? [{
+      alias: "workdir",
+      working_directory_id: preferredWorkingDirectory.working_directory_id,
+      relative_cwd: "",
+    }]
+    : selectedRuntime?.working_directory_required === true
+    ? [{ alias: "workdir", working_directory_id: "", relative_cwd: "" }]
+    : [];
 
   return {
     runtime_id: current.runtime_id || preferredRuntime?.runtime_id || "",
@@ -69,22 +99,68 @@ export function defaultWorkerLaunchForm(
         ? current.profile
         : preferredProfile?.id || "",
     initial_text: current.initial_text,
-    working_directory_id:
-      !workdirlessRuntime && availableWorkingDirectories.some(
-          (directory) =>
-            directory.working_directory_id === current.working_directory_id,
-        )
-        ? current.working_directory_id
-        : preferredWorkingDirectory?.working_directory_id || "",
+    workdir_attachments: workdirAttachments,
     working_directory_repository_key:
       current.working_directory_repository_key ||
       preferredRepository?.repository_key || "",
     working_directory_selector: current.working_directory_selector ||
       preferredRepository?.default_selector || "HEAD",
-    relative_cwd: current.relative_cwd,
   };
 }
 
+export function workerLaunchAttachmentError(
+  attachments: WorkerLaunchAttachmentFormState[],
+): string | null {
+  const aliases = new Set<string>();
+  const workdirIds = new Set<string>();
+
+  for (const [index, attachment] of attachments.entries()) {
+    const position = index + 1;
+    const alias = attachment.alias.trim();
+    const workdirId = attachment.working_directory_id.trim();
+    const relativeCwd = attachment.relative_cwd.trim();
+
+    if (!WORKDIR_ALIAS_PATTERN.test(alias)) {
+      return `Attachment ${position} alias must be 1–64 ASCII letters, digits, dots, underscores, or hyphens, and start with a letter or digit.`;
+    }
+    if (aliases.has(alias)) {
+      return `Attachment alias “${alias}” is used more than once.`;
+    }
+    aliases.add(alias);
+
+    if (!workdirId) {
+      return `Attachment ${position} must select a Workdir.`;
+    }
+    if (workdirIds.has(workdirId)) {
+      return "A Workdir cannot be attached more than once to one Worker.";
+    }
+    workdirIds.add(workdirId);
+
+    if (
+      relativeCwd.startsWith("/") ||
+      relativeCwd.split("/").some((component) => component === "..")
+    ) {
+      return `Attachment ${position} relative cwd must stay inside the selected Workdir.`;
+    }
+  }
+
+  return null;
+}
+
+function validatedAttachments(
+  attachments: WorkerLaunchAttachmentFormState[],
+): BrowserWorkerWorkingDirectorySelection[] {
+  const error = workerLaunchAttachmentError(attachments);
+  if (error) {
+    throw new Error(error);
+  }
+  return attachments.map((attachment) => ({
+    alias: attachment.alias.trim(),
+    working_directory_id: attachment.working_directory_id.trim(),
+    relative_cwd: attachment.relative_cwd.trim() || null,
+  }));
+}
+
 export function buildCreateWorkspaceWorkerRequest(
   form: WorkerLaunchFormState,
 ): CreateWorkspaceWorkerRequest {
@@ -97,12 +173,7 @@ export function buildCreateWorkspaceWorkerRequest(
     initial_submit: initialMessage
       ? [{ kind: "text", content: form.initial_text }]
       : [],
-    working_directory: form.working_directory_id
-      ? {
-        working_directory_id: form.working_directory_id,
-        relative_cwd: form.relative_cwd.trim() || null,
-      }
-      : null,
+    workdir_attachments: validatedAttachments(form.workdir_attachments),
     control_operation_id: null,
   });
 }

web/workspace/src/lib/workspace/sidebar/worker-subscription.test.ts

@@ -32,7 +32,7 @@ function worker(
     workspace_id: 'workspace-test',
     display_name: null,
     profile: null,
-    working_directory_id: null,
+    workdir_attachments: [],
   };
 }
 

web/workspace/src/lib/workspace/sidebar/worker-subscription.ts

@@ -1,5 +1,8 @@
 import { readable, type Readable } from 'svelte/store';
-import type { SubscriptionWorker } from '$lib/generated/protocol';
+import type {
+  SubscriptionWorker,
+  SubscriptionWorkerWorkdirAttachment,
+} from '$lib/generated/protocol';
 import { workspaceMultiplexer } from '$lib/workspace/multiplexer';
 import {
   applyWorkspaceWorkersFrame,
@@ -9,9 +12,8 @@ import { liveWorkerState } from './worker-state';
 import { compareWorkersForSidebar } from './workers';
 import type { Worker } from './types';
 
-export type SidebarWorker = Worker & {
-  repository_key: string | null;
-  working_directory_id: string | null;
+export type SidebarWorker = Omit<Worker, 'workdir_attachments'> & {
+  workdir_attachments: SubscriptionWorkerWorkdirAttachment[];
   has_running_internal_workers: boolean;
 };
 
@@ -103,10 +105,8 @@ function projectWorker(worker: SubscriptionWorker): SidebarWorker {
       can_stop: worker.availability !== 'unavailable' && worker.state !== 'stopped',
       can_spawn_followup: false,
     },
-    repository_key: worker.repository_key ?? null,
-    working_directory_id: worker.working_directory_id ?? null,
+    workdir_attachments: worker.workdir_attachments ?? [],
     has_running_internal_workers: worker.has_running_internal_workers,
-    working_directory: null,
     diagnostics: [],
   };
 }

web/workspace/src/lib/workspace/sidebar/workers.test.ts

@@ -40,7 +40,7 @@ function worker(overrides: Partial<Worker>): Worker {
       can_stop: true,
       can_spawn_followup: false,
     },
-    working_directory: null,
+    workdir_attachments: [],
     diagnostics: [],
     ...overrides,
   };

web/workspace/src/lib/workspace/sidebar/workers.ts

@@ -19,11 +19,15 @@ export function sidebarWorkerActivity(
   return 'none';
 }
 
-export function canShowWorkerInSidebar(worker: Worker): boolean {
+export function canShowWorkerInSidebar(
+  worker: Pick<Worker, 'implementation'>,
+): boolean {
   return worker.implementation.kind !== 'backend_worker_registry';
 }
 
-export function canOpenWorkerConsole(worker: Worker): boolean {
+export function canOpenWorkerConsole(
+  worker: Pick<Worker, 'implementation'>,
+): boolean {
   return canShowWorkerInSidebar(worker);
 }
 

web/workspace/src/lib/workspace/styles/workers.css

@@ -143,19 +143,41 @@
     min-width: 0;
     max-width: 100%;
   }
-  .worker-inline-select.wd-select {
-    min-width: 20rem;
+  .worker-attachment-heading {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    gap: var(--space-3);
+  }
+  .worker-attachment-heading h3,
+  .new-working-directory-panel h3 {
+    margin: 0;
+    color: var(--text-strong);
+    font-size: var(--font-size-body);
+  }
+  .worker-attachment-list {
+    display: grid;
+  }
+  .worker-attachment-row {
+    display: grid;
+    grid-template-columns:
+      minmax(7rem, 0.7fr) minmax(13rem, 1.5fr) minmax(10rem, 1fr) auto;
+    align-items: end;
+    gap: var(--space-2);
+    border-top: 1px solid var(--line);
+    padding: var(--space-3) 0;
+  }
+  .worker-attachment-row:last-child {
+    border-bottom: 1px solid var(--line);
+  }
+  .worker-attachment-remove {
+    margin-bottom: 1px;
   }
   .new-working-directory-panel {
     display: grid;
     gap: var(--space-3);
     padding-left: var(--space-3);
   }
-  .new-working-directory-panel h3 {
-    margin: 0;
-    color: var(--text-strong);
-    font-size: var(--font-size-body);
-  }
   .new-working-directory-fields,
   .worker-detail-grid {
     display: grid;
@@ -182,15 +204,19 @@
       flex-direction: column;
       white-space: normal;
     }
-    .worker-inline-select,
-    .worker-inline-select.wd-select {
+    .worker-inline-select {
       width: 100%;
       min-width: 0;
     }
     .new-working-directory-fields,
-    .worker-detail-grid {
+    .worker-detail-grid,
+    .worker-attachment-row {
       grid-template-columns: 1fr;
     }
+    .worker-attachment-remove {
+      justify-self: start;
+      margin-bottom: 0;
+    }
   }
   .worker-submit-error {
     display: grid;

web/workspace/src/routes/w/[workspaceId]/settings/runtimes/[runtimeId]/workdirs/+page.svelte

@@ -138,7 +138,10 @@
           {#each workdirs as workdir}
             {@const cleanup = cleanupCandidate(workdir)}
             <tr>
-              <td><code>{workdir.working_directory_id}</code></td>
+              <td>
+                <span>{workdir.display_name ?? '—'}</span>
+                <small><code>{workdir.working_directory_id}</code></small>
+              </td>
               <td>{workdir.repository_key}</td>
               <td><code>{currentRevision(workdir)}</code></td>
               <td>{workdir.status}</td>

web/workspace/src/routes/w/[workspaceId]/workers/+page.svelte

@@ -145,11 +145,14 @@
   }
 
   function workerDirectory(worker: Worker): string {
-    const directory = worker.working_directory;
-    if (!directory) return '—';
-    const provider = data.repositories?.items.find((repository) => repository.repository_key === directory.repository_key)
-      ?.provider;
-    return `${directory.repository_key} · ${formatCurrentWorkdirRevision(directory, provider)}`;
+    const attachments = worker.workdir_attachments ?? [];
+    if (attachments.length === 0) return '—';
+    return attachments.map(({ alias, working_directory: directory }) => {
+      const provider = data.repositories?.items.find((repository) => repository.repository_key === directory.repository_key)
+        ?.provider;
+      const label = directory.display_name ?? directory.repository_key;
+      return `${alias}: ${label} · ${formatCurrentWorkdirRevision(directory, provider)}`;
+    }).join(', ');
   }
 </script>
 

web/workspace/src/routes/w/[workspaceId]/workers/new/+page.svelte

@@ -11,7 +11,12 @@
     parseWorkerLaunchOptionsResponse,
   } from '$lib/workspace/api/workers';
   import { formatCurrentWorkdirRevision } from '$lib/workspace/settings/workdir-revision';
-  import { buildCreateWorkspaceWorkerRequest, defaultWorkerLaunchForm } from '$lib/workspace/sidebar/worker-launch';
+  import {
+    buildCreateWorkspaceWorkerRequest,
+    defaultWorkerLaunchForm,
+    workerLaunchAttachmentError,
+  } from '$lib/workspace/sidebar/worker-launch';
+  import type { WorkerLaunchAttachmentFormState } from '$lib/workspace/sidebar/worker-launch';
   import type {
     Diagnostic,
     WorkerLaunchOptionsResponse,
@@ -33,7 +38,8 @@
   function workdirOptionLabel(directory: WorkingDirectorySummary): string {
     const provider = data.repositories?.items.find((repository) => repository.repository_key === directory.repository_key)
       ?.provider;
-    return `${directory.repository_key} · ${formatCurrentWorkdirRevision(directory, provider)}`;
+    const label = directory.display_name ?? directory.repository_key;
+    return `${label} · ${formatCurrentWorkdirRevision(directory, provider)}`;
   }
 
   let { data }: PageProps = $props();
@@ -61,31 +67,37 @@
       : '',
   );
   let initialText = $state(ticketContext?.initialInput ?? '');
-  let workingDirectoryId = $state('');
+  let workdirAttachments = $state<WorkerLaunchAttachmentFormState[]>([]);
+  let workingDirectoryDisplayName = $state('');
   let workingDirectoryRepositoryKey = $state(ticketContext?.repositoryKey ?? '');
   let workingDirectorySelector = $state(ticketContext?.refSelector ?? 'HEAD');
-  let relativeCwd = $state('');
   let creatingWorkingDirectory = $state(false);
-  let isNewWorkingDirectorySelected = $derived(workingDirectoryId === NEW_WORKING_DIRECTORY_VALUE);
+  let newWorkingDirectoryAttachmentIndex = $derived(
+    workdirAttachments.findIndex((attachment) => attachment.working_directory_id === NEW_WORKING_DIRECTORY_VALUE),
+  );
+  let isNewWorkingDirectorySelected = $derived(newWorkingDirectoryAttachmentIndex >= 0);
   let selectedRuntime = $derived(options?.runtimes.find((runtime) => runtime.runtime_id === runtimeId));
   let selectedRuntimeAllowsNoWorkdir = $derived(selectedRuntime?.working_directory_required === false);
-  let hasSelectedExistingWorkdir = $derived(Boolean(
-    workingDirectoryId && !isNewWorkingDirectorySelected && !selectedRuntimeAllowsNoWorkdir,
-  ));
   let availableWorkingDirectories = $derived(
     selectedRuntimeAllowsNoWorkdir
       ? []
       : (options?.working_directories ?? []).filter((directory) =>
         directory.status === 'active' &&
         directory.cleanliness === 'clean' &&
-        directory.primary_worker_id == null &&
         directory.occupied_by == null
       ),
   );
+  let attachmentValidationError = $derived(
+    isNewWorkingDirectorySelected
+      ? 'Create the new Workdir before starting the Worker.'
+      : workerLaunchAttachmentError(workdirAttachments),
+  );
   let canStartWorker = $derived(Boolean(
     runtimeId &&
       profile &&
-      (hasSelectedExistingWorkdir || (selectedRuntimeAllowsNoWorkdir && !isNewWorkingDirectorySelected)),
+      (selectedRuntimeAllowsNoWorkdir
+        ? workdirAttachments.length === 0
+        : workdirAttachments.length > 0 && !attachmentValidationError),
   ));
 
   function workerApiPath(path: string): string {
@@ -104,12 +116,49 @@
   });
 
   $effect(() => {
-    if (selectedRuntimeAllowsNoWorkdir && workingDirectoryId) {
-      workingDirectoryId = '';
-      relativeCwd = '';
+    if (selectedRuntimeAllowsNoWorkdir && workdirAttachments.length > 0) {
+      workdirAttachments = [];
+    } else if (selectedRuntime?.working_directory_required === true && workdirAttachments.length === 0) {
+      workdirAttachments = [{
+        alias: 'workdir',
+        working_directory_id: availableWorkingDirectories[0]?.working_directory_id ?? '',
+        relative_cwd: '',
+      }];
     }
   });
 
+  function nextAttachmentAlias(): string {
+    const aliases = new Set(workdirAttachments.map((attachment) => attachment.alias.trim()));
+    if (!aliases.has('workdir')) return 'workdir';
+    let suffix = 2;
+    while (aliases.has(`workdir${suffix}`)) suffix += 1;
+    return `workdir${suffix}`;
+  }
+
+  function addAttachment(): void {
+    const selectedWorkdirs = new Set(
+      workdirAttachments.map((attachment) => attachment.working_directory_id),
+    );
+    const available = availableWorkingDirectories.find((directory) =>
+      !selectedWorkdirs.has(directory.working_directory_id)
+    );
+    workdirAttachments = [...workdirAttachments, {
+      alias: nextAttachmentAlias(),
+      working_directory_id: available?.working_directory_id ?? '',
+      relative_cwd: '',
+    }];
+  }
+
+  function removeAttachment(index: number): void {
+    workdirAttachments = workdirAttachments.filter((_, candidateIndex) => candidateIndex !== index);
+  }
+
+  function workdirSelectedByAnotherAttachment(workdirId: string, index: number): boolean {
+    return workdirAttachments.some((attachment, candidateIndex) =>
+      candidateIndex !== index && attachment.working_directory_id === workdirId
+    );
+  }
+
   async function loadLaunchOptions(signal?: AbortSignal) {
     loading = true;
     optionsError = null;
@@ -125,19 +174,30 @@
         display_name: displayName,
         profile,
         initial_text: initialText,
-        working_directory_id: workingDirectoryId,
+        workdir_attachments: workdirAttachments,
         working_directory_repository_key: workingDirectoryRepositoryKey,
         working_directory_selector: workingDirectorySelector,
-        relative_cwd: relativeCwd,
       });
       runtimeId = form.runtime_id;
       displayName = form.display_name;
       profile = form.profile;
-      workingDirectoryId = form.working_directory_id ||
-        (ticketContext?.repositoryKey ? NEW_WORKING_DIRECTORY_VALUE : '');
+      const runtimeRequiresWorkdir = payload.runtimes.find((runtime) =>
+        runtime.runtime_id === form.runtime_id
+      )?.working_directory_required !== false;
+      workdirAttachments = form.workdir_attachments;
+      if (
+        runtimeRequiresWorkdir &&
+        ticketContext?.repositoryKey &&
+        workdirAttachments.every((attachment) => !attachment.working_directory_id)
+      ) {
+        workdirAttachments = [{
+          alias: 'workdir',
+          working_directory_id: NEW_WORKING_DIRECTORY_VALUE,
+          relative_cwd: '',
+        }];
+      }
       workingDirectoryRepositoryKey = form.working_directory_repository_key;
       workingDirectorySelector = form.working_directory_selector;
-      relativeCwd = form.relative_cwd;
     } catch (err) {
       if (err instanceof DOMException && err.name === 'AbortError') {
         return;
@@ -151,6 +211,11 @@
   }
 
   async function createWorkingDirectory() {
+    const attachmentIndex = newWorkingDirectoryAttachmentIndex;
+    if (attachmentIndex < 0) {
+      submitError = { message: 'select New workdir on an attachment first', diagnostics: [] };
+      return;
+    }
     if (!runtimeId) {
       submitError = { message: 'select a runtime before creating a workdir', diagnostics: [] };
       return;
@@ -168,6 +233,7 @@
     try {
       const request = validateWorkingDirectoryCreateRequest({
         runtime_id: runtimeId,
+        ...(workingDirectoryDisplayName.trim() ? { display_name: workingDirectoryDisplayName.trim() } : {}),
         repository_key: workingDirectoryRepositoryKey,
         ...(workingDirectorySelector ? { selector: workingDirectorySelector } : {}),
       });
@@ -193,7 +259,11 @@
           ],
         }
         : options;
-      workingDirectoryId = payload.item.working_directory_id;
+      workdirAttachments = workdirAttachments.map((attachment, index) =>
+        index === attachmentIndex && attachment.working_directory_id === NEW_WORKING_DIRECTORY_VALUE
+          ? { ...attachment, working_directory_id: payload.item.working_directory_id }
+          : attachment
+      );
     } catch (err) {
       submitError = exceptionDisplayError(err, 'workdir create failed');
     } finally {
@@ -206,8 +276,16 @@
       submitError = { message: 'workspace id is unavailable', diagnostics: [] };
       return;
     }
-    if (isNewWorkingDirectorySelected || (!workingDirectoryId && !selectedRuntimeAllowsNoWorkdir)) {
-      submitError = { message: 'select or create a workdir before starting a Worker; only embedded Runtime can start without one', diagnostics: [] };
+    if (selectedRuntimeAllowsNoWorkdir && workdirAttachments.length > 0) {
+      submitError = { message: 'the selected Runtime must start without Workdir attachments', diagnostics: [] };
+      return;
+    }
+    if (!selectedRuntimeAllowsNoWorkdir && workdirAttachments.length === 0) {
+      submitError = { message: 'add at least one Workdir attachment before starting a Worker; only embedded Runtime can start without one', diagnostics: [] };
+      return;
+    }
+    if (attachmentValidationError) {
+      submitError = { message: attachmentValidationError, diagnostics: [] };
       return;
     }
 
@@ -222,10 +300,9 @@
           display_name: displayName,
           profile,
           initial_text: initialText,
-          working_directory_id: workingDirectoryId,
+          workdir_attachments: workdirAttachments,
           working_directory_repository_key: workingDirectoryRepositoryKey,
           working_directory_selector: workingDirectorySelector,
-          relative_cwd: relativeCwd,
         })),
       });
       if (!response.ok) {
@@ -302,21 +379,7 @@
         <h2 id="worker-location-heading">Location</h2>
 
         <div class="worker-launch-sentence">
-          <span>Run at</span>
-          <select class="worker-inline-select wd-select" bind:value={workingDirectoryId} aria-label="Workdir">
-            {#if selectedRuntimeAllowsNoWorkdir}
-              <option value="">No workdir</option>
-            {:else}
-              <option value="" disabled>Select workdir</option>
-              {#each availableWorkingDirectories as directory}
-                <option value={directory.working_directory_id}>
-                  {workdirOptionLabel(directory)}
-                </option>
-              {/each}
-              <option value={NEW_WORKING_DIRECTORY_VALUE}>New workdir…</option>
-            {/if}
-          </select>
-          <span>in</span>
+          <span>Run in</span>
           <select class="worker-inline-select runtime-select" bind:value={runtimeId} required aria-label="Runtime">
             {#if options?.runtimes.length}
               {#each options.runtimes as runtime}
@@ -330,16 +393,78 @@
           </select>
         </div>
 
-        {#if !selectedRuntimeAllowsNoWorkdir && !workingDirectoryId && !isNewWorkingDirectorySelected}
-          <p class="worker-workdir-note">This Runtime requires a selected workdir before starting a Worker.</p>
-        {:else if selectedRuntimeAllowsNoWorkdir && !workingDirectoryId}
-          <p class="worker-workdir-note">No filesystem tools or Bash will be available without a workdir.</p>
+        {#if selectedRuntimeAllowsNoWorkdir}
+          <p class="worker-workdir-note">No filesystem tools or Bash will be available without a Workdir.</p>
+        {:else}
+          <div class="worker-attachment-heading">
+            <h3>Initial Workdir attachments</h3>
+            <button type="button" class="secondary-button" onclick={addAttachment}>Add attachment</button>
+          </div>
+
+          <div class="worker-attachment-list">
+            {#each workdirAttachments as attachment, index}
+              <div class="worker-attachment-row">
+                <label>
+                  <span>Alias</span>
+                  <input
+                    bind:value={attachment.alias}
+                    autocomplete="off"
+                    maxlength="64"
+                    placeholder="workdir"
+                    aria-label={`Attachment ${index + 1} alias`}
+                  />
+                </label>
+                <label>
+                  <span>Workdir</span>
+                  <select bind:value={attachment.working_directory_id} aria-label={`Attachment ${index + 1} Workdir`}>
+                    <option value="" disabled>Select Workdir</option>
+                    {#each availableWorkingDirectories as directory}
+                      <option
+                        value={directory.working_directory_id}
+                        disabled={workdirSelectedByAnotherAttachment(directory.working_directory_id, index)}
+                      >
+                        {workdirOptionLabel(directory)}
+                      </option>
+                    {/each}
+                    <option
+                      value={NEW_WORKING_DIRECTORY_VALUE}
+                      disabled={isNewWorkingDirectorySelected && newWorkingDirectoryAttachmentIndex !== index}
+                    >New Workdir…</option>
+                  </select>
+                </label>
+                <label>
+                  <span>Relative cwd</span>
+                  <input
+                    bind:value={attachment.relative_cwd}
+                    autocomplete="off"
+                    placeholder="Optional path inside Workdir"
+                    aria-label={`Attachment ${index + 1} relative cwd`}
+                  />
+                </label>
+                <button
+                  type="button"
+                  class="worker-attachment-remove"
+                  onclick={() => removeAttachment(index)}
+                  disabled={creatingWorkingDirectory && newWorkingDirectoryAttachmentIndex === index}
+                  aria-label={`Remove attachment ${index + 1}`}
+                >Remove</button>
+              </div>
+            {/each}
+          </div>
+
+          {#if attachmentValidationError}
+            <p class="worker-workdir-note error">{attachmentValidationError}</p>
+          {/if}
         {/if}
 
         {#if isNewWorkingDirectorySelected}
           <div class="new-working-directory-panel">
-            <h3>New workdir</h3>
+            <h3>New Workdir for “{workdirAttachments[newWorkingDirectoryAttachmentIndex]?.alias || `attachment ${newWorkingDirectoryAttachmentIndex + 1}`}”</h3>
             <div class="new-working-directory-fields">
+              <label>
+                <span>Display name</span>
+                <input bind:value={workingDirectoryDisplayName} autocomplete="off" placeholder="Optional label" maxlength="80" />
+              </label>
               <label>
                 <span>Repository</span>
                 <select bind:value={workingDirectoryRepositoryKey}>
@@ -358,17 +483,10 @@
               </label>
             </div>
             <button type="button" disabled={creatingWorkingDirectory || !runtimeId || !workingDirectoryRepositoryKey} onclick={() => void createWorkingDirectory()}>
-              {creatingWorkingDirectory ? 'Creating…' : 'Create workdir'}
+              {creatingWorkingDirectory ? 'Creating…' : 'Create Workdir'}
             </button>
           </div>
         {/if}
-
-        {#if hasSelectedExistingWorkdir || isNewWorkingDirectorySelected}
-          <label class="relative-cwd-field">
-            <span>Relative cwd inside workdir</span>
-            <input bind:value={relativeCwd} autocomplete="off" placeholder="Optional path inside workdir" />
-          </label>
-        {/if}
       </section>
 
       <section class="worker-form-section" aria-labelledby="worker-details-heading">

web/workspace/tests/workdir-api.test.ts

@@ -10,6 +10,7 @@ import {
 
 const summary = {
   working_directory_id: "workdir-1",
+  display_name: "Checkout",
   repository_key: "main",
   materializer_kind: "runtime_git_clone",
   status: "active",
@@ -27,6 +28,9 @@ Deno.test("Workdir REST validation accepts the generated list and create contrac
     items: [summary],
     diagnostics: [],
   });
+  if (list.items[0]?.display_name !== "Checkout") {
+    throw new Error("display name was not preserved");
+  }
   if (list.items[0]?.occupied_by?.runtime_id !== "arcadia") {
     throw new Error("occupancy subject was not preserved");
   }
@@ -60,6 +64,7 @@ Deno.test("Workdir REST validation rejects stale response JSON", () => {
 Deno.test("Workdir REST validation enforces create operation fields", () => {
   const request = validateWorkingDirectoryCreateRequest({
     runtime_id: "arcadia",
+    display_name: "Review checkout",
     repository_key: "main",
     selector: "develop",
     operation_id: "operation-1",
@@ -67,6 +72,9 @@ Deno.test("Workdir REST validation enforces create operation fields", () => {
   if (request.operation_id !== "operation-1") {
     throw new Error("operation id was not preserved");
   }
+  if (request.display_name !== "Review checkout") {
+    throw new Error("display name was not preserved");
+  }
 
   for (
     const invalid of [