feat: route SubWorker workdir execution through parent

crates/tools/src/bash.rs

@@ -118,6 +118,7 @@ impl Tool for BashTool {
                 command: params.command,
                 timeout_secs,
                 output_limit: INLINE_BYTE_BUDGET,
+                cwd: None,
                 spill_dir: Some(self.output_dir.clone()),
                 tool_call_id: Some(call_id.clone()),
             })

crates/workdir/src/http.rs

@@ -68,12 +68,10 @@ pub enum WorkdirSessionOperation {
     CommandCancel(CommandHandle),
 }
 
-/// Wire envelope for an operation and its optional provider-enforced child scope.
+/// Wire envelope for one provider operation.
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct WorkdirSessionOperationRequest {
-    #[serde(default, skip_serializing_if = "Vec::is_empty")]
-    pub delegations: Vec<crate::WorkdirDelegationRequest>,
     pub operation: WorkdirSessionOperation,
 }
 
@@ -289,7 +287,7 @@ mod client {
     use reqwest::{Client, StatusCode, Url};
 
     use super::*;
-    use crate::{Workdir, WorkdirSession, WorkdirSessionHandle};
+    use crate::{Workdir, WorkdirSession};
 
     /// Provides a fresh bearer token for each Runtime request. Backend
     /// implementations can mint short-lived capability tokens without making a
@@ -324,7 +322,6 @@ mod client {
         workdir: Workdir,
         session_id: WorkdirSessionId,
         capabilities: WorkdirSessionCapabilities,
-        delegations: Vec<crate::WorkdirDelegationRequest>,
         closed: AtomicBool,
     }
 
@@ -377,7 +374,6 @@ mod client {
                 workdir: Workdir::new(opened.workdir_id.as_str()),
                 session_id: opened.session_id,
                 capabilities: opened.capabilities,
-                delegations: Vec::new(),
                 closed: AtomicBool::new(false),
             })
         }
@@ -404,10 +400,7 @@ mod client {
                     "operations",
                 ],
             )?;
-            let operation = WorkdirSessionOperationRequest {
-                delegations: self.delegations.clone(),
-                operation,
-            };
+            let operation = WorkdirSessionOperationRequest { operation };
             let response = self
                 .client
                 .post(url)
@@ -436,37 +429,6 @@ mod client {
             self.capabilities
         }
 
-        fn transports_delegation_context(&self) -> bool {
-            true
-        }
-
-        async fn capture_delegation_source(
-            &self,
-            request: &crate::WorkdirDelegationRequest,
-        ) -> Result<WorkdirSessionHandle, WorkdirError> {
-            if self.closed.load(Ordering::Acquire) {
-                return Err(WorkdirError::SessionClosed);
-            }
-            let mut delegations = self.delegations.clone();
-            delegations.push(request.clone());
-            let candidate = Arc::new(Self {
-                client: self.client.clone(),
-                base_url: self.base_url.clone(),
-                authorization: self.authorization.clone(),
-                workdir: self.workdir.clone(),
-                session_id: self.session_id.clone(),
-                capabilities: self.capabilities,
-                delegations,
-                closed: AtomicBool::new(false),
-            });
-            candidate
-                .stat(StatRequest {
-                    path: fs_operation::FsPath::new("").expect("empty Workdir path is valid"),
-                })
-                .await?;
-            Ok(candidate)
-        }
-
         async fn stat(&self, request: StatRequest) -> Result<StatResult, WorkdirError> {
             match self.operate(WorkdirSessionOperation::Stat(request)).await? {
                 WorkdirSessionOperationResult::Stat(result) => Ok(result),

crates/workdir/src/lib.rs

@@ -5,10 +5,10 @@
 //! bound to one Worker. Tools consume sessions; they do not own Workdir
 //! materialization or cleanup.
 
-mod delegation;
 pub mod http;
 mod local;
 mod operation;
+mod scope;
 pub mod workspace;
 
 use std::path::{Path, PathBuf};
@@ -18,11 +18,6 @@ use async_trait::async_trait;
 use serde::{Deserialize, Serialize};
 use tokio::sync::broadcast;
 
-pub use delegation::{
-    AppliedWorkdirDelegation, ReadOnlyWorkdirSession, WorkdirDelegation,
-    WorkdirDelegationPermission, WorkdirDelegationRequest, WorkdirDelegationRule,
-    apply_delegation_chain, delegation_capable_session,
-};
 pub use fs_operation::{
     ContentHash, EditRequest, EditResult, EntryKind, FsPath as WorkdirPath, GlobRequest,
     GlobResult, GrepOutputMode, GrepRequest, GrepResult, ListEntry, ListRequest, ListResult,
@@ -32,6 +27,10 @@ pub use local::{
     LocalWorkdirSession, SymlinkInfo, WorkdirSessionResource, direct_symlink, first_symlink,
 };
 pub use operation::*;
+pub use scope::{
+    ReadOnlyWorkdirSession, WorkdirScopeLease, WorkdirToolBroker, WorkdirToolScope,
+    WorkdirToolScopePermission, WorkdirToolScopeRule,
+};
 
 /// Persistent, opaque identity of one materialized Workdir.
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
@@ -148,39 +147,6 @@ pub trait WorkdirSession: std::fmt::Debug + Send + Sync {
     fn workdir(&self) -> &Workdir;
     fn capabilities(&self) -> WorkdirSessionCapabilities;
 
-    fn is_delegation_capable(&self) -> bool {
-        false
-    }
-
-    /// Whether this session transports the delegation chain to another
-    /// provider boundary that will apply logical cwd/path resolution there.
-    fn transports_delegation_context(&self) -> bool {
-        false
-    }
-
-    /// Capture a provider-specific source for a delegated child session.
-    /// Remote providers use this boundary to pin attachment identity without
-    /// exposing transport handles or host paths.
-    async fn capture_delegation_source(
-        &self,
-        _request: &WorkdirDelegationRequest,
-    ) -> Result<WorkdirSessionHandle, WorkdirError> {
-        Err(WorkdirError::Denied(
-            "workdir provider does not support delegated sessions".into(),
-        ))
-    }
-
-    /// Attenuate this session into a revocable child lease. Only sessions
-    /// created with [`delegation_capable_session`] implement this operation.
-    async fn delegate(
-        &self,
-        _request: WorkdirDelegationRequest,
-    ) -> Result<WorkdirDelegation, WorkdirError> {
-        Err(WorkdirError::Denied(
-            "workdir session is not delegation-capable".into(),
-        ))
-    }
-
     async fn stat(&self, request: StatRequest) -> Result<StatResult, WorkdirError>;
     async fn read(&self, request: ReadRequest) -> Result<ReadResult, WorkdirError>;
     async fn write(&self, request: WriteRequest) -> Result<WriteResult, WorkdirError>;

crates/workdir/src/local.rs

@@ -18,7 +18,7 @@ use std::sync::{Arc, Mutex as StdMutex};
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 use async_trait::async_trait;
-use manifest::{Permission, Scope, ScopeConfig, ScopeRule, SharedScope};
+use manifest::{Scope, SharedScope};
 use sha2::{Digest, Sha256};
 use tokio::process::Command;
 use tokio::sync::{Mutex, broadcast, watch};
@@ -28,10 +28,8 @@ use crate::{
     CommandEvent, CommandHandle, CommandOutput, CommandOutputRequest, CommandRequest,
     CommandSnapshot, CommandStatus, CommandStream, CommandStreamSlice, EditRequest, EditResult,
     GlobRequest, GlobResult, GrepRequest, GrepResult, ListRequest, ListResult, ReadRequest,
-    ReadResult, StatRequest, StatResult, Workdir, WorkdirDelegationPermission,
-    WorkdirDelegationRequest, WorkdirError, WorkdirPath, WorkdirSession,
-    WorkdirSessionCapabilities, WorkdirSessionCapability, WorkdirSessionHandle, WriteRequest,
-    WriteResult,
+    ReadResult, StatRequest, StatResult, Workdir, WorkdirError, WorkdirPath, WorkdirSession,
+    WorkdirSessionCapabilities, WorkdirSessionCapability, WriteRequest, WriteResult,
 };
 #[cfg(test)]
 use crate::{EntryKind, WriteOutcome};
@@ -558,69 +556,6 @@ impl WorkdirSession for LocalWorkdirSession {
         self.inner.capabilities
     }
 
-    async fn capture_delegation_source(
-        &self,
-        request: &WorkdirDelegationRequest,
-    ) -> Result<WorkdirSessionHandle, WorkdirError> {
-        let host_rules = request
-            .rules
-            .iter()
-            .map(|rule| ScopeRule {
-                target: self.inner.root.join(rule.target.as_str()),
-                permission: match rule.permission {
-                    WorkdirDelegationPermission::Read => Permission::Read,
-                    WorkdirDelegationPermission::Write => Permission::Write,
-                },
-                recursive: rule.recursive,
-            })
-            .collect::<Vec<_>>();
-        for (logical, host) in request.rules.iter().zip(&host_rules) {
-            if logical.permission == WorkdirDelegationPermission::Write {
-                let resolved = Scope::resolved_target(host)
-                    .map_err(|error| WorkdirError::Denied(error.to_string()))?;
-                if resolved != host.target {
-                    return Err(WorkdirError::Denied(format!(
-                        "write delegation target `{}` traverses a symlink",
-                        logical.target
-                    )));
-                }
-            }
-        }
-        let parent_scope = self.inner.scope.snapshot();
-        for rule in &host_rules {
-            if !parent_scope
-                .allows_rule(rule)
-                .map_err(|error| WorkdirError::Denied(error.to_string()))?
-            {
-                return Err(WorkdirError::Denied(format!(
-                    "delegated provider scope `{}` exceeds the parent session",
-                    rule.target.display()
-                )));
-            }
-        }
-        let child_scope = Scope::from_config(&ScopeConfig {
-            allow: host_rules,
-            deny: Vec::new(),
-        })
-        .map_err(|error| WorkdirError::Denied(error.to_string()))?;
-        let child_cwd = self.inner.root.join(request.cwd.as_str());
-        if !child_scope.is_readable(&child_cwd)
-            || !std::fs::metadata(&child_cwd).is_ok_and(|metadata| metadata.is_dir())
-        {
-            return Err(WorkdirError::Denied(format!(
-                "delegated cwd `{}` is not a readable Workdir directory",
-                request.cwd
-            )));
-        }
-        Ok(Arc::new(LocalWorkdirSession::materialized_bound(
-            self.inner.workdir.clone(),
-            self.inner.root.clone(),
-            self.inner.root.clone(),
-            SharedScope::new(child_scope),
-            self.inner.capabilities,
-        )))
-    }
-
     async fn stat(&self, request: StatRequest) -> Result<StatResult, WorkdirError> {
         self.ensure_capability(WorkdirSessionCapability::Read)?;
         let logical = request.path.clone();
@@ -694,9 +629,20 @@ impl WorkdirSession for LocalWorkdirSession {
         {
             return Err(WorkdirError::OutOfScope(spill_dir.to_path_buf()));
         }
+        let cwd = if let Some(logical_cwd) = request.cwd.as_ref() {
+            let cwd = self.resolve(logical_cwd);
+            let scope = self.inner.scope.snapshot();
+            if !scope.is_readable(&cwd)
+                || !std::fs::metadata(&cwd).is_ok_and(|metadata| metadata.is_dir())
+            {
+                return Err(WorkdirError::OutOfScope(cwd));
+            }
+            cwd
+        } else {
+            self.inner.cwd.clone()
+        };
         let id = self.inner.next_command_id.fetch_add(1, Ordering::Relaxed);
         let handle = CommandHandle(format!("command-{id}"));
-        let cwd = self.inner.cwd.clone();
         let (completion_tx, completion) = watch::channel(false);
         let command_id = handle.0.clone();
         let telemetry = self.inner.command_telemetry.clone();
@@ -1516,6 +1462,7 @@ mod tests {
                 command: "sleep 30".to_owned(),
                 timeout_secs: 60,
                 output_limit: 1024,
+                cwd: None,
                 spill_dir: None,
                 tool_call_id: None,
             },
@@ -2043,6 +1990,7 @@ mod tests {
                 command: "pwd && printf provider-command".into(),
                 timeout_secs: 5,
                 output_limit: 4096,
+                cwd: None,
                 spill_dir: None,
                 tool_call_id: None,
             },
@@ -2141,6 +2089,7 @@ mod tests {
                 command: "printf hidden".into(),
                 timeout_secs: 5,
                 output_limit: 1,
+                cwd: None,
                 spill_dir: Some(spill.path().to_path_buf()),
                 tool_call_id: None,
             },
@@ -2178,6 +2127,7 @@ mod tests {
                 command: "i=0; while [ $i -lt 200 ]; do printf 'line-%03d\\n' \"$i\"; i=$((i+1)); done; printf 'FINAL-NEEDLE\\n'".into(),
                 timeout_secs: 5,
                 output_limit: 64,
+                cwd: None,
                 spill_dir: Some(spill.path().to_path_buf()),
                 tool_call_id: None,
             },
@@ -2224,6 +2174,7 @@ mod tests {
                 command: "printf 'aéz'".into(),
                 timeout_secs: 5,
                 output_limit: 1024,
+                cwd: None,
                 spill_dir: None,
                 tool_call_id: None,
             },
@@ -2449,6 +2400,7 @@ mod tests {
                 command: "printf ready; printf warning >&2; sleep 0.2; printf done".into(),
                 timeout_secs: 5,
                 output_limit: 1024,
+                cwd: None,
                 spill_dir: None,
                 tool_call_id: Some("tool-7".into()),
             },
@@ -2553,6 +2505,7 @@ mod tests {
                 command: "sleep 30".into(),
                 timeout_secs: 1,
                 output_limit: 1024,
+                cwd: None,
                 spill_dir: None,
                 tool_call_id: None,
             },
@@ -2623,6 +2576,7 @@ mod tests {
                 command: "sleep 30".into(),
                 timeout_secs: 60,
                 output_limit: 1024,
+                cwd: None,
                 spill_dir: None,
                 tool_call_id: None,
             },

crates/workdir/src/operation.rs

@@ -11,6 +11,10 @@ pub struct CommandRequest {
     pub command: String,
     pub timeout_secs: u64,
     pub output_limit: usize,
+    /// Workdir-relative command directory. Providers validate it against the
+    /// active session before process start.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub cwd: Option<fs_operation::FsPath>,
     /// Provider-local directory where complete output is retained when the
     /// inline result exceeds `output_limit`.
     pub spill_dir: Option<PathBuf>,

crates/workdir/src/workspace.rs

@@ -104,15 +104,5 @@ mod tests {
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct WorkspaceWorkdirSessionOperationRequest {
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub expected_session_fence: Option<String>,
-    #[serde(default, skip_serializing_if = "Vec::is_empty")]
-    pub delegations: Vec<crate::WorkdirDelegationRequest>,
     pub operation: crate::http::WorkdirSessionOperation,
 }
-
-#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
-#[serde(deny_unknown_fields)]
-pub struct WorkspaceWorkdirSessionFence {
-    pub value: String,
-}

crates/worker-runtime/src/http_server.rs

@@ -774,8 +774,7 @@ async fn run_workdir_session_operation(
             .ok_or_else(RuntimeHttpWorkdirError::not_found)?;
         record.session.clone()
     };
-    let applied = workdir::apply_delegation_chain(source, request.delegations).await?;
-    let session = applied.scoped_session.as_ref();
+    let session = source.as_ref();
     let operation = request.operation;
 
     let result = match operation {
@@ -2215,8 +2214,8 @@ mod tests {
     use manifest::{Scope, SharedScope};
     use tower::ServiceExt;
     use workdir::{
-        GrepOutputMode, GrepRequest, LocalWorkdirSession, ReadRequest, StatRequest, Workdir,
-        WorkdirPath, WorkdirSessionCapabilities,
+        GrepOutputMode, GrepRequest, LocalWorkdirSession, StatRequest, Workdir, WorkdirPath,
+        WorkdirSessionCapabilities,
     };
 
     #[tokio::test]
@@ -2770,16 +2769,6 @@ mod tests {
     async fn workdir_session_operations_enforce_owner_and_close_terminally() {
         let temp = tempfile::tempdir().expect("tempdir");
         std::fs::write(temp.path().join("hello.txt"), "hello").expect("write fixture");
-        #[cfg(unix)]
-        {
-            use std::os::unix::fs::symlink;
-            std::fs::create_dir(temp.path().join("granted")).expect("granted directory");
-            std::fs::write(temp.path().join("granted/visible"), "visible")
-                .expect("visible fixture");
-            std::fs::create_dir(temp.path().join("secret")).expect("secret directory");
-            std::fs::write(temp.path().join("secret/key"), "hidden").expect("secret fixture");
-            symlink("../secret/key", temp.path().join("granted/link")).expect("symlink fixture");
-        }
         let scope = SharedScope::new(Scope::writable(temp.path()).expect("scope"));
         let session: WorkdirSessionHandle = Arc::new(LocalWorkdirSession::materialized_bound(
             Workdir::new("wd-1"),
@@ -2813,7 +2802,6 @@ mod tests {
             expires_at: u64::MAX,
         };
         let operation = WorkdirSessionOperationRequest {
-            delegations: Vec::new(),
             operation: WorkdirSessionOperation::Stat(StatRequest {
                 path: WorkdirPath::new("hello.txt").expect("logical path"),
             }),
@@ -2830,7 +2818,6 @@ mod tests {
         assert!(matches!(result, WorkdirSessionOperationResult::Stat(_)));
 
         let grep = WorkdirSessionOperationRequest {
-            delegations: Vec::new(),
             operation: WorkdirSessionOperation::Grep(GrepRequest {
                 pattern: "hello".into(),
                 path: WorkdirPath::new("hello.txt").unwrap(),
@@ -2853,78 +2840,7 @@ mod tests {
         )
         .await
         .expect("grep direct file through provider operation");
-        match result {
-            WorkdirSessionOperationResult::Grep(result) => {
-                assert_eq!(result.match_count, 1);
-                assert_eq!(result.matched_files, 1);
-                assert!(result.output.starts_with("hello.txt\n"));
-                assert!(result.output.contains("> 1 │ hello"));
-            }
-            other => panic!("unexpected workdir grep result: {other:?}"),
-        }
-
-        #[cfg(unix)]
-        {
-            let delegated_visible = WorkdirSessionOperationRequest {
-                delegations: vec![workdir::WorkdirDelegationRequest {
-                    rules: vec![workdir::WorkdirDelegationRule {
-                        target: WorkdirPath::new("granted").unwrap(),
-                        permission: workdir::WorkdirDelegationPermission::Read,
-                        recursive: true,
-                    }],
-                    cwd: WorkdirPath::new("granted").unwrap(),
-                }],
-                operation: WorkdirSessionOperation::Read(ReadRequest {
-                    path: WorkdirPath::new("visible").unwrap(),
-                    offset: 0,
-                    limit: 20,
-                    max_bytes: 1024,
-                }),
-            };
-            let visible = run_workdir_session_operation(
-                State(state.clone()),
-                Path("session-1".to_string()),
-                Some(Extension(auth.clone())),
-                Ok(Json(delegated_visible)),
-            )
-            .await
-            .expect("non-root delegated cwd should resolve once")
-            .0;
-            assert!(matches!(
-                visible,
-                WorkdirSessionOperationResult::Read(result) if result.bytes == b"visible"
-            ));
-
-            let delegated_read = WorkdirSessionOperationRequest {
-                delegations: vec![workdir::WorkdirDelegationRequest {
-                    rules: vec![workdir::WorkdirDelegationRule {
-                        target: WorkdirPath::new("granted").unwrap(),
-                        permission: workdir::WorkdirDelegationPermission::Read,
-                        recursive: true,
-                    }],
-                    cwd: WorkdirPath::new("granted").unwrap(),
-                }],
-                operation: WorkdirSessionOperation::Read(ReadRequest {
-                    path: WorkdirPath::new("link").unwrap(),
-                    offset: 0,
-                    limit: 20,
-                    max_bytes: 1024,
-                }),
-            };
-            let error = run_workdir_session_operation(
-                State(state.clone()),
-                Path("session-1".to_string()),
-                Some(Extension(auth.clone())),
-                Ok(Json(delegated_read)),
-            )
-            .await
-            .expect_err("provider must reject delegated symlink escape");
-            assert_ne!(error.status, StatusCode::OK);
-            assert_eq!(
-                std::fs::read_to_string(temp.path().join("secret/key")).unwrap(),
-                "hidden"
-            );
-        }
+        assert!(matches!(result, WorkdirSessionOperationResult::Grep(_)));
 
         let wrong_owner = RuntimeAuthContext {
             workspace_id: "workspace-b".to_string(),

crates/worker/src/controller.rs

@@ -636,6 +636,7 @@ impl WorkerController {
             runtime_base.to_path_buf(),
             spawned_registry.clone(),
             Some(method_tx.downgrade()),
+            None,
         )
         .await?;
         if let Some(session) = fs_for_view.as_ref() {
@@ -1035,6 +1036,7 @@ 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>,
 ) -> std::io::Result<Option<workdir::WorkdirSessionHandle>>
 where
     C: LlmClient + Clone + 'static,
@@ -1043,21 +1045,26 @@ 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();
-        worker.bind_workdir_session(Some(workdir::delegation_capable_session(
+        let broker = workdir::WorkdirToolBroker::new(
             crate::feature::builtin::manage_workdir::WorkspaceAttachedWorkdirSession::handle(
                 workspace_client,
             ),
-        )));
-    }
-    if feature_config.sub_worker.enabled
+        );
+        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()
-        && !existing.is_delegation_capable()
     {
-        worker.bind_workdir_session(Some(workdir::delegation_capable_session(existing)));
+        let broker = workdir::WorkdirToolBroker::new(existing);
+        worker.bind_workdir_session(Some(broker.tool_session()));
+        workdir_tool_broker = Some(broker);
     }
-    let worker_workdir = worker.workdir_session().cloned();
+    let worker_workdir = workdir_tool_broker
+        .as_ref()
+        .map(workdir::WorkdirToolBroker::tool_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();
@@ -1224,8 +1231,17 @@ where
                 "manage Workdir tools require Backend Workspace API authority",
             ));
         }
+        let shutdown_registry = spawned_registry.clone();
+        let reopen_registry = spawned_registry.clone();
         feature_registry.add_module(
-            crate::feature::builtin::manage_workdir::manage_workdir_feature(workspace_client),
+            crate::feature::builtin::manage_workdir::ManageWorkdirFeature::with_child_lifecycle(
+                workspace_client,
+                Arc::new(move || {
+                    let child_registry = shutdown_registry.clone();
+                    Box::pin(async move { child_registry.shutdown_internal().await })
+                }),
+                Arc::new(move || reopen_registry.reopen_internal()),
+            ),
         );
     }
     if feature_config.workspace_worker_discovery.enabled {
@@ -1287,7 +1303,6 @@ where
     }
 
     let host_worker_observation_provider = worker.worker_observation_provider();
-    let source_workdir_session = worker.workdir_session().cloned();
     {
         let workspace_client = worker.workspace_client_handle();
         let engine = worker.engine_mut();
@@ -1329,7 +1344,7 @@ where
                 runtime_base.clone(),
                 bash_output_dir.clone(),
                 spawner_workspace_root,
-                source_workdir_session,
+                workdir_tool_broker,
                 spawned_registry.clone(),
                 spawner_manifest,
                 prompts,
@@ -2043,7 +2058,16 @@ async fn controller_loop<C, St>(
     // Memory/Workdir teardown so they cannot observe a partially closed Worker.
     worker.stop_feature_runtime("controller shutdown").await;
 
-    if let Some(session) = worker.workdir_session()
+    let child_cleanup_succeeded = match spawned_registry.shutdown_internal().await {
+        Ok(()) => true,
+        Err(error) => {
+            tracing::warn!(%error, "Internal SubWorker cleanup failed before Workdir shutdown");
+            false
+        }
+    };
+
+    if child_cleanup_succeeded
+        && let Some(session) = worker.workdir_session()
         && let Err(error) = session.close().await
     {
         tracing::warn!(%error, "Workdir session close failed");
@@ -3235,4 +3259,21 @@ mod tests {
             other => panic!("expected compact rejection error, got {other:?}"),
         }
     }
+
+    #[test]
+    fn controller_shutdown_orders_child_cleanup_before_workdir_close() {
+        let source = include_str!("controller.rs");
+        let shutdown_start = source
+            .rfind("worker.stop_feature_runtime(\"controller shutdown\")")
+            .expect("controller shutdown block");
+        let shutdown = &source[shutdown_start..];
+        let children = shutdown
+            .find("spawned_registry.shutdown_internal().await")
+            .expect("Internal SubWorker cleanup");
+        let workdir = shutdown
+            .find("session.close().await")
+            .expect("parent Workdir close");
+        assert!(children < workdir);
+        assert!(shutdown.contains("if child_cleanup_succeeded"));
+    }
 }

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

@@ -5,6 +5,8 @@
 //! endpoints, credentials, materializer handles, and operation sessions stay
 //! behind [`WorkspaceClient`].
 
+use std::future::Future;
+use std::pin::Pin;
 use std::sync::Arc;
 
 use agen::tool::{Tool, ToolDefinition, ToolError, ToolExecutionContext, ToolMeta, ToolOutput};
@@ -12,7 +14,7 @@ use async_trait::async_trait;
 use serde::{Deserialize, Serialize};
 use serde_json::json;
 use workdir::http::{WorkdirSessionOperation, WorkdirSessionOperationResult};
-use workdir::workspace::{WorkspaceWorkdirSessionFence, WorkspaceWorkdirSessionOperationRequest};
+use workdir::workspace::WorkspaceWorkdirSessionOperationRequest;
 use workdir::{
     CommandHandle, CommandOutput, CommandOutputRequest, CommandRequest, CommandStatus, EditRequest,
     EditResult, GlobRequest, GlobResult, GrepRequest, GrepResult, ListRequest, ListResult,
@@ -52,16 +54,48 @@ const LIST_DESCRIPTION: &str = "List persistent Workdirs in the current Workspac
 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.";
+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>;
+
 const DELETE_DESCRIPTION: &str = "Request removal of one persistent Workdir by id through durable Backend Workspace authority. The input includes only the Workdir id and a bounded reason. The result reports removed, retained, or attention_required without exposing operation-table or provider internals.";
 
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct ManageWorkdirFeature {
     client: Arc<dyn WorkspaceClient>,
+    before_workdir_release: Option<BeforeWorkdirRelease>,
+    after_workdir_attach: Option<AfterWorkdirAttach>,
+}
+
+impl std::fmt::Debug for ManageWorkdirFeature {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        formatter
+            .debug_struct("ManageWorkdirFeature")
+            .field("client_kind", &self.client.kind())
+            .field("release_guard", &self.before_workdir_release.is_some())
+            .finish()
+    }
 }
 
 impl ManageWorkdirFeature {
     pub fn new(client: Arc<dyn WorkspaceClient>) -> Self {
-        Self { client }
+        Self {
+            client,
+            before_workdir_release: None,
+            after_workdir_attach: None,
+        }
+    }
+
+    pub(crate) fn with_child_lifecycle(
+        client: Arc<dyn WorkspaceClient>,
+        before_workdir_release: BeforeWorkdirRelease,
+        after_workdir_attach: AfterWorkdirAttach,
+    ) -> Self {
+        Self {
+            client,
+            before_workdir_release: Some(before_workdir_release),
+            after_workdir_attach: Some(after_workdir_attach),
+        }
     }
 }
 
@@ -81,7 +115,10 @@ impl FeatureModule for ManageWorkdirFeature {
     }
 
     fn install(&self, context: &mut FeatureInstallContext<'_>) -> Result<(), FeatureInstallError> {
-        let backend = WorkspaceHttpWorkdirBackend::new(self.client.clone());
+        let backend = WorkspaceHttpWorkdirBackend::new(self.client.clone()).with_child_lifecycle(
+            self.before_workdir_release.clone(),
+            self.after_workdir_attach.clone(),
+        );
         for (name, definition) in [
             (
                 LIST_TOOL,
@@ -142,9 +179,21 @@ impl FeatureModule for ManageWorkdirFeature {
     }
 }
 
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 struct WorkspaceHttpWorkdirBackend {
     client: Arc<dyn WorkspaceClient>,
+    before_workdir_release: Option<BeforeWorkdirRelease>,
+    after_workdir_attach: Option<AfterWorkdirAttach>,
+}
+
+impl std::fmt::Debug for WorkspaceHttpWorkdirBackend {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        formatter
+            .debug_struct("WorkspaceHttpWorkdirBackend")
+            .field("client_kind", &self.client.kind())
+            .field("release_guard", &self.before_workdir_release.is_some())
+            .finish()
+    }
 }
 
 /// Worker-local Workdir handle whose operation authority remains in the Workspace Backend.
@@ -156,8 +205,6 @@ struct WorkspaceHttpWorkdirBackend {
 pub struct WorkspaceAttachedWorkdirSession {
     client: Arc<dyn WorkspaceClient>,
     workdir: Workdir,
-    expected_session_fence: Option<String>,
-    delegations: Vec<workdir::WorkdirDelegationRequest>,
 }
 
 impl WorkspaceAttachedWorkdirSession {
@@ -165,8 +212,6 @@ impl WorkspaceAttachedWorkdirSession {
         Arc::new(Self {
             client,
             workdir: Workdir::new("workspace-attachment"),
-            expected_session_fence: None,
-            delegations: Vec::new(),
         })
     }
 
@@ -183,16 +228,13 @@ impl WorkspaceAttachedWorkdirSession {
                 "/api/w/{}/workers/self/workdir-session/operations",
                 encode_path_segment(workspace_id)
             ),
-            serde_json::to_string(&WorkspaceWorkdirSessionOperationRequest {
-                expected_session_fence: self.expected_session_fence.clone(),
-                delegations: self.delegations.clone(),
-                operation,
-            })
-            .map_err(|error| {
-                WorkdirError::Transport(format!(
-                    "failed to encode Workspace Workdir operation: {error}"
-                ))
-            })?,
+            serde_json::to_string(&WorkspaceWorkdirSessionOperationRequest { operation }).map_err(
+                |error| {
+                    WorkdirError::Transport(format!(
+                        "failed to encode Workspace Workdir operation: {error}"
+                    ))
+                },
+            )?,
         );
         let response = self
             .client
@@ -241,59 +283,6 @@ impl WorkdirSession for WorkspaceAttachedWorkdirSession {
         WorkdirSessionCapabilities::ALL
     }
 
-    fn transports_delegation_context(&self) -> bool {
-        true
-    }
-
-    async fn capture_delegation_source(
-        &self,
-        request: &workdir::WorkdirDelegationRequest,
-    ) -> Result<WorkdirSessionHandle, WorkdirError> {
-        let expected_session_fence = if let Some(fence) = &self.expected_session_fence {
-            fence.clone()
-        } else {
-            let workspace_id = self.client.workspace_id().ok_or_else(|| {
-                WorkdirError::Unavailable("Workspace identity is unavailable".to_string())
-            })?;
-            let response = self
-                .client
-                .execute(WorkspaceRequest {
-                    method: WorkspaceRequestMethod::Get,
-                    path: format!(
-                        "/api/w/{}/workers/self/workdir-session/fence",
-                        encode_path_segment(workspace_id)
-                    ),
-                    body: None,
-                })
-                .map_err(|error| {
-                    WorkdirError::Unavailable(format!(
-                        "failed to capture Workdir attachment fence: {error}"
-                    ))
-                })?;
-            let fence: WorkspaceWorkdirSessionFence = serde_json::from_str(&response.body)
-                .map_err(|error| {
-                    WorkdirError::Unavailable(format!(
-                        "invalid Workdir attachment fence response: {error}"
-                    ))
-                })?;
-            fence.value
-        };
-        let mut delegations = self.delegations.clone();
-        delegations.push(request.clone());
-        let candidate = Arc::new(Self {
-            client: self.client.clone(),
-            workdir: self.workdir.clone(),
-            expected_session_fence: Some(expected_session_fence),
-            delegations,
-        });
-        candidate
-            .stat(StatRequest {
-                path: workdir::WorkdirPath::new("").expect("empty Workdir path is valid"),
-            })
-            .await?;
-        Ok(candidate)
-    }
-
     async fn stat(&self, request: StatRequest) -> Result<StatResult, WorkdirError> {
         match self.operate(WorkdirSessionOperation::Stat(request))? {
             WorkdirSessionOperationResult::Stat(result) => Ok(result),
@@ -387,7 +376,21 @@ impl WorkdirSession for WorkspaceAttachedWorkdirSession {
 
 impl WorkspaceHttpWorkdirBackend {
     fn new(client: Arc<dyn WorkspaceClient>) -> Self {
-        Self { client }
+        Self {
+            client,
+            before_workdir_release: None,
+            after_workdir_attach: None,
+        }
+    }
+
+    fn with_child_lifecycle(
+        mut self,
+        before_workdir_release: Option<BeforeWorkdirRelease>,
+        after_workdir_attach: Option<AfterWorkdirAttach>,
+    ) -> Self {
+        self.before_workdir_release = before_workdir_release;
+        self.after_workdir_attach = after_workdir_attach;
+        self
     }
 
     fn workspace_id(&self) -> Result<&str, ToolError> {
@@ -565,11 +568,26 @@ impl Tool for WorkspaceHttpWorkdirTool {
                 parse_input::<WorkdirCreateInput>(input_json)?,
                 ctx.call_id.to_string(),
             ),
-            WorkdirOperation::Attach => self
-                .backend
-                .attach(parse_input::<WorkdirAttachInput>(input_json)?),
+            WorkdirOperation::Attach => {
+                let result = self
+                    .backend
+                    .attach(parse_input::<WorkdirAttachInput>(input_json)?);
+                if result.is_ok()
+                    && let Some(after_attach) = &self.backend.after_workdir_attach
+                {
+                    after_attach();
+                }
+                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| {
+                        ToolError::ExecutionFailed(format!(
+                            "stop Internal SubWorkers before Workdir detach: {error}"
+                        ))
+                    })?;
+                }
                 self.backend.detach()
             }
             WorkdirOperation::Delete => self
@@ -765,6 +783,7 @@ struct WorkdirDeleteInput {
 #[cfg(test)]
 mod tests {
     use std::sync::Mutex;
+    use std::sync::atomic::{AtomicUsize, Ordering};
 
     use super::*;
     use crate::feature::{FeatureModule, FeatureRegistryBuilder};
@@ -1155,6 +1174,7 @@ mod tests {
                 command: "true".to_string(),
                 timeout_secs: 120,
                 output_limit: 1024,
+                cwd: None,
                 spill_dir: Some("/worker-local/bash-output".into()),
                 tool_call_id: Some("call-1".to_string()),
             })
@@ -1178,83 +1198,6 @@ mod tests {
         );
     }
 
-    #[tokio::test]
-    async fn delegated_attached_session_carries_captured_fence_on_operations() {
-        let client = Arc::new(RecordingWorkspaceClient::new(vec![
-            response(json!({"value": "attachment-fence"})),
-            response(json!({
-                "operation": "stat",
-                "result": {"path": "", "kind": "directory", "size": 0}
-            })),
-            response(json!({
-                "operation": "stat",
-                "result": {"path": "visible.txt", "kind": "file", "size": 8}
-            })),
-        ]));
-        let parent = workdir::delegation_capable_session(WorkspaceAttachedWorkdirSession::handle(
-            client.clone(),
-        ));
-        let delegation = parent
-            .delegate(workdir::WorkdirDelegationRequest {
-                rules: vec![workdir::WorkdirDelegationRule {
-                    target: workdir::WorkdirPath::new("").unwrap(),
-                    permission: workdir::WorkdirDelegationPermission::Read,
-                    recursive: false,
-                }],
-                cwd: workdir::WorkdirPath::new("").unwrap(),
-            })
-            .await
-            .unwrap();
-        delegation
-            .scoped_session
-            .stat(StatRequest {
-                path: workdir::WorkdirPath::new("visible.txt").unwrap(),
-            })
-            .await
-            .unwrap();
-
-        let requests = client.requests();
-        assert_eq!(requests.len(), 3);
-        assert_eq!(
-            requests[0].path,
-            "/api/w/workspace%2Ftest/workers/self/workdir-session/fence"
-        );
-        let body: serde_json::Value =
-            serde_json::from_str(requests[2].body.as_deref().unwrap()).unwrap();
-        assert_eq!(body["expected_session_fence"], "attachment-fence");
-        assert_eq!(body["operation"]["operation"], "stat");
-        assert_eq!(body["delegations"][0]["rules"][0]["target"], "");
-    }
-
-    #[tokio::test]
-    async fn attached_provider_rejection_happens_before_delegation_is_returned() {
-        let client = Arc::new(RecordingWorkspaceClient::new(vec![
-            response(json!({"value": "attachment-fence"})),
-            response(json!({"error": "provider rejected delegated write target"})),
-        ]));
-        let parent = workdir::delegation_capable_session(WorkspaceAttachedWorkdirSession::handle(
-            client.clone(),
-        ));
-        let result = parent
-            .delegate(workdir::WorkdirDelegationRequest {
-                rules: vec![workdir::WorkdirDelegationRule {
-                    target: workdir::WorkdirPath::new("linked-target").unwrap(),
-                    permission: workdir::WorkdirDelegationPermission::Write,
-                    recursive: true,
-                }],
-                cwd: workdir::WorkdirPath::new("linked-target").unwrap(),
-            })
-            .await;
-
-        assert!(result.is_err(), "provider rejection must fail before lease");
-        let requests = client.requests();
-        assert_eq!(requests.len(), 2);
-        let validation: serde_json::Value =
-            serde_json::from_str(requests[1].body.as_deref().unwrap()).unwrap();
-        assert_eq!(validation["operation"]["operation"], "stat");
-        assert_eq!(validation["delegations"].as_array().unwrap().len(), 1);
-    }
-
     #[tokio::test]
     async fn attached_session_preserves_typed_provider_validation_error() {
         let client = Arc::new(RecordingWorkspaceClient::new(vec![error_response(
@@ -1298,73 +1241,52 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn nested_attached_session_preserves_full_delegation_chain() {
+    async fn scoped_broker_operations_carry_no_child_context() {
         let client = Arc::new(RecordingWorkspaceClient::new(vec![
-            response(json!({"value": "attachment-fence"})),
             response(json!({
                 "operation": "stat",
-                "result": {"path": "", "kind": "directory", "size": 0}
+                "result": {"path": "visible.txt", "kind": "file", "size": 8}
             })),
             response(json!({
                 "operation": "stat",
-                "result": {"path": "nested", "kind": "directory", "size": 0}
-            })),
-            response(json!({
-                "operation": "stat",
-                "result": {"path": "nested/file", "kind": "file", "size": 1}
+                "result": {"path": "visible.txt", "kind": "file", "size": 8}
             })),
         ]));
-        let parent = workdir::delegation_capable_session(WorkspaceAttachedWorkdirSession::handle(
+        let broker = workdir::WorkdirToolBroker::new(WorkspaceAttachedWorkdirSession::handle(
             client.clone(),
         ));
-        let outer = parent
-            .delegate(workdir::WorkdirDelegationRequest {
-                rules: vec![workdir::WorkdirDelegationRule {
+        let scoped = broker
+            .scope(workdir::WorkdirToolScope {
+                rules: vec![workdir::WorkdirToolScopeRule {
                     target: workdir::WorkdirPath::new("").unwrap(),
-                    permission: workdir::WorkdirDelegationPermission::Read,
+                    permission: workdir::WorkdirToolScopePermission::Read,
                     recursive: true,
                 }],
                 cwd: workdir::WorkdirPath::new("").unwrap(),
+                command: false,
             })
             .await
             .unwrap();
-        let nested = outer
-            .scoped_session
-            .delegate(workdir::WorkdirDelegationRequest {
-                rules: vec![workdir::WorkdirDelegationRule {
-                    target: workdir::WorkdirPath::new("nested").unwrap(),
-                    permission: workdir::WorkdirDelegationPermission::Read,
-                    recursive: true,
-                }],
-                cwd: workdir::WorkdirPath::new("nested").unwrap(),
-            })
-            .await
-            .unwrap();
-        nested
-            .scoped_session
+        scoped
             .stat(StatRequest {
-                path: workdir::WorkdirPath::new("file").unwrap(),
+                path: workdir::WorkdirPath::new("visible.txt").unwrap(),
             })
             .await
             .unwrap();
 
         let requests = client.requests();
-        assert_eq!(requests.len(), 4);
-        let outer_validation: serde_json::Value =
-            serde_json::from_str(requests[1].body.as_deref().unwrap()).unwrap();
-        let nested_validation: serde_json::Value =
-            serde_json::from_str(requests[2].body.as_deref().unwrap()).unwrap();
-        assert_eq!(outer_validation["delegations"].as_array().unwrap().len(), 1);
-        assert_eq!(
-            nested_validation["delegations"].as_array().unwrap().len(),
-            2
-        );
-        let body: serde_json::Value =
-            serde_json::from_str(requests[3].body.as_deref().unwrap()).unwrap();
-        assert_eq!(body["delegations"].as_array().unwrap().len(), 2);
-        assert_eq!(body["delegations"][0]["rules"][0]["target"], "");
-        assert_eq!(body["delegations"][1]["rules"][0]["target"], "nested");
-        assert_eq!(body["operation"]["request"]["path"], "file");
+        assert_eq!(requests.len(), 2);
+        for request in requests {
+            assert_eq!(
+                request.path,
+                "/api/w/workspace%2Ftest/workers/self/workdir-session/operations"
+            );
+            let body: serde_json::Value =
+                serde_json::from_str(request.body.as_deref().unwrap()).unwrap();
+            assert!(body.get("delegations").is_none());
+            assert!(body.get("child").is_none());
+            assert!(body.get("expected_session_fence").is_none());
+        }
     }
 
     #[test]
@@ -1416,4 +1338,86 @@ mod tests {
         assert!(client.requests().is_empty());
         assert!(parse_input::<WorkdirListInput>(r#"{"path":"/tmp"}"#).is_err());
     }
+
+    #[tokio::test]
+    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",
+            "attached": false
+        }))]));
+        let cleanup_calls = Arc::new(AtomicUsize::new(0));
+        let cleanup_calls_for_guard = cleanup_calls.clone();
+        let before_release: BeforeWorkdirRelease = Arc::new(move || {
+            let cleanup_calls = cleanup_calls_for_guard.clone();
+            Box::pin(async move {
+                cleanup_calls.fetch_add(1, Ordering::SeqCst);
+                Ok(())
+            })
+        });
+        let tool = WorkspaceHttpWorkdirTool {
+            backend: WorkspaceHttpWorkdirBackend::new(client.clone())
+                .with_child_lifecycle(Some(before_release), None),
+            operation: WorkdirOperation::Detach,
+        };
+
+        tool.execute("{}", ToolExecutionContext::default())
+            .await
+            .unwrap();
+
+        assert_eq!(cleanup_calls.load(Ordering::SeqCst), 1);
+        assert_eq!(client.requests().len(), 1);
+        assert_eq!(
+            client.requests()[0].path,
+            "/api/w/workspace%2Ftest/workers/self/workdir-attachment"
+        );
+    }
+
+    #[tokio::test]
+    async fn detach_does_not_release_backend_when_child_cleanup_fails() {
+        let client = Arc::new(RecordingWorkspaceClient::new(Vec::new()));
+        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_child_lifecycle(Some(before_release), None),
+            operation: WorkdirOperation::Detach,
+        };
+
+        let error = tool
+            .execute("{}", ToolExecutionContext::default())
+            .await
+            .unwrap_err();
+
+        assert!(error.to_string().contains("stop Internal SubWorkers"));
+        assert!(client.requests().is_empty());
+    }
+
+    #[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",
+            "attached": true
+        }))]));
+        let reopen_calls = Arc::new(AtomicUsize::new(0));
+        let reopen_calls_for_hook = reopen_calls.clone();
+        let after_attach: AfterWorkdirAttach = Arc::new(move || {
+            reopen_calls_for_hook.fetch_add(1, Ordering::SeqCst);
+        });
+        let tool = WorkspaceHttpWorkdirTool {
+            backend: WorkspaceHttpWorkdirBackend::new(client)
+                .with_child_lifecycle(None, Some(after_attach)),
+            operation: WorkdirOperation::Attach,
+        };
+
+        tool.execute(
+            r#"{"workdir_id":"wd-attached"}"#,
+            ToolExecutionContext::default(),
+        )
+        .await
+        .unwrap();
+
+        assert_eq!(reopen_calls.load(Ordering::SeqCst), 1);
+    }
 }

crates/worker/src/internal_worker.rs

@@ -709,7 +709,7 @@ pub(crate) fn prepare_internal_worker_from_spec(
         }
 
         Box::pin(prepare_internal_worker_session(
-            worker, store, visibility, None, None,
+            worker, store, visibility, None, None, None,
         ))
         .await
     })
@@ -746,13 +746,16 @@ 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>,
 ) -> Result<InternalWorkerSessionHandle, InternalWorkerSessionError> {
     let (event_tx, _event_rx) = broadcast::channel(256);
     let sink = worker.sink();
     spawn_internal_log_event_bridge(sink.clone(), event_tx.clone());
     let alerter = Alerter::new(event_tx.clone());
     let in_flight = InFlightEvents::new(event_tx.clone());
-    if let Some(session) = worker.workdir_session() {
+    if let Some(broker) = command_event_broker.as_ref() {
+        wire_workdir_command_events(&broker.tool_session(), &in_flight);
+    } else if let Some(session) = worker.workdir_session() {
         wire_workdir_command_events(session, &in_flight);
     }
     let actor_in_flight = in_flight.clone();
@@ -887,6 +890,7 @@ pub(crate) async fn spawn_prepared_internal_worker_session(
         InternalWorkerVisibility::ServicePrivate,
         None,
         on_turn_end,
+        None,
     )
     .await?;
     handle.send(input).await?;

crates/worker/src/spawn/registry.rs

@@ -12,7 +12,7 @@ use std::collections::{BTreeMap, HashSet};
 use std::io;
 use std::sync::{
     Arc, Mutex,
-    atomic::{AtomicBool, AtomicU64, Ordering},
+    atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering},
 };
 use std::time::Instant;
 
@@ -23,9 +23,9 @@ use protocol::{Event, InternalWorkerKind, InternalWorkerRef, InternalWorkerSnaps
 use session_store::{
     LoggedItem, WorkerMetadataStore, WorkerReclaimedChild, WorkerSpawnedChild, WorkerStoreError,
 };
-use tokio::sync::broadcast;
+use tokio::sync::{Notify, broadcast};
 use tracing::warn;
-use workdir::WorkdirDelegation;
+use workdir::WorkdirScopeLease;
 
 use crate::internal_worker::{InternalWorkerSessionHandle, InternalWorkerVisibility};
 use crate::runtime::dir::{RuntimeDir, SpawnedWorkerRecord};
@@ -68,10 +68,11 @@ pub(crate) struct SubWorkerStopSummary {
 pub(crate) struct InternalSpawnedWorkerRecord {
     pub worker_name: String,
     pub scope_delegated: Vec<ScopeRule>,
-    pub workdir_delegation: Arc<WorkdirDelegation>,
+    pub workdir_tool_scope: Arc<WorkdirScopeLease>,
     #[cfg(test)]
     pub installed_tools: Arc<[String]>,
     pub session: InternalWorkerSessionHandle,
+    pub child_registry: Arc<SpawnedWorkerRegistry>,
     change_tracker: Option<tools::Tracker>,
     started_at: Instant,
     stop_lock: Arc<tokio::sync::Mutex<()>>,
@@ -86,18 +87,20 @@ impl InternalSpawnedWorkerRecord {
     pub(crate) fn new(
         worker_name: String,
         scope_delegated: Vec<ScopeRule>,
-        workdir_delegation: WorkdirDelegation,
+        workdir_tool_scope: WorkdirScopeLease,
         #[cfg(test)] installed_tools: Vec<String>,
         session: InternalWorkerSessionHandle,
+        child_registry: Arc<SpawnedWorkerRegistry>,
         change_tracker: Option<tools::Tracker>,
     ) -> Self {
         Self {
             worker_name,
             scope_delegated,
-            workdir_delegation: Arc::new(workdir_delegation),
+            workdir_tool_scope: Arc::new(workdir_tool_scope),
             #[cfg(test)]
             installed_tools: installed_tools.into(),
             session,
+            child_registry,
             change_tracker,
             started_at: Instant::now(),
             stop_lock: Arc::new(tokio::sync::Mutex::new(())),
@@ -235,18 +238,56 @@ pub(crate) struct InternalSpawnReservation {
 }
 
 impl InternalSpawnReservation {
-    pub(crate) fn commit(mut self, record: InternalSpawnedWorkerRecord) -> io::Result<()> {
-        if record.worker_name != self.worker_name {
-            return Err(io::Error::new(
+    pub(crate) async fn commit(mut self, record: InternalSpawnedWorkerRecord) -> io::Result<()> {
+        let rejection = if record.worker_name != self.worker_name {
+            Some(io::Error::new(
                 io::ErrorKind::InvalidInput,
                 "internal SubWorker reservation name does not match record name",
-            ));
+            ))
+        } else {
+            match self.registry.internal_records.lock() {
+                Ok(mut records) => {
+                    if self.registry.internal_shutting_down.load(Ordering::Acquire) {
+                        Some(io::Error::new(
+                            io::ErrorKind::Interrupted,
+                            "internal SubWorker registry is shutting down",
+                        ))
+                    } else {
+                        records.push(record.clone());
+                        None
+                    }
+                }
+                Err(_) => Some(io::Error::other(
+                    "internal spawned-worker registry lock poisoned",
+                )),
+            }
+        };
+        if let Some(error) = rejection {
+            let mut cleanup_failures = Vec::new();
+            if let Err(cleanup) = record.session.stop().await {
+                cleanup_failures.push(format!("stop rejected Internal SubWorker: {cleanup}"));
+            }
+            if let Err(cleanup) = Box::pin(record.child_registry.shutdown_internal()).await {
+                cleanup_failures.push(format!(
+                    "stop rejected Internal SubWorker descendants: {cleanup}"
+                ));
+            }
+            if let Err(cleanup) = record.workdir_tool_scope.close().await {
+                cleanup_failures.push(format!(
+                    "close rejected Internal SubWorker Workdir tools: {cleanup}"
+                ));
+            }
+            if cleanup_failures.is_empty() {
+                return Err(error);
+            }
+            self.registry
+                .internal_spawn_cleanup_failed
+                .store(true, Ordering::Release);
+            return Err(io::Error::other(format!(
+                "{error}; {}",
+                cleanup_failures.join("; ")
+            )));
         }
-        self.registry
-            .internal_records
-            .lock()
-            .map_err(|_| io::Error::other("internal spawned-worker registry lock poisoned"))?
-            .push(record.clone());
         self.registry.start_protocol_forwarding(record);
         self.committed = true;
         Ok(())
@@ -260,6 +301,10 @@ impl Drop for InternalSpawnReservation {
                 names.remove(&self.worker_name);
             }
         }
+        self.registry
+            .pending_internal_spawns
+            .fetch_sub(1, Ordering::AcqRel);
+        self.registry.pending_internal_notify.notify_waiters();
     }
 }
 
@@ -267,6 +312,10 @@ pub struct SpawnedWorkerRegistry {
     internal_records: std::sync::Mutex<Vec<InternalSpawnedWorkerRecord>>,
     service_records: std::sync::Mutex<Vec<InternalServiceWorkerRecord>>,
     internal_names: std::sync::Mutex<HashSet<String>>,
+    internal_shutting_down: AtomicBool,
+    pending_internal_spawns: AtomicUsize,
+    pending_internal_notify: Notify,
+    internal_spawn_cleanup_failed: AtomicBool,
     parent_scope: Option<SharedScope>,
     parent_protocol: Mutex<Option<(broadcast::Sender<Event>, String)>>,
 }
@@ -283,6 +332,10 @@ impl SpawnedWorkerRegistry {
             internal_records: std::sync::Mutex::new(Vec::new()),
             service_records: std::sync::Mutex::new(Vec::new()),
             internal_names: std::sync::Mutex::new(HashSet::new()),
+            internal_shutting_down: AtomicBool::new(false),
+            pending_internal_spawns: AtomicUsize::new(0),
+            pending_internal_notify: Notify::new(),
+            internal_spawn_cleanup_failed: AtomicBool::new(false),
             parent_scope: None,
             parent_protocol: Mutex::new(None),
         })
@@ -294,6 +347,10 @@ impl SpawnedWorkerRegistry {
             internal_records: std::sync::Mutex::new(Vec::new()),
             service_records: std::sync::Mutex::new(Vec::new()),
             internal_names: std::sync::Mutex::new(HashSet::new()),
+            internal_shutting_down: AtomicBool::new(false),
+            pending_internal_spawns: AtomicUsize::new(0),
+            pending_internal_notify: Notify::new(),
+            internal_spawn_cleanup_failed: AtomicBool::new(false),
             parent_scope: None,
             parent_protocol: Mutex::new(None),
         })
@@ -304,6 +361,10 @@ impl SpawnedWorkerRegistry {
             internal_records: std::sync::Mutex::new(Vec::new()),
             service_records: std::sync::Mutex::new(Vec::new()),
             internal_names: std::sync::Mutex::new(HashSet::new()),
+            internal_shutting_down: AtomicBool::new(false),
+            pending_internal_spawns: AtomicUsize::new(0),
+            pending_internal_notify: Notify::new(),
+            internal_spawn_cleanup_failed: AtomicBool::new(false),
             parent_scope: Some(parent_scope),
             parent_protocol: Mutex::new(None),
         })
@@ -383,6 +444,10 @@ impl SpawnedWorkerRegistry {
                 internal_records: std::sync::Mutex::new(Vec::new()),
                 service_records: std::sync::Mutex::new(Vec::new()),
                 internal_names: std::sync::Mutex::new(HashSet::new()),
+                internal_shutting_down: AtomicBool::new(false),
+                pending_internal_spawns: AtomicUsize::new(0),
+                pending_internal_notify: Notify::new(),
+                internal_spawn_cleanup_failed: AtomicBool::new(false),
                 parent_scope,
                 parent_protocol: Mutex::new(None),
             }),
@@ -394,6 +459,16 @@ impl SpawnedWorkerRegistry {
         self: &Arc<Self>,
         worker_name: String,
     ) -> io::Result<InternalSpawnReservation> {
+        let records = self
+            .internal_records
+            .lock()
+            .map_err(|_| io::Error::other("internal Worker registry lock poisoned"))?;
+        if self.internal_shutting_down.load(Ordering::Acquire) {
+            return Err(io::Error::new(
+                io::ErrorKind::Interrupted,
+                "internal SubWorker registry is shutting down",
+            ));
+        }
         let mut names = self
             .internal_names
             .lock()
@@ -404,7 +479,9 @@ impl SpawnedWorkerRegistry {
                 format!("spawned worker `{worker_name}` is already registered"),
             ));
         }
+        self.pending_internal_spawns.fetch_add(1, Ordering::AcqRel);
         drop(names);
+        drop(records);
         Ok(InternalSpawnReservation {
             registry: Arc::clone(self),
             worker_name,
@@ -679,18 +756,11 @@ impl SpawnedWorkerRegistry {
             .unwrap_or_default()
     }
 
-    pub(crate) fn reclaim_internal_scope(&self, worker_name: &str) -> io::Result<bool> {
-        let record = self.get_internal(worker_name).ok_or_else(|| {
-            io::Error::new(io::ErrorKind::NotFound, "internal SubWorker not found")
-        })?;
-        self.reclaim_record_scope(&record)
-    }
-
     fn reclaim_record_scope(&self, record: &InternalSpawnedWorkerRecord) -> io::Result<bool> {
         if !record.claim_scope_reclaim() {
             return Ok(false);
         }
-        record.workdir_delegation.release();
+        record.workdir_tool_scope.revoke();
         let result = if let Some(parent_scope) = &self.parent_scope {
             parent_scope
                 .update(|current| current.with_removed_deny_rules(delegated_write_rules(record)))
@@ -705,6 +775,58 @@ impl SpawnedWorkerRegistry {
         result
     }
 
+    pub(crate) async fn close_internal_scope(&self, name: &str) -> io::Result<bool> {
+        let Some(record) = self.get_internal(name) else {
+            return Ok(false);
+        };
+        Box::pin(record.child_registry.shutdown_internal()).await?;
+        record
+            .workdir_tool_scope
+            .close()
+            .await
+            .map_err(|error| io::Error::other(error.to_string()))?;
+        self.reclaim_record_scope(&record)
+    }
+
+    pub(crate) async fn shutdown_internal(&self) -> io::Result<()> {
+        let names = {
+            let records = self
+                .internal_records
+                .lock()
+                .map_err(|_| io::Error::other("internal Worker registry lock poisoned"))?;
+            self.internal_shutting_down.store(true, Ordering::Release);
+            records
+                .iter()
+                .map(|record| record.worker_name.clone())
+                .collect::<Vec<_>>()
+        };
+        loop {
+            let notified = self.pending_internal_notify.notified();
+            if self.pending_internal_spawns.load(Ordering::Acquire) == 0 {
+                break;
+            }
+            notified.await;
+        }
+        let mut first_error = None;
+        for name in names {
+            if let Err(error) = self.remove_internal(&name).await {
+                first_error.get_or_insert(error);
+            }
+        }
+        if first_error.is_none() && self.internal_spawn_cleanup_failed.load(Ordering::Acquire) {
+            first_error = Some(io::Error::other(
+                "an in-flight Internal SubWorker failed cleanup during shutdown",
+            ));
+        }
+        first_error.map_or(Ok(()), Err)
+    }
+
+    pub(crate) fn reopen_internal(&self) {
+        self.internal_shutting_down.store(false, Ordering::Release);
+        self.internal_spawn_cleanup_failed
+            .store(false, Ordering::Release);
+    }
+
     /// Stop one direct Internal SubWorker and discard its registry/scope state.
     ///
     /// The child actor must acknowledge its stop before the registry is removed.
@@ -731,6 +853,12 @@ impl SpawnedWorkerRegistry {
             .stop()
             .await
             .map_err(|error| io::Error::other(error.to_string()))?;
+        Box::pin(record.child_registry.shutdown_internal()).await?;
+        record
+            .workdir_tool_scope
+            .close()
+            .await
+            .map_err(|error| io::Error::other(error.to_string()))?;
         let summary = record.stop_summary();
         self.reclaim_record_scope(&record)?;
         let removed =
@@ -966,7 +1094,7 @@ mod tests {
             deny: Vec::new(),
         })
         .unwrap();
-        let source = workdir::delegation_capable_session(Arc::new(
+        let source = workdir::WorkdirToolBroker::new(Arc::new(
             workdir::LocalWorkdirSession::materialized_bound(
                 workdir::Workdir::new("registry-test"),
                 root.clone(),
@@ -976,13 +1104,14 @@ mod tests {
             ),
         ));
         let delegation = source
-            .delegate(workdir::WorkdirDelegationRequest {
-                rules: vec![workdir::WorkdirDelegationRule {
+            .scope(workdir::WorkdirToolScope {
+                rules: vec![workdir::WorkdirToolScopeRule {
                     target: workdir::WorkdirPath::new("").unwrap(),
-                    permission: workdir::WorkdirDelegationPermission::Read,
+                    permission: workdir::WorkdirToolScopePermission::Read,
                     recursive: true,
                 }],
                 cwd: workdir::WorkdirPath::new("").unwrap(),
+                command: false,
             })
             .await
             .unwrap();
@@ -993,6 +1122,7 @@ mod tests {
                 delegation,
                 Vec::new(),
                 session,
+                registry(),
                 None,
             ),
             sender,
@@ -1230,6 +1360,143 @@ mod tests {
         }
     }
 
+    #[tokio::test]
+    async fn parent_shutdown_stops_all_internal_workers_before_returning() {
+        let registry = registry();
+        for name in ["first", "second"] {
+            let (record, _events) = record(name, InternalWorkerVisibility::ParentClient).await;
+            record
+                .session
+                .force_status(InternalWorkerSessionStatus::Running);
+            install_record(&registry, record);
+        }
+
+        registry.shutdown_internal().await.unwrap();
+
+        assert!(registry.list_internal().is_empty());
+        assert!(registry.get_internal("first").is_none());
+        assert!(registry.get_internal("second").is_none());
+    }
+
+    #[tokio::test]
+    async fn shutdown_rejects_new_reservations_until_reopened() {
+        let registry = registry();
+        registry.shutdown_internal().await.unwrap();
+        assert!(registry.reserve_internal_name("late-child".into()).is_err());
+
+        registry.reopen_internal();
+        let reservation = registry.reserve_internal_name("late-child".into()).unwrap();
+        drop(reservation);
+    }
+
+    #[tokio::test]
+    async fn concurrent_commit_and_shutdown_leave_no_live_internal_worker() {
+        let registry = registry();
+        let reservation = registry
+            .reserve_internal_name("racing-child".into())
+            .unwrap();
+        let (record, _events) =
+            record("racing-child", InternalWorkerVisibility::ParentClient).await;
+        let scope = record.workdir_tool_scope.clone();
+        let barrier = Arc::new(tokio::sync::Barrier::new(2));
+        let commit_barrier = barrier.clone();
+        let commit = tokio::spawn(async move {
+            commit_barrier.wait().await;
+            reservation.commit(record).await
+        });
+        let shutdown_registry = registry.clone();
+        let shutdown = tokio::spawn(async move {
+            barrier.wait().await;
+            shutdown_registry.shutdown_internal().await
+        });
+
+        let commit = commit.await.unwrap();
+        shutdown.await.unwrap().unwrap();
+        if let Err(error) = commit {
+            assert_eq!(error.kind(), io::ErrorKind::Interrupted);
+        }
+
+        assert!(registry.list_internal().is_empty());
+        assert!(!scope.is_active());
+    }
+
+    #[tokio::test]
+    async fn shutdown_fences_a_reservation_that_has_not_committed() {
+        let registry = registry();
+        let reservation = registry
+            .reserve_internal_name("racing-child".into())
+            .unwrap();
+        let (record, _events) =
+            record("racing-child", InternalWorkerVisibility::ParentClient).await;
+
+        let mut shutdown = {
+            let registry = registry.clone();
+            tokio::spawn(async move { registry.shutdown_internal().await })
+        };
+        while !registry.internal_shutting_down.load(Ordering::Acquire) {
+            tokio::task::yield_now().await;
+        }
+        assert!(
+            tokio::time::timeout(std::time::Duration::from_millis(50), &mut shutdown)
+                .await
+                .is_err(),
+            "shutdown must wait for the pending spawn to roll back"
+        );
+        let error = reservation.commit(record).await.unwrap_err();
+        assert_eq!(error.kind(), io::ErrorKind::Interrupted);
+        shutdown.await.unwrap().unwrap();
+    }
+
+    #[tokio::test]
+    async fn rejected_spawn_cleanup_failure_keeps_shutdown_failed_closed() {
+        let registry = registry();
+        let reservation = registry
+            .reserve_internal_name("cleanup-failure".into())
+            .unwrap();
+        let (record, _events) =
+            record("cleanup-failure", InternalWorkerVisibility::ParentClient).await;
+        record.session.force_stop_failure();
+        let shutdown = {
+            let registry = registry.clone();
+            tokio::spawn(async move { registry.shutdown_internal().await })
+        };
+        while !registry.internal_shutting_down.load(Ordering::Acquire) {
+            tokio::task::yield_now().await;
+        }
+
+        let error = reservation.commit(record).await.unwrap_err();
+        assert!(
+            error
+                .to_string()
+                .contains("stop rejected Internal SubWorker")
+        );
+        let shutdown_error = shutdown.await.unwrap().unwrap_err();
+        assert!(
+            shutdown_error
+                .to_string()
+                .contains("failed cleanup during shutdown")
+        );
+        assert!(registry.internal_shutting_down.load(Ordering::Acquire));
+    }
+
+    #[tokio::test]
+    async fn shutdown_recursively_stops_grandchildren_before_parent_scope_release() {
+        let registry = registry();
+        let (child, _child_events) = record("child", InternalWorkerVisibility::ParentClient).await;
+        let child_registry = child.child_registry.clone();
+        let (grandchild, _grandchild_events) =
+            record("grandchild", InternalWorkerVisibility::ParentClient).await;
+        let grandchild_scope = grandchild.workdir_tool_scope.clone();
+        install_record(&child_registry, grandchild);
+        install_record(&registry, child);
+
+        registry.shutdown_internal().await.unwrap();
+
+        assert!(registry.list_internal().is_empty());
+        assert!(child_registry.list_internal().is_empty());
+        assert!(!grandchild_scope.is_active());
+    }
+
     #[tokio::test]
     async fn running_worker_is_stopped_before_removal() {
         let registry = registry();

crates/worker/src/spawn/tool.rs

@@ -22,8 +22,7 @@ use manifest::{
 use serde::Deserialize;
 use tokio::sync::mpsc;
 use workdir::{
-    WorkdirDelegationPermission, WorkdirDelegationRequest, WorkdirDelegationRule, WorkdirPath,
-    WorkdirSessionHandle,
+    WorkdirToolBroker, WorkdirToolScope, WorkdirToolScopePermission, WorkdirToolScopeRule,
 };
 
 use crate::PromptCatalogSource;
@@ -64,6 +63,9 @@ struct SubWorkerSpawnInput {
     /// spawner's explicit delegation authority; direct tool scope alone is not
     /// sufficient. Omit `recursive` for normal workspace/worktree delegation; it defaults to true.
     scope: Vec<ScopeRuleInput>,
+    /// Explicitly grant command execution through the parent-owned Workdir tool broker.
+    #[serde(default)]
+    command: bool,
     /// Binds an actual read-only builtin Reviewer child to the current Merge Request candidate.
     /// Review capability material is generated by the trusted spawn layer.
     #[serde(default)]
@@ -284,8 +286,8 @@ pub struct SubWorkerSpawnTool {
     workspace_root: PathBuf,
     /// Directory the spawned SubWorker's tools should use when the LLM did not
     /// override it. Defaults to the spawner's cwd.
-    /// Active provider-backed Workdir session from which child leases are captured.
-    source_workdir_session: Option<WorkdirSessionHandle>,
+    /// Parent-owned broker for scoped Workdir tool execution.
+    workdir_tool_broker: Option<WorkdirToolBroker>,
     /// Parent-owned in-memory registry shared by the five SubWorker tools.
     registry: Arc<SpawnedWorkerRegistry>,
     /// Spawner's resolved Manifest. `profile = "inherit"` derives the
@@ -312,7 +314,7 @@ impl SubWorkerSpawnTool {
         runtime_base: PathBuf,
         bash_output_dir: PathBuf,
         workspace_root: PathBuf,
-        source_workdir_session: Option<WorkdirSessionHandle>,
+        workdir_tool_broker: Option<WorkdirToolBroker>,
         registry: Arc<SpawnedWorkerRegistry>,
         spawner_manifest: WorkerManifest,
         prompt_loader: PromptCatalogSource,
@@ -325,7 +327,7 @@ impl SubWorkerSpawnTool {
             runtime_base,
             bash_output_dir,
             workspace_root,
-            source_workdir_session,
+            workdir_tool_broker,
             registry,
             spawner_manifest,
             prompt_loader,
@@ -358,6 +360,11 @@ fn validate_reviewer_handoff(input: &SubWorkerSpawnInput) -> Result<(), ToolErro
             "Merge Request Reviewer SubWorkers must include writable delegated scope".to_string(),
         ));
     }
+    if !input.command {
+        return Err(ToolError::InvalidArgument(
+            "Merge Request Reviewer SubWorkers require an explicit command grant".to_string(),
+        ));
+    }
     Ok(())
 }
 
@@ -387,7 +394,7 @@ impl Tool for SubWorkerSpawnTool {
             .reserve_internal_name(input.name.clone())
             .map_err(|error| ToolError::InvalidArgument(error.to_string()))?;
 
-        let mut workdir_rules = parse_workdir_scope(&input.scope)?;
+        let workdir_rules = parse_workdir_scope(&input.scope)?;
         let child_bash_output_dir = self.bash_output_dir.join("sub-workers").join(&input.name);
         tokio::fs::create_dir_all(&child_bash_output_dir)
             .await
@@ -397,28 +404,15 @@ impl Tool for SubWorkerSpawnTool {
                     child_bash_output_dir.display()
                 ))
             })?;
-        let source_workdir_session =
-            require_active_workdir_session(self.source_workdir_session.as_ref())?;
-        let transports_delegation_context = source_workdir_session.transports_delegation_context();
-        // Provider-transported sessions resolve every delegation rule in the
-        // receiving Workdir namespace. The Bash spill directory instead belongs
-        // to this Worker host, so forwarding it would widen the request with a
-        // foreign absolute path and fail the provider's existing scope check.
-        if !transports_delegation_context {
-            workdir_rules.push(WorkdirDelegationRule {
-                target: WorkdirPath::new_scoped(child_bash_output_dir.to_string_lossy())
-                    .map_err(|error| ToolError::ExecutionFailed(error.to_string()))?,
-                permission: WorkdirDelegationPermission::Read,
-                recursive: true,
-            });
-        }
-        let delegation_request = workdir_delegation_request(input.cwd.as_deref(), workdir_rules)?;
-        let workdir_delegation = source_workdir_session
-            .delegate(delegation_request)
+        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 workdir_scope = workdir_tool_broker
+            .scope(tool_scope)
             .await
             .map_err(|error| {
-                ToolError::InvalidArgument(format!("delegate Workdir session: {error}"))
+                ToolError::InvalidArgument(format!("scope parent-owned Workdir tools: {error}"))
             })?;
+        let child_workdir_tool_broker = workdir_scope.broker();
 
         let spawn_selector =
             parse_spawn_profile_selector(input.profile.as_deref()).map_err(|msg| {
@@ -507,7 +501,6 @@ impl Tool for SubWorkerSpawnTool {
         )
         .await
         .map_err(|error| ToolError::ExecutionFailed(format!("build Internal Worker: {error}")))?;
-        child.bind_workdir_session(Some(workdir_delegation.scoped_session.clone()));
         child
             .add_scope_rules([ScopeRule {
                 target: child_bash_output_dir.clone(),
@@ -527,6 +520,7 @@ impl Tool for SubWorkerSpawnTool {
             self.runtime_base.clone(),
             child_registry.clone(),
             None,
+            Some(child_workdir_tool_broker.clone()),
         )
         .await
         .map_err(|error| {
@@ -555,13 +549,16 @@ impl Tool for SubWorkerSpawnTool {
                     InternalWorkerSessionStatus::Failed | InternalWorkerSessionStatus::Stopped
                 ) {
                     if let Some(registry) = registry.upgrade() {
-                        if let Err(error) = registry.reclaim_internal_scope(&child_name) {
-                            tracing::warn!(
-                                child_name,
-                                %error,
-                                "failed to reclaim delegated scope after Internal SubWorker failure"
-                            );
-                        }
+                        let child_name = child_name.clone();
+                        tokio::spawn(async move {
+                            if let Err(error) = registry.close_internal_scope(&child_name).await {
+                                tracing::warn!(
+                                    child_name,
+                                    %error,
+                                    "failed to close parent-owned Workdir tools after Internal SubWorker failure"
+                                );
+                            }
+                        });
                     }
                 }
                 let message = format!(
@@ -569,6 +566,7 @@ impl Tool for SubWorkerSpawnTool {
                 );
                 parent_notifications.notify(child_name.clone(), message, true);
             })),
+            Some(child_workdir_tool_broker.clone()),
         )
         .await;
         let session = session_result.map_err(|error| {
@@ -619,15 +617,19 @@ impl Tool for SubWorkerSpawnTool {
                 ),
                 body.to_string(),
             );
-            let response = self
-                .workspace_context
-                .client()
-                .execute(request)
-                .map_err(|error| {
-                    ToolError::ExecutionFailed(format!("register review capability: {error}"))
-                })?;
+            let response = match self.workspace_context.client().execute(request) {
+                Ok(response) => response,
+                Err(error) => {
+                    let _ = session.stop().await;
+                    let _ = workdir_scope.close().await;
+                    return Err(ToolError::ExecutionFailed(format!(
+                        "register review capability: {error}"
+                    )));
+                }
+            };
             if !response.is_success() {
                 let _ = session.stop().await;
+                let _ = workdir_scope.close().await;
                 return Err(ToolError::ExecutionFailed(format!(
                     "register review capability failed with status {}: {}",
                     response.status, response.body
@@ -638,14 +640,14 @@ impl Tool for SubWorkerSpawnTool {
         let record = crate::spawn::registry::InternalSpawnedWorkerRecord::new(
             input.name.clone(),
             scope_allow,
-            workdir_delegation,
+            workdir_scope,
             #[cfg(test)]
             installed_tools,
             session.clone(),
+            child_registry,
             child_change_tracker,
         );
-        if let Err(error) = name_reservation.commit(record) {
-            let _ = session.stop().await;
+        if let Err(error) = name_reservation.commit(record).await {
             return Err(ToolError::ExecutionFailed(format!(
                 "register Internal Worker session: {error}"
             )));
@@ -691,18 +693,18 @@ fn logical_workdir_path(value: &str, field: &str) -> Result<FsPath, ToolError> {
     })
 }
 
-fn parse_workdir_scope(rules: &[ScopeRuleInput]) -> Result<Vec<WorkdirDelegationRule>, ToolError> {
+fn parse_workdir_scope(rules: &[ScopeRuleInput]) -> Result<Vec<WorkdirToolScopeRule>, ToolError> {
     if rules.is_empty() {
         return Err(ToolError::InvalidArgument("scope must not be empty".into()));
     }
     rules
         .iter()
         .map(|rule| {
-            Ok(WorkdirDelegationRule {
+            Ok(WorkdirToolScopeRule {
                 target: logical_workdir_path(&rule.target, "scope.target")?,
                 permission: match rule.permission {
-                    PermissionInput::Read => WorkdirDelegationPermission::Read,
-                    PermissionInput::Write => WorkdirDelegationPermission::Write,
+                    PermissionInput::Read => WorkdirToolScopePermission::Read,
+                    PermissionInput::Write => WorkdirToolScopePermission::Write,
                 },
                 recursive: rule.recursive,
             })
@@ -710,22 +712,24 @@ fn parse_workdir_scope(rules: &[ScopeRuleInput]) -> Result<Vec<WorkdirDelegation
         .collect()
 }
 
-fn workdir_delegation_request(
+fn workdir_tool_scope(
     cwd: Option<&str>,
-    rules: Vec<WorkdirDelegationRule>,
-) -> Result<WorkdirDelegationRequest, ToolError> {
-    Ok(WorkdirDelegationRequest {
+    rules: Vec<WorkdirToolScopeRule>,
+    command: bool,
+) -> Result<WorkdirToolScope, ToolError> {
+    Ok(WorkdirToolScope {
         rules,
         cwd: logical_workdir_path(cwd.unwrap_or("."), "cwd")?,
+        command,
     })
 }
 
-fn require_active_workdir_session(
-    session: Option<&WorkdirSessionHandle>,
-) -> Result<&WorkdirSessionHandle, ToolError> {
-    session.ok_or_else(|| {
+fn require_workdir_tool_broker(
+    broker: Option<&WorkdirToolBroker>,
+) -> Result<&WorkdirToolBroker, ToolError> {
+    broker.ok_or_else(|| {
         ToolError::InvalidArgument(
-            "SubWorkerSpawn requires an active Workdir session; attach a Workdir before delegating filesystem access"
+            "SubWorkerSpawn requires parent-owned Workdir tools; attach a Workdir before granting filesystem access"
                 .to_string(),
         )
     })
@@ -963,7 +967,7 @@ pub(crate) fn sub_worker_spawn_tool(
     runtime_base: PathBuf,
     bash_output_dir: PathBuf,
     workspace_root: PathBuf,
-    source_workdir_session: Option<WorkdirSessionHandle>,
+    workdir_tool_broker: Option<WorkdirToolBroker>,
     registry: Arc<SpawnedWorkerRegistry>,
     spawner_manifest: WorkerManifest,
     prompts: Arc<ArcSwap<PromptCatalog>>,
@@ -975,7 +979,7 @@ pub(crate) fn sub_worker_spawn_tool(
         runtime_base,
         bash_output_dir,
         workspace_root,
-        source_workdir_session,
+        workdir_tool_broker,
         registry,
         spawner_manifest,
         prompts,
@@ -989,7 +993,7 @@ fn sub_worker_spawn_tool_impl(
     runtime_base: PathBuf,
     bash_output_dir: PathBuf,
     workspace_root: PathBuf,
-    source_workdir_session: Option<WorkdirSessionHandle>,
+    workdir_tool_broker: Option<WorkdirToolBroker>,
     registry: Arc<SpawnedWorkerRegistry>,
     spawner_manifest: WorkerManifest,
     prompts: Arc<ArcSwap<PromptCatalog>>,
@@ -1021,7 +1025,7 @@ fn sub_worker_spawn_tool_impl(
             runtime_base.clone(),
             bash_output_dir.clone(),
             workspace_root.clone(),
-            source_workdir_session.clone(),
+            workdir_tool_broker.clone(),
             registry.clone(),
             spawner_manifest.clone(),
             prompts.load_full().source(),
@@ -1054,12 +1058,12 @@ mod tests {
     };
 
     #[test]
-    fn missing_active_workdir_session_fails_deterministically() {
-        let error = require_active_workdir_session(None).unwrap_err();
+    fn missing_parent_workdir_tool_broker_fails_deterministically() {
+        let error = require_workdir_tool_broker(None).unwrap_err();
         assert!(matches!(
             error,
             ToolError::InvalidArgument(message)
-                if message.contains("requires an active Workdir session")
+                if message.contains("requires parent-owned Workdir tools")
         ));
     }
 
@@ -1096,6 +1100,7 @@ mod tests {
         let valid: SubWorkerSpawnInput = serde_json::from_value(serde_json::json!({
             "name":"reviewer","task":"review","profile":"builtin:reviewer",
             "scope":[{"target":"work","permission":"write"}],
+            "command":true,
             "review":{"ticket_id":"T1"}
         }))
         .unwrap();
@@ -1219,7 +1224,7 @@ 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 source_workdir_session = workdir::delegation_capable_session(Arc::new(
+        let workdir_tool_broker = workdir::WorkdirToolBroker::new(Arc::new(
             workdir::LocalWorkdirSession::materialized_bound(
                 workdir::Workdir::new("test-workdir"),
                 workspace_root.clone(),
@@ -1238,7 +1243,7 @@ enabled = false
             runtime.path().to_path_buf(),
             bash_output_dir.clone(),
             workspace_root.clone(),
-            Some(source_workdir_session),
+            Some(workdir_tool_broker),
             registry.clone(),
             manifest.clone(),
             prompt_loader,
@@ -1261,7 +1266,8 @@ enabled = false
                 "target": ".",
                 "permission": "write",
                 "recursive": true
-            }]
+            }],
+            "command": true
         });
 
         assert!(spawner_scope.snapshot().is_writable(&workspace_root));
@@ -1296,15 +1302,6 @@ enabled = false
         let record = registry
             .get_internal("reviewer-child")
             .expect("Internal reviewer registry record");
-        let child_bash_output_dir = bash_output_dir.join("sub-workers").join("reviewer-child");
-        record
-            .workdir_delegation
-            .scoped_session
-            .stat(workdir::StatRequest {
-                path: WorkdirPath::new_scoped(child_bash_output_dir.to_string_lossy()).unwrap(),
-            })
-            .await
-            .expect("local child retains read scope for its Bash output directory");
         for required in ["Read", "Write", "Edit", "Glob", "Grep", "Bash"] {
             assert!(
                 record.installed_tools.iter().any(|name| name == required),
@@ -1423,7 +1420,7 @@ enabled = false
             "Stopped terminal child must release its delegated Workdir session"
         );
         assert!(
-            !record.workdir_delegation.is_active(),
+            !record.workdir_tool_scope.is_active(),
             "stopped child must revoke cloned scoped sessions"
         );
         assert!(registry.get_internal("reviewer-child").is_some());
@@ -1478,7 +1475,7 @@ enabled = false
             Arc::new(AvailableWorkspaceClient),
         );
         let remote_client = Arc::new(StrictRemoteWorkdirWorkspaceClient::default());
-        let source_workdir_session = workdir::delegation_capable_session(
+        let workdir_tool_broker = workdir::WorkdirToolBroker::new(
             WorkspaceAttachedWorkdirSession::handle(remote_client.clone()),
         );
         let calls = Arc::new(AtomicUsize::new(0));
@@ -1493,7 +1490,7 @@ enabled = false
             runtime.path().to_path_buf(),
             bash_output_dir.clone(),
             workspace_root.clone(),
-            Some(source_workdir_session),
+            Some(workdir_tool_broker),
             registry.clone(),
             manifest,
             PromptCatalogSource::builtins_only(),
@@ -1533,51 +1530,12 @@ enabled = false
             record.session.wait_until_idle().await,
             crate::internal_worker::InternalWorkerSessionStatus::Idle
         );
+        assert!(record.installed_tools.iter().any(|tool| tool == "Write"));
+        assert!(!record.installed_tools.iter().any(|tool| tool == "Bash"));
         assert_eq!(calls.load(Ordering::SeqCst), 1);
-        assert_eq!(
-            remote_client
-                .foreign_scope_rejections
-                .load(Ordering::SeqCst),
-            0
-        );
-        let child_bash_output_dir = bash_output_dir.join("sub-workers").join("remote-child");
-        assert!(child_bash_output_dir.is_dir());
-        for required in ["Read", "Write", "Edit", "Glob", "Grep", "Bash"] {
-            assert!(
-                record.installed_tools.iter().any(|name| name == required),
-                "remote write-scoped child is missing {required}: {:?}",
-                record.installed_tools
-            );
-        }
-
-        let remote_requests = remote_client.requests();
-        let operate_requests = remote_requests
-            .iter()
-            .filter(|request| request.body.is_some())
-            .collect::<Vec<_>>();
-        assert_eq!(
-            operate_requests.len(),
-            1,
-            "remote requests: {remote_requests:?}"
-        );
-        let operation_body: serde_json::Value = serde_json::from_str(
-            operate_requests[0]
-                .body
-                .as_deref()
-                .expect("remote operation body"),
-        )
-        .unwrap();
-        let rules = operation_body["delegations"][0]["rules"]
-            .as_array()
-            .expect("delegation rules");
-        assert_eq!(rules.len(), 1, "remote operation body: {operation_body}");
-        assert_eq!(rules[0]["target"], "");
         assert!(
-            !operation_body.to_string().contains(
-                child_bash_output_dir
-                    .to_str()
-                    .expect("UTF-8 test output directory")
-            )
+            remote_client.requests().is_empty(),
+            "spawning a child must not open or delegate a provider Workdir session"
         );
     }
 
@@ -1589,6 +1547,7 @@ enabled = false
             .and_then(serde_json::Value::as_object)
             .expect("schema properties");
         assert!(properties.contains_key("cwd"), "schema: {schema}");
+        assert!(properties.contains_key("command"), "schema: {schema}");
         let required = schema
             .get("required")
             .and_then(serde_json::Value::as_array)
@@ -1718,7 +1677,6 @@ enabled = false
     #[derive(Debug, Default)]
     struct StrictRemoteWorkdirWorkspaceClient {
         requests: Mutex<Vec<WorkspaceRequest>>,
-        foreign_scope_rejections: AtomicUsize,
     }
 
     impl StrictRemoteWorkdirWorkspaceClient {
@@ -1750,59 +1708,10 @@ enabled = false
             self.requests
                 .lock()
                 .expect("remote Workdir request lock")
-                .push(request.clone());
-            if request.path.ends_with("/fence") {
-                return Ok(WorkspaceResponse {
-                    status: 200,
-                    body: serde_json::json!({ "value": "remote-fence-1" }).to_string(),
-                });
-            }
-
-            let body: serde_json::Value = serde_json::from_str(
-                request
-                    .body
-                    .as_deref()
-                    .ok_or_else(|| WorkspaceClientError::Request("missing request body".into()))?,
-            )
-            .map_err(|error| WorkspaceClientError::Request(error.to_string()))?;
-            let has_foreign_scope = body
-                .get("delegations")
-                .and_then(serde_json::Value::as_array)
-                .into_iter()
-                .flatten()
-                .flat_map(|delegation| {
-                    delegation
-                        .get("rules")
-                        .and_then(serde_json::Value::as_array)
-                        .into_iter()
-                        .flatten()
-                })
-                .filter_map(|rule| rule.get("target").and_then(serde_json::Value::as_str))
-                .any(|target| Path::new(target).is_absolute());
-            if has_foreign_scope {
-                self.foreign_scope_rejections.fetch_add(1, Ordering::SeqCst);
-                return Ok(WorkspaceResponse {
-                    status: 403,
-                    body: serde_json::json!({
-                        "code": "out_of_scope",
-                        "message": "Worker-host path is outside the remote Workdir namespace"
-                    })
-                    .to_string(),
-                });
-            }
-
-            Ok(WorkspaceResponse {
-                status: 200,
-                body: serde_json::json!({
-                    "operation": "stat",
-                    "result": {
-                        "path": "",
-                        "kind": "directory",
-                        "size": 0
-                    }
-                })
-                .to_string(),
-            })
+                .push(request);
+            Err(WorkspaceClientError::Request(
+                "SubWorker spawn must not call the remote Workdir provider".into(),
+            ))
         }
     }
 

crates/worker/tests/controller_test.rs

@@ -332,6 +332,7 @@ async fn shutdown_closes_bound_workdir_session() {
             command: "sleep 30".to_owned(),
             timeout_secs: 60,
             output_limit: 1024,
+            cwd: None,
             spill_dir: None,
             tool_call_id: None,
         })
@@ -376,6 +377,7 @@ async fn controller_projects_workdir_command_events_and_snapshot_state() {
             command: "printf ready; sleep 0.3; printf done".to_owned(),
             timeout_secs: 5,
             output_limit: 1024,
+            cwd: None,
             spill_dir: None,
             tool_call_id: Some("tool-command-1".into()),
         })
@@ -484,6 +486,7 @@ async fn controller_refreshes_command_snapshot_after_high_output_provider_lag()
                 .to_owned(),
             timeout_secs: 10,
             output_limit: 1024,
+            cwd: None,
             spill_dir: None,
             tool_call_id: Some("tool-high-output".into()),
         })
@@ -560,6 +563,7 @@ async fn controller_startup_failure_closes_bound_workdir_session() {
                 command: "printf unreachable".to_owned(),
                 timeout_secs: 5,
                 output_limit: 1024,
+                cwd: None,
                 spill_dir: None,
                 tool_call_id: None,
             })

crates/workspace-server/src/server.rs

@@ -48,8 +48,7 @@ use workdir::http::{
 };
 use workdir::workspace::{
     MaterializerKind, WorkingDirectoryCleanupTarget, WorkingDirectoryOccupancy,
-    WorkingDirectoryStatusKind, WorkingDirectorySummary, WorkspaceWorkdirSessionFence,
-    WorkspaceWorkdirSessionOperationRequest,
+    WorkingDirectoryStatusKind, WorkingDirectorySummary, WorkspaceWorkdirSessionOperationRequest,
 };
 use workdir::{CommandHandle, WorkdirSessionHandle};
 use worker::feature::builtin::{WorkerObservationSubject, WorkerObservationSubjectRef};
@@ -353,7 +352,6 @@ static EMBEDDED_RUNTIME_REQUEST_IDENTITY: std::sync::LazyLock<
 struct WorkdirCommandSession {
     source: WorkdirSessionHandle,
     provider_handle: CommandHandle,
-    delegations: Vec<workdir::WorkdirDelegationRequest>,
 }
 
 enum RegisteredWorkdirSession {
@@ -396,7 +394,6 @@ impl WorkdirSessionRegistry {
         worker: RuntimeWorkerRef,
         source: WorkdirSessionHandle,
         provider_handle: CommandHandle,
-        delegations: Vec<workdir::WorkdirDelegationRequest>,
     ) -> CommandHandle {
         let external_handle = loop {
             let candidate = CommandHandle(Uuid::now_v7().to_string());
@@ -412,7 +409,6 @@ impl WorkdirSessionRegistry {
             WorkdirCommandSession {
                 source,
                 provider_handle,
-                delegations,
             },
         );
         external_handle
@@ -2625,10 +2621,6 @@ fn build_inner_router(api: WorkspaceApi) -> Router {
             post(scoped_attach_current_worker_workdir)
                 .delete(scoped_detach_current_worker_workdir),
         )
-        .route(
-            "/api/w/{workspace_id}/workers/self/workdir-session/fence",
-            get(scoped_current_worker_workdir_session_fence),
-        )
         .route(
             "/api/w/{workspace_id}/workers/self/workdir-session/operations",
             post(scoped_execute_current_worker_workdir_operation),
@@ -7380,46 +7372,11 @@ async fn scoped_detach_current_worker_workdir(
     }))
 }
 
-async fn scoped_current_worker_workdir_session_fence(
-    State(api): State<WorkspaceApi>,
-    AxumPath(path): AxumPath<ScopedWorkspacePath>,
-    headers: HeaderMap,
-) -> ApiResult<Json<WorkspaceWorkdirSessionFence>> {
-    validate_workspace_scope(&api, &path.workspace_id)?;
-    let worker = current_worker_identity(&api, &path.workspace_id, &headers)?;
-    let session_lock = current_worker_session_lock(&api, &worker);
-    let _session_guard = session_lock.lock().await;
-    let link = current_worker_active_attachment(&api, &worker)?;
-    Ok(Json(WorkspaceWorkdirSessionFence {
-        value: current_worker_workdir_session_fence(&link),
-    }))
-}
-
-fn current_worker_workdir_session_fence(link: &WorkerWorkdirLinkRecord) -> String {
-    format!("v1:{}\0{}", link.workdir_id, link.linked_at)
-}
-
-fn validate_current_worker_workdir_session_fence(
-    link: &WorkerWorkdirLinkRecord,
-    expected: Option<&str>,
-) -> Result<()> {
-    if expected.is_some_and(|expected| expected != current_worker_workdir_session_fence(link)) {
-        Err(Error::WorkdirAttachmentConflict(
-            "delegated Workdir session attachment changed".to_string(),
-        ))
-    } else {
-        Ok(())
-    }
-}
-
 fn validated_current_worker_attachment(
     api: &WorkspaceApi,
     worker: &RuntimeWorkerRef,
-    expected_session_fence: Option<&str>,
 ) -> ApiResult<WorkerWorkdirLinkRecord> {
-    let link = current_worker_active_attachment(api, worker)?;
-    validate_current_worker_workdir_session_fence(&link, expected_session_fence)?;
-    Ok(link)
+    current_worker_active_attachment(api, worker)
 }
 
 #[derive(Debug)]
@@ -7474,23 +7431,13 @@ async fn scoped_execute_current_worker_workdir_operation(
 ) -> std::result::Result<Json<WorkdirSessionOperationResult>, WorkdirOperationApiError> {
     validate_workspace_scope(&api, &path.workspace_id)?;
     let worker = current_worker_identity(&api, &path.workspace_id, &headers)?;
-    let expected_session_fence = request.expected_session_fence;
-    let delegations = request.delegations;
     let result = match request.operation {
         WorkdirSessionOperation::CommandStart(command) => {
             let session_lock = current_worker_session_lock(&api, &worker);
             let _session_guard = session_lock.lock().await;
-            let link = validated_current_worker_attachment(
-                &api,
-                &worker,
-                expected_session_fence.as_deref(),
-            )?;
+            let link = validated_current_worker_attachment(&api, &worker)?;
             let source = open_current_worker_workdir_session_locked(&api, &worker, &link).await?;
-            let applied =
-                apply_current_worker_delegations(&worker, source.clone(), delegations.clone())
-                    .await?;
-            let provider_handle = applied
-                .scoped_session
+            let provider_handle = source
                 .start_command(command)
                 .await
                 .map_err(|error| current_worker_workdir_operation_error(&worker, error))?;
@@ -7509,58 +7456,32 @@ async fn scoped_execute_current_worker_workdir_operation(
                 .workdir_sessions
                 .lock()
                 .expect("Workdir session registry lock poisoned")
-                .register_command(
-                    worker.clone(),
-                    registered_source,
-                    provider_handle,
-                    delegations,
-                );
+                .register_command(worker.clone(), registered_source, provider_handle);
             WorkdirSessionOperationResult::CommandStart(external_handle)
         }
         WorkdirSessionOperation::CommandStatus(external_handle) => {
-            let (session, provider_handle) = current_worker_command_session(
-                &api,
-                &worker,
-                &external_handle,
-                &delegations,
-                expected_session_fence.as_deref(),
-            )
-            .await?;
+            let (session, provider_handle) =
+                current_worker_command_session(&api, &worker, &external_handle)?;
             session
-                .scoped_session
                 .command_status(provider_handle)
                 .await
                 .map(WorkdirSessionOperationResult::CommandStatus)
                 .map_err(|error| current_worker_workdir_operation_error(&worker, error))?
         }
         WorkdirSessionOperation::CommandOutput(mut output) => {
-            let (session, provider_handle) = current_worker_command_session(
-                &api,
-                &worker,
-                &output.handle,
-                &delegations,
-                expected_session_fence.as_deref(),
-            )
-            .await?;
+            let (session, provider_handle) =
+                current_worker_command_session(&api, &worker, &output.handle)?;
             output.handle = provider_handle;
             session
-                .scoped_session
                 .command_output(output)
                 .await
                 .map(WorkdirSessionOperationResult::CommandOutput)
                 .map_err(|error| current_worker_workdir_operation_error(&worker, error))?
         }
         WorkdirSessionOperation::CommandCancel(external_handle) => {
-            let (session, provider_handle) = current_worker_command_session(
-                &api,
-                &worker,
-                &external_handle,
-                &delegations,
-                expected_session_fence.as_deref(),
-            )
-            .await?;
+            let (session, provider_handle) =
+                current_worker_command_session(&api, &worker, &external_handle)?;
             session
-                .scoped_session
                 .cancel_command(provider_handle)
                 .await
                 .map(|()| WorkdirSessionOperationResult::CommandCancel)
@@ -7575,14 +7496,9 @@ async fn scoped_execute_current_worker_workdir_operation(
         | WorkdirSessionOperation::Grep(_)) => {
             let session_lock = current_worker_session_lock(&api, &worker);
             let _session_guard = session_lock.lock().await;
-            let link = validated_current_worker_attachment(
-                &api,
-                &worker,
-                expected_session_fence.as_deref(),
-            )?;
+            let link = validated_current_worker_attachment(&api, &worker)?;
             let source = open_current_worker_workdir_session_locked(&api, &worker, &link).await?;
-            let applied = apply_current_worker_delegations(&worker, source, delegations).await?;
-            execute_workdir_session_operation(&applied.scoped_session, operation)
+            execute_workdir_session_operation(&source, operation)
                 .await
                 .map_err(|error| current_worker_workdir_operation_error(&worker, error))?
         }
@@ -7590,29 +7506,12 @@ async fn scoped_execute_current_worker_workdir_operation(
     Ok(Json(result))
 }
 
-async fn apply_current_worker_delegations(
-    worker: &RuntimeWorkerRef,
-    source: WorkdirSessionHandle,
-    delegations: Vec<workdir::WorkdirDelegationRequest>,
-) -> Result<workdir::AppliedWorkdirDelegation> {
-    workdir::apply_delegation_chain(source, delegations)
-        .await
-        .map_err(|error| Error::RuntimeOperationFailed {
-            runtime_id: worker.runtime_id.clone(),
-            code: "workdir_session_delegation_failed".to_string(),
-            message: error.to_string(),
-        })
-}
-
-async fn current_worker_command_session(
+fn current_worker_command_session(
     api: &WorkspaceApi,
     worker: &RuntimeWorkerRef,
     external_handle: &CommandHandle,
-    delegations: &[workdir::WorkdirDelegationRequest],
-    expected_session_fence: Option<&str>,
-) -> std::result::Result<(workdir::AppliedWorkdirDelegation, CommandHandle), WorkdirOperationApiError>
-{
-    let _link = validated_current_worker_attachment(api, worker, expected_session_fence)?;
+) -> std::result::Result<(WorkdirSessionHandle, CommandHandle), WorkdirOperationApiError> {
+    let _link = validated_current_worker_attachment(api, worker)?;
     let command = api
         .workdir_sessions
         .lock()
@@ -7624,15 +7523,7 @@ async fn current_worker_command_session(
                 workdir::WorkdirError::UnknownCommand(external_handle.0.clone()),
             ))
         })?;
-    if command.delegations != delegations {
-        return Err(Error::WorkdirAttachmentConflict(
-            "command lifecycle delegation differs from CommandStart".to_string(),
-        )
-        .into());
-    }
-    let session =
-        apply_current_worker_delegations(worker, command.source, command.delegations).await?;
-    Ok((session, command.provider_handle))
+    Ok((command.source, command.provider_handle))
 }
 
 fn current_worker_workdir_operation_error(
@@ -16567,6 +16458,7 @@ mod tests {
                 command: "printf ready; sleep 30".to_string(),
                 timeout_secs: 60,
                 output_limit: 4096,
+                cwd: None,
                 spill_dir: None,
                 tool_call_id: Some("tool-call-command-session".to_string()),
             })
@@ -16576,12 +16468,8 @@ mod tests {
         let mut registry = WorkdirSessionRegistry::default();
         registry.insert_attachment(worker.clone(), source.clone());
         let registered_source = registry.remove_attachment(&worker).unwrap();
-        let external_handle = registry.register_command(
-            worker.clone(),
-            registered_source,
-            provider_handle.clone(),
-            Vec::new(),
-        );
+        let external_handle =
+            registry.register_command(worker.clone(), registered_source, provider_handle.clone());
         assert_ne!(external_handle, provider_handle);
 
         let refreshed: WorkdirSessionHandle = Arc::new(workdir::LocalWorkdirSession::new(
@@ -23356,30 +23244,6 @@ mod tests {
         assert_eq!(response.status(), StatusCode::BAD_REQUEST);
     }
 
-    #[test]
-    fn delegated_workdir_session_fence_rejects_reattached_link() {
-        let first = WorkerWorkdirLinkRecord {
-            workspace_id: "workspace-a".to_string(),
-            worker: workdir::workspace::RuntimeWorkerRef::new("runtime-a", "worker-a"),
-            workdir_id: "workdir-a".to_string(),
-            role: "primary".to_string(),
-            linked_at: "2026-01-01T00:00:00Z".to_string(),
-            unlinked_at: None,
-        };
-        let expected = current_worker_workdir_session_fence(&first);
-        assert!(validate_current_worker_workdir_session_fence(&first, None).is_ok());
-        assert!(validate_current_worker_workdir_session_fence(&first, Some(&expected)).is_ok());
-
-        let reattached = WorkerWorkdirLinkRecord {
-            linked_at: "2026-01-01T00:00:01Z".to_string(),
-            ..first
-        };
-        assert!(matches!(
-            validate_current_worker_workdir_session_fence(&reattached, Some(&expected)),
-            Err(Error::WorkdirAttachmentConflict(_))
-        ));
-    }
-
     #[tokio::test]
     async fn backend_workdir_session_proxy_executes_typed_operations() {
         use manifest::Scope;

resources/flows/coder-review.dcdl

@@ -15,7 +15,7 @@
         };
 
         review = {
-            instructions = "Use the current Ticket Merge Request as review authority. Call `ShowMergeRequest` and confirm its source selector resolves to exact committed implementation HEAD, then spawn one actual direct-child SubWorker with profile builtin:reviewer, write scope for Workdir inspection and command validation, and only the Ticket id in the structured review handoff. The trusted spawn layer records `ReviewRequested` with the exact source ref and injects review capability; do not place commit/ref identity, capability material, or a prewritten verdict in model input. The child must commit `ReviewMergeRequest`; prose output and Worker observation are not approval authority. After the structured result for the exact current source ref exists, request a Flow transition.";
+            instructions = "Use the current Ticket Merge Request as review authority. Call `ShowMergeRequest` and confirm its source selector resolves to exact committed implementation HEAD, then spawn one actual direct-child SubWorker with profile builtin:reviewer, write scope plus an explicit command grant for Workdir inspection and command validation, and only the Ticket id in the structured review handoff. The trusted spawn layer records `ReviewRequested` with the exact source ref and injects review capability; do not place commit/ref identity, capability material, or a prewritten verdict in model input. The child must commit `ReviewMergeRequest`; prose output and Worker observation are not approval authority. After the structured result for the exact current source ref exists, request a Flow transition.";
             transitions = {
                 approved = {
                     target = "complete";

resources/prompts/internal/sub_worker_spawn_tool_description.md

@@ -1,8 +1,8 @@
 Spawn a parent-owned Internal SubWorker session to split context for a delegated task. The parent Worker's write scope is reduced by the scope passed here; the Internal SubWorker starts running `task` immediately without creating a Runtime Worker record, OS process, PID, or Unix socket. It remains available for follow-up turns until explicitly stopped or its parent exits.
 
-Optional `cwd`: when provided, the spawned SubWorker's tool default working directory only. It must be an absolute existing directory covered by the child's delegated readable scope, and it does not change workspace/Profile/memory/Ticket roots or grant authority. `name` must be unique among this Worker's direct children.
+Optional `cwd`: when provided, the spawned SubWorker's tool default working directory only. It must be a Workdir-relative existing directory covered by the child's readable scope, and it does not change workspace/Profile/memory/Ticket roots or grant authority. `name` must be unique among this Worker's direct children.
 
-Profile selection: `profile` may be omitted or set to `default` to use the effective child default profile, set to `inherit` to derive reusable child configuration from this Worker, or set to one of the registry selectors below. Raw/path profile selectors are not accepted by SubWorkerSpawn. `scope` is always the only delegated filesystem capability; profile scope is replaced by the explicit SubWorkerSpawn scope.
+Profile selection: `profile` may be omitted or set to `default` to use the effective child default profile, set to `inherit` to derive reusable child configuration from this Worker, or set to one of the registry selectors below. Raw/path profile selectors are not accepted by SubWorkerSpawn. `scope` is the child's only filesystem capability and replaces profile scope. `command` is a separate explicit grant, defaults to false, and is accepted only with a writable scope; writable scope alone does not grant command execution.
 
 Default profile: {{ default_profile }}
 Special selector: inherit — derive reusable model/worker/tool policy from the spawner while replacing worker.name and scope.