feat: expose compaction as an internal worker

crates/protocol/src/lib.rs

@@ -281,11 +281,44 @@ impl Method {
 /// Presentation category for an Internal Worker exposed through its parent's
 /// protocol stream. Internal Workers never become independently addressable
 /// protocol subjects.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
 #[serde(rename_all = "snake_case")]
 pub enum InternalWorkerKind {
     SubWorker,
+    Service { kind: String },
+}
+
+/// Stable parent-owned lifecycle for one compaction run.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+pub struct CompactionLifecycle {
+    pub schema_version: u32,
+    pub compaction_id: String,
+    pub revision: u64,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub internal_worker: Option<InternalWorkerRef>,
+    pub state: CompactionLifecycleState,
+    /// Milliseconds since the Unix epoch.
+    pub started_at_ms: u64,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub ended_at_ms: Option<u64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub summary: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub error: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub new_segment_id: Option<String>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+#[serde(rename_all = "snake_case")]
+pub enum CompactionLifecycleState {
+    Running,
+    Done,
+    Failed,
+    Interrupted,
 }
 
 /// Stable presentation identity for one parent-owned Internal Worker session.
@@ -607,23 +640,18 @@ pub enum Event {
     /// This is not part of LLM history or prompt context; clients may display it
     /// briefly as operational status.
     MemoryWorker(MemoryWorkerEvent),
-    /// Worker has started compacting the current session.
-    ///
-    /// Fired immediately before a compaction run. Success is signalled by
-    /// `CompactDone` (with the new `SegmentId`); failure by `CompactFailed`.
-    /// Broadcast to all clients; not replayed to late subscribers.
-    CompactStart,
-    /// Compaction completed and the session was rotated.
-    ///
-    /// `new_segment_id` is the UUID of the freshly created session that
-    /// replaced the old history.
-    CompactDone {
-        #[cfg_attr(feature = "typescript", ts(type = "string"))]
-        new_segment_id: uuid::Uuid,
+    /// Worker has started compacting the current session, or bound the run to its
+    /// observable Internal Worker. Revisions upsert one stable lifecycle item.
+    CompactStart {
+        lifecycle: CompactionLifecycle,
     },
-    /// Compaction failed. The session is unchanged.
+    /// Compaction completed and the session was rotated.
+    CompactDone {
+        lifecycle: CompactionLifecycle,
+    },
+    /// Compaction failed or was cancelled. The session is unchanged.
     CompactFailed {
-        error: String,
+        lifecycle: CompactionLifecycle,
     },
     Shutdown,
 }
@@ -1732,45 +1760,74 @@ mod tests {
         assert_eq!(parsed["data"]["timestamp_ms"], 1_700_000_000_000i64);
     }
 
+    fn test_compaction_lifecycle(state: CompactionLifecycleState) -> CompactionLifecycle {
+        CompactionLifecycle {
+            schema_version: 2,
+            compaction_id: "0192f0e8-4d84-7d6e-a000-000000000000".into(),
+            revision: 1,
+            internal_worker: None,
+            state,
+            started_at_ms: 1_700_000_000_000,
+            ended_at_ms: None,
+            summary: None,
+            error: None,
+            new_segment_id: None,
+        }
+    }
+
     #[test]
     fn event_compact_start_roundtrip() {
-        let event = Event::CompactStart;
+        let event = Event::CompactStart {
+            lifecycle: test_compaction_lifecycle(CompactionLifecycleState::Running),
+        };
         let json = serde_json::to_string(&event).unwrap();
-        assert_eq!(json, r#"{"event":"compact_start"}"#);
+        let parsed: serde_json::Value = serde_json::from_str(&json).unwrap();
+        assert_eq!(parsed["event"], "compact_start");
+        assert_eq!(parsed["data"]["lifecycle"]["state"], "running");
         let decoded: Event = serde_json::from_str(&json).unwrap();
-        assert!(matches!(decoded, Event::CompactStart));
+        assert!(matches!(decoded, Event::CompactStart { lifecycle } if lifecycle.revision == 1));
     }
 
     #[test]
     fn event_compact_done_roundtrip() {
         let id = uuid::Uuid::parse_str("0192f0e8-4d84-7d6e-a000-000000000001").unwrap();
-        let event = Event::CompactDone { new_segment_id: id };
+        let mut lifecycle = test_compaction_lifecycle(CompactionLifecycleState::Done);
+        lifecycle.new_segment_id = Some(id.to_string());
+        lifecycle.summary = Some("accepted summary".into());
+        let event = Event::CompactDone { lifecycle };
         let json = serde_json::to_string(&event).unwrap();
         let parsed: serde_json::Value = serde_json::from_str(&json).unwrap();
         assert_eq!(parsed["event"], "compact_done");
         assert_eq!(
-            parsed["data"]["new_segment_id"],
+            parsed["data"]["lifecycle"]["new_segment_id"],
             "0192f0e8-4d84-7d6e-a000-000000000001"
         );
         let decoded: Event = serde_json::from_str(&json).unwrap();
         match decoded {
-            Event::CompactDone { new_segment_id } => assert_eq!(new_segment_id, id),
+            Event::CompactDone { lifecycle } => {
+                assert_eq!(
+                    lifecycle.new_segment_id.as_deref(),
+                    Some(id.to_string().as_str())
+                )
+            }
             other => panic!("expected CompactDone, got {other:?}"),
         }
     }
 
     #[test]
     fn event_compact_failed_roundtrip() {
-        let event = Event::CompactFailed {
-            error: "provider 429".into(),
-        };
+        let mut lifecycle = test_compaction_lifecycle(CompactionLifecycleState::Failed);
+        lifecycle.error = Some("provider 429".into());
+        let event = Event::CompactFailed { lifecycle };
         let json = serde_json::to_string(&event).unwrap();
         let parsed: serde_json::Value = serde_json::from_str(&json).unwrap();
         assert_eq!(parsed["event"], "compact_failed");
-        assert_eq!(parsed["data"]["error"], "provider 429");
+        assert_eq!(parsed["data"]["lifecycle"]["error"], "provider 429");
         let decoded: Event = serde_json::from_str(&json).unwrap();
         match decoded {
-            Event::CompactFailed { error } => assert_eq!(error, "provider 429"),
+            Event::CompactFailed { lifecycle } => {
+                assert_eq!(lifecycle.error.as_deref(), Some("provider 429"))
+            }
             other => panic!("expected CompactFailed, got {other:?}"),
         }
     }

crates/protocol/src/typescript.rs

@@ -4,11 +4,11 @@ use ts_rs::{Config, TS};
 
 use crate::{
     Alert, AlertLevel, AlertSource, CommandEvent, CommandSnapshot, CommandStatus, CommandStream,
-    CommandStreamSlice, CompletionEntry, CompletionKind, ErrorCode, Event, Greeting, InFlightBlock,
-    InFlightSnapshot, InFlightToolCallState, InternalWorkerKind, InternalWorkerRef,
-    InternalWorkerSnapshot, InvokeKind, MemoryWorkerEvent, Method, Permission, RewindSummary,
-    RewindTarget, RewindTargetId, RunResult, ScopeRule, Segment, TurnResult, WorkerEvent,
-    WorkerStatus,
+    CommandStreamSlice, CompactionLifecycle, CompactionLifecycleState, CompletionEntry,
+    CompletionKind, ErrorCode, Event, Greeting, InFlightBlock, InFlightSnapshot,
+    InFlightToolCallState, InternalWorkerKind, InternalWorkerRef, InternalWorkerSnapshot,
+    InvokeKind, MemoryWorkerEvent, Method, Permission, RewindSummary, RewindTarget, RewindTargetId,
+    RunResult, ScopeRule, Segment, TurnResult, WorkerEvent, WorkerStatus,
     subscription::{
         EventSubscriptionSelector, SubscriptionEvent, SubscriptionEventPayload, SubscriptionFrame,
         SubscriptionFramePayload, SubscriptionId, SubscriptionRejectionCode, SubscriptionRequest,
@@ -53,6 +53,8 @@ pub fn generated_protocol_types() -> String {
     push_decl::<CommandStreamSlice>(&cfg, &mut output);
     push_decl::<CommandSnapshot>(&cfg, &mut output);
     push_decl::<CommandEvent>(&cfg, &mut output);
+    push_decl::<CompactionLifecycleState>(&cfg, &mut output);
+    push_decl::<CompactionLifecycle>(&cfg, &mut output);
     push_decl::<ScopeRule>(&cfg, &mut output);
     push_decl::<CompletionEntry>(&cfg, &mut output);
     push_decl::<RewindTargetId>(&cfg, &mut output);

crates/tui/src/app.rs

@@ -1342,13 +1342,20 @@ impl App {
                     }
                 }
             }
-            Event::CompactStart => {
-                self.blocks.push(Block::Compact(CompactEvent::Streaming {
-                    started_at: Instant::now(),
-                }));
+            Event::CompactStart { .. } => {
+                if self.last_streaming_compact_mut().is_none() {
+                    self.blocks.push(Block::Compact(CompactEvent::Streaming {
+                        started_at: Instant::now(),
+                    }));
+                }
             }
-            Event::CompactDone { new_segment_id } => {
+            Event::CompactDone { lifecycle } => {
                 self.session_context_tokens = 0;
+                let new_segment_id = lifecycle
+                    .new_segment_id
+                    .as_deref()
+                    .and_then(|value| uuid::Uuid::parse_str(value).ok())
+                    .unwrap_or_default();
                 if let Some(evt) = self.last_streaming_compact_mut() {
                     let elapsed_secs = match evt {
                         CompactEvent::Streaming { started_at } => {
@@ -1367,7 +1374,10 @@ impl App {
                     }));
                 }
             }
-            Event::CompactFailed { error } => {
+            Event::CompactFailed { lifecycle } => {
+                let error = lifecycle
+                    .error
+                    .unwrap_or_else(|| "compaction failed".to_string());
                 if let Some(evt) = self.last_streaming_compact_mut() {
                     let elapsed_secs = match evt {
                         CompactEvent::Streaming { started_at } => {
@@ -2486,7 +2496,7 @@ fn event_is_stale_after_rewind(event: &Event) -> bool {
         event,
         Event::Alert(_)
             | Event::MemoryWorker(_)
-            | Event::CompactStart
+            | Event::CompactStart { .. }
             | Event::CompactDone { .. }
             | Event::CompactFailed { .. }
             | Event::SegmentRotated { .. }
@@ -4076,13 +4086,34 @@ mod completion_flow_tests {
         }
     }
 
+    fn test_compaction_lifecycle(
+        state: protocol::CompactionLifecycleState,
+    ) -> protocol::CompactionLifecycle {
+        protocol::CompactionLifecycle {
+            schema_version: 2,
+            compaction_id: "compaction-test".into(),
+            revision: 1,
+            internal_worker: None,
+            state,
+            started_at_ms: 1,
+            ended_at_ms: None,
+            summary: None,
+            error: None,
+            new_segment_id: None,
+        }
+    }
+
     #[test]
     fn compact_done_replaces_live_block() {
         let mut app = App::new("test".into());
         let id = uuid::Uuid::parse_str("12345678-1234-5678-1234-567812345678").unwrap();
 
-        app.handle_worker_event(Event::CompactStart);
-        app.handle_worker_event(Event::CompactDone { new_segment_id: id });
+        app.handle_worker_event(Event::CompactStart {
+            lifecycle: test_compaction_lifecycle(protocol::CompactionLifecycleState::Running),
+        });
+        let mut lifecycle = test_compaction_lifecycle(protocol::CompactionLifecycleState::Done);
+        lifecycle.new_segment_id = Some(id.to_string());
+        app.handle_worker_event(Event::CompactDone { lifecycle });
 
         assert_eq!(compact_block_count(&app), 1);
         assert!(matches!(
@@ -4098,10 +4129,12 @@ mod completion_flow_tests {
     fn compact_failed_replaces_live_block() {
         let mut app = App::new("test".into());
 
-        app.handle_worker_event(Event::CompactStart);
-        app.handle_worker_event(Event::CompactFailed {
-            error: "provider 429".into(),
+        app.handle_worker_event(Event::CompactStart {
+            lifecycle: test_compaction_lifecycle(protocol::CompactionLifecycleState::Running),
         });
+        let mut lifecycle = test_compaction_lifecycle(protocol::CompactionLifecycleState::Failed);
+        lifecycle.error = Some("provider 429".into());
+        app.handle_worker_event(Event::CompactFailed { lifecycle });
 
         assert_eq!(compact_block_count(&app), 1);
         assert!(matches!(
@@ -4117,7 +4150,9 @@ mod completion_flow_tests {
     fn shutdown_marks_live_compact_incomplete() {
         let mut app = App::new("test".into());
 
-        app.handle_worker_event(Event::CompactStart);
+        app.handle_worker_event(Event::CompactStart {
+            lifecycle: test_compaction_lifecycle(protocol::CompactionLifecycleState::Running),
+        });
         app.handle_worker_event(Event::Shutdown);
 
         assert!(app.quit);
@@ -4208,9 +4243,9 @@ mod completion_flow_tests {
         let mut app = App::new("test".into());
         app.session_context_tokens = 42_000;
 
-        app.handle_worker_event(Event::CompactDone {
-            new_segment_id: uuid::Uuid::nil(),
-        });
+        let mut lifecycle = test_compaction_lifecycle(protocol::CompactionLifecycleState::Done);
+        lifecycle.new_segment_id = Some(uuid::Uuid::nil().to_string());
+        app.handle_worker_event(Event::CompactDone { lifecycle });
 
         assert_eq!(app.session_context_tokens, 0);
     }

crates/worker/src/compact/worker.rs

@@ -31,12 +31,11 @@ use workdir::LocalWorkdirSession;
 use workdir::{ReadRequest, WorkdirPath, WorkdirSessionHandle};
 
 use crate::compact::usage_tracker::UsageTracker;
-use crate::fs_view::ReadRequirement;
-#[cfg(test)]
-use crate::fs_view::slice_lines;
-use crate::session_capture::{
-    ReadDetail, ReadOptions, ReadSelector, SearchOptions, SessionCapture, ToolPart,
+use crate::feature::{
+    FeatureDescriptor, FeatureInstallContext, FeatureInstallError, FeatureModule, ToolContribution,
+    ToolDeclaration,
 };
+use crate::fs_view::ReadRequirement;
 
 /// Aggregated output of a compact worker run.
 #[derive(Debug, Default, Clone)]
@@ -91,248 +90,19 @@ struct SummaryParams {
     pub text: String,
 }
 
-/// Input to `search_session_log`.
-#[derive(Debug, Deserialize, schemars::JsonSchema)]
-struct SearchSessionParams {
-    /// Case-insensitive substring to search in compact-target history.
-    pub query: String,
-    /// 0-based item offset to start searching from.
-    #[serde(default)]
-    pub offset: Option<usize>,
-    /// Maximum number of hits to return.
-    #[serde(default)]
-    pub limit: Option<usize>,
-}
-
-/// Input to `read_session_items`.
-#[derive(Debug, Deserialize, schemars::JsonSchema)]
-struct ReadSessionParams {
-    /// 0-based compact-target history item offset.
-    pub offset: usize,
-    /// Maximum number of items to return.
-    pub limit: usize,
-    /// `compact` omits tool arguments/full results; `full` includes message text and tool result content.
-    #[serde(default = "default_session_read_mode")]
-    pub mode: String,
-}
-
-fn default_session_read_mode() -> String {
-    "compact".to_string()
-}
-
-const SESSION_TOOL_MAX_OUTPUT_TOKENS: u64 = 12_000;
-const SESSION_SEARCH_MAX_RESULTS: usize = 50;
-const SESSION_READ_MAX_ITEMS: usize = 80;
-
 const MARK_DESCRIPTION: &str = "Inject a file's contents into the compacted context so the \
 next session starts with it already read. Use this for files the next task needs in full. \
 Optionally specify `offset` (0-based line) and `limit` (line count) to inject only a slice. \
-Counts against `auto_read_budget`; overflow returns an error and the mark is not recorded. \
-Paths must be absolute.";
+Counts against `auto_read_budget`; overflow returns an error and the mark is not recorded.";
 
-const REFERENCE_DESCRIPTION: &str = "Record a file path as a named reference in the compacted \
-context without injecting its contents. Use for files that are contextually relevant but \
-whose current content the next session can fetch on demand.";
+const REFERENCE_DESCRIPTION: &str = "Record a Workdir-relative file path as a named reference in \
+the compacted context without injecting its contents. Use for files that are contextually \
+relevant but whose current content the next session can fetch on demand.";
 
 const SUMMARY_DESCRIPTION: &str = "Provide the final structured summary text. Subsequent calls \
 replace the previous content; only the last call is used. Must be called before the compact run \
 ends or compaction fails.";
 
-const SEARCH_SESSION_DESCRIPTION: &str = "Search the compact-target session history by \
-case-insensitive substring. Returns item indexes and compact snippets. Use this when the initial \
-overview is not enough to identify which part of the session matters. Results are bounded; narrow \
-the query if important details are omitted.";
-
-const READ_SESSION_DESCRIPTION: &str = "Read a bounded range of compact-target session history \
-items by 0-based index. mode='compact' omits tool arguments, full tool results, and reasoning \
-bodies; mode='full' includes message text and tool result content but still remains bounded. Use \
-this to verify details before writing the summary.";
-
-struct SessionLogToolState {
-    items: Arc<Vec<Item>>,
-    view: SessionCapture,
-}
-
-struct SearchSessionLogTool {
-    state: Arc<SessionLogToolState>,
-}
-
-#[async_trait]
-impl Tool for SearchSessionLogTool {
-    async fn execute(
-        &self,
-        input_json: &str,
-        _ctx: agen::tool::ToolExecutionContext,
-    ) -> Result<ToolOutput, ToolError> {
-        let params: SearchSessionParams = serde_json::from_str(input_json).map_err(|e| {
-            ToolError::InvalidArgument(format!("invalid search_session_log input: {e}"))
-        })?;
-        let query = params.query.trim().to_lowercase();
-        if query.is_empty() {
-            return Err(ToolError::InvalidArgument(
-                "search_session_log query must not be empty".to_string(),
-            ));
-        }
-        let offset = params.offset.unwrap_or(0);
-        let limit = params
-            .limit
-            .unwrap_or(20)
-            .clamp(1, SESSION_SEARCH_MAX_RESULTS);
-        let hits = self.state.view.search(&SearchOptions {
-            query: params.query.clone(),
-            kind: None,
-            tool_part: None,
-            tool_name: None,
-            limit: Some(limit),
-            min_entry_index: Some(offset as u64),
-            from: None,
-            through: None,
-            offset: 0,
-        });
-        let blocks = hits
-            .iter()
-            .map(|hit| {
-                let part = hit
-                    .tool_part
-                    .map(|part| format!(" {part:?}"))
-                    .unwrap_or_default();
-                let tool = hit
-                    .tool_name
-                    .as_ref()
-                    .map(|name| format!(" {name}"))
-                    .unwrap_or_default();
-                format!(
-                    "[{} {}{}{} {:?}] {}\n{}",
-                    hit.id,
-                    hit.kind.as_str(),
-                    part,
-                    tool,
-                    hit.entry_range,
-                    hit.label,
-                    hit.summary
-                )
-            })
-            .collect::<Vec<_>>();
-        let mut content = blocks.join("\n\n");
-        let truncated = truncate_to_token_budget(&mut content, SESSION_TOOL_MAX_OUTPUT_TOKENS);
-        let summary = if hits.is_empty() {
-            format!("No session log hits for {query:?} from item offset {offset}.")
-        } else if truncated {
-            format!(
-                "Found {} session log hit(s) for {query:?}; output truncated. Narrow the query.",
-                hits.len()
-            )
-        } else {
-            format!("Found {} session log hit(s) for {query:?}.", hits.len())
-        };
-        Ok(ToolOutput {
-            summary,
-            content: (!content.is_empty()).then_some(content),
-
-            attachments: Vec::new(),
-        })
-    }
-}
-
-struct ReadSessionItemsTool {
-    state: Arc<SessionLogToolState>,
-}
-
-#[async_trait]
-impl Tool for ReadSessionItemsTool {
-    async fn execute(
-        &self,
-        input_json: &str,
-        _ctx: agen::tool::ToolExecutionContext,
-    ) -> Result<ToolOutput, ToolError> {
-        let params: ReadSessionParams = serde_json::from_str(input_json).map_err(|e| {
-            ToolError::InvalidArgument(format!("invalid read_session_items input: {e}"))
-        })?;
-        let mode = SessionReadMode::parse(&params.mode)?;
-        let offset = params.offset.min(self.state.items.len());
-        let limit = params.limit.clamp(1, SESSION_READ_MAX_ITEMS);
-        let end = offset.saturating_add(limit).min(self.state.items.len());
-        let detail = match mode {
-            SessionReadMode::Compact => ReadDetail::Compact,
-            SessionReadMode::Full => ReadDetail::Full,
-        };
-        let read = if offset >= end {
-            crate::session_capture::ReadResult {
-                entries: Vec::new(),
-                truncated: false,
-            }
-        } else {
-            self.state.view.read(
-                ReadSelector::EntryRange([offset as u64, end.saturating_sub(1) as u64]),
-                ReadOptions {
-                    include_tools: true,
-                    tool_part: ToolPart::Both,
-                    detail,
-                    max_items: limit,
-                    max_bytes: 48 * 1024,
-                },
-            )
-        };
-        let mut content = read
-            .entries
-            .iter()
-            .map(|entry| entry.text.clone())
-            .collect::<Vec<_>>()
-            .join("\n\n");
-        let token_truncated =
-            truncate_to_token_budget(&mut content, SESSION_TOOL_MAX_OUTPUT_TOKENS);
-        let truncated = read.truncated || token_truncated;
-        let summary = if truncated {
-            format!(
-                "Read session items {offset}..{end} in {mode:?} mode; output truncated. Narrow the range."
-            )
-        } else {
-            format!("Read session items {offset}..{end} in {mode:?} mode.")
-        };
-        Ok(ToolOutput {
-            summary,
-            content: (!content.is_empty()).then_some(content),
-
-            attachments: Vec::new(),
-        })
-    }
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-enum SessionReadMode {
-    Compact,
-    Full,
-}
-
-impl SessionReadMode {
-    fn parse(value: &str) -> Result<Self, ToolError> {
-        match value {
-            "compact" => Ok(Self::Compact),
-            "full" => Ok(Self::Full),
-            other => Err(ToolError::InvalidArgument(format!(
-                "invalid read_session_items mode {other:?}; expected 'compact' or 'full'"
-            ))),
-        }
-    }
-}
-
-fn truncate_to_token_budget(text: &mut String, max_tokens: u64) -> bool {
-    let max_bytes = max_tokens.saturating_mul(4) as usize;
-    if text.len() <= max_bytes {
-        return false;
-    }
-    let mut cut = 0;
-    for (idx, _) in text.char_indices() {
-        if idx > max_bytes {
-            break;
-        }
-        cut = idx;
-    }
-    text.truncate(cut);
-    text.push_str("\n… [session tool output truncated]");
-    true
-}
-
 struct MarkReadRequiredTool {
     session: WorkdirSessionHandle,
     ctx: Arc<Mutex<CompactWorkerContext>>,
@@ -508,36 +278,63 @@ pub(crate) fn write_summary_tool(ctx: Arc<Mutex<CompactWorkerContext>>) -> ToolD
     })
 }
 
-pub(crate) fn search_session_log_tool(items: Arc<Vec<Item>>) -> ToolDefinition {
-    let view = SessionCapture::new("compact-target", (*items).clone());
-    let state = Arc::new(SessionLogToolState { items, view });
-    Arc::new(move || {
-        let schema = schemars::schema_for!(SearchSessionParams);
-        let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
-        let meta = ToolMeta::new("search_session_log")
-            .description(SEARCH_SESSION_DESCRIPTION)
-            .input_schema(schema_value);
-        let tool: Arc<dyn Tool> = Arc::new(SearchSessionLogTool {
-            state: state.clone(),
-        });
-        (meta, tool)
-    })
+#[derive(Clone)]
+pub(crate) struct CompactionOutputFeature {
+    session: Option<WorkdirSessionHandle>,
+    tracker: tools::Tracker,
+    context: Arc<Mutex<CompactWorkerContext>>,
 }
 
-pub(crate) fn read_session_items_tool(items: Arc<Vec<Item>>) -> ToolDefinition {
-    let view = SessionCapture::new("compact-target", (*items).clone());
-    let state = Arc::new(SessionLogToolState { items, view });
-    Arc::new(move || {
-        let schema = schemars::schema_for!(ReadSessionParams);
-        let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
-        let meta = ToolMeta::new("read_session_items")
-            .description(READ_SESSION_DESCRIPTION)
-            .input_schema(schema_value);
-        let tool: Arc<dyn Tool> = Arc::new(ReadSessionItemsTool {
-            state: state.clone(),
-        });
-        (meta, tool)
-    })
+impl CompactionOutputFeature {
+    pub(crate) fn new(
+        session: Option<WorkdirSessionHandle>,
+        tracker: tools::Tracker,
+        context: Arc<Mutex<CompactWorkerContext>>,
+    ) -> Self {
+        Self {
+            session,
+            tracker,
+            context,
+        }
+    }
+}
+
+impl FeatureModule for CompactionOutputFeature {
+    fn descriptor(&self) -> FeatureDescriptor {
+        let descriptor = FeatureDescriptor::builtin("compaction-output", "Compaction Output")
+            .with_description("Read-only Workdir access and bounded compaction output decisions.")
+            .with_tool(ToolDeclaration::new("add_reference", REFERENCE_DESCRIPTION))
+            .with_tool(ToolDeclaration::new("write_summary", SUMMARY_DESCRIPTION));
+        if self.session.is_some() {
+            descriptor
+                .with_tool(ToolDeclaration::new("Read", "Read a Workdir file."))
+                .with_tool(ToolDeclaration::new("mark_read_required", MARK_DESCRIPTION))
+        } else {
+            descriptor
+        }
+    }
+
+    fn install(&self, context: &mut FeatureInstallContext<'_>) -> Result<(), FeatureInstallError> {
+        if let Some(session) = &self.session {
+            context.tools().register(ToolContribution::new(
+                "Read",
+                tools::read_tool(session.clone(), self.tracker.clone()),
+            ))?;
+            context.tools().register(ToolContribution::new(
+                "mark_read_required",
+                mark_read_required_tool(session.clone(), self.context.clone()),
+            ))?;
+        }
+        context.tools().register(ToolContribution::new(
+            "add_reference",
+            add_reference_tool(self.context.clone()),
+        ))?;
+        context.tools().register(ToolContribution::new(
+            "write_summary",
+            write_summary_tool(self.context.clone()),
+        ))?;
+        Ok(())
+    }
 }
 
 /// Interceptor that monitors compact-worker context occupancy.
@@ -810,53 +607,4 @@ mod tests {
         assert_eq!(guard.references.len(), 1);
         assert_eq!(guard.references[0], PathBuf::from(p));
     }
-
-    #[tokio::test]
-    async fn search_session_log_returns_bounded_hits_without_full_tool_content() {
-        let items = Arc::new(vec![
-            Item::user_message("investigate compact failure"),
-            Item::tool_result_with_content(
-                "call-1",
-                "read trace with compact failure",
-                "very large raw trace body with secret detail",
-            ),
-        ]);
-        let view = SessionCapture::new("test", (*items).clone());
-        let tool: Arc<dyn Tool> = Arc::new(SearchSessionLogTool {
-            state: Arc::new(SessionLogToolState { items, view }),
-        });
-        let input = serde_json::json!({ "query": "compact", "limit": 10 }).to_string();
-        let out = tool.execute(&input, Default::default()).await.unwrap();
-        let content = out.content.unwrap();
-
-        assert!(content.contains("investigate compact failure"));
-        assert!(content.contains("read trace with compact failure"));
-        assert!(!content.contains("secret detail"));
-    }
-
-    #[tokio::test]
-    async fn read_session_items_full_mode_can_read_tool_result_content() {
-        let items = Arc::new(vec![Item::tool_result_with_content(
-            "call-1",
-            "read trace",
-            "raw trace detail",
-        )]);
-        let view = SessionCapture::new("test", (*items).clone());
-        let tool: Arc<dyn Tool> = Arc::new(ReadSessionItemsTool {
-            state: Arc::new(SessionLogToolState { items, view }),
-        });
-        let input = serde_json::json!({ "offset": 0, "limit": 1, "mode": "full" }).to_string();
-        let out = tool.execute(&input, Default::default()).await.unwrap();
-        let content = out.content.unwrap();
-
-        assert!(content.contains("raw trace detail"));
-    }
-
-    #[test]
-    fn slice_lines_handles_offset_and_limit() {
-        let text = "a\nb\nc\nd";
-        assert_eq!(slice_lines(text, 0, None), "a\nb\nc\nd");
-        assert_eq!(slice_lines(text, 1, Some(2)), "b\nc");
-        assert_eq!(slice_lines(text, 10, None), "");
-    }
 }

crates/worker/src/controller.rs

@@ -383,6 +383,7 @@ impl WorkerController {
         worker.attach_alerter(alerter.clone());
         // Also hand the raw broadcast sender so Worker-internal operations
         // can emit typed lifecycle `Event`s (currently: compact progress).
+        worker.attach_internal_worker_registry(spawned_registry.clone());
         worker.attach_event_tx(event_tx.clone());
 
         // Bash spills long outputs to a per-worker subdir under the runtime
@@ -421,7 +422,6 @@ impl WorkerController {
         wire_event_bridges_on_engine(&mut worker, &event_tx, &alerter, &in_flight);
 
         // === 3. Tool registration (builtin / memory / spawn-orchestration) ===
-        spawned_registry.attach_parent_protocol(event_tx.clone(), worker.session_id().to_string());
         let fs_for_view = register_worker_tools(
             &mut worker,
             bash_output_dir,

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

@@ -560,6 +560,7 @@ where
                 attempt.instance_id, attempt.checked_state_revision
             )),
             max_turns: Some(12),
+            engine_configurator: None,
             features,
             required_tools: &[
                 "ShowOverview",
@@ -571,6 +572,7 @@ where
                 workspace: WorkerWorkspaceContext::no_workspace(),
                 filesystem: WorkerFilesystemAuthority::None,
                 scope: Scope::empty(),
+                workdir_session: None,
             },
         };
         match run_internal_worker(spec).await {

crates/worker/src/internal_worker.rs

@@ -43,6 +43,8 @@ pub(crate) struct InternalWorkerAuthority {
     pub workspace: WorkerWorkspaceContext,
     pub filesystem: WorkerFilesystemAuthority,
     pub scope: Scope,
+    /// Provider-bound session inherited in an attenuated form from the owner.
+    pub workdir_session: Option<workdir::WorkdirSessionHandle>,
 }
 
 pub(crate) struct InternalWorkerSpec {
@@ -53,6 +55,7 @@ pub(crate) struct InternalWorkerSpec {
     pub input: String,
     pub cache_key: Option<String>,
     pub max_turns: Option<u32>,
+    pub engine_configurator: Option<Box<dyn FnOnce(&mut Engine<Box<dyn LlmClient>>) + Send>>,
     pub features: FeatureRegistryBuilder,
     pub required_tools: &'static [&'static str],
     pub authority: InternalWorkerAuthority,
@@ -102,6 +105,7 @@ where
         input,
         cache_key,
         max_turns,
+        engine_configurator,
         features,
         required_tools,
         authority,
@@ -128,7 +132,11 @@ where
     });
     engine.set_cache_key(cache_key);
     engine.set_max_turns(max_turns);
+    if let Some(configure) = engine_configurator {
+        configure(&mut engine);
+    }
     let store = EphemeralSessionStore::default();
+    let inherited_workdir_session = authority.workdir_session.clone();
     let mut worker = Worker::new(
         manifest,
         engine,
@@ -144,6 +152,9 @@ where
         identity: identity.clone(),
         history_entries: 0,
     })?;
+    if let Some(session) = inherited_workdir_session {
+        worker.bind_workdir_session(Some(session));
+    }
 
     let install_report = worker.install_features(features);
     let installed_tools = install_report.installed_tool_names();
@@ -250,7 +261,6 @@ impl InternalWorkerSessionStatus {
 
 #[derive(Debug, thiserror::Error)]
 pub(crate) enum InternalWorkerSessionError {
-    #[cfg(test)]
     #[error("failed to build internal Worker session: {message}")]
     Build { message: String },
     #[error("internal Worker session is busy")]
@@ -410,7 +420,6 @@ impl InternalWorkerSessionHandle {
         Ok(())
     }
 
-    #[cfg(test)]
     pub(crate) async fn wait_until_idle(&self) -> InternalWorkerSessionStatus {
         loop {
             let notified = self.state_changed.notified();
@@ -475,6 +484,7 @@ pub(crate) async fn spawn_internal_worker_session(
         input,
         cache_key,
         max_turns,
+        engine_configurator,
         features,
         required_tools,
         authority,
@@ -492,7 +502,11 @@ pub(crate) async fn spawn_internal_worker_session(
     });
     engine.set_cache_key(cache_key);
     engine.set_max_turns(max_turns);
+    if let Some(configure) = engine_configurator {
+        configure(&mut engine);
+    }
     let store = EphemeralSessionStore::default();
+    let inherited_workdir_session = authority.workdir_session.clone();
     let mut worker = Worker::new(
         manifest,
         engine,
@@ -505,6 +519,9 @@ pub(crate) async fn spawn_internal_worker_session(
     .map_err(|source| InternalWorkerSessionError::Build {
         message: source.to_string(),
     })?;
+    if let Some(session) = inherited_workdir_session {
+        worker.bind_workdir_session(Some(session));
+    }
     let install_report = worker.install_features(features);
     let installed_tools = install_report.installed_tool_names();
     let install_failed = install_report
@@ -539,6 +556,102 @@ pub(crate) async fn spawn_internal_worker_session(
     spawn_prepared_internal_worker_session(worker, store, input, None).await
 }
 
+/// Prepare an observable Internal Worker from the same bounded spec as one-shot
+/// helpers, but do not start its first turn. The owner must register the returned
+/// handle before calling `send`, preserving the snapshot/live boundary.
+pub(crate) fn prepare_internal_worker_from_spec(
+    spec: InternalWorkerSpec,
+    visibility: InternalWorkerVisibility,
+) -> std::pin::Pin<
+    Box<
+        dyn std::future::Future<
+                Output = Result<InternalWorkerSessionHandle, InternalWorkerSessionError>,
+            > + Send,
+    >,
+> {
+    Box::pin(async move {
+        let InternalWorkerSpec {
+            identity,
+            mut manifest,
+            client,
+            system_prompt,
+            input: _,
+            cache_key,
+            max_turns,
+            engine_configurator,
+            features,
+            required_tools,
+            authority,
+        } = spec;
+        manifest.worker.name = format!("internal-{}-{}", identity.kind, identity.run_id);
+        manifest.feature = Default::default();
+        manifest.plugins = Default::default();
+        manifest.mcp = Default::default();
+        manifest.skills = None;
+        manifest.compaction = None;
+        manifest.memory = None;
+
+        let mut engine = Engine::new(client).system_prompt(system_prompt);
+        engine.set_cache_key(cache_key);
+        engine.set_max_turns(max_turns);
+        if let Some(configure) = engine_configurator {
+            configure(&mut engine);
+        }
+        let store = EphemeralSessionStore::default();
+        let inherited_workdir_session = authority.workdir_session.clone();
+        let mut worker = Worker::new(
+            manifest,
+            engine,
+            store.clone(),
+            authority.workspace,
+            authority.filesystem,
+            authority.scope,
+        )
+        .await
+        .map_err(|source| InternalWorkerSessionError::Build {
+            message: source.to_string(),
+        })?;
+        if let Some(session) = inherited_workdir_session {
+            worker.bind_workdir_session(Some(session));
+        }
+        let install_report = worker.install_features(features);
+        let installed_tools = install_report.installed_tool_names();
+        let install_failed = install_report
+            .reports
+            .iter()
+            .any(|report| !report.installed);
+        let missing = required_tools
+            .iter()
+            .filter(|required| {
+                !installed_tools
+                    .iter()
+                    .any(|installed| installed == **required)
+            })
+            .copied()
+            .collect::<Vec<_>>();
+        if install_failed || !missing.is_empty() {
+            let diagnostics = install_report
+                .reports
+                .iter()
+                .flat_map(|report| report.diagnostics.iter())
+                .map(|diagnostic| diagnostic.message.as_str())
+                .collect::<Vec<_>>()
+                .join("; ");
+            return Err(InternalWorkerSessionError::Build {
+                message: format!(
+                    "internal Worker feature installation failed: {diagnostics}; missing tools: {}",
+                    missing.join(", ")
+                ),
+            });
+        }
+
+        Box::pin(prepare_internal_worker_session(
+            worker, store, visibility, None, None,
+        ))
+        .await
+    })
+}
+
 fn spawn_internal_log_event_bridge(sink: SegmentLogSink, event_tx: broadcast::Sender<Event>) {
     let (_, mut log_rx) = sink.subscribe_with_snapshot();
     tokio::spawn(async move {
@@ -1076,12 +1189,14 @@ permission = "write"
             input: "input".to_string(),
             cache_key: Some("internal-test".to_string()),
             max_turns: Some(1),
+            engine_configurator: None,
             features: FeatureRegistryBuilder::new(),
             required_tools,
             authority: InternalWorkerAuthority {
                 workspace: WorkerWorkspaceContext::no_workspace(),
                 filesystem: WorkerFilesystemAuthority::None,
                 scope: Scope::empty(),
+                workdir_session: None,
             },
         }
     }

crates/worker/src/session_capture.rs

@@ -143,6 +143,7 @@ pub(crate) struct SearchHit {
 #[derive(Debug, Clone, Copy)]
 pub(crate) enum ReadSelector<'a> {
     Id(&'a str),
+    #[cfg(test)]
     EntryRange([u64; 2]),
 }
 
@@ -418,6 +419,7 @@ impl SessionCapture {
                 .iter()
                 .filter(|entry| entry.id.as_str() == id)
                 .collect(),
+            #[cfg(test)]
             ReadSelector::EntryRange([start, end]) => self
                 .index
                 .iter()

crates/worker/src/spawn/registry.rs

@@ -1,7 +1,8 @@
-//! Parent-owned registry of direct Internal SubWorker sessions.
+//! Parent-owned registry of direct Internal Worker sessions.
 //!
-//! `SubWorkerSpawn` inserts typed `InternalWorkerSessionHandle`s; List/Send/Stop and
-//! worker-observation use the same in-memory authority. Internal children are not persisted, restored, discovered as
+//! `SubWorkerSpawn` inserts controllable SubWorker handles, while host services such as
+//! compaction insert parent-visible service handles without joining the model-facing
+//! List/Send/Stop surface. Internal children are not persisted, restored, discovered as
 //! Runtime Workers, or addressed through sockets. Restore consumes any legacy persisted process
 //! child records only to reclaim their delegated scope and clear obsolete metadata.
 //! Parent registry drop closes all session handles and synchronously returns delegated Write deny
@@ -177,6 +178,52 @@ impl InternalSpawnedWorkerRecord {
     }
 }
 
+/// Parent-visible service Internal Worker. Unlike a SubWorker this record has no
+/// delegated scope, model-facing control name, or stop-summary authority.
+#[derive(Clone)]
+pub(crate) struct InternalServiceWorkerRecord {
+    pub service_kind: String,
+    pub display_name: String,
+    pub session: InternalWorkerSessionHandle,
+    protocol_revision: Arc<AtomicU64>,
+    protocol_emit_lock: Arc<Mutex<()>>,
+    protocol_terminal: Arc<AtomicBool>,
+    forwarding_started: Arc<AtomicBool>,
+}
+
+impl InternalServiceWorkerRecord {
+    pub(crate) fn new(
+        service_kind: impl Into<String>,
+        display_name: impl Into<String>,
+        session: InternalWorkerSessionHandle,
+    ) -> Self {
+        Self {
+            service_kind: service_kind.into(),
+            display_name: display_name.into(),
+            session,
+            protocol_revision: Arc::new(AtomicU64::new(0)),
+            protocol_emit_lock: Arc::new(Mutex::new(())),
+            protocol_terminal: Arc::new(AtomicBool::new(false)),
+            forwarding_started: Arc::new(AtomicBool::new(false)),
+        }
+    }
+
+    fn protocol_ref(&self, parent_session_id: Option<String>) -> InternalWorkerRef {
+        InternalWorkerRef {
+            session_id: self.session.session_id_string(),
+            name: self.display_name.clone(),
+            parent_session_id,
+            kind: InternalWorkerKind::Service {
+                kind: self.service_kind.clone(),
+            },
+        }
+    }
+
+    fn protocol_revision(&self) -> u64 {
+        self.protocol_revision.load(Ordering::Acquire)
+    }
+}
+
 pub(crate) struct InternalSpawnReservation {
     registry: Arc<SpawnedWorkerRegistry>,
     worker_name: String,
@@ -214,6 +261,7 @@ impl Drop for InternalSpawnReservation {
 
 pub struct SpawnedWorkerRegistry {
     internal_records: std::sync::Mutex<Vec<InternalSpawnedWorkerRecord>>,
+    service_records: std::sync::Mutex<Vec<InternalServiceWorkerRecord>>,
     internal_names: std::sync::Mutex<HashSet<String>>,
     parent_scope: Option<SharedScope>,
     parent_protocol: Mutex<Option<(broadcast::Sender<Event>, String)>>,
@@ -226,10 +274,21 @@ pub struct SpawnedWorkerRegistryLoad {
 }
 
 impl SpawnedWorkerRegistry {
+    pub(crate) fn new_for_internal_services() -> Arc<Self> {
+        Arc::new(Self {
+            internal_records: std::sync::Mutex::new(Vec::new()),
+            service_records: std::sync::Mutex::new(Vec::new()),
+            internal_names: std::sync::Mutex::new(HashSet::new()),
+            parent_scope: None,
+            parent_protocol: Mutex::new(None),
+        })
+    }
+
     /// Empty registry used by tests and non-spawning projections.
     pub fn new(_runtime_dir: Arc<RuntimeDir>) -> Arc<Self> {
         Arc::new(Self {
             internal_records: std::sync::Mutex::new(Vec::new()),
+            service_records: std::sync::Mutex::new(Vec::new()),
             internal_names: std::sync::Mutex::new(HashSet::new()),
             parent_scope: None,
             parent_protocol: Mutex::new(None),
@@ -239,6 +298,7 @@ impl SpawnedWorkerRegistry {
     pub(crate) fn new_internal(_parent_name: String, parent_scope: SharedScope) -> Arc<Self> {
         Arc::new(Self {
             internal_records: std::sync::Mutex::new(Vec::new()),
+            service_records: std::sync::Mutex::new(Vec::new()),
             internal_names: std::sync::Mutex::new(HashSet::new()),
             parent_scope: Some(parent_scope),
             parent_protocol: Mutex::new(None),
@@ -317,6 +377,7 @@ impl SpawnedWorkerRegistry {
         Ok(SpawnedWorkerRegistryLoad {
             registry: Arc::new(Self {
                 internal_records: std::sync::Mutex::new(Vec::new()),
+                service_records: std::sync::Mutex::new(Vec::new()),
                 internal_names: std::sync::Mutex::new(HashSet::new()),
                 parent_scope,
                 parent_protocol: Mutex::new(None),
@@ -356,6 +417,144 @@ impl SpawnedWorkerRegistry {
         for record in self.internal_records.lock().unwrap().clone() {
             self.start_protocol_forwarding(record);
         }
+        for record in self.service_records.lock().unwrap().clone() {
+            self.start_service_protocol_forwarding(record);
+        }
+    }
+
+    /// Register a parent-visible service Internal Worker before its first turn.
+    pub(crate) fn attach_service(
+        &self,
+        record: InternalServiceWorkerRecord,
+    ) -> io::Result<InternalWorkerRef> {
+        let parent_session_id = self
+            .parent_protocol
+            .lock()
+            .unwrap()
+            .as_ref()
+            .map(|(_, id)| id.clone());
+        let worker_ref = record.protocol_ref(parent_session_id);
+        let session_id = record.session.session_id_string();
+        let mut records = self
+            .service_records
+            .lock()
+            .map_err(|_| io::Error::other("internal service-worker registry lock poisoned"))?;
+        if records
+            .iter()
+            .any(|candidate| candidate.session.session_id_string() == session_id)
+        {
+            return Err(io::Error::new(
+                io::ErrorKind::AlreadyExists,
+                "internal service Worker is already registered",
+            ));
+        }
+        records.push(record.clone());
+        drop(records);
+        self.start_service_protocol_forwarding(record);
+        Ok(worker_ref)
+    }
+
+    /// Stop and remove one parent-owned service Worker. This is host-only and is
+    /// intentionally separate from the SubWorker control surface.
+    pub(crate) async fn stop_service(&self, session_id: &str) -> io::Result<bool> {
+        let record = self
+            .service_records
+            .lock()
+            .map_err(|_| io::Error::other("internal service-worker registry lock poisoned"))?
+            .iter()
+            .find(|record| record.session.session_id_string() == session_id)
+            .cloned();
+        let Some(record) = record else {
+            return Ok(false);
+        };
+        record
+            .session
+            .stop()
+            .await
+            .map_err(|error| io::Error::other(error.to_string()))?;
+        self.remove_service(session_id)
+    }
+
+    /// Remove one service Worker and emit the terminal projection fence.
+    pub(crate) fn remove_service(&self, session_id: &str) -> io::Result<bool> {
+        let removed = {
+            let mut records = self
+                .service_records
+                .lock()
+                .map_err(|_| io::Error::other("internal service-worker registry lock poisoned"))?;
+            records
+                .iter()
+                .position(|record| record.session.session_id_string() == session_id)
+                .map(|index| records.remove(index))
+        };
+        if let Some(record) = removed {
+            self.publish_service_removal(&record);
+            Ok(true)
+        } else {
+            Ok(false)
+        }
+    }
+
+    fn start_service_protocol_forwarding(&self, record: InternalServiceWorkerRecord) {
+        if record.session.visibility() != InternalWorkerVisibility::ParentClient
+            || record.forwarding_started.swap(true, Ordering::AcqRel)
+        {
+            return;
+        }
+        let Some((parent_tx, parent_session_id)) = self.parent_protocol.lock().unwrap().clone()
+        else {
+            record.forwarding_started.store(false, Ordering::Release);
+            return;
+        };
+        let worker = record.protocol_ref(Some(parent_session_id));
+        let protocol_revision = record.protocol_revision.clone();
+        let protocol_emit_lock = record.protocol_emit_lock.clone();
+        let protocol_terminal = record.protocol_terminal.clone();
+        let mut child_rx = record.session.subscribe_events();
+        tokio::spawn(async move {
+            loop {
+                match child_rx.recv().await {
+                    Ok(event) => {
+                        let shutdown = matches!(event, Event::Shutdown);
+                        let _emit_guard = protocol_emit_lock
+                            .lock()
+                            .unwrap_or_else(|error| error.into_inner());
+                        if protocol_terminal.load(Ordering::Acquire) {
+                            break;
+                        }
+                        let revision = protocol_revision.fetch_add(1, Ordering::AcqRel) + 1;
+                        let _ = parent_tx.send(Event::InternalWorker {
+                            worker: worker.clone(),
+                            revision,
+                            event: Box::new(event),
+                        });
+                        if shutdown {
+                            break;
+                        }
+                    }
+                    Err(broadcast::error::RecvError::Lagged(skipped)) => {
+                        let _emit_guard = protocol_emit_lock
+                            .lock()
+                            .unwrap_or_else(|error| error.into_inner());
+                        if protocol_terminal.load(Ordering::Acquire) {
+                            break;
+                        }
+                        let revision = protocol_revision.fetch_add(1, Ordering::AcqRel) + 1;
+                        let _ = parent_tx.send(Event::InternalWorker {
+                            worker: worker.clone(),
+                            revision,
+                            event: Box::new(Event::Error {
+                                code: protocol::ErrorCode::Internal,
+                                message: format!(
+                                    "internal Worker output lagged by {skipped} events; reconnect to resynchronize"
+                                ),
+                            }),
+                        });
+                    }
+                    Err(broadcast::error::RecvError::Closed) => break,
+                }
+            }
+        });
     }
 
     fn start_protocol_forwarding(&self, record: InternalSpawnedWorkerRecord) {
@@ -427,28 +626,37 @@ impl SpawnedWorkerRegistry {
             .unwrap()
             .as_ref()
             .map(|(_, id)| id.clone());
-        self.internal_records
+        let mut snapshots = self
+            .internal_records
             .lock()
             .unwrap()
             .iter()
             .filter(|record| record.session.visibility() == InternalWorkerVisibility::ParentClient)
             .map(|record| {
-                let snapshot = record.session.protocol_snapshot();
-                InternalWorkerSnapshot {
-                    worker: record.protocol_ref(parent_session_id.clone()),
-                    revision: record.protocol_revision(),
-                    entries: snapshot
-                        .entries
-                        .into_iter()
-                        .filter_map(|entry| serde_json::to_value(entry).ok())
-                        .collect(),
-                    status: snapshot.status,
-                    error: snapshot.error,
-                    in_flight: snapshot.in_flight,
-                    internal_workers: snapshot.internal_workers,
-                }
+                internal_worker_snapshot(
+                    record.protocol_ref(parent_session_id.clone()),
+                    record.protocol_revision(),
+                    &record.session,
+                )
             })
-            .collect()
+            .collect::<Vec<_>>();
+        snapshots.extend(
+            self.service_records
+                .lock()
+                .unwrap()
+                .iter()
+                .filter(|record| {
+                    record.session.visibility() == InternalWorkerVisibility::ParentClient
+                })
+                .map(|record| {
+                    internal_worker_snapshot(
+                        record.protocol_ref(parent_session_id.clone()),
+                        record.protocol_revision(),
+                        &record.session,
+                    )
+                }),
+        );
+        snapshots
     }
 
     pub(crate) fn get_internal(&self, worker_name: &str) -> Option<InternalSpawnedWorkerRecord> {
@@ -567,6 +775,47 @@ impl SpawnedWorkerRegistry {
             revision,
         });
     }
+
+    fn publish_service_removal(&self, record: &InternalServiceWorkerRecord) {
+        if record.session.visibility() != InternalWorkerVisibility::ParentClient {
+            return;
+        }
+        let Some((parent_tx, parent_session_id)) = self.parent_protocol.lock().unwrap().clone()
+        else {
+            return;
+        };
+        let _emit_guard = record
+            .protocol_emit_lock
+            .lock()
+            .unwrap_or_else(|error| error.into_inner());
+        record.protocol_terminal.store(true, Ordering::Release);
+        let revision = record.protocol_revision.fetch_add(1, Ordering::AcqRel) + 1;
+        let _ = parent_tx.send(Event::InternalWorkerRemoved {
+            worker: record.protocol_ref(Some(parent_session_id)),
+            revision,
+        });
+    }
+}
+
+fn internal_worker_snapshot(
+    worker: InternalWorkerRef,
+    revision: u64,
+    session: &InternalWorkerSessionHandle,
+) -> InternalWorkerSnapshot {
+    let snapshot = session.protocol_snapshot();
+    InternalWorkerSnapshot {
+        worker,
+        revision,
+        entries: snapshot
+            .entries
+            .into_iter()
+            .filter_map(|entry| serde_json::to_value(entry).ok())
+            .collect(),
+        status: snapshot.status,
+        error: snapshot.error,
+        in_flight: snapshot.in_flight,
+        internal_workers: snapshot.internal_workers,
+    }
 }
 
 impl Drop for SpawnedWorkerRegistry {
@@ -813,6 +1062,63 @@ mod tests {
         assert_eq!(snapshots[0].in_flight.blocks.len(), 1);
     }
 
+    #[tokio::test]
+    async fn service_worker_is_parent_visible_but_not_subworker_controllable() {
+        let registry = registry();
+        let (parent_tx, mut parent_rx) = broadcast::channel(16);
+        registry.attach_parent_protocol(parent_tx, "parent-session".into());
+        let (session, child_tx) =
+            test_internal_worker_session(InternalWorkerVisibility::ParentClient);
+        let session_id = session.session_id_string();
+
+        let worker_ref = registry
+            .attach_service(InternalServiceWorkerRecord::new(
+                "compaction",
+                "Compaction",
+                session,
+            ))
+            .unwrap();
+        assert!(matches!(
+            worker_ref.kind,
+            InternalWorkerKind::Service { ref kind } if kind == "compaction"
+        ));
+        assert!(registry.list_internal().is_empty());
+
+        child_tx
+            .send(Event::TextDone {
+                text: "summary candidate".into(),
+            })
+            .unwrap();
+        let event = tokio::time::timeout(Duration::from_secs(1), parent_rx.recv())
+            .await
+            .unwrap()
+            .unwrap();
+        assert!(matches!(
+            event,
+            Event::InternalWorker { worker, revision: 1, event }
+                if worker.session_id == session_id
+                    && matches!(worker.kind, InternalWorkerKind::Service { ref kind } if kind == "compaction")
+                    && matches!(*event, Event::TextDone { ref text } if text == "summary candidate")
+        ));
+        let snapshots = registry.internal_worker_snapshots();
+        assert_eq!(snapshots.len(), 1);
+        assert!(matches!(
+            snapshots[0].worker.kind,
+            InternalWorkerKind::Service { ref kind } if kind == "compaction"
+        ));
+        assert!(registry.remove_service(&session_id).unwrap());
+        let removed = tokio::time::timeout(Duration::from_secs(1), parent_rx.recv())
+            .await
+            .unwrap()
+            .unwrap();
+        assert!(matches!(
+            removed,
+            Event::InternalWorkerRemoved { worker, revision: 2 }
+                if worker.session_id == session_id
+        ));
+        assert!(registry.internal_worker_snapshots().is_empty());
+    }
+
     #[tokio::test]
     async fn service_private_internal_output_is_never_disclosed() {
         let registry = registry();

crates/worker/src/worker.rs

@@ -46,12 +46,11 @@ use crate::hook::{
 };
 use crate::in_flight::InFlightEvents;
 use crate::internal_worker::{
-    InternalWorkerAuthority, InternalWorkerIdentity, InternalWorkerSpec, run_internal_worker,
-    run_internal_worker_with_cancel_sender,
+    InternalWorkerAuthority, InternalWorkerIdentity, InternalWorkerSpec, InternalWorkerVisibility,
+    prepare_internal_worker_from_spec, run_internal_worker, run_internal_worker_with_cancel_sender,
 };
 
 const COMPACTION_EXTENSION_DOMAIN: &str = "yoi.compaction";
-const COMPACTION_BLOCK_ID: &str = "compact";
 const WORKER_ORCHESTRATION_INSTRUCTION_ID: &str = "worker.orchestration";
 const WORKER_ORCHESTRATION_PROMPT_REF: &str = "common.worker_orchestration";
 
@@ -76,7 +75,8 @@ use crate::skill::{SkillActivationResponse, SkillClientError};
 #[cfg(test)]
 use async_trait::async_trait;
 use protocol::{
-    AlertLevel, AlertSource, Event, RewindSummary, RewindTarget, RewindTargetId, Segment,
+    AlertLevel, AlertSource, CompactionLifecycle, CompactionLifecycleState, Event, RewindSummary,
+    RewindTarget, RewindTargetId, Segment,
 };
 use tokio::net::UnixStream;
 use tokio::sync::broadcast;
@@ -971,6 +971,9 @@ pub struct Worker<C: LlmClient, St: Store> {
     /// notifications, events sent here are NOT replayed to clients that
     /// connect after the fact — they are fire-and-forget broadcasts.
     event_tx: Option<broadcast::Sender<Event>>,
+    /// Parent-owned projection/control boundary for observable Internal service Workers.
+    /// Service Workers are never exposed through the model-facing SubWorker control surface.
+    internal_worker_registry: Option<Arc<crate::spawn::registry::SpawnedWorkerRegistry>>,
     in_flight: Option<InFlightEvents>,
     /// Monotonic counter incremented by worker event bridges when an
     /// assistant-side execution artifact becomes visible to clients before
@@ -1115,6 +1118,7 @@ impl<C: LlmClient + Clone + 'static, St: Store + Clone + 'static> Worker<C, St>
             feature_instructions: self.feature_instructions.clone(),
             alerter: self.alerter.clone(),
             event_tx: self.event_tx.clone(),
+            internal_worker_registry: self.internal_worker_registry.clone(),
             in_flight: self.in_flight.clone(),
             ai_activity_counter: self.ai_activity_counter.clone(),
             pending_notifies: NotifyBuffer::new(),
@@ -1315,6 +1319,7 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             feature_instructions: Vec::new(),
             alerter: None,
             event_tx: None,
+            internal_worker_registry: None,
             in_flight: None,
             ai_activity_counter: Arc::new(AtomicUsize::new(0)),
             pending_notifies: NotifyBuffer::new(),
@@ -1957,9 +1962,21 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
     /// Worker-internal operations (currently: compaction) can surface
     /// progress to connected clients.
     pub fn attach_event_tx(&mut self, event_tx: broadcast::Sender<Event>) {
+        let session_id = self.session_id().to_string();
+        let registry = self.internal_worker_registry.get_or_insert_with(
+            crate::spawn::registry::SpawnedWorkerRegistry::new_for_internal_services,
+        );
+        registry.attach_parent_protocol(event_tx.clone(), session_id);
         self.event_tx = Some(event_tx);
     }
 
+    pub(crate) fn attach_internal_worker_registry(
+        &mut self,
+        registry: Arc<crate::spawn::registry::SpawnedWorkerRegistry>,
+    ) {
+        self.internal_worker_registry = Some(registry);
+    }
+
     /// Shared activity counter incremented by worker event bridges when any
     /// assistant-side output is surfaced before history persistence.
     pub fn ai_activity_counter(&self) -> Arc<AtomicUsize> {
@@ -2895,52 +2912,46 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             .map_err(WorkerError::Engine)
     }
 
-    fn persist_compaction_block(
+    fn persist_compaction_lifecycle(
         &mut self,
-        state: &str,
-        message: &str,
-        error: Option<&str>,
-        new_segment_id: Option<SegmentId>,
+        lifecycle: &CompactionLifecycle,
     ) -> Result<(), WorkerError> {
-        let payload = serde_json::json!({
-            "kind": "compaction_block",
-            "schema_version": 1,
-            "block_id": COMPACTION_BLOCK_ID,
-            "state": state,
-            "message": message,
-            "error": error,
-            "new_segment_id": new_segment_id.map(|id| id.to_string()),
-        });
         Ok(self.commit_entry(LogEntry::Extension {
             ts: segment_log::now_millis(),
             domain: COMPACTION_EXTENSION_DOMAIN.into(),
-            payload,
+            payload: serde_json::to_value(lifecycle).map_err(|error| {
+                WorkerError::InvalidState(format!(
+                    "serialize compaction lifecycle {}: {error}",
+                    lifecycle.compaction_id
+                ))
+            })?,
         })?)
     }
 
-    fn persist_and_send_compact_start(&mut self) -> Result<(), WorkerError> {
-        self.persist_compaction_block("running", "Compacting…", None, None)?;
-        self.send_event(Event::CompactStart);
+    fn persist_and_send_compact_start(
+        &mut self,
+        lifecycle: CompactionLifecycle,
+    ) -> Result<(), WorkerError> {
+        self.persist_compaction_lifecycle(&lifecycle)?;
+        self.send_event(Event::CompactStart { lifecycle });
         Ok(())
     }
 
     fn persist_and_send_compact_done(
         &mut self,
-        new_segment_id: SegmentId,
+        lifecycle: CompactionLifecycle,
     ) -> Result<(), WorkerError> {
-        self.persist_compaction_block("done", "Compacted.", None, Some(new_segment_id))?;
-        self.send_event(Event::CompactDone { new_segment_id });
+        self.persist_compaction_lifecycle(&lifecycle)?;
+        self.send_event(Event::CompactDone { lifecycle });
         Ok(())
     }
 
-    fn persist_and_send_compact_failed(&mut self, error: String) -> Result<(), WorkerError> {
-        self.persist_compaction_block(
-            "failed",
-            &format!("Compact failed: {error}"),
-            Some(error.as_str()),
-            None,
-        )?;
-        self.send_event(Event::CompactFailed { error });
+    fn persist_and_send_compact_failed(
+        &mut self,
+        lifecycle: CompactionLifecycle,
+    ) -> Result<(), WorkerError> {
+        self.persist_compaction_lifecycle(&lifecycle)?;
+        self.send_event(Event::CompactFailed { lifecycle });
         Ok(())
     }
 
@@ -2969,14 +2980,12 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
                 .map(|s| s.retained_tokens())
                 .unwrap_or(manifest::defaults::COMPACT_RETAINED_TOKENS);
 
-            self.persist_and_send_compact_start()?;
             match self.compact(retained).await {
                 Ok(new_segment_id) => {
                     info!(
                         new_segment_id = %new_segment_id,
                         "Compaction succeeded, resuming execution"
                     );
-                    self.persist_and_send_compact_done(new_segment_id)?;
                     if let Some(ref state) = self.compact_state {
                         state.record_compact_success();
                     }
@@ -2984,7 +2993,6 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
                 }
                 Err(e) => {
                     warn!(error = %e, "Compaction failed during run");
-                    self.persist_and_send_compact_failed(e.to_string())?;
                     self.alert(
                         AlertLevel::Error,
                         AlertSource::Compactor,
@@ -3017,45 +3025,16 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
         }
 
         let retained = state.retained_tokens();
-        if let Err(err) = self.persist_and_send_compact_start() {
-            warn!(error = %err, "failed to persist proactive compact start");
-            self.alert(
-                AlertLevel::Warn,
-                AlertSource::Compactor,
-                format!("pre-run compaction not started: failed to persist status block: {err}"),
-            );
-            return;
-        }
         match self.compact(retained).await {
             Ok(new_segment_id) => {
                 info!(
                     new_segment_id = %new_segment_id,
                     "Proactive pre-run compaction succeeded"
                 );
-                if let Err(err) = self.persist_and_send_compact_done(new_segment_id) {
-                    warn!(error = %err, "failed to persist proactive compact completion");
-                    self.alert(
-                        AlertLevel::Warn,
-                        AlertSource::Compactor,
-                        format!(
-                            "pre-run compaction completed but status block was not persisted: {err}"
-                        ),
-                    );
-                }
                 state.record_compact_success();
             }
             Err(e) => {
                 warn!(error = %e, "Proactive pre-run compaction failed");
-                if let Err(err) = self.persist_and_send_compact_failed(e.to_string()) {
-                    warn!(error = %err, "failed to persist proactive compact failure");
-                    self.alert(
-                        AlertLevel::Warn,
-                        AlertSource::Compactor,
-                        format!(
-                            "pre-run compaction failed and status block was not persisted: {err}"
-                        ),
-                    );
-                }
                 self.alert(
                     AlertLevel::Warn,
                     AlertSource::Compactor,
@@ -3113,11 +3092,9 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
         }
 
         self.join_memory_task().await;
-        self.persist_and_send_compact_start()?;
         match self.compact(retained).await {
             Ok(new_segment_id) => {
                 info!(new_segment_id = %new_segment_id, "Manual compaction succeeded");
-                self.persist_and_send_compact_done(new_segment_id)?;
                 if let Some(ref state) = state {
                     state.record_compact_success();
                 }
@@ -3125,7 +3102,6 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             }
             Err(e) => {
                 warn!(error = %e, "Manual compaction failed");
-                self.persist_and_send_compact_failed(e.to_string())?;
                 self.alert(
                     AlertLevel::Error,
                     AlertSource::Compactor,
@@ -3262,20 +3238,79 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
         Ok(())
     }
 
-    /// Compact the current session by summarising history via a
-    /// disposable Engine, then replacing history with
-    /// `[summary, ...recent_turns]` in a new Segment of the same Session.
-    ///
-    /// The summary Engine uses:
-    /// - `compaction.model` from the manifest if configured, or
-    /// - a clone of the main LlmClient via `clone_boxed()`.
-    ///
-    /// Returns the new Segment ID. The Worker keeps its Session ID.
+    /// Runs one parent-owned observable compaction service and returns the new
+    /// Segment ID. Lifecycle revisions are committed before they are broadcast.
     pub async fn compact(&mut self, retained_tokens: u64) -> Result<SegmentId, WorkerError> {
+        let mut lifecycle = CompactionLifecycle {
+            schema_version: 2,
+            compaction_id: uuid::Uuid::now_v7().to_string(),
+            revision: 1,
+            internal_worker: None,
+            state: CompactionLifecycleState::Running,
+            started_at_ms: segment_log::now_millis(),
+            ended_at_ms: None,
+            summary: None,
+            error: None,
+            new_segment_id: None,
+        };
+        self.persist_and_send_compact_start(lifecycle.clone())?;
+        match self.compact_impl(retained_tokens, &mut lifecycle).await {
+            Ok((new_segment_id, summary)) => {
+                lifecycle.revision = lifecycle.revision.saturating_add(1);
+                lifecycle.state = CompactionLifecycleState::Done;
+                lifecycle.ended_at_ms = Some(segment_log::now_millis());
+                lifecycle.summary = Some(summary);
+                lifecycle.new_segment_id = Some(new_segment_id.to_string());
+                let terminal = self.persist_and_send_compact_done(lifecycle.clone());
+                self.release_compaction_service(&lifecycle).await;
+                terminal?;
+                Ok(new_segment_id)
+            }
+            Err(error) => {
+                lifecycle.revision = lifecycle.revision.saturating_add(1);
+                lifecycle.state = if matches!(error, WorkerError::CompactCancelled) {
+                    CompactionLifecycleState::Interrupted
+                } else {
+                    CompactionLifecycleState::Failed
+                };
+                lifecycle.ended_at_ms = Some(segment_log::now_millis());
+                lifecycle.error = Some(error.to_string().chars().take(2_000).collect());
+                let terminal = self.persist_and_send_compact_failed(lifecycle.clone());
+                self.release_compaction_service(&lifecycle).await;
+                terminal?;
+                Err(error)
+            }
+        }
+    }
+
+    async fn release_compaction_service(&self, lifecycle: &CompactionLifecycle) {
+        let Some(session_id) = lifecycle
+            .internal_worker
+            .as_ref()
+            .map(|worker| worker.session_id.as_str())
+        else {
+            return;
+        };
+        let Some(registry) = &self.internal_worker_registry else {
+            return;
+        };
+        if let Err(error) = registry.stop_service(session_id).await {
+            warn!(
+                compaction_id = %lifecycle.compaction_id,
+                internal_worker_session_id = %session_id,
+                error = %error,
+                "failed to release terminal compaction Internal Worker"
+            );
+        }
+    }
+
+    async fn compact_impl(
+        &mut self,
+        retained_tokens: u64,
+        lifecycle: &mut CompactionLifecycle,
+    ) -> Result<(SegmentId, String), WorkerError> {
         use crate::compact::worker::{
-            CompactWorkerContext, CompactWorkerInterceptor, add_reference_tool,
-            mark_read_required_tool, read_session_items_tool, search_session_log_tool,
-            write_summary_tool,
+            CompactWorkerContext, CompactWorkerInterceptor, CompactionOutputFeature,
         };
         use crate::fs_view::WorkerFsView;
 
@@ -3385,10 +3420,12 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             auto_read_budget,
         )));
 
-        // Build an independent compact worker. It clones the main Worker's
-        // provider handle, so compact-time reads use the same WorkdirSession instance.
-        // No-workdir Workers deliberately omit compact-time filesystem tools.
+        // Build a normal parent-owned Internal Worker over a pinned immutable
+        // capture. Only SessionExplore and compaction output tools are installed.
         let workdir = self.workdir_session.clone();
+        let read_only_workdir = workdir.clone().map(|session| {
+            Arc::new(ReadOnlyWorkdirSession::new(session)) as workdir::WorkdirSessionHandle
+        });
         let summary_tracker = tools::Tracker::new();
         let summary_client: Box<dyn LlmClient> = self.build_compactor_client()?;
         let summary_system_prompt = self
@@ -3396,51 +3433,129 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             .load_full()
             .compact_system()
             .map_err(WorkerError::PromptCatalog)?;
-        let mut summary_worker = Engine::new(summary_client).system_prompt(summary_system_prompt);
-        summary_worker.set_cache_key(Some(self.segment_id().to_string()));
-
-        // Occupancy-based input-token meter + interceptor. The tracker pairs
-        // each pre-request history length with the following UsageEvent, then
-        // the interceptor projects current prompt occupancy with the same
-        // UsageRecord counter used by the main Worker thresholds.
         let summary_usage_tracker = Arc::new(UsageTracker::new());
-        {
-            let tracker = summary_usage_tracker.clone();
-            summary_worker.on_usage(move |event| {
-                tracker.record_usage(event);
-            });
-        }
         let compactor_warning_cb = self.alerter.clone().map(|alerter| {
             Arc::new(move |message: String| {
                 alerter.alert(AlertLevel::Warn, AlertSource::Compactor, message);
             }) as Arc<dyn Fn(String) + Send + Sync>
         });
-        summary_worker.set_interceptor(CompactWorkerInterceptor::new(
-            summary_usage_tracker,
+        let interceptor = CompactWorkerInterceptor::new(
+            summary_usage_tracker.clone(),
             worker_context_max_tokens,
             finish_warning_remaining_tokens,
             final_reserve_tokens,
             compactor_warning_cb,
-        ));
-        summary_worker.set_max_turns(worker_max_turns);
+        );
+        let tracker_for_engine = summary_usage_tracker.clone();
+        let features = crate::feature::FeatureRegistryBuilder::new()
+            .with_module(
+                crate::feature::builtin::session_explore::SessionExploreFeature::new(
+                    crate::feature::builtin::session_explore::SessionExploreState::new(
+                        crate::session_capture::SessionCapture::new(
+                            self.segment_id().to_string(),
+                            items_to_summarise.clone(),
+                        ),
+                    ),
+                ),
+            )
+            .with_module(CompactionOutputFeature::new(
+                read_only_workdir.clone(),
+                summary_tracker,
+                ctx.clone(),
+            ));
+        let required_tools: &'static [&'static str] = if read_only_workdir.is_some() {
+            &[
+                "ShowOverview",
+                "SearchEntries",
+                "ReadEntry",
+                "Read",
+                "mark_read_required",
+                "add_reference",
+                "write_summary",
+            ]
+        } else {
+            &[
+                "ShowOverview",
+                "SearchEntries",
+                "ReadEntry",
+                "add_reference",
+                "write_summary",
+            ]
+        };
+        let handle = prepare_internal_worker_from_spec(
+            InternalWorkerSpec {
+                identity: InternalWorkerIdentity {
+                    kind: "compaction",
+                    run_id: uuid::Uuid::parse_str(&lifecycle.compaction_id).map_err(|error| {
+                        WorkerError::InvalidState(format!("invalid compaction id: {error}"))
+                    })?,
+                },
+                manifest: self.manifest.clone(),
+                client: summary_client,
+                system_prompt: summary_system_prompt,
+                input: summary_input.text.clone(),
+                cache_key: Some(self.segment_id().to_string()),
+                max_turns: worker_max_turns,
+                engine_configurator: Some(Box::new(move |engine| {
+                    let tracker = tracker_for_engine;
+                    engine.on_usage(move |event| {
+                        tracker.record_usage(event);
+                    });
+                    engine.set_interceptor(interceptor);
+                })),
+                features,
+                required_tools,
+                authority: InternalWorkerAuthority {
+                    workspace: WorkerWorkspaceContext::no_workspace(),
+                    filesystem: WorkerFilesystemAuthority::None,
+                    scope: Scope::empty(),
+                    workdir_session: read_only_workdir,
+                },
+            },
+            InternalWorkerVisibility::ParentClient,
+        )
+        .await
+        .map_err(|error| WorkerError::InvalidState(error.to_string()))?;
+        let registry = self
+            .internal_worker_registry
+            .get_or_insert_with(
+                crate::spawn::registry::SpawnedWorkerRegistry::new_for_internal_services,
+            )
+            .clone();
+        let internal_ref = registry
+            .attach_service(crate::spawn::registry::InternalServiceWorkerRecord::new(
+                "compaction",
+                "Compaction",
+                handle.clone(),
+            ))
+            .map_err(|error| WorkerError::InvalidState(error.to_string()))?;
+        lifecycle.revision = lifecycle.revision.saturating_add(1);
+        lifecycle.internal_worker = Some(internal_ref);
+        self.persist_and_send_compact_start(lifecycle.clone())?;
 
-        // Tools: read_file (shared scope, fresh tracker), bounded session
-        // history exploration, and compact-specific tools that populate `ctx`.
-        let compact_target_items = Arc::new(items_to_summarise.clone());
-        if let Some(workdir) = workdir.clone() {
-            summary_worker.register_tool(tools::read_tool(workdir.clone(), summary_tracker));
-            summary_worker.register_tool(mark_read_required_tool(workdir, ctx.clone()));
+        if let Err(error) = handle.send(summary_input.text).await {
+            let _ = registry.remove_service(&handle.session_id_string());
+            return Err(WorkerError::InvalidState(error.to_string()));
+        }
+        match handle.wait_until_idle().await {
+            crate::internal_worker::InternalWorkerSessionStatus::Idle => {}
+            crate::internal_worker::InternalWorkerSessionStatus::Stopped => {
+                return Err(WorkerError::CompactCancelled);
+            }
+            crate::internal_worker::InternalWorkerSessionStatus::Failed => {
+                return Err(WorkerError::InvalidState(
+                    handle
+                        .protocol_snapshot()
+                        .error
+                        .unwrap_or_else(|| "compactor Internal Worker failed".into()),
+                ));
+            }
+            status => {
+                return Err(WorkerError::InvalidState(format!(
+                    "compactor Internal Worker ended in {status:?}"
+                )));
+            }
         }
-        summary_worker.register_tool(search_session_log_tool(compact_target_items.clone()));
-        summary_worker.register_tool(read_session_items_tool(compact_target_items));
-        summary_worker.register_tool(add_reference_tool(ctx.clone()));
-        summary_worker.register_tool(write_summary_tool(ctx.clone()));
-
-        let out = summary_worker
-            .run(summary_input.text)
-            .await
-            .map_err(WorkerError::Engine)?;
-        let mut locked_engine = out.engine;
 
         // Guard: nudge the worker once more if the expected outputs
         // (summary, and any auto-read nominations when default refs
@@ -3469,10 +3584,24 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             }
         };
         if let Some(prompt) = nudge {
-            let _ = locked_engine
-                .run(prompt)
+            handle
+                .send(prompt)
                 .await
-                .map_err(WorkerError::Engine)?;
+                .map_err(|error| WorkerError::InvalidState(error.to_string()))?;
+            match handle.wait_until_idle().await {
+                crate::internal_worker::InternalWorkerSessionStatus::Idle => {}
+                crate::internal_worker::InternalWorkerSessionStatus::Stopped => {
+                    return Err(WorkerError::CompactCancelled);
+                }
+                _ => {
+                    return Err(WorkerError::InvalidState(
+                        handle
+                            .protocol_snapshot()
+                            .error
+                            .unwrap_or_else(|| "compactor Internal Worker failed".into()),
+                    ));
+                }
+            }
         }
 
         let mut final_ctx = ctx.lock().expect("compact ctx poisoned").clone();
@@ -3487,10 +3616,24 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
                  {summary_max_tokens}). Rewrite it now with `write_summary`, preserving the \
                  same five sections but making it concise. Target ≈{summary_target_tokens} tokens."
             );
-            let _ = locked_engine
-                .run(prompt)
+            handle
+                .send(prompt)
                 .await
-                .map_err(WorkerError::Engine)?;
+                .map_err(|error| WorkerError::InvalidState(error.to_string()))?;
+            match handle.wait_until_idle().await {
+                crate::internal_worker::InternalWorkerSessionStatus::Idle => {}
+                crate::internal_worker::InternalWorkerSessionStatus::Stopped => {
+                    return Err(WorkerError::CompactCancelled);
+                }
+                _ => {
+                    return Err(WorkerError::InvalidState(
+                        handle
+                            .protocol_snapshot()
+                            .error
+                            .unwrap_or_else(|| "compactor Internal Worker failed".into()),
+                    ));
+                }
+            }
             final_ctx = ctx.lock().expect("compact ctx poisoned").clone();
             summary_text = final_ctx
                 .summary
@@ -3694,7 +3837,7 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             .lock()
             .expect("extract_pointer poisoned") = None;
 
-        Ok(new_segment_id)
+        Ok((new_segment_id, summary_text))
     }
 
     /// Build the LlmClient for the compactor Engine.
@@ -4080,6 +4223,7 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             input: input_text,
             cache_key: Some(self.segment_id().to_string()),
             max_turns: extract_worker_max_turns,
+            engine_configurator: None,
             features,
             required_tools: &[
                 "ShowOverview",
@@ -4092,6 +4236,7 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
                 workspace: self.workspace_context.clone(),
                 filesystem: WorkerFilesystemAuthority::None,
                 scope: Scope::empty(),
+                workdir_session: None,
             },
         };
         let internal_result = match cancel_observer {
@@ -4566,6 +4711,7 @@ where
             feature_instructions: common.feature_instructions,
             alerter: None,
             event_tx: None,
+            internal_worker_registry: None,
             in_flight: None,
             ai_activity_counter: Arc::new(AtomicUsize::new(0)),
             pending_notifies: NotifyBuffer::new(),
@@ -4643,6 +4789,7 @@ where
             feature_instructions: common.feature_instructions,
             alerter: None,
             event_tx: None,
+            internal_worker_registry: None,
             in_flight: None,
             ai_activity_counter: Arc::new(AtomicUsize::new(0)),
             pending_notifies: NotifyBuffer::new(),
@@ -4755,6 +4902,7 @@ where
             feature_instructions: common.feature_instructions,
             alerter: None,
             event_tx: None,
+            internal_worker_registry: None,
             in_flight: None,
             ai_activity_counter: Arc::new(AtomicUsize::new(0)),
             pending_notifies: NotifyBuffer::new(),
@@ -5071,6 +5219,7 @@ where
             feature_instructions: common.feature_instructions,
             alerter: None,
             event_tx: None,
+            internal_worker_registry: None,
             in_flight: None,
             ai_activity_counter: Arc::new(AtomicUsize::new(0)),
             pending_notifies: NotifyBuffer::new(),
@@ -5725,6 +5874,9 @@ pub enum WorkerError {
     #[error("compact worker did not produce a summary (write_summary was never called)")]
     CompactSummaryMissing,
 
+    #[error("compaction was cancelled")]
+    CompactCancelled,
+
     #[error("compact summary too large: {tokens} tokens exceeds max {max}")]
     CompactSummaryTooLarge { tokens: u64, max: u64 },
 

crates/worker/tests/compact_events_test.rs

@@ -431,7 +431,7 @@ async fn pre_run_compact_success_broadcasts_start_and_done() {
     let kinds: Vec<&str> = events
         .iter()
         .map(|e| match e {
-            Event::CompactStart => "start",
+            Event::CompactStart { .. } => "start",
             Event::CompactDone { .. } => "done",
             Event::CompactFailed { .. } => "failed",
             _ => "other",
@@ -445,10 +445,61 @@ async fn pre_run_compact_success_broadcasts_start_and_done() {
         !kinds.contains(&"failed"),
         "unexpected CompactFailed in {kinds:?}"
     );
+    let starts = events
+        .iter()
+        .filter_map(|event| match event {
+            Event::CompactStart { lifecycle } => Some(lifecycle),
+            _ => None,
+        })
+        .collect::<Vec<_>>();
+    assert_eq!(
+        starts.len(),
+        2,
+        "start and Internal Worker binding revisions"
+    );
+    assert_eq!(starts[0].compaction_id, starts[1].compaction_id);
+    assert_eq!(starts[0].revision, 1);
+    assert!(starts[0].internal_worker.is_none());
+    assert_eq!(starts[1].revision, 2);
+    assert!(matches!(
+        starts[1].internal_worker.as_ref().map(|worker| &worker.kind),
+        Some(protocol::InternalWorkerKind::Service { kind }) if kind == "compaction"
+    ));
+    assert!(events.iter().any(|event| matches!(
+        event,
+        Event::InternalWorker { worker, .. }
+            if matches!(&worker.kind, protocol::InternalWorkerKind::Service { kind } if kind == "compaction")
+    )), "compactor activity must be projected through the parent stream");
+    let completed = events
+        .iter()
+        .find_map(|event| match event {
+            Event::CompactDone { lifecycle } => Some(lifecycle),
+            _ => None,
+        })
+        .expect("completed lifecycle");
+    assert_eq!(completed.compaction_id, starts[0].compaction_id);
+    assert_eq!(completed.revision, 3);
+    assert_eq!(completed.summary.as_deref(), Some("summary"));
+    assert_eq!(completed.state, protocol::CompactionLifecycleState::Done);
+    let done_index = events
+        .iter()
+        .position(|event| matches!(event, Event::CompactDone { .. }))
+        .expect("done event");
+    let removed_index = events
+        .iter()
+        .position(|event| matches!(event, Event::InternalWorkerRemoved { .. }))
+        .expect("terminal compactor session must be released");
+    assert!(
+        done_index < removed_index,
+        "terminal lifecycle precedes release fence"
+    );
 
     // CompactDone carries the new Segment ID; the Session ID is unchanged.
     let new_id_in_event = events.iter().find_map(|e| match e {
-        Event::CompactDone { new_segment_id } => Some(*new_segment_id),
+        Event::CompactDone { lifecycle } => lifecycle
+            .new_segment_id
+            .as_deref()
+            .and_then(|value| uuid::Uuid::parse_str(value).ok()),
         _ => None,
     });
     assert!(new_id_in_event.is_some(), "CompactDone missing");
@@ -488,7 +539,7 @@ async fn mid_turn_compact_success_broadcasts_start_and_done() {
     let kinds: Vec<&str> = events
         .iter()
         .map(|e| match e {
-            Event::CompactStart => "start",
+            Event::CompactStart { .. } => "start",
             Event::CompactDone { .. } => "done",
             Event::CompactFailed { .. } => "failed",
             _ => "other",
@@ -504,7 +555,10 @@ async fn mid_turn_compact_success_broadcasts_start_and_done() {
     );
 
     let new_id_in_event = events.iter().find_map(|e| match e {
-        Event::CompactDone { new_segment_id } => Some(*new_segment_id),
+        Event::CompactDone { lifecycle } => lifecycle
+            .new_segment_id
+            .as_deref()
+            .and_then(|value| uuid::Uuid::parse_str(value).ok()),
         _ => None,
     });
     assert_eq!(new_id_in_event, Some(worker.segment_id()));
@@ -659,7 +713,7 @@ async fn pre_run_compact_failure_broadcasts_start_and_failed() {
     let kinds: Vec<&str> = events
         .iter()
         .map(|e| match e {
-            Event::CompactStart => "start",
+            Event::CompactStart { .. } => "start",
             Event::CompactDone { .. } => "done",
             Event::CompactFailed { .. } => "failed",
             _ => "other",
@@ -817,11 +871,14 @@ async fn controller_compact_method_emits_start_and_done() {
             .expect("timeout waiting for compact events")
             .expect("event")
         {
-            Event::CompactStart => saw_start = true,
+            Event::CompactStart { .. } => saw_start = true,
             Event::CompactDone { .. } => {
                 break;
             }
-            Event::CompactFailed { error } => panic!("manual compact failed: {error}"),
+            Event::CompactFailed { lifecycle } => panic!(
+                "manual compact failed: {}",
+                lifecycle.error.as_deref().unwrap_or("unknown error")
+            ),
             _ => {}
         }
     }