feat(compact): add optional cancellation signal to the compact seam methods

packages/compact/compact/README.md

@@ -18,8 +18,10 @@ Both methods are **abstract** — the backend owns the entire strategy (token es
 
 | Member | Semantics |
 |---|---|
-| `compactIfNeeded(session, systemPrompt?, model?)` | Estimate the history size; if over the backend's threshold, compact an older range via `compactRegion`, keeping recent context intact. Returns the `CompactionResult`, or `null` if nothing needed compacting. |
-| `compactRegion(session, start, end, model)` | Forcibly summarize surface nodes `[start, end]` (inclusive seqs) into a single replacement node. **Throws** if a compaction is already in progress, if `start`/`end` aren't surface nodes, or if `start > end`. |
+| `compactIfNeeded(session, systemPrompt?, model?, signal?)` | Estimate the history size; if over the backend's threshold, compact an older range via `compactRegion`, keeping recent context intact. Returns the `CompactionResult`, or `null` if nothing needed compacting. |
+| `compactRegion(session, start, end, model, signal?)` | Forcibly summarize surface nodes `[start, end]` (inclusive seqs) into a single replacement node. **Throws** if a compaction is already in progress, if `start`/`end` aren't surface nodes, or if `start > end`. |
+
+Both methods take an optional `signal: AbortSignal`. A backend that summarizes via `ctx.llm.stream()` **must** forward it into the call's `GenerateOptions.signal`, so an abort or fiber dispose tears down the in-flight summarization instead of leaving an orphaned model call running past the cancellation. The turn that the `compact/*` events belong to is not a parameter — it is recoverable from the log (the currently-open turn), so the backend stamps it without the caller supplying it.
 
 ## Surface contract
 

packages/compact/compact/src/index.ts

@@ -69,12 +69,17 @@ export abstract class CompactService extends Service {
    * @param session - the session whose surface may be compacted.
    * @param systemPrompt - optional system prompt, counted toward the estimate.
    * @param model - optional summarization model (falls back to backend config).
+   * @param signal - optional cancellation signal. A backend that summarizes via
+   *   `ctx.llm.stream()` MUST forward this into the call's `GenerateOptions.signal`
+   *   so an abort/dispose tears down the in-flight summarization rather than
+   *   leaving an orphaned model call running past the cancellation.
    * @returns the compaction result, or `null` if no compaction was needed.
    */
   abstract compactIfNeeded(
     session: Session,
     systemPrompt?: string,
     model?: string,
+    signal?: AbortSignal,
   ): Promise<CompactionResult | null>
 
   /**
@@ -88,6 +93,10 @@ export abstract class CompactService extends Service {
    * @param start - inclusive seq of the first surface node to compact.
    * @param end - inclusive seq of the last surface node to compact.
    * @param model - summarization model.
+   * @param signal - optional cancellation signal. A backend that summarizes via
+   *   `ctx.llm.stream()` MUST forward this into the call's `GenerateOptions.signal`
+   *   so an abort/dispose tears down the in-flight summarization rather than
+   *   leaving an orphaned model call running past the cancellation.
    * @throws if compaction is already in progress, or if `start`/`end` are not
    *   valid surface nodes, or if `start > end`.
    */
@@ -96,6 +105,7 @@ export abstract class CompactService extends Service {
     start: number,
     end: number,
     model: string,
+    signal?: AbortSignal,
   ): Promise<CompactionResult>
 }
 

packages/compact/compact/tests/compact.spec.ts

@@ -11,11 +11,27 @@ import { Session, SessionId } from '@deepseek-ai/dsh-session'
  * declaration merge.
  */
 class StubCompactService extends CompactService {
-  override async compactIfNeeded(_session: Session, _systemPrompt?: string, _model?: string): Promise<CompactionResult | null> {
+  /** Records the signal handed to the most recent call, to prove it threads through. */
+  lastSignal: AbortSignal | undefined
+
+  override async compactIfNeeded(
+    _session: Session,
+    _systemPrompt?: string,
+    _model?: string,
+    signal?: AbortSignal,
+  ): Promise<CompactionResult | null> {
+    this.lastSignal = signal
     return null
   }
 
-  override async compactRegion(session: Session, start: number, end: number, _model: string): Promise<CompactionResult> {
+  override async compactRegion(
+    session: Session,
+    start: number,
+    end: number,
+    _model: string,
+    signal?: AbortSignal,
+  ): Promise<CompactionResult> {
+    this.lastSignal = signal
     // Minimal stub honoring the lock + log-only event contract.
     const startEvent = session.append('compact/start', { turn: 0 })
     const summaryEvent = session.append('compact/summary', {
@@ -75,4 +91,17 @@ describe('CompactService seam', () => {
     expect(result.summarySeq).toBeGreaterThan(result.startSeq)
     expect(result.endSeq).toBeGreaterThan(result.summarySeq)
   })
+
+  it('threads the cancellation signal through to the backend', async () => {
+    const ctx = new Context()
+    const svc = new StubCompactService(ctx)
+    const session = new Session(SessionId('s'))
+    const controller = new AbortController()
+
+    await svc.compactRegion(session, 0, 0, 'm', controller.signal)
+    expect(svc.lastSignal).toBe(controller.signal)
+
+    await svc.compactIfNeeded(session, undefined, undefined, controller.signal)
+    expect(svc.lastSignal).toBe(controller.signal)
+  })
 })