fix(sisyphus-orchestrator): add debounce to boulder continuation to prevent infinite loop

Add 5-second cooldown between continuation injections to prevent rapid-fire
session.idle events from causing infinite loop when boulder has incomplete tasks.

src/hooks/sisyphus-orchestrator/index.test.ts

@@ -862,6 +862,46 @@ describe("sisyphus-orchestrator hook", () => {
       expect(mockInput._promptMock).not.toHaveBeenCalled()
     })
 
+    test("should debounce rapid continuation injections (prevent infinite loop)", async () => {
+      // #given - boulder state with incomplete plan
+      const planPath = join(TEST_DIR, "test-plan.md")
+      writeFileSync(planPath, "# Plan\n- [ ] Task 1\n- [ ] Task 2")
+
+      const state: BoulderState = {
+        active_plan: planPath,
+        started_at: "2026-01-02T10:00:00Z",
+        session_ids: [MAIN_SESSION_ID],
+        plan_name: "test-plan",
+      }
+      writeBoulderState(TEST_DIR, state)
+
+      const mockInput = createMockPluginInput()
+      const hook = createSisyphusOrchestratorHook(mockInput)
+
+      // #when - fire multiple idle events in rapid succession (simulating infinite loop bug)
+      await hook.handler({
+        event: {
+          type: "session.idle",
+          properties: { sessionID: MAIN_SESSION_ID },
+        },
+      })
+      await hook.handler({
+        event: {
+          type: "session.idle",
+          properties: { sessionID: MAIN_SESSION_ID },
+        },
+      })
+      await hook.handler({
+        event: {
+          type: "session.idle",
+          properties: { sessionID: MAIN_SESSION_ID },
+        },
+      })
+
+      // #then - should only call prompt ONCE due to debouncing
+      expect(mockInput._promptMock).toHaveBeenCalledTimes(1)
+    })
+
     test("should cleanup on session.deleted", async () => {
       // #given - boulder state
       const planPath = join(TEST_DIR, "test-plan.md")

src/hooks/sisyphus-orchestrator/index.ts

@@ -402,8 +402,11 @@ function isCallerOrchestrator(sessionID?: string): boolean {
 
 interface SessionState {
   lastEventWasAbortError?: boolean
+  lastContinuationInjectedAt?: number
 }
 
+const CONTINUATION_COOLDOWN_MS = 5000
+
 export interface SisyphusOrchestratorHookOptions {
   directory: string
   backgroundManager?: BackgroundManager
@@ -576,6 +579,13 @@ export function createSisyphusOrchestratorHook(
           return
         }
 
+        const now = Date.now()
+        if (state.lastContinuationInjectedAt && now - state.lastContinuationInjectedAt < CONTINUATION_COOLDOWN_MS) {
+          log(`[${HOOK_NAME}] Skipped: continuation cooldown active`, { sessionID, cooldownRemaining: CONTINUATION_COOLDOWN_MS - (now - state.lastContinuationInjectedAt) })
+          return
+        }
+
+        state.lastContinuationInjectedAt = now
         const remaining = progress.total - progress.completed
         injectContinuation(sessionID, boulderState.plan_name, remaining, progress.total)
         return