From 4635d61adad6428816ca2597389a40a3d07c69e0 Mon Sep 17 00:00:00 2001
From: YeonGyu-Kim <code.yeon.gyu@gmail.com>
Date: Wed, 27 May 2026 16:17:30 +0900
Subject: [PATCH] fix(background-agent): defer parent wake during active turns

---
 .../parent-wake-active-turn-event.test.ts     | 52 ++++++++++++++++++-
 .../background-agent/parent-wake-notifier.ts  | 20 ++-----
 2 files changed, 53 insertions(+), 19 deletions(-)

diff --git a/src/features/background-agent/parent-wake-active-turn-event.test.ts b/src/features/background-agent/parent-wake-active-turn-event.test.ts
index 46fa66a75..4a801d126 100644
--- a/src/features/background-agent/parent-wake-active-turn-event.test.ts
+++ b/src/features/background-agent/parent-wake-active-turn-event.test.ts
@@ -108,7 +108,7 @@ async function flushPendingParentWakeForTest(manager: BackgroundManager, session
 }
 
 describe("BackgroundManager parent wake active turn events", () => {
-  test("#when background task completes during active parent turn #then parent gets same-turn no-reply reminder", async () => {
+  test("#when background task completes during active parent turn #then parent wake stays deferred", async () => {
     // given
     const sessionStatuses: Record<string, { type: string }> = {
       "parent-1": { type: "busy" },
@@ -129,9 +129,57 @@ describe("BackgroundManager parent wake active turn events", () => {
     await notifyParentSessionForTest(manager, task)
     await flushPendingParentWakeForTest(manager, "parent-1")
 
+    // then
+    expect(promptAsyncCalls).toHaveLength(0)
+    expect(getPendingParentWakes(manager).has("parent-1")).toBe(true)
+  })
+
+  test("#when duplicate background completions overlap an active parent turn #then one coalesced wake dispatches after idle", async () => {
+    // given
+    const sessionStatuses: Record<string, { type: string }> = {
+      "parent-1": { type: "busy" },
+    }
+    const { manager, promptAsyncCalls } = createManager(sessionStatuses)
+    managerUnderTest = manager
+    const taskA = createTask({
+      id: "task-a",
+      parentSessionId: "parent-1",
+      description: "task A",
+      status: "completed",
+      completedAt: new Date("2026-05-20T14:19:14.625Z"),
+    })
+    const taskB = createTask({
+      id: "task-b",
+      parentSessionId: "parent-1",
+      description: "task B",
+      status: "completed",
+      completedAt: new Date("2026-05-20T14:19:15.625Z"),
+    })
+    getTasks(manager).set(taskA.id, taskA)
+    getTasks(manager).set(taskB.id, taskB)
+    getPendingByParent(manager).set(taskA.parentSessionId, new Set([taskA.id, taskB.id]))
+
+    // when
+    await notifyParentSessionForTest(manager, taskA)
+    await notifyParentSessionForTest(manager, taskB)
+    await Promise.all([
+      flushPendingParentWakeForTest(manager, "parent-1"),
+      flushPendingParentWakeForTest(manager, "parent-1"),
+    ])
+
+    // then
+    expect(promptAsyncCalls).toHaveLength(0)
+    expect(getPendingParentWakes(manager).has("parent-1")).toBe(true)
+
+    // when
+    sessionStatuses["parent-1"] = { type: "idle" }
+    await Promise.all([
+      flushPendingParentWakeForTest(manager, "parent-1"),
+      flushPendingParentWakeForTest(manager, "parent-1"),
+    ])
+
     // then
     expect(promptAsyncCalls).toHaveLength(1)
-    expect(promptAsyncCalls[0]?.body.noReply).toBe(true)
     expect(JSON.stringify(promptAsyncCalls[0]?.body.parts)).toContain("ALL BACKGROUND TASKS COMPLETE")
     expect(getPendingParentWakes(manager).has("parent-1")).toBe(false)
   })
diff --git a/src/features/background-agent/parent-wake-notifier.ts b/src/features/background-agent/parent-wake-notifier.ts
index b16cf0a5a..c3800ac8d 100644
--- a/src/features/background-agent/parent-wake-notifier.ts
+++ b/src/features/background-agent/parent-wake-notifier.ts
@@ -77,19 +77,6 @@ type ToolWaitDeferralDecision = {
 
 type Unrefable = ReturnType<typeof setTimeout> & { unref?: () => unknown }
 
-const ACTIVE_TURN_COMPLETION_NOTIFICATION_MARKERS = [
-  "[BACKGROUND TASK COMPLETED]",
-  "[ALL BACKGROUND TASKS COMPLETE]",
-] as const
-
-function notificationAllowsActiveTurnDelivery(notification: string): boolean {
-  return ACTIVE_TURN_COMPLETION_NOTIFICATION_MARKERS.some((marker) => notification.includes(marker))
-}
-
-function pendingWakeAllowsActiveTurnDelivery(wake: PendingParentWake): boolean {
-  return wake.notifications.length > 0 && wake.notifications.every(notificationAllowsActiveTurnDelivery)
-}
-
 function unrefTimerHandle(handle: ReturnType<typeof setTimeout>): void {
   const maybeUnref = (handle as Unrefable).unref
   if (typeof maybeUnref === "function") {
@@ -179,8 +166,7 @@ export class ParentWakeNotifier {
     if (!latestWake) {
       return
     }
-    const canDeliverDuringActiveTurn = sessionActive && pendingWakeAllowsActiveTurnDelivery(latestWake)
-    if (sessionActive && !canDeliverDuringActiveTurn) {
+    if (sessionActive) {
       this.schedulePendingParentWakeFlush(sessionID)
       return
     }
@@ -234,12 +220,12 @@ export class ParentWakeNotifier {
         source: "background-agent-parent-wake",
         settleMs: 0,
         queueBehavior: "defer",
-        checkStatus: !canDeliverDuringActiveTurn,
+        checkStatus: true,
         checkToolState: !toolWaitDecision.skipPromptGateToolStateCheck,
         input: {
           path: { id: sessionID },
           body: {
-            noReply: canDeliverDuringActiveTurn ? true : !latestWake.shouldReply,
+            noReply: !latestWake.shouldReply,
             ...latestWake.promptContext,
             parts: [createInternalAgentTextPart(notificationContent)],
           },