refactor(background-agent): optimize cache timer lifecycle and result handling

Improve cache timer management in background agent manager and update result handler to properly handle cache state transitions

src/features/background-agent/manager.test.ts

@@ -2157,6 +2157,67 @@ describe("BackgroundManager.completionTimers - Memory Leak Fix", () => {
     manager.shutdown()
   })
 
+  test("should start cleanup timers only after all tasks complete", async () => {
+    // given
+    const client = {
+      session: {
+        prompt: async () => ({}),
+        abort: async () => ({}),
+        messages: async () => ({ data: [] }),
+      },
+    }
+    const manager = new BackgroundManager({ client, directory: tmpdir() } as unknown as PluginInput)
+    const taskA: BackgroundTask = {
+      id: "task-timer-a",
+      sessionID: "session-timer-a",
+      parentSessionID: "parent-session",
+      parentMessageID: "msg-a",
+      description: "Task A",
+      prompt: "test",
+      agent: "explore",
+      status: "completed",
+      startedAt: new Date(),
+      completedAt: new Date(),
+    }
+    const taskB: BackgroundTask = {
+      id: "task-timer-b",
+      sessionID: "session-timer-b",
+      parentSessionID: "parent-session",
+      parentMessageID: "msg-b",
+      description: "Task B",
+      prompt: "test",
+      agent: "explore",
+      status: "completed",
+      startedAt: new Date(),
+      completedAt: new Date(),
+    }
+    getTaskMap(manager).set(taskA.id, taskA)
+    getTaskMap(manager).set(taskB.id, taskB)
+    ;(manager as unknown as { pendingByParent: Map<string, Set<string>> }).pendingByParent.set(
+      "parent-session",
+      new Set([taskA.id, taskB.id])
+    )
+
+    // when
+    await (manager as unknown as { notifyParentSession: (task: BackgroundTask) => Promise<void> })
+      .notifyParentSession(taskA)
+
+    // then
+    const completionTimers = getCompletionTimers(manager)
+    expect(completionTimers.size).toBe(0)
+
+    // when
+    await (manager as unknown as { notifyParentSession: (task: BackgroundTask) => Promise<void> })
+      .notifyParentSession(taskB)
+
+    // then
+    expect(completionTimers.size).toBe(2)
+    expect(completionTimers.has(taskA.id)).toBe(true)
+    expect(completionTimers.has(taskB.id)).toBe(true)
+
+    manager.shutdown()
+  })
+
   test("should clear all completion timers on shutdown", () => {
     // given
     const manager = createBackgroundManager()

src/features/background-agent/manager.ts

@@ -1013,9 +1013,11 @@ export class BackgroundManager {
     const errorInfo = task.error ? `\n**Error:** ${task.error}` : ""
     
     let notification: string
+    let completedTasks: BackgroundTask[] = []
     if (allComplete) {
-      const completedTasks = Array.from(this.tasks.values())
+      completedTasks = Array.from(this.tasks.values())
         .filter(t => t.parentSessionID === task.parentSessionID && t.status !== "running" && t.status !== "pending")
+      const completedTasksText = completedTasks
         .map(t => `- \`${t.id}\`: ${t.description}`)
         .join("\n")
 
@@ -1023,7 +1025,7 @@ export class BackgroundManager {
 [ALL BACKGROUND TASKS COMPLETE]
 
 **Completed:**
-${completedTasks || `- \`${task.id}\`: ${task.description}`}
+${completedTasksText || `- \`${task.id}\`: ${task.description}`}
 
 Use \`background_output(task_id="<id>")\` to retrieve each result.
 </system-reminder>`
@@ -1092,16 +1094,25 @@ Use \`background_output(task_id="${task.id}")\` to retrieve this result when rea
       log("[background-agent] Failed to send notification:", error)
     }
 
-    const taskId = task.id
-    const timer = setTimeout(() => {
-      this.completionTimers.delete(taskId)
-      if (this.tasks.has(taskId)) {
-        this.clearNotificationsForTask(taskId)
-        this.tasks.delete(taskId)
-        log("[background-agent] Removed completed task from memory:", taskId)
+    if (allComplete) {
+      for (const completedTask of completedTasks) {
+        const taskId = completedTask.id
+        const existingTimer = this.completionTimers.get(taskId)
+        if (existingTimer) {
+          clearTimeout(existingTimer)
+          this.completionTimers.delete(taskId)
+        }
+        const timer = setTimeout(() => {
+          this.completionTimers.delete(taskId)
+          if (this.tasks.has(taskId)) {
+            this.clearNotificationsForTask(taskId)
+            this.tasks.delete(taskId)
+            log("[background-agent] Removed completed task from memory:", taskId)
+          }
+        }, TASK_CLEANUP_DELAY_MS)
+        this.completionTimers.set(taskId, timer)
       }
-    }, TASK_CLEANUP_DELAY_MS)
-    this.completionTimers.set(taskId, timer)
+    }
   }
 
   private formatDuration(start: Date, end?: Date): string {

src/features/background-agent/result-handler.ts

@@ -174,9 +174,11 @@ export async function notifyParentSession(
   const errorInfo = task.error ? `\n**Error:** ${task.error}` : ""
   
   let notification: string
+  let completedTasks: BackgroundTask[] = []
   if (allComplete) {
-    const completedTasks = Array.from(state.tasks.values())
+    completedTasks = Array.from(state.tasks.values())
       .filter(t => t.parentSessionID === task.parentSessionID && t.status !== "running" && t.status !== "pending")
+    const completedTasksText = completedTasks
       .map(t => `- \`${t.id}\`: ${t.description}`)
       .join("\n")
 
@@ -184,7 +186,7 @@ export async function notifyParentSession(
 [ALL BACKGROUND TASKS COMPLETE]
 
 **Completed:**
-${completedTasks || `- \`${task.id}\`: ${task.description}`}
+${completedTasksText || `- \`${task.id}\`: ${task.description}`}
 
 Use \`background_output(task_id="<id>")\` to retrieve each result.
 </system-reminder>`
@@ -256,14 +258,19 @@ Use \`background_output(task_id="${task.id}")\` to retrieve this result when rea
     log("[background-agent] Failed to send notification:", error)
   }
 
-  const taskId = task.id
-  const timer = setTimeout(() => {
-    state.completionTimers.delete(taskId)
-    if (state.tasks.has(taskId)) {
-      state.clearNotificationsForTask(taskId)
-      state.tasks.delete(taskId)
-      log("[background-agent] Removed completed task from memory:", taskId)
+  if (allComplete) {
+    for (const completedTask of completedTasks) {
+      const taskId = completedTask.id
+      state.clearCompletionTimer(taskId)
+      const timer = setTimeout(() => {
+        state.completionTimers.delete(taskId)
+        if (state.tasks.has(taskId)) {
+          state.clearNotificationsForTask(taskId)
+          state.tasks.delete(taskId)
+          log("[background-agent] Removed completed task from memory:", taskId)
+        }
+      }, TASK_CLEANUP_DELAY_MS)
+      state.setCompletionTimer(taskId, timer)
     }
-  }, TASK_CLEANUP_DELAY_MS)
-  state.setCompletionTimer(taskId, timer)
+  }
 }