feat: Add idle timeout to kill inactive sessions after 15 minutes (#1207)

1. Add 15-minute idle timeout that auto-kills sessions with no user activity
2. Track activity on permission responses and prompt cycles in AgentService
3. Send heartbeat pings every 5 minutes from TaskLogsPanel when viewing a task
4. Clean up idle-killed sessions in renderer SessionService (unsubscribe, remove state)
5. Clear all timeout handles on service teardown and session cleanup

Author: charlesvien

apps/code/src/main/services/agent/schemas.ts

@@ -183,11 +183,17 @@ export const subscribeSessionInput = z.object({
   taskRunId: z.string(),
 });
 
+// Record activity input — resets the idle timeout for the given session
+export const recordActivityInput = z.object({
+  taskRunId: z.string(),
+});
+
 // Agent events
 export const AgentServiceEvent = {
   SessionEvent: "session-event",
   PermissionRequest: "permission-request",
   SessionsIdle: "sessions-idle",
+  SessionIdleKilled: "session-idle-killed",
 } as const;
 
 export interface AgentSessionEventPayload {
@@ -203,10 +209,16 @@ export type PermissionRequestPayload = Omit<
   taskRunId: string;
 };
 
+export interface SessionIdleKilledPayload {
+  taskRunId: string;
+  taskId: string;
+}
+
 export interface AgentServiceEvents {
   [AgentServiceEvent.SessionEvent]: AgentSessionEventPayload;
   [AgentServiceEvent.PermissionRequest]: PermissionRequestPayload;
   [AgentServiceEvent.SessionsIdle]: undefined;
+  [AgentServiceEvent.SessionIdleKilled]: SessionIdleKilledPayload;
 }
 
 // Permission response input for tRPC

apps/code/src/main/services/agent/service.test.ts

@@ -51,8 +51,13 @@ const mockFetch = vi.hoisted(() => vi.fn());
 
 // --- Module mocks ---
 
+const mockPowerMonitor = vi.hoisted(() => ({
+  on: vi.fn(),
+}));
+
 vi.mock("electron", () => ({
   app: mockApp,
+  powerMonitor: mockPowerMonitor,
 }));
 
 vi.mock("../../utils/logger.js", () => ({
@@ -280,4 +285,145 @@ describe("AgentService", () => {
       );
     });
   });
+
+  describe("idle timeout", () => {
+    function injectSession(
+      svc: AgentService,
+      taskRunId: string,
+      overrides: Record<string, unknown> = {},
+    ) {
+      const sessions = (svc as unknown as { sessions: Map<string, unknown> })
+        .sessions;
+      sessions.set(taskRunId, {
+        taskRunId,
+        taskId: `task-for-${taskRunId}`,
+        repoPath: "/mock/repo",
+        agent: { cleanup: vi.fn().mockResolvedValue(undefined) },
+        clientSideConnection: {},
+        channel: `ch-${taskRunId}`,
+        createdAt: Date.now(),
+        lastActivityAt: Date.now(),
+        config: {},
+        needsRecreation: false,
+        promptPending: false,
+        ...overrides,
+      });
+    }
+
+    function getIdleTimeouts(svc: AgentService) {
+      return (
+        svc as unknown as {
+          idleTimeouts: Map<
+            string,
+            { handle: ReturnType<typeof setTimeout>; deadline: number }
+          >;
+        }
+      ).idleTimeouts;
+    }
+
+    beforeEach(() => {
+      vi.useFakeTimers();
+    });
+
+    afterEach(() => {
+      vi.useRealTimers();
+    });
+
+    it("recordActivity is a no-op for unknown sessions", () => {
+      service.recordActivity("unknown-run");
+      expect(getIdleTimeouts(service).size).toBe(0);
+    });
+
+    it("recordActivity sets a timeout for a known session", () => {
+      injectSession(service, "run-1");
+      service.recordActivity("run-1");
+      expect(getIdleTimeouts(service).has("run-1")).toBe(true);
+    });
+
+    it("recordActivity resets the timeout on subsequent calls", () => {
+      injectSession(service, "run-1");
+      service.recordActivity("run-1");
+      const firstDeadline = getIdleTimeouts(service).get("run-1")?.deadline;
+
+      vi.advanceTimersByTime(5 * 60 * 1000);
+      service.recordActivity("run-1");
+      const secondDeadline = getIdleTimeouts(service).get("run-1")?.deadline;
+
+      expect(secondDeadline).toBeGreaterThan(firstDeadline!);
+    });
+
+    it("kills idle session after timeout expires", () => {
+      injectSession(service, "run-1");
+      service.recordActivity("run-1");
+
+      vi.advanceTimersByTime(15 * 60 * 1000);
+
+      expect(service.emit).toHaveBeenCalledWith(
+        "session-idle-killed",
+        expect.objectContaining({ taskRunId: "run-1" }),
+      );
+    });
+
+    it("does not kill session if activity is recorded before timeout", () => {
+      injectSession(service, "run-1");
+      service.recordActivity("run-1");
+
+      vi.advanceTimersByTime(14 * 60 * 1000);
+      service.recordActivity("run-1");
+      vi.advanceTimersByTime(14 * 60 * 1000);
+
+      expect(service.emit).not.toHaveBeenCalledWith(
+        "session-idle-killed",
+        expect.anything(),
+      );
+    });
+
+    it("reschedules when promptPending is true at timeout", () => {
+      injectSession(service, "run-1", { promptPending: true });
+      service.recordActivity("run-1");
+
+      vi.advanceTimersByTime(15 * 60 * 1000);
+
+      expect(service.emit).not.toHaveBeenCalledWith(
+        "session-idle-killed",
+        expect.anything(),
+      );
+      expect(getIdleTimeouts(service).has("run-1")).toBe(true);
+    });
+
+    it("checkIdleDeadlines kills expired sessions on resume", () => {
+      injectSession(service, "run-1");
+      service.recordActivity("run-1");
+
+      const resumeHandler = mockPowerMonitor.on.mock.calls.find(
+        ([event]: string[]) => event === "resume",
+      )?.[1] as () => void;
+      expect(resumeHandler).toBeDefined();
+
+      vi.advanceTimersByTime(20 * 60 * 1000);
+      resumeHandler();
+
+      expect(service.emit).toHaveBeenCalledWith(
+        "session-idle-killed",
+        expect.objectContaining({ taskRunId: "run-1" }),
+      );
+    });
+
+    it("checkIdleDeadlines does not kill non-expired sessions", () => {
+      injectSession(service, "run-1");
+      service.recordActivity("run-1");
+
+      const resumeHandler = mockPowerMonitor.on.mock.calls.find(
+        ([event]: string[]) => event === "resume",
+      )?.[1] as () => void;
+
+      vi.advanceTimersByTime(5 * 60 * 1000);
+      resumeHandler();
+
+      expect(service.emit).not.toHaveBeenCalledWith(
+        "session-idle-killed",
+        expect.anything(),
+      );
+    });
+  });
 });

apps/code/src/main/services/agent/service.ts

@@ -23,7 +23,7 @@ import { getLlmGatewayUrl } from "@posthog/agent/posthog-api";
 import type { OnLogCallback } from "@posthog/agent/types";
 import { isAuthError } from "@shared/errors.js";
 import type { AcpMessage } from "@shared/types/session-events.js";
-import { app } from "electron";
+import { app, powerMonitor } from "electron";
 import { inject, injectable, preDestroy } from "inversify";
 import { MAIN_TOKENS } from "../../di/tokens.js";
 import { isDevBuild } from "../../utils/env.js";
@@ -252,10 +252,16 @@ interface PendingPermission {
 
 @injectable()
 export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
+  private static readonly IDLE_TIMEOUT_MS = 15 * 60 * 1000;
+
   private sessions = new Map<string, ManagedSession>();
   private currentToken: string | null = null;
   private pendingPermissions = new Map<string, PendingPermission>();
   private mockNodeReady = false;
+  private idleTimeouts = new Map<
+    string,
+    { handle: ReturnType<typeof setTimeout>; deadline: number }
+  >();
   private processTracking: ProcessTrackingService;
   private sleepService: SleepService;
   private fsService: FsService;
@@ -276,6 +282,8 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
     this.sleepService = sleepService;
     this.fsService = fsService;
     this.posthogPluginService = posthogPluginService;
+
+    powerMonitor.on("resume", () => this.checkIdleDeadlines());
   }
 
   public updateToken(newToken: string): void {
@@ -349,6 +357,7 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
     });
 
     this.pendingPermissions.delete(key);
+    this.recordActivity(taskRunId);
   }
 
   /**
@@ -376,6 +385,7 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
     });
 
     this.pendingPermissions.delete(key);
+    this.recordActivity(taskRunId);
   }
 
   /**
@@ -392,6 +402,48 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
     return false;
   }
 
+  public recordActivity(taskRunId: string): void {
+    if (!this.sessions.has(taskRunId)) return;
+
+    const existing = this.idleTimeouts.get(taskRunId);
+    if (existing) clearTimeout(existing.handle);
+
+    const deadline = Date.now() + AgentService.IDLE_TIMEOUT_MS;
+    const handle = setTimeout(() => {
+      this.killIdleSession(taskRunId);
+    }, AgentService.IDLE_TIMEOUT_MS);
+
+    this.idleTimeouts.set(taskRunId, { handle, deadline });
+  }
+
+  private killIdleSession(taskRunId: string): void {
+    const session = this.sessions.get(taskRunId);
+    if (!session) return;
+    if (session.promptPending) {
+      this.recordActivity(taskRunId);
+      return;
+    }
+    log.info("Killing idle session", { taskRunId, taskId: session.taskId });
+    this.emit(AgentServiceEvent.SessionIdleKilled, {
+      taskRunId,
+      taskId: session.taskId,
+    });
+    this.cleanupSession(taskRunId).catch((err) => {
+      log.error("Failed to cleanup idle session", { taskRunId, err });
+    });
+  }
+
+  private checkIdleDeadlines(): void {
+    const now = Date.now();
+    const expired = [...this.idleTimeouts.entries()].filter(
+      ([, { deadline }]) => now >= deadline,
+    );
+    for (const [taskRunId, { handle }] of expired) {
+      clearTimeout(handle);
+      this.killIdleSession(taskRunId);
+    }
+  }
+
   private getToken(fallback: string): string {
     return this.currentToken || fallback;
   }
@@ -786,6 +838,7 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
       };
 
       this.sessions.set(taskRunId, session);
+      this.recordActivity(taskRunId);
       if (isRetry) {
         log.info("Session created after auth retry", { taskRunId });
       }
@@ -912,6 +965,7 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
 
     session.lastActivityAt = Date.now();
     session.promptPending = true;
+    this.recordActivity(sessionId);
     this.sleepService.acquire(sessionId);
 
     const promptJson = JSON.stringify(finalPrompt);
@@ -947,6 +1001,8 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
       throw err;
     } finally {
       session.promptPending = false;
+      session.lastActivityAt = Date.now();
+      this.recordActivity(sessionId);
       this.sleepService.release(sessionId);
 
       if (!this.hasActiveSessions()) {
@@ -1138,6 +1194,8 @@ For git operations while detached:
 
   @preDestroy()
   async cleanupAll(): Promise<void> {
+    for (const { handle } of this.idleTimeouts.values()) clearTimeout(handle);
+    this.idleTimeouts.clear();
     const sessionIds = Array.from(this.sessions.keys());
     log.info("Cleaning up all agent sessions", {
       sessionCount: sessionIds.length,
@@ -1224,6 +1282,12 @@ For git operations while detached:
       }
 
       this.sessions.delete(taskRunId);
+
+      const timeout = this.idleTimeouts.get(taskRunId);
+      if (timeout) {
+        clearTimeout(timeout.handle);
+        this.idleTimeouts.delete(taskRunId);
+      }
     }
   }
 

apps/code/src/main/trpc/routers/agent.ts

@@ -14,6 +14,7 @@ import {
   promptInput,
   promptOutput,
   reconnectSessionInput,
+  recordActivityInput,
   respondToPermissionInput,
   sessionResponseSchema,
   setConfigOptionInput,
@@ -183,6 +184,20 @@ export const agentRouter = router({
     log.info("All sessions reset successfully");
   }),
 
+  recordActivity: publicProcedure
+    .input(recordActivityInput)
+    .mutation(({ input }) => getService().recordActivity(input.taskRunId)),
+
+  onSessionIdleKilled: publicProcedure.subscription(async function* (opts) {
+    const service = getService();
+    for await (const event of service.toIterable(
+      AgentServiceEvent.SessionIdleKilled,
+      { signal: opts.signal },
+    )) {
+      yield event;
+    }
+  }),
+
   getGatewayModels: publicProcedure
     .input(getGatewayModelsInput)
     .output(getGatewayModelsOutput)

apps/code/src/renderer/features/sessions/service/service.test.ts

@@ -15,6 +15,7 @@ const mockTrpcAgent = vi.hoisted(() => ({
   cancelPermission: { mutate: vi.fn() },
   onSessionEvent: { subscribe: vi.fn() },
   onPermissionRequest: { subscribe: vi.fn() },
+  onSessionIdleKilled: { subscribe: vi.fn(() => ({ unsubscribe: vi.fn() })) },
   resetAll: { mutate: vi.fn().mockResolvedValue(undefined) },
 }));