Report canceled child tasks and wait for replacement tasks to finish (#6660)

* fix(server): report canceled child turns to their callers

* fix(server): wait for replacement child tasks before notifying callers

A displaced turn emits cancellation while its replacement is still running. Notify on terminal events only once the child becomes idle, so Stop and Reload report cancellation while replacement prompts produce one eventual outcome.

Co-authored-by: 见安 <73627805+Mar-garet@users.noreply.github.com>

* test(server): remove debug output from cancellation regressions

---------

Co-authored-by: 见安 <73627805+Mar-garet@users.noreply.github.com>
Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>

packages/server/src/server/agent/agent-prompt.test.ts

@@ -222,6 +222,11 @@ function createFinishNotificationScenario(
         type: "agent_state",
         agent: childAgent,
       });
+      subscriber?.({
+        type: "agent_stream",
+        agentId: "child-agent",
+        event: { type: "turn_completed", provider: "codex" },
+      });
     },
     async finishChildAndReadParentPrompt() {
       const parentPrompt = new Promise<string>((resolve) => {
@@ -540,6 +545,11 @@ it("does not notify archived callers", async () => {
     type: "agent_state",
     agent: childAgent,
   });
+  subscriber?.({
+    type: "agent_stream",
+    agentId: "child-agent",
+    event: { type: "turn_completed", provider: "codex" },
+  });
 
   await vi.waitFor(() => {
     expect(agentStorageGetSpy).toHaveBeenCalledWith("caller-agent");

packages/server/src/server/agent/agent-prompt.ts

@@ -407,13 +407,20 @@ export interface SetupFinishNotificationParams {
   logger: Logger;
 }
 
-type FinishNotificationReason = "finished" | "errored" | "needs permission" | "was closed";
+type FinishNotificationReason =
+  | "finished"
+  | "errored"
+  | "needs permission"
+  | "was closed"
+  | "was canceled";
 
 const finishNotificationEvents = {
   finished: "finished",
   errored: "errored",
   "needs permission": "permission-required",
   "was closed": "closed",
+  // Use the existing failure event so older clients still parse agent-message metadata.
+  "was canceled": "errored",
 } as const;
 
 const FINISH_NOTIFICATION_MESSAGE_LIMIT = 4000;
@@ -568,10 +575,8 @@ export function setupFinishNotification(params: SetupFinishNotificationParams):
       notifySafely("errored");
       return;
     }
-    if (agent.lifecycle === "idle" && hasSeenRunning) {
-      notifySafely("finished");
-      return;
-    }
+    // Idle is published before the terminal stream event for both completion
+    // and cancellation. Let that event identify the outcome instead.
     if (agent.lifecycle === "closed") {
       notifySafely("was closed");
       return;
@@ -600,6 +605,18 @@ export function setupFinishNotification(params: SetupFinishNotificationParams):
         return;
       }
 
+      if (event.event.type === "turn_completed" || event.event.type === "turn_canceled") {
+        // Replacing a turn keeps the child running through the displaced turn's
+        // cancellation. The task settles only when the child becomes idle.
+        if (agentManager.getAgent(childAgentId)?.lifecycle !== "idle") return;
+        if (event.event.type === "turn_completed" && hasSeenRunning) {
+          notifySafely("finished");
+        } else if (event.event.type === "turn_canceled" && hasSeenTurn) {
+          notifySafely("was canceled");
+        }
+        return;
+      }
+
       if (event.event.type === "permission_requested") {
         // A permission pause is an intermediate checkpoint. Forget the run
         // observed before it so an idle state during follow-up startup cannot

packages/server/src/server/agent/mcp-parity.e2e.test.ts

@@ -12,6 +12,8 @@ import { createTestPaseoDaemon, type TestPaseoDaemon } from "../test-utils/paseo
 import { createTestAgentClients } from "../test-utils/fake-agent-client.js";
 import type { AgentClient, AgentProvider, AgentSessionConfig } from "./agent-sdk-types.js";
 import { PARENT_AGENT_ID_LABEL } from "@getpaseo/protocol/agent-labels";
+import { DaemonClient } from "../test-utils/daemon-client.js";
+import { parseAgentMessage } from "./agent-messages/index.js";
 
 interface StructuredContent {
   [key: string]: unknown;
@@ -311,6 +313,167 @@ afterAll(async () => {
 });
 
 describe("Suite A: Core Fixes", () => {
+  test.each([
+    ["Stop", "cancelAgent"],
+    ["Reload", "refreshAgent"],
+  ] as const)(
+    "%s tells the parent that a watched child was canceled",
+    async (_action, method) => {
+      let releaseChild!: () => void;
+      let childReachedGate!: () => void;
+      const heldTurn = new Promise<void>((resolve) => {
+        releaseChild = resolve;
+      });
+      const childAtGate = new Promise<void>((resolve) => {
+        childReachedGate = resolve;
+      });
+      const parentPrompts: string[] = [];
+      const daemon = await createTestPaseoDaemon({
+        agentClients: createTestAgentClients({
+          onStartTurn(prompt, config) {
+            if (config.title === "Watching parent" && typeof prompt === "string")
+              parentPrompts.push(prompt);
+          },
+          async beforeTurnComplete(prompt) {
+            if (
+              typeof prompt === "string" &&
+              parseAgentMessage(prompt).text === "Hold this child turn"
+            ) {
+              childReachedGate();
+              await heldTurn;
+            }
+          },
+        }),
+      });
+      const client = new DaemonClient({
+        url: `ws://127.0.0.1:${daemon.port}/ws`,
+        appVersion: "0.11.2",
+      });
+      let mcp: McpClient | undefined;
+      let unsubscribe: (() => void) | undefined;
+      try {
+        await client.connect();
+        await client.fetchAgents({ subscribe: {} });
+        const parent = await client.createAgent({
+          provider: "claude",
+          cwd: daemon.paseoHome,
+          title: "Watching parent",
+          modeId: "bypassPermissions",
+        });
+        mcp = await createMcpClient(
+          buildExpectedAgentMcpUrl({ host: "127.0.0.1", port: daemon.port, agentId: parent.id }),
+        );
+        const created = await callToolStructured(mcp, "create_agent", {
+          relationship: { kind: "subagent" },
+          workspace: { kind: "current" },
+          title: "Watched child",
+          provider: "codex/gpt-5.4",
+          initialPrompt: "Hold this child turn",
+          notifyOnFinish: true,
+          settings: { modeId: "full-access" },
+        });
+        const childId = str(created.agentId);
+        await childAtGate;
+        expect(daemon.daemon.agentManager.getAgent(childId)?.lifecycle).toBe("running");
+        const terminalEvents: string[] = [];
+        unsubscribe = daemon.daemon.agentManager.subscribe(
+          (event) => {
+            if (
+              event.type === "agent_stream" &&
+              event.agentId === childId &&
+              (event.event.type === "turn_completed" || event.event.type === "turn_canceled")
+            )
+              terminalEvents.push(event.event.type);
+          },
+          { agentId: childId, replayState: false },
+        );
+
+        await client[method](childId);
+        await waitFor({
+          timeoutMs: 10000,
+          label: "parent cancellation notification",
+          check: () => (parentPrompts.length === 1 ? true : null),
+        });
+        const notification = parseAgentMessage(parentPrompts[0]);
+        expect(terminalEvents).toEqual(["turn_canceled"]);
+        expect(notification.source).toEqual({
+          kind: "agent-notification",
+          agentId: childId,
+          title: "Watched child",
+          event: "errored",
+        });
+        expect(notification.text).toContain(`Agent ${childId} (Watched child) was canceled.`);
+        expect(notification.text).not.toContain("finished.");
+        await waitFor({
+          timeoutMs: 10000,
+          label: "parent notification turn drained",
+          check: () =>
+            daemon.daemon.agentManager.getAgent(parent.id)?.lifecycle === "idle" ? true : null,
+        });
+        expect(parentPrompts).toHaveLength(1);
+      } finally {
+        releaseChild();
+        unsubscribe?.();
+        await mcp?.close();
+        await client.close();
+        await daemon.close();
+      }
+    },
+    30000,
+  );
+
+  test.each([
+    { outcome: "finished", prompt: "say done and stop", status: "idle" },
+    { outcome: "errored", prompt: "Emit a turn failure", status: "error" },
+  ])(
+    "a watched child still reports $outcome after send_agent_prompt",
+    async ({ outcome, prompt, status }) => {
+      const childId = await createChildAgent({
+        title: "Follow-up child",
+        settings: { modeId: "bypassPermissions" },
+      });
+      try {
+        await waitFor({
+          timeoutMs: 10000,
+          label: "initial child turn completed",
+          check: () =>
+            daemonHandle.daemon.agentManager.getAgent(childId)?.lifecycle === "idle" ? true : null,
+        });
+        await callToolStructured(agentScopedClient, "send_agent_prompt", {
+          agentId: childId,
+          prompt,
+          notifyOnFinish: true,
+        });
+        const notifications = await waitFor({
+          timeoutMs: 10000,
+          label: `${outcome} notification`,
+          check: () => {
+            const items = daemonHandle.daemon.agentManager
+              .getTimeline(parentAgentId)
+              .filter(
+                (item) => item.type === "tool_call" && item.agentMessage?.sender.id === childId,
+              );
+            return items.length > 0 ? items : null;
+          },
+        });
+        expect(notifications).toEqual([
+          expect.objectContaining({
+            type: "tool_call",
+            agentMessage: {
+              event: outcome,
+              sender: { id: childId, title: "Follow-up child" },
+              text: expect.stringContaining(`(Follow-up child) ${outcome}.`),
+            },
+          }),
+        ]);
+        expect(daemonHandle.daemon.agentManager.getAgent(childId)?.lifecycle).toBe(status);
+      } finally {
+        await archiveAgentIfPresent(childId);
+      }
+    },
+    30000,
+  );
+
   test("AGENT_WAIT_TIMEOUT_MS is 30000", () => {
     expect(AGENT_WAIT_TIMEOUT_MS).toBe(30_000);
   });

packages/server/src/server/agent/mcp-server.test.ts

@@ -4359,6 +4359,10 @@ describe("send_agent_prompt MCP tool", () => {
       await vi.waitFor(() => expect(finishNotifications()).not.toHaveLength(0));
       await new Promise((resolve) => setTimeout(resolve, 100));
       expect(finishNotifications()).toHaveLength(1);
+      expect(parentClient.sessions[0]!.prompts).toHaveLength(1);
+      expect(parseAgentMessage(parentClient.sessions[0]!.prompts[0])).toMatchObject({
+        source: { kind: "agent-notification", agentId: childId, event: "finished" },
+      });
     } finally {
       await removeAgentStateDir(agentManager, storage, workdir);
     }