fix: report task stop reasons to the model (#1781)

* fix: report task stop reasons to the model

* chore: add task stop reason changeset

.changeset/report-task-stop-reasons.md

@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/kimi-code": patch
+---
+
+Report when users stop tasks and preserve other stop reasons in model context.

packages/agent-core-v2/src/agent/rpc/rpcService.ts

@@ -241,6 +241,10 @@ export class AgentRPCService implements IAgentRPCService {
   }
 
   stopTask(payload: StopTaskPayload): void {
+    if (payload.reason === undefined) {
+      void this.tasks.stopByUser(payload.taskId);
+      return;
+    }
     void this.tasks.stop(payload.taskId, payload.reason);
   }
 

packages/agent-core-v2/src/agent/task/task.ts

@@ -92,6 +92,7 @@ export interface IAgentTaskService {
   suppressTerminalNotification(taskId: string): Promise<void>;
   detach(taskId: string): AgentTaskInfo | undefined;
   stop(taskId: string, reason?: string): Promise<AgentTaskInfo | undefined>;
+  stopByUser(taskId: string): Promise<AgentTaskInfo | undefined>;
   stopAll(reason?: string): Promise<readonly AgentTaskInfo[]>;
   stopAllOnExit(reason: string): Promise<readonly AgentTaskInfo[]>;
   wait(

packages/agent-core-v2/src/agent/task/taskService.ts

@@ -36,7 +36,10 @@ import { LifecycleScope, registerScopedService } from '#/_base/di/scope';
 import type { ContentPart } from '#/app/llmProtocol/message';
 
 import { Disposable } from '#/_base/di/lifecycle';
-import { abortable } from '#/_base/utils/abort';
+import {
+  abortable,
+  userCancellationReason,
+} from '#/_base/utils/abort';
 import { escapeXml, escapeXmlAttr } from '#/_base/utils/xml-escape';
 import { IEventBus } from '#/app/event/eventBus';
 import type { ContextMessage, TaskOrigin } from '#/agent/contextMemory/types';
@@ -167,7 +170,6 @@ function outputLimitReason(): string {
 
 const SIGTERM_GRACE_MS = 5_000;
 const TASK_ID_ALPHABET = '0123456789abcdefghijklmnopqrstuvwxyz';
-const USER_INTERRUPT_REASON = 'Interrupted by user';
 const SESSION_CLOSED_REASON = 'Session closed';
 const NOTIFICATION_FALLBACK_PREVIEW_BYTES = 3_000;
 const ACTIVE_BACKGROUND_TASK_INJECTION_VARIANT = 'background_task_status';
@@ -625,6 +627,17 @@ export class AgentTaskService extends Disposable implements IAgentTaskService {
     });
   }
 
+  async stopByUser(taskId: string): Promise<AgentTaskInfo | undefined> {
+    const entry = this.tasks.get(taskId);
+    if (entry === undefined) return undefined;
+    const reason = userCancellationReason();
+    return this.terminateWithGrace(entry, {
+      stopReason: reason.message,
+      abortReason: reason,
+      finalStatus: 'killed',
+    });
+  }
+
   private async terminateWithGrace(
     entry: ManagedTask,
     options: {
@@ -1098,8 +1111,9 @@ export class AgentTaskService extends Disposable implements IAgentTaskService {
 
     const abortFromSignal = (): void => {
       if (this.isDetached(entry)) return;
+      const userReason = userCancellationReason();
       void this.terminateWithGrace(entry, {
-        stopReason: USER_INTERRUPT_REASON,
+        stopReason: userReason.message,
         abortReason: signal.reason,
         finalStatus: 'killed',
       });
@@ -1229,9 +1243,11 @@ function buildAgentTaskNotificationBody(info: AgentTaskInfo): string {
   const baseLine =
     info.status === 'timed_out'
       ? `${info.description} timed out.`
-      : info.stopReason
-        ? `${info.description} ${info.status === 'killed' ? 'was killed' : info.status}: ${info.stopReason}.`
-        : `${info.description} ${info.status}.`;
+      : info.status === 'killed' && isSerializedUserCancellation(info.stopReason)
+        ? `${info.description} was stopped by user.`
+        : info.stopReason
+          ? `${info.description} ${info.status === 'killed' ? 'was stopped' : info.status}. Reason: ${info.stopReason}`
+          : `${info.description} ${info.status}.`;
 
   if (info.kind !== 'agent') return baseLine;
   if (info.status === 'completed') return baseLine;
@@ -1263,6 +1279,10 @@ function normalizeReason(reason: string | undefined): string | undefined {
   return trimmed === undefined || trimmed.length === 0 ? undefined : trimmed;
 }
 
+function isSerializedUserCancellation(reason: string | undefined): boolean {
+  return reason === userCancellationReason().message;
+}
+
 function createForegroundRelease(): ForegroundRelease {
   let resolve!: (reason: ForegroundTaskReleaseReason) => void;
   const promise = new Promise<ForegroundTaskReleaseReason>((done) => {

packages/agent-core-v2/src/os/backends/node-local/tools/bash.ts

@@ -50,6 +50,7 @@ import { registerTool } from '#/agent/toolRegistry/toolContribution';
 import { toInputJsonSchema } from '#/tool/input-schema';
 import { literalRulePattern, matchesGlobRuleSubject } from '#/tool/rule-match';
 import { renderPrompt } from '#/_base/utils/render-prompt';
+import { userCancellationReason } from '#/_base/utils/abort';
 import bashDescriptionTemplate from './bash.md?raw';
 import { ProcessTask } from './process-task';
 
@@ -58,7 +59,6 @@ const DEFAULT_TIMEOUT_S = 60;
 const MAX_TIMEOUT_S = 5 * 60;
 const DEFAULT_BACKGROUND_TIMEOUT_S = 10 * 60;
 const MAX_BACKGROUND_TIMEOUT_S = 24 * 60 * 60;
-const USER_INTERRUPT_REASON = 'Interrupted by user';
 
 export const BashInputSchema = z
   .object({
@@ -395,8 +395,11 @@ export class BashTool implements BuiltinTool<BashInput> {
       result = builder.error(`Command killed by timeout (${timeoutLabel})`, {
         brief: `Killed by timeout (${timeoutLabel})`,
       });
-    } else if (current?.status === 'killed' && current.stopReason === USER_INTERRUPT_REASON) {
-      result = builder.error(USER_INTERRUPT_REASON, { brief: USER_INTERRUPT_REASON });
+    } else if (
+      current?.status === 'killed' &&
+      current.stopReason === userCancellationReason().message
+    ) {
+      result = builder.error('Interrupted by user', { brief: 'Interrupted by user' });
     } else if (
       (current?.status === 'failed' || current?.status === 'killed') &&
       current.stopReason !== undefined

packages/agent-core-v2/src/session/subagent/tools/agent.ts

@@ -17,7 +17,11 @@
 import { z } from 'zod';
 
 import type { IAgentScopeHandle } from '#/_base/di/scope';
-import { isUserCancellation } from '#/_base/utils/abort';
+import {
+  isAbortError,
+  isUserCancellation,
+  userCancellationReason,
+} from '#/_base/utils/abort';
 import { toInputJsonSchema } from '#/tool/input-schema';
 import { matchesGlobRuleSubject } from '#/tool/rule-match';
 import {
@@ -29,7 +33,6 @@ import { IAgentPermissionModeService } from '#/agent/permissionMode/permissionMo
 import { IAgentScopeContext } from '#/agent/scopeContext/scopeContext';
 import { IAgentLoopService } from '#/agent/loop/loop';
 import { IAgentUserToolService } from '#/agent/userTool/userTool';
-import { isAbortError } from '#/_base/utils/abort';
 import {
   ToolAccesses,
   type BuiltinTool,
@@ -127,7 +130,8 @@ const BACKGROUND_AGENT_UNAVAILABLE =
 const RESUME_WITH_TYPE_UNAVAILABLE =
   'Cannot set subagent_type when resuming an existing agent. Resume by agent id only.';
 const USER_INTERRUPTED_SUBAGENT_MESSAGE =
-  "The user manually interrupted this subagent (and any sibling agents launched alongside it). This was a deliberate user action, not a system error, a timeout, or a capacity/concurrency limit. Do not retry automatically or speculate about why it failed — wait for the user's next instruction.";
+  'The subagent was stopped before it finished by user.';
+const SUBAGENT_STOPPED_MESSAGE = 'The subagent was stopped before it finished.';
 
 
 export class AgentTool implements BuiltinTool<AgentToolInput> {
@@ -428,11 +432,7 @@ export class AgentTool implements BuiltinTool<AgentToolInput> {
     const timedOut = info?.status === 'timed_out';
     const message = timedOut
       ? `Agent timed out after ${formatSubagentTimeoutDescription(timeoutMs)}.`
-      : info?.stopReason === 'Interrupted by user'
-        ? USER_INTERRUPTED_SUBAGENT_MESSAGE
-        : info?.stopReason !== undefined
-          ? info.stopReason
-          : 'The subagent was stopped before it finished.';
+      : formatSubagentStoppedMessage(info?.stopReason);
     return {
       output: formatForegroundAgentFailure(handle, message, timedOut),
       isError: true,
@@ -515,6 +515,19 @@ function formatForegroundAgentFailure(
 
 function launchErrorMessage(error: unknown, signal: AbortSignal): string {
   if (isUserCancellation(signal.reason)) return USER_INTERRUPTED_SUBAGENT_MESSAGE;
-  if (isAbortError(error)) return 'The subagent was stopped before it finished.';
+  if (isAbortError(error)) return formatSubagentStoppedMessage(errorMessage(signal.reason));
   return error instanceof Error ? error.message : String(error);
 }
+
+function formatSubagentStoppedMessage(reason: string | undefined): string {
+  const normalized = reason?.trim();
+  if (normalized === userCancellationReason().message) return USER_INTERRUPTED_SUBAGENT_MESSAGE;
+  if (normalized === undefined || normalized.length === 0) return SUBAGENT_STOPPED_MESSAGE;
+  return `${SUBAGENT_STOPPED_MESSAGE} Reason: ${normalized}`;
+}
+
+function errorMessage(error: unknown): string | undefined {
+  if (typeof error === 'string') return error;
+  if (error instanceof Error) return error.message;
+  return undefined;
+}

packages/agent-core-v2/test/agent/task/rpc-events.test.ts

@@ -502,7 +502,7 @@ describe('AgentTaskService — notification delivery', () => {
     const { agent, ctx, manager } = createAgentTaskService();
     const taskId = registerProcess(manager, pendingProcess(), 'sleep 60', 'long shell task');
 
-    await manager.stop(taskId);
+    await manager.stopByUser(taskId);
 
     await vi.waitFor(() => {
       expect(notifiedCount(ctx)).toBe(1);
@@ -516,9 +516,7 @@ describe('AgentTaskService — notification delivery', () => {
       status: 'killed',
       notificationId: `task:${taskId}:killed`,
     });
-    expect(message.content[0]!.text).toContain(
-      'Background process killed',
-    );
+    expect(message.content[0]!.text).toContain('long shell task was stopped by user.');
   });
 
   it('TaskStopTool suppresses the real terminal notification for model-requested stops', async () => {

packages/agent-core-v2/test/agent/task/taskManager.test.ts

@@ -477,7 +477,7 @@ describe('AgentTaskService', () => {
     expect(killSpy).toHaveBeenCalledWith('SIGTERM');
     expect(manager.getTask(taskId)).toMatchObject({
       status: 'killed',
-      stopReason: 'Interrupted by user',
+      stopReason: 'Aborted by the user',
     });
   });
 
@@ -507,7 +507,7 @@ describe('AgentTaskService', () => {
     const info = await manager.wait(taskId);
     expect(info).toMatchObject({
       status: 'killed',
-      stopReason: 'Interrupted by user',
+      stopReason: 'Aborted by the user',
     });
     expect(isUserCancellation(subagentController.signal.reason)).toBe(true);
   });

packages/agent-core-v2/test/agent/task/tools/task-tools.test.ts

@@ -220,6 +220,10 @@ class FakeTaskService implements IAgentTaskService {
     return entry.info;
   }
 
+  async stopByUser(taskId: string): Promise<AgentTaskInfo | undefined> {
+    return this.stop(taskId, 'Aborted by the user');
+  }
+
   async stopAll(reason?: string): Promise<readonly AgentTaskInfo[]> {
     const stopped = await Promise.all(
       Array.from(this.entries.keys()).map((taskId) => this.stop(taskId, reason)),

packages/agent-core-v2/test/os/backends/node-local/tools/bash.test.ts

@@ -28,6 +28,7 @@ import {
   type RegisterAgentTaskOptions,
 } from '#/agent/task/task';
 import type { AgentTaskSettlement } from '#/agent/task/types';
+import { userCancellationReason } from '#/_base/utils/abort';
 import type { IConfigService } from '#/app/config/config';
 import { ProcessTask } from '#/os/backends/node-local/tools/process-task';
 import type { IHostEnvironment } from '#/os/interface/hostEnvironment';
@@ -313,7 +314,6 @@ const TERMINAL_STATUSES: ReadonlySet<AgentTaskStatus> = new Set([
   'lost',
 ]);
 const SIGTERM_GRACE_MS = 5_000;
-const USER_INTERRUPT_REASON = 'Interrupted by user';
 const TASK_ID_ALPHABET = '0123456789abcdefghijklmnopqrstuvwxyz';
 
 interface ForegroundRelease {
@@ -542,7 +542,7 @@ function createFakeTaskService(options: { maxRunningTasks?: number } = {}): {
         const signal = registerOptions.signal;
         const abortFromSignal = (): void => {
           if (entry.foregroundRelease === undefined) return;
-          void stopEntry(entry, USER_INTERRUPT_REASON);
+          void stopEntry(entry, userCancellationReason().message);
         };
         if (signal.aborted) {
           abortFromSignal();
@@ -612,6 +612,10 @@ function createFakeTaskService(options: { maxRunningTasks?: number } = {}): {
       return stopEntry(entry, reason);
     },
 
+    async stopByUser(taskId: string): Promise<AgentTaskInfo | undefined> {
+      return service.stop(taskId, userCancellationReason().message);
+    },
+
     async stopAll(reason?: string): Promise<readonly AgentTaskInfo[]> {
       const results = await Promise.all(
         Array.from(tasks.keys()).map((taskId) => service.stop(taskId, reason)),

packages/agent-core-v2/test/tool/tool.test.ts

@@ -1256,10 +1256,36 @@ describe('Agent tool execution contract', () => {
 
     expect(result.isError).toBe(true);
     expect(result.output).toContain('status: failed');
-    expect(result.output).not.toContain('was stopped by the user');
-    expect(result.output).toContain('not a system error');
-    expect(result.output).toContain('capacity');
-    expect(result.output).toContain('wait for the user');
+    expect(result.output).toContain('The subagent was stopped before it finished by user.');
+  });
+
+  it('reports the reason when a foreground subagent is stopped for another cause', async () => {
+    const lifecycle = createAgentLifecycleStub({
+      createAgentIds: ['agent-child'],
+      runCompletion: (_agentId, _request, options) =>
+        new Promise((_resolve, reject) => {
+          options.signal.addEventListener('abort', () => reject(options.signal.reason), {
+            once: true,
+          });
+        }),
+    });
+    const context = createAgentToolContext(lifecycle);
+
+    const resultPromise = executeAgentTool(context, {
+      prompt: 'Investigate',
+      description: 'Find cause',
+    });
+    await vi.waitFor(() => {
+      expect(context.get(IAgentTaskService).list(false)).toHaveLength(1);
+    });
+    const [task] = context.get(IAgentTaskService).list(false);
+    await context.get(IAgentTaskService).stop(task!.taskId, 'Session closed');
+    const result = await resultPromise;
+
+    expect(result.isError).toBe(true);
+    expect(result.output).toContain(
+      'The subagent was stopped before it finished. Reason: Session closed',
+    );
   });
 
   it('returns the spawned agent id when a foreground subagent times out', async () => {

packages/kap-server/src/routes/tasks.ts

@@ -256,7 +256,7 @@ export function registerTasksRoutes(app: TasksRouteHost, core: Scope): void {
         return;
       }
 
-      await resolved.tasks?.stop(task_id);
+      await resolved.tasks?.stopByUser(task_id);
       requestLog(req)?.info({ session_id, task_id }, 'task cancelled');
       reply.send(okEnvelope({ cancelled: true as const }, req.id));
     },

packages/kap-server/test/tasks.test.ts

@@ -258,6 +258,7 @@ describe('server-v2 /api/v1/sessions/{sid}/tasks', () => {
     );
     expect(cancelled.body.code).toBe(0);
     expect(cancelled.body.data).toEqual({ cancelled: true });
+    expect(tasks.getTask(taskId)?.stopReason).toBe('Aborted by the user');
 
     // The task is now terminal (killed → cancelled); a second cancel is a
     // conflict with the idempotent envelope shape.