refactor(core): extract ExecutionLifecycleService for tool backgrounding (#21717)

packages/core/src/services/executionLifecycleService.test.ts

@@ -0,0 +1,298 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import {
+  ExecutionLifecycleService,
+  type ExecutionHandle,
+  type ExecutionResult,
+} from './executionLifecycleService.js';
+
+function createResult(
+  overrides: Partial<ExecutionResult> = {},
+): ExecutionResult {
+  return {
+    rawOutput: Buffer.from(''),
+    output: '',
+    exitCode: 0,
+    signal: null,
+    error: null,
+    aborted: false,
+    pid: 123,
+    executionMethod: 'child_process',
+    ...overrides,
+  };
+}
+
+describe('ExecutionLifecycleService', () => {
+  beforeEach(() => {
+    ExecutionLifecycleService.resetForTest();
+  });
+
+  it('completes managed executions in the foreground and notifies exit subscribers', async () => {
+    const handle = ExecutionLifecycleService.createExecution();
+    if (handle.pid === undefined) {
+      throw new Error('Expected execution ID.');
+    }
+
+    const onExit = vi.fn();
+    const unsubscribe = ExecutionLifecycleService.onExit(handle.pid, onExit);
+
+    ExecutionLifecycleService.appendOutput(handle.pid, 'Hello');
+    ExecutionLifecycleService.appendOutput(handle.pid, ' World');
+    ExecutionLifecycleService.completeExecution(handle.pid, {
+      exitCode: 0,
+    });
+
+    const result = await handle.result;
+    expect(result.output).toBe('Hello World');
+    expect(result.executionMethod).toBe('none');
+    expect(result.backgrounded).toBeUndefined();
+
+    await vi.waitFor(() => {
+      expect(onExit).toHaveBeenCalledWith(0, undefined);
+    });
+
+    unsubscribe();
+  });
+
+  it('supports explicit execution methods for managed executions', async () => {
+    const handle = ExecutionLifecycleService.createExecution(
+      '',
+      undefined,
+      'remote_agent',
+    );
+    if (handle.pid === undefined) {
+      throw new Error('Expected execution ID.');
+    }
+
+    ExecutionLifecycleService.completeExecution(handle.pid, {
+      exitCode: 0,
+    });
+    const result = await handle.result;
+    expect(result.executionMethod).toBe('remote_agent');
+  });
+
+  it('supports backgrounding managed executions and continues streaming updates', async () => {
+    const handle = ExecutionLifecycleService.createExecution();
+    if (handle.pid === undefined) {
+      throw new Error('Expected execution ID.');
+    }
+
+    const chunks: string[] = [];
+    const onExit = vi.fn();
+
+    const unsubscribeStream = ExecutionLifecycleService.subscribe(
+      handle.pid,
+      (event) => {
+        if (event.type === 'data' && typeof event.chunk === 'string') {
+          chunks.push(event.chunk);
+        }
+      },
+    );
+    const unsubscribeExit = ExecutionLifecycleService.onExit(
+      handle.pid,
+      onExit,
+    );
+
+    ExecutionLifecycleService.appendOutput(handle.pid, 'Chunk 1');
+    ExecutionLifecycleService.background(handle.pid);
+
+    const backgroundResult = await handle.result;
+    expect(backgroundResult.backgrounded).toBe(true);
+    expect(backgroundResult.output).toBe('Chunk 1');
+
+    ExecutionLifecycleService.appendOutput(handle.pid, '\nChunk 2');
+    ExecutionLifecycleService.completeExecution(handle.pid, {
+      exitCode: 0,
+    });
+
+    await vi.waitFor(() => {
+      expect(chunks.join('')).toContain('Chunk 2');
+      expect(onExit).toHaveBeenCalledWith(0, undefined);
+    });
+
+    unsubscribeStream();
+    unsubscribeExit();
+  });
+
+  it('kills managed executions and resolves with aborted result', async () => {
+    const onKill = vi.fn();
+    const handle = ExecutionLifecycleService.createExecution('', onKill);
+    if (handle.pid === undefined) {
+      throw new Error('Expected execution ID.');
+    }
+
+    ExecutionLifecycleService.appendOutput(handle.pid, 'work');
+    ExecutionLifecycleService.kill(handle.pid);
+
+    const result = await handle.result;
+    expect(onKill).toHaveBeenCalledTimes(1);
+    expect(result.aborted).toBe(true);
+    expect(result.exitCode).toBe(130);
+    expect(result.error?.message).toContain('Operation cancelled by user');
+  });
+
+  it('does not probe OS process state for completed non-process execution IDs', async () => {
+    const handle = ExecutionLifecycleService.createExecution();
+    if (handle.pid === undefined) {
+      throw new Error('Expected execution ID.');
+    }
+
+    ExecutionLifecycleService.completeExecution(handle.pid, { exitCode: 0 });
+    await handle.result;
+
+    const processKillSpy = vi.spyOn(process, 'kill');
+    expect(ExecutionLifecycleService.isActive(handle.pid)).toBe(false);
+    expect(processKillSpy).not.toHaveBeenCalled();
+    processKillSpy.mockRestore();
+  });
+
+  it('manages external executions through registration hooks', async () => {
+    const writeInput = vi.fn();
+    const isActive = vi.fn().mockReturnValue(true);
+    const exitListener = vi.fn();
+    const chunks: string[] = [];
+
+    let output = 'seed';
+    const handle: ExecutionHandle = ExecutionLifecycleService.attachExecution(
+      4321,
+      {
+        executionMethod: 'child_process',
+        getBackgroundOutput: () => output,
+        getSubscriptionSnapshot: () => output,
+        writeInput,
+        isActive,
+      },
+    );
+
+    const unsubscribe = ExecutionLifecycleService.subscribe(4321, (event) => {
+      if (event.type === 'data' && typeof event.chunk === 'string') {
+        chunks.push(event.chunk);
+      }
+    });
+    ExecutionLifecycleService.onExit(4321, exitListener);
+
+    ExecutionLifecycleService.writeInput(4321, 'stdin');
+    expect(writeInput).toHaveBeenCalledWith('stdin');
+    expect(ExecutionLifecycleService.isActive(4321)).toBe(true);
+
+    const firstChunk = { type: 'data', chunk: ' +delta' } as const;
+    ExecutionLifecycleService.emitEvent(4321, firstChunk);
+    output += firstChunk.chunk;
+
+    ExecutionLifecycleService.background(4321);
+    const backgroundResult = await handle.result;
+    expect(backgroundResult.backgrounded).toBe(true);
+    expect(backgroundResult.output).toBe('seed +delta');
+    expect(backgroundResult.executionMethod).toBe('child_process');
+
+    ExecutionLifecycleService.completeWithResult(
+      4321,
+      createResult({
+        pid: 4321,
+        output: 'seed +delta done',
+        rawOutput: Buffer.from('seed +delta done'),
+        executionMethod: 'child_process',
+      }),
+    );
+
+    await vi.waitFor(() => {
+      expect(exitListener).toHaveBeenCalledWith(0, undefined);
+    });
+
+    const lateExit = vi.fn();
+    ExecutionLifecycleService.onExit(4321, lateExit);
+    expect(lateExit).toHaveBeenCalledWith(0, undefined);
+
+    unsubscribe();
+  });
+
+  it('supports late subscription catch-up after backgrounding an external execution', async () => {
+    let output = 'seed';
+    const onExit = vi.fn();
+    const handle = ExecutionLifecycleService.attachExecution(4322, {
+      executionMethod: 'child_process',
+      getBackgroundOutput: () => output,
+      getSubscriptionSnapshot: () => output,
+    });
+
+    ExecutionLifecycleService.onExit(4322, onExit);
+    ExecutionLifecycleService.background(4322);
+
+    const backgroundResult = await handle.result;
+    expect(backgroundResult.backgrounded).toBe(true);
+    expect(backgroundResult.output).toBe('seed');
+
+    output += ' +late';
+    ExecutionLifecycleService.emitEvent(4322, {
+      type: 'data',
+      chunk: ' +late',
+    });
+
+    const chunks: string[] = [];
+    const unsubscribe = ExecutionLifecycleService.subscribe(4322, (event) => {
+      if (event.type === 'data' && typeof event.chunk === 'string') {
+        chunks.push(event.chunk);
+      }
+    });
+    expect(chunks[0]).toBe('seed +late');
+
+    output += ' +live';
+    ExecutionLifecycleService.emitEvent(4322, {
+      type: 'data',
+      chunk: ' +live',
+    });
+    expect(chunks[chunks.length - 1]).toBe(' +live');
+
+    ExecutionLifecycleService.completeWithResult(
+      4322,
+      createResult({
+        pid: 4322,
+        output,
+        rawOutput: Buffer.from(output),
+        executionMethod: 'child_process',
+      }),
+    );
+
+    await vi.waitFor(() => {
+      expect(onExit).toHaveBeenCalledWith(0, undefined);
+    });
+    unsubscribe();
+  });
+
+  it('kills external executions and settles pending promises', async () => {
+    const terminate = vi.fn();
+    const onExit = vi.fn();
+    const handle = ExecutionLifecycleService.attachExecution(4323, {
+      executionMethod: 'child_process',
+      initialOutput: 'running',
+      kill: terminate,
+    });
+    ExecutionLifecycleService.onExit(4323, onExit);
+    ExecutionLifecycleService.kill(4323);
+
+    const result = await handle.result;
+    expect(terminate).toHaveBeenCalledTimes(1);
+    expect(result.aborted).toBe(true);
+    expect(result.exitCode).toBe(130);
+    expect(result.output).toBe('running');
+    expect(result.error?.message).toContain('Operation cancelled by user');
+    expect(onExit).toHaveBeenCalledWith(130, undefined);
+  });
+
+  it('rejects duplicate execution registration for active execution IDs', () => {
+    ExecutionLifecycleService.attachExecution(4324, {
+      executionMethod: 'child_process',
+    });
+
+    expect(() => {
+      ExecutionLifecycleService.attachExecution(4324, {
+        executionMethod: 'child_process',
+      });
+    }).toThrow('Execution 4324 is already attached.');
+  });
+});

packages/core/src/services/executionLifecycleService.ts

@@ -0,0 +1,454 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { AnsiOutput } from '../utils/terminalSerializer.js';
+
+export type ExecutionMethod =
+  | 'lydell-node-pty'
+  | 'node-pty'
+  | 'child_process'
+  | 'remote_agent'
+  | 'none';
+
+export interface ExecutionResult {
+  rawOutput: Buffer;
+  output: string;
+  exitCode: number | null;
+  signal: number | null;
+  error: Error | null;
+  aborted: boolean;
+  pid: number | undefined;
+  executionMethod: ExecutionMethod;
+  backgrounded?: boolean;
+}
+
+export interface ExecutionHandle {
+  pid: number | undefined;
+  result: Promise<ExecutionResult>;
+}
+
+export type ExecutionOutputEvent =
+  | {
+      type: 'data';
+      chunk: string | AnsiOutput;
+    }
+  | {
+      type: 'binary_detected';
+    }
+  | {
+      type: 'binary_progress';
+      bytesReceived: number;
+    }
+  | {
+      type: 'exit';
+      exitCode: number | null;
+      signal: number | null;
+    };
+
+export interface ExecutionCompletionOptions {
+  exitCode?: number | null;
+  signal?: number | null;
+  error?: Error | null;
+  aborted?: boolean;
+}
+
+export interface ExternalExecutionRegistration {
+  executionMethod: ExecutionMethod;
+  initialOutput?: string;
+  getBackgroundOutput?: () => string;
+  getSubscriptionSnapshot?: () => string | AnsiOutput | undefined;
+  writeInput?: (input: string) => void;
+  kill?: () => void;
+  isActive?: () => boolean;
+}
+
+interface ManagedExecutionBase {
+  executionMethod: ExecutionMethod;
+  output: string;
+  getBackgroundOutput?: () => string;
+  getSubscriptionSnapshot?: () => string | AnsiOutput | undefined;
+}
+
+interface VirtualExecutionState extends ManagedExecutionBase {
+  kind: 'virtual';
+  onKill?: () => void;
+}
+
+interface ExternalExecutionState extends ManagedExecutionBase {
+  kind: 'external';
+  writeInput?: (input: string) => void;
+  kill?: () => void;
+  isActive?: () => boolean;
+}
+
+type ManagedExecutionState = VirtualExecutionState | ExternalExecutionState;
+
+const NON_PROCESS_EXECUTION_ID_START = 2_000_000_000;
+
+/**
+ * Central owner for execution backgrounding lifecycle across shell and tools.
+ */
+export class ExecutionLifecycleService {
+  private static readonly EXIT_INFO_TTL_MS = 5 * 60 * 1000;
+  private static nextExecutionId = NON_PROCESS_EXECUTION_ID_START;
+
+  private static activeExecutions = new Map<number, ManagedExecutionState>();
+  private static activeResolvers = new Map<
+    number,
+    (result: ExecutionResult) => void
+  >();
+  private static activeListeners = new Map<
+    number,
+    Set<(event: ExecutionOutputEvent) => void>
+  >();
+  private static exitedExecutionInfo = new Map<
+    number,
+    { exitCode: number; signal?: number }
+  >();
+
+  private static storeExitInfo(
+    executionId: number,
+    exitCode: number,
+    signal?: number,
+  ): void {
+    this.exitedExecutionInfo.set(executionId, {
+      exitCode,
+      signal,
+    });
+    setTimeout(() => {
+      this.exitedExecutionInfo.delete(executionId);
+    }, this.EXIT_INFO_TTL_MS).unref();
+  }
+
+  private static allocateExecutionId(): number {
+    let executionId = ++this.nextExecutionId;
+    while (this.activeExecutions.has(executionId)) {
+      executionId = ++this.nextExecutionId;
+    }
+    return executionId;
+  }
+
+  private static createPendingResult(
+    executionId: number,
+  ): Promise<ExecutionResult> {
+    return new Promise<ExecutionResult>((resolve) => {
+      this.activeResolvers.set(executionId, resolve);
+    });
+  }
+
+  private static createAbortedResult(
+    executionId: number,
+    execution: ManagedExecutionState,
+  ): ExecutionResult {
+    const output = execution.getBackgroundOutput?.() ?? execution.output;
+    return {
+      rawOutput: Buffer.from(output, 'utf8'),
+      output,
+      exitCode: 130,
+      signal: null,
+      error: new Error('Operation cancelled by user.'),
+      aborted: true,
+      pid: executionId,
+      executionMethod: execution.executionMethod,
+    };
+  }
+
+  /**
+   * Resets lifecycle state for isolated unit tests.
+   */
+  static resetForTest(): void {
+    this.activeExecutions.clear();
+    this.activeResolvers.clear();
+    this.activeListeners.clear();
+    this.exitedExecutionInfo.clear();
+    this.nextExecutionId = NON_PROCESS_EXECUTION_ID_START;
+  }
+
+  static attachExecution(
+    executionId: number,
+    registration: ExternalExecutionRegistration,
+  ): ExecutionHandle {
+    if (
+      this.activeExecutions.has(executionId) ||
+      this.activeResolvers.has(executionId)
+    ) {
+      throw new Error(`Execution ${executionId} is already attached.`);
+    }
+    this.exitedExecutionInfo.delete(executionId);
+
+    this.activeExecutions.set(executionId, {
+      executionMethod: registration.executionMethod,
+      output: registration.initialOutput ?? '',
+      kind: 'external',
+      getBackgroundOutput: registration.getBackgroundOutput,
+      getSubscriptionSnapshot: registration.getSubscriptionSnapshot,
+      writeInput: registration.writeInput,
+      kill: registration.kill,
+      isActive: registration.isActive,
+    });
+
+    return {
+      pid: executionId,
+      result: this.createPendingResult(executionId),
+    };
+  }
+
+  static createExecution(
+    initialOutput = '',
+    onKill?: () => void,
+    executionMethod: ExecutionMethod = 'none',
+  ): ExecutionHandle {
+    const executionId = this.allocateExecutionId();
+
+    this.activeExecutions.set(executionId, {
+      executionMethod,
+      output: initialOutput,
+      kind: 'virtual',
+      onKill,
+      getBackgroundOutput: () => {
+        const state = this.activeExecutions.get(executionId);
+        return state?.output ?? initialOutput;
+      },
+      getSubscriptionSnapshot: () => {
+        const state = this.activeExecutions.get(executionId);
+        return state?.output ?? initialOutput;
+      },
+    });
+
+    return {
+      pid: executionId,
+      result: this.createPendingResult(executionId),
+    };
+  }
+
+  static appendOutput(executionId: number, chunk: string): void {
+    const execution = this.activeExecutions.get(executionId);
+    if (!execution || chunk.length === 0) {
+      return;
+    }
+
+    execution.output += chunk;
+    this.emitEvent(executionId, { type: 'data', chunk });
+  }
+
+  static emitEvent(executionId: number, event: ExecutionOutputEvent): void {
+    const listeners = this.activeListeners.get(executionId);
+    if (listeners) {
+      listeners.forEach((listener) => listener(event));
+    }
+  }
+
+  private static resolvePending(
+    executionId: number,
+    result: ExecutionResult,
+  ): void {
+    const resolve = this.activeResolvers.get(executionId);
+    if (!resolve) {
+      return;
+    }
+
+    resolve(result);
+    this.activeResolvers.delete(executionId);
+  }
+
+  private static settleExecution(
+    executionId: number,
+    result: ExecutionResult,
+  ): void {
+    if (!this.activeExecutions.has(executionId)) {
+      return;
+    }
+
+    this.resolvePending(executionId, result);
+    this.emitEvent(executionId, {
+      type: 'exit',
+      exitCode: result.exitCode,
+      signal: result.signal,
+    });
+
+    this.activeListeners.delete(executionId);
+    this.activeExecutions.delete(executionId);
+    this.storeExitInfo(
+      executionId,
+      result.exitCode ?? 0,
+      result.signal ?? undefined,
+    );
+  }
+
+  static completeExecution(
+    executionId: number,
+    options?: ExecutionCompletionOptions,
+  ): void {
+    const execution = this.activeExecutions.get(executionId);
+    if (!execution) {
+      return;
+    }
+
+    const {
+      error = null,
+      aborted = false,
+      exitCode = error ? 1 : 0,
+      signal = null,
+    } = options ?? {};
+
+    const output = execution.getBackgroundOutput?.() ?? execution.output;
+
+    this.settleExecution(executionId, {
+      rawOutput: Buffer.from(output, 'utf8'),
+      output,
+      exitCode,
+      signal,
+      error,
+      aborted,
+      pid: executionId,
+      executionMethod: execution.executionMethod,
+    });
+  }
+
+  static completeWithResult(
+    executionId: number,
+    result: ExecutionResult,
+  ): void {
+    this.settleExecution(executionId, result);
+  }
+
+  static background(executionId: number): void {
+    const resolve = this.activeResolvers.get(executionId);
+    if (!resolve) {
+      return;
+    }
+
+    const execution = this.activeExecutions.get(executionId);
+    if (!execution) {
+      return;
+    }
+
+    const output = execution.getBackgroundOutput?.() ?? execution.output;
+
+    resolve({
+      rawOutput: Buffer.from(''),
+      output,
+      exitCode: null,
+      signal: null,
+      error: null,
+      aborted: false,
+      pid: executionId,
+      executionMethod: execution.executionMethod,
+      backgrounded: true,
+    });
+
+    this.activeResolvers.delete(executionId);
+  }
+
+  static subscribe(
+    executionId: number,
+    listener: (event: ExecutionOutputEvent) => void,
+  ): () => void {
+    if (!this.activeListeners.has(executionId)) {
+      this.activeListeners.set(executionId, new Set());
+    }
+    this.activeListeners.get(executionId)?.add(listener);
+
+    const execution = this.activeExecutions.get(executionId);
+    if (execution) {
+      const snapshot =
+        execution.getSubscriptionSnapshot?.() ??
+        (execution.output.length > 0 ? execution.output : undefined);
+      if (snapshot && (typeof snapshot !== 'string' || snapshot.length > 0)) {
+        listener({ type: 'data', chunk: snapshot });
+      }
+    }
+
+    return () => {
+      this.activeListeners.get(executionId)?.delete(listener);
+      if (this.activeListeners.get(executionId)?.size === 0) {
+        this.activeListeners.delete(executionId);
+      }
+    };
+  }
+
+  static onExit(
+    executionId: number,
+    callback: (exitCode: number, signal?: number) => void,
+  ): () => void {
+    if (this.activeExecutions.has(executionId)) {
+      const listener = (event: ExecutionOutputEvent) => {
+        if (event.type === 'exit') {
+          callback(event.exitCode ?? 0, event.signal ?? undefined);
+          unsubscribe();
+        }
+      };
+      const unsubscribe = this.subscribe(executionId, listener);
+      return unsubscribe;
+    }
+
+    const exitedInfo = this.exitedExecutionInfo.get(executionId);
+    if (exitedInfo) {
+      callback(exitedInfo.exitCode, exitedInfo.signal);
+    }
+
+    return () => {};
+  }
+
+  static kill(executionId: number): void {
+    const execution = this.activeExecutions.get(executionId);
+    if (!execution) {
+      return;
+    }
+
+    if (execution.kind === 'virtual') {
+      execution.onKill?.();
+    }
+
+    if (execution.kind === 'external') {
+      execution.kill?.();
+    }
+
+    this.completeWithResult(
+      executionId,
+      this.createAbortedResult(executionId, execution),
+    );
+  }
+
+  static isActive(executionId: number): boolean {
+    const execution = this.activeExecutions.get(executionId);
+    if (!execution) {
+      if (executionId >= NON_PROCESS_EXECUTION_ID_START) {
+        return false;
+      }
+      try {
+        return process.kill(executionId, 0);
+      } catch {
+        return false;
+      }
+    }
+
+    if (execution.kind === 'virtual') {
+      return true;
+    }
+
+    if (execution.kind === 'external' && execution.isActive) {
+      try {
+        return execution.isActive();
+      } catch {
+        return false;
+      }
+    }
+
+    try {
+      return process.kill(executionId, 0);
+    } catch {
+      return false;
+    }
+  }
+
+  static writeInput(executionId: number, input: string): void {
+    const execution = this.activeExecutions.get(executionId);
+    if (execution?.kind === 'external') {
+      execution.writeInput?.(input);
+    }
+  }
+}

packages/core/src/services/shellExecutionService.test.ts

@@ -22,6 +22,7 @@ import {
   type ShellOutputEvent,
   type ShellExecutionConfig,
 } from './shellExecutionService.js';
+import { ExecutionLifecycleService } from './executionLifecycleService.js';
 import type { AnsiOutput, AnsiToken } from '../utils/terminalSerializer.js';
 
 // Hoisted Mocks
@@ -201,6 +202,7 @@ describe('ShellExecutionService', () => {
 
   beforeEach(() => {
     vi.clearAllMocks();
+    ExecutionLifecycleService.resetForTest();
     mockSerializeTerminalToObject.mockReturnValue([]);
     mockIsBinary.mockReturnValue(false);
     mockPlatform.mockReturnValue('linux');
@@ -469,9 +471,10 @@ describe('ShellExecutionService', () => {
   });
 
   describe('pty interaction', () => {
-    let ptySpy: { mockRestore(): void };
+    let activePtysGetSpy: { mockRestore: () => void };
+
     beforeEach(() => {
-      ptySpy = vi
+      activePtysGetSpy = vi
         .spyOn(ShellExecutionService['activePtys'], 'get')
         .mockReturnValue({
           // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -482,7 +485,7 @@ describe('ShellExecutionService', () => {
     });
 
     afterEach(() => {
-      ptySpy.mockRestore();
+      activePtysGetSpy.mockRestore();
     });
 
     it('should write to the pty and trigger a render', async () => {
@@ -1102,11 +1105,10 @@ describe('ShellExecutionService', () => {
     });
 
     it('should destroy the PTY when an exception occurs after spawn in executeWithPty', async () => {
-      // Simulate: spawn succeeds, Promise executor runs fine (pid accesses 1-2),
-      // but the return statement `{ pid: ptyProcess.pid }` (access 3) throws.
-      // The catch block should call spawnedPty.destroy() to release the fd.
+      // Simulate: spawn succeeds, but accessing ptyProcess.pid throws.
+      // spawnedPty is set before the pid access, so the catch block should
+      // call spawnedPty.destroy() to release the fd.
       const destroySpy = vi.fn();
-      let pidAccessCount = 0;
       const faultyPty = {
         onData: vi.fn(),
         onExit: vi.fn(),
@@ -1114,15 +1116,8 @@ describe('ShellExecutionService', () => {
         kill: vi.fn(),
         resize: vi.fn(),
         destroy: destroySpy,
-        get pid() {
-          pidAccessCount++;
-          // Accesses 1-2 are inside the Promise executor (setup).
-          // Access 3 is at `return { pid: ptyProcess.pid, result }`,
-          // outside the Promise — caught by the outer try/catch.
-          if (pidAccessCount > 2) {
-            throw new Error('Simulated post-spawn failure on pid access');
-          }
-          return 77777;
+        get pid(): number {
+          throw new Error('Simulated post-spawn failure on pid access');
         },
       };
       mockPtySpawn.mockReturnValueOnce(faultyPty);