feat(core): extract execution lifecycle facade

Extracts ExecutionLifecycleService to decouple background task tracking from ShellExecutionService, enabling Ctrl+B backgrounding for any tool (including remote agents).

packages/core/src/core/coreToolHookTriggers.test.ts

@@ -11,6 +11,7 @@ import {
   BaseToolInvocation,
   type ToolResult,
   type AnyDeclarativeTool,
+  type ToolLiveOutput,
 } from '../tools/tools.js';
 import type { MessageBus } from '../confirmation-bus/message-bus.js';
 import type { HookSystem } from '../hooks/hookSystem.js';
@@ -37,6 +38,30 @@ class MockInvocation extends BaseToolInvocation<{ key?: string }, ToolResult> {
   }
 }
 
+class MockBackgroundableInvocation extends BaseToolInvocation<
+  { key?: string },
+  ToolResult
+> {
+  constructor(params: { key?: string }, messageBus: MessageBus) {
+    super(params, messageBus);
+  }
+  getDescription() {
+    return 'mock-pid';
+  }
+  async execute(
+    _signal: AbortSignal,
+    _updateOutput?: (output: ToolLiveOutput) => void,
+    _shellExecutionConfig?: unknown,
+    setExecutionIdCallback?: (executionId: number) => void,
+  ) {
+    setExecutionIdCallback?.(4242);
+    return {
+      llmContent: 'pid',
+      returnDisplay: 'pid',
+    };
+  }
+}
+
 describe('executeToolWithHooks', () => {
   let messageBus: MessageBus;
   let mockTool: AnyDeclarativeTool;
@@ -258,4 +283,26 @@ describe('executeToolWithHooks', () => {
     expect(invocation.params.key).toBe('original');
     expect(mockTool.build).not.toHaveBeenCalled();
   });
+
+  it('should pass execution ID callback through for non-shell invocations', async () => {
+    const invocation = new MockBackgroundableInvocation({}, messageBus);
+    const abortSignal = new AbortController().signal;
+    const setExecutionIdCallback = vi.fn();
+
+    vi.mocked(mockHookSystem.fireBeforeToolEvent).mockResolvedValue(undefined);
+    vi.mocked(mockHookSystem.fireAfterToolEvent).mockResolvedValue(undefined);
+
+    await executeToolWithHooks(
+      invocation,
+      'test_tool',
+      abortSignal,
+      mockTool,
+      undefined,
+      undefined,
+      setExecutionIdCallback,
+      mockConfig,
+    );
+
+    expect(setExecutionIdCallback).toHaveBeenCalledWith(4242);
+  });
 });

packages/core/src/core/coreToolHookTriggers.ts

@@ -15,7 +15,6 @@ import type {
 import { ToolErrorType } from '../tools/tool-error.js';
 import { debugLogger } from '../utils/debugLogger.js';
 import type { ShellExecutionConfig } from '../index.js';
-import { ShellToolInvocation } from '../tools/shell.js';
 import { DiscoveredMCPToolInvocation } from '../tools/mcp-tool.js';
 
 /**
@@ -26,7 +25,7 @@ import { DiscoveredMCPToolInvocation } from '../tools/mcp-tool.js';
  * @returns MCP context if this is an MCP tool, undefined otherwise
  */
 function extractMcpContext(
-  invocation: ShellToolInvocation | AnyToolInvocation,
+  invocation: AnyToolInvocation,
   config: Config,
 ): McpToolContext | undefined {
   if (!(invocation instanceof DiscoveredMCPToolInvocation)) {
@@ -63,18 +62,18 @@ function extractMcpContext(
  * @param signal Abort signal for cancellation
  * @param liveOutputCallback Optional callback for live output updates
  * @param shellExecutionConfig Optional shell execution config
- * @param setPidCallback Optional callback to set the PID for shell invocations
+ * @param setExecutionIdCallback Optional callback to set an execution ID for backgroundable invocations
  * @param config Config to look up MCP server details for hook context
  * @returns The tool result
  */
 export async function executeToolWithHooks(
-  invocation: ShellToolInvocation | AnyToolInvocation,
+  invocation: AnyToolInvocation,
   toolName: string,
   signal: AbortSignal,
   tool: AnyDeclarativeTool,
   liveOutputCallback?: (outputChunk: ToolLiveOutput) => void,
   shellExecutionConfig?: ShellExecutionConfig,
-  setPidCallback?: (pid: number) => void,
+  setExecutionIdCallback?: (executionId: number) => void,
   config?: Config,
   originalRequestName?: string,
 ): Promise<ToolResult> {
@@ -154,22 +153,14 @@ export async function executeToolWithHooks(
     }
   }
 
-  // Execute the actual tool
-  let toolResult: ToolResult;
-  if (setPidCallback && invocation instanceof ShellToolInvocation) {
-    toolResult = await invocation.execute(
-      signal,
-      liveOutputCallback,
-      shellExecutionConfig,
-      setPidCallback,
-    );
-  } else {
-    toolResult = await invocation.execute(
-      signal,
-      liveOutputCallback,
-      shellExecutionConfig,
-    );
-  }
+  // Execute the actual tool. Tools that support backgrounding can optionally
+  // surface an execution ID via the callback.
+  const toolResult: ToolResult = await invocation.execute(
+    signal,
+    liveOutputCallback,
+    shellExecutionConfig,
+    setExecutionIdCallback,
+  );
 
   // Append notification if parameters were modified
   if (inputWasModified) {

packages/core/src/scheduler/tool-executor.test.ts

@@ -469,7 +469,7 @@ describe('ToolExecutor', () => {
     expect(result.status).toBe(CoreToolCallStatus.Success);
   });
 
-  it('should report PID updates for shell tools', async () => {
+  it('should report execution ID updates for backgroundable tools', async () => {
     // 1. Setup ShellToolInvocation
     const messageBus = createMockMessageBus();
     const shellInvocation = new ShellToolInvocation(
@@ -480,7 +480,7 @@ describe('ToolExecutor', () => {
     // We need a dummy tool that matches the invocation just for structure
     const mockTool = new MockTool({ name: SHELL_TOOL_NAME });
 
-    // 2. Mock executeToolWithHooks to trigger the PID callback
+    // 2. Mock executeToolWithHooks to trigger the execution ID callback
     const testPid = 12345;
     vi.mocked(coreToolHookTriggers.executeToolWithHooks).mockImplementation(
       async (
@@ -490,13 +490,13 @@ describe('ToolExecutor', () => {
         _tool,
         _liveCb,
         _shellCfg,
-        setPidCallback,
+        setExecutionIdCallback,
         _config,
         _originalRequestName,
       ) => {
-        // Simulate the shell tool reporting a PID
-        if (setPidCallback) {
-          setPidCallback(testPid);
+        // Simulate the tool reporting an execution ID
+        if (setExecutionIdCallback) {
+          setExecutionIdCallback(testPid);
         }
         return { llmContent: 'done', returnDisplay: 'done' };
       },
@@ -525,7 +525,7 @@ describe('ToolExecutor', () => {
       onUpdateToolCall,
     });
 
-    // 4. Verify PID was reported
+    // 4. Verify execution ID was reported
     expect(onUpdateToolCall).toHaveBeenCalledWith(
       expect.objectContaining({
         status: CoreToolCallStatus.Executing,
@@ -534,6 +534,59 @@ describe('ToolExecutor', () => {
     );
   });
 
+  it('should report execution ID updates for non-shell backgroundable tools', async () => {
+    const mockTool = new MockTool({
+      name: 'remote_agent_call',
+      description: 'Remote agent call',
+    });
+    const invocation = mockTool.build({});
+
+    const testExecutionId = 67890;
+    vi.mocked(coreToolHookTriggers.executeToolWithHooks).mockImplementation(
+      async (
+        _inv,
+        _name,
+        _sig,
+        _tool,
+        _liveCb,
+        _shellCfg,
+        setExecutionIdCallback,
+      ) => {
+        setExecutionIdCallback?.(testExecutionId);
+        return { llmContent: 'done', returnDisplay: 'done' };
+      },
+    );
+
+    const scheduledCall: ScheduledToolCall = {
+      status: CoreToolCallStatus.Scheduled,
+      request: {
+        callId: 'call-remote-pid',
+        name: 'remote_agent_call',
+        args: {},
+        isClientInitiated: false,
+        prompt_id: 'prompt-remote-pid',
+      },
+      tool: mockTool,
+      invocation: invocation as unknown as AnyToolInvocation,
+      startTime: Date.now(),
+    };
+
+    const onUpdateToolCall = vi.fn();
+
+    await executor.execute({
+      call: scheduledCall,
+      signal: new AbortController().signal,
+      onUpdateToolCall,
+    });
+
+    expect(onUpdateToolCall).toHaveBeenCalledWith(
+      expect.objectContaining({
+        status: CoreToolCallStatus.Executing,
+        pid: testExecutionId,
+      }),
+    );
+  });
+
   it('should return cancelled result with partial output when signal is aborted', async () => {
     const mockTool = new MockTool({
       name: 'slowTool',

packages/core/src/scheduler/tool-executor.ts

@@ -16,7 +16,6 @@ import {
   type ToolLiveOutput,
 } from '../index.js';
 import { SHELL_TOOL_NAME } from '../tools/tool-names.js';
-import { ShellToolInvocation } from '../tools/shell.js';
 import { DiscoveredMCPTool } from '../tools/mcp-tool.js';
 import { executeToolWithHooks } from '../core/coreToolHookTriggers.js';
 import {
@@ -89,43 +88,29 @@ export class ToolExecutor {
         let completedToolCall: CompletedToolCall;
 
         try {
-          let promise: Promise<ToolResult>;
-          if (invocation instanceof ShellToolInvocation) {
-            const setPidCallback = (pid: number) => {
-              const executingCall: ExecutingToolCall = {
-                ...call,
-                status: CoreToolCallStatus.Executing,
-                tool,
-                invocation,
-                pid,
-                startTime: 'startTime' in call ? call.startTime : undefined,
-              };
-              onUpdateToolCall(executingCall);
+          const setExecutionIdCallback = (executionId: number) => {
+            const executingCall: ExecutingToolCall = {
+              ...call,
+              status: CoreToolCallStatus.Executing,
+              tool,
+              invocation,
+              pid: executionId,
+              startTime: 'startTime' in call ? call.startTime : undefined,
             };
-            promise = executeToolWithHooks(
-              invocation,
-              toolName,
-              signal,
-              tool,
-              liveOutputCallback,
-              shellExecutionConfig,
-              setPidCallback,
-              this.config,
-              request.originalRequestName,
-            );
-          } else {
-            promise = executeToolWithHooks(
-              invocation,
-              toolName,
-              signal,
-              tool,
-              liveOutputCallback,
-              shellExecutionConfig,
-              undefined,
-              this.config,
-              request.originalRequestName,
-            );
-          }
+            onUpdateToolCall(executingCall);
+          };
+
+          const promise = executeToolWithHooks(
+            invocation,
+            toolName,
+            signal,
+            tool,
+            liveOutputCallback,
+            shellExecutionConfig,
+            setExecutionIdCallback,
+            this.config,
+            request.originalRequestName,
+          );
 
           const toolResult: ToolResult = await promise;
 

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

@@ -21,6 +21,7 @@ import {
   type ShellOutputEvent,
   type ShellExecutionConfig,
 } from './shellExecutionService.js';
+import { ExecutionLifecycleService } from './executionLifecycleService.js';
 import type { AnsiOutput, AnsiToken } from '../utils/terminalSerializer.js';
 
 // Hoisted Mocks
@@ -166,6 +167,7 @@ describe('ShellExecutionService', () => {
 
   beforeEach(() => {
     vi.clearAllMocks();
+    ExecutionLifecycleService.resetForTest();
     mockSerializeTerminalToObject.mockReturnValue([]);
     mockIsBinary.mockReturnValue(false);
     mockPlatform.mockReturnValue('linux');
@@ -432,13 +434,21 @@ describe('ShellExecutionService', () => {
   });
 
   describe('pty interaction', () => {
+    let activePtysGetSpy: { mockRestore: () => void };
+
     beforeEach(() => {
-      vi.spyOn(ShellExecutionService['activePtys'], 'get').mockReturnValue({
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        ptyProcess: mockPtyProcess as any,
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        headlessTerminal: mockHeadlessTerminal as any,
-      });
+      activePtysGetSpy = vi
+        .spyOn(ShellExecutionService['activePtys'], 'get')
+        .mockReturnValue({
+          // eslint-disable-next-line @typescript-eslint/no-explicit-any
+          ptyProcess: mockPtyProcess as any,
+          // eslint-disable-next-line @typescript-eslint/no-explicit-any
+          headlessTerminal: mockHeadlessTerminal as any,
+        });
+    });
+
+    afterEach(() => {
+      activePtysGetSpy.mockRestore();
     });
 
     it('should write to the pty and trigger a render', async () => {

packages/core/src/tools/shell.ts

@@ -18,6 +18,7 @@ import {
   Kind,
   type ToolInvocation,
   type ToolResult,
+  type BackgroundExecutionData,
   type ToolCallConfirmationDetails,
   type ToolExecuteConfirmationDetails,
   type PolicyUpdateOptions,
@@ -150,7 +151,7 @@ export class ShellToolInvocation extends BaseToolInvocation<
     signal: AbortSignal,
     updateOutput?: (output: ToolLiveOutput) => void,
     shellExecutionConfig?: ShellExecutionConfig,
-    setPidCallback?: (pid: number) => void,
+    setExecutionIdCallback?: (executionId: number) => void,
   ): Promise<ToolResult> {
     const strippedCommand = stripShellWrapper(this.params.command);
 
@@ -281,8 +282,8 @@ export class ShellToolInvocation extends BaseToolInvocation<
         );
 
       if (pid) {
-        if (setPidCallback) {
-          setPidCallback(pid);
+        if (setExecutionIdCallback) {
+          setExecutionIdCallback(pid);
         }
 
         // If the model requested to run in the background, do so after a short delay.
@@ -324,7 +325,7 @@ export class ShellToolInvocation extends BaseToolInvocation<
         }
       }
 
-      let data: Record<string, unknown> | undefined;
+      let data: BackgroundExecutionData | undefined;
 
       let llmContent = '';
       let timeoutMessage = '';

packages/core/src/tools/tools.ts

@@ -61,15 +61,51 @@ export interface ToolInvocation<
    * Executes the tool with the validated parameters.
    * @param signal AbortSignal for tool cancellation.
    * @param updateOutput Optional callback to stream output.
+   * @param setExecutionIdCallback Optional callback for tools that expose a background execution handle.
    * @returns Result of the tool execution.
    */
   execute(
     signal: AbortSignal,
     updateOutput?: (output: ToolLiveOutput) => void,
     shellExecutionConfig?: ShellExecutionConfig,
+    setExecutionIdCallback?: (executionId: number) => void,
   ): Promise<TResult>;
 }
 
+/**
+ * Structured payload used by tools to surface background execution metadata to
+ * the CLI UI.
+ *
+ * NOTE: `pid` is used as the canonical identifier for now to stay consistent
+ * with existing types (ExecutingToolCall.pid, ExecutionHandle.pid, etc.).
+ * A future rename to `executionId` is planned once the codebase is fully
+ * migrated — not done in this PR to keep the diff focused on the abstraction.
+ */
+export interface BackgroundExecutionData extends Record<string, unknown> {
+  pid?: number;
+  command?: string;
+  initialOutput?: string;
+}
+
+export function isBackgroundExecutionData(
+  data: unknown,
+): data is BackgroundExecutionData {
+  if (typeof data !== 'object' || data === null) {
+    return false;
+  }
+
+  const pid = 'pid' in data ? data.pid : undefined;
+  const command = 'command' in data ? data.command : undefined;
+  const initialOutput =
+    'initialOutput' in data ? data.initialOutput : undefined;
+
+  return (
+    (pid === undefined || typeof pid === 'number') &&
+    (command === undefined || typeof command === 'string') &&
+    (initialOutput === undefined || typeof initialOutput === 'string')
+  );
+}
+
 /**
  * Options for policy updates that can be customized by tool invocations.
  */