feat(core): refactor shell execution to use node-pty (#6491)

Co-authored-by: Jacob Richman <[email protected]>

6 files changed, 826 insertions, 222 deletions

diff --git a/packages/core/src/config/config.ts b/packages/core/src/config/config.ts
index 5ab39e83..8c95a99d 100644
--- a/packages/core/src/config/config.ts
+++ b/packages/core/src/config/config.ts
@@ -202,6 +202,7 @@ export interface ConfigParameters {
   chatCompression?: ChatCompressionSettings;
   interactive?: boolean;
   trustedFolder?: boolean;
+  shouldUseNodePtyShell?: boolean;
 }
 
 export class Config {
@@ -267,6 +268,7 @@ export class Config {
   private readonly chatCompression: ChatCompressionSettings | undefined;
   private readonly interactive: boolean;
   private readonly trustedFolder: boolean | undefined;
+  private readonly shouldUseNodePtyShell: boolean;
   private initialized: boolean = false;
 
   constructor(params: ConfigParameters) {
@@ -334,6 +336,7 @@ export class Config {
     this.chatCompression = params.chatCompression;
     this.interactive = params.interactive ?? false;
     this.trustedFolder = params.trustedFolder;
+    this.shouldUseNodePtyShell = params.shouldUseNodePtyShell ?? false;
 
     if (params.contextFileName) {
       setGeminiMdFilename(params.contextFileName);
@@ -728,6 +731,10 @@ export class Config {
     return this.interactive;
   }
 
+  getShouldUseNodePtyShell(): boolean {
+    return this.shouldUseNodePtyShell;
+  }
+
   async getGitService(): Promise<GitService> {
     if (!this.gitService) {
       this.gitService = new GitService(this.targetDir);
diff --git a/packages/core/src/services/shellExecutionService.test.ts b/packages/core/src/services/shellExecutionService.test.ts
index 47df12e8..604350aa 100644
--- a/packages/core/src/services/shellExecutionService.test.ts
+++ b/packages/core/src/services/shellExecutionService.test.ts
@@ -5,21 +5,6 @@
  */
 
 import { vi, describe, it, expect, beforeEach, type Mock } from 'vitest';
-const mockSpawn = vi.hoisted(() => vi.fn());
-vi.mock('child_process', () => ({
-  spawn: mockSpawn,
-}));
-
-const mockGetShellConfiguration = vi.hoisted(() => vi.fn());
-let mockIsWindows = false;
-
-vi.mock('../utils/shell-utils.js', () => ({
-  getShellConfiguration: mockGetShellConfiguration,
-  get isWindows() {
-    return mockIsWindows;
-  },
-}));
-
 import EventEmitter from 'events';
 import { Readable } from 'stream';
 import { type ChildProcess } from 'child_process';
@@ -28,17 +13,43 @@ import {
   ShellOutputEvent,
 } from './shellExecutionService.js';
 
+// Hoisted Mocks
+const mockPtySpawn = vi.hoisted(() => vi.fn());
+const mockCpSpawn = vi.hoisted(() => vi.fn());
 const mockIsBinary = vi.hoisted(() => vi.fn());
+const mockPlatform = vi.hoisted(() => vi.fn());
+const mockGetPty = vi.hoisted(() => vi.fn());
+
+// Top-level Mocks
+vi.mock('@lydell/node-pty', () => ({
+  spawn: mockPtySpawn,
+}));
+vi.mock('child_process', () => ({
+  spawn: mockCpSpawn,
+}));
 vi.mock('../utils/textUtils.js', () => ({
   isBinary: mockIsBinary,
 }));
-
-const mockPlatform = vi.hoisted(() => vi.fn());
 vi.mock('os', () => ({
   default: {
     platform: mockPlatform,
+    constants: {
+      signals: {
+        SIGTERM: 15,
+        SIGKILL: 9,
+      },
+    },
   },
   platform: mockPlatform,
+  constants: {
+    signals: {
+      SIGTERM: 15,
+      SIGKILL: 9,
+    },
+  },
+}));
+vi.mock('../utils/getPty.js', () => ({
+  getPty: mockGetPty,
 }));
 
 const mockProcessKill = vi
@@ -46,19 +57,271 @@ const mockProcessKill = vi
   .mockImplementation(() => true);
 
 describe('ShellExecutionService', () => {
-  let mockChildProcess: EventEmitter & Partial<ChildProcess>;
+  let mockPtyProcess: EventEmitter & {
+    pid: number;
+    kill: Mock;
+    onData: Mock;
+    onExit: Mock;
+  };
   let onOutputEventMock: Mock<(event: ShellOutputEvent) => void>;
 
   beforeEach(() => {
     vi.clearAllMocks();
 
     mockIsBinary.mockReturnValue(false);
+    mockPlatform.mockReturnValue('linux');
+    mockGetPty.mockResolvedValue({
+      module: { spawn: mockPtySpawn },
+      name: 'mock-pty',
+    });
+
+    onOutputEventMock = vi.fn();
+
+    mockPtyProcess = new EventEmitter() as EventEmitter & {
+      pid: number;
+      kill: Mock;
+      onData: Mock;
+      onExit: Mock;
+    };
+    mockPtyProcess.pid = 12345;
+    mockPtyProcess.kill = vi.fn();
+    mockPtyProcess.onData = vi.fn();
+    mockPtyProcess.onExit = vi.fn();
+
+    mockPtySpawn.mockReturnValue(mockPtyProcess);
+  });
+
+  // Helper function to run a standard execution simulation
+  const simulateExecution = async (
+    command: string,
+    simulation: (
+      ptyProcess: typeof mockPtyProcess,
+      ac: AbortController,
+    ) => void,
+  ) => {
+    const abortController = new AbortController();
+    const handle = await ShellExecutionService.execute(
+      command,
+      '/test/dir',
+      onOutputEventMock,
+      abortController.signal,
+      true,
+    );
+
+    await new Promise((resolve) => setImmediate(resolve));
+    simulation(mockPtyProcess, abortController);
+    const result = await handle.result;
+    return { result, handle, abortController };
+  };
+
+  describe('Successful Execution', () => {
+    it('should execute a command and capture output', async () => {
+      const { result, handle } = await simulateExecution('ls -l', (pty) => {
+        pty.onData.mock.calls[0][0]('file1.txt\n');
+        pty.onExit.mock.calls[0][0]({ exitCode: 0, signal: null });
+      });
+
+      expect(mockPtySpawn).toHaveBeenCalledWith(
+        'bash',
+        ['-c', 'ls -l'],
+        expect.any(Object),
+      );
+      expect(result.exitCode).toBe(0);
+      expect(result.signal).toBeNull();
+      expect(result.error).toBeNull();
+      expect(result.aborted).toBe(false);
+      expect(result.output).toBe('file1.txt');
+      expect(handle.pid).toBe(12345);
+
+      expect(onOutputEventMock).toHaveBeenCalledWith({
+        type: 'data',
+        chunk: 'file1.txt',
+      });
+    });
+
+    it('should strip ANSI codes from output', async () => {
+      const { result } = await simulateExecution('ls --color=auto', (pty) => {
+        pty.onData.mock.calls[0][0]('a\u001b[31mred\u001b[0mword');
+        pty.onExit.mock.calls[0][0]({ exitCode: 0, signal: null });
+      });
+
+      expect(result.output).toBe('aredword');
+      expect(onOutputEventMock).toHaveBeenCalledWith({
+        type: 'data',
+        chunk: 'aredword',
+      });
+    });
+
+    it('should correctly decode multi-byte characters split across chunks', async () => {
+      const { result } = await simulateExecution('echo "你好"', (pty) => {
+        const multiByteChar = '你好';
+        pty.onData.mock.calls[0][0](multiByteChar.slice(0, 1));
+        pty.onData.mock.calls[0][0](multiByteChar.slice(1));
+        pty.onExit.mock.calls[0][0]({ exitCode: 0, signal: null });
+      });
+      expect(result.output).toBe('你好');
+    });
+
+    it('should handle commands with no output', async () => {
+      const { result } = await simulateExecution('touch file', (pty) => {
+        pty.onExit.mock.calls[0][0]({ exitCode: 0, signal: null });
+      });
+
+      expect(result.output).toBe('');
+      expect(onOutputEventMock).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('Failed Execution', () => {
+    it('should capture a non-zero exit code', async () => {
+      const { result } = await simulateExecution('a-bad-command', (pty) => {
+        pty.onData.mock.calls[0][0]('command not found');
+        pty.onExit.mock.calls[0][0]({ exitCode: 127, signal: null });
+      });
+
+      expect(result.exitCode).toBe(127);
+      expect(result.output).toBe('command not found');
+      expect(result.error).toBeNull();
+    });
+
+    it('should capture a termination signal', async () => {
+      const { result } = await simulateExecution('long-process', (pty) => {
+        pty.onExit.mock.calls[0][0]({ exitCode: 0, signal: 15 });
+      });
+
+      expect(result.exitCode).toBe(0);
+      expect(result.signal).toBe(15);
+    });
+
+    it('should handle a synchronous spawn error', async () => {
+      mockGetPty.mockImplementation(() => null);
+
+      mockCpSpawn.mockImplementation(() => {
+        throw new Error('Simulated PTY spawn error');
+      });
+
+      const handle = await ShellExecutionService.execute(
+        'any-command',
+        '/test/dir',
+        onOutputEventMock,
+        new AbortController().signal,
+        true,
+      );
+      const result = await handle.result;
+
+      expect(result.error).toBeInstanceOf(Error);
+      expect(result.error?.message).toContain('Simulated PTY spawn error');
+      expect(result.exitCode).toBe(1);
+      expect(result.output).toBe('');
+      expect(handle.pid).toBeUndefined();
+    });
+  });
+
+  describe('Aborting Commands', () => {
+    it('should abort a running process and set the aborted flag', async () => {
+      const { result } = await simulateExecution(
+        'sleep 10',
+        (pty, abortController) => {
+          abortController.abort();
+          pty.onExit.mock.calls[0][0]({ exitCode: 1, signal: null });
+        },
+      );
+
+      expect(result.aborted).toBe(true);
+      expect(mockPtyProcess.kill).toHaveBeenCalled();
+    });
+  });
+
+  describe('Binary Output', () => {
+    it('should detect binary output and switch to progress events', async () => {
+      mockIsBinary.mockReturnValueOnce(true);
+      const binaryChunk1 = Buffer.from([0x89, 0x50, 0x4e, 0x47]);
+      const binaryChunk2 = Buffer.from([0x0d, 0x0a, 0x1a, 0x0a]);
+
+      const { result } = await simulateExecution('cat image.png', (pty) => {
+        pty.onData.mock.calls[0][0](binaryChunk1);
+        pty.onData.mock.calls[0][0](binaryChunk2);
+        pty.onExit.mock.calls[0][0]({ exitCode: 0, signal: null });
+      });
 
-    mockGetShellConfiguration.mockReturnValue({
-      executable: 'bash',
-      argsPrefix: ['-c'],
+      expect(result.rawOutput).toEqual(
+        Buffer.concat([binaryChunk1, binaryChunk2]),
+      );
+      expect(onOutputEventMock).toHaveBeenCalledTimes(3);
+      expect(onOutputEventMock.mock.calls[0][0]).toEqual({
+        type: 'binary_detected',
+      });
+      expect(onOutputEventMock.mock.calls[1][0]).toEqual({
+        type: 'binary_progress',
+        bytesReceived: 4,
+      });
+      expect(onOutputEventMock.mock.calls[2][0]).toEqual({
+        type: 'binary_progress',
+        bytesReceived: 8,
+      });
     });
-    mockIsWindows = false;
+
+    it('should not emit data events after binary is detected', async () => {
+      mockIsBinary.mockImplementation((buffer) => buffer.includes(0x00));
+
+      await simulateExecution('cat mixed_file', (pty) => {
+        pty.onData.mock.calls[0][0](Buffer.from('some text'));
+        pty.onData.mock.calls[0][0](Buffer.from([0x00, 0x01, 0x02]));
+        pty.onData.mock.calls[0][0](Buffer.from('more text'));
+        pty.onExit.mock.calls[0][0]({ exitCode: 0, signal: null });
+      });
+
+      const eventTypes = onOutputEventMock.mock.calls.map(
+        (call: [ShellOutputEvent]) => call[0].type,
+      );
+      expect(eventTypes).toEqual([
+        'data',
+        'binary_detected',
+        'binary_progress',
+        'binary_progress',
+      ]);
+    });
+  });
+
+  describe('Platform-Specific Behavior', () => {
+    it('should use cmd.exe on Windows', async () => {
+      mockPlatform.mockReturnValue('win32');
+      await simulateExecution('dir "foo bar"', (pty) =>
+        pty.onExit.mock.calls[0][0]({ exitCode: 0, signal: null }),
+      );
+
+      expect(mockPtySpawn).toHaveBeenCalledWith(
+        'cmd.exe',
+        ['/c', 'dir "foo bar"'],
+        expect.any(Object),
+      );
+    });
+
+    it('should use bash on Linux', async () => {
+      mockPlatform.mockReturnValue('linux');
+      await simulateExecution('ls "foo bar"', (pty) =>
+        pty.onExit.mock.calls[0][0]({ exitCode: 0, signal: null }),
+      );
+
+      expect(mockPtySpawn).toHaveBeenCalledWith(
+        'bash',
+        ['-c', 'ls "foo bar"'],
+        expect.any(Object),
+      );
+    });
+  });
+});
+
+describe('ShellExecutionService child_process fallback', () => {
+  let mockChildProcess: EventEmitter & Partial<ChildProcess>;
+  let onOutputEventMock: Mock<(event: ShellOutputEvent) => void>;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+
+    mockIsBinary.mockReturnValue(false);
+    mockPlatform.mockReturnValue('linux');
+    mockGetPty.mockResolvedValue(null);
 
     onOutputEventMock = vi.fn();
 
@@ -73,7 +336,7 @@ describe('ShellExecutionService', () => {
       configurable: true,
     });
 
-    mockSpawn.mockReturnValue(mockChildProcess);
+    mockCpSpawn.mockReturnValue(mockChildProcess);
   });
 
   // Helper function to run a standard execution simulation
@@ -82,11 +345,12 @@ describe('ShellExecutionService', () => {
     simulation: (cp: typeof mockChildProcess, ac: AbortController) => void,
   ) => {
     const abortController = new AbortController();
-    const handle = ShellExecutionService.execute(
+    const handle = await ShellExecutionService.execute(
       command,
       '/test/dir',
       onOutputEventMock,
       abortController.signal,
+      true,
     );
 
     await new Promise((resolve) => setImmediate(resolve));
@@ -103,7 +367,7 @@ describe('ShellExecutionService', () => {
         cp.emit('exit', 0, null);
       });
 
-      expect(mockSpawn).toHaveBeenCalledWith(
+      expect(mockCpSpawn).toHaveBeenCalledWith(
         'ls -l',
         [],
         expect.objectContaining({ shell: 'bash' }),
@@ -112,19 +376,15 @@ describe('ShellExecutionService', () => {
       expect(result.signal).toBeNull();
       expect(result.error).toBeNull();
       expect(result.aborted).toBe(false);
-      expect(result.stdout).toBe('file1.txt\n');
-      expect(result.stderr).toBe('a warning');
-      expect(result.output).toBe('file1.txt\n\na warning');
+      expect(result.output).toBe('file1.txt\na warning');
       expect(handle.pid).toBe(12345);
 
       expect(onOutputEventMock).toHaveBeenCalledWith({
         type: 'data',
-        stream: 'stdout',
         chunk: 'file1.txt\n',
       });
       expect(onOutputEventMock).toHaveBeenCalledWith({
         type: 'data',
-        stream: 'stderr',
         chunk: 'a warning',
       });
     });
@@ -135,10 +395,9 @@ describe('ShellExecutionService', () => {
         cp.emit('exit', 0, null);
       });
 
-      expect(result.stdout).toBe('aredword');
+      expect(result.output).toBe('aredword');
       expect(onOutputEventMock).toHaveBeenCalledWith({
         type: 'data',
-        stream: 'stdout',
         chunk: 'aredword',
       });
     });
@@ -150,7 +409,7 @@ describe('ShellExecutionService', () => {
         cp.stdout?.emit('data', multiByteChar.slice(2));
         cp.emit('exit', 0, null);
       });
-      expect(result.stdout).toBe('你好');
+      expect(result.output).toBe('你好');
     });
 
     it('should handle commands with no output', async () => {
@@ -158,8 +417,6 @@ describe('ShellExecutionService', () => {
         cp.emit('exit', 0, null);
       });
 
-      expect(result.stdout).toBe('');
-      expect(result.stderr).toBe('');
       expect(result.output).toBe('');
       expect(onOutputEventMock).not.toHaveBeenCalled();
     });
@@ -173,9 +430,7 @@ describe('ShellExecutionService', () => {
       });
 
       expect(result.exitCode).toBe(127);
-      expect(result.stderr).toBe('command not found');
-      expect(result.stdout).toBe('');
-      expect(result.output).toBe('\ncommand not found');
+      expect(result.output).toBe('command not found');
       expect(result.error).toBeNull();
     });
 
@@ -185,7 +440,7 @@ describe('ShellExecutionService', () => {
       });
 
       expect(result.exitCode).toBeNull();
-      expect(result.signal).toBe('SIGTERM');
+      expect(result.signal).toBe(15);
     });
 
     it('should handle a spawn error', async () => {
@@ -247,7 +502,7 @@ describe('ShellExecutionService', () => {
               expectedSignal,
             );
           } else {
-            expect(mockSpawn).toHaveBeenCalledWith(expectedCommand, [
+            expect(mockCpSpawn).toHaveBeenCalledWith(expectedCommand, [
               '/pid',
               String(mockChildProcess.pid),
               '/f',
@@ -265,11 +520,12 @@ describe('ShellExecutionService', () => {
       // Don't await the result inside the simulation block for this specific test.
       // We need to control the timeline manually.
       const abortController = new AbortController();
-      const handle = ShellExecutionService.execute(
+      const handle = await ShellExecutionService.execute(
         'unresponsive_process',
         '/test/dir',
         onOutputEventMock,
         abortController.signal,
+        true,
       );
 
       abortController.abort();
@@ -296,7 +552,7 @@ describe('ShellExecutionService', () => {
       vi.useRealTimers();
 
       expect(result.aborted).toBe(true);
-      expect(result.signal).toBe('SIGKILL');
+      expect(result.signal).toBe(9);
       // The individual kill calls were already asserted above.
       expect(mockProcessKill).toHaveBeenCalledTimes(2);
     });
@@ -341,7 +597,6 @@ describe('ShellExecutionService', () => {
         cp.emit('exit', 0, null);
       });
 
-      // FIX: Provide explicit type for the 'call' parameter in the map function.
       const eventTypes = onOutputEventMock.mock.calls.map(
         (call: [ShellOutputEvent]) => call[0].type,
       );
@@ -361,7 +616,7 @@ describe('ShellExecutionService', () => {
         cp.emit('exit', 0, null),
       );
 
-      expect(mockSpawn).toHaveBeenCalledWith(
+      expect(mockCpSpawn).toHaveBeenCalledWith(
         'dir "foo bar"',
         [],
         expect.objectContaining({
@@ -375,7 +630,7 @@ describe('ShellExecutionService', () => {
       mockPlatform.mockReturnValue('linux');
       await simulateExecution('ls "foo bar"', (cp) => cp.emit('exit', 0, null));
 
-      expect(mockSpawn).toHaveBeenCalledWith(
+      expect(mockCpSpawn).toHaveBeenCalledWith(
         'ls "foo bar"',
         [],
         expect.objectContaining({
@@ -386,3 +641,110 @@ describe('ShellExecutionService', () => {
     });
   });
 });
+
+describe('ShellExecutionService execution method selection', () => {
+  let onOutputEventMock: Mock<(event: ShellOutputEvent) => void>;
+  let mockPtyProcess: EventEmitter & {
+    pid: number;
+    kill: Mock;
+    onData: Mock;
+    onExit: Mock;
+  };
+  let mockChildProcess: EventEmitter & Partial<ChildProcess>;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    onOutputEventMock = vi.fn();
+
+    // Mock for pty
+    mockPtyProcess = new EventEmitter() as EventEmitter & {
+      pid: number;
+      kill: Mock;
+      onData: Mock;
+      onExit: Mock;
+    };
+    mockPtyProcess.pid = 12345;
+    mockPtyProcess.kill = vi.fn();
+    mockPtyProcess.onData = vi.fn();
+    mockPtyProcess.onExit = vi.fn();
+    mockPtySpawn.mockReturnValue(mockPtyProcess);
+    mockGetPty.mockResolvedValue({
+      module: { spawn: mockPtySpawn },
+      name: 'mock-pty',
+    });
+
+    // Mock for child_process
+    mockChildProcess = new EventEmitter() as EventEmitter &
+      Partial<ChildProcess>;
+    mockChildProcess.stdout = new EventEmitter() as Readable;
+    mockChildProcess.stderr = new EventEmitter() as Readable;
+    mockChildProcess.kill = vi.fn();
+    Object.defineProperty(mockChildProcess, 'pid', {
+      value: 54321,
+      configurable: true,
+    });
+    mockCpSpawn.mockReturnValue(mockChildProcess);
+  });
+
+  it('should use node-pty when shouldUseNodePty is true and pty is available', async () => {
+    const abortController = new AbortController();
+    const handle = await ShellExecutionService.execute(
+      'test command',
+      '/test/dir',
+      onOutputEventMock,
+      abortController.signal,
+      true, // shouldUseNodePty
+    );
+
+    // Simulate exit to allow promise to resolve
+    mockPtyProcess.onExit.mock.calls[0][0]({ exitCode: 0, signal: null });
+    const result = await handle.result;
+
+    expect(mockGetPty).toHaveBeenCalled();
+    expect(mockPtySpawn).toHaveBeenCalled();
+    expect(mockCpSpawn).not.toHaveBeenCalled();
+    expect(result.executionMethod).toBe('mock-pty');
+  });
+
+  it('should use child_process when shouldUseNodePty is false', async () => {
+    const abortController = new AbortController();
+    const handle = await ShellExecutionService.execute(
+      'test command',
+      '/test/dir',
+      onOutputEventMock,
+      abortController.signal,
+      false, // shouldUseNodePty
+    );
+
+    // Simulate exit to allow promise to resolve
+    mockChildProcess.emit('exit', 0, null);
+    const result = await handle.result;
+
+    expect(mockGetPty).not.toHaveBeenCalled();
+    expect(mockPtySpawn).not.toHaveBeenCalled();
+    expect(mockCpSpawn).toHaveBeenCalled();
+    expect(result.executionMethod).toBe('child_process');
+  });
+
+  it('should fall back to child_process if pty is not available even if shouldUseNodePty is true', async () => {
+    mockGetPty.mockResolvedValue(null);
+
+    const abortController = new AbortController();
+    const handle = await ShellExecutionService.execute(
+      'test command',
+      '/test/dir',
+      onOutputEventMock,
+      abortController.signal,
+      true, // shouldUseNodePty
+    );
+
+    // Simulate exit to allow promise to resolve
+    mockChildProcess.emit('exit', 0, null);
+    const result = await handle.result;
+
+    expect(mockGetPty).toHaveBeenCalled();
+    expect(mockPtySpawn).not.toHaveBeenCalled();
+    expect(mockCpSpawn).toHaveBeenCalled();
+    expect(result.executionMethod).toBe('child_process');
+  });
+});
diff --git a/packages/core/src/services/shellExecutionService.ts b/packages/core/src/services/shellExecutionService.ts
index 3749fcf6..59e998bd 100644
--- a/packages/core/src/services/shellExecutionService.ts
+++ b/packages/core/src/services/shellExecutionService.ts
@@ -4,35 +4,47 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { spawn } from 'child_process';
+import { getPty, PtyImplementation } from '../utils/getPty.js';
+import { spawn as cpSpawn } from 'child_process';
 import { TextDecoder } from 'util';
 import os from 'os';
-import stripAnsi from 'strip-ansi';
 import { getCachedEncodingForBuffer } from '../utils/systemEncoding.js';
 import { isBinary } from '../utils/textUtils.js';
+import pkg from '@xterm/headless';
+import stripAnsi from 'strip-ansi';
+const { Terminal } = pkg;
 
 const SIGKILL_TIMEOUT_MS = 200;
 
+// @ts-expect-error getFullText is not a public API.
+const getFullText = (terminal: Terminal) => {
+  const buffer = terminal.buffer.active;
+  const lines: string[] = [];
+  for (let i = 0; i < buffer.length; i++) {
+    const line = buffer.getLine(i);
+    lines.push(line ? line.translateToString(true) : '');
+  }
+  return lines.join('\n').trim();
+};
+
 /** A structured result from a shell command execution. */
 export interface ShellExecutionResult {
   /** The raw, unprocessed output buffer. */
   rawOutput: Buffer;
-  /** The combined, decoded stdout and stderr as a string. */
+  /** The combined, decoded output as a string. */
   output: string;
-  /** The decoded stdout as a string. */
-  stdout: string;
-  /** The decoded stderr as a string. */
-  stderr: string;
   /** The process exit code, or null if terminated by a signal. */
   exitCode: number | null;
   /** The signal that terminated the process, if any. */
-  signal: NodeJS.Signals | null;
+  signal: number | null;
   /** An error object if the process failed to spawn. */
   error: Error | null;
   /** A boolean indicating if the command was aborted by the user. */
   aborted: boolean;
   /** The process ID of the spawned shell. */
   pid: number | undefined;
+  /** The method used to execute the shell command. */
+  executionMethod: 'lydell-node-pty' | 'node-pty' | 'child_process' | 'none';
 }
 
 /** A handle for an ongoing shell execution. */
@@ -50,8 +62,6 @@ export type ShellOutputEvent =
   | {
       /** The event contains a chunk of output data. */
       type: 'data';
-      /** The stream from which the data originated. */
-      stream: 'stdout' | 'stderr';
       /** The decoded string chunk. */
       chunk: string;
     }
@@ -73,7 +83,7 @@ export type ShellOutputEvent =
  */
 export class ShellExecutionService {
   /**
-   * Executes a shell command using `spawn`, capturing all output and lifecycle events.
+   * Executes a shell command using `node-pty`, capturing all output and lifecycle events.
    *
    * @param commandToExecute The exact command string to run.
    * @param cwd The working directory to execute the command in.
@@ -82,172 +92,369 @@ export class ShellExecutionService {
    * @returns An object containing the process ID (pid) and a promise that
    *          resolves with the complete execution result.
    */
-  static execute(
+  static async execute(
     commandToExecute: string,
     cwd: string,
     onOutputEvent: (event: ShellOutputEvent) => void,
     abortSignal: AbortSignal,
-  ): ShellExecutionHandle {
-    const isWindows = os.platform() === 'win32';
+    shouldUseNodePty: boolean,
+    terminalColumns?: number,
+    terminalRows?: number,
+  ): Promise<ShellExecutionHandle> {
+    if (shouldUseNodePty) {
+      const ptyInfo = await getPty();
+      if (ptyInfo) {
+        try {
+          return this.executeWithPty(
+            commandToExecute,
+            cwd,
+            onOutputEvent,
+            abortSignal,
+            terminalColumns,
+            terminalRows,
+            ptyInfo,
+          );
+        } catch (_e) {
+          // Fallback to child_process
+        }
+      }
+    }
 
-    const child = spawn(commandToExecute, [], {
+    return this.childProcessFallback(
+      commandToExecute,
       cwd,
-      stdio: ['ignore', 'pipe', 'pipe'],
-      // Use bash unless in Windows (since it doesn't support bash).
-      // For windows, just use the default.
-      shell: isWindows ? true : 'bash',
-      // Use process groups on non-Windows for robust killing.
-      // Windows process termination is handled by `taskkill /t`.
-      detached: !isWindows,
-      env: {
-        ...process.env,
-        GEMINI_CLI: '1',
-      },
-    });
+      onOutputEvent,
+      abortSignal,
+    );
+  }
+
+  private static childProcessFallback(
+    commandToExecute: string,
+    cwd: string,
+    onOutputEvent: (event: ShellOutputEvent) => void,
+    abortSignal: AbortSignal,
+  ): ShellExecutionHandle {
+    try {
+      const isWindows = os.platform() === 'win32';
 
-    const result = new Promise<ShellExecutionResult>((resolve) => {
-      // Use decoders to handle multi-byte characters safely (for streaming output).
-      let stdoutDecoder: TextDecoder | null = null;
-      let stderrDecoder: TextDecoder | null = null;
+      const child = cpSpawn(commandToExecute, [], {
+        cwd,
+        stdio: ['ignore', 'pipe', 'pipe'],
+        shell: isWindows ? true : 'bash',
+        detached: !isWindows,
+        env: {
+          ...process.env,
+          GEMINI_CLI: '1',
+          TERM: 'xterm-256color',
+          PAGER: 'cat',
+        },
+      });
 
-      let stdout = '';
-      let stderr = '';
-      const outputChunks: Buffer[] = [];
-      let error: Error | null = null;
-      let exited = false;
+      const result = new Promise<ShellExecutionResult>((resolve) => {
+        let stdoutDecoder: TextDecoder | null = null;
+        let stderrDecoder: TextDecoder | null = null;
 
-      let isStreamingRawContent = true;
-      const MAX_SNIFF_SIZE = 4096;
-      let sniffedBytes = 0;
+        let stdout = '';
+        let stderr = '';
+        const outputChunks: Buffer[] = [];
+        let error: Error | null = null;
+        let exited = false;
 
-      const handleOutput = (data: Buffer, stream: 'stdout' | 'stderr') => {
-        if (!stdoutDecoder || !stderrDecoder) {
-          const encoding = getCachedEncodingForBuffer(data);
-          try {
-            stdoutDecoder = new TextDecoder(encoding);
-            stderrDecoder = new TextDecoder(encoding);
-          } catch {
-            // If the encoding is not supported, fall back to utf-8.
-            // This can happen on some platforms for certain encodings like 'utf-32le'.
-            stdoutDecoder = new TextDecoder('utf-8');
-            stderrDecoder = new TextDecoder('utf-8');
+        let isStreamingRawContent = true;
+        const MAX_SNIFF_SIZE = 4096;
+        let sniffedBytes = 0;
+
+        const handleOutput = (data: Buffer, stream: 'stdout' | 'stderr') => {
+          if (!stdoutDecoder || !stderrDecoder) {
+            const encoding = getCachedEncodingForBuffer(data);
+            try {
+              stdoutDecoder = new TextDecoder(encoding);
+              stderrDecoder = new TextDecoder(encoding);
+            } catch {
+              stdoutDecoder = new TextDecoder('utf-8');
+              stderrDecoder = new TextDecoder('utf-8');
+            }
           }
-        }
 
-        outputChunks.push(data);
+          outputChunks.push(data);
+
+          if (isStreamingRawContent && sniffedBytes < MAX_SNIFF_SIZE) {
+            const sniffBuffer = Buffer.concat(outputChunks.slice(0, 20));
+            sniffedBytes = sniffBuffer.length;
 
-        // Binary detection logic. This only runs until we've made a determination.
-        if (isStreamingRawContent && sniffedBytes < MAX_SNIFF_SIZE) {
-          const sniffBuffer = Buffer.concat(outputChunks.slice(0, 20));
-          sniffedBytes = sniffBuffer.length;
+            if (isBinary(sniffBuffer)) {
+              isStreamingRawContent = false;
+              onOutputEvent({ type: 'binary_detected' });
+            }
+          }
+
+          const decoder = stream === 'stdout' ? stdoutDecoder : stderrDecoder;
+          const decodedChunk = decoder.decode(data, { stream: true });
+          const strippedChunk = stripAnsi(decodedChunk);
 
-          if (isBinary(sniffBuffer)) {
-            // Change state to stop streaming raw content.
-            isStreamingRawContent = false;
-            onOutputEvent({ type: 'binary_detected' });
+          if (stream === 'stdout') {
+            stdout += strippedChunk;
+          } else {
+            stderr += strippedChunk;
           }
-        }
 
-        const decodedChunk =
-          stream === 'stdout'
-            ? stdoutDecoder.decode(data, { stream: true })
-            : stderrDecoder.decode(data, { stream: true });
-        const strippedChunk = stripAnsi(decodedChunk);
+          if (isStreamingRawContent) {
+            onOutputEvent({ type: 'data', chunk: strippedChunk });
+          } else {
+            const totalBytes = outputChunks.reduce(
+              (sum, chunk) => sum + chunk.length,
+              0,
+            );
+            onOutputEvent({
+              type: 'binary_progress',
+              bytesReceived: totalBytes,
+            });
+          }
+        };
 
-        if (stream === 'stdout') {
-          stdout += strippedChunk;
-        } else {
-          stderr += strippedChunk;
-        }
+        const handleExit = (
+          code: number | null,
+          signal: NodeJS.Signals | null,
+        ) => {
+          const { finalBuffer } = cleanup();
+          // Ensure we don't add an extra newline if stdout already ends with one.
+          const separator = stdout.endsWith('\n') ? '' : '\n';
+          const combinedOutput =
+            stdout + (stderr ? (stdout ? separator : '') + stderr : '');
 
-        if (isStreamingRawContent) {
-          onOutputEvent({ type: 'data', stream, chunk: strippedChunk });
-        } else {
-          const totalBytes = outputChunks.reduce(
-            (sum, chunk) => sum + chunk.length,
-            0,
-          );
-          onOutputEvent({ type: 'binary_progress', bytesReceived: totalBytes });
-        }
-      };
+          resolve({
+            rawOutput: finalBuffer,
+            output: combinedOutput.trim(),
+            exitCode: code,
+            signal: signal ? os.constants.signals[signal] : null,
+            error,
+            aborted: abortSignal.aborted,
+            pid: child.pid,
+            executionMethod: 'child_process',
+          });
+        };
 
-      child.stdout.on('data', (data) => handleOutput(data, 'stdout'));
-      child.stderr.on('data', (data) => handleOutput(data, 'stderr'));
-      child.on('error', (err) => {
-        const { stdout, stderr, finalBuffer } = cleanup();
-        error = err;
-        resolve({
-          error,
-          stdout,
-          stderr,
-          rawOutput: finalBuffer,
-          output: stdout + (stderr ? `\n${stderr}` : ''),
-          exitCode: 1,
-          signal: null,
-          aborted: false,
-          pid: child.pid,
+        child.stdout.on('data', (data) => handleOutput(data, 'stdout'));
+        child.stderr.on('data', (data) => handleOutput(data, 'stderr'));
+        child.on('error', (err) => {
+          error = err;
+          handleExit(1, null);
         });
-      });
 
-      const abortHandler = async () => {
-        if (child.pid && !exited) {
-          if (isWindows) {
-            spawn('taskkill', ['/pid', child.pid.toString(), '/f', '/t']);
-          } else {
-            try {
-              // Kill the entire process group (negative PID).
-              // SIGTERM first, then SIGKILL if it doesn't die.
-              process.kill(-child.pid, 'SIGTERM');
-              await new Promise((res) => setTimeout(res, SIGKILL_TIMEOUT_MS));
-              if (!exited) {
-                process.kill(-child.pid, 'SIGKILL');
+        const abortHandler = async () => {
+          if (child.pid && !exited) {
+            if (isWindows) {
+              cpSpawn('taskkill', ['/pid', child.pid.toString(), '/f', '/t']);
+            } else {
+              try {
+                process.kill(-child.pid, 'SIGTERM');
+                await new Promise((res) => setTimeout(res, SIGKILL_TIMEOUT_MS));
+                if (!exited) {
+                  process.kill(-child.pid, 'SIGKILL');
+                }
+              } catch (_e) {
+                if (!exited) child.kill('SIGKILL');
               }
-            } catch (_e) {
-              // Fall back to killing just the main process if group kill fails.
-              if (!exited) child.kill('SIGKILL');
             }
           }
+        };
+
+        abortSignal.addEventListener('abort', abortHandler, { once: true });
+
+        child.on('exit', (code, signal) => {
+          handleExit(code, signal);
+        });
+
+        function cleanup() {
+          exited = true;
+          abortSignal.removeEventListener('abort', abortHandler);
+          if (stdoutDecoder) {
+            const remaining = stdoutDecoder.decode();
+            if (remaining) {
+              stdout += stripAnsi(remaining);
+            }
+          }
+          if (stderrDecoder) {
+            const remaining = stderrDecoder.decode();
+            if (remaining) {
+              stderr += stripAnsi(remaining);
+            }
+          }
+
+          const finalBuffer = Buffer.concat(outputChunks);
+
+          return { stdout, stderr, finalBuffer };
         }
+      });
+
+      return { pid: child.pid, result };
+    } catch (e) {
+      const error = e as Error;
+      return {
+        pid: undefined,
+        result: Promise.resolve({
+          error,
+          rawOutput: Buffer.from(''),
+          output: '',
+          exitCode: 1,
+          signal: null,
+          aborted: false,
+          pid: undefined,
+          executionMethod: 'none',
+        }),
       };
+    }
+  }
 
-      abortSignal.addEventListener('abort', abortHandler, { once: true });
+  private static executeWithPty(
+    commandToExecute: string,
+    cwd: string,
+    onOutputEvent: (event: ShellOutputEvent) => void,
+    abortSignal: AbortSignal,
+    terminalColumns: number | undefined,
+    terminalRows: number | undefined,
+    ptyInfo: PtyImplementation | undefined,
+  ): ShellExecutionHandle {
+    try {
+      const cols = terminalColumns ?? 80;
+      const rows = terminalRows ?? 30;
+      const isWindows = os.platform() === 'win32';
+      const shell = isWindows ? 'cmd.exe' : 'bash';
+      const args = isWindows
+        ? ['/c', commandToExecute]
+        : ['-c', commandToExecute];
 
-      child.on('exit', (code: number, signal: NodeJS.Signals) => {
-        const { stdout, stderr, finalBuffer } = cleanup();
+      const ptyProcess = ptyInfo?.module.spawn(shell, args, {
+        cwd,
+        name: 'xterm-color',
+        cols,
+        rows,
+        env: {
+          ...process.env,
+          GEMINI_CLI: '1',
+          TERM: 'xterm-256color',
+          PAGER: 'cat',
+        },
+        handleFlowControl: true,
+      });
 
-        resolve({
-          rawOutput: finalBuffer,
-          output: stdout + (stderr ? `\n${stderr}` : ''),
-          stdout,
-          stderr,
-          exitCode: code,
-          signal,
-          error,
-          aborted: abortSignal.aborted,
-          pid: child.pid,
+      const result = new Promise<ShellExecutionResult>((resolve) => {
+        const headlessTerminal = new Terminal({
+          allowProposedApi: true,
+          cols,
+          rows,
         });
-      });
+        let processingChain = Promise.resolve();
+        let decoder: TextDecoder | null = null;
+        let output = '';
+        const outputChunks: Buffer[] = [];
+        const error: Error | null = null;
+        let exited = false;
 
-      /**
-       * Cleans up a process (and it's accompanying state) that is exiting or
-       * erroring and returns output formatted output buffers and strings
-       */
-      function cleanup() {
-        exited = true;
-        abortSignal.removeEventListener('abort', abortHandler);
-        if (stdoutDecoder) {
-          stdout += stripAnsi(stdoutDecoder.decode());
-        }
-        if (stderrDecoder) {
-          stderr += stripAnsi(stderrDecoder.decode());
-        }
+        let isStreamingRawContent = true;
+        const MAX_SNIFF_SIZE = 4096;
+        let sniffedBytes = 0;
 
-        const finalBuffer = Buffer.concat(outputChunks);
+        const handleOutput = (data: Buffer) => {
+          processingChain = processingChain.then(
+            () =>
+              new Promise<void>((resolve) => {
+                if (!decoder) {
+                  const encoding = getCachedEncodingForBuffer(data);
+                  try {
+                    decoder = new TextDecoder(encoding);
+                  } catch {
+                    decoder = new TextDecoder('utf-8');
+                  }
+                }
 
-        return { stdout, stderr, finalBuffer };
-      }
-    });
+                outputChunks.push(data);
+
+                if (isStreamingRawContent && sniffedBytes < MAX_SNIFF_SIZE) {
+                  const sniffBuffer = Buffer.concat(outputChunks.slice(0, 20));
+                  sniffedBytes = sniffBuffer.length;
+
+                  if (isBinary(sniffBuffer)) {
+                    isStreamingRawContent = false;
+                    onOutputEvent({ type: 'binary_detected' });
+                  }
+                }
+
+                if (isStreamingRawContent) {
+                  const decodedChunk = decoder.decode(data, { stream: true });
+                  headlessTerminal.write(decodedChunk, () => {
+                    const newStrippedOutput = getFullText(headlessTerminal);
+                    output = newStrippedOutput;
+                    onOutputEvent({ type: 'data', chunk: newStrippedOutput });
+                    resolve();
+                  });
+                } else {
+                  const totalBytes = outputChunks.reduce(
+                    (sum, chunk) => sum + chunk.length,
+                    0,
+                  );
+                  onOutputEvent({
+                    type: 'binary_progress',
+                    bytesReceived: totalBytes,
+                  });
+                  resolve();
+                }
+              }),
+          );
+        };
+
+        ptyProcess.onData((data: string) => {
+          const bufferData = Buffer.from(data, 'utf-8');
+          handleOutput(bufferData);
+        });
+
+        ptyProcess.onExit(
+          ({ exitCode, signal }: { exitCode: number; signal?: number }) => {
+            exited = true;
+            abortSignal.removeEventListener('abort', abortHandler);
+
+            processingChain.then(() => {
+              const finalBuffer = Buffer.concat(outputChunks);
 
-    return { pid: child.pid, result };
+              resolve({
+                rawOutput: finalBuffer,
+                output,
+                exitCode,
+                signal: signal ?? null,
+                error,
+                aborted: abortSignal.aborted,
+                pid: ptyProcess.pid,
+                executionMethod: ptyInfo?.name ?? 'node-pty',
+              });
+            });
+          },
+        );
+
+        const abortHandler = async () => {
+          if (ptyProcess.pid && !exited) {
+            ptyProcess.kill('SIGHUP');
+          }
+        };
+
+        abortSignal.addEventListener('abort', abortHandler, { once: true });
+      });
+
+      return { pid: ptyProcess.pid, result };
+    } catch (e) {
+      const error = e as Error;
+      return {
+        pid: undefined,
+        result: Promise.resolve({
+          error,
+          rawOutput: Buffer.from(''),
+          output: '',
+          exitCode: 1,
+          signal: null,
+          aborted: false,
+          pid: undefined,
+          executionMethod: 'none',
+        }),
+      };
+    }
   }
 }
diff --git a/packages/core/src/tools/shell.test.ts b/packages/core/src/tools/shell.test.ts
index c0b409fa..79354cf8 100644
--- a/packages/core/src/tools/shell.test.ts
+++ b/packages/core/src/tools/shell.test.ts
@@ -56,6 +56,7 @@ describe('ShellTool', () => {
       getSummarizeToolOutputConfig: vi.fn().mockReturnValue(undefined),
       getWorkspaceContext: () => createMockWorkspaceContext('.'),
       getGeminiClient: vi.fn(),
+      getShouldUseNodePtyShell: vi.fn().mockReturnValue(false),
     } as unknown as Config;
 
     shellTool = new ShellTool(mockConfig);
@@ -123,13 +124,12 @@ describe('ShellTool', () => {
       const fullResult: ShellExecutionResult = {
         rawOutput: Buffer.from(result.output || ''),
         output: 'Success',
-        stdout: 'Success',
-        stderr: '',
         exitCode: 0,
         signal: null,
         error: null,
         aborted: false,
         pid: 12345,
+        executionMethod: 'child_process',
         ...result,
       };
       resolveExecutionPromise(fullResult);
@@ -152,6 +152,9 @@ describe('ShellTool', () => {
         expect.any(String),
         expect.any(Function),
         mockAbortSignal,
+        false,
+        undefined,
+        undefined,
       );
       expect(result.llmContent).toContain('Background PIDs: 54322');
       expect(vi.mocked(fs.unlinkSync)).toHaveBeenCalledWith(tmpFile);
@@ -164,13 +167,12 @@ describe('ShellTool', () => {
       resolveShellExecution({
         rawOutput: Buffer.from(''),
         output: '',
-        stdout: '',
-        stderr: '',
         exitCode: 0,
         signal: null,
         error: null,
         aborted: false,
         pid: 12345,
+        executionMethod: 'child_process',
       });
       await promise;
       expect(mockShellExecutionService).toHaveBeenCalledWith(
@@ -178,6 +180,9 @@ describe('ShellTool', () => {
         expect.any(String),
         expect.any(Function),
         mockAbortSignal,
+        false,
+        undefined,
+        undefined,
       );
     });
 
@@ -189,16 +194,14 @@ describe('ShellTool', () => {
         error,
         exitCode: 1,
         output: 'err',
-        stderr: 'err',
         rawOutput: Buffer.from('err'),
-        stdout: '',
         signal: null,
         aborted: false,
         pid: 12345,
+        executionMethod: 'child_process',
       });
 
       const result = await promise;
-      // The final llmContent should contain the user's command, not the wrapper
       expect(result.llmContent).toContain('Error: wrapped command failed');
       expect(result.llmContent).not.toContain('pgrep');
     });
@@ -231,13 +234,12 @@ describe('ShellTool', () => {
       resolveExecutionPromise({
         output: 'long output',
         rawOutput: Buffer.from('long output'),
-        stdout: 'long output',
-        stderr: '',
         exitCode: 0,
         signal: null,
         error: null,
         aborted: false,
         pid: 12345,
+        executionMethod: 'child_process',
       });
 
       const result = await promise;
@@ -283,7 +285,6 @@ describe('ShellTool', () => {
         // First chunk, should be throttled.
         mockShellOutputCallback({
           type: 'data',
-          stream: 'stdout',
           chunk: 'hello ',
         });
         expect(updateOutputMock).not.toHaveBeenCalled();
@@ -294,24 +295,22 @@ describe('ShellTool', () => {
         // Send a second chunk. THIS event triggers the update with the CUMULATIVE content.
         mockShellOutputCallback({
           type: 'data',
-          stream: 'stderr',
-          chunk: 'world',
+          chunk: 'hello world',
         });
 
         // It should have been called once now with the combined output.
         expect(updateOutputMock).toHaveBeenCalledOnce();
-        expect(updateOutputMock).toHaveBeenCalledWith('hello \nworld');
+        expect(updateOutputMock).toHaveBeenCalledWith('hello world');
 
         resolveExecutionPromise({
           rawOutput: Buffer.from(''),
           output: '',
-          stdout: '',
-          stderr: '',
           exitCode: 0,
           signal: null,
           error: null,
           aborted: false,
           pid: 12345,
+          executionMethod: 'child_process',
         });
         await promise;
       });
@@ -350,13 +349,12 @@ describe('ShellTool', () => {
         resolveExecutionPromise({
           rawOutput: Buffer.from(''),
           output: '',
-          stdout: '',
-          stderr: '',
           exitCode: 0,
           signal: null,
           error: null,
           aborted: false,
           pid: 12345,
+          executionMethod: 'child_process',
         });
         await promise;
       });
diff --git a/packages/core/src/tools/shell.ts b/packages/core/src/tools/shell.ts
index 8d5c624c..3fce7c2d 100644
--- a/packages/core/src/tools/shell.ts
+++ b/packages/core/src/tools/shell.ts
@@ -96,6 +96,8 @@ class ShellToolInvocation extends BaseToolInvocation<
   async execute(
     signal: AbortSignal,
     updateOutput?: (output: string) => void,
+    terminalColumns?: number,
+    terminalRows?: number,
   ): Promise<ToolResult> {
     const strippedCommand = stripShellWrapper(this.params.command);
 
@@ -128,13 +130,11 @@ class ShellToolInvocation extends BaseToolInvocation<
         this.params.directory || '',
       );
 
-      let cumulativeStdout = '';
-      let cumulativeStderr = '';
-
+      let cumulativeOutput = '';
       let lastUpdateTime = Date.now();
       let isBinaryStream = false;
 
-      const { result: resultPromise } = ShellExecutionService.execute(
+      const { result: resultPromise } = await ShellExecutionService.execute(
         commandToExecute,
         cwd,
         (event: ShellOutputEvent) => {
@@ -147,15 +147,9 @@ class ShellToolInvocation extends BaseToolInvocation<
 
           switch (event.type) {
             case 'data':
-              if (isBinaryStream) break; // Don't process text if we are in binary mode
-              if (event.stream === 'stdout') {
-                cumulativeStdout += event.chunk;
-              } else {
-                cumulativeStderr += event.chunk;
-              }
-              currentDisplayOutput =
-                cumulativeStdout +
-                (cumulativeStderr ? `\n${cumulativeStderr}` : '');
+              if (isBinaryStream) break;
+              cumulativeOutput = event.chunk;
+              currentDisplayOutput = cumulativeOutput;
               if (Date.now() - lastUpdateTime > OUTPUT_UPDATE_INTERVAL_MS) {
                 shouldUpdate = true;
               }
@@ -186,6 +180,9 @@ class ShellToolInvocation extends BaseToolInvocation<
           }
         },
         signal,
+        this.config.getShouldUseNodePtyShell(),
+        terminalColumns,
+        terminalRows,
       );
 
       const result = await resultPromise;
@@ -217,7 +214,7 @@ class ShellToolInvocation extends BaseToolInvocation<
       if (result.aborted) {
         llmContent = 'Command was cancelled by user before it could complete.';
         if (result.output.trim()) {
-          llmContent += ` Below is the output (on stdout and stderr) before it was cancelled:\n${result.output}`;
+          llmContent += ` Below is the output before it was cancelled:\n${result.output}`;
         } else {
           llmContent += ' There was no output before it was cancelled.';
         }
@@ -231,8 +228,7 @@ class ShellToolInvocation extends BaseToolInvocation<
         llmContent = [
           `Command: ${this.params.command}`,
           `Directory: ${this.params.directory || '(root)'}`,
-          `Stdout: ${result.stdout || '(empty)'}`,
-          `Stderr: ${result.stderr || '(empty)'}`,
+          `Output: ${result.output || '(empty)'}`,
           `Error: ${finalError}`, // Use the cleaned error string.
           `Exit Code: ${result.exitCode ?? '(none)'}`,
           `Signal: ${result.signal ?? '(none)'}`,
diff --git a/packages/core/src/utils/getPty.ts b/packages/core/src/utils/getPty.ts
new file mode 100644
index 00000000..2d7cb16f
--- /dev/null
+++ b/packages/core/src/utils/getPty.ts
@@ -0,0 +1,34 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+export type PtyImplementation = {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  module: any;
+  name: 'lydell-node-pty' | 'node-pty';
+} | null;
+
+export interface PtyProcess {
+  readonly pid: number;
+  onData(callback: (data: string) => void): void;
+  onExit(callback: (e: { exitCode: number; signal?: number }) => void): void;
+  kill(signal?: string): void;
+}
+
+export const getPty = async (): Promise<PtyImplementation> => {
+  try {
+    const lydell = '@lydell/node-pty';
+    const module = await import(lydell);
+    return { module, name: 'lydell-node-pty' };
+  } catch (_e) {
+    try {
+      const nodePty = 'node-pty';
+      const module = await import(nodePty);
+      return { module, name: 'node-pty' };
+    } catch (_e2) {
+      return null;
+    }
+  }
+};