fix: prevent hangs in non-interactive mode and improve agent guidance (#20893)

Co-authored-by: Keith Schaab <keith.schaab@gmail.com>

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

@@ -1703,4 +1703,95 @@ describe('ShellExecutionService environment variables', () => {
     mockChildProcess.emit('close', 0, null);
     await new Promise(process.nextTick);
   });
+
+  it('should include headless git and gh environment variables in non-interactive mode and append git config safely', async () => {
+    vi.resetModules();
+    vi.stubEnv('GIT_CONFIG_COUNT', '2');
+    vi.stubEnv('GIT_CONFIG_KEY_0', 'core.editor');
+    vi.stubEnv('GIT_CONFIG_VALUE_0', 'vim');
+    vi.stubEnv('GIT_CONFIG_KEY_1', 'pull.rebase');
+    vi.stubEnv('GIT_CONFIG_VALUE_1', 'true');
+
+    const { ShellExecutionService } = await import(
+      './shellExecutionService.js'
+    );
+
+    mockGetPty.mockResolvedValue(null); // Force child_process fallback
+    await ShellExecutionService.execute(
+      'test-cp-headless-git',
+      '/',
+      vi.fn(),
+      new AbortController().signal,
+      false, // non-interactive
+      shellExecutionConfig,
+    );
+
+    expect(mockCpSpawn).toHaveBeenCalled();
+    const cpEnv = mockCpSpawn.mock.calls[0][2].env;
+    expect(cpEnv).toHaveProperty('GIT_TERMINAL_PROMPT', '0');
+    expect(cpEnv).toHaveProperty('GIT_ASKPASS', '');
+    expect(cpEnv).toHaveProperty('SSH_ASKPASS', '');
+    expect(cpEnv).toHaveProperty('GH_PROMPT_DISABLED', '1');
+    expect(cpEnv).toHaveProperty('GCM_INTERACTIVE', 'never');
+    expect(cpEnv).toHaveProperty('DISPLAY', '');
+    expect(cpEnv).toHaveProperty('DBUS_SESSION_BUS_ADDRESS', '');
+
+    // Existing values should be preserved
+    expect(cpEnv).toHaveProperty('GIT_CONFIG_KEY_0', 'core.editor');
+    expect(cpEnv).toHaveProperty('GIT_CONFIG_VALUE_0', 'vim');
+    expect(cpEnv).toHaveProperty('GIT_CONFIG_KEY_1', 'pull.rebase');
+    expect(cpEnv).toHaveProperty('GIT_CONFIG_VALUE_1', 'true');
+
+    // The new credential.helper override should be appended at index 2
+    expect(cpEnv).toHaveProperty('GIT_CONFIG_COUNT', '3');
+    expect(cpEnv).toHaveProperty('GIT_CONFIG_KEY_2', 'credential.helper');
+    expect(cpEnv).toHaveProperty('GIT_CONFIG_VALUE_2', '');
+
+    // Ensure child_process exits
+    mockChildProcess.emit('exit', 0, null);
+    mockChildProcess.emit('close', 0, null);
+    await new Promise(process.nextTick);
+
+    vi.unstubAllEnvs();
+  });
+
+  it('should NOT include headless git and gh environment variables in interactive fallback mode', async () => {
+    vi.resetModules();
+    vi.stubEnv('GIT_TERMINAL_PROMPT', undefined);
+    vi.stubEnv('GIT_ASKPASS', undefined);
+    vi.stubEnv('SSH_ASKPASS', undefined);
+    vi.stubEnv('GH_PROMPT_DISABLED', undefined);
+    vi.stubEnv('GCM_INTERACTIVE', undefined);
+    vi.stubEnv('GIT_CONFIG_COUNT', undefined);
+
+    const { ShellExecutionService } = await import(
+      './shellExecutionService.js'
+    );
+
+    mockGetPty.mockResolvedValue(null); // Force child_process fallback
+    await ShellExecutionService.execute(
+      'test-cp-interactive-fallback',
+      '/',
+      vi.fn(),
+      new AbortController().signal,
+      true, // isInteractive (shouldUseNodePty)
+      shellExecutionConfig,
+    );
+
+    expect(mockCpSpawn).toHaveBeenCalled();
+    const cpEnv = mockCpSpawn.mock.calls[0][2].env;
+    expect(cpEnv).not.toHaveProperty('GIT_TERMINAL_PROMPT');
+    expect(cpEnv).not.toHaveProperty('GIT_ASKPASS');
+    expect(cpEnv).not.toHaveProperty('SSH_ASKPASS');
+    expect(cpEnv).not.toHaveProperty('GH_PROMPT_DISABLED');
+    expect(cpEnv).not.toHaveProperty('GCM_INTERACTIVE');
+    expect(cpEnv).not.toHaveProperty('GIT_CONFIG_COUNT');
+
+    // Ensure child_process exits
+    mockChildProcess.emit('exit', 0, null);
+    mockChildProcess.emit('close', 0, null);
+    await new Promise(process.nextTick);
+
+    vi.unstubAllEnvs();
+  });
 });

packages/core/src/services/shellExecutionService.ts

@@ -252,6 +252,7 @@ export class ShellExecutionService {
       onOutputEvent,
       abortSignal,
       shellExecutionConfig.sanitizationConfig,
+      shouldUseNodePty,
     );
   }
 
@@ -298,6 +299,7 @@ export class ShellExecutionService {
     onOutputEvent: (event: ShellOutputEvent) => void,
     abortSignal: AbortSignal,
     sanitizationConfig: EnvironmentSanitizationConfig,
+    isInteractive: boolean,
   ): ShellExecutionHandle {
     try {
       const isWindows = os.platform() === 'win32';
@@ -305,20 +307,56 @@ export class ShellExecutionService {
       const guardedCommand = ensurePromptvarsDisabled(commandToExecute, shell);
       const spawnArgs = [...argsPrefix, guardedCommand];
 
+      // Specifically allow GIT_CONFIG_* variables to pass through sanitization
+      // in non-interactive mode so we can safely append our overrides.
+      const gitConfigKeys = !isInteractive
+        ? Object.keys(process.env).filter((k) => k.startsWith('GIT_CONFIG_'))
+        : [];
+      const sanitizedEnv = sanitizeEnvironment(process.env, {
+        ...sanitizationConfig,
+        allowedEnvironmentVariables: [
+          ...(sanitizationConfig.allowedEnvironmentVariables || []),
+          ...gitConfigKeys,
+        ],
+      });
+
+      const env: NodeJS.ProcessEnv = {
+        ...sanitizedEnv,
+        [GEMINI_CLI_IDENTIFICATION_ENV_VAR]:
+          GEMINI_CLI_IDENTIFICATION_ENV_VAR_VALUE,
+        TERM: 'xterm-256color',
+        PAGER: 'cat',
+        GIT_PAGER: 'cat',
+      };
+
+      if (!isInteractive) {
+        const gitConfigCount = parseInt(
+          sanitizedEnv['GIT_CONFIG_COUNT'] || '0',
+          10,
+        );
+        Object.assign(env, {
+          // Disable interactive prompts and session-linked credential helpers
+          // in non-interactive mode to prevent hangs in detached process groups.
+          GIT_TERMINAL_PROMPT: '0',
+          GIT_ASKPASS: '',
+          SSH_ASKPASS: '',
+          GH_PROMPT_DISABLED: '1',
+          GCM_INTERACTIVE: 'never',
+          DISPLAY: '',
+          DBUS_SESSION_BUS_ADDRESS: '',
+          GIT_CONFIG_COUNT: (gitConfigCount + 1).toString(),
+          [`GIT_CONFIG_KEY_${gitConfigCount}`]: 'credential.helper',
+          [`GIT_CONFIG_VALUE_${gitConfigCount}`]: '',
+        });
+      }
+
       const child = cpSpawn(executable, spawnArgs, {
         cwd,
         stdio: ['ignore', 'pipe', 'pipe'],
         windowsVerbatimArguments: isWindows ? false : undefined,
         shell: false,
         detached: !isWindows,
-        env: {
-          ...sanitizeEnvironment(process.env, sanitizationConfig),
-          [GEMINI_CLI_IDENTIFICATION_ENV_VAR]:
-            GEMINI_CLI_IDENTIFICATION_ENV_VAR_VALUE,
-          TERM: 'xterm-256color',
-          PAGER: 'cat',
-          GIT_PAGER: 'cat',
-        },
+        env,
       });
 
       const state = {