3 files changed, 145 insertions, 0 deletions
diff --git a/packages/cli/src/config/config.test.ts b/packages/cli/src/config/config.test.ts
index 08a85e4d..ad8b1d44 100644
--- a/packages/cli/src/config/config.test.ts
+++ b/packages/cli/src/config/config.test.ts
@@ -768,3 +768,117 @@ describe('loadCliConfig extensions', () => {
     expect(config.getExtensionContextFilePaths()).toEqual(['/path/to/ext1.md']);
   });
 });
+
+describe('loadCliConfig ideMode', () => {
+  const originalArgv = process.argv;
+  const originalEnv = { ...process.env };
+
+  beforeEach(() => {
+    vi.resetAllMocks();
+    vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
+    process.env.GEMINI_API_KEY = 'test-api-key';
+    // Explicitly delete TERM_PROGRAM and SANDBOX before each test
+    delete process.env.TERM_PROGRAM;
+    delete process.env.SANDBOX;
+  });
+
+  afterEach(() => {
+    process.argv = originalArgv;
+    process.env = originalEnv;
+    vi.restoreAllMocks();
+  });
+
+  it('should be false by default', async () => {
+    process.argv = ['node', 'script.js'];
+    const settings: Settings = {};
+    const argv = await parseArguments();
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(false);
+  });
+
+  it('should be false if --ide-mode is true but TERM_PROGRAM is not vscode', async () => {
+    process.argv = ['node', 'script.js', '--ide-mode'];
+    const settings: Settings = {};
+    const argv = await parseArguments();
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(false);
+  });
+
+  it('should be false if settings.ideMode is true but TERM_PROGRAM is not vscode', async () => {
+    process.argv = ['node', 'script.js'];
+    const argv = await parseArguments();
+    const settings: Settings = { ideMode: true };
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(false);
+  });
+
+  it('should be true when --ide-mode is set and TERM_PROGRAM is vscode', async () => {
+    process.argv = ['node', 'script.js', '--ide-mode'];
+    const argv = await parseArguments();
+    process.env.TERM_PROGRAM = 'vscode';
+    const settings: Settings = {};
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(true);
+  });
+
+  it('should be true when settings.ideMode is true and TERM_PROGRAM is vscode', async () => {
+    process.argv = ['node', 'script.js'];
+    const argv = await parseArguments();
+    process.env.TERM_PROGRAM = 'vscode';
+    const settings: Settings = { ideMode: true };
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(true);
+  });
+
+  it('should prioritize --ide-mode (true) over settings (false) when TERM_PROGRAM is vscode', async () => {
+    process.argv = ['node', 'script.js', '--ide-mode'];
+    const argv = await parseArguments();
+    process.env.TERM_PROGRAM = 'vscode';
+    const settings: Settings = { ideMode: false };
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(true);
+  });
+
+  it('should prioritize --no-ide-mode (false) over settings (true) even when TERM_PROGRAM is vscode', async () => {
+    process.argv = ['node', 'script.js', '--no-ide-mode'];
+    const argv = await parseArguments();
+    process.env.TERM_PROGRAM = 'vscode';
+    const settings: Settings = { ideMode: true };
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(false);
+  });
+
+  it('should be false when --ide-mode is true, TERM_PROGRAM is vscode, but SANDBOX is set', async () => {
+    process.argv = ['node', 'script.js', '--ide-mode'];
+    const argv = await parseArguments();
+    process.env.TERM_PROGRAM = 'vscode';
+    process.env.SANDBOX = 'true';
+    const settings: Settings = {};
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(false);
+  });
+
+  it('should be false when settings.ideMode is true, TERM_PROGRAM is vscode, but SANDBOX is set', async () => {
+    process.argv = ['node', 'script.js'];
+    const argv = await parseArguments();
+    process.env.TERM_PROGRAM = 'vscode';
+    process.env.SANDBOX = 'true';
+    const settings: Settings = { ideMode: true };
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(false);
+  });
+
+  it('should add __ide_server when ideMode is true', async () => {
+    process.argv = ['node', 'script.js', '--ide-mode'];
+    const argv = await parseArguments();
+    process.env.TERM_PROGRAM = 'vscode';
+    const settings: Settings = {};
+    const config = await loadCliConfig(settings, [], 'test-session', argv);
+    expect(config.getIdeMode()).toBe(true);
+    const mcpServers = config.getMcpServers();
+    expect(mcpServers['_ide_server']).toBeDefined();
+    expect(mcpServers['_ide_server'].httpUrl).toBe('http://localhost:3000/mcp');
+    expect(mcpServers['_ide_server'].description).toBe('IDE connection');
+    expect(mcpServers['_ide_server'].trust).toBe(false);
+  });
+});
diff --git a/packages/cli/src/config/config.ts b/packages/cli/src/config/config.ts
index 1c1f0746..626f23e1 100644
--- a/packages/cli/src/config/config.ts
+++ b/packages/cli/src/config/config.ts
@@ -17,6 +17,7 @@ import {
   DEFAULT_GEMINI_EMBEDDING_MODEL,
   FileDiscoveryService,
   TelemetryTarget,
+  MCPServerConfig,
 } from '@google/gemini-cli-core';
 import { Settings } from './settings.js';
 
@@ -54,6 +55,7 @@ export interface CliArgs {
   allowedMcpServerNames: string[] | undefined;
   extensions: string[] | undefined;
   listExtensions: boolean | undefined;
+  ideMode: boolean | undefined;
 }
 
 export async function parseArguments(): Promise<CliArgs> {
@@ -175,6 +177,10 @@ export async function parseArguments(): Promise<CliArgs> {
       type: 'boolean',
       description: 'List all available extensions and exit.',
     })
+    .option('ide-mode', {
+      type: 'boolean',
+      description: 'Run in IDE mode?',
+    })
 
     .version(await getCliVersion()) // This will enable the --version flag based on package.json
     .alias('v', 'version')
@@ -230,6 +236,11 @@ export async function loadCliConfig(
       (v) => v === 'true' || v === '1',
     );
 
+  const ideMode =
+    (argv.ideMode ?? settings.ideMode ?? false) &&
+    process.env.TERM_PROGRAM === 'vscode' &&
+    !process.env.SANDBOX;
+
   const activeExtensions = filterActiveExtensions(
     extensions,
     argv.extensions || [],
@@ -273,6 +284,24 @@ export async function loadCliConfig(
     }
   }
 
+  if (ideMode) {
+    mcpServers['_ide_server'] = new MCPServerConfig(
+      undefined, // command
+      undefined, // args
+      undefined, // env
+      undefined, // cwd
+      undefined, // url
+      'http://localhost:3000/mcp', // httpUrl
+      undefined, // headers
+      undefined, // tcp
+      undefined, // timeout
+      false, // trust
+      'IDE connection', // description
+      undefined, // includeTools
+      undefined, // excludeTools
+    );
+  }
+
   const sandboxConfig = await loadSandboxConfig(settings, argv);
 
   return new Config({
@@ -333,6 +362,7 @@ export async function loadCliConfig(
       version: e.config.version,
     })),
     noBrowser: !!process.env.NO_BROWSER,
+    ideMode,
   });
 }
 
diff --git a/packages/cli/src/config/settings.ts b/packages/cli/src/config/settings.ts
index d9e6e4c4..50c07cf1 100644
--- a/packages/cli/src/config/settings.ts
+++ b/packages/cli/src/config/settings.ts
@@ -85,6 +85,7 @@ export interface Settings {
   maxSessionTurns?: number;
 
   // Add other settings here.
+  ideMode?: boolean;
 }
 
 export interface SettingsError {