feat(cli): Antigravity run mode

Adds Antigravity as a sixth CLI backend alongside Claude Code, shell, OpenCode,
Codex and Gemini, following the existing pluggable-resolver pattern.

- `utils/antigravity-cli-resolver.ts` resolves the CLI, mirroring the other
  resolvers; `GET /api/antigravity/status` reports availability and path.
- `ANTIGRAVITY_*` joins the `ALLOWED_ENV_PREFIXES` allowlist in schemas.ts, so
  env overrides stay CLI-scoped rather than blanket-forwarded.
- Session, tmux-manager, mux-interface and types carry the new mode; secrets are
  injected via socket-scoped `tmux setenv`, never on the spawn command line, so
  the mode requires tmux with no direct PTY fallback like the other external CLIs.
- Frontend: Run-dropdown entry, agent-type option, `ag` tab badge and toolbar
  colours. `runAntigravity()` routes remote/docker cases through
  `POST /api/quick-start` and skips the local status probe for them.

Tests: test/antigravity-mode.test.ts, plus run-mode-ui and system-routes coverage.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

test/antigravity-mode.test.ts

@@ -0,0 +1,123 @@
+import { describe, expect, it } from 'vitest';
+import { CreateSessionSchema, QuickStartSchema } from '../src/web/schemas.js';
+import { buildSpawnCommand } from '../src/tmux-manager.js';
+import { defaultDockerCommandForMode } from '../src/docker-hosts.js';
+import { defaultRemoteCommandForMode } from '../src/remote-hosts.js';
+import { isExternalCliMode, isAltScreenStripMode } from '../src/session.js';
+
+describe('Antigravity mode schemas', () => {
+  it('accepts Antigravity session creation config', () => {
+    const parsed = CreateSessionSchema.parse({
+      workingDir: '/tmp',
+      mode: 'antigravity',
+      antigravityConfig: {
+        model: 'gemini-3-pro',
+        dangerouslySkipPermissions: true,
+      },
+    });
+
+    expect(parsed.mode).toBe('antigravity');
+    expect(parsed.antigravityConfig).toEqual({
+      model: 'gemini-3-pro',
+      dangerouslySkipPermissions: true,
+    });
+  });
+
+  it('accepts Antigravity quick-start config', () => {
+    const parsed = QuickStartSchema.parse({
+      caseName: 'antigravity-case',
+      mode: 'antigravity',
+      antigravityConfig: {
+        resumeConversationId: 'conv-1234abcd',
+      },
+    });
+
+    expect(parsed.mode).toBe('antigravity');
+    expect(parsed.antigravityConfig?.resumeConversationId).toBe('conv-1234abcd');
+  });
+
+  it('rejects unsafe Antigravity model strings', () => {
+    expect(() =>
+      CreateSessionSchema.parse({
+        workingDir: '/tmp',
+        mode: 'antigravity',
+        antigravityConfig: { model: 'agy; rm -rf /' },
+      })
+    ).toThrow();
+  });
+
+  it('allows ANTIGRAVITY_* env overrides and still rejects unknown prefixes', () => {
+    const parsed = CreateSessionSchema.parse({
+      workingDir: '/tmp',
+      mode: 'antigravity',
+      envOverrides: { ANTIGRAVITY_LOG_LEVEL: 'debug' },
+    });
+    expect(parsed.envOverrides).toEqual({ ANTIGRAVITY_LOG_LEVEL: 'debug' });
+
+    expect(() =>
+      CreateSessionSchema.parse({
+        workingDir: '/tmp',
+        envOverrides: { RANDOM_PREFIX_KEY: 'x' },
+      })
+    ).toThrow();
+  });
+});
+
+describe('Antigravity spawn command', () => {
+  it('builds a bare agy command when no config is sent (safe default, no bypass)', () => {
+    const cmd = buildSpawnCommand({ mode: 'antigravity', sessionId: 'abc12345' });
+    expect(cmd).toBe('agy');
+  });
+
+  it('adds --dangerously-skip-permissions only when explicitly requested', () => {
+    const cmd = buildSpawnCommand({
+      mode: 'antigravity',
+      sessionId: 'abc12345',
+      antigravityConfig: { dangerouslySkipPermissions: true, model: 'gemini-3-pro' },
+    });
+    expect(cmd).toBe('agy --dangerously-skip-permissions --model gemini-3-pro');
+  });
+
+  it('passes --conversation for resume and drops unsafe ids', () => {
+    expect(
+      buildSpawnCommand({
+        mode: 'antigravity',
+        sessionId: 'abc12345',
+        antigravityConfig: { resumeConversationId: 'conv-99' },
+      })
+    ).toBe('agy --conversation conv-99');
+
+    expect(
+      buildSpawnCommand({
+        mode: 'antigravity',
+        sessionId: 'abc12345',
+        antigravityConfig: { resumeConversationId: 'x; rm -rf /' },
+      })
+    ).toBe('agy');
+  });
+
+  it('drops unsafe model strings from the spawn command', () => {
+    expect(
+      buildSpawnCommand({
+        mode: 'antigravity',
+        sessionId: 'abc12345',
+        antigravityConfig: { model: 'a`b' },
+      })
+    ).toBe('agy');
+  });
+});
+
+describe('Antigravity mode gates', () => {
+  it('is an external CLI mode (readiness/ralph/respawn gating)', () => {
+    expect(isExternalCliMode('antigravity')).toBe(true);
+  });
+
+  it('is NOT an alt-screen strip mode (unverified Go TUI, like opencode)', () => {
+    expect(isAltScreenStripMode('antigravity')).toBe(false);
+  });
+
+  it('has docker/remote default commands', () => {
+    expect(defaultDockerCommandForMode('antigravity')).toBe('exec agy');
+    expect(defaultRemoteCommandForMode('antigravity')).toBe('exec agy');
+  });
+});

test/routes/system-routes.test.ts

@@ -81,12 +81,18 @@ vi.mock('../../src/utils/gemini-cli-resolver.js', () => ({
   resolveGeminiDir: vi.fn(() => null),
 }));
 
+vi.mock('../../src/utils/antigravity-cli-resolver.js', () => ({
+  isAntigravityAvailable: vi.fn(() => false),
+  resolveAntigravityDir: vi.fn(() => null),
+}));
+
 import fs from 'node:fs/promises';
 import { existsSync, readdirSync } from 'node:fs';
 import { subagentWatcher } from '../../src/subagent-watcher.js';
 import { getLifecycleLog } from '../../src/session-lifecycle-log.js';
 import { isOpenCodeAvailable, resolveOpenCodeDir } from '../../src/utils/opencode-cli-resolver.js';
 import { isGeminiAvailable, resolveGeminiDir } from '../../src/utils/gemini-cli-resolver.js';
+import { isAntigravityAvailable, resolveAntigravityDir } from '../../src/utils/antigravity-cli-resolver.js';
 
 const mockedReadFile = vi.mocked(fs.readFile);
 const mockedWriteFile = vi.mocked(fs.writeFile);
@@ -98,6 +104,8 @@ const mockedIsOpenCodeAvailable = vi.mocked(isOpenCodeAvailable);
 const mockedResolveOpenCodeDir = vi.mocked(resolveOpenCodeDir);
 const mockedIsGeminiAvailable = vi.mocked(isGeminiAvailable);
 const mockedResolveGeminiDir = vi.mocked(resolveGeminiDir);
+const mockedIsAntigravityAvailable = vi.mocked(isAntigravityAvailable);
+const mockedResolveAntigravityDir = vi.mocked(resolveAntigravityDir);
 
 describe('system-routes', () => {
   let harness: RouteTestHarness;
@@ -805,6 +813,32 @@ describe('system-routes', () => {
     });
   });
 
+  // ========== GET /api/antigravity/status ==========
+
+  describe('GET /api/antigravity/status', () => {
+    it('returns unavailable when agy is not installed', async () => {
+      mockedIsAntigravityAvailable.mockReturnValue(false);
+      mockedResolveAntigravityDir.mockReturnValue(null);
+
+      const res = await harness.app.inject({ method: 'GET', url: '/api/antigravity/status' });
+      expect(res.statusCode).toBe(200);
+      const body = JSON.parse(res.body);
+      expect(body.available).toBe(false);
+      expect(body.path).toBeNull();
+    });
+
+    it('returns available with path when agy is installed', async () => {
+      mockedIsAntigravityAvailable.mockReturnValue(true);
+      mockedResolveAntigravityDir.mockReturnValue('/home/user/.local/bin');
+
+      const res = await harness.app.inject({ method: 'GET', url: '/api/antigravity/status' });
+      expect(res.statusCode).toBe(200);
+      const body = JSON.parse(res.body);
+      expect(body.available).toBe(true);
+      expect(body.path).toBe('/home/user/.local/bin');
+    });
+  });
+
   // ========== GET /api/execution/model-config ==========
 
   describe('GET /api/execution/model-config', () => {

test/run-mode-ui.test.ts

@@ -71,6 +71,16 @@ describe('run mode UI', () => {
     expect(app.runMode).toBe('gemini');
     expect(runBtnLabel.textContent).toBe('Run GM');
   });
+
+  it('accepts Antigravity mode from server sync and updates the run button label', async () => {
+    const { app, storage, runBtnLabel } = loadRunModeHarness();
+
+    storage.set('codeman_runMode', 'claude');
+    await app.loadAppSettingsFromServer(Promise.resolve({ runMode: 'antigravity' }));
+
+    expect(app.runMode).toBe('antigravity');
+    expect(runBtnLabel.textContent).toBe('Run AG');
+  });
 });
 
 describe('Run launch synchronization', () => {
@@ -557,3 +567,56 @@ describe('Gemini quick start', () => {
     expect(selected).toEqual(['sess-gm']);
   });
 });
+
+describe('Antigravity quick start', () => {
+  // Same envelope-unwrap regression guard as the Gemini block above, for runAntigravity().
+  it('drives runAntigravity() through the {success,data} envelope and selects the new session', async () => {
+    const elements: Record<string, any> = {
+      quickStartCase: { value: 'ag-case' },
+    };
+    const requests: Array<{ url: string; body?: any }> = [];
+    const CodemanApp = function CodemanApp(this: any) {};
+
+    const context = vm.createContext({
+      CodemanApp,
+      localStorage: { getItem: () => null, setItem: () => {} },
+      document: { getElementById: (id: string) => elements[id] ?? null },
+      fetch: async (url: string, init?: { body?: string }) => {
+        requests.push({ url, body: init?.body ? JSON.parse(init.body) : undefined });
+        if (url === '/api/antigravity/status')
+          return { json: async () => ({ success: true, data: { available: true } }) };
+        if (url === '/api/quick-start')
+          return { json: async () => ({ success: true, data: { sessionId: 'sess-ag' } }) };
+        if (url === '/api/sessions/sess-ag')
+          return { json: async () => ({ success: true, data: { id: 'sess-ag', name: 'w1-ag-case' } }) };
+        throw new Error(`unexpected fetch: ${url}`);
+      },
+      console,
+    });
+
+    const sessionUi = readFileSync(resolve(import.meta.dirname, '../src/web/public/session-ui.js'), 'utf8');
+    vm.runInContext(sessionUi, context, { filename: 'session-ui.js' });
+
+    const app = new (CodemanApp as any)();
+    app.terminal = { clear: () => {}, writeln: () => {}, focus: () => {} };
+    app.loadAppSettingsFromStorage = () => ({});
+    app.getCaseSettings = () => ({});
+    app.buildEnvOverrides = () => ({});
+    app.sessions = new Map();
+    app._onSessionCreated = (session: any) => app.sessions.set(session.id, session);
+    app._renderSessionTabsImmediate = vi.fn();
+    const selected: string[] = [];
+    app.selectSession = async (id: string) => {
+      selected.push(id);
+    };
+
+    await app.runAntigravity();
+
+    expect(requests.find((req) => req.url === '/api/quick-start')?.body).toMatchObject({
+      caseName: 'ag-case',
+      mode: 'antigravity',
+      antigravityConfig: { dangerouslySkipPermissions: true },
+    });
+    expect(selected).toEqual(['sess-ag']);
+  });
+});