[build-tools] Install ffmpeg for argent screen recording when missing

CHANGELOG.md

@@ -13,6 +13,8 @@ This is the log of notable changes to EAS CLI and related packages.
 
 ### 🐛 Bug fixes
 
+- [build-tools] Install ffmpeg when it is missing so Argent screen recording works in EAS Simulator sessions. ([#4110](https://github.com/expo/eas-cli/pull/4110) by [@szdziedzic](https://github.com/szdziedzic))
+
 ### 🧹 Chores
 
 ## [21.4.0](https://github.com/expo/eas-cli/releases/tag/v21.4.0) - 2026-07-28

packages/build-tools/src/steps/functions/__tests__/startArgentRemoteSession-orchestration.test.ts

@@ -40,6 +40,7 @@ jest.mock('../../utils/argentEvents', () => ({
   startArgentEventCollectionAsync: jest.fn(),
 }));
 jest.mock('../../utils/remoteDeviceRunSession', () => ({
+  ensureFfmpegInstalledAsync: jest.fn(),
   getDeviceRunSessionIdOrThrow: jest.fn(),
   getNgrokAuthtokenOrThrow: jest.fn(),
   getNgrokTunnelDomainOrThrow: jest.fn(),

packages/build-tools/src/steps/functions/startArgentRemoteSession.ts

@@ -20,6 +20,7 @@ import { sleepAsync } from '../../utils/retry';
 import { pollArgentArtifactsForUploadAsync } from '../utils/argentArtifacts';
 import { ARGENT_EVENT_LOG_FILENAME, startArgentEventCollectionAsync } from '../utils/argentEvents';
 import {
+  ensureFfmpegInstalledAsync,
   getDeviceRunSessionIdOrThrow,
   getNgrokAuthtokenOrThrow,
   getNgrokTunnelDomainOrThrow,
@@ -89,6 +90,12 @@ export function createStartArgentRemoteSessionBuildFunction(
         await selectXcodeDeveloperDirectoryAsync({ env, logger });
       }
 
+      // Argent shells out to ffmpeg to record the screen. Installing it pulls a
+      // large Homebrew dependency tree, so do not block session readiness on it:
+      // the session comes up at its usual speed and only a recording started in
+      // the first moments misses ffmpeg. Never rejects, so `void` is safe.
+      void ensureFfmpegInstalledAsync({ runtimePlatform, env, logger });
+
       logger.info('Enabling the Argent artifacts list endpoint flag.');
       await spawn(
         'bunx',

packages/build-tools/src/steps/utils/__tests__/remoteDeviceRunSession.test.ts

@@ -1,11 +1,14 @@
 import { bunyan } from '@expo/logger';
-import { BuildStepEnv } from '@expo/steps';
+import { BuildRuntimePlatform, BuildStepEnv } from '@expo/steps';
+import spawn from '@expo/turtle-spawn';
+import fs from 'node:fs';
 import { setTimeout as setTimeoutAsync } from 'node:timers/promises';
 
 import { CustomBuildContext } from '../../../customBuildContext';
 import { Sentry } from '../../../sentry';
 import { turtleFetch } from '../../../utils/turtleFetch';
 import {
+  ensureFfmpegInstalledAsync,
   fetchServeSimTurnArgsAsync,
   turnIceServersToServeSimArgs,
   waitForDeviceRunSessionStoppedAsync,
@@ -14,6 +17,7 @@ import {
 jest.mock('node:timers/promises');
 jest.mock('../../../utils/turtleFetch');
 jest.mock('../../../sentry');
+jest.mock('@expo/turtle-spawn');
 
 function createLoggerMock(): bunyan {
   return {
@@ -279,3 +283,135 @@ describe(waitForDeviceRunSessionStoppedAsync, () => {
     );
   });
 });
+
+describe(ensureFfmpegInstalledAsync, () => {
+  const spawnMock = jest.mocked(spawn);
+  let existsSyncSpy: jest.SpyInstance;
+
+  function spawnResolved(): ReturnType<typeof spawn> {
+    return Promise.resolve({}) as unknown as ReturnType<typeof spawn>;
+  }
+
+  function spawnRejected(): ReturnType<typeof spawn> {
+    return Promise.reject(new Error('boom')) as unknown as ReturnType<typeof spawn>;
+  }
+
+  beforeEach(() => {
+    spawnMock.mockReset();
+    jest.mocked(Sentry).capture.mockReset();
+    // Default to "no ffmpeg on any fallback path" so each test opts in.
+    existsSyncSpy = jest.spyOn(fs, 'existsSync').mockReturnValue(false);
+  });
+
+  afterEach(() => {
+    existsSyncSpy.mockRestore();
+  });
+
+  it('does not install when ffmpeg is already on a fallback path', async () => {
+    existsSyncSpy.mockImplementation(path => path === '/opt/homebrew/bin/ffmpeg');
+
+    await ensureFfmpegInstalledAsync({
+      runtimePlatform: BuildRuntimePlatform.DARWIN,
+      env: createEnvMock(),
+      logger: createLoggerMock(),
+    });
+
+    expect(spawnMock).not.toHaveBeenCalled();
+  });
+
+  it('does not install when ffmpeg is on PATH', async () => {
+    spawnMock.mockReturnValueOnce(spawnResolved());
+
+    await ensureFfmpegInstalledAsync({
+      runtimePlatform: BuildRuntimePlatform.DARWIN,
+      env: createEnvMock(),
+      logger: createLoggerMock(),
+    });
+
+    expect(spawnMock).toHaveBeenCalledTimes(1);
+    expect(spawnMock).toHaveBeenCalledWith('sh', ['-c', 'command -v ffmpeg'], expect.anything());
+  });
+
+  it('installs ffmpeg with Homebrew on darwin when it is missing', async () => {
+    spawnMock.mockReturnValueOnce(spawnRejected()).mockReturnValueOnce(spawnResolved());
+
+    await ensureFfmpegInstalledAsync({
+      runtimePlatform: BuildRuntimePlatform.DARWIN,
+      env: createEnvMock(),
+      logger: createLoggerMock(),
+    });
+
+    expect(spawnMock).toHaveBeenLastCalledWith(
+      'brew',
+      ['install', 'ffmpeg'],
+      expect.objectContaining({
+        env: expect.objectContaining({ HOMEBREW_NO_AUTO_UPDATE: '1' }),
+      })
+    );
+  });
+
+  it('installs ffmpeg with apt on linux when it is missing', async () => {
+    spawnMock
+      .mockReturnValueOnce(spawnRejected()) // command -v ffmpeg
+      .mockReturnValueOnce(spawnResolved()) // apt-get update
+      .mockReturnValueOnce(spawnResolved()); // apt-get install
+
+    await ensureFfmpegInstalledAsync({
+      runtimePlatform: BuildRuntimePlatform.LINUX,
+      env: createEnvMock(),
+      logger: createLoggerMock(),
+    });
+
+    expect(spawnMock).toHaveBeenCalledWith(
+      'sudo',
+      ['apt-get', 'update'],
+      expect.objectContaining({
+        env: expect.objectContaining({ DEBIAN_FRONTEND: 'noninteractive' }),
+      })
+    );
+    expect(spawnMock).toHaveBeenLastCalledWith(
+      'sudo',
+      ['apt-get', 'install', '-y', 'ffmpeg'],
+      expect.objectContaining({
+        env: expect.objectContaining({ DEBIAN_FRONTEND: 'noninteractive' }),
+      })
+    );
+  });
+
+  it('still installs on linux when the apt index refresh fails', async () => {
+    spawnMock
+      .mockReturnValueOnce(spawnRejected()) // command -v ffmpeg
+      .mockReturnValueOnce(spawnRejected()) // apt-get update
+      .mockReturnValueOnce(spawnResolved()); // apt-get install
+    const logger = createLoggerMock();
+
+    await ensureFfmpegInstalledAsync({
+      runtimePlatform: BuildRuntimePlatform.LINUX,
+      env: createEnvMock(),
+      logger,
+    });
+
+    expect(spawnMock).toHaveBeenLastCalledWith(
+      'sudo',
+      ['apt-get', 'install', '-y', 'ffmpeg'],
+      expect.anything()
+    );
+    expect(logger.warn).not.toHaveBeenCalled();
+  });
+
+  it('warns and resolves when the install fails, so the session still starts', async () => {
+    spawnMock.mockReturnValueOnce(spawnRejected()).mockReturnValueOnce(spawnRejected());
+    const logger = createLoggerMock();
+
+    await expect(
+      ensureFfmpegInstalledAsync({
+        runtimePlatform: BuildRuntimePlatform.DARWIN,
+        env: createEnvMock(),
+        logger,
+      })
+    ).resolves.toBeUndefined();
+
+    expect(logger.warn).toHaveBeenCalled();
+    expect(jest.mocked(Sentry).capture).toHaveBeenCalled();
+  });
+});

packages/build-tools/src/steps/utils/remoteDeviceRunSession.ts

@@ -1,6 +1,7 @@
 import { SystemError } from '@expo/eas-build-job';
 import { bunyan } from '@expo/logger';
-import { BuildStepEnv, spawnAsync } from '@expo/steps';
+import { asyncResult } from '@expo/results';
+import { BuildRuntimePlatform, BuildStepEnv, spawnAsync } from '@expo/steps';
 import spawn from '@expo/turtle-spawn';
 import * as ngrok from '@ngrok/ngrok';
 import { graphql } from 'gql.tada';
@@ -179,6 +180,96 @@ async function sleepUntilAbortedAsync(
   }
 }
 
+// Argent encodes screen recordings by piping simulator frames into `ffmpeg`,
+// which it resolves from PATH and then from these prefixes. Keep the list in
+// sync with argent so we never reinstall a binary it can already find.
+const FFMPEG_FALLBACK_PATHS = [
+  '/opt/homebrew/bin/ffmpeg',
+  '/usr/local/bin/ffmpeg',
+  '/usr/bin/ffmpeg',
+];
+
+async function isFfmpegAvailableAsync(env: BuildStepEnv): Promise<boolean> {
+  if (FFMPEG_FALLBACK_PATHS.some(ffmpegPath => fs.existsSync(ffmpegPath))) {
+    return true;
+  }
+  return (await asyncResult(spawn('sh', ['-c', 'command -v ffmpeg'], { env }))).ok;
+}
+
+async function installFfmpegWithHomebrewAsync({
+  env,
+  logger,
+}: {
+  env: BuildStepEnv;
+  logger: bunyan;
+}): Promise<void> {
+  await spawn('brew', ['install', 'ffmpeg'], {
+    env: { ...env, HOMEBREW_NO_AUTO_UPDATE: '1' },
+    logger,
+  });
+}
+
+async function installFfmpegWithAptAsync({
+  env,
+  logger,
+}: {
+  env: BuildStepEnv;
+  logger: bunyan;
+}): Promise<void> {
+  const aptEnv = { ...env, DEBIAN_FRONTEND: 'noninteractive' };
+  // The worker's package index can be older than the image it booted from, which
+  // makes the install 404 on a moved package. Refreshing first avoids that; a
+  // failed refresh is not fatal because the existing index may still resolve.
+  await asyncResult(spawn('sudo', ['apt-get', 'update'], { env: aptEnv, logger }));
+  await spawn('sudo', ['apt-get', 'install', '-y', 'ffmpeg'], { env: aptEnv, logger });
+}
+
+/**
+ * Install ffmpeg when the runtime does not already provide it, so argent's
+ * `screen-recording-start` tool can encode a video. The worker images do not
+ * ship ffmpeg yet, so without this the tool fails with "`ffmpeg` was not found
+ * on PATH" — on macOS (iOS simulators) and Linux (Android emulators) alike.
+ *
+ * Best-effort by design: screen recording is one optional argent tool, so a
+ * failure here is logged and the session continues without it. Never rejects,
+ * which is what lets the caller run it in the background.
+ */
+export async function ensureFfmpegInstalledAsync({
+  runtimePlatform,
+  env,
+  logger,
+}: {
+  runtimePlatform: BuildRuntimePlatform;
+  env: BuildStepEnv;
+  logger: bunyan;
+}): Promise<void> {
+  if (await isFfmpegAvailableAsync(env)) {
+    logger.info('ffmpeg is already installed.');
+    return;
+  }
+
+  const isDarwin = runtimePlatform === BuildRuntimePlatform.DARWIN;
+  logger.info(
+    `ffmpeg is not installed, installing it with ${
+      isDarwin ? 'Homebrew' : 'apt'
+    } for argent screen recording.`
+  );
+  const installResult = await asyncResult(
+    isDarwin
+      ? installFfmpegWithHomebrewAsync({ env, logger })
+      : installFfmpegWithAptAsync({ env, logger })
+  );
+  if (!installResult.ok) {
+    Sentry.capture('Could not install ffmpeg for argent screen recording', installResult.reason);
+    logger.warn(
+      { err: installResult.reason },
+      'Could not install ffmpeg. Argent screen recording will not work in this session.'
+    );
+    return;
+  }
+  logger.info('Installed ffmpeg.');
+}
+
 const TurnIceServersResponseSchema = z.object({
   data: z.object({
     iceServers: TurnIceServersSchema,