[gwdp]

Why

Follow-up to #4577. That PR made the Appium step wait for the ffmpeg setup before Appium starts, so iOS recording works on images without ffmpeg. Images that already ship ffmpeg should not pay for that setup.

The setup checks for ffmpeg by running ffmpeg -version and waits for it. On macos-tahoe-26.6-xcode-27.1, which ships Homebrew ffmpeg-full, the first run on a fresh VM took 12.8 s in one probe and 23.7 s in another while the binary loads its 83 libraries. Later runs take 0.06 s. The Android session host waits for the same check.

How

• Find ffmpeg on the step's PATH without running it: the first entry that is an executable file. An empty entry means the current directory, as it does for spawn. Device-session tools, such as XCUITest's screen recording, resolve ffmpeg the same way.
• When ffmpeg is on PATH, or after an install, run ffmpeg -version once in the background and do not wait for it. The binary then loads while Appium installs, so the first recording does not pay the cold start. A failed warm-up is ignored.

LLM Authorship

• Gabe asked to remove the cold ffmpeg -version from the session setup on the Xcode 27.1 image, and chose the PATH lookup with a background warm-up. Claude Code wrote the change.
• AI review found that empty PATH entries were skipped. They now resolve to the current directory, and a test covers it.
• A second AI review noted that an executable ffmpeg that cannot start passes the lookup. This is a known tradeoff, explained in the review thread.
• Gabe reviewed the final diff and can answer questions.

Test Plan

• EAS workflow on macos-tahoe-26.6-xcode-27.1: the first ffmpeg -version took 12.76 s, and the next two took 0.06 s and 0.07 s.

• EAS workflow on the same image: a background ffmpeg -version started with the Appium install took 23.7 s and finished before the Appium install did (36.1 s).

• build-tools unit tests in src/steps: 1337 passed. The ffmpeg tests build PATH in Jest's in-memory file system. They cover an executable on PATH, a file that is not executable, a directory named ffmpeg, an empty PATH entry, the Homebrew and apt installs, and warm-ups that reject or throw.

• The same lookup on a real macOS file system found /opt/homebrew/bin/ffmpeg, which is a relative symlink into the Homebrew Cellar. The in-memory file system cannot test symlinks, because it checks the link's own mode.

• yarn build, tsc, oxlint, and oxfmt are clean.

• EAS workflow on the session runner classes: this branch's built build-tools ran next to the deployed worker's dist, and called ensureFfmpegInstalledOnceAsync. The control ran the deployed version.

  Image	Setup returned	Warm-up done	Next ffmpeg -version
  macos-tahoe-26.6-xcode-27.1, deployed (control)	12.77 s	–	0.05 s
  macos-tahoe-26.6-xcode-27.1, this branch	0.16 s	12.01 s	0.06 s
  macos-tahoe-26.5-xcode-26.6, this branch (Homebrew install)	8.30 s	10.34 s	0.03 s
  ubuntu-26.04-jdk-17-ndk-r27b-sdk-58, this branch	0.27 s	0.68 s	0.05 s

• Not run: a hosted session with this branch deployed.

Generated with T3 Code, using Claude Code.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.92%. Comparing base (800a0e0) to head (0e2fdfb).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4582      +/-   ##
==========================================
+ Coverage   73.92%   73.92%   +0.01%     
==========================================
  Files        1012     1012              
  Lines       49330    49346      +16     
  Branches    10650    10656       +6     
==========================================
+ Hits        36460    36476      +16     
  Misses      11878    11878              
  Partials      992      992              

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[devin-ai-integration]

Devin Review found 1 potential issue.

[szdziedzic]

awesome

[github-actions]

✅ Thank you for adding the changelog entry!