Video capture

Cairntrace records native WebM video with the Playwright backend. The agent-browser and mock backends do not record video, and Cairntrace does not build a synthetic video from screenshots.

Record a Playwright run

Enable video in the spec and run it with Playwright:

artifacts:
  capture:
    video: always
  video:
    slowMo: 250
    speed: 1

cairn run flows/checkout.yml --backend playwright

A retained recording is written to videos/playwright-video.webm. slowMo delays browser actions so short interactions remain visible. speed changes playback speed during post-processing and requires ffmpeg.

Capture policy controls retention:

• always keeps video for passing and non-passing runs.
• on-failure removes the video after a passing run.
• never disables recording and is the default.

Check Playwright readiness

Install the package dependencies and the matching Chromium build:

bun install
bunx playwright install chromium
cairn doctor --format md

Doctor reports playwright-package and playwright-chromium separately. This distinguishes a missing dependency install from a missing or non-executable browser binary.

Use screenshots on agent-browser

When you use agent-browser, capture screenshots directly:

artifacts:
  capture:
    screenshots: always
    video: never

Screenshots are written as screenshots/<step-ordinal>_<step-id>.png. If video is requested on a backend without recording support, Cairntrace writes a warning to events.ndjson and continues the run without a video file.

Audit and clips

cairn audit forces the Playwright backend and video capture, then can run vidtrace extraction under videos/vidtrace/. cairn clip cuts labelled segments from an existing retained video; it cannot create a source video for a run that did not record one.

See also

• Artifacts — exact run-directory layout and redaction boundary
• Clip — cut labelled segments with vidtrace
• Investigate and audit — one-command video evidence and code connection
• Doctor and clean — Playwright package and Chromium readiness checks