video-start/video-stop produces 0-byte files when navigations occur during recording

[kenwang-coursera]

Version

• @playwright/cli: 0.1.1
• bundled playwright: 1.59.0-alpha-1771104257000
• Node: v20.12.2
• OS: macOS 26.3.1 (Darwin arm64)

Repro

playwright-cli open
playwright-cli goto https://news.ycombinator.com
playwright-cli video-start
playwright-cli goto https://news.ycombinator.com/newest
playwright-cli snapshot
playwright-cli goto https://news.ycombinator.com/ask
playwright-cli snapshot
playwright-cli goto https://news.ycombinator.com/show
playwright-cli snapshot
playwright-cli goto https://news.ycombinator.com
playwright-cli snapshot
playwright-cli video-stop --filename=output.webm
ls -lh output.webm
# => output.webm is 0 bytes

Expected

output.webm contains a valid video recording of the browser session.

Actual

output.webm is 0 bytes (empty file).

Reproduction Rate

5/5 — tested with 5 independent parallel sessions (-s=repro1 through -s=repro5), all produced 0-byte files.

Additional Observations

• Works with a single navigation: video-start → one goto → video-stop produces a valid video
• Not site-specific: reproduces with any website (tested with Hacker News, Coursera, example.com)
• Adding sleep before video-stop does NOT help: even sleep 10 before stop still produces 0 bytes after multiple navigations
• Headless and headed both affected
• Chrome (system) and Chromium (bundled) both affected
• Closing and reopening the browser resets the issue: after close + open, the first video cycle works again
• Progressive degradation on static pages: with repeated video-start/video-stop cycles on a static page (no navigations between), video file sizes degrade progressively (25K → 14K → 1.9K) before stabilizing at 1.9K (white fallback frame only)

Secondary Issue: --filename flag

Separately, video-stop defines filename as an --option but documentation and intuitive usage suggest it should be a positional arg:

# Fails: "error: too many arguments: expected 0, received 1"
playwright-cli video-stop output.webm

# Works
playwright-cli video-stop --filename=output.webm

Possible Root Cause (AI-assisted — may not be accurate)

The following analysis was performed by Claude (AI) by reading the source code. It has not been verified by the maintainers and may be incorrect:

• video-start calls Page.startScreencast via CDP, and sets up a ScreencastFrame event listener that feeds frames to an ffmpeg process via stdin
• Multiple rapid navigations appear to cause Chrome to stop emitting Page.screencastFrame CDP events entirely — the screencast becomes permanently dead for that browser instance
• When video-stop is called with 0 frames received, VideoRecorder.stop() creates a white fallback frame and writes it to ffmpeg. However, the output file ends up 0 bytes — possibly because saveAs() copies the file before ffmpeg has fully flushed/closed the output
• The startScreencast method in screencast.js only sends the CDP Page.startScreencast command once (when the first client registers) and does not re-issue it after navigations, which may be why Chrome stops delivering frames

[pavelfeldman]

Hm, it works for me just fine