{
  "slug": "screencast-start-and-screencast-stop-use-built-in-recording-by-default-8036f981d89c",
  "title": "screencast_start and screencast_stop use built-in recording by default",
  "tools": [
    "chrome-devtools-mcp"
  ],
  "tags": [
    "agent"
  ],
  "introduced_at": "2026-10-15T14:01:41.000Z",
  "announced_at": "2026-10-15T14:01:41.000Z",
  "effective_at": null,
  "date_basis": "source-publication",
  "status": "unknown",
  "how": {
    "incantation": "When recording a page without ffmpeg, call `screencast_start` and then `screencast_stop`; the built-in recorder writes MP4. To set the frame rate, configure `--screencast-fps=<positive-integer>` (the old `--experimental-screencast-fps` name remains an alias).",
    "examples": [
      "screencast_start({\"pageId\": <page-id>, \"filePath\": \"<output.mp4>\"})\nscreencast_stop({\"pageId\": <page-id>})",
      "npx chrome-devtools-mcp@1.11.0 --screencast-fps=<positive-integer>"
    ],
    "gotchas": [
      "Version: 1.11.0",
      "pageId (required): Identifies the page to record or stop recording.",
      "filePath: Optional output path; the recorder generates a unique path when omitted. Built-in recording outputs MP4.",
      "--screencast-fps: Frame rate; must be a positive integer. `--experimental-screencast-fps` is an alias.",
      "--experimental-screencast: Selects legacy ffmpeg-based screencast tools; requires ffmpeg installed and available in the MCP server PATH. Not needed for built-in recording or the frame-rate flag.",
      "Prerequisite: Install and configure chrome-devtools-mcp; the tools require a target page ID.",
      "Prerequisite: For the legacy implementation only, install ffmpeg and make it available in the MCP server PATH.",
      "The legacy ffmpeg-based implementation remains available behind `--experimental-screencast`.",
      "The new built-in recorder always writes MP4.",
      "The fps flag no longer requires `--experimental-screencast`.",
      "Docs conflict: The commit-pinned tool reference still says screencast tools require `--experimentalScreencast=true` and lists WebM as supported. This conflicts with the release note's default built-in MP4 recorder behavior; omitted those claims."
    ]
  },
  "why_it_matters": "When recording a page without an ffmpeg dependency, use the default screencast tools and set the recording frame rate if needed.",
  "before": "Use the legacy ffmpeg-based screencast implementation, which requires ffmpeg available in the MCP server PATH and `--experimental-screencast`.",
  "sources": [
    "https://github.com/ChromeDevTools/chrome-devtools-mcp/releases/tag/chrome-devtools-mcp-v1.11.0",
    "https://github.com/ChromeDevTools/chrome-devtools-mcp/pull/3123",
    "https://github.com/ChromeDevTools/chrome-devtools-mcp/blob/8953ea5159e38dfe8c6c553c02991a45fb8c5655/docs/tool-reference.md",
    "https://github.com/ChromeDevTools/chrome-devtools-mcp/blob/8953ea5159e38dfe8c6c553c02991a45fb8c5655/docs/configuration.md",
    "https://github.com/ChromeDevTools/chrome-devtools-mcp/blob/8953ea5159e38dfe8c6c553c02991a45fb8c5655/src/config/mcp-options.ts"
  ],
  "rank": 0.97035,
  "judge": {
    "publish": true,
    "judge_model": "codex-cli/gpt-6-luna+typesafe/jev-1.13.0",
    "prompt_version": "extract-v7+enrich-v2+judge-v2x3+jev-publish-v1"
  },
  "review_state": "approved",
  "provenance": {
    "run_id": "daily-20261015-20",
    "verdict_id": "daily-20261015-20:daily-20261015-20-0fad988eee015972-7:gate",
    "evidence_hash": "f4ab448bcf93bfbc244c11495c3319bca957c64c1a6b2148d3c22048468b33a0"
  },
  "review": {
    "draft_hash": "fd12b4b8d684e21ea1c5fcbbcf3a59f382f65116e76dd05b9ba9dbe661f4301b",
    "reviewer": "publication-gate",
    "reviewed_at": "2026-10-15T14:01:41.000Z",
    "decision": "daily-20261015-20:gate",
    "reason": "3 of 3 judge runs approved with p_yes >= 0.9 (mean 0.97 >= 0.9; 2 needed) and Jev gave 0.79 (>= 0.6 needed)."
  }
}