Fixes#2206
### Problem
`screencast_start` matched the requested file extension with a
**case-sensitive** `endsWith()` against `['.webm', '.mp4']` and
**silently fell back to `.mp4`** when nothing matched. Combined with
`ensureExtension()` (which replaces the extension), a request for
`demo.WEBM` was recorded as **MP4** to **`demo.mp4`** — a different
format *and* path than requested — and any unsupported extension (e.g.
`recording.avi`) silently became `.mp4`.
Separately, when `screencast_start` is called without a `filePath`, it
creates a temp directory via `mkdtemp()`. If `page.screencast()` then
throws (e.g. ffmpeg missing), that directory was leaked.
### Changes
Two commits:
1. **`fix: match screencast extension case-insensitively and reject
unsupported ones`** — match via `path.extname().toLowerCase()`; reject
an explicitly requested but unsupported extension with an explicit error
listing the supported formats; a missing extension still defaults to
`.mp4`.
2. **`fix: clean up screencast temp directory when recording fails to
start`** — remove the generated temp dir in the `catch` handler, but
only when we own the generated path (never when the caller supplied
`filePath`).
| requested | before | after |
| --------------- | --------------- | -------------- |
| `demo.WEBM` | mp4 → `demo.mp4`| webm → `demo.webm` |
| `recording.avi` | mp4 → `recording.mp4` | error (rejected) |
| `demo.webm` | webm → `demo.webm` | unchanged |
| *(no filePath)* | mp4 temp | unchanged |
The matched extension is normalized to lower case (`demo.WEBM` →
`demo.webm`).
### Testing
Added three regression tests to `tests/tools/screencast.test.ts` using
the existing `sinon`/`withMcpContext` harness. Verified locally against
Chrome for Testing 149 (`PUPPETEER_EXECUTABLE_PATH`):
- With the fix reverted, the two extension tests fail (uppercase `.WEBM`
→ mp4, `.avi` not rejected) and the cleanup test fails (temp dir left
behind) — i.e. they fail for the right reason.
- With the fix applied, the full `screencast.test.ts` suite passes
(11/11).
- `tsc --noEmit` and `npm run check-format` (eslint + prettier) are
clean.
> Note: I ran the `screencast` test file (which stubs `page.screencast`)
plus typecheck/lint locally; the rest of the browser-based suite I left
to CI.
### Notes for reviewers
- I chose to **`throw`** for an unsupported explicit extension
(consistent with the ffmpeg-missing `throw` in the same handler and with
the issue's "reject with an explicit error"). Happy to switch to the
softer `appendResponseLine(...) + return` style used by the in-progress
guard if you'd prefer.
- The two commits are independent and can be split if you'd rather take
them separately.
- I left the pre-existing `as \`${string}.webm\`` assertion on
`resolvedPath` untouched to keep the diff focused, though it's slightly
misleading now that the default is `.mp4`.
---------
Co-authored-by: Nicholas Roscino <nroscino@google.com>
## Summary
`screencast_stop` returns an empty response when no recording is active,
making it impossible for the calling agent to distinguish "stopped
successfully" from "nothing was recording."
`screencast_start` already handles its inverse case with an explicit
error (`"a screencast recording is already in progress"`), so this makes
`stop` consistent.
## Change
Added an error message when `screencast_stop` is called without an
active recording:
```ts
if (!data) {
response.appendResponseLine(
'Error: no active screencast recording to stop.',
);
return;
}
```
## Before
Empty tool response — agent cannot tell what happened.
## After
`Error: no active screencast recording to stop.`
---------
Co-authored-by: Nicholas Roscino <nroscino@google.com>
- renamed getSelectedPage to getSelectedPptrPage
- removes getSelectedPptrPage from tool interfaces
- moves dialog handling to McpPage
- makes responses to be optionally McpPage-scoped
## Summary
Adds `screencast_start` and `screencast_stop` MCP tools that allow
agents to record a video of a page using Puppeteer's `page.screencast()`
API.
Only enabled if the command line option `--experimental-screencast` is
provided
Closes#878.
## New Tools
### `screencast_start`
Starts recording a screencast (video) of the selected page in mp4
format.
| Parameter | Type | Default | Description |
|-----------|------|---------|-------------|
| `path` | string (optional) | temp file | Output file path |
### `screencast_stop`
Stops the active recording and reports the saved file path.
## Design
- **Start/stop pair** following the `performance_start_trace` /
`performance_stop_trace` pattern
- **State management** via `getScreenRecorder()` / `setScreenRecorder()`
on the Context interface
- **Category**: `DEBUGGING` (alongside `take_screenshot`)
- **ffmpeg dependency**: Clear error message when ffmpeg is not
installed
- **Temp file fallback**: When no `path` is provided, creates a temp
file with the correct extension
---------
Co-authored-by: Alex Rudenko <alexrudenko@chromium.org>
Nebrass Lamouchi