fix(recording): stream the native webcam to disk instead of losing it

[EtienneLescot]

Fixes #253.

The bug

On the macOS and Linux native capture paths the webcam handle is built with no file name, which selects in-memory buffering — nothing reaches disk during capture. Finalize then has to flatten the whole clip into a single ArrayBuffer to hand it across IPC. Past ~2 GB (roughly 20 minutes at BITRATE_BASE) that allocation throws.

The throw was swallowed twice:

1. fixWebmDuration catches its own failure and returns the unpatched blob — WebmFile.fromBlob does a full-blob FileReader.readAsArrayBuffer, so it dies first and silently.
2. The finalize catch logged to console and returned undefined, which made the if (webcamAsset && result.path) guard skip the attach entirely.

The session was written screen-only and the editor opened as if nothing had happened, camera simply absent. No toast, no failure state.

One correction to the issue's diagnosis: this is not memory exhaustion. Chromium handled the buffering correctly and spilled the ~1380 one-second blobs to blob_storage — that's what the reporter's 2149 MB disk-write warning actually shows. What has a hard ceiling is the mandatory flatten. The old design needed a contiguous multi-GB allocation four times over: the FileReader read, .arrayBuffer(), the structured clone through ipcRenderer.invoke, and Buffer.from() in the main process.

Windows is unaffected — its helper owns webcam capture directly.

The fix

Pass the webcam file name on both native paths so chunks stream to disk as they arrive, the way the legacy path and the Windows helper already do. All the plumbing existed (RecordingStreamRegistry, finalizeRecordingFile, repairRecordingContainer) — the native paths just weren't wired to it.

• Finalize branches on isStreaming(): a streamed clip hands over its name alone; the main process closes the stream and patches the WebM duration on disk. Nothing multi-gigabyte is flattened or crosses IPC. Buffered short takes keep the existing behaviour.
• Every failure now reaches the user as a toast, with a reason. Both the catch and the size === 0 early return used to exit without saying anything.
• Partial files are cleaned up. Now that bytes land on disk during capture, a webcam stream not folded into a saved session gets closed and its file removed, or a discarded/failed take orphans a half-written .webm.
• The macOS and Linux finalizers were line-for-line copies, so the shared logic moved into finalizeWebcamAsset() instead of being duplicated a second time.

Tests

Six new cases in src/hooks/webcamAsset.test.ts, following the webcamOffset.test.ts convention. Verified they have teeth: removing the isStreaming() branch fails two of them.

Full suite: 1625 passing. The 6 failures in electron/recording/webm-seek-index.test.ts are pre-existing and unrelated — that suite asserts remux behaviour behind a process.platform !== "linux" guard, so it only passes on Linux (confirmed failing identically on a clean tree).

What I could not verify

The streaming path is exercised by unit tests, not by a real >2 GB recording — I have no way to run a 20-minute webcam capture here. Worth one manual long take on macOS before release.

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[lorenjphillips]

thank you!