opfs-worker ignores the byte count FileSystemSyncAccessHandle.write() returns, so a short write corrupts the file silently #138

Severity: low

Where: chrome/player/network/opfs-worker.mjs (setFile, saveAppend, the heartbeat write)

What happens

accessHandle.write(data, {at: 0});
...
stream.handle.write(data, {at: stream.offset});
stream.offset += data.byteLength;

FileSystemSyncAccessHandle.write() returns the number of bytes written. Nothing compares it with data.byteLength.

Failure scenario

A partial write (disk nearly full) leaves a hole; the next saveAppend lands at the assumed offset and the saved MP4 is corrupt with no error.

Suggested fix

const n = handle.write(...); if (n !== data.byteLength) throw new Error(...) in all three places.

Confidence: medium (depends on Gecko returning a short count rather than throwing).

From a line-by-line code review of the tree at 41363fd (2026-10-02). Each claim above was checked against the source before filing; the reproduction steps and line references are as of that commit.

Generated by Claude Code