Production was returning HTTP 413 with empty body on the first APPEND
segment of every video upload to X v2 — surfacing to users as 'An
unknown X error occurred.'
Empty-body 413 is the classic signature of an edge/CDN rejection: the
X gateway is denying the request before X's application code sees it.
The X v2 reference docs say 'max chunk size: 5MB', but every canonical
reference uses 1MB:
- X's official Python quickstart: `chunk_size = 1024 * 1024`
- X's official JavaScript quickstart: `const chunkSize = 1024 * 1024`
- twitter-api-v2 (the most-used Node SDK, used by Postiz et al.):
`chunkSize: number = 1024 * 1024`
5MB plus multipart-form overhead apparently exceeds an undocumented
edge limit. 1MB is the empirically safe size everyone converges on.
Changes:
- XPublisher chunked APPEND now uses 1MB chunks. An 8MB video uploads
as 8 segments instead of 2; more roundtrips but actually succeeds.
- Set explicit Content-Type on each chunk attach (matches the simple
upload path in the same file).
- XPublishException::fromApiResponse maps HTTP 413 to
ErrorCategory::MediaFormat with the message 'Media chunk rejected
by X (payload too large).' so we don't surface 413 as 'unknown' if
it ever recurs.
Test: unit test covering the 413→MediaFormat mapping. Full suite green
(1503 passed, 2 skipped).
7d82cc3f12