Multipart upload (field file, max 25 MB). Returned URLs are signed and expire — attach them to a message promptly and never persist them. Idempotency-Key is not supported on multipart uploads (re-uploading is safe: every upload mints a fresh URL).
Bearer <token>.Stored
Missing, invalid or revoked service account token.
The addressed resource does not exist in this project.
File exceeds the 25 MB limit.
Idempotency-Key reuse with a different request body.
Rate limit exceeded — honor the Retry-After header.
Any other error, including validation_failed (400) and internal_error (500).