The permanent-brick class in #69078: xAI returns 'Invalid PNG image'
when a re-serialized image part in replayed history becomes
undecodable. The existing image-error patterns cover only Anthropic
'exceeds max dimension' wordings and 'model does not support images'
strings, so the classifier lands on a generic non-retryable 400 and
neither the shrink path nor the strip path fires. Every subsequent
turn (even bare text) fails identically because the poison stays in
history — the session is permanently wedged until deleted.
Two recovery layers, deliberately separate:
- Semantic split: new FailoverReason.image_corrupt with
_IMAGE_CORRUPT_PATTERNS ('invalid png image' / 'invalid jpeg image'),
checked BEFORE _IMAGE_TOO_LARGE_PATTERNS in both _classify_400 and
_classify_by_message. Corrupt bytes route to strip-and-retry, never
to the shrink path (shrinking corrupt bytes cannot help).
- Generic fallback: any non-retryable 400 whose outgoing messages
still contain image parts gets one strip-and-retry via the existing
_strip_images_from_messages helper, guarded by a new
stripped_images_this_turn one-shot flag on TurnRetryState. This
un-bricks the session for any current or future provider wording
without adding another pattern list to maintain.
Item 3 from the report (multimodal-part integrity across FTS
persistence + compaction handoff) is a separate investigation and
remains follow-up work.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: paultaki <paultaki@users.noreply.github.com>
Sora-bluesky
8aeb3f6ee3