Worker published only Redis pub/sub events; backend status stayed QUEUED
forever (callback endpoint never called — gap masked by earlier Gemini 429).
- worker.py: POST /api/internal/render/callback (X-Worker-Token) after each
job with imageUrl=/renders/{key}, schemaHash, modelVersion, errorMessage
- backend: serve /renders/** from RENDER_OUTPUT_DIR + security permit
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>