AI Image Generation
When the Model Goes Down, Then What?
In Alice, the user says "draw me a picture," but behind the scenes Gemini may have timed out, Seedream rate-limited, and GPT Image errored. The user doesn't care which model failed — they only care: will the image come out?
Alice's Three States
Thinking
Generating image, please wait
Error
Model returned an error, switching to fallback
All Failed
All models unavailable, graceful degradation
Fallback Chain: Alice's Safety Net
Model A (Gemini) timed out after 15s
Timeout circuit breaker triggered → auto fallback
Switching to Model B (Seedream)
Fallback model takes over, transparent to user
Model B returned a rate-limit error
Concurrency limit hit, continuing to next fallback
Switching to Model C (GPT Image)
Third fallback steps in
Model C generated image successfully
User receives the image, switching completely transparent
All failed? Graceful degradation
"Sorry, service is busy. You've been added to the queue and will be notified."
Final Result: What the User Sees
Despite two model failures, the user still got their image
The user only sees the "Alice is drawing…" waiting state, then receives the result. Behind the scenes Model A timed out, Model B was rate-limited, Model C stepped in — all completely transparent to the user. This is the value of a fallback chain.
Three Product Approaches
Priority Ordering + Whitelist
Preset model priorities. Different scenes can specify different model combinations: for character close-ups use the best-quality model; for plain backgrounds use cheaper, faster ones.
Health Check Mechanism
Periodically probe the health of each model. Skip confirmed-down models immediately, bring them back online automatically on recovery. Don't waste user wait time on dead models.
Image-to-Image Degradation
Some models don't support image-to-image. If the fallback model doesn't support it, fall back to text-to-image: lower quality but at least an image is produced.
Users don't care which model you use — they only care whether the image comes out. In Alice, the fallback chain ensures that even if the primary models all fail, the worst case is the user waits a few extra seconds or receives a friendly message. They will never hit a cold error page.