Claude can stop with stop_reason "refusal" (a creative model such as Fable 5
hitting a content boundary). Return a typed ErrModelRefusal carrying any refusal
text instead of a generic "no response": an empty-content refusal previously
looked identical to an empty/failed response, so callers could not tell "the
model declined" from "the request failed".
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Sergey Kozyrenko
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