ModelRefusalError

Error class representing a model refusal.

Providers report a refusal, such as a safety-policy refusal, as a successful response rather than an error. LangChain raises this error where a refusal cannot be treated as an answer, for example when structured output has nothing to parse, or when an agent uses refusal middleware.

The ModelRefusalError extends the LangChainError base class with the marker "model-refusal". Retrying the same request is unlikely to succeed, so the error is marked as not retryable.