X_AI_REQUEST_INVALID
Means
the provider would reject this request
Typical cause
a reasoning control the chosen model does not have — effort or adaptive thinking on a pre-4.6 model, or thinking: 'disabled' above a model's effort cap
Fix
set model: on the llm() declaration to one whose MODELS row has the control, or drop effort/thinking from definePrompt — editing the template alone leaves the control in the request