Fixes invalid_request_error for tool calling with Anthropic models#192
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zachdaniel merged 1 commit intoash-project:mainfrom Apr 24, 2026
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Anthropic does not allow "prefilling assitant messages", meaning the last message of the `messages` parameter to ReqLLM `generate_object/4` may not have the role `:assistant`. See: ash-project#191 This commit prevents run_loop/10 and stream_iteration/1 in AshAi.ToolLoop from appending assistant messages to the context when the model provider is anthropic. --- I've changed `defp resolve_model(model, _opts), do: model` to return `ReqLLM.model!(model)` in `AshAi.ToolLoop`. This makes working with the model inside the module simpler ans seems to be recommended by ReqLLM https://github.com/agentjido/req_llm/blob/main/lib/req_llm.ex#L353 Would have done the same in `AshAi.Actions.Prompt` for resolve_model_spec since model is passed from Prompt to ToolLoop and people using the fn variant of resolve_model this would be a breaking change.
zachdaniel
approved these changes
Apr 24, 2026
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Anthropic does not allow "prefilling assitant messages", meaning the last message of the
messagesparameter to ReqLLMgenerate_object/4may not have the role:assistant.See: #191
This commit prevents run_loop/10 and stream_iteration/1 in AshAi.ToolLoop from appending assistant messages to the context when the model provider is anthropic.
I've changed
defp resolve_model(model, _opts), do: modelto returnReqLLM.model!(model)inAshAi.ToolLoop. This makes working with the model inside the module simpler ans seems to be recommended by ReqLLM https://github.com/agentjido/req_llm/blob/main/lib/req_llm.ex#L353Would have done the same in
AshAi.Actions.Promptfor resolve_model_spec since model is passed from Prompt to ToolLoop and people using the fn variant of resolve_model this would be a breaking change.Contributor checklist
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