Error: Model - 400

[rangerdirector]

Error Details

Model: Unknown
Provider: Unknown
Status Code: 400

Error Output

{"message":"Item 'rs_05fcf8a672f793b100696ca4732bb08197ad3765d5cfa9c927' of type 'reasoning' was provided without its required following item.","type":"invalid_request_error","param":"input","code":null}

Additional Context
Please add any additional context about the error here

[rangerdirector]

• name: gpt-5-nano
  provider: openai
  model: gpt-5-nano

[rangerdirector]

Error handling model response
There was an error handling the response from the model.

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[sestinj]

Related issues:

• 'reasoning' was provided without its required following item #8933 - Same error: "type 'reasoning' was provided without its required following item" with OpenAI reasoning models (GPT-5.1 Codex)
• Error: G 5 - 400 #9264 - Same error with GPT-5 reasoning models
• Error: using organization model. 400 #9274 - Same error with Azure-hosted GPT-5.1 reasoning model

[RomneyDa]

Fixed by #11785
There may still be cases where this could happen when using one provider like Anthropic and then switching the same conversation to OpenAI. If you run into this, please open a new issue with details.