OpenAI - type 'reasoning' was provided without its required following item

[xaliqm1]

Before submitting your bug report

• I've tried using the "Ask AI" feature on the Continue docs site to see if the docs have an answer
• I'm not able to find a related conversation on GitHub discussions that reports the same bug
• I'm not able to find an open issue that reports the same bug
• I've seen the troubleshooting guide on the Continue Docs

Relevant environment info

- OS:
- Continue version:
- IDE version:
- Model:
- config:
  

  
  OR link to agent in Continue hub:

Description

When using GPT-5 (or o-series reasoning models) via the openai provider, the conversation fails with the following error:type 'reasoning' was provided without its required following item.","type":"invalid_request_error","param":"input","code":null}

To reproduce

Configure a model in config.yaml using provider: openai and model: gpt-5 (or o1/o3).

Engage in a multi-turn conversation where the model generates "thinking" or reasoning steps.

On the subsequent prompt, the API returns a 400 error because the history injected by Continue violates the reasoning-item sequence rules.

Log output

[sestinj]

Related issues:

• 'reasoning' was provided without its required following item #8933 - Same error: 'reasoning' was provided without its required following item (appears to be a duplicate)

[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.