gpt-5.x models served via the OpenAI Responses API reject requests that
include temperature or top_p with:
{"detail":"Unsupported parameter: temperature"}
This caused ClaudeCode agent/subagent tool requests to fail with a 400
error when an OpenAI group had the Messages-format support enabled.
Root cause: AnthropicToResponses and ChatCompletionsToResponses were
unconditionally forwarding temperature and top_p from the incoming
request to the ResponsesRequest, even though all gpt-5.x reasoning
models reject these sampling parameters.
Fix:
- Add isReasoningModel(model string) bool helper that returns true for
any model whose name starts with "gpt-5".
- Skip temperature and top_p when converting to ResponsesRequest for
reasoning models. Non-reasoning models (e.g. gpt-4o) are unaffected.
- ResponsesRequest.Temperature and TopP are already *float64 with
omitempty, so nil values are safely omitted from the JSON body.
Tests:
- TestAnthropicToResponses_TemperatureStrippedForReasoningModel
- TestAnthropicToResponses_TemperatureStrippedForAllGpt5Variants
- TestChatCompletionsToResponses_TemperatureStrippedForReasoningModel
- TestChatCompletionsToResponses_TemperaturePreservedForNonReasoningModel
Fixes#2487
276b5c7755