Refine temperature/top_p handling for reasoning models

[mayeco]

Update handling of temperature and top_p for OpenAI models.

This fix issue #2278

Checklist

• If the PR is changing/adding functionality, are there tests to reflect this?
• If there is an example, have you run the example to make sure that it works?
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[Copilot]

Pull request overview

Updates chat-completion option normalization to avoid stripping sampling params (temperature, top_p) for non-OpenAI “reasoning effort” models (notably Gemini), while still handling OpenAI reasoning-model quirks.

Changes:

• Only remove temperature/top_p for OpenAI reasoning models (o1*, o3*) instead of all models that support reasoning_effort.
• Add model-name normalization logic in select_chat_options to gate this behavior.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

openhands-sdk/openhands/sdk/llm/options/chat_options.py:59

• The Gemini 2.5-pro substring check is case-sensitive and bypasses the model_lower normalization introduced above. For consistency with other model checks in this function (and with model_features.model_matches, which is case-insensitive), use model_lower (or another normalized form) so variants like provider-prefixed or differently-cased model IDs don’t skip this defaulting behavior.

        # Gemini 2.5-pro default to low if not set
        if "gemini-2.5-pro" in llm.model:
            if llm.reasoning_effort in {None, "none"}:
                out["reasoning_effort"] = "low"

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[enyst]

I think it’s not only o1, o3, there are also Claudes, open models, GPTs

I’d actually suggest that since we removed temperature by default, we could remove this temperature special cases for all

The other models will also get nothing set (from the SDK), so they all should respect user choice

[enyst]

Thank you for the contribution! This bit of code might be unnecessary now, since we just merged #1989

[mayeco]

yes I understand @enyst but #1989 but still not fix my issue.

If I have a reasoning model like gemini, then set the temperature to 0.0. then will be 1 (the default)

https://github.com/OpenHands/software-agent-sdk/blob/main/openhands-sdk/openhands/sdk/llm/options/chat_options.py#L43

{
  "generationConfig": {
    "maxOutputTokens": 65536,
    "temperature": 1,  // ← Incorrect: should be 0.0
    "thinkingConfig": {
      "includeThoughts": true,
      "thinkingLevel": "HIGH"
    }
  }
}

[enyst]

Oh, I agree. I just don't fully understand, why keep the code for o1 and o3?

[mayeco]

yes. maybe is not only o1 / o3 we need to make a list of models that the reasoning fail when temperature is set.
that is better @enyst ?

[enyst]

Sounds good!