gemini-2.5-flash doesn't show reasoning with OpenRouter

[meizheng4646]

What happened?

Hi, I noticed that when using Gemini 2.5 Flash with OpenRouter it doesn't show any reasoning despite the model supporting it. I tried to read the code and i think somehow the app drop the 'reasoning_effort' from the request when it's actually necessary. I tried to modify the code myself but I still can't figure out why my modification doesn't work.

Version Information

Latest image version as of

UTC current time is 15:31:00
UTC current date is 29th Friday August 2025.

Steps to Reproduce

What browsers are you seeing the problem on?

No response

Relevant log output

-

Screenshots

Code of Conduct

• I agree to follow this project's Code of Conduct

[danny-avila]

LibreChat does not drop reasoning, it always sends the parameter as true for OpenRouter. For example, here's what gets sent when I select the gemini-2.5-pro vs gemini-2.5-flash.

Pro seems more likely to reason than flash, or flash might not support reasoning via OR.

gemini-2.5-pro

{
  "model": "google/gemini-2.5-pro",
  "user": "some-user-id",
  "stream": true,
  "include_reasoning": true,
  "messages": [
    {
      "role": "user",
      "content": "what is the meaning of life"
    }
  ]
}

gemini-2.5-flash

{
  "model": "google/gemini-2.5-flash",
  "user": "some-user-id",
  "stream": true,
  "include_reasoning": true,
  "messages": [
    {
      "role": "user",
      "content": "what is the meaning of life"
    }
  ]
}

[meizheng4646]

But include_reasoning doesn't actually do any reasoning for gemini flash based on openrouter activities history. While with reasoning_effort, even a simple hi can trigger the reasoning mechanism. My earlier screenshot show you that gemini flash is indeed support reasoning. You can try this curl if you don't believe me.

 curl -X POST "https://openrouter.ai/api/v1/chat/completions" -H "Authorization: Bearer REDACTED" -H "Content-Type: application/json" -d '{"model": "google/gemini-2.5-flash","reasoning_effort": "medium","messages": [{"role": "user", "content": "Solve: 2x + 5 = 13"}]}'

[meizheng4646]

This is what happened. If I use include_reasoning instead of reasoning_effort when dealing with Gemini Flash on OpenRouter

[danny-avila]

You can also set reasoning_effort via LC but I will look into why it's not going through with gemini flash. Thanks will also review OR docs

[meizheng4646]

Thanks, I really love LibreChat. Thank you for your hard work.

BTW, I did try to set addparams and customparams at librechat.yml and none of it working, that's why i suspect that somehow the reasoning_effort got omitted or transformer. my suspect is "OpenAIClient.js".

[meizheng4646]

if you are wondering how did i find out about adding reasoning_effort there, it's actually mentioned in Gemini docs instead of openrouter docs, but it works the same somehow. In https://ai.google.dev/gemini-api/docs/openai#javascript_1