Add an OpenRouterModel

[DouweM]

Description

The OpenRouter API is mostly but not completely OpenAI Chat Completions-compatible, so using OpenAIChatModel with OpenRouterProvider mostly works, but not entirely:

• OpenRouter uses non-compatible finish reason #2844
• Handle error response from OpenRouter as exception instead of validation failure #2323

And some OpenRouter-only features cannot currently be implemented easily:

• Store OpenRouter provider metadata in ModelResponse vendor details #1849
• Support prefill by ending history with ModelResponse #2778
• Can I get thinking part from openrouter provider using google/gemini-2.5-pro? #2999

  • pydantic-ai/pydantic_ai_slim/pydantic_ai/models/openai.py

    Lines 521 to 522 in aca70eb

    	# NOTE: We don't currently handle OpenRouter `reasoning_details`:
    	# - https://openrouter.ai/docs/use-cases/reasoning-tokens#preserving-reasoning-blocks

• Add OpenRouterModel #1870 (comment)

Two PR to implement an OpenRouterModel was recently submitted, but it involved too much duplication with OpenAIChatModel for my taste, instead of subclassing and only changing what's necessary: #1870 #2409. However, the Groq and HuggingFace models basically copy-paste OpenAIChatModel as well, so I think the benefit outweighs the cost. I've reopened the most recent of those 2 PRs.

References

No response

[mister-jack]

I love this, Openrouter is a great platform. One thing that would be AMAZING -
Openrouter can optionally include detailed usage metrics (including cost breakdowns) - see https://openrouter.ai/docs/use-cases/usage-accounting, would be good to get access to this passed through as-is to the RunUsage.details attribute?

Example of the data returned from Openrouter:

{

"usage": {
  "completion_tokens": 2,
  "completion_tokens_details": {
    "reasoning_tokens": 0
    },
  "cost": 0.95,
 "cost_details": {
    "upstream_inference_cost": 19
   },
  "prompt_tokens": 194,
  "prompt_tokens_details": {
    "cached_tokens": 0,
    "audio_tokens": 0
  },
  "total_tokens": 196
  }
}