OpenRouter OpenAI Compatibility

Overview

OpenRouter implements the OpenAI Chat Completions API specification (/v1/chat/completions). Existing OpenAI SDK code works with OpenRouter by changing two values: base_url and api_key. This gives you access to 400+ models from all providers through the same SDK interface.

Prerequisites

• An existing OpenAI SDK integration to migrate — Python or TypeScript code calling chat.completions.create
• An OpenRouter API key exported as OPENROUTER_API_KEY — see the openrouter-install-auth skill for setup
• Python 3.8+ with the openai package, or Node.js 18+ with the openai npm package — the same SDK you already use, no new dependency
• Optionally keep OPENAI_API_KEY exported too, so the Dual-Provider Pattern can switch back to direct OpenAI

Instructions

1. Apply The Two-Line Migration: point base_url at https://openrouter.ai/api/v1 and swap api_key to OPENROUTER_API_KEY; optionally add the HTTP-Referer / X-Title headers for app attribution.
2. Prefix every model string per Model ID Mapping — gpt-4o becomes openai/gpt-4o, o1 becomes openai/o1 — and try a non-OpenAI model (anthropic/claude-3.5-sonnet) through the same client.
3. Confirm your feature usage against What Works Identically (streaming, tools, JSON mode, stop, n) and adjust per What Differs — remove the organization param, plan around limited embeddings, and check logprobs support per model via /api/v1/models.
4. Layer in OpenRouter-Only Features through extra_body: ordered fallback model lists with "route": "fallback", provider preferences with sort: "price", or the plugins: [{"id": "web"}] web-search plugin.
5. Keep the migration reversible with the Dual-Provider Pattern — create_client() switches between direct OpenAI and OpenRouter off the LLM_PROVIDER environment variable.