One API Key for GPT, Claude, Gemini, and Qwen: A Practical Guide to OpenAI-Compatible Model Routing

One API Key for GPT, Claude, Gemini, and Qwen: A Practical Guide to OpenAI-Compatible Model Routing

If you’ve built anything serious with LLM APIs, you’ve probably hit this pattern: GPT is great for one task, but too expensive for another. Claude is better at long-context reasoning, but you don’t want to rewrite your whole client. Gemini or Qwen may be good enough for cheaper background jobs. Your app slowly turns into a pile of provider-specific SDKs, env vars, retry logic, and billing dashboards. Not fun. The cleanest version of this setup is simple: keep your app speaking the OpenAI API format, but route requests to different models behind the scenes. That’s the idea behind an OpenAI-compatible AI gateway. Disclosure: I work on TokenBay, an AI model API gateway. This post is based on the setup I usually recommend when developers want access to multiple model families without rewriting their app every time they test a new provider. The Problem Most AI apps start with one model provider. That works fine until you need to optimize for cost, latency, quality, availability, or task type. For example: Use a strong reasoning model for complex user-facing answers. Use a cheaper model for summarization, tagging, extraction, or internal jobs. Fall back to another provider when one API is slow or unavailable. Test new models without refactoring half your codebase. The painful part is not calling one API. The painful part is maintaining five slightly different API integrations. The Practical Pattern Instead of wiring every provider directly into your app, you can use an OpenAI-compatible gateway. Your application keeps using the…

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