OpenAI-Compatible API Gateway: Setup Without Changing Your Code
An OpenAI-compatible API gateway lets you swap models, add budgets, and add caching to any app that already uses the OpenAI SDK — with zero code changes. Here's the setup.
An OpenAI-compatible API gateway exposes the same endpoints and request format as OpenAI's API, so any app built on the OpenAI SDK can point at it by changing one base URL. That one change unlocks model flexibility, cost control, and caching across your whole app.
Setup is deliberately boring: create the gateway, add your keys, copy one base URL.
Setup steps
- Create a gateway workspace and add your provider API keys (BYOK).
- Copy your gateway's base URL (it looks like OpenAI's but points at your workspace).
- In your app, set baseURL to the gateway URL and keep everything else.
- Configure routing rules and a monthly budget limit.
- Run a smoke test with your existing SDK.
Because the request/response format is OpenAI-compatible, models from Anthropic, Google, and others appear to your app as normal chat completions (with normal tool calling and structured outputs).
What you unlock
- Model choice per request — swap or route without SDK changes.
- Hard budget limits and spend analytics on every request.
- Prompt caching and request retries at the gateway layer.
- Per-project and per-key usage reporting.
Gotchas to watch
Keep your original OpenAI key out of client-side bundles. Verify streaming and tool calling both work on your gateway. And check that your gateway forwards any provider-specific headers you rely on (like reasoning-effort) or maps them for you.
FAQ
What is an OpenAI-compatible API gateway?+
A service that exposes OpenAI's API format so existing OpenAI SDK clients can route to many providers through one base URL.
Do I need to change my code?+
No. You change the baseURL, and your SDK continues to work against the gateway.
What do gateways add beyond model access?+
Hard budget limits, spend analytics, caching, retries, and per-key reporting — usually the reason teams add one.
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