How to Switch LLM API Providers Without Downtime

Switching providers or gateways is mostly a configuration change. The risk is in quality and edge cases, so move traffic in stages and keep a rollback.

Quick answer

Change the base URL and key on one service, compare results on real traffic, move the rest in stages, and keep the old endpoint as a one-line rollback.

The checklist

Inventory every call site, model, key, region and special feature (tools, structured outputs, streaming, images).
Check compatibility. Most gateways speak the OpenAI API format. Note any provider-specific parameters you rely on.
Store the endpoint and key in configuration, not code, so switching is a config change.
Shadow test. Send a copy of real requests to the new route and compare outputs, errors and latency.
Canary. Move 5% of one service, then 25%, then 100%, watching cost per successful request.
Keep rollback one line away. Point the base URL back if anything degrades.
Reconcile the first invoice against your dashboard numbers.

Code

For OpenAI-compatible SDKs, switching is the base_url and key. See the quickstart and integration guides.

Coming from a specific gateway?

See the alternatives guides for OpenRouter, LiteLLM, Portkey and Helicone.

Frequently asked questions

How long does it take to switch LLM providers?

With an OpenAI-compatible endpoint, a day for the change itself, plus a few days of side-by-side measurement for confidence.

Can I switch without changing prompts?

Usually yes when the model stays the same. When the model changes, re-test prompts on your evaluation set.

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