Coding assistants like Aider, Cline, and Continue all speak the OpenAI wire protocol — point them at a base_url, give them an API key, done. That makes swapping in a different LLM backend trivial... if that backend uses Authorization: Bearer.
The flat-priced, auto-routing API I'd been using doesn't. It's distributed through RapidAPI, which authenticates with an X-RapidAPI-Key header instead of Bearer. So I couldn't just drop it into Aider. The fix turned out to be ~120 lines, so I open-sourced it.
modelis-openai
A zero-dependency local proxy (MIT, Node 18+). It listens on 127.0.0.1, speaks plain OpenAI, rewrites the auth header, and forwards to the upstream gateway. Streaming (stream: true) is piped straight through, so token-by-token output works exactly as with the OpenAI API.
your tool ──OpenAI(Bearer)──▶ modelis-openai (localhost) ──X-RapidAPI-Key──▶ upstream ──▶ best model
