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
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Quickstart
npx modelis-openai
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Then point any OpenAI-compatible tool at it:
Setting
Value
Base URL
http://127.0.0.1:8787/v1
API key
your RapidAPI key
Model
modelis-auto
Drop it into your tool
Aider
export OPENAI_API_BASE=http://127.0.0.1:8787/v1
export OPENAI_API_KEY=
aider –model openai/modelis-auto
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Cline / Roo Code — API Provider OpenAI Compatible, Base URL http://127.0.0.1:8787/v1, Model ID modelis-auto.
Continue (~/.continue/config.yaml)
models:
– name: Modelis
provider: openai
model: modelis-auto
apiBase: http://127.0.0.1:8787/v1
apiKey:
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Any OpenAI SDK
from openai import OpenAI
client = OpenAI(base_url=”http://127.0.0.1:8787/v1″, api_key=””)
print(client.chat.completions.create(
model=”modelis-auto”,
messages=({“role”: “user”, “content”: “Hello”}),
).choices(0).message.content)
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How it works
Reads the key from Authorization: Bearer (or MODELIS_RAPIDAPI_KEY).
Rewrites the request model to modelis-auto (configurable).
Forwards to the RapidAPI gateway with X-RapidAPI-Key / X-RapidAPI-Host.
Relays the response — including SSE streams and rate-limit headers — unchanged.
It also answers GET /v1/models and GET /health so tools that probe on startup don’t choke.
Honest notes
It routes to a paid API (there’s a free tier to start). The point of the proxy is to remove the integration friction, not to give anything away.
Cursor isn’t supported — it sends requests from its own servers, so a localhost endpoint can’t be reached. This is for tools that call the API from your machine.
Links
If you try it in a tool I didn’t list, I’d love to hear how it goes.
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