LowRouterBeta

Aider

Aider is a terminal pair-programming agent. It reaches any OpenAI-compatible endpoint through its openai/ model prefix, which is what makes it work with LowRouter.

Verified against Aider v0.86.0. The config below is re-run against that release every week.

Configure

Aider reads the endpoint and key from the environment:

Bash
export OPENAI_API_BASE=https://api.lowrouter.ai/v1
export OPENAI_API_KEY=sk-lr-...

Then start it with the model name prefixed by openai/:

Bash
cd /your/project
aider --model openai/auto/mistralai/mistral-large-2512

The prefix is easy to miss. Aider decides where to send a request from the model name’s prefix: openai/ means “send this to whatever OPENAI_API_BASE points at”, and everything after it is passed through unchanged as the model. So the full name is openai/ followed by any ID from the model browser:

You want--model
LowRouter picks the routeopenai/auto/mistralai/mistral-large-2512
A pinned provideropenai/anthropic/anthropic/claude-sonnet-5
A pinned regionopenai/aws-bedrock/mistralai/ministral-3-3b-instruct/br-gru

OPENAI_API_BASE ends in /v1, with no trailing slash, because Aider appends /chat/completions itself.

You will see a warning on start-up that Aider does not know the model (“Unknown context window size and costs”). It is harmless: Aider works with a model it has no metadata for, and the real cost of every request is in your Activity. Silence it with --no-show-model-warnings.

Picking a model

Aider does not use function calling. It asks the model for edits in a text format it parses itself, so any chat model works. Look for good instruction following on code and a context window big enough for the files you add to the chat. The model browser tags context length per model.

  • Use a dedicated key. Aider re-sends the files in the chat on every turn, so a long session with large files spends quickly, and a key of its own makes that spend visible on the Activity page and revocable on its own.
  • Pin the route with an explicit model ID for repeatable pricing. An auto/ ID keeps the model fixed but may serve it from a different provider or region, with the same output at a different per-token price.
  • Read the diff. Aider commits to your repository by default; run with --no-auto-commits until you trust the model on your codebase.

Troubleshooting

  • 401: the key is not exported, or was exported in another shell. Aider reads OPENAI_API_KEY at start-up.
  • 404: OPENAI_API_BASE is missing /v1, or has a trailing slash.
  • “Model … is not supported” or a BadRequestError naming the model: the openai/ prefix is missing. Without it Aider tries to route the name through another provider’s SDK.
  • Latency feels off: check the provider field on the request in Activity. Aider doesn’t expose it; LowRouter does.