Aider OpenAI-Compatible API Setup with RouterPlex

Aider works with RouterPlex through its OpenAI-compatible API support. Set the API base and key, then use an openai/-prefixed RouterPlex model ID when launching Aider.

Quick setup #

Create a dedicated RouterPlex key for Aider and export these variables:

export OPENAI_API_BASE="https://api.routerplex.com/v1"
export OPENAI_API_KEY="sk-..."
 
aider --model openai/claude-opus-4-8

The openai/ prefix tells Aider which API format to use. RouterPlex receives the part after the slash as the model ID.

You can switch to another model without changing the endpoint:

aider --model openai/gpt-5.5
aider --model openai/gemini-3.5-flash

Use an ID from the current RouterPlex model catalog.

Persist the configuration #

Add the settings to ~/.aider.conf.yml:

openai-api-base: https://api.routerplex.com/v1
openai-api-key: sk-...
model: openai/claude-opus-4-8
weak-model: openai/claude-haiku-4-5

Prefer an environment variable or local secret mechanism for the key. Do not commit a live credential into a repository.

The weak model handles lower-stakes work and can reduce cost, while the primary model remains available for the main coding task.

Set a server-side budget #

Aider sessions can become expensive when a large repository is repeatedly mapped or a task needs many edit/test cycles.

Create a key named after the repository and cap it at the most you are willing to spend during the session. The budget remains effective even if Aider retries or a local cost estimate is wrong.

Optionally allowlist only the primary and weak model. This prevents an accidental configuration change from selecting a more expensive model.

Verify the route #

Start Aider in a small repository and ask for a read-only task:

/ask Explain the project structure without editing files.

Then check the RouterPlex dashboard for the key, model, token count, and cost.

Common Aider errors #

Unknown model

Confirm that the command uses openai/routerplex-model-id and that the part after openai/ exactly matches the RouterPlex catalog.

Authentication error

Make sure OPENAI_API_KEY is exported in the shell that launches Aider. A terminal, IDE task, and container can each have different environments.

Requests go to api.openai.com

Check OPENAI_API_BASE or openai-api-base. It must point to https://api.routerplex.com/v1.

Repository map costs too much

Use a lower-cost weak model, narrow the task, and set a smaller RouterPlex key budget while tuning the workflow.

See the concise Aider integration reference, or start with $5 and run one budget-capped coding session.