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Aider is an open-source AI pair programming tool for the terminal (Apache-2.0, source). It edits code in your local git repo and commits as it goes. Aider treats any OpenAI-compatible endpoint as an OpenAI provider, so two environment variables point it at Opper.

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Setup

On Windows, use setx OPENAI_API_BASE ... and setx OPENAI_API_KEY ... instead.
The openai/ prefix is Aider’s own routing marker — it tells Aider to use its OpenAI-compatible client. Everything after it is the Opper model ID, which carries its own provider prefix. So anthropic/claude-sonnet-4-6 on Opper becomes openai/anthropic/claude-sonnet-4-6 on the Aider command line.

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Choosing a model

Any model ID from the catalog, prefixed with openai/. To make it stick, put it in .aider.conf.yml at the root of your repo:

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Troubleshooting

Aider needs the openai/ prefix to route through its OpenAI-compatible client. Without it, Aider tries to resolve the name against its built-in model list and fails.
OPENAI_API_KEY must hold your Opper key, not an OpenAI one. Opper keys start with op-.
Aider keeps a static metadata map for models it knows. The warning is cosmetic and the model still works; set --no-show-model-warnings to silence it.

Model catalog

Browse the catalog for model IDs and capabilities.

All integrations

Every app that runs on Opper.