Aider error
Aider: The API provider is not able to authenticate you. Check your API key
The API provider is not able to authenticate you. Check your API key.Status: By designLast verified 2 documented fixes2 sources
What it means
The provider returned a litellm AuthenticationError. Aider prints this description, treats the error as non-retryable, and stops the request.
Causes
- Missing, wrong or expired API key for the selected provider (aider's exception description: "Check your API key.").
How to fix it
- Fix 1.
Provide the correct key with --api-key, or through environment variables or config files as described in the API keys docs.
Terminalaider --model deepseek --api-key deepseek=your-key-goes-here - Fix 2.
If you have no keys, aider offers to connect you to OpenRouter (Models and API keys doc).
More Aider errors
All 17 Aider errorsThe LLM did not conform to the edit format.Status: WorkaroundSearchReplaceNoExactMatch: This SEARCH block failed to exactly match lines in {path}Status: WorkaroundModel gpt-3.5-turbo has hit a token limit!Status: WorkaroundModel foobar: Unknown context window size and costs, using sane defaults.Status: By designModel azure/gpt-4-turbo: Missing these environment variables:Status: By designaider: The term 'aider' is not recognized as a name of a cmdlet, function, script file, or executable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.Status: Workaroundaider-chat 0.23.0 requires somepackage==X.Y.Z, but you have somepackage U.W.V which is incompatible.Status: WorkaroundThe API provider has rate limited you. Try again later or check your quotas.Status: By design
Related reading
- Aider vs Claude Code in 2026: Git-First Open Source vs Subagent RuntimeAider vs Claude Code: git-first, model-agnostic Aider against the Claude Code runtime of subagents and hooks. Compare architecture, cost, governance and fit.
- Aider vs Claude Code: Open Source vs Commercial AI Coding CLIAider is open source and works with any model. Claude Code is Anthropic's commercial agent. Here is how they compare for TypeScript.
FAQ
What does "The API provider is not able to authenticate you. Check your API key" mean in Aider?
The provider returned a litellm AuthenticationError. Aider prints this description, treats the error as non-retryable, and stops the request.
How do I fix "The API provider is not able to authenticate you. Check your API key"?
There are 2 documented fixes. Start with the first: Provide the correct key with --api-key, or through environment variables or config files as described in the API keys docs.
Is this Aider error fixed?
Status: By design. Expected behavior, not a bug. The documented fixes change the setup that triggers it. Affected versions: All versions that use litellm exception mapping.
Sources
Last verified against 2 sources: official docs, maintainer replies and release notes.
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