Aider failing with authentication or missing-key errors is almost always a configuration problem. Here's how to diagnose and fix API key issues so Aider can reach your model.
You launch Aider and it immediately errors out with a message about a missing or invalid API key, or an authentication failure from the provider. It may mention that no key was found, or that the key was rejected.
This is one of the most common first-run problems, and it has nothing to do with your Swift code. Aider simply cannot reach the model.
The good news is that authentication errors are almost always configuration issues, not bugs. They are quick to fix once you know where to look.
Work through the checks below in order. Most cases resolve at the first or second step.
Aider looks for your API key in specific environment variables that depend on your provider. If that variable is not set in the shell where you run Aider, it cannot authenticate.
Confirm the variable is actually present in your current shell session, not just in a file you edited earlier. Environment changes often require opening a new terminal or re-sourcing your shell profile.
A frequent mistake is setting the key in one shell and running Aider in another. Make sure they are the same environment.
Check the exact variable name against Aider's documentation for your provider. A typo in the variable name means Aider never sees the key.
Even when a key is set, it can be incorrect. Copy-paste errors, trailing spaces, or a partially copied key all cause rejection.
Regenerate the key in your provider's console if you are unsure, and paste it carefully. Watch for hidden whitespace at the beginning or end.
Make sure you are using a key for the right provider. A key from one provider will never authenticate against another provider's model.
If you recently rotated or revoked keys, confirm you are using the current, active one. Old keys stop working the moment they are revoked.
Aider needs the model you select to match the key you configured. If you point Aider at one provider's model but supply another provider's key, authentication fails.
Double-check the model identifier you passed on the command line or in your config. It should belong to the same provider as your key.
Some models also require specific access or account enablement. If your account does not have access to a given model, requests will be denied.
Align the three pieces: the provider, the key, and the model. When they match, authentication succeeds.
Providers often require an active billing setup before API keys will work. A brand-new account without billing configured can produce authentication or authorization errors.
Log into your provider's console and confirm that billing is set up and that your account is in good standing. Some accounts also need to accept terms or enable API access explicitly.
Usage limits or spending caps can also block requests once reached. Check whether you have hit a configured limit.
This is an account-side fix, not an Aider fix. Resolve it in the provider's dashboard, then retry.
If your machine sits behind a corporate proxy or VPN, requests to the model provider may be blocked or rewritten. That can surface as authentication or connection failures.
Test whether you can reach the provider's API from your terminal at all. If a basic request fails, the problem is network access, not your key.
Corporate networks sometimes require proxy environment variables or allowlisting of the provider's domains. Coordinate with your IT team if so.
Switching networks temporarily, for example off a restrictive VPN, is a quick way to isolate whether the network is the culprit.
After each change, restart Aider in a fresh terminal so it picks up the current environment. Stale shells are a common reason a fix appears not to work.
Run a trivial request, such as asking Aider a simple question or making a tiny edit to one file. If it responds and can reach the model, authentication is working.
Once it connects, return to your normal iOS workflow: add Swift files, request changes, then build and verify in Xcode. Authentication only needed to be solved once.
Store your key securely for the future. Keep it in your shell profile or Aider's config, and never commit it to your repo.
Set your API key in your shell profile so it is available in every new terminal automatically. This avoids the one-shell-only trap.
Keep any Aider config that contains secrets out of git by adding it to .gitignore. Leaking a key to a repository can lead to unexpected charges.
Document which provider and model your team uses so everyone configures the matching key. Mismatches are a frequent source of confusion.
Finally, remember that these are provider and environment issues. Aider is only the messenger; the fix lives in your shell and your provider account.
If you have verified the variable, the key value, the model, billing, and the network and Aider still refuses to connect, slow down and isolate one variable at a time. Try a different, known-good model from the same provider to see whether the problem is model-specific rather than key-specific.
Check the provider's status page for an active outage. Occasionally the failure is on their side, and no amount of local configuration will help until service recovers.
Confirm your Aider version is current, since older builds may reference outdated endpoints or variable names. The official documentation lists the expected configuration for the current release.
As a last resort, reduce the setup to its simplest form: a fresh terminal, one exported key, and one trivial request. If that minimal case works, reintroduce your config piece by piece until the offending setting reveals itself. Methodical isolation almost always beats guessing.
The exact wording of the failure usually tells you which cause you are dealing with, so read it rather than skimming. A message about a missing or unset key points straight at the environment: the variable is absent in the shell running Aider.
A message about an invalid or rejected key means the value reached the provider but was refused, which points to a wrong, truncated, or revoked key rather than a missing one. These two look similar at a glance but call for different fixes.
Authorization or permission errors, as opposed to authentication errors, often indicate an account-side problem: no billing, no access to the chosen model, or a spending limit reached. The request was understood but not allowed.
Connection or timeout errors usually mean the request never completed, which points to a network, proxy, or VPN issue instead of anything about the key itself. Matching the wording to the category saves you from trying fixes for the wrong problem. When in doubt, note the exact text and work the matching cause above.
You likely set it in a different shell, or the terminal running Aider started before the variable was set. Open a fresh terminal or re-source your shell profile, and confirm the exact variable name matches Aider's docs.
Yes. If you select a model from a different provider than your key, or a model your account cannot access, authentication or authorization fails. Match provider, key, and model.
Aider reads the key from your environment or config file. Keep config files with secrets out of git by adding them to .gitignore so the key is never committed.
Check that billing is enabled in your provider console, that you have not hit a spending limit, and that no proxy or VPN is blocking the provider's API.