A 401 usually means your request failed an identity check
You connect a coding tool to a relay, send your first prompt, and get a 401 instead of an answer. In plain English, that response usually means: the service could not accept the credentials attached to your request. It does not automatically mean the model is unavailable or your prompt is wrong.
A relay sits between your application and a model provider. Your application authenticates with the relay, and the relay handles the onward request. That creates more than one place where authentication can fail. Start with your connection to the relay, but read the error message before deciding which side needs attention.
Check that your key belongs to the relay
A common beginner mistake is putting a model provider's API key into a tool configured to use a relay. A key is not a universal password: it normally belongs to the service that issued it.
When using SwiftRelay, configure your client with a SwiftRelay API key and the appropriate SwiftRelay endpoint. Do not assume that a key issued directly by another provider will authenticate against the relay.
- Check the source: confirm that you copied the key from the relay account you intend to use.
- Check the copy: remove accidental spaces, line breaks, or literal quotation marks around the value.
- Check its status: a revoked, deleted, or otherwise inactive key may no longer authenticate.
If a key has appeared in a screenshot, public repository, or shared log, replace it rather than continuing to test with it.
Match the endpoint to the client
A correct key sent to the wrong service will not establish the identity you intended. Check the host alongside the key, especially if you recently switched from a direct provider connection.
For SwiftRelay, the API host is https://api.fastapirelay.com. Claude Code and Gemini CLI take that bare host. OpenAI-compatible SDKs use a base URL with /v1: https://api.fastapirelay.com/v1.
Follow the client's configuration instructions rather than adding paths by guesswork. An incorrect path may produce a routing error instead of a 401, but checking the endpoint still helps establish where your credentials are going. Never send a real key to an unfamiliar host while troubleshooting.
Confirm your running tool actually sends the key
Saving a key does not guarantee that the next request uses it. A terminal may still contain an old environment variable. An editor extension may read a different settings file. A running process may need to restart before it sees your changes.
- Confirm the selected connection is the relay connection, not an older provider profile.
- Check whether environment variables override the settings you just edited.
- Restart the relevant tool after changing credentials when necessary.
- Use the authentication format expected by that client and endpoint.
OpenAI-compatible requests commonly use an Authorization header containing Bearer followed by the key. Other client integrations can use different headers or authentication settings. Do not assume every tool wants the same header.
Read the error before changing billing or models
A 401 usually points toward authentication. A 403 commonly indicates a permission restriction, while a 429 commonly indicates rate limiting or quota enforcement. Services can map errors differently, so the response body matters more than a memorized checklist.
If the message explicitly identifies an upstream authentication failure, your local relay key may not be the problem. Likewise, an explicit balance or account restriction deserves its own investigation. Repeatedly changing models or adding funds is not a reliable fix for an unexplained 401.
Make one clean test before asking for help
Test one small request with the intended endpoint and a confirmed key. If it still fails, collect the status, error message, client name, and request identifier if available. Remove credentials and private prompt content before sharing diagnostics.
For a straightforward starting point, sign up for SwiftRelay and configure one supported client first. Once that connection authenticates, expand your setup one change at a time. A 401 is usually a credential checkpoint, not a reason to rebuild everything.