What a 401 Error Is Telling You

Formats d'échangeEN2026-10-25

A failed API request can send you looking at prompts, model settings, and account balances. With a 401 error, start somewhere simpler: authentication. Work through the checks below in order, changing one thing at a time.

§ Step 1: Understand what 401 actually means

HTTP 401 Unauthorized means the request lacks valid authentication credentials for the target resource. Despite its name, it is primarily an authentication signal. A 403 Forbidden means the server understood the request but refuses to fulfill it; access restrictions may be involved. Neither response, by itself, proves that the model is unavailable. ([rfc-editor.org](https://www.rfc-editor.org/rfc/rfc9110.html))

Begin by saving the exact status and error message. Avoid changing your prompt or switching models until you have checked the credentials attached to the failed request.

§ Step 2: Read the response before changing configuration

Inspect the response body for a more specific explanation. Also inspect the WWW-Authenticate response header: HTTP requires a server generating a 401 to provide an authentication challenge there. That challenge can help identify the expected authentication scheme. ([rfc-editor.org](https://www.rfc-editor.org/rfc/rfc9110.html))

Record the error type, message, timestamp, and request identifier, if present.
Check whether the response identifies a missing credential, rejected key, or malformed header.
Keep credentials out of screenshots, logs, and support messages.

Treat the message as evidence, not as permission to expose the request's secrets.

§ Step 3: Check the key and destination together

Confirm that the key belongs to the service receiving the request. For Vana API's OpenAI-compatible route, the documented setup pairs the Vana API key with the base address ending in /v1. Its request example sends that key through Bearer authentication. ([vanaapi.com](https://vanaapi.com/plug-in?locale=en))

Compare your configuration against that pairing. Check for leading or trailing whitespace, copied quotation marks, truncated values, and placeholder text. If the key has been revoked or exposed, replace it through your account's key-management controls rather than continuing to test it.

If you are starting without credentials, create a Vana API account and obtain your own API key before continuing.

§ Step 4: Match authentication to the protocol

Do not assume every client uses the same configuration field. Vana API's setup guide uses ANTHROPIC_AUTH_TOKEN for Claude Code, an API-key field for OpenAI-compatible clients, and GEMINI_API_KEY for Gemini CLI. Its native Gemini request example uses the x-goog-api-key header. ([vanaapi.com](https://vanaapi.com/plug-in?locale=en))

For a Bearer-authenticated request, use the shape Authorization: Bearer YOUR_API_KEY, replacing the placeholder.
In a client's dedicated API-key field, enter the key itself unless its instructions explicitly require a prefix.
Check the documented base-path rules for your chosen client instead of adding version segments by guesswork.

Inspect header names and whether a value is present without printing the secret.

§ Step 5: Inspect the running application

Check the configuration available to the process making the request, not just the file you edited. Verify the selected environment, secret name, deployment settings, and client profile.

After updating credentials, restart the relevant terminal, application, or deployment where necessary. Look for a second configuration source that could override your change. Compare local and deployed settings without copying production secrets into development tools.

§ Step 6: Make one minimal test

Send a short request using the documented route, required fields, and one supported model. Remove optional tools, attachments, and custom middleware for this test. Keep the same key and destination so the result answers a specific question.

If it succeeds, restore optional features one at a time. If it still returns 401, focus on authentication. If the status changes, investigate the new response rather than treating every failure as the original problem.

§ Step 7: Retry deliberately, then escalate safely

A 401 permits another attempt with new or replaced credentials. Do not build an endless retry loop around unchanged credentials; make a meaningful correction before testing again. ([rfc-editor.org](https://www.rfc-editor.org/rfc/rfc9110.html))

If the failure persists, send support the timestamp, request identifier, client version, route, and sanitized error body. Never send the full key. The useful question is precise: which credential reached which endpoint, and why was it rejected?