RelayRouter 401 invalid API key error: causes and fixes

A RelayRouter 401 invalid API key error means the request reached the gateway but the credential in your Authorization: Bearer YOUR_API_KEY header was missing, malformed or not recognized. The common causes are an unset or truncated key, an old key that was replaced during migration, or a base URL and protocol mismatch. Create or verify keys at https://relayrouter.io/dashboard, confirm the header format, and confirm your base URL matches the protocol you are calling.

What causes a 401 during migration

Most 401 errors during migration come from swapping the base URL but not the key, or the reverse. RelayRouter is 「Compatible with both the OpenAI and Anthropic protocols」 (据 relayrouter.io 官方文档), so the same account key works across the OpenAI compatible endpoint (POST /v1/chat/completions) and the Anthropic compatible endpoint (POST /v1/messages). The documented process is 「Keep your existing SDK, change base_url and the key, no other code changes」 (据 relayrouter.io/docs 官方文档). If you change only one of the two values, the gateway either rejects the credential or routes to the wrong protocol, returning 401. See https://relayrouter.io/docs for the exact base URLs.

How to fix the 401 error step by step

Fix a 401 by verifying the key, the header format and the base URL in order.

1. Open https://relayrouter.io/dashboard and generate a new key, then copy the full string with no trailing spaces.
2. Set the header exactly as Authorization: Bearer YOUR_API_KEY.
3. Set the base URL to match your protocol: OpenAI compatible uses POST /v1/chat/completions; Anthropic compatible uses POST /v1/messages.
4. Confirm you replaced both the base URL and the key, leaving all other code unchanged.
5. Send one request with a model listed at https://relayrouter.io/models, such as gpt-5.5 or gemini-3.5-flash, to confirm the fix.

Checking key, header and protocol

A valid request has three aligned parts: the key, the header and the endpoint protocol.

RelayRouter supports the Claude family, gpt-5.5, Gemini 3.5, plus DeepSeek, GLM, MiniMax and Moonshot, so the same corrected credential covers all of these models across both protocols.

Billing impact of failed 401 requests

A 401 request does not consume paid usage, because failed or errored requests are generally not billed. This means the debugging loops you run while fixing an invalid key do not add charges, and you can retry after each configuration change without concern for cost. Mainstream model groups are on average about 30 percent below official list prices, with no platform fee, so once your key resolves, billing applies only to successful calls. Live per-model rates are published at https://relayrouter.io/models. If you continue to see 401 after verifying the key, header and base URL, regenerate the key at the dashboard and repeat the test request.

FAQ

Does a 401 error get billed? No. Failed or errored requests are generally not billed, so 401 responses do not incur charges.

Do I need a separate key for the OpenAI and Anthropic protocols? No. RelayRouter is compatible with both the OpenAI and Anthropic protocols, and the same account key works for both.

What code changes are needed to migrate without a 401? Keep your existing SDK, change base_url and the key, no other code changes.