OpenRouter API 401 AuthenticationError — Valid Key but Authentication Fails

What this error means

AuthenticationError [HTTP 401] - API call failed despite valid API key and available credits is a OpenRouter failure pattern reported for developers trying to fix openrouter api returning 401 error even when api key is valid and has credits. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Multiple GitHub issues report OpenRouter returning 401 AuthenticationError despite verified valid API keys with credits. Affected tools include hermes-agent, Cline, Aider, and Home Assistant. One user reported creating a dozen API keys without resolution, with errors randomly alternating between 401 and ‘Provider returned error’.

Common causes

• OpenRouter is a paid AI model aggregation service. When 401 errors occur despite valid keys, developers cannot use any downstream tools (Cline, Aider, Home Assistant, OpenClaw) that depend on OpenRouter. The intermittent nature (alternating between 401 and working) makes it especially frustrating.
• Multiple GitHub issues report OpenRouter returning 401 AuthenticationError despite verified valid API keys with credits. Affected tools include hermes-agent, Cline, Aider, and Home Assistant. One user reported creating a dozen API keys without resolution, with errors randomly alternating between 401 and ‘Provider returned error’.

Quick fixes

1. Confirm the exact error signature matches AuthenticationError [HTTP 401] - API call failed despite valid API key and available credits.
2. Check the OpenRouter account, local tool state, and provider configuration involved in the failing workflow.
3. Verify the account session, API key, provider settings, and environment where the failing tool is running.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/NousResearch/hermes-agent/issues/14637
• https://github.com/cline/cline/issues/813
• https://github.com/Aider-AI/aider/issues/853

Evidence note: Multiple GitHub issues report OpenRouter returning 401 AuthenticationError despite verified valid API keys with credits. Affected tools include hermes-agent, Cline, Aider, and Home Assistant. One user reported creating a dozen API keys without resolution, with errors randomly alternating between 401 and ‘Provider returned error’.

Related errors

• OpenRouter 429 rate limit exceeded
• OpenRouter insufficient credits quota exceeded
• OpenRouter model not available error

FAQ

What should I check first?

Start with the exact AuthenticationError [HTTP 401] - API call failed despite valid API key and available credits text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed OpenRouter workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without AuthenticationError [HTTP 401] - API call failed despite valid API key and available credits.