Claude Code 401 Auth Loop — All Commands Fail Including /login on Windows

What this error means

API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"Invalid authentication credentials"}} is a Claude Code failure pattern reported for developers trying to fix claude code 401 authentication error that blocks all commands including /login. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

User on Windows with active Claude Pro subscription (paid May 2026) reports all Claude Code commands return 401 Invalid authentication credentials. Tried /logout, /login, setup-token, deleted ~/.claude, reinstalled v2.1.141. Welcome screen shows correct account but API always returns 401.

Common causes

• Paid Pro subscribers hit a 401 auth loop where every command fails, including re-login. The welcome screen shows valid account but API requests are rejected. Devastating for productivity.
• User on Windows with active Claude Pro subscription (paid May 2026) reports all Claude Code commands return 401 Invalid authentication credentials. Tried /logout, /login, setup-token, deleted ~/.claude, reinstalled v2.1.141. Welcome screen shows correct account but API always returns 401.

Quick fixes

1. Confirm the exact error signature matches API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"Invalid authentication credentials"}}.
2. Check the Claude Code 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/anthropics/claude-code/issues/58926

Evidence note: User on Windows with active Claude Pro subscription (paid May 2026) reports all Claude Code commands return 401 Invalid authentication credentials. Tried /logout, /login, setup-token, deleted ~/.claude, reinstalled v2.1.141. Welcome screen shows correct account but API always returns 401.

Related errors

• Claude Code login fails
• Claude Code OAuth token expired
• Claude Code authentication_error invalid credentials

FAQ

What should I check first?

Start with the exact API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"Invalid authentication credentials"}} text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Claude Code 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 API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"Invalid authentication credentials"}}.