Claude Code HTTP 401 OAuth Token Expired Mid-Session

What this error means

HTTP 401 authentication_error mid-session — OAuth token expired or revoked, every subsequent tool call returns authentication_error is a Claude Code failure pattern reported for developers trying to fix claude code 401 auth failure caused by expired oauth token without re-login. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Documented in Codersera Claude Code error guide — 401 auth failure occurs when OAuth token expires or is revoked, especially painful during autonomous runs. Fix: /logout then /login to refresh credentials. Truefoundry MCP auth guide confirms OAuth expiry patterns. Strong commercial impact.

Common causes

• Documented in Codersera Claude Code error guide — 401 auth failure occurs when OAuth token expires or is revoked, especially painful during autonomous runs. Fix: /logout then /login to refresh credentials. Truefoundry MCP auth guide confirms OAuth expiry patterns. Strong commercial impact.

Quick fixes

1. Confirm the exact error signature matches HTTP 401 authentication_error mid-session — OAuth token expired or revoked, every subsequent tool call returns authentication_error.
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://codersera.com/blog/claude-code-common-errors-troubleshooting-2026/
• https://www.truefoundry.com/blog/mcp-authentication-in-claude-code

Evidence note: Documented in Codersera Claude Code error guide — 401 auth failure occurs when OAuth token expires or is revoked, especially painful during autonomous runs. Fix: /logout then /login to refresh credentials. Truefoundry MCP auth guide confirms OAuth expiry patterns. Strong commercial impact.

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FAQ

What should I check first?

Start with the exact HTTP 401 authentication_error mid-session — OAuth token expired or revoked, every subsequent tool call returns authentication_error 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 HTTP 401 authentication_error mid-session — OAuth token expired or revoked, every subsequent tool call returns authentication_error.