Claude Code OAuth Reconnection Fails After Successful Auth — MCP Streamable-HTTP Transport Bug

What this error means

Authentication successful, but server reconnection failed is a Claude Code failure pattern reported for developers trying to fix mcp server reconnection failure after oauth authentication succeeds in claude code using streamable-http transport. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Found on GitHub anthropics/claude-code#10250 (browser CDP fetch). OAuth auth passes green but subsequent MCP server reconnection fails, requiring full Claude Code restart. Also corroborated by codersera.com 2026 troubleshooting guide covering Claude Code 529/401/MCP errors. Category maps to AI Coding Tools per approved list. High commercial value: blocks paid developers from using Claude Code mid-session.

Common causes

• Found on GitHub anthropics/claude-code#10250 (browser CDP fetch). OAuth auth passes green but subsequent MCP server reconnection fails, requiring full Claude Code restart. Also corroborated by codersera.com 2026 troubleshooting guide covering Claude Code 529/401/MCP errors. Category maps to AI Coding Tools per approved list. High commercial value: blocks paid developers from using Claude Code mid-session.

Quick fixes

1. Confirm the exact error signature matches Authentication successful, but server reconnection failed.
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/10250
• https://codersera.com/blog/claude-code-common-errors-troubleshooting-2026/
• https://www.truefoundry.com/blog/mcp-authentication-in-claude-code

Evidence note: Found on GitHub anthropics/claude-code#10250 (browser CDP fetch). OAuth auth passes green but subsequent MCP server reconnection fails, requiring full Claude Code restart. Also corroborated by codersera.com 2026 troubleshooting guide covering Claude Code 529/401/MCP errors. Category maps to AI Coding Tools per approved list. High commercial value: blocks paid developers from using Claude Code mid-session.

Related errors

• AI Coding Tools

FAQ

What should I check first?

Start with the exact Authentication successful, but server reconnection failed 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 Authentication successful, but server reconnection failed.