Fix OAuth 2.1 connection failure for custom MCP servers in Claude Code; resolve infinite restart loop during authentication flow Includes evidence for Claude Code troubleshooting demand.
Source-backedLast updated May 23, 20263 sourcesNeeds local verification
Custom MCP server with OAuth 2.1 authentication fails to connect in Claude Code/Claude Desktop — OAuth flow opens about:blank page and creates infinite restart loop instead of initiating auth prompt
Quick fix
Verify the account session, API key, provider settings, and environment where the failing tool is running.
Updated
Verification status
Source-backed
Evidence
3 public source URLs
Before you change production
This page includes public source URLs in the imported troubleshooting record. Compare those references with your version and environment before applying changes.
Reproduce the smallest failing action and save non-secret logs before changing configuration.
Check versions for Claude Code, related SDKs, package managers, CI runners, and hosting providers.
Change one setting or dependency at a time, then rerun the same failing command or request.
Avoid destructive commands, credential rotation, billing changes, or security relaxations without a rollback plan.
What this error means
Custom MCP server with OAuth 2.1 authentication fails to connect in Claude Code/Claude Desktop — OAuth flow opens about:blank page and creates infinite restart loop instead of initiating auth prompt is a Claude Code failure pattern reported for developers trying to fix oauth 2.1 connection failure for custom mcp servers in claude code; resolve infinite restart loop during authentication flow. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.
Why this happens
anthropics/claude-code#11814 details spec-compliant OAuth 2.1 MCP servers failing in both Claude Desktop and claude.ai web interface while working perfectly via CLI --transport http. The about:blank + infinite loop bug blocks enterprise MCP integrations entirely.
Common causes
anthropics/claude-code#11814 details spec-compliant OAuth 2.1 MCP servers failing in both Claude Desktop and claude.ai web interface while working perfectly via CLI --transport http. The about:blank + infinite loop bug blocks enterprise MCP integrations entirely.
Quick fixes
Confirm the exact error signature matches Custom MCP server with OAuth 2.1 authentication fails to connect in Claude Code/Claude Desktop — OAuth flow opens about:blank page and creates infinite restart loop instead of initiating auth prompt.
Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
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
Capture the exact error message and the command, editor action, or request that triggered it.
Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
Review the source evidence below and compare it with your environment.
Apply one change at a time and rerun the smallest failing action.
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.
Diagnostic flow for this page
Match Custom MCP server with OAuth 2.1 authentication fails to connect in Claude Code/Claude Desktop — OAuth flow opens about:blank page and creates infinite restart loop instead of initiating auth prompt exactly before applying the quick fix.
Compare the failing environment with Claude Code versions, account scope, provider settings, and deployment context.
Check the listed common causes in order, starting with the cause that best matches your logs.
Use the evidence status below to decide whether to confirm against public sources or official documentation.
Apply one reversible change, rerun the smallest failing action, and keep rollback notes.