Claude Code / AI Coding Tools

Claude Desktop/Web infinite about:blank loop when connecting to OAuth-protected custom MCP servers

Fix Claude Desktop and claude.ai web interface failing to initiate OAuth flow for custom MCP servers — browser stays on about:blank creating infinite reconnect loop, while Claude Code CLI works fine Includes evidence for Claude Code troubleshooting demand.

Source-backed Last updated May 18, 2026 1 source Needs local verification

Category: AI Coding Tools
Error signature: Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName]
Quick fix: Verify the account session, API key, provider settings, and environment where the failing tool is running.
Updated: May 18, 2026
Verification status: Source-backed
Evidence: 1 public source URL

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

Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName] is a Claude Code failure pattern reported for developers trying to fix claude desktop and claude.ai web interface failing to initiate oauth flow for custom mcp servers — browser stays on about:blank creating infinite reconnect loop, while claude code cli works fine. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub Issue #11814 on anthropics/claude-code: Custom spec-compliant FastAPI MCP server with OAuth 2.1 (RFC 8414, RFC 9728, RFC 7636) returns correct discovery metadata but Claude Desktop/Web never send requests. about:blank loop vs Claude Code CLI --transport http working perfectly. Closed as duplicate of #5826. Categorized as AI Coding Tools per SKILL.md mapping for Claude Code OAuth/MCP auth errors.

Common causes

GitHub Issue #11814 on anthropics/claude-code: Custom spec-compliant FastAPI MCP server with OAuth 2.1 (RFC 8414, RFC 9728, RFC 7636) returns correct discovery metadata but Claude Desktop/Web never send requests. about:blank loop vs Claude Code CLI --transport http working perfectly. Closed as duplicate of #5826. Categorized as AI Coding Tools per SKILL.md mapping for Claude Code OAuth/MCP auth errors.

Quick fixes

Confirm the exact error signature matches Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName].
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 Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName] 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.

FAQ

What does Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName] mean in Claude Code?

Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName] indicates the workflow described by "Claude Desktop/Web infinite about:blank loop when connecting to OAuth-protected custom MCP servers" failed in a AI Coding Tools context. Start by confirming the exact signature and the component that emitted it.

What should I check first for Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName]?

Check whether this cause matches your environment: GitHub Issue #11814 on anthropics/claude-code: Custom spec-compliant FastAPI MCP server with OAuth 2.1 (RFC 8414, RFC 9728, RFC 7636) returns correct discovery metadata but Claude Desktop/Web never send requests. about:blank loop vs Claude Code CLI --transport http working perfectly. Closed as duplicate of #5826. Categorized as AI Coding Tools per SKILL.md mapping for Claude Code OAuth/MCP auth errors.

Is the Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName] guidance source-backed?

The "Claude Desktop/Web infinite about:blank loop when connecting to OAuth-protected custom MCP servers" page is labeled source-backed. It has 1 public source URL from github.com, so use that evidence status when deciding how much additional verification you need.

When should I avoid the quick fix for Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName]?

For "Claude Desktop/Web infinite about:blank loop when connecting to OAuth-protected custom MCP servers", avoid applying "Verify the account session, API key, provider settings, and environment where the failing tool is running." when the error text differs, the affected version or provider is different, or the change would touch credentials, billing, DNS, production deploy settings, or irreversible data.

What should I collect before debugging Browser opens to about:blank; 'Open Claude?' dialog appears immediately; There was an error connecting to [ServerName]?

For "Claude Desktop/Web infinite about:blank loop when connecting to OAuth-protected custom MCP servers", collect the failing Claude Code command or request, non-secret configuration, versions, timestamps, request IDs when available, and the smallest reproduction that still triggers the signature.