[DOCS] MCP OAuth docs missing manual callback URL paste fallback for localhost redirect failures

Documentation Type

Missing documentation (feature not documented)

Documentation Location

https://code.claude.com/docs/en/mcp

Section/Topic

"Authenticate with remote MCP servers" OAuth troubleshooting flow.

Current Documentation

Current OAuth guidance says:

"Then follow the steps in your browser to login."

And tips include:

"If your browser doesn't open automatically, copy the provided URL"

It does not document what to do when the localhost redirect callback itself fails.

What's Wrong or Missing?

Release v2.1.63 added this fallback behavior:

"Added manual URL paste fallback during MCP OAuth authentication. If the automatic localhost redirect doesn't work, you can paste the callback URL to complete authentication."

The docs currently cover browser-launch issues but not redirect callback failure recovery, which is a separate failure mode.

Suggested Improvement

Add a troubleshooting subsection in MCP OAuth docs:

• Detecting localhost redirect callback failure
• How to copy/paste the callback URL manually to complete auth
• Any requirements/format constraints for the callback URL
• How this interacts with --callback-port / MCP_OAUTH_CALLBACK_PORT

Impact

High - Prevents users from using a feature

Additional Context

Affected Pages:

| Page | Context |
|------|---------|
| https://code.claude.com/docs/en/mcp | Primary OAuth flow docs for Claude Code MCP servers |
| https://code.claude.com/docs/en/settings | MCP_OAUTH_CALLBACK_PORT env var reference should cross-link callback fallback guidance |
| https://platform.claude.com/docs/en/agent-sdk/mcp | Agent SDK cross-reference for OAuth callback handling context |

Total scope: 3 pages affected

Related open issue (behavior context): https://github.com/anthropics/claude-code/issues/16006

Source: Claude Code release v2.1.63
Changelog entry: "Added manual URL paste fallback during MCP OAuth authentication. If the automatic localhost redirect doesn't work, you can paste the callback URL to complete authentication."