[BUG]

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Title: HTTP MCP server with Authorization header fails on Windows after June 2 update (works on Mac)

Describe the bug

Since the Anthropic update on June 2 2026, an HTTP MCP server configured with a static headers.Authorization field no longer connects on Windows. The same config works fine on Mac (confirmed with a colleague on the same shared API key).

Claude Code shows: HTTP 401 — Server rejected the configured Authorization header. OAuth fallback is disabled when headers.Authorization is set.

The MCP server does not appear in the tools list at all.

Config (redacted)

"ReadMe": {
  "type": "http",
  "url": "https://docs.readme.com/mcp",
  "headers": {
    "Authorization": "Bearer rdme_xxxx"
  }
}

What's notable

Two other HTTP MCP servers in the same config file connect fine on the same machine:

• One uses type: "http" with no auth headers (Notion) — works
• One uses type: "http" with OAuth — works

ReadMe is the only server using headers.Authorization and it is the only one failing.

Steps to reproduce

1. Configure an HTTP MCP server with a static Authorization header in .claude.json
2. Start Claude Code on Windows
3. Server fails with 401; tools do not load

Environment

• OS: Windows 11 Enterprise
• Claude Code version: 2.1.161
• This config worked reliably for 6+ months before June 2 2026
• Colleague on Mac with identical config and same API token: no issue

What Should Happen?

Claude should connect to ReadMe via mcp server.

Error Messages/Logs

Steps to Reproduce

● 1. Add an HTTP MCP server to .claude.json with a static Authorization header (e.g. "Authorization": "Bearer rdme_xxxx") 2. Start Claude Code on Windows 11

1. Run /mcp to check server status
2. Server shows HTTP 401; tools do not appear in the tools list

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.161

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Two other HTTP MCP servers in the same .claude.json work fine on the same machine: one with no auth headers (Notion), one with OAuth (Slack). ReadMe is the only server using headers.Authorization and
the only one failing. A colleague on Mac with identical config and the same API token has no issue. This worked reliably for 6+ months before the June 2 update.