[BUG] 403 "Request not allowed" when creating new Cowork chat (existing chats work fine)

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?

Creating a new Cowork chat in the Claude Code desktop app (macOS) immediately fails
with a 403 error: "Request not allowed". This happens every time a new session is
started. Existing/older Cowork chats open and work fine — only new ones fail.

When trying to start a new Cowork chat in the Claude Code desktop app (macOS),
I get the following error:

Failed to authenticate. API Error: 403 {"error":{"type":"forbidden","message":"Request not allowed"}}

Existing/old Cowork chats continue to work normally. Only creating new sessions fails.

Steps to reproduce

1. Open Claude Code desktop app (macOS)
2. Go to the Cowork tab
3. Try to start a new Cowork chat
4. Error appears immediately

What Should Happen?

A new Cowork session should be created successfully.

What I tried

• Updated Claude Code CLI to 2.1.105
• Logged out of all devices and logged back in
• Issue persists after re-authentication

Environment

• OS: macOS Version 15.7.4
• Claude desktop app
• Account: Claude Pro

Error Messages/Logs

Failed to authenticate. API Error: 403 {"error":{"type":"forbidden","message":"Request not allowed"}}

Steps to Reproduce

1. Open Claude Code desktop app (macOS)
2. Navigate to the Cowork tab
3. Click to start a new Cowork chat
4. Error appears immediately:

"Failed to authenticate. API Error: 403 {"error":{"type":"forbidden","message":"Request not allowed"}}"

Note: Existing Cowork chats (created previously) open and work fine.

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.105 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_