[BUG] Claude in Chrome extension OAuth fails with "Redirect URI chrome-extension:// is not supported by client" - Cowork desktop app

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?

Description
The Claude in Chrome browser extension fails to authorise when used via the Cowork desktop app. The error appears immediately after clicking Authorise.

Environment

• App: Claude Cowork (desktop)
• Browser: Chrome (latest)
• OS: macOS
• Extension: Claude (official Anthropic, fcoeoabgfenejglbffodgkkbkcdhcgfn)

That gives Anthropic everything they need to investigate. You can also reference issues #17786 and #17790 in your report since this looks like the same root cause.

What Should Happen?

Expected behaviour
After completing Google OAuth, the extension should successfully authorise and connect to the Cowork desktop app. The Claude in Chrome side panel should open and show a "Connected" state, allowing Claude to read and interact with browser tabs on the user's behalf.
Instead, OAuth completes but the redirect back to the extension fails immediately with the "not supported by client" error, leaving the extension in a permanently disconnected state. Reinstalling the extension does not resolve this — the same error appears on every fresh authorisation attempt.

Error Messages/Logs

**Error message**
"Authorization failed / Redirect URI chrome-extension:/fcoeoabgfenejglbffodgkkbkcdhcgfn/oauth_callback.html is not supported by client"

Steps to Reproduce

Steps to reproduce

1. Open Cowork desktop app
2. Install Claude in Chrome extension from Chrome Web Store
3. Click Authorise in the extension
4. Google OAuth completes successfully
5. Redirected back to extension — Authorization failed error shown immediately

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.63.

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Additional context

• Removing and reinstalling the extension does not fix it
• The extension times out entirely when Claude in Chrome tools attempt to connect (60s timeout)
• The extension ID in the error matches the official Anthropic Claude extension: fcoeoabgfenejglbffodgkkbkcdhcgfn
• This appears related to #17786 (oauth_callback.html missing) and #17790
• User is logged into the same Google account in both Chrome and Cowork