[BUG] Impossible to append folders via deeplink

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?

It's impossible to use claude:// deeplink to append folders to a new session.

What Should Happen?

I expect claude://cowork/new?file=<file_path> to behave similar to drag&drop.

Error Messages/Logs

Steps to Reproduce

1. Call claude://cowork/new?folder=123&folder=456

• Both folders 123 and 456 are attached to a new session

1. Call claude://cowork/new?folder=789

• 123 and 456 get discarded, 789 becomes the only attached folder

1. Call claude://cowork/new?folder=123&folder=456

• 789 gets discarded, 123 and 456 are attached to a new session

Screen recording:
https://cloud.box.com/s/snnfzjxx4347gzeelxkkz85qgh0yt4o8
(the link expires on September 13)

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.202

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_