[BUG] [Cowork] [#67330] "Add files" during project creation silently copies files to project folder

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?

When adding files during Cowork project creation, the files are physically copied into the new project folder on disk. The UI presents "Add files" as a way to give Claude context — there is no indication that the files will be duplicated or that copies will be written anywhere.

What Should Happen?

Expected behaviour

The file is referenced as read context for Claude. The original file is untouched and no copy is created. If copying is intentional (e.g. to create a portable project bundle), the destination path and copy behaviour are disclosed before the user confirms creation.

Actual behaviour

A copy of the file is written into the project folder on disk. Given that project folder location can itself be unpredictable (see related issue), the user may not know where the copy has been created.

Example: A file added from C:\Users\CarolineDunn\Desktop\start.png was copied into C:\Users\CarolineDunn\Documents\Claude\Projects\abc\start.png with no disclosure that this would happen.

Error Messages/Logs

Steps to Reproduce

Steps to reproduce

1. Create a new project: + New project → Start from scratch
2. Enter a project name
3. Add a file using the Add files field (e.g. a screenshot from the Desktop)
4. Hit Create
5. Navigate to the newly created project folder on disk

Claude Model

Not sure / Multiple models

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude Desktop v2.1.170.

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Additional context

This compounds the folder location issue: a user who adds a working file as context may not realise they now have a duplicate of that file in a different location, potentially diverging if they continue editing the original.

The "Add files" label and drop zone UI pattern is consistent with "attach for context" interactions across other tools (chat interfaces, email). The copy-to-disk behaviour is not consistent with that expectation and is not surfaced in the UI at any point.

Related issue: Project folder created at wrong location (context folder used as parent) - #67330