[BUG] Cowork (Windows 11): drag-and-drop files are not uploaded to the session uploads 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?

What's Wrong?

On Claude Desktop for Windows 11, files attached to a Cowork chat via drag-and-drop are not transferred to the session's uploads folder (i.e. the per-session working directory that Cowork normally exposes to Claude, such as /mnt/user-data/uploads).

The file appears to be attached in the chat UI as expected, but when Claude attempts to read it from the uploads folder, the file is not present. As a result, Claude cannot access the contents of the dropped file at all during that session.

By contrast, attaching the same file through the + / paperclip button (the standard file picker) works correctly — the file ends up in the uploads folder and Claude can read it normally. This makes the issue specific to the drag-and-drop ingestion path.

What Should Happen?

Expected Behavior

The dragged-and-dropped file should be placed in the session's uploads folder, identical to the behavior when the same file is attached via the file picker button. Claude should be able to list and read the file.

Actual Behavior

The uploads folder does not contain the dropped file. Claude reports that no such file exists in the session workspace, even though the attachment is visible in the chat UI.

Workaround: re-attach the file using the file picker button instead of drag-and-drop.

Error Messages/Logs

Steps to Reproduce

1. On Windows 11, open Claude Desktop and start a new Cowork chat.
2. Drag a file (e.g. test.txt) from File Explorer and drop it onto the Cowork chat input area.
3. Confirm that the file appears as an attachment in the message composer.
4. Send a message such as: "List the files in the uploads folder and show me the contents of test.txt."
5. Observe Claude's tool output.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

-

Claude Code Version

-

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

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

Note: This is a Claude Cowork (Claude Desktop) bug, not a Claude Code bug. Filing here as the only available channel for Cowork issues (per precedent in #54011, #58536, and others).

Environment

| Field | Value |
| --- | --- |
| OS | Windows 11 |
| Client | Claude Desktop (Cowork) |
| Reproduction | Consistent, every drag-and-drop attempt |
| Regression | Unsure whether this worked in a previous version |

Additional Notes

It would be ideal if the drag-and-drop and file-picker paths shared the same upload pipeline, so that any file accepted by the UI is guaranteed to reach the session uploads folder.

Thank you for looking into this!