[BUG] Cowork: present_files creates local-to-Drive desync — agent reads stale local copy after user edits on Drive

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?

Context: Cowork mode (Claude desktop app, research preview). Using present_files to deliver an .xlsx file to the user.

What happened:

1. Agent creates an .xlsx file locally and calls present_files to deliver it
2. 2. present_files uploads the file to Google Drive and shows the user an interactive card
3. 3. User opens the file on Google Drive (the natural action after seeing it there), edits cells, and saves
4. 4. Agent subsequently reads the file back using the Read tool or bash — but reads the local filesystem copy, not the Drive version
5. 5. Agent reports "no corrections found" despite user's edits being clearly visible on Drive

Root cause: After present_files uploads to Drive, the agent's file tools still point to the local copy. There is no sync-back mechanism, so edits made on Drive are invisible to the agent.

Impact: User and agent are working on different versions of the same file without knowing it. The agent confidently reports stale data. In our case, the user had filled in a review column on 17 rows in a 149-row spreadsheet, and the agent saw zero changes.

What Should Happen?

One of the following:

1. Sync-back: After present_files uploads to Drive, subsequent Read / bash calls for that file should pull from the Drive version (or at least detect it changed and re-download)
2. 2. Read from synced source: The conversation context already included a <sync_sources> document with the Google Sheet content. The agent should prefer this over the local file when checking for edits.
3. 3. UX clarity: If sync-back isn't feasible, make it clear to the user (and the agent) that the file card is view-only on Drive and edits should be made via the sidebar preview or by re-uploading the file.

Error Messages/Logs

Steps to Reproduce

1. In Cowork mode, have the agent create any file (e.g., an .xlsx spreadsheet) and deliver it via present_files
2. 2. The file card appears in chat. Open it — it opens on Google Drive.
3. 3. Edit the file on Google Drive (e.g., change a cell value) and save.
4. 4. Back in Cowork, ask the agent to "check out my corrections" or "read the file back"
5. 5. The agent reads the local copy via Read tool or bash, sees the original unedited version, and reports no changes.

Note: The conversation context does include the Drive content via <sync_sources>, but the agent's default behavior is to read via filesystem tools, which hit the stale local copy.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Cowork mode (Claude desktop app, research preview) — May 22, 2026

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

This bug report was filed by Claude (Cowork mode) on behalf of the user, during a live session where the desync was encountered.