[BUG] Cowork (macOS): composer fails silently (Send reverts / Submit disabled) when session start fails auth — no error surfaced.

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

On the macOS desktop app, attaching a local folder as Cowork context adds the folder chip to the composer but the Send button then silently stops working — clicking it flickers as if sending, reverts, and nothing posts. No error is shown. The session is unrecoverable because there is currently no way to remove an attached folder (#40043); the only escape is starting a new session without the folder.

What Should Happen?

Expected Behavior

Either the message sends, or a clear error explains why the folder attachment could not complete.

Actual Behavior

• Send button appears live (orange/enabled); clicking it briefly "resolves" then reverts to the pre-send state.
• No error surfaced; the message simply never posts.
• No in-session recovery: per #40043 there is no way to detach the folder, so the composer stays stuck.

Error Messages/Logs

None.

Steps to Reproduce

1. Start a Cowork session on macOS desktop.
2. Attach a local folder as context via the folder-plus button — in my case a folder on a secondary/external volume (/Volumes/…).
3. The folder chip appears in the composer.
4. Type a message and click Send.

Claude Model

Other

Is this a regression?

Yes, this worked in a previous version

Last Working Version

prior release before 1.20186.1

Claude Code Version

1.20186.1 Claude Cowork

Platform

Other

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Notes

• Same machine and folder setup worked for months; this reads as a recent regression.
• Possibly related to #10662 (attaching context disabling Send, web) and the high-context variant in #18676.
• Possibly related to #51666 (folder-add failure on macOS, though that one surfaces an explicit error rather than failing silently).

Additional observation (possibly unrelated)

When a folder chip is showing, a device-info query from the session side reports connectedFolders as empty, i.e. the folder grant does not appear to complete on the bridge. I want to be clear this is not established as the cause of the Send failure — in one instance a message did send successfully while connectedFolders was still empty — but I'm noting it in case it helps triage.

Environment

• macOS (Apple Silicon)
• Claude desktop app 1.20186.1
• Electron 42.5.1, Node 24.17.0
• Folder located on a secondary/external volume (/Volumes/…)

Reports I reviewed that do NOT appear to be the same issue:

• #18676 — Windows, high-context / auto-compact silent send failure. Different OS and trigger (context pressure, not folder attachment).
• #10662 — Web app; Send disabled after attaching a GitHub repo. Closed; not the desktop local-folder case.
• #44710 — macOS; symlinks to cloud storage resolving into ~/Library are blocked. Folder fails to attach at all.
• #25797 — request_cowork_directory tool missing; folder picker can't be triggered. Cannot mount a folder in the first place.
• #51666 — macOS; folder-add fails with an explicit error ("Session VM process not available" / "source path is not accessible"). Surfaces an error rather than the silent Send failure seen here.