[BUG] Cowork: folders attached in Project → Context are not mounted in new chat sessions

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?

Same bug, but the documented workaround does NOT fix it for me.

Setup: Cowork project with Production_server and Sandbox_server folders added
in Project → Context. Folders show as attached in the Context panel.

What happens: new chat sessions in this project do not mount these folders at
all — only the project's docs/knowledge (files, memory.md) come through, no
filesystem access to the attached folders.

Tried, none worked:

1. Full app restart (Cmd+Q, not just closing the window)
2. Confirmed app is on the latest version (Check for Updates)
3. Removed and re-added both folders in Project → Context
4. The "send a message first, then mount" workaround from #76183 — mount

control still doesn't pick up the folders after sending a message

Only workaround that works: staying in an already-active session from before
this started, where the folders happened to mount correctly. Any brand new
session in this project is broken.

Would appreciate this being looked at separately if it's not exactly the same
root cause as #76183, since the standard workaround here doesn't apply.

What Should Happen?

Folders attached to a Cowork project via Project → Context should automatically mount in every new chat session started within that project, without requiring manual reattachment or the "send a message first, then attach" workaround.

Error Messages/Logs

No error is shown in the UI — the session silently proceeds without access to the attached folders. Asking Claude to list its mounted paths in a broken session returns only: outputs, uploads, .claude/projects, .claude/skills, .projects/<project-name> — the folders attached in Context (Production_server, Sandbox_server) are simply absent from the mount table.

Steps to Reproduce

1. Create a Cowork project and add one or more local/iCloud folders under Project → Context.
2. Start a brand new chat session inside that project.
3. Ask Claude to check which folders/paths are accessible in the session.
4. Observe: only the project's docs/knowledge (files, memory.md) are present — the folders attached in Context are not mounted.
5. Try the following, none of which restore the mount for new sessions in this project:

• Full app restart (Cmd+Q, not just closing the window)
• Confirming the app is on the latest version
• Removing and re-adding the folders in Project → Context
• Sending a placeholder message first, then attaching the folder (workaround from #76183)

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude 1.22209.0 (77c938)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_