[BUG] Cowork: Conversation rollback/loss when switching to settings or menus

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 navigating away from an active Cowork conversation to access settings, menus, or other UI elements, then returning to the conversation window, the most recent messages systematically disappear. The conversation "rolls back" to an earlier state, losing the last few exchanges.
This is not a random or intermittent issue — it happens every time the user switches away from the conversation and comes back.

What Should Happen?

Actual behavior
The conversation rolls back to a previous state. Recent messages are lost. This is particularly disruptive when:

A present_files dialog was displayed (the file delivery dialog doesn't re-render correctly after rollback)
The assistant asked a question and the user needs to re-answer it
Multiple tool calls or actions were performed that are no longer visible

Impact

Context loss: user and assistant lose track of what was just discussed
Workflow disruption: file deliveries via present_files fail to display properly after rollback, requiring re-generation
Repeated work: the user has to re-explain or re-confirm actions that were already completed

Error Messages/Logs

Steps to Reproduce

1. Have an active Cowork conversation with several recent exchanges
2. Click on Settings, or navigate to any menu/panel outside the conversation
3. Return to the Cowork conversation window
4. Observe: the last messages (both user and assistant) have disappeared

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

Version 1.1.4498 (24f768)

Claude Code Version

Version 1.1.4498 (24f768)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

This appears related to but distinct from existing issues:

#19434 (Chats Disappearing)
#27339 (Forked conversations sometimes disappear when resuming)
#26805 (Responses not rendering until user types)

The key differentiator here is that it's systematic (100% reproducible) and specifically triggered by navigating to settings/menus, not by forking, resuming, or waiting.