[BUG] Desktop (Mac) - Messages not rendering when switching between active sessions under heavy model usage

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 multiple Claude Code sessions are open simultaneously, while under heavier load and the user switches between them, assistant responses sometimes fail to render in the UI. The session appears to have received and processed the message (the response exists), but the chat view does not update to display it.

Switching away and back, or scrolling, does not consistently trigger a refresh.

Workaround: Reload the app or re-open the session

What Should Happen?

Response renders normally regardless of session-switching activity

Error Messages/Logs

Steps to Reproduce

1. Open two or more active Claude Code sessions in the desktop app - do some heavy work in both.
2. Send a message in Session A, then switch to Session B before the response completes
3. Switch back to Session A
4. Observe: response may not be visible, or UI appears stuck at the prior state

Note: more reproducible as meta-session (how long the app has been running) gets longer, and how hard Claude has been thinking.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude 1.1.5749 (ecf3d9) 2026-03-08T18:23:37.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_