[BUG] Sessions not refreshing state on return — response shown as delivered but missing from UI

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 I switch away from an active session to another session,
and then return to it, the session UI appears idle with no
processing indicator. The response is not visible in the
conversation. If I ask what happened, Claude replies that it
already delivered the answer — but the response text is absent
from the UI.

What Should Happen?

When returning to a session that was processing in the background,
the response should be visible, or at least a status indicator
should show that the session completed or is still working.

Error Messages/Logs

Steps to Reproduce

1. Start a session and send a prompt that takes time to process
2. Switch to a different session while it's running
3. Return to the original session
4. Observe: no response is shown, no loading indicator
5. Send a follow-up message asking about the result
6. Claude replies it already answered — but no answer is visible

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.1.4173 (12766c)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_