[BUG] "Stale 'conversation open elsewhere' warning on reopen, even with no other session attached"

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?

Every time I reopen a Claude Code conversation in the VS Code extension, I get a 'This conversation is still open somewhere else' warning, even though no other window/device/session has it open. Confirmed via the extension itself that no other session is attached. This occurs even after restarting.

What Should Happen?

Reopening a conversation that isn't actually open in any other session/window/device should not show the 'still open somewhere else' warning. The warning should only appear when another session is genuinely attached.

Error Messages/Logs

Steps to Reproduce

Open a conversation in the Claude Code VS Code extension.
Close the chat panel/window (without force-killing VS Code).
Reopen the same conversation.
Warning appears: "This conversation is still open somewhere else. Using it in two places at once can mix up its messages."
Confirmed no other session is actually attached — no other VS Code window, device, or Claude Code session has this conversation open.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.296 (anthropic.claude-code)

Platform

Other

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_