Invisible “New Tab” process is created when dragging a tab between windows, and it prevents Catsxp from exiting

[ryo-fujinone]

Catsxp: 5.12.5
Kernel: 143.0.7499.174

There is a bug where an extra “New Tab” process is created in the background, but it does not appear as an actual tab in the UI.

I can reproduce this on a fresh portable build (portable_x64_release_143_5_12_5.zip) after extracting it to a new folder, so I believe this is not caused by my profile or extensions.

# Steps to reproduce
1. Left-click and drag a tab to detach it into its own window.
(At this point, the invisible “New Tab” process does not appear.)
2. Drop the tab into another Catsxp window (it can be the original window).
(At the moment the tab is dropped/moved into the other window, an extra “New Tab” process is created in the background.)

# Result / impact
After this bug happens, even if I close all visible Catsxp windows, the invisible “New Tab” process does not exit, and Catsxp remains running in the background.
As a result, Catsxp cannot be fully closed normally. To fully exit Catsxp, I have to open Windows Task Manager and manually terminate all Catsxp processes. This behavior is clearly incorrect and seems like a leak of a hidden window/tab/process.

[catsxp]

6.1.1 beta-18 fixed!