1998881 - Closing the “Compose Message” window temporarily freezes the app behind it on macOS 26

Status: UNCONFIRMED

(Thunderbird :: Message Compose Window, defect)

Description

[Victor]

Steps to reproduce:

Open a “Compose Message” window (e.g., by clicking a mailto: link or using an email-related extension).

Close the “Compose Message” window.

Immediately try to interact with the app behind Firefox (for example, Finder, Mail, Chrome, or another browser window).

Actual results:

The app behind remains frozen or unresponsive for several seconds after the compose window is closed.
Environment: macOS 26.1

Expected results:

The background app should remain responsive immediately after the compose window is closed.

Comment 1

[meso]

Similar if not the same issue here.

1. After clicking the red close button Thunderbird often (but not always) freezes for around 10 seconds. In that time I'm unable to interact with the desktop or any other app until TB finishes whatever it's doing and unfreezes.
2. The same bug appears after clicking Reply on any email and adding a few lines in the new window. After pressing the Discard button TB momentarily freezes. During that time I can't open or even highlight other emails in the Inbox.

I've tried 1) quitting TB and 2) restarting my computer but that didn't help. This long lag/freeze started happening after I upgraded to Mac OS X 26.2 from 25.7 a few days ago.

Thunderbird 146.0

Comment 2

[Wayne Mery (:wsmwk)]

Please test the list at https://wiki.mozilla.org/Thunderbird:Testing:Memory_Usage_Problems