Qutebrowser is no longer able to load a session with more than a couple hundred tabs after an update from version 3.6.3 to 3.7.0

Version info: qutebrowser v3.7.0 Git commit: Backend: QtWebEngine 6.11.1 based on Chromium 140.0.7339.225 with security patches up to 148.0.7778.96 (plus any distribution patches) (source: api) Qt: 6.11.1

CPython: 3.14.6 PyQt: 6.11.0

Qt wrapper info: PyQt6: success PyQt5: not imported -> selected: PyQt6 (via autoselect)

colorama: 0.4.6 jinja2: 3.1.6 pygments: 2.19.2 yaml: 6.0.3 adblock: 0.6.0 objc: no PyQt6.QtWebEngineCore: 6.11.0 PyQt6.sip: 6.15.2 pdf.js: 4.5.136 (/usr/share/pdf.js/build/pdf.mjs) sqlite: 3.53.3 QtNetwork SSL: OpenSSL 3.5.7 9 Jun 2026

WebExtensions: chromium-pdf (mhjfbmdgcfjbbpaeojofohoefgiehjai) [x] enabled [x] loaded [ ] installed /usr/share/qt6/resources/pdf

Google Hangouts (nkeimhogjdpnpccoofpliimaahmaaome) [x] enabled [x] loaded [ ] installed /usr/share/qt6/resources/hangout_services

Style: QFusionStyle Qt Platform: xcb (dwm) OpenGL: AMD, 4.6 (Compatibility Profile) Mesa 26.1.6 Platform: Linux-6.18.6-gentoo-gentoo-dist-x86_64-12th_Gen_Intel-R-_Core-TM-_i3-12100F-with-glibc2.43, 64bit Linux distribution: 'Gentoo Linux' (unknown) Frozen: False Imported from /usr/lib/python3.14/site-packages/qutebrowser Using Python from /usr/bin/python3.14 Qt library executable path: /usr/lib64/qt6/libexec, data path: /usr/share/qt6 OS Version:

--- /etc/os-release --- NAME='Gentoo' ID='gentoo' PRETTY_NAME='Gentoo Linux' VERSION='2.18' VERSION_ID='2.18'

--- /etc/gentoo-release --- Gentoo Base System release 2.18

--- /etc/lsb-release --- DISTRIB_ID="Gentoo"

Paths: cache: /home/rado/.cache/qutebrowser config: /home/rado/.config/qutebrowser data: /home/rado/.local/share/qutebrowser runtime: /run/user/1000/qutebrowser system data: /usr/share/qutebrowser

Autoconfig loaded: yes Config.py: no config.py was loaded Uptime: 1:03:52

Does the bug happen if you start with --temp-basedir?: I tried to create a temporary session in temp-basedir, but when I started to duplicate tabs a lot and got over 100, the browser just crashed with no warning. I haven't been able to verify if the bug still happens in temp-basedir sessions.

Description Today I updated my browser version from 6.3.6 to 6.7.0 and my Qtwebengine version from 6.10.2 to 6.11.1 and I am no longer able to load my main browsing session (500+ tabs). It worked perfectly fine before and I never had any issues, but now I am not even able to load it. When I try, the browser freezes entirely and it takes more than 10 minutes to receive another frame again. In this situation the browser either crashes or waits until all the tabs' renderer processes have been killed by the OOM killer, so eventually I am left with a field of errors. I tried enabling lazy restore, but that did nothing. I'll be really thankful if you can tell me how I can potentially fix this problem.

How to reproduce

1. Load a browser session with lots of tabs.
2. Notice the browser freeze.
3. Wait for the tabs to get killed and die.