[Desktop] K-Win frequently crashes when the PC starts up

[greenster]

For the past few days, K-Win has been crashing frequently when I start up my PC.

Unfortunately, I can’t send an error report.

That’s why I’m asking here.

[greenster]

KWin continues to crash every time I restart Kubuntu 26.04 LTS. The standard Kubuntu taskbar at the top of the desktop does not appear, but another taskbar at the bottom does appear as normal.

How can I fix this problem?

Would it be helpful for you to see the error code for the KWin crash? If so, what’s the best way for me to provide it?

[die.boer]

After a reboot where KWin crashed, run:

journalctl -b -1 | grep -Ei "kwin|plasmashell|drkonqi|segfault"

if it crashed during the current boot,run:

journalctl -b | grep -Ei "kwin|plasmashell|drkonqi|segfault"

paste the output

also check whether KWin is actually crashing

coredumpctl list | grep kwin

If you see entries, also run:

coredumpctl info

and paste the KWin section

[greenster]

One more thing: if Kubuntu starts up with errors like that, I log out and then log back in, and Kubuntu starts up normally again without any errors.

@die.boer I’ll get round to your tasks later today.

[die.boer]

One more thing: if Kubuntu starts up with errors like that, I log out and then log back in, and Kubuntu starts up normally again without any errors.

with that info ,please try disabling session restore.(if it is enabled)

Go to:

System Settings - Session - Desktop Session

and set: On login: Start with an empty session

[greenster]

with that info ,please try disabling session restore.(if it is enabled)

Go to:

System Settings - Session - Desktop Session

and set: On login: Start with an empty session

That’s exactly how it was already set up for me.

[greenster]

When the system shuts down, I can see that my Kubuntu is labelled ‘Development branch’.

Does that mean this is a developer version of Kubuntu and that errors might therefore occur?



I downloaded Kubuntu from here in February this year:

https://wiki.ubuntuusers.de/Downloads/Resolute_Raccoon/

[die.boer]

The official release of Ubuntu/Kubuntu 26.04 LTS wasn't available yet in February, so the ISO you installed was almost certainly a pre-release (daily build/beta). Those builds identify themselves as the development branch.

Even though you've kept it updated, some packages or branding may still reflect that development state, and pre-release installations can occasionally carry over bugs or configuration quirks.
That does not necessarily explain the KWin crashes,but it does increase the likelihood that you're encountering a Plasma or packaging bug that wouldn't affect someone who installed from the final release media.

please give outputs of these 2

cat /etc/os-release

apt policy base-files

...and the error codes from post #3 , if possiible

[greenster]

Here are the first two code snippets; I’ll do the ones from post 3 next.

PRETTY_NAME="Ubuntu 26.04 LTS"
NAME="Ubuntu"
VERSION_ID="26.04"
VERSION="26.04 LTS (Resolute Raccoon)"
VERSION_CODENAME=resolute
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=

base-files:
Installiert: 14ubuntu6.1
Installationskandidat: 14ubuntu6.1
Versionstabelle:
*** 14ubuntu6.1 500
500 http://archive.ubuntu.com/ubuntu resolute-updates/main amd64 Packages
100 /var/lib/dpkg/status
14ubuntu6 500
500 http://archive.ubuntu.com/ubuntu resolute/main amd64 Packages

[die.boer]

Your installation is on the released version of Ubuntu/Kubuntu 26.04 LTS , so you're not still running a development release.
The fact that the shutdown splash still says "development branch" is almost certainly just a cosmetic bug in the Plymouth theme or branding package. It isn't evidence that your entire OS is a development build.

[greenster]

First code from post 3

stephan@BlackSnake:~$ journalctl -b -1 | grep -Ei "kwin|plasmashell|drkonqi|segfault"
Aug 03 15:24:41 BlackSnake systemd[1751]: Started drkonqi-sentry-postman.path - Submitting pending crash events (file monitor).
Aug 03 15:24:41 BlackSnake systemd[1751]: Started drkonqi-coredump-cleanup.timer - Cleanup lingering KCrash metadata.
Aug 03 15:24:41 BlackSnake systemd[1751]: drkonqi-sentry-postman.timer - Submitting pending crash events skipped, unmet condition check ConditionPathExistsGlob=/home/stepha
n/.cache/drkonqi/sentry-envelopes/*
Aug 03 15:24:41 BlackSnake systemd[1751]: Listening on drkonqi-coredump-launcher.socket - Socket to launch DrKonqi for a systemd-coredump crash.
Aug 03 15:24:41 BlackSnake systemd[1751]: Started drkonqi-coredump-cleanup.service - Cleanup lingering KCrash metadata.
Aug 03 15:24:43 BlackSnake systemd[1751]: drkonqi-sentry-postman.timer - Submitting pending crash events skipped, unmet condition check ConditionPathExistsGlob=/home/stepha
n/.cache/drkonqi/sentry-envelopes/*
Aug 03 15:24:43 BlackSnake systemd[1751]: Starting plasma-kwin_x11.service - KDE Window Manager...
Aug 03 15:24:43 BlackSnake systemd[1751]: Starting plasma-plasmashell.service - KDE Plasma Workspace...
Aug 03 15:24:44 BlackSnake systemd[1751]: Started plasma-kwin_x11.service - KDE Window Manager.
Aug 03 15:24:44 BlackSnake systemd[1751]: Started plasma-plasmashell.service - KDE Plasma Workspace.
Aug 03 15:24:44 BlackSnake systemd[1751]: Started drkonqi-coredump-pickup.service - Consume pending crashes using DrKonqi.
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"Soniq.Widget", fileName: "/home/stephan/.local/share/plasma/plasmoids/Soniq.Wid
get/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"Bix.Plasma.Player", fileName: "/home/stephan/.local/share/plasma/plasmoids/Bix.
Plasma.Player/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"Plasma.Flex.Hub", fileName: "/home/stephan/.local/share/plasma/plasmoids/Plasma
.Flex.Hub/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"org.kde.netspeedWidget", fileName: "/home/stephan/.local/share/plasma/plasmoids
/org.kde.netspeedWidget/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"Plasma.Control.Hub", fileName: "/home/stephan/.local/share/plasma/plasmoids/Pla
sma.Control.Hub/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"org.kde.windowtitle.Fork ", fileName: "/home/stephan/.local/share/plasma/plasmoi
ds/org.kde.windowtitle.Fork/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"org.kde.windowtitle", fileName: "/home/stephan/.local/share/plasma/plasmoids/or
g.kde.windowtitle/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"Solid.Square.Music", fileName: "/home/stephan/.local/share/plasma/plasmoids/Sol
id.Square.Music/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"SlateWeather", fileName: "/home/stephan/.local/share/plasma/plasmoids/SlateWeat
her/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"zayron.simple.separator" , fileName: "/home/stephan/.local/share/plasma/plasmoid
s/zayron.simple.separator/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"Minimal.chaac.weather", fileName: "/home/stephan/.local/share/plasma/plasmoids/
Minimal.chaac.weather/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"org.kde.Big.Clock", fileName: "/home/stephan/.local/share/plasma/plasmoids/org.
kde.Big.Clock/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"org.kde.plasma.youtube", fileName: "/home/stephan/.local/share/plasma/plasmoids
/org.kde.plasma.youtube/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"zayron.almanac.V2", fileName: "/home/stephan/.local/share/plasma/plasmoids/zayr
on.almanac.V2/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"com.marcinorlowski.monol ithmhl", fileName: "/home/stephan/.local/share/plasma/p
lasmoids/com.marcinorlowski.monolithmhl/metadata.json") does not match requested format "Plasma/Applet"
Aug 03 15:24:44 BlackSnake plasmashell[2632]: KPackageStructure of KPluginMetaData(pluginId:"Hiragana.Calendar", fileName: "/home/stephan/.local/share/plasma/plasmoids/Hira
gana.Calendar/metadata.json") does not match requested format "Plasma/Applet"

[greenster]

Third code from post 3

coredumpctl list | grep kwin
Mon 2026-05-18 10:56:06 CEST 2588 1000 1000 SIGSEGV missing /usr/bin/kwin_x11 -
Fri 2026-05-29 18:01:39 CEST 2582 1000 1000 SIGSEGV missing /usr/bin/kwin_x11 -
Wed 2026-06-03 15:01:38 CEST 2578 1000 1000 SIGSEGV missing /usr/bin/kwin_x11 -
Thu 2026-07-02 19:36:39 CEST 2585 1000 1000 SIGSEGV missing /usr/bin/kwin_x11 -
Tue 2026-07-14 16:45:02 CEST 2606 1000 1000 SIGSEGV missing /usr/bin/kwin_x11 -
Wed 2026-07-15 11:55:49 CEST 2605 1000 1000 SIGSEGV missing /usr/bin/kwin_x11 -
Wed 2026-07-15 21:45:17 CEST 2583 1000 1000 SIGSEGV missing /usr/bin/kwin_x11 -
Mon 2026-07-20 11:00:11 CEST 13613 1000 1000 SIGSEGV missing /usr/bin/kwin_x11 -
Wed 2026-07-29 18:05:07 CEST 2727 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 10:34:54 CEST 2541 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 10:36:28 CEST 2560 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 10:37:28 CEST 2555 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 10:38:21 CEST 2568 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 15:11:50 CEST 2528 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 15:12:30 CEST 2558 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 15:13:29 CEST 2570 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 15:15:01 CEST 5677 1000 1000 SIGABRT present /usr/bin/kwin_x11 1.2M
Thu 2026-07-30 15:15:01 CEST 3259 1000 1000 SIGSEGV present /usr/bin/kwin_x11 5.9M
Thu 2026-07-30 15:15:53 CEST 7717 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 15:18:40 CEST 2558 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 15:22:44 CEST 2516 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 16:19:39 CEST 2527 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 16:22:35 CEST 2574 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 16:24:09 CEST 2543 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Thu 2026-07-30 16:25:25 CEST 2565 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Fri 2026-07-31 04:31:34 CEST 2537 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Fri 2026-07-31 13:31:08 CEST 2544 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Sun 2026-08-02 17:06:29 CEST 2594 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Sun 2026-08-02 17:07:25 CEST 2606 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Sun 2026-08-02 17:08:33 CEST 2604 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Sun 2026-08-02 20:36:57 CEST 2587 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Sun 2026-08-02 20:40:30 CEST 2617 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 04:47:27 CEST 2668 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 07:34:56 CEST 2562 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 07:47:42 CEST 2617 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 13:31:06 CEST 2587 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 13:46:03 CEST 2578 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 13:48:52 CEST 2584 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 14:40:58 CEST 2614 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 14:42:21 CEST 2611 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 14:46:12 CEST 2612 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 15:24:47 CEST 2614 1000 1000 SIGSEGV present /usr/bin/kwin_x11 6.1M
Mon 2026-08-03 18:49:24 CEST 2625 1000 1000 SIGSEGV present /usr/bin/kwin_x11

[greenster]

Last bit of code for today:

PID: 2625 (kwin_x11)
UID: 1000 (stephan)
GID: 1000 (stephan)
Signal: 11 (SEGV)
Timestamp: Mon 2026-08-03 18:49:23 CEST (29min ago)
Command Line: /usr/bin/kwin_x11 --replace
Executable: /usr/bin/kwin_x11
Control Group: /user.slice/user-1000.slice/user@1000.service/session.slice/plasma-kwin_x11.service
Unit: user@1000.service
User Unit: plasma-kwin_x11.service
Slice: user-1000.slice
Owner UID: 1000 (stephan)
Boot ID: 01f4f556450a4040935ef3dc0a9c70e8
Machine ID: 7fe66da5923345f8b567d75ee4af2f1c
Hostname: BlackSnake
Storage: /var/lib/systemd/coredump/core.kwin_x11.1000.01f4f556450a4040935ef3dc0a9c70e 8.2625.1785775763000000.zst (present)
Size on Disk: 6.1M
Package: kwin-x11/4:6.6.4-0ubuntu1
build-id: 3ece8a3c2fad024297c9c0d1f1b0bcd4aa91ecd4
Message: Process 2625 (kwin_x11) of user 1000 dumped core.

Module /usr/bin/kwin_x11 from deb kwin-x11-4:6.6.4-0ubuntu1.amd64
Module linux-vdso.so.1 from deb linux-7.0.0-28.28.amd64
Module libQt6Quick3DUtils.so.6 from deb qt6-quick3d-6.10.2-1.amd64
Module libQt6Quick3DRuntimeRender.so.6 from deb qt6-quick3d-6.10.2-1.amd64
Module libQt6Quick3D.so.6 from deb qt6-quick3d-6.10.2-1.amd64
Module libqquick3dplugin.so from deb qt6-quick3d-6.10.2-1.amd64
Module KirigamiPlasmaStyle.so from deb libplasma-6.6.6-0ubuntu0.1~ubuntu26.04~ppa1.amd64
Module libqqc2desktopstyleplugin.so from deb kf6-qqc2-desktop-style-6.24.0-0ubuntu1.amd64
Module libKF6SonnetCore.so.6 from deb kf6-sonnet-6.24.0-0ubuntu1.amd64
Module libsonnetquickplugin.so from deb kf6-sonnet-6.24.0-0ubuntu1.amd64
Module liborg_kde_desktop_private.so from deb kf6-qqc2-desktop-style-6.24.0-0ubuntu1.amd64
Module libKirigamiTemplates.so.6 from deb kf6-kirigami-6.24.0-0ubuntu1.amd64
Module libKirigamiTemplatesplugin.so from deb kf6-kirigami-6.24.0-0ubuntu1.amd64
Module libQt6ShaderTools.so.6 from deb qt6-shadertools-6.10.2-1.amd64
Module libqtgraphicaleffectsprivateplugin.so from deb qt6-5compat-6.10.2-1.amd64
Module libKirigamiPrivate.so.6 from deb kf6-kirigami-6.24.0-0ubuntu1.amd64
Module libKirigamiPrivateplugin.so from deb kf6-kirigami-6.24.0-0ubuntu1.amd64
Module libquickwindowplugin.so from deb qt6-declarative-6.10.2+dfsg-3.amd64
Module liborg_kde_desktop.so from deb kf6-qqc2-desktop-style-6.24.0-0ubuntu1.amd64
Module libQt6QuickControls2Basic.so.6 from deb qt6-declarative-6.10.2+dfsg-3.amd64
Module libqtquickcontrols2basicstyleplugin.so from deb qt6-declarative-6.10.2+dfsg-3.amd64
Module libqtquickcontrols2plugin.so from deb qt6-declarative-6.10.2+dfsg-3.amd64
Module KF6WindowSystemX11Plugin.so from deb kf6-kwindowsystem-6.24.0-0ubuntu1.amd64
Module libPlasma.so.7 from deb libplasma-6.6.6-0ubuntu0.1~ubuntu26.04~ppa1.amd64

[die.boer]

you have a long list of third-party widgets:
Soniq.Widget
Bix.Plasma.Player
Plasma.Flex.Hub
org.kde.windowtitle
SlateWeather
Big.Clock
youtube
Hiragana.Calendar
...and many others

Those messages themselves aren't fatal, but they show you have a large number of third-party Plasma widgets installed.

On Plasma 6, some older widgets can destabilize Plasma or KWin, especially during startup.


try this test : temporarily disable all user-installed Plasma widgets without deleting them.

mv ~/.local/share/plasma/plasmoids ~/.local/share/plasma/plasmoids.backup

then reboot

see if Kwin still crashes


If nothing changes, you can restore them with:

mv ~/.local/share/plasma/plasmoids.backup ~/.local/share/plasma/plasmoids