Just upgraded from bullseye to bookworm and encountered this, host is on
bullseye guest was on bullseye but is now on bookworm, unlike the
original reporter adding a spice-vdagent.desktop file does work, the
contents are:
[Desktop Entry]
Exec=/usr/bin/spice-vdagent
Icon=dialog-scripts
Name=spice-vdagent
Path=
Type=Application
X-KDE-AutostartScript=true
Without the desktop file at login spice-vdagent.service and
spice-vdagentd.service are both not running.
Manually starting them with sudo systemctl start spice-vdagent.service
and systemctl start spice-vdagent --user doesn't seem to help the
services start but screen resizing doesn't work.
Please let me know if you need me to debug further.