New Features

systemd provides the privilege-escalator run0, which like sudo expects the user's password rather than root's, and in fact checks for membership of the "sudo" group, but in theory makes sudo itself largely redundant
to help with deprecating the old "one-liner" SourcesList format in favor of deb822 format there's now apt modernize-sources
something that mostly won't be visible to end users though it took significant development and organization work: the t64 transition, making various libraries Y2038-safe.

Changes

systemd by default now creates /tmp as a tmpfs. On new installs it also introduces a "tmpreaping" regime for /tmp and /var/tmp, but this is opt-in for upgraded systems (see NEWS.Debian.gz)
the old utmp/wtmp db format was Y2038-buggy (see t64 above), and the functionality is these days mostly covered by other logging mechanisms, so various tools have been either dropped or replaced: lastlog (in login) is replaced by the package lastlog2 (and its recommended packages), last (in util-linux) is replaced by the package wtmpd (and ditto), and utils-linux provides a new lslogins
utils-linux-extra also drops mesg and write while adding new tools including exch and waitpid
since all trixie systems should now have a "merged" /usr, usrmerge and usr-is-merged are removable dummy packages

Upgrade Issues

Users of i386 (the original Debian architecture) should be aware that although it's still on the architectures list, it's intended for legacy functions only - in chroots, for multiarch, etc; dist-upgrades to trixie are NOT supported.

Please read the Release Notes, which list several packages (such as dovecot and libvirt) that will require configuration changes.

CategoryPermalink: Mentioned in the Release Notes