[stack_underflow]

I think anyone who suggests daily driving Debian testing should also mention the fact that packages can disappear from testing for weeks/months at a time (and reappear later). It's recommended to configure `unstable` in your sources as well but set up apt pinning so that those packages are only pulled in if they're missing in testing. See: https://wiki.debian.org/DebianTesting "Best practices for Testing users"

In practice this means adding something like this to /etc/apt/preferences (along with adding entries for `unstable` in /etc/apt/sources.list)

    # use `n=` when referencing codename (i.e. buster/bullseye/...)
    Package: *
    Pin: release n=bookworm
    Pin-Priority: 550

    # use `a=` when referencing archive (i.e. stable/testing/unstable)
    Package: *
    Pin: release a=unstable
    Pin-Priority: 520

That way apt will pull in any packages missing in testing from unstable, and once the package is reintroduced to testing, will prefer that version rather than continue to track unstable.

Maybe I've been lucky but I've been running testing on my non-server desktops and laptops for 13 years now and have only rendered my system unbootable once (required having to boot up a live CD to reinstall an older working version of some bad libpcre update that had been rolled out).