Lennart Poettering on Nostr: I am pretty sure it makes more sense if the logic that invokes the payload should set ...

I am pretty sure it makes more sense if the logic that invokes the payload should set this up, as it knows best in which context it invokes the payload.

With systemd v257 we added a tiny feature to make this a bit nicer:

There are now three environment variables: $SHELL_PROMPT_PREFIX, $SHELL_PROMPT_SUFFIX, $SHELL_WELCOME, which a login shell will honour when initializing (by including the prefix/suffix in $PS1, and printing the other env var immediately as welcome text).