Profile sourcing and $GUIX_PROFILE when using guix home

[Kenan Toker <kenan@kdtsh.net>]

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Hello wonderful Guix users and developers!

I am looking for some help understanding fundamental concepts in Guix. 
In particular, I want to better understand how $GUIX_PROFILE works, and 
how profiles are sourced when I boot, login, etc. I am using Guix System 
and generally keep up-to-date with the main branch, usually running a 
guix pull every other day before I make any configuration changes or 
install new packages.

I have recently started using guix home, and my $GUIX_PROFILE is 
automatically set to:
     ~/.guix-home/profile
This is currently a symlink to the directory:
     /gnu/store/708xnkkd86xf4nx9mmf8szpwi4yd9ms2-profile/

I also have a symlink in my $HOME called ~/.guix-profile, which links to:
     /var/guix/profiles/per-user/me/guix-profile
This links to the symlink:
     /var/guix/profiles/per-user/me/guix-profile-n-link
Which in turn currently links to the directory:
     /gnu/store/3mjlciy8fywyvajcxy76gy3dscp1bmns-profile/

What I am wondering is:
     1. Where is $GUIX_PROFILE set for my user, and how has this changed 
since using guix home?
     2. ~/.guix-profile/etc/profile seems to have been sourced at some 
point between booting, logging into my account, and opening an 
interative shell, because all my packages are present when I run `guix 
package -I`; I also have all the packages I expect in Gnome Shell. 
How/when was ~/.guix-profile/etc/profile sourced if it is not set to 
$GUIX_PROFILE?

Slightly related: before I started using guix home, I found that my 
$GUIX_PROFILE would sometimes be set to ~/.config/guix/current, which 
links to:
     /var/guix/profiles/per-user/me/current-guix
This links to the symlink:
     /var/guix/profiles/per-user/me/current-guix-n-link
Which in turn currently links to the directory:
     /gnu/store/n6syypzqx7cfr7ypd56ww04313xh888k-profile/

(This behaviour, where $GUIX_PROFILE was ~/.config/guix/current instead 
of ~/.guix-profile, did not always happen - I have never found a clear 
pattern as to why it happened when it did. I did find that it would 
correlate with unexpected behaviour like my laptop not suspending on lid 
close, but I have never determined the exact cause of this so it might 
not be related.)

I understand that ~/.config/guix/current is a profile containing the 
current version of Guix (along with the channels I use), and that 
~/.guix-profile is a profile containing packages installed to the 
default profile. On this, I am wondering
     1. How it is that both ~/.config/guix/current/etc/profile and 
~/.guix-profile/etc/profile are sourced at some point before or during 
login?
     2. Why it was that $GUIX_PROFILE would sometimes be set to 
~/.config/guix/current (before I started using guix home)?

Thanks a lot everyone,
Kenan


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