what does launchctl config user path do?

I was having a strange problem with PATH environment variable in MacOS that I spent several hours to debug:

Some time ago, when I was trying to fix the issue IntelliJ terminal PATH variable not the same with iTerm, I followed an online article and executed this:

sudo launchctl config user path $PATH
Apparently this command sets and persists the value of PATH variable at that moment of time somewhere and that variable is loaded even before my shell is loaded whenever I start a new zsh session. Only recently I recognized this issue because I removed some paths location setting in my zshrc and the PATH variable still didn't reflect
My question is where does that command store the PATH variable value? and how does it load that value before my shell is loaded?

(For people who wonder how I fixed the issue: I executed the command again to set path to empty value: sudo launchctl config user path '')

Solution

The sudo launchctl config user path <...> command updates /private/var/db/com.apple.xpc.launchd/config/user.plist:

$ cat /private/var/db/com.apple.xpc.launchd/config/user.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>PathEnvironmentVariable</key>
    <string>/opt/homebrew/bin:/usr/bin:/bin:/usr/sbin:/sbin</string>
</dict>
</plist>

Tested on my system, which is currently macOS 14.2.1 (AppleSilicon). You can replace user with system to operate on the system-wide preferences. Both require sudo, oddly enough.

You can query launchd's current custom PATH setting (will return an empty string if you haven't configured one) with:

launchctl getenv PATH

You can query the default PATH by executing:

sysctl -n user.cs_path

To undo any customizations, you can issue:

sudo defaults delete /private/var/db/com.apple.xpc.launchd/config/user.plist PathEnvironmentVariable

(requires a reboot to take effect)