jj: Jj git fetch not connecting to ssh-agent

Overview

For some reason, ssh operations don’t seem to be connecting to the ssh-agent for me. This is means that my ~/.ssh/config doesn’t get read, so port and key settings never get read:

$ jj git fetch
Error: Unexpected git error when fetching: failed to connect to git.wilsonb.com: Connection refused; class=Os (2)

Sanity checks

Level 1

I am fairly sure my ssh-agent is running and SSH_AUTH_SOCK is setup correctly:

$ ssh-add -L
...
<my key>
...

Level 2

But, just to be sure, I directly checked whether jj is actually trying to connect to ssh-agent

$ strace -fo ~/jj.strace jj git fetch
...
$ grep -F "$SSH_AUTH_SOCK" ~/jj.strace || echo nope
nope

Level 3

But since SSH_AUTH_SOCK was added in 4a1576c, I started to doubt my sanity, so I ran ssh-agent -d, which stays in the foreground and noisily shows when anyone connects. Running something like ssh example.com does cause it to generate connection logs; however, in the same shell as that working ssh command, running jj git fetch errors out, and ssh-agent stays completely silent.

Am I missing something obvious?

Version info

I am running the latest flake on HEAD:

$ nix shell github:martinvonz/jj#jujutsu
$ command -v jj
/nix/store/8i7lzldsqwl35zl04p8x7vlll03zjch4-jujutsu-unstable-86318bf/bin/jj