SSH Agent Not Automatically Unlock ID

Somehow, under Silverblue, the SSH Agent does not seem to persistently add SSH IDs. E.g. doing a git update reports the following:

[user@localhost u-boot.git]$ git remote update
Fetching gitlab
sign_and_send_pubkey: signing failed for RSA "/var/home/user/.ssh/id_rsa" from agent: agent refused operation Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
error: Could not fetch gitlab

If I do ssh-add it works during this login session:

[user@localhost u-boot.git]$ ssh-add
Enter passphrase for /var/home/user/.ssh/id_rsa: 
Identity added: /var/home/user/.ssh/id_rsa (/var/home/user/.ssh/id_rsa)
[user@localhost u-boot.git]$ git remote update
Fetching gitlab

But it won’t be preserved across log-ins. How exactly is this supposed to work in Silverblue?