1Password SSH Agent how to set specific ssh key

You can specify which key to use for which host in ~/.ssh/config using IdentityFile option, where the identity file is the public key to use and the private key is stored in 1Password. You may also need to specify IdentitiesOnly yes.

Example for mailto:user99@example.com:


Host example.com
User user99
IdentityFile ~/.ssh/identity.pub
IdentitiesOnly yes


More here:
https://linux.die.net/man/5/ssh_config

I've been able to achieve this with git's conditional includes. Here's what a config may look like:

# ~/.config/git/config

[include]
    path = base-config.inc
[includeIf "hasconfig:remote.*.url:*:jc00ke/**"]
    path = personal-config.inc
[includeIf "hasconfig:remote.*.url:*:WORK/**"]
    path = work-config.inc

# ~/.config/git/personal-config.inc
[user]
    name = Jesse Cooke
    email = jesse@example.com
    signingkey = ~/.ssh/personal.pubkey

# ~/.config/git/work-config.inc
[user]
    name = Jesse Cooke
    email = jesse@work.example.com
    signingkey = ~/.ssh/work.pubkey

Here's my real dotfiles; this has worked for me for a while now.