Run ssh-agent via fish shell

fish-agent.sh

#!/bin/bash
#
# Convert ssh-agent output to fish shell
#

eval "$(ssh-agent)" >/dev/null

echo "set SSH_AUTH_SOCK \"$SSH_AUTH_SOCK\"; export SSH_AUTH_SOCK"
echo "set SSH_AGENT_PID \"$SSH_AGENT_PID\"; export SSH_AGENT_PID"

If you're using macOS, you don't need to manage ssh-agent (whether it be your Fish config or any other shell).

Instead, run this for each key you use to store the passphrase in the Keychain:

ssh-add --apple-use-keychain ~/.ssh/my_key
# This flag works with Apple's `/usr/bin/ssh-add`.
# (Other `ssh` versions may lack the flag.)

Then add this to ~/.ssh/config:

Host *
    UseKeychain yes
    AddKeysToAgent yes

With the above settings:

• on first use of each key,
• ssh will look up the passphrase from your Keychain,
• and load the key into the agent,
• without prompting you.

You get to avoid the complexities of starting and stopping ssh-agent correctly. No startup code, no stale sockets, no orphaned agent processes.

P.S. This answer matches my experience, and Claude Sonnet 4.6 agrees.