Claude Code and Codex start their shells without SSH_AUTH_SOCK. id_ed25519
has a passphrase, so batch ssh from a harness had no way to unlock it and
failed with "Permission denied (publickey)" against server.gib, junior.gib
and git.gbrown.org. The key and the per-host blocks were right the whole
time, which made it read as a key problem and cost several rounds of
checking keys that were never wrong.
The desktop keyring agent at $XDG_RUNTIME_DIR/keyring/ssh already holds the
key unlocked for the interactive session. A Host * block with IdentityAgent
points every host at that socket, so a shell that inherits no agent gets the
same one the terminal uses.
Gabriel Brown
501f7306ed