The command no longer sends a shell script to the host. It fetches
~/.ssh/authorized_keys with the system sftp in batch mode, adds the key
line here, and writes the file back in a second session: mkdir and chmod
on ~/.ssh, put to authorized_keys.keyfunc-<random>, chmod 600, then
rename over authorized_keys. A run that adds a line connects twice; one
that finds the line there connects once and stops. A failed step leaves
everything as it is and names the uploaded file.
sftp echoes the commands it runs, so all of its output goes to standard
error and the tool prints only "added" or "already present". Batch mode
cannot prompt for a password; the README says so.
Model: opus-5
keyfunc ssh install appends the public line on a host through the system ssh, only when absent, feeding the line on standard input; keyfunc ssh to serves the derived key from an in-process agent on a private socket and runs the system ssh with it, the private key never on disk. Two review rounds; the second passed with no findings.
Model: opus-5 (implementation and review); fable-5-1 (landing)
