SSH Exit Code 255 in CI: Connection or Auth Failure

SSH exit code 255 means ssh itself failed to connect or authenticate - it is not a status from the remote command.

A step exiting 255 from ssh never ran (or never reached) the remote command; the SSH session setup failed.

What it means

ssh reserves 255 for its own fatal errors: connection refused, network unreachable, host-key verification failure, or authentication failure. Any other code is the remote command's own exit status.

Common causes

Host key mismatch or unknown host.
Wrong key, user, or rejected auth.
The host was unreachable or refused the connection.

How to fix it

Re-run with ssh -v to see where setup fails; fix the key, known_hosts entry, or network path. A transient network/host blip can clear on retry - Latchkey auto-retries these mechanical connection failures.

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