sequenceDiagram
  autonumber
  participant C as Caller
  participant D as SSHWrapper (driver.py)
  participant CL as Client (client.py)
  participant OS as OS/FS

  C->>D: Configure ssh_identity or ssh_identity_file
  alt ssh_identity_file provided
    D->>OS: Read ssh_identity_file
    OS-->>D: Identity contents or error
    D->>D: Validate mutual exclusivity
  else ssh_identity provided
    D->>D: Validate mutual exclusivity
  end

  C->>D: get_ssh_identity()
  D-->>C: ssh_identity (string or None)

  C->>CL: _run_ssh_local(..., ssh_identity, args)
  opt ssh_identity provided
    CL->>OS: Create temp file with 0600 perms
    CL->>CL: identity_file = temp path
  end
  CL->>CL: _build_ssh_command_args(..., identity_file, args)
  note over CL: Include -i identity_file if set<br/>Inject -l default_username if not explicitly provided
  CL->>OS: Execute SSH command
  alt success or failure
    OS-->>CL: Exit status / output
  end
  CL->>OS: Cleanup temp identity file
  OS-->>CL: Deleted or warn on failure
  CL-->>C: Result