A dormant session comes back under the same uuid and sidecar, so its
name, created_at, env and worktree ownership survive; only the tmux
session and the PTY bridge are new. The command is the matching preset's
resume_command with {agent_session} filled in, falling back to the
command the session was spawned with.
Refused with 409 for a session that is already running or whose cwd is
gone. Attaching to a session with no bridge now answers 409
not_attachable instead of 404 unknown_session, so a client can tell a
resumable session from one that does not exist.
Miguel Palhas
bb6b885c68