Session states

Every session sess knows about — every saved snapshot, every live tmux session, or both at once under the same name — is in exactly one of four states. This is computed from real system state, not inferred separately by each command: list, status, switch, and the picker all call the same detection logic, so they never disagree with each other.

State	Meaning
`RUNNING`	A live tmux session exists for this name.
`SAVED`	A valid snapshot exists, nothing live, and everything it references still looks reachable.
`STALE`	A valid snapshot exists, nothing live, but something it references — currently: a pane's working directory — no longer exists on disk.
`BROKEN`	The saved file exists but could not be parsed (corrupted JSON, usually).

RUNNING takes priority: if a live tmux session exists under that name, that's the state, even if its saved snapshot happens to look stale or broken underneath.

Where you see this

sess list      # STATE column
sess status    # grouped counts + one line per session
sess switch    # color-coded in the picker, drives what Enter does

What happens with each state in the picker

Running or Saved — pressing Enter opens it (attaches or restores).
Stale — pressing Enter shows what's missing and asks: open anyway, delete, or cancel. Nothing happens silently.
Broken — pressing Enter shows the parse error. There's nothing to open; use d to delete it, or run sess prune to clear out every broken snapshot at once.