Agent sessions are amnesiac. Something worth remembering surfaces mid-session — a follow-up, a thing to check once a deploy lands — and there’s nowhere to put it that a future session will actually see.
Later is a durable local queue for exactly that. Claude Code or Codex leaves a message for a future session in the same project, or in every project, and the message surfaces the next time a live session gets a prompt after it’s due.
It is deliberately not a notification service or a job runner. Nothing runs in the background and nothing tries to wake a sleeping laptop. A prompt hook reads the queue; if a reminder is due, it drops a short pointer into the active agent’s context and leaves the full body on disk until someone asks for it.