/heartbeat every <interval> <prompt> gives the current session one
recurring instruction. When the session is idle and the interval has
elapsed, the prompt is injected as a plain user turn — same
conversation, same context, prompt cache and role alternation
untouched.
- CLI: idle-poll watchdog thread (wake-word watchdog pattern) feeding
_pending_input; gateway: single gateway-wide async poller injecting
through the adapter FIFO. Busy sessions coalesce their tick to the
next idle poll.
- Missed ticks coalesce (anchor resets on fire) — a busy hour yields
ONE heartbeat turn, never a backlog. Real user messages always win.
- 60s interval floor; injected prompt carries a don't-invent-work
guard so idle heartbeats don't generate busywork.
- State persists in SessionDB.state_meta (heartbeat:<session_id>),
survives /resume, migrates across compression session rotations
alongside /goal state.
- Session-scoped and in-process by design — durable cross-process
schedules remain the cron subsystem's job (docs draw the boundary).
- Slack stays under the 50-slash cap via /hermes heartbeat; ghost-text
suggester now prefers the shortest prefix match so /he still
suggests /help.
Adapted from the session-heartbeat concept in Prime Intellect's
Prime-Agent (/heartbeat).
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