pub const EVENT_SUBAGENT_BACKFILL_STATUS: &str = "subagent:backfill_status";Expand description
Fired by SubagentWatcher::scan_session_subagents (the pane-reopen
cold-backfill entry point, subagent_watcher/scan.rs) so a pane can
show its BrainSpinner overlay (block.tsx’s ready() gate) until its
own subagent/dispatch history has actually finished backfilling, instead
of exposing the Activity Dock’s genuinely-changing intermediate states —
see docs/retro/retro-activity-dock-flicker-survives-debounce-fix-2026-08-24.md
§5 option 1/2. Payload: { "status": "started" | "done" }. persist: 2,
same rationale as EVENT_AGENT_RESUME_RETRY above — both ends travel
over this one channel, so a mount-time EventReadHistoryCommand read
(guarding the same “pane subscribed after the backend already finished”
race that event’s own hook already handles) always recovers the correct
current status rather than a stale one.