AI Implementation feature(905): Challenges Page and Challenge Solve Modal 1.01 (#47)

docs/guides/event-window.md

@@ -3,7 +3,7 @@ type: guide
 title: Event Window
 description: How the event window state machine is computed and surfaced via REST + SSE.
 tags: [guide, event, countdown, sse, state-machine]
-timestamp: 2026-07-22T09:03:53Z
+timestamp: 2026-07-23T01:19:00Z
 ---
 
 # Configuration
@@ -88,6 +88,24 @@ itself) close the SSE source and clear the tick interval, so leaving
 the shell (e.g. by logging out and landing on `/login`) tears the
 stream down cleanly.
 
+# Auto-reload at the transition boundary
+
+`ChallengesPage` registers a one-shot handler with
+`EventStatusStore.subscribeReloadAtCountdownZero(() => window.location.reload())`
+in its constructor; the returned disposer is wired into its
+`DestroyRef` so the subscription is cleared when the page is destroyed.
+The subscription is **page-owned** and independent of the transport
+lifecycle (`start()`/`stop()` only manage the SSE source + tick +
+watcher; they never clear the reload handler). The store owns a 1 s
+watcher (`checkZero`) that fires the handler exactly once when the
+local-clock countdown reaches zero (`countdown → running`) or the
+running countdown reaches zero (`running → stopped`). The latch is
+re-armed on every state transition (countdown→running and
+running→stopped), and a strict-equal follow-up SSE frame is collapsed
+so a duplicate zero-countdown payload cannot disarm the latch. After
+`stop()` (end-of-life teardown) the store is fully reset; a fresh
+handler subscription re-installs the watcher.
+
 # Push path
 
 1. The admin cron / settings update writes to `setting.eventStartUtc` /