diff --git a/CLAUDE.md b/CLAUDE.md
index 2555812..438fb6c 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -55,7 +55,19 @@ commits), they describe the pre-2026-09-03 app, not the current one.
   `delete_event` — a bad push can't be cleaned up via the HA API, only
   manually in Google Calendar. No duplicate-prevention: re-pushing the
   same date's menu creates a second event — this is why the default
-  schedule is a single day/week, not daily (see below). The webhook id is
+  schedule is a single day/week, not daily (see below).
+  **`mode: parallel`, not the default `single` (fixed 2026-09-03 after a
+  real bug):** a week push fires one webhook POST per school day
+  back-to-back with no delay. Under `mode: single`, HA rejects any
+  webhook trigger that arrives while a previous run is still executing
+  (`calendar.create_event` itself takes ~600-700ms) — 4 of every 5 days
+  were silently dropped as `failed_single`, so only one day's event ever
+  actually got created per week push. Found via `ha_get_automation_traces`
+  after the user reported a manual test push not showing up on the
+  calendar. Each invocation is independent (one `calendar.create_event`
+  call, no shared state), so `parallel` is the correct mode per HA's own
+  guidance ("independent per-entity actions → parallel"), not just a
+  workaround. The webhook id is
   a random token that lives only in the server's `.env` (`HA_WEBHOOK_URL`)
   and in the automation's trigger config — never committed here. If the
   calendar push stops working, check both ends: `GET /api/integrations`