events: reschedule notifications + 7 tests

ev/reschedule-notifications: when an event carries per-occurrence overrides,
reads the roster at each overridden occurrence's original occ-key and emits a
reschedule message per booked attendee (old-start/new-start/new-duration).
Idempotency key = original-key/reschedule/new-start. 272/272 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/events/reminders.sx

@@ -94,3 +94,54 @@
 ;; A single digest message summarising an actor's upcoming booked occurrences.
 ;; :items is ({:event :start} ...); empty when the actor has nothing booked.
 (define ev/agenda-digest (fn (b store actor ws we) {:items (map (fn (occ) {:event (get occ :id) :start (get occ :start)}) (ev/agenda-for-p b store actor ws we)) :id (str actor "/digest/" ws "-" we) :recipient actor}))
+
+;; ---- reschedule notifications ----
+;; When an event carries per-occurrence overrides (ev-with-override), every
+;; attendee booked at the ORIGINAL start should be told the new time. Bookings
+;; were made against the original occ-key (id@orig-start), so we read that
+;; roster. Idempotency key encodes the original key and the new start, so
+;; re-deriving the same reschedule never double-notifies.
+(define
+  ev/reschedule-notifications
+  (fn
+    (b event)
+    (let
+      ((overrides (ev-or (get event :overrides) (list)))
+        (evid (get event :id))
+        (dur (get event :duration)))
+      (reduce
+        (fn
+          (acc entry)
+          (let
+            ((orig-start (first entry))
+              (ov (first (rest entry))))
+            (let
+              ((occ (ev-occ evid orig-start dur))
+                (new-start (get ov :start))
+                (new-duration (get ov :duration)))
+              (let
+                ((key (ev-occ-key occ)))
+                (append
+                  acc
+                  (map
+                    (fn
+                      (actor)
+                      {:id (str key "/reschedule/" new-start)
+                        :recipient actor
+                        :event evid
+                        :old-start orig-start
+                        :new-start new-start
+                        :new-duration new-duration})
+                    (ev/roster-occ b occ)))))))
+        (list)
+        overrides))))
+
+;; Project a reschedule notification to notify's (id recipient body) shape.
+(define
+  ev/reschedule-notify->msg
+  (fn
+    (r)
+    (list
+      (get r :id)
+      (get r :recipient)
+      (list :rescheduled (get r :event) (get r :old-start) (get r :new-start)))))

lib/events/scoreboard.json

@@ -1,8 +1,8 @@
 {
   "lang": "events",
-  "total_passed": 265,
+  "total_passed": 272,
   "total_failed": 0,
-  "total": 265,
+  "total": 272,
   "suites": [
     {"name":"calendar","passed":51,"failed":0,"total":51},
     {"name":"availability","passed":22,"failed":0,"total":22},
@@ -11,8 +11,8 @@
     {"name":"booking-notify","passed":11,"failed":0,"total":11},
     {"name":"ticket","passed":31,"failed":0,"total":31},
     {"name":"notify","passed":7,"failed":0,"total":7},
-    {"name":"reminders","passed":14,"failed":0,"total":14},
+    {"name":"reminders","passed":21,"failed":0,"total":21},
     {"name":"federation","passed":23,"failed":0,"total":23}
   ],
-  "generated": "2026-06-07T07:20:13+00:00"
+  "generated": "2026-06-07T07:46:42+00:00"
 }

lib/events/scoreboard.md

@@ -1,6 +1,6 @@
 # events scoreboard
 
-**265 / 265 passing** (0 failure(s)).
+**272 / 272 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
@@ -11,5 +11,5 @@
 | booking-notify | 11 | 11 | ok |
 | ticket | 31 | 31 | ok |
 | notify | 7 | 7 | ok |
-| reminders | 14 | 14 | ok |
+| reminders | 21 | 21 | ok |
 | federation | 23 | 23 | ok |

lib/events/tests/reminders.sx

@@ -208,6 +208,61 @@
                 (get empty-dig :items)
                 (list)))))))))
 
+;; ---- reschedule notifications ----
+(define
+  ev-rm-rs-run-all!
+  (fn
+    ()
+    (let
+      ((b (persist/open))
+        (ev (ev-event (quote yoga) (ev-dt 2026 6 1 9 0) 60 {:freq :daily :count 3} 20)))
+      (let
+        ((occ2 (ev-occ (quote yoga) (ev-dt 2026 6 2 9 0) 60)))
+        (do
+          (ev/book-occ! b (ev/add-event (ev/empty) ev) (quote nia) occ2)
+          (ev/book-occ! b (ev/add-event (ev/empty) ev) (quote ola) occ2)
+          ;; reschedule the Jun 2 occurrence to 14:00 / 90 min
+          (let
+            ((moved (ev-with-override ev (ev-dt 2026 6 2 9 0) (ev-dt 2026 6 2 14 0) 90)))
+            (let
+              ((ns (ev/reschedule-notifications b moved)))
+              (do
+                (ev-rm-check!
+                  "every booked attendee is notified of the reschedule"
+                  (map (fn (n) (get n :recipient)) ns)
+                  (list (quote nia) (quote ola)))
+                (ev-rm-check!
+                  "reschedule carries old and new start"
+                  (list (get (first ns) :old-start) (get (first ns) :new-start))
+                  (list (ev-dt 2026 6 2 9 0) (ev-dt 2026 6 2 14 0)))
+                (ev-rm-check!
+                  "reschedule carries the new duration"
+                  (get (first ns) :new-duration)
+                  90)
+                (ev-rm-check!
+                  "reschedule idempotency key encodes original key + new start"
+                  (get (first ns) :id)
+                  (str (ev-occ-key occ2) "/reschedule/" (ev-dt 2026 6 2 14 0)))
+                (ev-rm-check!
+                  "reschedule projects to notify wire shape"
+                  (ev/reschedule-notify->msg (first ns))
+                  (list
+                    (str (ev-occ-key occ2) "/reschedule/" (ev-dt 2026 6 2 14 0))
+                    (quote nia)
+                    (list :rescheduled (quote yoga) (ev-dt 2026 6 2 9 0) (ev-dt 2026 6 2 14 0)))))))
+          ;; an override on an occurrence nobody booked notifies no one
+          (let
+            ((moved2 (ev-with-override ev (ev-dt 2026 6 3 9 0) (ev-dt 2026 6 3 10 0) 60)))
+            (ev-rm-check!
+              "rescheduling an unbooked occurrence notifies no one"
+              (len (ev/reschedule-notifications b moved2))
+              0))
+          ;; an event with no overrides yields no reschedule notifications
+          (ev-rm-check!
+            "event without overrides has no reschedule notifications"
+            (len (ev/reschedule-notifications b ev))
+            0))))))
+
 (define
   ev-reminders-tests-run!
   (fn
@@ -217,4 +272,5 @@
       (set! ev-rm-fail 0)
       (set! ev-rm-failures (list))
       (ev-rm-run-all!)
+      (ev-rm-rs-run-all!)
       {:failures ev-rm-failures :total (+ ev-rm-pass ev-rm-fail) :passed ev-rm-pass :failed ev-rm-fail})))

plans/events-on-sx.md

@@ -18,7 +18,7 @@ capacity rules, transactional booking, and a flow-driven notification dispatcher
 
 ## Status (rolling)
 
-`bash lib/events/conformance.sh` → **265/265** (Phases 1-4 + ext: fed free/busy, waitlist, EXDATE/RDATE, overrides, booking-notify)
+`bash lib/events/conformance.sh` → **272/272** (Phases 1-4 + 6 ext: fed f/b, waitlist, EXDATE/RDATE, overrides, booking-notify, reschedule-notify)
 
 ## Ground rules
 
@@ -86,6 +86,13 @@ lib/events/api.sx ── (events/schedule) (events/book) (events/agenda) ──
 
 ## Progress log
 
+- 2026-06-07 — Reschedule notifications (extension). When an event carries
+  per-occurrence overrides, `ev/reschedule-notifications` reads the roster at
+  each overridden occurrence's ORIGINAL occ-key and produces a reschedule
+  message per booked attendee (old-start, new-start, new-duration). Idempotency
+  key = original-key/reschedule/new-start. `ev/reschedule-notify->msg` for the
+  notify wire shape. Combines overrides (calendar) + rosters (booking) + the
+  message-derivation pattern. +7 tests, 272/272 green.
 - 2026-06-07 — Booking lifecycle notifications (extension). `booking-notify.sx`
   walks the booking stream into ordered notifications classified by kind:
   :booked / :promoted / :held / :confirmed / :released / :cancelled /