1 files changed, 26 insertions, 2 deletions

diff --git a/lib/rites/rite_of/temporal_of.ml b/lib/rites/rite_of/temporal_of.ml
index e375350..1da6cf9 100644
--- a/lib/rites/rite_of/temporal_of.ml
+++ b/lib/rites/rite_of/temporal_of.ml
@@ -532,8 +532,32 @@ let temporal d =
 let anchors y =
   let easter = Computus.gregorian_easter y in
   let off n = Date.add_days easter n in
-  [ ("of-nativity-vigil", mk y 12 24);
-    ("of-nativity", mk y 12 25);
+  (* CORRECTED (celebrant-rubrics-phase1 review, 2026-08-26): this used to
+     list ("of-nativity-vigil", mk y 12 24) UNCONDITIONALLY -- a regression
+     from the earlier R8 fix, which added the Sunday guard to [named]
+     above (Tabula I.2 outranks I.3: on a Sunday, 24 December is the
+     Fourth Sunday of Advent, not the Vigil) but never updated this
+     function to match, so in 2028/2034 this list claimed the Vigil where
+     [temporal] actually returns "of-advent-sunday-4". This module's own
+     doc comment on [anchors] says its whole purpose is to "catch an
+     accidental single-site drift... rather than leaving it invisible" --
+     the irony being that it caught exactly this drift, just years later
+     than it should have, only once Validate.run was wired for the OF rite
+     at all (nothing before that compared [anchors] against [named]/
+     [temporal], so the two were free to disagree unnoticed). The Fourth
+     Sunday of Advent is not added as a replacement entry on a Sunday year:
+     it is an ordinary generic week-numbered Sunday
+     ({!sunday_slug}'s own "of-advent-sunday-4", produced every year
+     regardless of where in the week it falls), never one of the NAMED
+     days this function exists to restate -- see the module doc comment
+     above [anchors] ("Independent restatement of {!named}'s... dates").
+     [named]'s own guard is restated exactly, not re-derived: [named]
+     checks the WEEKDAY of the actual civil date, so this does too, rather
+     than assuming Advent 4 Sunday is always 24 December (it is any Sunday
+     18-24 December; testing the weekday of 24 December itself is exact
+     regardless of which Sunday that turns out to be). *)
+  (if Date.weekday (mk y 12 24) = Date.Sun then [] else [ ("of-nativity-vigil", mk y 12 24) ])
+  @ [ ("of-nativity", mk y 12 25);
     ("of-mary-mother-of-god", mk y 1 1);
     ("of-epiphany", mk y 1 6);
     ("of-holy-family", holy_family y);