2 files changed, 64 insertions, 6 deletions
diff --git a/internal/caldata/caldata_test.go b/internal/caldata/caldata_test.go
index 7dbbf84..c0e2d50 100644
--- a/internal/caldata/caldata_test.go
+++ b/internal/caldata/caldata_test.go
@@ -402,3 +402,57 @@ func TestTridentineNamesPreservedAcrossRegeneration(t *testing.T) {
 		t.Errorf("assumption-of-the-blessed-virgin-mary: name.pl = %q, want the preserved Polish name", got)
 	}
 }
+
+// TestTridentineMissalOverrides pins the four fields where the 1962 MISSALE
+// ROMANUM decides against missalemeum, and the Missal wins.
+//
+// This is the safety net for a specific accident. This file is generated by
+// scripts/gen-sanctoral-ef.go from missalemeum, which does NOT carry any of
+// these values; the generator re-applies them from its own missalOverrides
+// table on every run. If that table is ever removed, or a slug is renamed
+// upstream so an override silently stops matching, the generated file quietly
+// reverts to missalemeum's values and nothing else in this repository would
+// notice. This test notices.
+//
+// Each was found by the sibling project colitur, which validates this data
+// against the Missal and its Rubricae Generales rather than against another
+// calendar program:
+//
+//   - ubaldus and didacus: the Missal's own universal calendarium ranks both
+//     "III classis" outright, with no commemoration rubric, and each has a
+//     Mass entry of its own in the Proprium taking its readings from a Common
+//     -- which a bare commemoration never has.
+//   - the two August vigils: RG 128 gives violet to "vigils of II and III
+//     class outside Paschaltide". Both qualify. The rule's sole exception is
+//     the Ascension's vigil, inside Paschaltide, which is white -- and which
+//     is therefore checked here too, in the opposite direction, so that a
+//     careless "make every vigil violet" fix would fail rather than pass.
+func TestTridentineMissalOverrides(t *testing.T) {
+	l := Tridentine()
+	for _, c := range []struct{ slug, field, want, why string }{
+		{"ubaldus", "rank", "class-3", "Missal calendarium: S. Ubaldi Ep. et Conf., III classis"},
+		{"didacus", "rank", "class-3", "Missal calendarium: S. Didaci Conf., III classis"},
+		{"vigil-of-st-lawrence", "colour", "violet", "RG 128: III-class vigil outside Paschaltide"},
+		{"vigil-of-the-assumption", "colour", "violet", "RG 128: II-class vigil outside Paschaltide"},
+	} {
+		rc, ok := l.Cels[c.slug]
+		if !ok {
+			t.Errorf("missing %q -- if the slug was renamed upstream, the generator's "+
+				"missalOverrides entry must be renamed with it, or the correction is lost", c.slug)
+			continue
+		}
+		if got := rc.Fields[c.field]; got != c.want {
+			t.Errorf("%s: %s = %q, want %q (%s). This is a MISSAL correction that "+
+				"missalemeum does not carry -- if it reverted, the generator's "+
+				"missalOverrides table has stopped being applied", c.slug, c.field, got, c.want, c.why)
+		}
+	}
+	// The exception, asserted in the other direction: RG 128's vigil rule is
+	// "outside Paschaltide", and the Ascension's vigil is inside it.
+	if rc, ok := l.Cels["vigil-of-the-ascension"]; ok {
+		if got := rc.Fields["colour"]; got != "" && got != "white" {
+			t.Errorf("vigil-of-the-ascension: colour = %q, want white -- RG 128's "+
+				"violet rule is for vigils OUTSIDE Paschaltide and this one is inside it", got)
+		}
+	}
+}
diff --git a/internal/caldata/tridentine-calendar.ini b/internal/caldata/tridentine-calendar.ini
index 2786125..51b931a 100644
--- a/internal/caldata/tridentine-calendar.ini
+++ b/internal/caldata/tridentine-calendar.ini
@@ -8,12 +8,16 @@
 ; name.<lang> (missalemeum supplies English only) is preserved verbatim from
 ; whatever this file already carried before regeneration. See NOTICE.
 ;
-; NO LONGER PURELY GENERATED -- READ BEFORE RE-RUNNING THE GENERATOR.
-; Four fields below are HAND CORRECTIONS against the 1962 Missale Romanum
-; itself, adopted 2026-08-18 from the sibling project colitur, which validated
-; this data against the Missal and found missalemeum wrong on each. They are
-; NOT in missalemeum and a regeneration WILL SILENTLY REVERT THEM. Re-apply
-; them, or teach the generator to, before committing regenerated output:
+; FOUR FIELDS ARE NOT FROM missalemeum. They are corrections against the 1962
+; Missale Romanum itself, adopted 2026-08-18 from the sibling project colitur,
+; which validated this data against the Missal and found missalemeum wrong on
+; each. missalemeum does not carry them.
+;
+; REGENERATING THIS FILE IS SAFE. gen-sanctoral-ef.go re-applies all four from
+; its own missalOverrides table on every run, and fails loudly rather than
+; silently dropping one whose slug has been renamed upstream.
+; EDITING THEM HERE BY HAND IS NOT SAFE -- the next run puts them back. Change
+; the table. TestTridentineMissalOverrides pins all four either way:
 ;
 ;   [ubaldus]                  rank   commemoration -> class-3
 ;   [didacus]                  rank   commemoration -> class-3