Give Prime's Preces the ferial form on Vigil days

isSundayOrFeastOffice treats any sanctoral winner, Vigils included, as a
"feast," so a Vigil day was getting the Sunday/feast Preces. Add a
by-day-kind 'vigilIsFerial' flag, set only on Prime's Preces part (its
capitulum keeps the old behavior), so a Vigil-ranked winner now routes
to the ferial Preces text instead.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HWN869GrMFHqrer9fdCBbF

src/data/hours/prime.yml

@@ -30,6 +30,12 @@
 # ferial Preces are said on *every* ferial day, not just Advent/Lent/
 # vigils/Ember days the way later rubrics restricted them.
 #
+# Preces additionally set `vigilIsFerial: true` — isSundayOrFeastOffice on
+# its own treats any sanctoral winner, Vigils included, as a "feast," but
+# by explicit choice a Vigil day gets the ferial Preces instead. The
+# capitulum doesn't set this flag, so a Vigil still gets the Sunday/feast
+# capitulum, same as before.
+#
 # Preces deliberately use the *secular* Tridentine form
 # (propers/common/prime-preces-dominicales.yml), not Monastic Prime's own
 # shorter Dominicales form — chosen because the secular form keeps content
@@ -65,6 +71,7 @@ parts:
   - kind: by-day-kind
     resolvedKind: preces
     omitOnDouble: true
+    vigilIsFerial: true
     sundayOrFeastRef: { source: common, id: prime-preces-dominicales }
     ferialRef: { source: common, id: prime-preces-feriales }
   - kind: prayer

src/hours/prime.ts

@@ -97,10 +97,13 @@ function resolvePart(part: HourPart, date: string, day: LiturgicalDay): Resolved
     case 'canticle':
       return [{ kind: 'canticle', canticleId: part.canticleId, text: resolveCommon(part.textRef.id) }];
     case 'by-day-kind': {
-      if (part.omitOnDouble && isDoubleOrHigher(resolveOfficeWinner(day))) {
+      const winner = resolveOfficeWinner(day);
+      if (part.omitOnDouble && isDoubleOrHigher(winner)) {
         return [];
       }
-      const ref = isSundayOrFeastOffice(day) ? part.sundayOrFeastRef : part.ferialRef;
+      const isVigil = winner.kind === 'sanctoral' && winner.rank === 'vigil';
+      const useFeastForm = isSundayOrFeastOffice(day) && !(part.vigilIsFerial && isVigil);
+      const ref = useFeastForm ? part.sundayOrFeastRef : part.ferialRef;
       if (part.resolvedKind === 'preces') {
         return [{ kind: 'preces', text: resolveCommon(ref.id), label: part.label }];
       }

src/hours/types.ts

@@ -61,6 +61,12 @@ export type HourPart =
       resolvedKind: 'chapter' | 'preces';
       label?: string;
       omitOnDouble?: true;
+      // When true, a Vigil-ranked sanctoral winner takes the ferialRef
+      // instead of the sundayOrFeastRef isSundayOrFeastOffice would
+      // otherwise give it (that function treats any sanctoral winner,
+      // Vigils included, as a "feast"). Prime's Preces use this; its
+      // capitulum doesn't.
+      vigilIsFerial?: true;
       sundayOrFeastRef: PropersRef;
       ferialRef: PropersRef;
     }

tests/hours/prime.test.ts

@@ -130,6 +130,25 @@ describe('resolveOrdo("prime", ...)', () => {
     ).toContain('Et ego ad te, Dómine, clamávi');
   });
 
+  it('uses the ferial Preces (but the Sunday/feast capitulum) on a Vigil day', () => {
+    // 2025-11-29: a real, unimpeded Vigil of St. Andrew — day.winner is
+    // itself sanctoral/vigil (not merely commemorated), see
+    // data/calendar/saints/vigil-of-st-andrew.yml's own header comment.
+    const VIGIL = '2025-11-29';
+    const ordo = resolveOrdo('prime', VIGIL);
+    const chapter = ordo.parts.find((p) => p.kind === 'chapter');
+    // The capitulum doesn't set vigilIsFerial, so it stays on the
+    // Sunday/feast form even on a Vigil day.
+    expect(chapter && chapter.kind === 'chapter' ? chapter.text.text.en : undefined).toBe(
+      'Now to the king of ages, immortal, invisible, the only God, be honour and glory for ever and ever. Amen.',
+    );
+    const preces = ordo.parts.filter((p) => p.kind === 'preces');
+    const ferialPreces = preces.find((p) => p.kind === 'preces' && p.text.text.la?.startsWith('V. Éripe me'));
+    expect(ferialPreces).toBeDefined();
+    const dominicalPreces = preces.find((p) => p.kind === 'preces' && p.text.text.la?.includes('Confíteor Deo'));
+    expect(dominicalPreces).toBeUndefined();
+  });
+
   it('gives the capitulum its scripture citation', () => {
     const ordo = resolveOrdo('prime', MONDAY);
     const chapter = ordo.parts.find((p) => p.kind === 'chapter');