hours: build Terce, Sext, and None

Three separate resolver files (terce.ts/sext.ts/none.ts), not a shared
little-hour module — they're structurally identical but kept independent
by choice. Ordo verified against Divinum Officium (Monastic Tridentinum
1617): opening versicle, self-contained hymn, one antiphon framing three
psalms (no closing repeat, unlike Prime), a capitulum with its own
embedded short versicle/response, the day's own collect, and a closing
identical across all three hours.

Also fills in psalter-distribution.yml's previously-missing Sunday/
Monday/Tuesday psalm entries (Ps 118 sections for Sunday/Monday; Tuesday
turns out to share Wednesday/Thursday's native gradual-psalm set, not a
distinct one). Friday/Saturday's antiphons are derived from each day's
first psalm rather than reusing the native gradual antiphons, since
those two days already use a redistributed, non-native psalm set.

hours/types.ts gains a 'day-collect' part kind — the first ordo to use
the day's own Proper collect rather than a fixed text.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/data/hours/none-antiphons.yml

@@ -0,0 +1,19 @@
+# See terce-antiphons.yml for the full explanation of this table's shape,
+# sourcing, and the Friday/Saturday derivation caveat.
+sunday:
+  la: "Allelúja."
+  en: "Alleluia."
+monday:
+  la: "Fiat manus tua."
+  en: "Let thy hand be with me to save me."
+tuesday: &gradual-none-ant
+  la: "Beáti omnes."
+  en: "Blessed are all they."
+wednesday: *gradual-none-ant
+thursday: *gradual-none-ant
+friday:
+  la: "Si vere útique justítiam loquímini."
+  en: "If in very deed you speak justice."
+saturday:
+  la: "Dóminus regnávit."
+  en: "The Lord hath reigned."

src/data/hours/none.yml

@@ -0,0 +1,16 @@
+# See terce.yml for the full explanation of this ordo's structure and
+# deliberate deviations — None is identical in shape, only its hymn,
+# antiphon/psalms, and capitulum differ.
+id: none
+parts:
+  - kind: opening-versicle
+  - kind: hymn
+    textRef: { source: common, id: none-hymn }
+  - kind: variable
+    resolve: by-weekday
+  - kind: chapter
+    textRef: { source: common, id: none-capitulum-per-annum }
+  - kind: day-collect
+  - kind: preces
+    textRef: { source: common, id: little-hour-conclusio }
+    label: Conclusion

src/data/hours/sext-antiphons.yml

@@ -0,0 +1,19 @@
+# See terce-antiphons.yml for the full explanation of this table's shape,
+# sourcing, and the Friday/Saturday derivation caveat.
+sunday:
+  la: "Allelúja."
+  en: "Alleluia."
+monday:
+  la: "Áspice in me."
+  en: "Look upon me."
+tuesday: &gradual-sext-ant
+  la: "Qui hábitas."
+  en: "Who dwellest."
+wednesday: *gradual-sext-ant
+thursday: *gradual-sext-ant
+friday:
+  la: "Quid gloriáris in malítia."
+  en: "Why dost thou glory in malice."
+saturday:
+  la: "Fundaménta ejus in móntibus sanctis."
+  en: "The foundations thereof are in the holy mountains."

src/data/hours/sext.yml

@@ -0,0 +1,16 @@
+# See terce.yml for the full explanation of this ordo's structure and
+# deliberate deviations — Sext is identical in shape, only its hymn,
+# antiphon/psalms, and capitulum differ.
+id: sext
+parts:
+  - kind: opening-versicle
+  - kind: hymn
+    textRef: { source: common, id: sext-hymn }
+  - kind: variable
+    resolve: by-weekday
+  - kind: chapter
+    textRef: { source: common, id: sext-capitulum-per-annum }
+  - kind: day-collect
+  - kind: preces
+    textRef: { source: common, id: little-hour-conclusio }
+    label: Conclusion

src/data/hours/terce-antiphons.yml

@@ -0,0 +1,38 @@
+# One antiphon per weekday, framing that day's whole psalm group (see
+# hours/terce.ts and psalter/distribution.ts's 'terce' table) — same shape
+# and convention as data/hours/prime-antiphons.yml (inline text, no
+# separate common-propers id, incipit/full split via an embedded "*" where
+# the source has one). None of these happen to have a "*" — each is a
+# short single-clause antiphon and splitAntiphon() already degrades
+# gracefully (incipit == full) when there isn't one.
+#
+# Verified against Divinum Officium (Monastic Tridentinum 1617):
+#   - sunday/monday/tuesday: clean per-annum runs with no sanctoral
+#     override (2026-08-09 Sun, 2026-08-31 Mon, 2026-10-13 Tue).
+#   - wednesday/thursday: share Tuesday's antiphon — same native psalms
+#     (119-121), confirmed identical across all three.
+#   - friday/saturday: these two days' psalms were editorially
+#     redistributed (see psalter-distribution.yml's long comment on
+#     'terce'), so there's no real historical antiphon for this specific
+#     grouping. Per explicit decision, each is instead derived from the
+#     opening phrase of that day's first psalm (Ps 41 for Friday, Ps 69 for
+#     Saturday) — editorial, not independently verified against the
+#     reference engine as a real antiphon, same caveat as the
+#     redistribution itself.
+sunday:
+  la: "Allelúja."
+  en: "Alleluia."
+monday:
+  la: "Ádjuva me."
+  en: "Help me."
+tuesday: &gradual-terce-ant
+  la: "Clamávi."
+  en: "I cried unto the Lord."
+wednesday: *gradual-terce-ant
+thursday: *gradual-terce-ant
+friday:
+  la: "Quemádmodum desíderat cervus."
+  en: "As the hart panteth."
+saturday:
+  la: "Deus, in adjutórium meum inténde."
+  en: "O God, come to my assistance."

src/data/hours/terce.yml

@@ -0,0 +1,29 @@
+# Ordo verified against Divinum Officium (Monastic Tridentinum 1617), clean
+# per-annum runs with no sanctoral override (2026-08-09 Sun, 2026-08-31 Mon,
+# 2026-10-13 Tue) — see src/hours/terce.ts for how each part resolves.
+#
+# Deliberately deviates from that verified source in one place, matching
+# Prime's own precedent: the opening Pater/Ave (said silently before "Deus
+# in adjutórium") is dropped, to keep the hour shorter.
+#
+# Real structure, confirmed directly against the engine: opening versicle,
+# hymn (self-contained, no seasonal doxology swap — see terce-hymn.yml),
+# one antiphon framing all three psalms, capitulum with its own embedded
+# short versicle/response (*not* a separate elaborate responsory the way
+# Prime's chapter-responsory.ts adds one — Monastic Terce doesn't have
+# one), the day's own collect, and a closing that's identical across all
+# three Little Hours (see little-hour-conclusio.yml). No Preces, no Creed —
+# real Monastic Terce/Sext/None have neither.
+id: terce
+parts:
+  - kind: opening-versicle
+  - kind: hymn
+    textRef: { source: common, id: terce-hymn }
+  - kind: variable
+    resolve: by-weekday
+  - kind: chapter
+    textRef: { source: common, id: terce-capitulum-per-annum }
+  - kind: day-collect
+  - kind: preces
+    textRef: { source: common, id: little-hour-conclusio }
+    label: Conclusion

src/data/propers/common/little-hour-conclusio.yml

@@ -0,0 +1,23 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617), clean
+# per-annum run (2026-08-31) — identical across Terce, Sext, and None
+# (confirmed by comparing all three directly), unlike Prime's/Compline's
+# own distinct conclusios.
+id: little-hour-conclusio
+text:
+  la: |
+    V. Dómine, exáudi oratiónem meam.
+    R. Et clamor meus ad te véniat.
+    V. Benedicámus Dómino.
+    R. Deo grátias.
+    V. Fidélium ánimæ per misericórdiam Dei requiéscant in pace.
+    R. Amen.
+  en: |
+    V. O Lord, hear my prayer.
+    R. And let my cry come unto thee.
+    V. Let us bless the Lord.
+    R. Thanks be to God.
+    V. May the souls of the faithful, through the mercy of God, rest in peace.
+    R. Amen.
+status:
+  la: verified
+  en: verified

src/data/propers/common/none-capitulum-per-annum.yml

@@ -0,0 +1,13 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617), clean
+# per-annum run (2026-08-31). See terce-capitulum-per-annum.yml for the
+# combined-block structure note and the deferred-seasonal-variant caveat.
+id: none-capitulum-per-annum
+text:
+  la: "Empti enim estis prétio magno. Glorificáte et portáte Deum in córpore vestro. R. Deo grátias. V. Ab occúltis meis munda me, Dómine. R. Et ab aliénis parce servo tuo."
+  en: "For you are bought with a great price. Glorify and bear God in your body. R. Thanks be to God. V. From my secret ones cleanse me, O Lord. R. And from those of others spare thy servant."
+citation:
+  la: "1 Cor. 6:20"
+  en: "1 Cor. 6:20"
+status:
+  la: verified
+  en: verified

src/data/propers/common/sext-capitulum-per-annum.yml

@@ -0,0 +1,13 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617), clean
+# per-annum run (2026-08-31). See terce-capitulum-per-annum.yml for the
+# combined-block structure note and the deferred-seasonal-variant caveat.
+id: sext-capitulum-per-annum
+text:
+  la: "Alter altérius ónera portáte, et sic adimplébitis legem Christi. R. Deo grátias. V. Dóminus regit me, et nihil mihi déerit. R. In loco páscuæ ibi me collocávit."
+  en: "Bear ye one another's burdens; and so you shall fulfill the law of Christ. R. Thanks be to God. V. The Lord ruleth me: and I shall want nothing. R. He hath set me in a place of pasture."
+citation:
+  la: "Gal. 6:2"
+  en: "Gal. 6:2"
+status:
+  la: verified
+  en: verified

src/data/propers/common/terce-capitulum-per-annum.yml

@@ -0,0 +1,20 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617), clean
+# per-annum runs (2026-08-31, a Monday with no sanctoral override — see
+# hours/terce.ts). "Capitulum Versus" in the source is one combined block:
+# the chapter, then R. Deo grátias, then a short versicle/response pair —
+# unlike Prime, the Little Hours have no separate elaborate short
+# responsory, so all of that is kept together here as one 'chapter' part.
+#
+# Per-annum only for now — real practice varies this by season (confirmed
+# by comparing against a Lenten Ember Wednesday run, which showed different
+# capitulum text entirely), but that seasonal table isn't built yet.
+id: terce-capitulum-per-annum
+text:
+  la: "Sana me, Dómine, et sanábor: salvum me fac, et salvus ero: quóniam laus mea tu es. R. Deo grátias. V. Adjútor meus, esto, ne derelínquas me. R. Neque despícias me, Deus, salutáris meus."
+  en: "Heal me, O Lord, and I shall be healed: save me, and I shall be saved, for thou art my praise. R. Thanks be to God. V. Be thou my helper, forsake me not. R. Do not thou despise me, O God my Saviour."
+citation:
+  la: "Jer. 17:14"
+  en: "Jer. 17:14"
+status:
+  la: verified
+  en: verified

src/data/psalter-distribution.yml

@@ -78,9 +78,9 @@ prime:
 #
 # Sunday, Monday, and Tuesday's Terce/Sext/None are untouched by any of
 # this (still whatever Divinum Officium gives natively — Ps 118 sections
-# for Sunday/Monday, 119-127 for Tuesday) and so aren't recorded here;
-# source them from the reference engine directly when those hours are
-# built, the same as Wednesday/Thursday's unchanged 119-127 below.
+# for Sunday/Monday, 119-127 for Tuesday) — now recorded below, verified
+# against clean per-annum runs with no sanctoral override (2026-08-09 Sun,
+# 2026-08-31 Mon, 2026-10-13 Tue).
 matins:
   monday:
     - { number: 32 }
@@ -147,10 +147,19 @@ matins:
   # redistribution; source it directly from the reference engine.
 
 terce:
-  wednesday: &gradual-terce
+  sunday:
+    - { number: 118, verses: "33-40" }
+    - { number: 118, verses: "41-48" }
+    - { number: 118, verses: "49-56" }
+  monday:
+    - { number: 118, verses: "105-112" }
+    - { number: 118, verses: "113-120" }
+    - { number: 118, verses: "121-128" }
+  tuesday: &gradual-terce
     - { number: 119 }
     - { number: 120 }
     - { number: 121 }
+  wednesday: *gradual-terce
   thursday: *gradual-terce
   friday:
     - { number: 41 }
@@ -162,10 +171,19 @@ terce:
     - { number: 81 }
 
 sext:
-  wednesday: &gradual-sext
+  sunday:
+    - { number: 118, verses: "57-64" }
+    - { number: 118, verses: "65-72" }
+    - { number: 118, verses: "73-80" }
+  monday:
+    - { number: 118, verses: "129-136" }
+    - { number: 118, verses: "137-144" }
+    - { number: 118, verses: "145-152" }
+  tuesday: &gradual-sext
     - { number: 122 }
     - { number: 123 }
     - { number: 124 }
+  wednesday: *gradual-sext
   thursday: *gradual-sext
   friday:
     - { number: 51 }
@@ -177,10 +195,19 @@ sext:
     - { number: 97 }
 
 none:
-  wednesday: &gradual-none
+  sunday:
+    - { number: 118, verses: "81-88" }
+    - { number: 118, verses: "89-96" }
+    - { number: 118, verses: "97-104" }
+  monday:
+    - { number: 118, verses: "153-160" }
+    - { number: 118, verses: "161-168" }
+    - { number: 118, verses: "169-176" }
+  tuesday: &gradual-none
     - { number: 125 }
     - { number: 126 }
     - { number: 127 }
+  wednesday: *gradual-none
   thursday: *gradual-none
   friday:
     - { number: 57 }

src/hours/compline.ts

@@ -85,6 +85,7 @@ function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
     case 'closing-antiphon':
     case 'by-day-kind':
     case 'variable':
+    case 'day-collect':
       throw new Error(`Compline's ordo doesn't support a '${part.kind}' part`);
   }
 }

src/hours/none.ts

@@ -1,7 +1,65 @@
-import type { ResolvedOrdo } from './types';
+import type { HourDefinition, HourPart, ResolvedOrdo, ResolvedPart } from './types';
+import type { LiturgicalDay, Weekday } from '../calendar/types';
+import { resolveDay } from '../calendar';
+import { getDayLabel } from '../calendar/day-label';
+import { getPsalmsFor } from '../psalter/distribution';
+import { getPsalmVerses } from '../psalter';
+import { getOpeningVersicleId } from './opening-versicle';
+import { isDoubleOrHigher } from './antiphon';
+import { resolveCommon, getDayCollect, splitNamedAntiphon } from './resolve-common';
+import noneDefinitionData from '../data/hours/none.yml';
+import antiphonsData from '../data/hours/none-antiphons.yml';
 
-// Milestone 3. Not built yet — will call into hours/shared/little-hour-shared.ts
-// alongside terce.ts and sext.ts once that's written.
-export function resolveOrdo(date: string): ResolvedOrdo {
-  return { hourId: 'none', date, parts: [], notImplemented: true };
+const noneDefinition = noneDefinitionData as HourDefinition;
+const antiphons = antiphonsData as Record<Weekday, Partial<Record<string, string>>>;
+
+function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
+  switch (part.kind) {
+    case 'opening-versicle':
+      return [{ kind: 'versicle', text: resolveCommon(getOpeningVersicleId(day.season, day.winner)) }];
+    case 'hymn':
+      // Self-contained, no appendDoxology — see none-hymn.yml.
+      return [{ kind: 'hymn', text: resolveCommon(part.textRef.id) }];
+    case 'chapter':
+      return [{ kind: 'chapter', text: resolveCommon(part.textRef.id) }];
+    case 'day-collect':
+      return [{ kind: 'prayer', text: getDayCollect(day) }];
+    case 'preces':
+      return [{ kind: 'preces', text: resolveCommon(part.textRef.id), label: part.label }];
+    case 'variable': {
+      // Only 'by-weekday' applies here — one antiphon framing all three
+      // psalms, no closing repeat (unlike Prime): confirmed directly
+      // against the engine, Capitulum follows the third psalm immediately.
+      const psalmRefs = getPsalmsFor('none', day.weekday);
+      const { incipit, full } = splitNamedAntiphon(antiphons[day.weekday]);
+      const opening = isDoubleOrHigher(day.winner) ? full : incipit;
+      return psalmRefs.map((ref, i) => ({
+        kind: 'psalm' as const,
+        psalmNumber: ref.number,
+        antiphon: i === 0 ? opening : undefined,
+        verses: getPsalmVerses(ref.number, ref.verses).map((v) => ({ n: v.n, text: v.text, status: v.status })),
+      }));
+    }
+    // Not used by None.
+    case 'prayer':
+    case 'responsory':
+    case 'versicle':
+    case 'psalm':
+    case 'canticle':
+    case 'lesson':
+    case 'martyrology':
+    case 'rule-reading':
+    case 'by-day-kind':
+    case 'creed':
+    case 'closing-antiphon':
+    case 'nunc-dimittis':
+    case 'marian-antiphon':
+      throw new Error(`None's ordo doesn't support a '${part.kind}' part`);
+  }
+}
+
+export function resolveOrdo(date: string): ResolvedOrdo {
+  const day = resolveDay(date);
+  const parts = noneDefinition.parts.flatMap((part) => resolvePart(part, day));
+  return { hourId: 'none', date, parts, dayLabel: getDayLabel(day) };
 }

src/hours/prime.ts

@@ -108,9 +108,10 @@ function resolvePart(part: HourPart, date: string, day: LiturgicalDay): Resolved
         { kind: 'preces', text: resolveCommon('lesson-close') },
       ];
     }
-    // Not used by Prime — Compline-only.
+    // Not used by Prime — Compline-only, or Little-Hours-only.
     case 'nunc-dimittis':
     case 'marian-antiphon':
+    case 'day-collect':
       throw new Error(`Prime's ordo doesn't support a '${part.kind}' part`);
   }
 }

src/hours/sext.ts

@@ -1,7 +1,65 @@
-import type { ResolvedOrdo } from './types';
+import type { HourDefinition, HourPart, ResolvedOrdo, ResolvedPart } from './types';
+import type { LiturgicalDay, Weekday } from '../calendar/types';
+import { resolveDay } from '../calendar';
+import { getDayLabel } from '../calendar/day-label';
+import { getPsalmsFor } from '../psalter/distribution';
+import { getPsalmVerses } from '../psalter';
+import { getOpeningVersicleId } from './opening-versicle';
+import { isDoubleOrHigher } from './antiphon';
+import { resolveCommon, getDayCollect, splitNamedAntiphon } from './resolve-common';
+import sextDefinitionData from '../data/hours/sext.yml';
+import antiphonsData from '../data/hours/sext-antiphons.yml';
 
-// Milestone 3. Not built yet — will call into hours/shared/little-hour-shared.ts
-// alongside terce.ts and none.ts once that's written.
-export function resolveOrdo(date: string): ResolvedOrdo {
-  return { hourId: 'sext', date, parts: [], notImplemented: true };
+const sextDefinition = sextDefinitionData as HourDefinition;
+const antiphons = antiphonsData as Record<Weekday, Partial<Record<string, string>>>;
+
+function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
+  switch (part.kind) {
+    case 'opening-versicle':
+      return [{ kind: 'versicle', text: resolveCommon(getOpeningVersicleId(day.season, day.winner)) }];
+    case 'hymn':
+      // Self-contained, no appendDoxology — see sext-hymn.yml.
+      return [{ kind: 'hymn', text: resolveCommon(part.textRef.id) }];
+    case 'chapter':
+      return [{ kind: 'chapter', text: resolveCommon(part.textRef.id) }];
+    case 'day-collect':
+      return [{ kind: 'prayer', text: getDayCollect(day) }];
+    case 'preces':
+      return [{ kind: 'preces', text: resolveCommon(part.textRef.id), label: part.label }];
+    case 'variable': {
+      // Only 'by-weekday' applies here — one antiphon framing all three
+      // psalms, no closing repeat (unlike Prime): confirmed directly
+      // against the engine, Capitulum follows the third psalm immediately.
+      const psalmRefs = getPsalmsFor('sext', day.weekday);
+      const { incipit, full } = splitNamedAntiphon(antiphons[day.weekday]);
+      const opening = isDoubleOrHigher(day.winner) ? full : incipit;
+      return psalmRefs.map((ref, i) => ({
+        kind: 'psalm' as const,
+        psalmNumber: ref.number,
+        antiphon: i === 0 ? opening : undefined,
+        verses: getPsalmVerses(ref.number, ref.verses).map((v) => ({ n: v.n, text: v.text, status: v.status })),
+      }));
+    }
+    // Not used by Sext.
+    case 'prayer':
+    case 'responsory':
+    case 'versicle':
+    case 'psalm':
+    case 'canticle':
+    case 'lesson':
+    case 'martyrology':
+    case 'rule-reading':
+    case 'by-day-kind':
+    case 'creed':
+    case 'closing-antiphon':
+    case 'nunc-dimittis':
+    case 'marian-antiphon':
+      throw new Error(`Sext's ordo doesn't support a '${part.kind}' part`);
+  }
+}
+
+export function resolveOrdo(date: string): ResolvedOrdo {
+  const day = resolveDay(date);
+  const parts = sextDefinition.parts.flatMap((part) => resolvePart(part, day));
+  return { hourId: 'sext', date, parts, dayLabel: getDayLabel(day) };
 }

src/hours/terce.ts

@@ -1,7 +1,65 @@
-import type { ResolvedOrdo } from './types';
+import type { HourDefinition, HourPart, ResolvedOrdo, ResolvedPart } from './types';
+import type { LiturgicalDay, Weekday } from '../calendar/types';
+import { resolveDay } from '../calendar';
+import { getDayLabel } from '../calendar/day-label';
+import { getPsalmsFor } from '../psalter/distribution';
+import { getPsalmVerses } from '../psalter';
+import { getOpeningVersicleId } from './opening-versicle';
+import { isDoubleOrHigher } from './antiphon';
+import { resolveCommon, getDayCollect, splitNamedAntiphon } from './resolve-common';
+import terceDefinitionData from '../data/hours/terce.yml';
+import antiphonsData from '../data/hours/terce-antiphons.yml';
 
-// Milestone 3. Not built yet — will call into hours/shared/little-hour-shared.ts
-// alongside sext.ts and none.ts once that's written.
-export function resolveOrdo(date: string): ResolvedOrdo {
-  return { hourId: 'terce', date, parts: [], notImplemented: true };
+const terceDefinition = terceDefinitionData as HourDefinition;
+const antiphons = antiphonsData as Record<Weekday, Partial<Record<string, string>>>;
+
+function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
+  switch (part.kind) {
+    case 'opening-versicle':
+      return [{ kind: 'versicle', text: resolveCommon(getOpeningVersicleId(day.season, day.winner)) }];
+    case 'hymn':
+      // Self-contained, no appendDoxology — see terce-hymn.yml.
+      return [{ kind: 'hymn', text: resolveCommon(part.textRef.id) }];
+    case 'chapter':
+      return [{ kind: 'chapter', text: resolveCommon(part.textRef.id) }];
+    case 'day-collect':
+      return [{ kind: 'prayer', text: getDayCollect(day) }];
+    case 'preces':
+      return [{ kind: 'preces', text: resolveCommon(part.textRef.id), label: part.label }];
+    case 'variable': {
+      // Only 'by-weekday' applies here — one antiphon framing all three
+      // psalms, no closing repeat (unlike Prime): confirmed directly
+      // against the engine, Capitulum follows the third psalm immediately.
+      const psalmRefs = getPsalmsFor('terce', day.weekday);
+      const { incipit, full } = splitNamedAntiphon(antiphons[day.weekday]);
+      const opening = isDoubleOrHigher(day.winner) ? full : incipit;
+      return psalmRefs.map((ref, i) => ({
+        kind: 'psalm' as const,
+        psalmNumber: ref.number,
+        antiphon: i === 0 ? opening : undefined,
+        verses: getPsalmVerses(ref.number, ref.verses).map((v) => ({ n: v.n, text: v.text, status: v.status })),
+      }));
+    }
+    // Not used by Terce.
+    case 'prayer':
+    case 'responsory':
+    case 'versicle':
+    case 'psalm':
+    case 'canticle':
+    case 'lesson':
+    case 'martyrology':
+    case 'rule-reading':
+    case 'by-day-kind':
+    case 'creed':
+    case 'closing-antiphon':
+    case 'nunc-dimittis':
+    case 'marian-antiphon':
+      throw new Error(`Terce's ordo doesn't support a '${part.kind}' part`);
+  }
+}
+
+export function resolveOrdo(date: string): ResolvedOrdo {
+  const day = resolveDay(date);
+  const parts = terceDefinition.parts.flatMap((part) => resolvePart(part, day));
+  return { hourId: 'terce', date, parts, dayLabel: getDayLabel(day) };
 }

src/hours/types.ts

@@ -87,7 +87,13 @@ export type HourPart =
   // Salve Regina. See hours/marian-antiphon.ts.
   | { kind: 'marian-antiphon' }
   // Unused by Prime/Compline/the little hours — exercised starting milestone 4.
-  | { kind: 'variable'; resolve: 'by-weekday' | 'by-season' | 'by-feast-rank' };
+  | { kind: 'variable'; resolve: 'by-weekday' | 'by-season' | 'by-feast-rank' }
+  // The day's own Proper-of-season/Proper-of-saints collect — resolved by
+  // day, not by textRef. First used by the Little Hours' "Oratio {ex
+  // Proprio de Tempore}" via hours/resolve-common.ts's getDayCollect;
+  // Prime/Compline both still use a fixed collect (`prayer` + textRef).
+  // Renders as a plain 'prayer' ResolvedPart.
+  | { kind: 'day-collect' };
 
 export interface HourDefinition {
   id: HourId;