diff --git a/src/data/hours/lauds.yml b/src/data/hours/lauds.yml
new file mode 100644
index 0000000..b09dbdf
--- /dev/null
+++ b/src/data/hours/lauds.yml
@@ -0,0 +1,25 @@
+# Ordo verified against Divinum Officium (Monastic Tridentinum 1617), Lauds
+# live query, 2026-08-11 — see src/hours/lauds.ts for how each part
+# resolves, and data/hours/lauds-antiphons.yml / lauds-canticles/*.yml /
+# propers/common/lauds-*.yml for the underlying weekday content.
+#
+# The suffrages (Holy Cross, BVM, Ss. Peter & Paul, Peace) are gated by
+# omitOnDouble — see hours/types.ts's 'suffrages' doc comment for the
+# caveat on what else real practice also suppresses them for that isn't
+# modeled yet.
+id: lauds
+parts:
+  - kind: opening-versicle
+  - kind: lauds-psalmody
+  - kind: lauds-office
+  - kind: benedictus
+  - kind: preces
+    textRef: { source: common, id: lauds-short-litany }
+  - kind: day-collects
+  - kind: suffrages
+    omitOnDouble: true
+  - kind: preces
+    textRef: { source: common, id: lauds-conclusio }
+  - kind: versicle
+    textRef: { source: common, id: lauds-closing-versicle }
+  - kind: marian-antiphon
diff --git a/src/hours/compline.ts b/src/hours/compline.ts
index 77e686c..02dacb5 100644
--- a/src/hours/compline.ts
+++ b/src/hours/compline.ts
@@ -86,6 +86,11 @@ function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
     case 'by-day-kind':
     case 'variable':
     case 'day-collect':
+    case 'lauds-psalmody':
+    case 'lauds-office':
+    case 'benedictus':
+    case 'suffrages':
+    case 'day-collects':
       throw new Error(`Compline's ordo doesn't support a '${part.kind}' part`);
   }
 }
diff --git a/src/hours/lauds.ts b/src/hours/lauds.ts
index b0baf79..7c79b09 100644
--- a/src/hours/lauds.ts
+++ b/src/hours/lauds.ts
@@ -1,7 +1,192 @@
-import type { ResolvedOrdo } from './types';
+import type { HourDefinition, HourPart, ResolvedOrdo, ResolvedPart, ResolvedText } from './types';
+import type { LiturgicalDay, Weekday } from '../calendar/types';
+import { resolveDay } from '../calendar';
+import { getDayLabel } from '../calendar/day-label';
+import { getPsalmVerses } from '../psalter';
+import { getCanticle } from './lauds-canticles';
+import { getOpeningVersicleId } from './opening-versicle';
+import { getMarianAntiphonId, getMarianAntiphonLabel } from './marian-antiphon';
+import { isDoubleOrHigher } from './antiphon';
+import { resolveCommon, getDayCollects, getBenedictusAntiphon, splitNamedAntiphon } from './resolve-common';
+import laudsDefinitionData from '../data/hours/lauds.yml';
+import laudsAntiphonsData from '../data/hours/lauds-antiphons.yml';
 
-// Milestone 4 — first hour needing real sanctoral occurrence + rank/commemoration
-// resolution (calendar/feasts.ts, calendar/easter.ts). Not built yet.
-export function resolveOrdo(date: string): ResolvedOrdo {
-  return { hourId: 'lauds', date, parts: [], notImplemented: true };
+const laudsDefinition = laudsDefinitionData as HourDefinition;
+
+type BilingualText = Partial<Record<string, string>>;
+interface LaudsGroup {
+  psalms: number[];
+  antiphon: BilingualText;
+}
+interface LaudsWeekdayAntiphons {
+  groups: LaudsGroup[];
+  canticle: { id: string; antiphon: BilingualText };
+  laudate: { antiphon: BilingualText };
+}
+const laudsAntiphons = laudsAntiphonsData as Record<Weekday, LaudsWeekdayAntiphons>;
+
+// Mon-Fri share one capitulum verbatim (confirmed against the live engine
+// — see lauds-capitulum-ferial.yml); Sunday and Saturday each have their
+// own.
+function capitulumId(weekday: Weekday): string {
+  if (weekday === 'sunday') {
+    return 'lauds-capitulum-sunday';
+  }
+  if (weekday === 'saturday') {
+    return 'lauds-capitulum-saturday';
+  }
+  return 'lauds-capitulum-ferial';
+}
+
+function psalmParts(numbers: number[], antiphon: BilingualText, opening: ResolvedText): ResolvedPart[] {
+  const parts: ResolvedPart[] = numbers.map((number, i) => ({
+    kind: 'psalm' as const,
+    psalmNumber: number,
+    antiphon: i === 0 ? opening : undefined,
+    verses: getPsalmVerses(number).map((v) => ({ n: v.n, text: v.text, status: v.status })),
+  }));
+  parts.push({ kind: 'antiphon', text: splitNamedAntiphon(antiphon).full });
+  return parts;
+}
+
+const STATUS_RANK = { verified: 0, draft: 1, missing: 2 } as const;
+
+/** Joins a canticle's verse array into one flowing text block, the same
+ * shape nunc-dimittis/benedictus already use — Lauds' weekday canticles
+ * are stored verse-by-verse (see lauds-canticles.ts) purely because that's
+ * how they were transcribed, not because callers need per-verse access.
+ * Appends the fixed Gloria Patri line every canticle ends with in real
+ * practice, same wording as benedictus.yml's own trailing line. */
+function canticleText(canticleId: string): ResolvedText {
+  const canticle = getCanticle(canticleId);
+  const text: Partial<Record<string, string>> = {};
+  const status: Partial<Record<string, 'verified' | 'draft' | 'missing'>> = {};
+  const GLORIA = {
+    la: 'V. Glória Patri, et Fílio, * et Spirítui Sancto.\nR. Sicut erat in princípio, et nunc, et semper, * et in sǽcula sæculórum. Amen.',
+    en: 'V. Glory be to the Father, and to the Son, * and to the Holy Ghost.\nR. As it was in the beginning, is now, * and ever shall be, world without end. Amen.',
+  };
+  for (const lang of ['la', 'en'] as const) {
+    const lines = canticle.verses.map((v) => v.text[lang]).filter((t): t is string => Boolean(t));
+    if (lines.length === 0) {
+      continue;
+    }
+    text[lang] = `${lines.join('\n')}\n${GLORIA[lang]}`;
+    let worst: 'verified' | 'draft' | 'missing' = 'verified';
+    for (const v of canticle.verses) {
+      const s = v.status[lang] ?? 'missing';
+      if (STATUS_RANK[s] > STATUS_RANK[worst]) {
+        worst = s;
+      }
+    }
+    status[lang] = worst;
+  }
+  return { text, status };
+}
+
+/** Ps 66 through the Laudate psalms — see hours/types.ts's 'lauds-psalmody'
+ * doc comment for the scope and the known Commune-override gap. */
+function resolvePsalmody(day: LiturgicalDay): ResolvedPart[] {
+  const wd = laudsAntiphons[day.weekday];
+  const opening = (antiphon: BilingualText) => {
+    const { incipit, full } = splitNamedAntiphon(antiphon);
+    return isDoubleOrHigher(day.winner) ? full : incipit;
+  };
+  const parts: ResolvedPart[] = [
+    {
+      kind: 'psalm',
+      psalmNumber: 66,
+      verses: getPsalmVerses(66).map((v) => ({ n: v.n, text: v.text, status: v.status })),
+    },
+  ];
+  for (const group of wd.groups) {
+    parts.push(...psalmParts(group.psalms, group.antiphon, opening(group.antiphon)));
+  }
+  const canticle = getCanticle(wd.canticle.id);
+  parts.push({
+    kind: 'canticle',
+    canticleId: canticle.id,
+    antiphon: opening(wd.canticle.antiphon),
+    text: canticleText(canticle.id),
+  });
+  parts.push({ kind: 'antiphon', text: splitNamedAntiphon(wd.canticle.antiphon).full });
+  parts.push(...psalmParts([148, 149, 150], wd.laudate.antiphon, opening(wd.laudate.antiphon)));
+  return parts;
+}
+
+function resolveOffice(weekday: Weekday): ResolvedPart[] {
+  return [
+    { kind: 'chapter', text: resolveCommon(capitulumId(weekday)) },
+    { kind: 'responsory', text: resolveCommon(`lauds-responsory-${weekday}`) },
+    { kind: 'hymn', text: resolveCommon(`lauds-hymn-${weekday}`) },
+    { kind: 'versicle', text: resolveCommon(`lauds-versicle-${weekday}`) },
+  ];
+}
+
+const SUFFRAGES = ['lauds-suffrage-cross', 'lauds-suffrage-bvm', 'lauds-suffrage-apostles', 'lauds-suffrage-peace'];
+const SUFFRAGE_LABELS: Record<string, string> = {
+  'lauds-suffrage-cross': 'Of the Holy Cross',
+  'lauds-suffrage-bvm': 'Of the Blessed Virgin Mary',
+  'lauds-suffrage-apostles': 'Of the Holy Apostles Peter and Paul',
+  'lauds-suffrage-peace': 'For Peace',
+};
+
+function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
+  switch (part.kind) {
+    case 'opening-versicle':
+      return [{ kind: 'versicle', text: resolveCommon(getOpeningVersicleId(day.season, day.winner)) }];
+    case 'lauds-psalmody':
+      return resolvePsalmody(day);
+    case 'lauds-office':
+      return resolveOffice(day.weekday);
+    case 'benedictus': {
+      const { incipit, full } = splitNamedAntiphon(getBenedictusAntiphon(day).text);
+      const opening = isDoubleOrHigher(day.winner) ? full : incipit;
+      return [
+        { kind: 'canticle', canticleId: 'benedictus', text: resolveCommon('benedictus'), antiphon: opening },
+        { kind: 'antiphon', text: full },
+      ];
+    }
+    case 'preces':
+      return [{ kind: 'preces', text: resolveCommon(part.textRef.id), label: part.label }];
+    case 'day-collects':
+      return getDayCollects(day).map((text) => ({ kind: 'prayer' as const, text }));
+    case 'suffrages':
+      if (part.omitOnDouble && isDoubleOrHigher(day.winner)) {
+        return [];
+      }
+      return SUFFRAGES.map((id) => ({
+        kind: 'preces' as const,
+        text: resolveCommon(id),
+        label: SUFFRAGE_LABELS[id],
+      }));
+    case 'versicle':
+    case 'chapter':
+    case 'responsory':
+    case 'prayer':
+      return [{ kind: part.kind, text: resolveCommon(part.textRef.id) }];
+    case 'marian-antiphon': {
+      const id = getMarianAntiphonId(day);
+      return [{ kind: 'preces', text: resolveCommon(id), label: getMarianAntiphonLabel(id) }];
+    }
+    // Not used by Lauds.
+    case 'hymn':
+    case 'lesson':
+    case 'psalm':
+    case 'canticle':
+    case 'martyrology':
+    case 'rule-reading':
+    case 'creed':
+    case 'closing-antiphon':
+    case 'by-day-kind':
+    case 'variable':
+    case 'day-collect':
+    case 'nunc-dimittis':
+      throw new Error(`Lauds' ordo doesn't support a '${part.kind}' part`);
+  }
+}
+
+export function resolveOrdo(date: string): ResolvedOrdo {
+  const day = resolveDay(date);
+  const parts = laudsDefinition.parts.flatMap((part) => resolvePart(part, day));
+  return { hourId: 'lauds', date, parts, dayLabel: getDayLabel(day) };
 }
diff --git a/src/hours/none.ts b/src/hours/none.ts
index 7b5d77a..502ab28 100644
--- a/src/hours/none.ts
+++ b/src/hours/none.ts
@@ -54,6 +54,11 @@ function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
     case 'closing-antiphon':
     case 'nunc-dimittis':
     case 'marian-antiphon':
+    case 'lauds-psalmody':
+    case 'lauds-office':
+    case 'benedictus':
+    case 'suffrages':
+    case 'day-collects':
       throw new Error(`None's ordo doesn't support a '${part.kind}' part`);
   }
 }
diff --git a/src/hours/prime.ts b/src/hours/prime.ts
index 5504eec..30b93be 100644
--- a/src/hours/prime.ts
+++ b/src/hours/prime.ts
@@ -112,6 +112,11 @@ function resolvePart(part: HourPart, date: string, day: LiturgicalDay): Resolved
     case 'nunc-dimittis':
     case 'marian-antiphon':
     case 'day-collect':
+    case 'lauds-psalmody':
+    case 'lauds-office':
+    case 'benedictus':
+    case 'suffrages':
+    case 'day-collects':
       throw new Error(`Prime's ordo doesn't support a '${part.kind}' part`);
   }
 }
diff --git a/src/hours/resolve-common.ts b/src/hours/resolve-common.ts
index 1d427d2..b7fbbb9 100644
--- a/src/hours/resolve-common.ts
+++ b/src/hours/resolve-common.ts
@@ -35,6 +35,62 @@ export function getDayCollect(day: LiturgicalDay): ResolvedText {
   return { text: {}, status: { la: 'missing', en: 'missing' } };
 }
 
+/**
+ * The day's own collect, plus one more per commemoration (calendar/
+ * types.ts's LiturgicalDay.commemorations) — Lauds/Vespers say all of
+ * these in sequence, unlike the Little Hours' single getDayCollect.
+ *
+ * Simplification, not yet corrected: real practice compresses this into
+ * one "Orémus" and lets only the *last* collect close with the full
+ * doxology, with earlier ones trailing straight into the next ("And:").
+ * Each collect file (data/propers/temporal/*-collect.yml, the per-saint
+ * *-collect.yml files) already bakes in its own "Orémus."/"Per Dóminum...
+ * Amen." for the single-collect case every other hour uses today, and
+ * stripping that back out per-collect to chain them properly would need
+ * text surgery this doesn't attempt — so on a commemorated day, each
+ * collect here renders as its own complete, separate block instead. An
+ * octave commemoration never contributes a collect (none authored — the
+ * octave content pull only ever sourced Matins readings, see propers/
+ * octave-readings.ts), so those are silently skipped, same as a
+ * not-yet-authored saint's own collect resolves to "missing" rather than
+ * throwing.
+ */
+export function getDayCollects(day: LiturgicalDay): ResolvedText[] {
+  const collects = [getDayCollect(day)];
+  for (const commemoration of day.commemorations) {
+    if (commemoration.kind === 'temporal') {
+      collects.push(toResolvedText(getTemporalProper(`${commemoration.id}-collect`)));
+    } else if (commemoration.kind === 'sanctoral') {
+      const saint = getSaintRecord(commemoration.id);
+      collects.push(
+        saint?.propers
+          ? resolveCommon(`${saint.propers}-collect`)
+          : { text: {}, status: { la: 'missing', en: 'missing' } },
+      );
+    }
+  }
+  return collects;
+}
+
+/**
+ * Lauds' Benedictus antiphon, resolved the same way as getDayCollect: a
+ * per-saint `${propers}-antiphon` (already authored during the sanctoral
+ * pull, sourced from each saint's own raw [Ant 1] — see e.g.
+ * st-lawrence-antiphon.yml) for a sanctoral winner, `${id}-benedictus-
+ * antiphon` (not authored yet for any temporal id — resolves "missing",
+ * same pending convention as everywhere else) for a temporal one.
+ */
+export function getBenedictusAntiphon(day: LiturgicalDay): ResolvedText {
+  if (day.winner.kind === 'temporal') {
+    return toResolvedText(getTemporalProper(`${day.winner.id}-benedictus-antiphon`));
+  }
+  const saint = getSaintRecord(day.winner.id);
+  if (saint?.propers) {
+    return resolveCommon(`${saint.propers}-antiphon`);
+  }
+  return { text: {}, status: { la: 'missing', en: 'missing' } };
+}
+
 export function verifiedText(text: Partial<Record<string, string>>): ResolvedText {
   const status: Partial<Record<string, 'verified'>> = {};
   for (const lang of Object.keys(text)) {
diff --git a/src/hours/sext.ts b/src/hours/sext.ts
index 9d2bdc1..a4b5bb8 100644
--- a/src/hours/sext.ts
+++ b/src/hours/sext.ts
@@ -54,6 +54,11 @@ function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
     case 'closing-antiphon':
     case 'nunc-dimittis':
     case 'marian-antiphon':
+    case 'lauds-psalmody':
+    case 'lauds-office':
+    case 'benedictus':
+    case 'suffrages':
+    case 'day-collects':
       throw new Error(`Sext's ordo doesn't support a '${part.kind}' part`);
   }
 }
diff --git a/src/hours/terce.ts b/src/hours/terce.ts
index 60563a3..361ae31 100644
--- a/src/hours/terce.ts
+++ b/src/hours/terce.ts
@@ -54,6 +54,11 @@ function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
     case 'closing-antiphon':
     case 'nunc-dimittis':
     case 'marian-antiphon':
+    case 'lauds-psalmody':
+    case 'lauds-office':
+    case 'benedictus':
+    case 'suffrages':
+    case 'day-collects':
       throw new Error(`Terce's ordo doesn't support a '${part.kind}' part`);
   }
 }
diff --git a/src/hours/types.ts b/src/hours/types.ts
index 2da2c19..6b71252 100644
--- a/src/hours/types.ts
+++ b/src/hours/types.ts
@@ -82,6 +82,48 @@ export type HourPart =
   // to a 'canticle' ResolvedPart (with the opening antiphon inline) plus a
   // standalone 'antiphon' ResolvedPart for the closing repeat.
   | { kind: 'nunc-dimittis' }
+  // Lauds only. Everything from Ps 66 through the Laudate psalms (148-150)
+  // inclusive, resolved by weekday — see hours/lauds.ts's resolvePsalmody
+  // and data/hours/lauds-antiphons.yml. Opaque here on purpose: the real
+  // shape (a fixed Ps 66 with no antiphon at all, then a weekday-variable
+  // number of antiphoned psalm groups, then a weekday-variable OT canticle,
+  // then the Laudate psalms under one more shared antiphon) doesn't fit any
+  // existing part kind, and hardcoding psalm numbers in lauds.yml can't
+  // work since they differ by weekday. Known, deliberate gap: does NOT
+  // model the Commune/feast override of this whole block (real practice
+  // substitutes an entirely different set of psalms+antiphons+canticle on
+  // a Semiduplex-or-higher day) — every day currently gets the plain
+  // ferial weekday distribution regardless of who wins. Fixing that is a
+  // separate, larger propers-authoring task (a full Common-of-Saints psalm
+  // set per Common), not started yet.
+  | { kind: 'lauds-psalmody' }
+  // Lauds only. The weekday-resolved chapter/short-responsory/hymn/closing
+  // versicle bundle that follows the psalmody — see hours/lauds.ts and
+  // data/propers/common/lauds-{capitulum,responsory,hymn,versicle}-*.yml.
+  // Expands into 4 ResolvedParts (chapter, responsory, hymn, versicle).
+  | { kind: 'lauds-office' }
+  // Lauds only. Benedictus (Luke 1:68-79), fixed text (see propers/common/
+  // benedictus.yml) framed by a day-resolved antiphon (see hours/
+  // resolve-common.ts's getBenedictusAntiphon) — same incipit-or-full/
+  // full-after-Creed... no Creed at Lauds, just before+after framing shape
+  // as nunc-dimittis, gated the same way by isDoubleOrHigher.
+  | { kind: 'benedictus' }
+  // Lauds only. The four fixed Tridentine suffrages (Holy Cross, BVM,
+  // Ss. Peter & Paul, Peace) said after the day's collect(s) — see
+  // data/propers/common/lauds-suffrage-*.yml. `omitOnDouble` gates the
+  // whole set at once (real practice: suffrages drop on a Double-or-higher
+  // feast) — an honest simplification, see hours/lauds.ts for the caveat
+  // on what real practice also suppresses them for that isn't modeled.
+  | { kind: 'suffrages'; omitOnDouble?: true }
+  // Lauds/Vespers. The day's own collect *and* one more per commemoration
+  // (calendar/types.ts's LiturgicalDay.commemorations) — see hours/
+  // resolve-common.ts's getDayCollects. Distinct from the singular
+  // 'day-collect' the Little Hours use (which only ever renders the
+  // winner's own collect, never a commemoration's). Simplification: each
+  // collect renders as its own complete "Let us pray ... Amen." block
+  // rather than the more compressed real form (one "Let us pray," only the
+  // last collect closes with the full doxology) — see hours/lauds.ts.
+  | { kind: 'day-collects' }
   // Compline's closing Marian antiphon (with its own versicle and collect
   // baked into the same text block) — resolved by season, defaulting to
   // Salve Regina. See hours/marian-antiphon.ts.
diff --git a/tests/hours/lauds.test.ts b/tests/hours/lauds.test.ts
new file mode 100644
index 0000000..7ff4a05
--- /dev/null
+++ b/tests/hours/lauds.test.ts
@@ -0,0 +1,203 @@
+import { describe, expect, it } from 'vitest';
+import { resolveOrdo } from '../../src/hours';
+
+// Clean ferial dates, one per weekday — see data/psalter-distribution.yml
+// and src/hours/lauds.ts's own generation-script provenance comments for
+// why these particular dates.
+const FERIAL_SUNDAY = '2026-06-21';
+const FERIAL_MONDAY = '2026-08-31';
+const FERIAL_TUESDAY = '2026-06-16';
+const LAWRENCE_OCTAVE_DAY = '2026-08-11'; // Semiduplex -- exercises isDoubleOrHigher's false branch differently than a plain feria only in rank, not in psalms (Commune override not modeled, see below)
+
+describe('resolveOrdo("lauds", ...)', () => {
+  it('is implemented', () => {
+    expect(resolveOrdo('lauds', FERIAL_TUESDAY).notImplemented).toBeUndefined();
+  });
+
+  it('opens with Ps 66 and gives it no antiphon at all, unlike every other psalm here', () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const psalms = ordo.parts.filter((p) => p.kind === 'psalm');
+    expect(psalms[0]?.kind === 'psalm' ? psalms[0].psalmNumber : undefined).toBe(66);
+    expect(psalms[0]?.kind === 'psalm' ? psalms[0].antiphon : 'should be undefined').toBeUndefined();
+  });
+
+  it("resolves Tuesday's weekday psalmody: Ps 50, 42, 56, the Canticle of Ezechias, then 148-150", () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const psalmNumbers = ordo.parts
+      .filter((p) => p.kind === 'psalm')
+      .map((p) => (p.kind === 'psalm' ? p.psalmNumber : undefined));
+    expect(psalmNumbers).toEqual([66, 50, 42, 56, 148, 149, 150]);
+
+    const canticle = ordo.parts.find((p) => p.kind === 'canticle' && p.canticleId !== 'benedictus');
+    expect(canticle?.kind === 'canticle' ? canticle.canticleId : undefined).toBe('canticum-ezechiae');
+    expect(canticle?.kind === 'canticle' ? canticle.text.text.la : undefined).toContain('In dimídio diérum meórum');
+  });
+
+  it("gives each variable psalm group its own opening antiphon (incipit, below Double) and a full repeat right after", () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const ps50Index = ordo.parts.findIndex((p) => p.kind === 'psalm' && p.psalmNumber === 50);
+    const ps50 = ordo.parts[ps50Index];
+    expect(ps50?.kind === 'psalm' ? ps50.antiphon?.text.la : undefined).toBe('Ant. Dele, Dómine.');
+    const repeat = ordo.parts[ps50Index + 1];
+    expect(repeat?.kind).toBe('antiphon');
+    expect(repeat?.kind === 'antiphon' ? repeat.text.text.la : undefined).toBe('Ant. Dele, Dómine, * iniquitátem meam.');
+  });
+
+  it("resolves Sunday's own psalmody: Ps 50+117 sharing one antiphon, then 62, then the Canticle of the Three Young Men", () => {
+    const ordo = resolveOrdo('lauds', FERIAL_SUNDAY);
+    const psalmNumbers = ordo.parts
+      .filter((p) => p.kind === 'psalm')
+      .map((p) => (p.kind === 'psalm' ? p.psalmNumber : undefined));
+    expect(psalmNumbers).toEqual([66, 50, 117, 62, 148, 149, 150]);
+
+    const ps117 = ordo.parts.find((p) => p.kind === 'psalm' && p.psalmNumber === 117);
+    expect(ps117?.kind === 'psalm' ? ps117.antiphon : 'should be undefined -- shares Ps 50s opening antiphon').toBeUndefined();
+
+    const canticle = ordo.parts.find((p) => p.kind === 'canticle' && p.canticleId !== 'benedictus');
+    expect(canticle?.kind === 'canticle' ? canticle.canticleId : undefined).toBe('canticum-trium-puerorum');
+  });
+
+  it("resolves Saturday's own psalmody: only one weekday psalm (142), and the Canticle of Moses split across two D.O. slots joins into one continuous canticle", () => {
+    // Any Saturday works here: lauds-psalmody doesn't yet model the
+    // Commune/feast override real practice would apply on a Marian-
+    // Sabbato Saturday (see hours/types.ts's 'lauds-psalmody' doc comment)
+    // -- the plain weekday distribution is always used, so this is
+    // exercising the real, current behavior, not a stand-in for it.
+    const ordo = resolveOrdo('lauds', '2026-06-20');
+    const psalmNumbers = ordo.parts
+      .filter((p) => p.kind === 'psalm')
+      .map((p) => (p.kind === 'psalm' ? p.psalmNumber : undefined));
+    expect(psalmNumbers).toEqual([66, 50, 142, 148, 149, 150]);
+
+    const canticle = ordo.parts.find((p) => p.kind === 'canticle' && p.canticleId !== 'benedictus');
+    expect(canticle?.kind === 'canticle' ? canticle.canticleId : undefined).toBe('canticum-moysis-deuteronomii');
+    expect(canticle?.kind === 'canticle' ? canticle.text.text.la : undefined).toContain('Audíte, cæli');
+  });
+
+  it('gives the Laudate psalms (148-150) one shared antiphon, opening before 148 and repeated in full after 150', () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const ps148Index = ordo.parts.findIndex((p) => p.kind === 'psalm' && p.psalmNumber === 148);
+    const ps149 = ordo.parts[ps148Index + 1];
+    const ps150 = ordo.parts[ps148Index + 2];
+    expect(ps149?.kind === 'psalm' ? ps149.antiphon : 'should be undefined').toBeUndefined();
+    expect(ps150?.kind === 'psalm' ? ps150.antiphon : 'should be undefined').toBeUndefined();
+    const repeat = ordo.parts[ps148Index + 3];
+    expect(repeat?.kind).toBe('antiphon');
+    expect(repeat?.kind === 'antiphon' ? repeat.text.text.en : undefined).toContain(
+      'Praise ye the Lord * from the heavens, all His angels',
+    );
+  });
+
+  it("resolves the weekday chapter/responsory/hymn/versicle bundle, sharing the same capitulum Mon-Fri", () => {
+    const tue = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const mon = resolveOrdo('lauds', FERIAL_MONDAY);
+    const tueChapter = tue.parts.find((p) => p.kind === 'chapter');
+    const monChapter = mon.parts.find((p) => p.kind === 'chapter');
+    expect(tueChapter?.kind === 'chapter' ? tueChapter.text.citation?.en : undefined).toBe('Rom 13:12-13');
+    expect(tueChapter?.kind === 'chapter' ? tueChapter.text.text.la : undefined).toBe(
+      monChapter?.kind === 'chapter' ? monChapter.text.text.la : undefined,
+    );
+
+    const responsory = tue.parts.find((p) => p.kind === 'responsory');
+    expect(responsory?.kind === 'responsory' ? responsory.text.text.la : undefined).toContain('Sana ánimam meam');
+
+    const hymn = tue.parts.find((p) => p.kind === 'hymn');
+    expect(hymn?.kind === 'hymn' ? hymn.text.text.la : undefined).toContain('Ales diéi núntius');
+  });
+
+  it("marks Saturday's hymn honestly missing rather than presenting a privileged season's swapped hymn as the default", () => {
+    const ordo = resolveOrdo('lauds', '2026-06-20');
+    const hymn = ordo.parts.find((p) => p.kind === 'hymn');
+    expect(hymn?.kind === 'hymn' ? hymn.text.status.la : undefined).toBe('missing');
+  });
+
+  it('resolves the Benedictus as a canticle with an opening antiphon and a full repeat, same shape as Compline\'s Nunc Dimittis', () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const canticleIndex = ordo.parts.findIndex((p) => p.kind === 'canticle' && p.canticleId === 'benedictus');
+    const canticle = ordo.parts[canticleIndex];
+    expect(canticle?.kind === 'canticle' ? canticle.text.text.en : undefined).toContain('Blessed be the Lord');
+    const repeat = ordo.parts[canticleIndex + 1];
+    expect(repeat?.kind).toBe('antiphon');
+  });
+
+  it("falls back to a missing Benedictus antiphon on a plain temporal day (no per-Sunday antiphon authored yet)", () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const canticle = ordo.parts.find((p) => p.kind === 'canticle' && p.canticleId === 'benedictus');
+    expect(canticle?.kind === 'canticle' ? canticle.antiphon?.status?.la : undefined).toBeUndefined();
+  });
+
+  it("resolves a real Benedictus antiphon on St. Lawrence's own octave day, from the saint's already-authored proper", () => {
+    const ordo = resolveOrdo('lauds', '2026-08-10'); // St. Lawrence's own day
+    const canticle = ordo.parts.find((p) => p.kind === 'canticle' && p.canticleId === 'benedictus');
+    expect(canticle?.kind === 'canticle' ? canticle.antiphon?.text.la : undefined).toContain('Levíta Lauréntius');
+  });
+
+  it('includes the short litany (Kyrie + Our Father) right after the Benedictus, before the day collect', () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const litanyIndex = ordo.parts.findIndex((p) => p.kind === 'preces' && p.text.text.la?.includes('Kýrie, eléison'));
+    const benedictusIndex = ordo.parts.findIndex((p) => p.kind === 'canticle' && p.canticleId === 'benedictus');
+    const collectIndex = ordo.parts.findIndex((p) => p.kind === 'prayer');
+    expect(litanyIndex).toBeGreaterThan(benedictusIndex);
+    expect(collectIndex).toBeGreaterThan(litanyIndex);
+  });
+
+  it('resolves just the winners own collect on a plain day with nothing commemorated', () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const collects = ordo.parts.filter((p) => p.kind === 'prayer');
+    expect(collects.length).toBe(1);
+  });
+
+  it('resolves both the winners collect and a commemorated saints collect on a day with a real commemoration', () => {
+    // 2025-11-30: Advent I (the winner) with St. Andrew, Duplex II. classis,
+    // commemorated alongside it (see tests/calendar/day-label.test.ts) --
+    // an octave commemoration (like LAWRENCE_OCTAVE_DAY's) never
+    // contributes a collect (none authored yet), so this needs a real
+    // sanctoral/temporal commemoration instead to exercise getDayCollects
+    // pushing a second entry.
+    const ordo = resolveOrdo('lauds', '2025-11-30');
+    const collects = ordo.parts.filter((p) => p.kind === 'prayer');
+    expect(collects.length).toBe(2);
+    expect(collects[1]?.kind === 'prayer' ? collects[1].text.text.en : undefined).toContain('Andrew');
+  });
+
+  it("skips a straight octave commemoration for collect purposes (no octave collect authored)", () => {
+    const ordo = resolveOrdo('lauds', LAWRENCE_OCTAVE_DAY);
+    const collects = ordo.parts.filter((p) => p.kind === 'prayer');
+    expect(collects.length).toBe(1);
+  });
+
+  it('includes all four Tridentine suffrages, in order, on an ordinary day', () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const labels = ordo.parts.filter((p) => p.kind === 'preces' && p.label).map((p) => (p.kind === 'preces' ? p.label : undefined));
+    expect(labels).toEqual([
+      'Of the Holy Cross',
+      'Of the Blessed Virgin Mary',
+      'Of the Holy Apostles Peter and Paul',
+      'For Peace',
+      'Salve Regina',
+    ]);
+  });
+
+  it('omits the suffrages on a Double-or-higher feast', () => {
+    const ordo = resolveOrdo('lauds', '2026-08-10'); // St. Lawrence, Duplex II. classis
+    const crossSuffrage = ordo.parts.find((p) => p.kind === 'preces' && p.label === 'Of the Holy Cross');
+    expect(crossSuffrage).toBeUndefined();
+  });
+
+  it('closes with the Conclusio, the closing versicle ("may the Lord grant us his peace... and life everlasting"), and the Marian antiphon -- without spelling out the silent Our Father', () => {
+    const ordo = resolveOrdo('lauds', FERIAL_TUESDAY);
+    const closingVersicle = ordo.parts.find(
+      (p) => p.kind === 'versicle' && p.text.text.en?.includes('grant us his peace'),
+    );
+    expect(closingVersicle?.kind === 'versicle' ? closingVersicle.text.text.en : undefined).toContain(
+      'life everlasting',
+    );
+    expect(closingVersicle?.kind === 'versicle' ? closingVersicle.text.text.en : undefined).not.toContain(
+      'Our Father',
+    );
+
+    const last = ordo.parts[ordo.parts.length - 1];
+    expect(last?.kind).toBe('preces');
+    expect(last?.kind === 'preces' ? last.label : undefined).toBe('Salve Regina');
+  });
+});
diff --git a/tests/hours/prime.test.ts b/tests/hours/prime.test.ts
index 2e82ab8..338141d 100644
--- a/tests/hours/prime.test.ts
+++ b/tests/hours/prime.test.ts
@@ -194,8 +194,8 @@ describe('resolveOrdo("prime", ...)', () => {
 });
 
 describe('resolveOrdo for not-yet-built hours', () => {
-  it('flags lauds as not implemented rather than throwing', () => {
-    const ordo = resolveOrdo('lauds', MONDAY);
+  it('flags vespers as not implemented rather than throwing', () => {
+    const ordo = resolveOrdo('vespers', MONDAY);
     expect(ordo.notImplemented).toBe(true);
     expect(ordo.parts).toEqual([]);
   });
diff --git a/tests/ui/shell.test.ts b/tests/ui/shell.test.ts
index fa3ccbf..1c93e58 100644
--- a/tests/ui/shell.test.ts
+++ b/tests/ui/shell.test.ts
@@ -41,12 +41,12 @@ describe('shell', () => {
     const root = document.getElementById('app')!;
     mountShell(root);
 
-    const laudsBtn = Array.from(root.querySelectorAll<HTMLButtonElement>('[data-hour]')).find(
-      (btn) => btn.dataset.hour === 'lauds',
+    const vespersBtn = Array.from(root.querySelectorAll<HTMLButtonElement>('[data-hour]')).find(
+      (btn) => btn.dataset.hour === 'vespers',
     );
-    laudsBtn?.click();
+    vespersBtn?.click();
 
-    expect(root.querySelector('.hour-view h2')?.textContent).toBe('Lauds');
+    expect(root.querySelector('.hour-view h2')?.textContent).toBe('Vespers');
     expect(root.querySelector('.hour-view-pending')).not.toBeNull();
   });