diff --git a/src/hours/lauds.ts b/src/hours/lauds.ts
index 7e2ac0b..4401cba 100644
--- a/src/hours/lauds.ts
+++ b/src/hours/lauds.ts
@@ -8,7 +8,7 @@ import { getCanticle } from './lauds-canticles';
 import { getLaudsPsalmodyOverride, type LaudsPsalmodyOverride } from './lauds-psalmody-overrides';
 import { getOpeningVersicleId } from './opening-versicle';
 import { getMarianAntiphonId, getMarianAntiphonLabel } from './marian-antiphon';
-import { isDoubleOrHigher } from './antiphon';
+import { isDoubleOrHigher, applyFlexaMark } from './antiphon';
 import {
   resolveCommon,
   getDayCollects,
@@ -81,12 +81,16 @@ function capitulumId(weekday: Weekday): string {
 }
 
 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 })),
-  }));
+  const parts: ResolvedPart[] = numbers.map((number, i) => {
+    const rawVerses = getPsalmVerses(number).map((v) => ({ n: v.n, text: v.text, status: v.status }));
+    const { verses, antiphon: psalmAntiphon } = applyFlexaMark(rawVerses, i === 0 ? opening : undefined);
+    return {
+      kind: 'psalm' as const,
+      psalmNumber: number,
+      antiphon: psalmAntiphon,
+      verses,
+    };
+  });
   parts.push({ kind: 'antiphon', text: splitNamedAntiphon(verifiedText(antiphon)).full });
   return parts;
 }
diff --git a/src/hours/matins.ts b/src/hours/matins.ts
index fdebcbe..02f5000 100644
--- a/src/hours/matins.ts
+++ b/src/hours/matins.ts
@@ -69,7 +69,7 @@ import { getPsalmVerses } from '../psalter';
 import { getPsalmsFor, type PsalmRef } from '../psalter/distribution';
 import { getScriptureVerses } from '../scripture';
 import { getOpeningVersicleId } from './opening-versicle';
-import { isDoubleOrHigher } from './antiphon';
+import { isDoubleOrHigher, applyFlexaMark } from './antiphon';
 import {
   resolveCommon,
   getDayCollect,
@@ -150,6 +150,15 @@ function plainPsalm(number: number): PsalmPart {
   };
 }
 
+/** `plainPsalm` plus the given antiphon, with the flexa mark (see
+ * hours/antiphon.ts's `applyFlexaMark`) applied to the first verse against
+ * that antiphon — a no-op when `antiphon` is undefined. */
+function psalmPartWithAntiphon(number: number, rawAntiphon: ResolvedText | undefined): PsalmPart {
+  const base = plainPsalm(number);
+  const { verses, antiphon } = applyFlexaMark(base.verses, rawAntiphon);
+  return { ...base, antiphon, verses };
+}
+
 function psalmRefParts(refs: PsalmRef[]): ResolvedPart[] {
   return refs.map((ref) => ({
     kind: 'psalm' as const,
@@ -167,7 +176,7 @@ function invitatoryParts(day: LiturgicalDay): ResolvedPart[] {
   const { incipit, full } = splitNamedAntiphon(resolveCommon('matins-invitatory-antiphon'));
   const opening = isDoubleOrHigher(resolveOfficeWinner(day)) ? full : incipit;
   return [
-    { ...plainPsalm(94), antiphon: opening },
+    psalmPartWithAntiphon(94, opening),
     { kind: 'antiphon', text: full },
   ];
 }
@@ -181,7 +190,7 @@ function sundayPsalmNocturn(group: SundayNocturn, day: LiturgicalDay): ResolvedP
     const { incipit, full } = splitNamedAntiphon(verifiedText(g.antiphon));
     const opening = isDoubleOrHigher(resolveOfficeWinner(day)) ? full : incipit;
     g.psalms.forEach((n, i) => {
-      parts.push({ ...plainPsalm(n), antiphon: i === 0 ? opening : undefined });
+      parts.push(psalmPartWithAntiphon(n, i === 0 ? opening : undefined));
     });
     parts.push({ kind: 'antiphon', text: full });
   }
@@ -282,11 +291,13 @@ function ferialAntiphonedNocturn(day: LiturgicalDay): ResolvedPart[] {
     const { incipit, full } = splitNamedAntiphon(verifiedText(group.antiphon));
     const opening = isDouble ? full : incipit;
     group.psalms.forEach((ref, i) => {
+      const rawVerses = getPsalmVerses(ref.number, ref.verses).map((v): ResolvedVerse => ({ n: v.n, text: v.text, status: v.status }));
+      const { verses, antiphon } = applyFlexaMark(rawVerses, i === 0 ? opening : undefined);
       parts.push({
         kind: 'psalm',
         psalmNumber: ref.number,
-        verses: getPsalmVerses(ref.number, ref.verses).map((v): ResolvedVerse => ({ n: v.n, text: v.text, status: v.status })),
-        antiphon: i === 0 ? opening : undefined,
+        verses,
+        antiphon,
       });
     });
     parts.push({ kind: 'antiphon', text: full });
diff --git a/src/hours/none.ts b/src/hours/none.ts
index 3aa1022..c6a32aa 100644
--- a/src/hours/none.ts
+++ b/src/hours/none.ts
@@ -5,7 +5,7 @@ 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 { isDoubleOrHigher, applyFlexaMark } from './antiphon';
 import {
   resolveCommon,
   getDayCollect,
@@ -40,12 +40,16 @@ function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
       const psalmRefs = getPsalmsFor('none', day.weekday);
       const { incipit, full } = splitNamedAntiphon(resolveMinorHourAntiphon('none', day, antiphons[day.weekday]));
       const opening = isDoubleOrHigher(resolveOfficeWinner(day)) ? 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 })),
-      }));
+      return psalmRefs.map((ref, i) => {
+        const rawVerses = getPsalmVerses(ref.number, ref.verses).map((v) => ({ n: v.n, text: v.text, status: v.status }));
+        const { verses, antiphon } = applyFlexaMark(rawVerses, i === 0 ? opening : undefined);
+        return {
+          kind: 'psalm' as const,
+          psalmNumber: ref.number,
+          antiphon,
+          verses,
+        };
+      });
     }
     // Not used by None.
     case 'prayer':
diff --git a/src/hours/prime.ts b/src/hours/prime.ts
index 7ce44e1..a7cc4ca 100644
--- a/src/hours/prime.ts
+++ b/src/hours/prime.ts
@@ -9,7 +9,7 @@ import { getRegulaReadingFor } from '../regula';
 import { getChapterResponsoryId } from './chapter-responsory';
 import { getHymnDoxologyId } from './hymn-doxology';
 import { getOpeningVersicleId } from './opening-versicle';
-import { isDoubleOrHigher } from './antiphon';
+import { isDoubleOrHigher, applyFlexaMark } from './antiphon';
 import {
   resolveCommon,
   appendDoxology,
@@ -70,12 +70,16 @@ function resolvePart(part: HourPart, date: string, day: LiturgicalDay): Resolved
         // — see hours/antiphon.ts. The full repeat comes later, after the
         // Creed (see 'closing-antiphon'), not tacked onto the last psalm.
         const opening = isDoubleOrHigher(resolveOfficeWinner(day)) ? 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 })),
-        }));
+        return psalmRefs.map((ref, i) => {
+          const rawVerses = getPsalmVerses(ref.number, ref.verses).map((v) => ({ n: v.n, text: v.text, status: v.status }));
+          const { verses, antiphon } = applyFlexaMark(rawVerses, i === 0 ? opening : undefined);
+          return {
+            kind: 'psalm' as const,
+            psalmNumber: ref.number,
+            antiphon,
+            verses,
+          };
+        });
       }
     case 'psalm':
       return [
diff --git a/src/hours/sext.ts b/src/hours/sext.ts
index 6fdedb7..b012954 100644
--- a/src/hours/sext.ts
+++ b/src/hours/sext.ts
@@ -5,7 +5,7 @@ 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 { isDoubleOrHigher, applyFlexaMark } from './antiphon';
 import {
   resolveCommon,
   getDayCollect,
@@ -40,12 +40,16 @@ function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
       const psalmRefs = getPsalmsFor('sext', day.weekday);
       const { incipit, full } = splitNamedAntiphon(resolveMinorHourAntiphon('sext', day, antiphons[day.weekday]));
       const opening = isDoubleOrHigher(resolveOfficeWinner(day)) ? 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 })),
-      }));
+      return psalmRefs.map((ref, i) => {
+        const rawVerses = getPsalmVerses(ref.number, ref.verses).map((v) => ({ n: v.n, text: v.text, status: v.status }));
+        const { verses, antiphon } = applyFlexaMark(rawVerses, i === 0 ? opening : undefined);
+        return {
+          kind: 'psalm' as const,
+          psalmNumber: ref.number,
+          antiphon,
+          verses,
+        };
+      });
     }
     // Not used by Sext.
     case 'prayer':
diff --git a/src/hours/terce.ts b/src/hours/terce.ts
index 48b2e21..97eb054 100644
--- a/src/hours/terce.ts
+++ b/src/hours/terce.ts
@@ -5,7 +5,7 @@ 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 { isDoubleOrHigher, applyFlexaMark } from './antiphon';
 import {
   resolveCommon,
   getDayCollect,
@@ -40,12 +40,16 @@ function resolvePart(part: HourPart, day: LiturgicalDay): ResolvedPart[] {
       const psalmRefs = getPsalmsFor('terce', day.weekday);
       const { incipit, full } = splitNamedAntiphon(resolveMinorHourAntiphon('terce', day, antiphons[day.weekday]));
       const opening = isDoubleOrHigher(resolveOfficeWinner(day)) ? 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 })),
-      }));
+      return psalmRefs.map((ref, i) => {
+        const rawVerses = getPsalmVerses(ref.number, ref.verses).map((v) => ({ n: v.n, text: v.text, status: v.status }));
+        const { verses, antiphon } = applyFlexaMark(rawVerses, i === 0 ? opening : undefined);
+        return {
+          kind: 'psalm' as const,
+          psalmNumber: ref.number,
+          antiphon,
+          verses,
+        };
+      });
     }
     // Not used by Terce.
     case 'prayer':
diff --git a/src/hours/vespers.ts b/src/hours/vespers.ts
index 3091033..6c1da84 100644
--- a/src/hours/vespers.ts
+++ b/src/hours/vespers.ts
@@ -4,7 +4,7 @@ import { resolveEveningDay } from '../calendar/vespers';
 import { getDayLabel } from '../calendar/day-label';
 import { getPsalmVerses } from '../psalter';
 import { getOpeningVersicleId } from './opening-versicle';
-import { isDoubleOrHigher } from './antiphon';
+import { isDoubleOrHigher, applyFlexaMark } from './antiphon';
 import {
   resolveCommon,
   getDayCollects,
@@ -50,12 +50,16 @@ function psalmParts(group: VespersGroup, day: LiturgicalDay): ResolvedPart[] {
   const { incipit, full } = splitNamedAntiphon(verifiedText(group.antiphon));
   const opening = isDoubleOrHigher(resolveOfficeWinner(day)) ? full : incipit;
   const refs = group.psalms.map(normalizePsalmRef);
-  const parts: ResolvedPart[] = refs.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 })),
-  }));
+  const parts: ResolvedPart[] = refs.map((ref, i) => {
+    const rawVerses = getPsalmVerses(ref.number, ref.verses).map((v) => ({ n: v.n, text: v.text, status: v.status }));
+    const { verses, antiphon } = applyFlexaMark(rawVerses, i === 0 ? opening : undefined);
+    return {
+      kind: 'psalm' as const,
+      psalmNumber: ref.number,
+      antiphon,
+      verses,
+    };
+  });
   parts.push({ kind: 'antiphon', text: full });
   return parts;
 }
diff --git a/tests/hours/flexa.test.ts b/tests/hours/flexa.test.ts
new file mode 100644
index 0000000..91fce37
--- /dev/null
+++ b/tests/hours/flexa.test.ts
@@ -0,0 +1,16 @@
+import { describe, expect, it } from 'vitest';
+import { resolveOrdo } from '../../src/hours';
+
+describe('resolveOrdo("matins", ...) flexa mark on Ps 20', () => {
+  it("marks where today's opening antiphon leaves off, in both the antiphon itself and Ps 20's first verse (Sunday Matins, Nocturn 1, 2026-08-23)", () => {
+    const ordo = resolveOrdo('matins', '2026-08-23');
+    const ps20 = ordo.parts.find((p) => p.kind === 'psalm' && p.psalmNumber === 20);
+    expect(ps20).toBeDefined();
+    if (ps20?.kind !== 'psalm') throw new Error('expected a psalm part');
+    const firstVerse = ps20.verses[0];
+    expect(firstVerse?.text.la).toContain('‡');
+    expect(firstVerse?.text.en).toContain('‡');
+    expect(ps20.antiphon?.text.la).toContain('‡');
+    expect(ps20.antiphon?.text.en).toContain('‡');
+  });
+});