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+// Traditional liturgical incipits ("Léctio libri Sapiéntiæ" / "A reading
+// from the book of Wisdom") for every book abbreviation used under
+// src/data/scripture — keyed exactly as ScriptureCitation.book spells them
+// (bible-plan.ts, octave-readings.ts). Used to replace the generic
+// "Reading"/"Gospel" UI heading (see hour-view.ts's renderLessonLabel) with
+// a real attribution wherever no editorial `source`/`label` was authored —
+// the common case for the user's own continuous bible-plan readings.
+//
+// Latin wording is drawn directly from the reference engine's own Sancti/
+// Commune/Tempora files (grep for "Léctio" across
+// ../divinum-officium-reference) wherever a match was found there; the
+// handful of books that never get their own proper-of-saints lesson in the
+// reference engine (Baruch, Aggeus, Habacuc, Nahum, Abdias, Sophonias, Josue,
+// Judges, Ruth, Proverbs, Ecclesiastes, Canticle of Canticles,
+// Ecclesiasticus, Lamentations, and the ordinal Kings/Paralipomenon/Esdras/
+// Machabees forms) follow the same standard Vulgate genitive pattern as the
+// confirmed ones, not independently re-verified per book.
+//
+// English keeps the reference engine's own "A reading from..." phrasing
+// (2026-09-03, user) but says "Saint Paul"/"Saint James"/etc., not "blessed
+// Paul" — the reference engine's English text mixes both, and "Saint" is
+// the ordinary modern English way to name an apostle, even though the
+// Latin `beáti` this pairs with is left as-is (that's correct Latin usage,
+// not the thing being fixed).
+export const BOOK_INCIPITS: Record<string, { la: string; en: string }> = {
+  // Pentateuch
+  gen: { la: 'Léctio libri Génesis', en: 'A reading from the book of Genesis' },
+  exod: { la: 'Léctio libri Éxodi', en: 'A reading from the book of Exodus' },
+  lev: { la: 'Léctio libri Levítici', en: 'A reading from the book of Leviticus' },
+  num: { la: 'Léctio libri Numeri', en: 'A reading from the book of Numbers' },
+  deut: { la: 'Léctio libri Deuteronómii', en: 'A reading from the book of Deuteronomy' },
+  // Historical books
+  jos: { la: 'Léctio libri Josue', en: 'A reading from the book of Josue' },
+  jdc: { la: 'Léctio libri Judicum', en: 'A reading from the book of Judges' },
+  ruth: { la: 'Léctio libri Ruth', en: 'A reading from the book of Ruth' },
+  '1reg': { la: 'Léctio libri primi Regum', en: 'A reading from the first book of Kings' },
+  '2reg': { la: 'Léctio libri secúndi Regum', en: 'A reading from the second book of Kings' },
+  '3reg': { la: 'Léctio libri tértii Regum', en: 'A reading from the third book of Kings' },
+  '4reg': { la: 'Léctio libri quárti Regum', en: 'A reading from the fourth book of Kings' },
+  '1par': { la: 'Léctio libri primi Paralipómenon', en: 'A reading from the first book of Paralipomenon' },
+  '2par': { la: 'Léctio libri secúndi Paralipómenon', en: 'A reading from the second book of Paralipomenon' },
+  '1esdr': { la: 'Léctio libri primi Esdræ', en: 'A reading from the first book of Esdras' },
+  '2esdr': { la: 'Léctio libri secúndi Esdræ', en: 'A reading from the second book of Esdras' },
+  tob: { la: 'Léctio libri Tobíæ', en: 'A reading from the book of Tobias' },
+  jdth: { la: 'Léctio libri Judith', en: 'A reading from the book of Judith' },
+  esth: { la: 'Léctio libri Esther', en: 'A reading from the book of Esther' },
+  job: { la: 'Léctio libri Job', en: 'A reading from the book of Job' },
+  '1mach': { la: 'Léctio libri primi Machabæórum', en: 'A reading from the first book of Machabees' },
+  '2mach': { la: 'Léctio libri secúndi Machabæórum', en: 'A reading from the second book of Machabees' },
+  // Wisdom books
+  prov: { la: 'Léctio libri Próverbiórum', en: 'A reading from the book of Proverbs' },
+  eccl: { la: 'Léctio libri Ecclesiástæ', en: 'A reading from the book of Ecclesiastes' },
+  cant: { la: 'Léctio libri Cánticorum Canticórum', en: 'A reading from the Canticle of Canticles' },
+  sap: { la: 'Léctio libri Sapiéntiæ', en: 'A reading from the book of Wisdom' },
+  sir: { la: 'Léctio libri Ecclesiástici', en: 'A reading from the book of Ecclesiasticus' },
+  // Major prophets
+  isa: { la: 'Léctio Isaíæ Prophétæ', en: 'A reading from the Prophecy of Isaias' },
+  jer: { la: 'Léctio Jeremíæ Prophétæ', en: 'A reading from the Prophecy of Jeremias' },
+  lam: { la: 'Léctio Threnórum Jeremíæ Prophétæ', en: 'A reading from the Lamentations of Jeremias the Prophet' },
+  bar: { la: 'Léctio Baruch Prophétæ', en: 'A reading from the Prophecy of Baruch' },
+  ezek: { la: 'Léctio Ezechiélis Prophétæ', en: 'A reading from the Prophecy of Ezechiel' },
+  dan: { la: 'Léctio Daniélis Prophétæ', en: 'A reading from the Prophecy of Daniel' },
+  // Minor prophets
+  osee: { la: 'Léctio Osee Prophétæ', en: 'A reading from the Prophecy of Osee' },
+  joel: { la: 'Léctio Joélis Prophétæ', en: 'A reading from the Prophecy of Joel' },
+  amos: { la: 'Léctio Amos Prophétæ', en: 'A reading from the Prophecy of Amos' },
+  abd: { la: 'Léctio Abdíæ Prophétæ', en: 'A reading from the Prophecy of Abdias' },
+  jon: { la: 'Léctio Jonæ Prophétæ', en: 'A reading from the Prophecy of Jonas' },
+  mich: { la: 'Léctio Michǽæ Prophétæ', en: 'A reading from the Prophecy of Micheas' },
+  nah: { la: 'Léctio Nahum Prophétæ', en: 'A reading from the Prophecy of Nahum' },
+  hab: { la: 'Léctio Habacuc Prophétæ', en: 'A reading from the Prophecy of Habacuc' },
+  soph: { la: 'Léctio Sophoníæ Prophétæ', en: 'A reading from the Prophecy of Sophonias' },
+  agg: { la: 'Léctio Aggǽi Prophétæ', en: 'A reading from the Prophecy of Aggeus' },
+  zach: { la: 'Léctio Zacharíæ Prophétæ', en: 'A reading from the Prophecy of Zacharias' },
+  mal: { la: 'Léctio Malachíæ Prophétæ', en: 'A reading from the Prophecy of Malachias' },
+  // Gospels
+  matt: { la: 'Léctio sancti Evangélii secúndum Matthǽum', en: 'A reading from the Holy Gospel according to Matthew' },
+  marc: { la: 'Léctio sancti Evangélii secúndum Marcum', en: 'A reading from the Holy Gospel according to Mark' },
+  luc: { la: 'Léctio sancti Evangélii secúndum Lucam', en: 'A reading from the Holy Gospel according to Luke' },
+  joan: { la: 'Léctio sancti Evangélii secúndum Joánnem', en: 'A reading from the Holy Gospel according to John' },
+  // Acts
+  act: { la: 'Léctio Actuum Apostolórum', en: 'A reading from the Acts of the Apostles' },
+  // Pauline epistles
+  rom: { la: 'Léctio Epístolæ beáti Pauli Apóstoli ad Romános', en: 'A reading from the Epistle of Saint Paul the Apostle to the Romans' },
+  '1cor': { la: 'Léctio Epístolæ primæ beáti Pauli Apóstoli ad Corínthios', en: 'A reading from the first Epistle of Saint Paul the Apostle to the Corinthians' },
+  '2cor': { la: 'Léctio Epístolæ secúndæ beáti Pauli Apóstoli ad Corínthios', en: 'A reading from the second Epistle of Saint Paul the Apostle to the Corinthians' },
+  gal: { la: 'Léctio Epístolæ beáti Pauli Apóstoli ad Gálatas', en: 'A reading from the Epistle of Saint Paul the Apostle to the Galatians' },
+  eph: { la: 'Léctio Epístolæ beáti Pauli Apóstoli ad Ephésios', en: 'A reading from the Epistle of Saint Paul the Apostle to the Ephesians' },
+  phil: { la: 'Léctio Epístolæ beáti Pauli Apóstoli ad Philippénses', en: 'A reading from the Epistle of Saint Paul the Apostle to the Philippians' },
+  col: { la: 'Léctio Epístolæ beáti Pauli Apóstoli ad Colossénses', en: 'A reading from the Epistle of Saint Paul the Apostle to the Colossians' },
+  '1thess': { la: 'Léctio Epístolæ primæ beáti Pauli Apóstoli ad Thessalonicénses', en: 'A reading from the first Epistle of Saint Paul the Apostle to the Thessalonians' },
+  '2thess': { la: 'Léctio Epístolæ secúndæ beáti Pauli Apóstoli ad Thessalonicénses', en: 'A reading from the second Epistle of Saint Paul the Apostle to the Thessalonians' },
+  '1tim': { la: 'Léctio Epístolæ primæ beáti Pauli Apóstoli ad Timótheum', en: 'A reading from the first Epistle of Saint Paul the Apostle to Timothy' },
+  '2tim': { la: 'Léctio Epístolæ secúndæ beáti Pauli Apóstoli ad Timótheum', en: 'A reading from the second Epistle of Saint Paul the Apostle to Timothy' },
+  tit: { la: 'Léctio Epístolæ beáti Pauli Apóstoli ad Titum', en: 'A reading from the Epistle of Saint Paul the Apostle to Titus' },
+  phlm: { la: 'Léctio Epístolæ beáti Pauli Apóstoli ad Philémonem', en: 'A reading from the Epistle of Saint Paul the Apostle to Philemon' },
+  heb: { la: 'Léctio Epístolæ beáti Pauli Apóstoli ad Hebrǽos', en: 'A reading from the Epistle of Saint Paul the Apostle to the Hebrews' },
+  // Catholic epistles
+  jac: { la: 'Léctio Epístolæ beáti Jacóbi Apóstoli', en: 'A reading from the Epistle of Saint James the Apostle' },
+  '1pet': { la: 'Léctio Epístolæ primæ beáti Petri Apóstoli', en: 'A reading from the first Epistle of Saint Peter the Apostle' },
+  '2pet': { la: 'Léctio Epístolæ secúndæ beáti Petri Apóstoli', en: 'A reading from the second Epistle of Saint Peter the Apostle' },
+  '1joan': { la: 'Léctio Epístolæ primæ beáti Joánnis Apóstoli', en: 'A reading from the first Epistle of Saint John the Apostle' },
+  '2joan': { la: 'Léctio Epístolæ secúndæ beáti Joánnis Apóstoli', en: 'A reading from the second Epistle of Saint John the Apostle' },
+  '3joan': { la: 'Léctio Epístolæ tértiæ beáti Joánnis Apóstoli', en: 'A reading from the third Epistle of Saint John the Apostle' },
+  jud: { la: 'Léctio Epístolæ beáti Judæ Apóstoli', en: 'A reading from the Epistle of Saint Jude the Apostle' },
+  // Apocalypse
+  apoc: { la: 'Léctio libri Apocalýpsis beáti Joánnis Apóstoli', en: 'A reading from the book of the Apocalypse of Saint John the Apostle' },
+};
+
+/** Book abbreviation -> {la, en} incipit, or undefined for an unrecognized
+ * abbreviation (shouldn't happen for anything actually keyed under
+ * src/data/scripture, but callers still get an honest absence rather than
+ * a made-up label). */
+export function getBookIncipit(book: string): { la: string; en: string } | undefined {
+  return BOOK_INCIPITS[book];
+}
+
+// Nocturn-readings.ts's own hand-authored Gospel pericopes (unlike
+// bible-plan.ts's) carry only an already-formatted `citation` string, not a
+// raw ScriptureCitation.book — and that citation's own abbreviation isn't
+// authored consistently (e.g. "Luc"/"Luke", "Joann"/"John" across
+// src/data/propers/nocturn-readings/*.yml). Restricted to the four Gospels
+// since those are the only isGospel:true entries this needs to cover.
+const GOSPEL_CITATION_PREFIXES: [RegExp, string][] = [
+  [/^matt/i, 'matt'],
+  [/^marc|^mark/i, 'marc'],
+  [/^luc|^luke/i, 'luc'],
+  [/^joann?|^john/i, 'joan'],
+];
+
+/** Best-effort incipit lookup from an already-rendered citation string (e.g.
+ * "Luc 7:11-16" or "John 14:1-13") — tries the Latin form first, then
+ * English, since the Latin abbreviation is the more consistently authored
+ * one. Undefined when neither matches a known Gospel prefix. */
+export function getGospelIncipitFromCitation(
+  citation: Partial<Record<string, string>> | undefined,
+): { la: string; en: string } | undefined {
+  for (const candidate of [citation?.la, citation?.en]) {
+    if (!candidate) continue;
+    for (const [pattern, book] of GOSPEL_CITATION_PREFIXES) {
+      if (pattern.test(candidate)) return BOOK_INCIPITS[book];
+    }
+  }
+  return undefined;
+}