diff --git a/functions/src/lyrics.js b/functions/src/lyrics.js
index aedb356..1f1ecfb 100644
--- a/functions/src/lyrics.js
+++ b/functions/src/lyrics.js
@@ -10,6 +10,67 @@ const axios = require("axios");
 const admin = require("firebase-admin");
 const { refList } = require("../index");
 
+const STRUCTURE_PROMPT_LABELS = {
+  couplet: "couplet",
+  refrain: "refrain",
+  short_intro: "introduction instrumentale courte",
+  long_intro: "introduction instrumentale longue",
+  pre_chorus: "pré-refrain",
+};
+
+const STRUCTURE_ALIASES = {
+  "short intro": "short_intro",
+  "introduction instrumentale courte": "short_intro",
+  "intro instrumentale courte": "short_intro",
+  "long intro": "long_intro",
+  "introduction instrumentale longue": "long_intro",
+  "intro instrumentale longue": "long_intro",
+  "pré-refrain": "pre_chorus",
+  "pre-refrain": "pre_chorus",
+  "pre chorus": "pre_chorus",
+  "pre-chorus": "pre_chorus",
+  prechorus: "pre_chorus",
+};
+
+const normalizeStructureValue = (value) => {
+  const raw = String(value || "").trim().toLowerCase();
+  if (!raw) return "";
+  if (STRUCTURE_PROMPT_LABELS[raw]) return raw;
+  if (STRUCTURE_ALIASES[raw]) return STRUCTURE_ALIASES[raw];
+  const sanitized = raw.replace(/[^a-z0-9]+/g, "_").replace(/^_+|_+$/g, "");
+  if (STRUCTURE_PROMPT_LABELS[sanitized]) return sanitized;
+  if (STRUCTURE_ALIASES[sanitized]) return STRUCTURE_ALIASES[sanitized];
+  return sanitized;
+};
+
+const sanitizeStructureEntries = (structure = []) => {
+  if (!Array.isArray(structure)) return [];
+  const output = [];
+  structure.forEach((entry) => {
+    const normalized = normalizeStructureValue(entry);
+    if (!normalized) return;
+    if (normalized === "short_intro" || normalized === "long_intro") {
+      const existingIndex = output.findIndex(
+        (item) => item === "short_intro" || item === "long_intro",
+      );
+      if (existingIndex !== -1) output.splice(existingIndex, 1);
+      output.push(normalized);
+      return;
+    }
+    if (normalized === "pre_chorus") {
+      if (!output.includes("pre_chorus")) output.push("pre_chorus");
+      return;
+    }
+    output.push(normalized);
+  });
+  return output;
+};
+
+const mapStructureToPrompt = (structure = []) =>
+  sanitizeStructureEntries(structure).map(
+    (entry) => STRUCTURE_PROMPT_LABELS[entry] || entry,
+  );
+
 const TOXIC_KEYWORDS = [
   /\bnazis?\b/i,
   /\bnazisme\b/i,
@@ -39,8 +100,9 @@ const buildModerationBrief = ({
     `<RIMES>${Array.isArray(rhymes) ? rhymes.join(", ") : rhymes || ""}</RIMES>`,
   ];
 
-  if (Array.isArray(structure) && structure.length) {
-    sections.push(`<STRUCTURE>${structure.join(" | ")}</STRUCTURE>`);
+  const promptStructure = mapStructureToPrompt(structure);
+  if (promptStructure.length) {
+    sections.push(`<STRUCTURE>${promptStructure.join(" | ")}</STRUCTURE>`);
   }
 
   return `<BRIEF_UTILISATEUR>\n${sections.join("\n")}\n</BRIEF_UTILISATEUR>`;
@@ -76,17 +138,29 @@ exports.generateLyrics = onCall({}, async ({ auth = {}, data = {} }) => {
       style = "",
       audience = "",
       emotion = "",
-      structure = ["couplet", "refrain", "couplet", "refrain"],
+      structure: rawStructure = [
+        "couplet",
+        "refrain",
+        "couplet",
+        "refrain",
+      ],
       rhymes = "",
     } = data;
 
+    const sanitizedStructure = sanitizeStructureEntries(rawStructure);
+    const promptStructure = sanitizedStructure.length
+      ? sanitizedStructure.map(
+          (entry) => STRUCTURE_PROMPT_LABELS[entry] || entry,
+        )
+      : [];
+
     const moderationPayload = {
       objective,
       context,
       style,
       audience,
       emotion,
-      structure,
+      structure: promptStructure,
       rhymes,
     };
 
@@ -137,7 +211,7 @@ Génère un titre accrocheur et mémorable en plus des paroles, tout en respecta
 Retourne uniquement un JSON conforme au schéma fourni, sans ajouter d'autres textes.
     `.trim();
 
-    const structureTags = (Array.isArray(structure) ? structure : [])
+    const structureTags = (Array.isArray(promptStructure) ? promptStructure : [])
       .map((part, index) => {
         const content = part || "";
         return `  <SECTION ordre="${index + 1}">${content}</SECTION>`;
@@ -191,8 +265,7 @@ ${structureTags || fallbackStructureTags}
             type: z
               .string()
               .describe(
-                'Type de section : "couplet" ou "refrain" ' +
-                  "selon la structure",
+                "Type de section : respecter exactement le nom de la section demandé dans la structure",
               ),
             lyrics: z
               .string()
diff --git a/src/screens/Library/MusicDetails.web.js b/src/screens/Library/MusicDetails.web.js
index b3dceb1..9de8558 100644
--- a/src/screens/Library/MusicDetails.web.js
+++ b/src/screens/Library/MusicDetails.web.js
@@ -37,6 +37,11 @@ import Page from "../../layouts/Page";
 import { Palette } from "../../styles";
 import { FONT_FAMILY } from "../../styles/Fonts";
 import Style, { gutters, size } from "../../styles/Style";
+import {
+  formatStructureLabel,
+  getSegmentMeta,
+  normalizeStructureType,
+} from "../../utils/songStructure";
 
 // 20 secondes
 const timeBeforeIncrement = 20000;
@@ -325,12 +330,14 @@ const MusicDetails = ({ route }) => {
   const description = useMemo(() => {
     // Build a readable text from lyrics with section labels
     if (Array.isArray(project?.lyrics)) {
+      const counts = {};
       return project.lyrics
         .map((s) => {
           const body = (s?.lyrics || "").trim();
           if (!body) return null;
-          const t = (s?.type || "").toLowerCase();
-          const label = t === "refrain" ? "Refrain" : "Couplet";
+          const type = normalizeStructureType(s?.type);
+          counts[type] = (counts[type] || 0) + 1;
+          const label = formatStructureLabel(type, counts[type]);
           return `[${label}]\n${body}`;
         })
         .filter(Boolean)
@@ -370,22 +377,41 @@ const MusicDetails = ({ route }) => {
     if (!match) return null;
     const label = match[1]?.trim() || "";
     const lower = label.toLowerCase();
+
     let type = "section";
     if (lower.includes("refrain") || lower.includes("chorus")) type = "refrain";
     else if (lower.includes("couplet") || lower.includes("verse"))
       type = "couplet";
+    else if (
+      lower.includes("pré") ||
+      lower.includes("prechorus") ||
+      lower.includes("pre-chorus") ||
+      lower.includes("pre chorus") ||
+      lower.includes("pre-refrain")
+    )
+      type = "pre_chorus";
     else if (lower.includes("bridge")) type = "bridge";
-    else if (lower.includes("intro")) type = "intro";
+    else if (lower.includes("intro")) {
+      if (lower.includes("long")) type = "long_intro";
+      else type = "short_intro";
+    }
     const indexMatch = label.match(/(\d+)/);
     const index = indexMatch ? Number(indexMatch[1]) : undefined;
     return { label, type, index };
   };
   const formatSectionLabel = (type, index, fallback) => {
     if (fallback) return fallback;
-    if (type === "refrain") return index > 1 ? `Refrain ${index}` : "Refrain";
-    if (type === "couplet") return index > 1 ? `Couplet ${index}` : "Couplet";
+    const normalized = normalizeStructureType(type);
+    const meta = getSegmentMeta(normalized);
+    if (meta) {
+      return formatStructureLabel(normalized, index);
+    }
+    if (normalized === "refrain")
+      return index > 1 ? `Refrain ${index}` : "Refrain";
+    if (normalized === "couplet")
+      return index > 1 ? `Couplet ${index}` : "Couplet";
     if (type === "bridge") return index > 1 ? `Pont ${index}` : "Pont";
-    if (type === "intro") return "Intro";
+    if (type === "intro") return index > 1 ? `Intro ${index}` : "Intro";
     return index > 1 ? `Section ${index}` : "Section";
   };
 
diff --git a/src/screens/Studio/ComposeSong.js b/src/screens/Studio/ComposeSong.js
index e405002..db8a8cf 100644
--- a/src/screens/Studio/ComposeSong.js
+++ b/src/screens/Studio/ComposeSong.js
@@ -10,6 +10,7 @@ import { Routes } from "../../navigation";
 import { goBack, navigate } from "../../navigation/NavigationService";
 import { useUser } from "../../providers/UserDataProvider";
 import { gutters } from "../../styles";
+import { normalizeStructureType } from "../../utils/songStructure";
 import ChooseGenre from "./ChooseGenre";
 import ChooseInstruments from "./ChooseInstruments";
 import ChooseRhythm from "./ChooseRhythm";
@@ -51,7 +52,7 @@ const ComposeSong = () => {
     let lyricsArr = [];
     if (Array.isArray(selectedProject?.lyrics)) {
       lyricsArr = selectedProject.lyrics.map((s) => ({
-        type: (s?.type || "").toLowerCase(),
+        type: normalizeStructureType(s?.type),
         lyrics: s?.lyrics || "",
       }));
     } else {
diff --git a/src/screens/Studio/ComposeSong.web.js b/src/screens/Studio/ComposeSong.web.js
index 1e0fc91..794c4e2 100644
--- a/src/screens/Studio/ComposeSong.web.js
+++ b/src/screens/Studio/ComposeSong.web.js
@@ -15,6 +15,7 @@ import { Routes } from "../../navigation";
 import { goBack, navigate } from "../../navigation/NavigationService";
 import { useUser } from "../../providers/UserDataProvider";
 import { gutters } from "../../styles";
+import { normalizeStructureType } from "../../utils/songStructure";
 import ChooseGenre from "./ChooseGenre";
 import ChooseInstruments from "./ChooseInstruments";
 import ChooseRhythm from "./ChooseRhythm";
@@ -54,7 +55,7 @@ const ComposeSong = () => {
     let lyricsArr = [];
     if (Array.isArray(selectedProject?.lyrics)) {
       lyricsArr = selectedProject.lyrics.map((s) => ({
-        type: (s?.type || "").toLowerCase(),
+        type: normalizeStructureType(s?.type),
         lyrics: s?.lyrics || "",
       }));
     } else {
diff --git a/src/screens/Writing/CreateLyricsWithAi.js b/src/screens/Writing/CreateLyricsWithAi.js
index ee8e924..aa6f20b 100644
--- a/src/screens/Writing/CreateLyricsWithAi.js
+++ b/src/screens/Writing/CreateLyricsWithAi.js
@@ -12,6 +12,7 @@ import { Routes } from "../../navigation";
 import { goBack, navigate } from "../../navigation/NavigationService";
 import { useUser } from "../../providers/UserDataProvider";
 import { gutters } from "../../styles";
+import { sanitizeStructureList } from "../../utils/songStructure";
 import CreatingLyrics from "./CreatingLyrics";
 import CustomizeSongStructure from "./CustomizeSongStructure";
 import EmotionConvey from "./EmotionConvey";
@@ -140,11 +141,24 @@ const CreateLyricsWithAi = () => {
 
     // Structure personnalisée: prioriser selections.customStructure puis config.structure
     const savedCustom = Array.isArray(sel.customStructure)
-      ? sel.customStructure
+      ? sanitizeStructureList(sel.customStructure)
       : null;
-    const cfgStructure = Array.isArray(cfg.structure) ? cfg.structure : null;
-    if (!Array.isArray(customStructure) && (savedCustom || cfgStructure)) {
-      setCustomStructure(savedCustom || cfgStructure);
+    const cfgStructure = Array.isArray(cfg.structure)
+      ? sanitizeStructureList(cfg.structure)
+      : null;
+    const fallbackStructure =
+      savedCustom && savedCustom.length ? savedCustom : cfgStructure;
+    if (!Array.isArray(customStructure) && fallbackStructure?.length) {
+      setCustomStructure(fallbackStructure);
+    } else if (
+      Array.isArray(customStructure) &&
+      fallbackStructure?.length &&
+      (customStructure.length !== fallbackStructure.length ||
+        customStructure.some(
+          (value, idx) => value !== fallbackStructure[idx]
+        ))
+    ) {
+      setCustomStructure(fallbackStructure);
     }
   }, [selectedProject]);
 
@@ -167,7 +181,8 @@ const CreateLyricsWithAi = () => {
           for (let i = 0; i < count; i++) result.push("refrain");
         }
       });
-      return result.length ? result : null;
+      const sanitizedResult = sanitizeStructureList(result);
+      return sanitizedResult.length ? sanitizedResult : null;
     } catch (e) {
       return null;
     }
@@ -187,6 +202,13 @@ const CreateLyricsWithAi = () => {
     const resolvedStyle = shouldUseOtherStyle
       ? persistedOtherStyle || undefined
       : style || undefined;
+    const sanitizedCustom =
+      Array.isArray(customStructure) && customStructure.length > 0
+        ? sanitizeStructureList(customStructure)
+        : [];
+    const sanitizedParsed = Array.isArray(parsedStructure)
+      ? sanitizeStructureList(parsedStructure)
+      : [];
 
     return {
       objective: resolvedObjective,
@@ -198,9 +220,11 @@ const CreateLyricsWithAi = () => {
       style: resolvedStyle,
       audience: audience?.trim() ? audience.trim() : undefined,
       structure:
-        (Array.isArray(customStructure) && customStructure.length > 0
-          ? customStructure
-          : parsedStructure) || undefined,
+        sanitizedCustom.length > 0
+          ? sanitizedCustom
+          : sanitizedParsed.length > 0
+            ? sanitizedParsed
+            : undefined,
       rhymes: rhymes || undefined,
     };
   }, [
@@ -276,12 +300,13 @@ const CreateLyricsWithAi = () => {
     // Si l'utilisateur a déjà des paroles et vient de finir CustomizeSongStructure (index 6),
     // sauter Rhymes et CreatingLyrics et aller directement sur Lyrics
     if (hasLyrics && selectedIndex === 6) {
-      const chosenStructure =
+      const chosenStructure = sanitizeStructureList(
         Array.isArray(customStructure) && customStructure.length > 0
           ? customStructure
           : Array.isArray(parsedStructure)
             ? parsedStructure
-            : [];
+            : []
+      );
       await updateProjectData({
         config: { structure: chosenStructure },
         selections: {
@@ -294,7 +319,7 @@ const CreateLyricsWithAi = () => {
           audience,
           structure,
           parsedStructure,
-          customStructure,
+          customStructure: sanitizeStructureList(customStructure),
           rhymes,
         },
         hasLyrics: true,
diff --git a/src/screens/Writing/CreateLyricsWithAi.web.js b/src/screens/Writing/CreateLyricsWithAi.web.js
index 46bcffd..743de56 100644
--- a/src/screens/Writing/CreateLyricsWithAi.web.js
+++ b/src/screens/Writing/CreateLyricsWithAi.web.js
@@ -10,6 +10,7 @@ import { Routes } from "../../navigation";
 import { goBack, navigate } from "../../navigation/NavigationService";
 import { useUser } from "../../providers/UserDataProvider";
 import { gutters } from "../../styles";
+import { sanitizeStructureList } from "../../utils/songStructure";
 import CreatingLyrics from "./CreatingLyrics";
 import CustomizeSongStructure from "./CustomizeSongStructure";
 import EmotionConvey from "./EmotionConvey";
@@ -138,11 +139,24 @@ const CreateLyricsWithAi = () => {
 
     // Structure personnalisée: prioriser selections.customStructure puis config.structure
     const savedCustom = Array.isArray(sel.customStructure)
-      ? sel.customStructure
+      ? sanitizeStructureList(sel.customStructure)
       : null;
-    const cfgStructure = Array.isArray(cfg.structure) ? cfg.structure : null;
-    if (!Array.isArray(customStructure) && (savedCustom || cfgStructure)) {
-      setCustomStructure(savedCustom || cfgStructure);
+    const cfgStructure = Array.isArray(cfg.structure)
+      ? sanitizeStructureList(cfg.structure)
+      : null;
+    const fallbackStructure =
+      savedCustom && savedCustom.length ? savedCustom : cfgStructure;
+    if (!Array.isArray(customStructure) && fallbackStructure?.length) {
+      setCustomStructure(fallbackStructure);
+    } else if (
+      Array.isArray(customStructure) &&
+      fallbackStructure?.length &&
+      (customStructure.length !== fallbackStructure.length ||
+        customStructure.some(
+          (value, idx) => value !== fallbackStructure[idx]
+        ))
+    ) {
+      setCustomStructure(fallbackStructure);
     }
   }, [selectedProject]);
 
@@ -172,7 +186,8 @@ const CreateLyricsWithAi = () => {
           for (let i = 0; i < count; i++) result.push("refrain");
         }
       });
-      return result.length ? result : null;
+      const sanitizedResult = sanitizeStructureList(result);
+      return sanitizedResult.length ? sanitizedResult : null;
     } catch (e) {
       return null;
     }
@@ -192,6 +207,13 @@ const CreateLyricsWithAi = () => {
     const resolvedStyle = shouldUseOtherStyle
       ? persistedOtherStyle || undefined
       : style || undefined;
+    const sanitizedCustom =
+      Array.isArray(customStructure) && customStructure.length > 0
+        ? sanitizeStructureList(customStructure)
+        : [];
+    const sanitizedParsed = Array.isArray(parsedStructure)
+      ? sanitizeStructureList(parsedStructure)
+      : [];
 
     return {
       objective: resolvedObjective,
@@ -203,9 +225,11 @@ const CreateLyricsWithAi = () => {
       style: resolvedStyle,
       audience: audience?.trim() ? audience.trim() : undefined,
       structure:
-        (Array.isArray(customStructure) && customStructure.length > 0
-          ? customStructure
-          : parsedStructure) || undefined,
+        sanitizedCustom.length > 0
+          ? sanitizedCustom
+          : sanitizedParsed.length > 0
+            ? sanitizedParsed
+            : undefined,
       rhymes: rhymes || undefined,
     };
   }, [
@@ -281,12 +305,13 @@ const CreateLyricsWithAi = () => {
     // Si l'utilisateur a déjà des paroles et vient de finir CustomizeSongStructure (index 6),
     // sauter Rhymes et CreatingLyrics et aller directement sur Lyrics
     if (hasLyrics && selectedIndex === 6) {
-      const chosenStructure =
+      const chosenStructure = sanitizeStructureList(
         Array.isArray(customStructure) && customStructure.length > 0
           ? customStructure
           : Array.isArray(parsedStructure)
             ? parsedStructure
-            : [];
+            : []
+      );
       await updateProjectData({
         config: { structure: chosenStructure },
         selections: {
@@ -299,7 +324,7 @@ const CreateLyricsWithAi = () => {
           audience,
           structure,
           parsedStructure,
-          customStructure,
+          customStructure: sanitizeStructureList(customStructure),
           rhymes,
         },
         hasLyrics: true,
diff --git a/src/screens/Writing/CreatingLyrics.js b/src/screens/Writing/CreatingLyrics.js
index 0fad850..c902994 100644
--- a/src/screens/Writing/CreatingLyrics.js
+++ b/src/screens/Writing/CreatingLyrics.js
@@ -12,6 +12,7 @@ import { navigate } from "../../navigation/NavigationService";
 import { useUser } from "../../providers/UserDataProvider";
 import { Palette, Style } from "../../styles";
 import { FONT_FAMILY } from "../../styles/Fonts";
+import { sanitizeStructureList } from "../../utils/songStructure";
 
 const CreatingLyrics = ({ active, config, selections }) => {
   const [progress, setProgress] = useState(0);
@@ -58,6 +59,7 @@ const CreatingLyrics = ({ active, config, selections }) => {
         console.log("🚀 [CreatingLyrics] Lancement de la génération", {
           platform: Platform.OS,
         });
+        const sanitizedStructure = sanitizeStructureList(config?.structure);
         const callable = firebase
           .functions()
           .httpsCallable("lyrics-generateLyrics");
@@ -67,10 +69,32 @@ const CreatingLyrics = ({ active, config, selections }) => {
           emotion: config?.emotion,
           style: config?.style,
           audience: config?.audience,
-          structure: config?.structure,
+          structure: sanitizedStructure,
           rhymes: config?.rhymes,
         });
-        setResult(data);
+        const rawLyrics = Array.isArray(data?.lyrics) ? data.lyrics : [];
+        const normalizedLyrics = rawLyrics.map((section) => {
+          const sanitizedType =
+            sanitizeStructureList([section?.type])[0] || section?.type || "";
+          return {
+            ...section,
+            type: sanitizedType,
+          };
+        });
+        const alignedLyrics =
+          sanitizedStructure.length > 0 &&
+          sanitizedStructure.length === normalizedLyrics.length
+            ? normalizedLyrics.map((section, index) => ({
+                ...section,
+                type: sanitizedStructure[index],
+              }))
+            : normalizedLyrics;
+        const processedResult = {
+          ...data,
+          lyrics: alignedLyrics,
+          structure: sanitizedStructure,
+        };
+        setResult(processedResult);
         setProgress(100);
         console.log("✨ [CreatingLyrics] Génération réussie");
       } catch (e) {
@@ -106,12 +130,44 @@ const CreatingLyrics = ({ active, config, selections }) => {
         setSaved(true);
         await setIsLoading(true);
         console.log("💾 [CreatingLyrics] Sauvegarde automatique des paroles");
+        const sanitizedStructure = sanitizeStructureList(
+          result?.structure || config?.structure
+        );
+        const baseConfig =
+          config && typeof config === "object" && !Array.isArray(config)
+            ? { ...config }
+            : {};
+        if (sanitizedStructure.length > 0) {
+          baseConfig.structure = sanitizedStructure;
+        } else if (Object.prototype.hasOwnProperty.call(baseConfig, "structure")) {
+          delete baseConfig.structure;
+        }
+        const persistedConfig =
+          Object.keys(baseConfig).length > 0 ? baseConfig : null;
+
+        let persistedSelections =
+          selections && typeof selections === "object" && !Array.isArray(selections)
+            ? { ...selections }
+            : null;
+        if (persistedSelections) {
+          if ("customStructure" in persistedSelections) {
+            persistedSelections.customStructure = sanitizeStructureList(
+              persistedSelections.customStructure
+            );
+          }
+          if ("parsedStructure" in persistedSelections) {
+            persistedSelections.parsedStructure = sanitizeStructureList(
+              persistedSelections.parsedStructure
+            );
+          }
+        }
+
         await updateProjectData({
           title: result?.title || "",
           lyrics: Array.isArray(result?.lyrics) ? result.lyrics : [],
           description: result?.lyricsDescription,
-          config: config || null,
-          selections: selections || null,
+          config: persistedConfig,
+          selections: persistedSelections,
           hasLyrics: false,
         });
         navigate(Routes.Lyrics);
diff --git a/src/screens/Writing/CustomizeSongStructure.js b/src/screens/Writing/CustomizeSongStructure.js
index e1e33a2..104e1ca 100644
--- a/src/screens/Writing/CustomizeSongStructure.js
+++ b/src/screens/Writing/CustomizeSongStructure.js
@@ -1,103 +1,165 @@
 import { BlurView } from "expo-blur";
-import React, { useEffect, useMemo } from "react";
+import React, { useEffect, useMemo, useState } from "react";
 import {
   FlatList,
   Image,
   Platform,
   StyleSheet,
   Text,
+  TouchableOpacity,
   View,
 } from "react-native";
 import Animated, { useAnimatedRef } from "react-native-reanimated";
 import Sortable from "react-native-sortables";
 import { icons } from "../../assets";
-import { Palette, Style } from "../../styles";
+import { Palette } from "../../styles";
 import { FONT_FAMILY } from "../../styles/Fonts";
+import {
+  formatStructureLabel,
+  getSegmentMeta,
+  OPTIONAL_STRUCTURE_SEGMENTS,
+  sanitizeStructureList,
+} from "../../utils/songStructure";
 import CreateLyricsHeader from "./components/CreateLyricsHeader";
 
-// baseStructure: array like ['couplet','refrain',...]
-// onChange: callback that receives array like ['couplet','refrain',...]
+const randomSuffix = () => Math.random().toString(36).slice(2, 8);
+const createItemId = (type) => `${type}-${Date.now()}-${randomSuffix()}`;
+const createSortableItem = (type, index = 0) => ({
+  id: `${type}-${index}-${randomSuffix()}`,
+  type,
+  value: type,
+});
+
+const buildInitialItems = (structure = []) =>
+  sanitizeStructureList(structure).map((type, index) =>
+    createSortableItem(type, index)
+  );
+
 const CustomizeSongStructure = ({ baseStructure = [], onChange }) => {
   const scrollRef = useAnimatedRef();
+  const sanitizedBase = useMemo(
+    () => sanitizeStructureList(baseStructure),
+    [baseStructure]
+  );
+  const [sortableItems, setSortableItems] = useState(() =>
+    buildInitialItems(sanitizedBase)
+  );
 
-  // Build stable keyed data like { 'couplet-1': { label, value }, ... }
-  const data = useMemo(() => {
-    const counters = { couplet: 0, refrain: 0 };
-    const out = {};
-    (baseStructure || []).forEach((type) => {
-      const key = (type || "").toLowerCase();
-      counters[key] = (counters[key] || 0) + 1;
-      const idx = counters[key];
-      const id = `${key}-${idx}`;
-      out[id] = {
-        id,
-        label: `${key === "couplet" ? "Couplet" : "Refrain"} ${idx}`,
-        value: key,
+  useEffect(() => {
+    setSortableItems((prev) => {
+      const prevTypes = prev.map((item) => item.type);
+      if (
+        prevTypes.length === sanitizedBase.length &&
+        prevTypes.every((type, index) => type === sanitizedBase[index])
+      ) {
+        return prev;
+      }
+      return buildInitialItems(sanitizedBase);
+    });
+  }, [sanitizedBase]);
+
+  useEffect(() => {
+    const values = sortableItems.map((item) => item.type).filter(Boolean);
+    onChange?.(values);
+  }, [sortableItems, onChange]);
+
+  const labeledItems = useMemo(() => {
+    const counts = {};
+    return sortableItems.map((item) => {
+      const baseType = item.type || item.value;
+      const nextCount = (counts[baseType] || 0) + 1;
+      counts[baseType] = nextCount;
+      return {
+        ...item,
+        type: baseType,
+        value: baseType,
+        label: formatStructureLabel(baseType, nextCount),
+        sortable: true,
       };
     });
-    return out;
-  }, [baseStructure]);
+  }, [sortableItems]);
 
-  const items = useMemo(() => Object.values(data), [data]);
+  const optionalSegments = useMemo(
+    () =>
+      OPTIONAL_STRUCTURE_SEGMENTS.map((type) => {
+        const meta = getSegmentMeta(type);
+        return { type, label: meta?.label || formatStructureLabel(type, 1) };
+      }),
+    []
+  );
 
-  const newItems = [
-    {
-      id: "short_intro",
-      label: "Introduction instrumentale courte",
-      value: "short_intro",
-    },
-    {
-      id: "long_intro",
-      label: "Introduction instrumentale longue",
-      value: "long_intro",
-    },
-    {
-      id: "pre_chorus",
-      label: "Pré-refrain",
-      value: "pre_chorus",
-    },
-  ];
-  // Initialize parent with current order (so it's saved even without drag)
-  useEffect(() => {
-    const initialValues = (items || []).map((it) => it?.value).filter(Boolean);
-    onChange?.(initialValues);
-    // We only want to run when baseStructure-derived items change
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [items.length]);
+  const selectedTypes = useMemo(() => {
+    const set = new Set();
+    sortableItems.forEach((item) => {
+      if (item?.type) set.add(item.type);
+      else if (item?.value) set.add(item.value);
+    });
+    return set;
+  }, [sortableItems]);
 
-  const Row = ({ item: rowData }) => (
-    <View style={styles.itemContainer}>
-      <BlurView
-        intensity={Platform.OS !== "ios" ? 10 : 30}
-        style={styles.rowBlur}
-        // experimentalBlurMethod={Platform.OS !== "ios" ? "dimezisBlurView" : "none"}
+  const toggleOptionalSegment = (type) => {
+    setSortableItems((prev) => {
+      const existsIndex = prev.findIndex((item) => item.type === type);
+      if (existsIndex !== -1) {
+        return prev.filter((item) => item.type !== type);
+      }
+      const meta = getSegmentMeta(type);
+      let next = [...prev];
+      if (meta?.exclusiveGroup) {
+        next = next.filter((item) => {
+          const itemMeta = getSegmentMeta(item.type || item.value);
+          return itemMeta?.exclusiveGroup !== meta.exclusiveGroup;
+        });
+      }
+      next.push(createSortableItem(type, next.length));
+      return next;
+    });
+  };
+
+  const Row = ({ item: rowData, onPress }) => {
+    const isButton = typeof onPress === "function";
+    const Wrapper = isButton ? TouchableOpacity : View;
+    const selected = rowData?.selected;
+    const icon = rowData?.icon;
+    return (
+      <Wrapper
+        onPress={onPress}
+        activeOpacity={0.8}
+        style={isButton ? styles.touchable : undefined}
       >
-        <View style={{ ...Style.containerSpaceBetween, alignItems: "center" }}>
-          <View>
-            <View>
-              <View>
-                <View />
-              </View>
-            </View>
-            <View>
-              <View />
-            </View>
-          </View>
-          <View style={{ flex: 1, justifyContent: "center" }}>
-            <View>
+        <View
+          style={[
+            styles.itemContainer,
+            selected && styles.selectedItem,
+            rowData?.sortable && styles.sortableItem,
+          ]}
+        >
+          <BlurView
+            intensity={Platform.OS !== "ios" ? 10 : 30}
+            style={[
+              styles.rowBlur,
+              selected && styles.selectedBlur,
+              isButton && styles.buttonBlur,
+            ]}
+          >
+            <View style={styles.rowContent}>
               <Text style={styles.rowText}>{rowData?.label || ""}</Text>
             </View>
-          </View>
-          {/* Render handle only for items that come from the sortable data (have an id like 'couplet-1') */}
-          {String(rowData?.id || "").includes("-") ? (
-            <Sortable.Handle>
-              <Image source={icons.dragDots} style={styles.handleIcon} />
-            </Sortable.Handle>
-          ) : null}
+            {rowData?.sortable ? (
+              <Sortable.Handle>
+                <Image source={icons.dragDots} style={styles.handleIcon} />
+              </Sortable.Handle>
+            ) : (
+              <Image
+                source={icon || (selected ? icons.check : icons.add)}
+                style={[styles.optionIcon]}
+              />
+            )}
+          </BlurView>
         </View>
-      </BlurView>
-    </View>
-  );
+      </Wrapper>
+    );
+  };
 
   return (
     <View style={{ flex: 1, gap: 10, marginTop: 16 }}>
@@ -115,29 +177,42 @@ const CustomizeSongStructure = ({ baseStructure = [], onChange }) => {
             <Sortable.Grid
               columns={1}
               rowGap={12}
-              data={items}
+              data={labeledItems}
               renderItem={({ item }) => <Row item={item} />}
               customHandle
-              // Enable auto-scroll when dragging near edges
               scrollableRef={scrollRef}
               onDragEnd={({ data: newData }) => {
-                const values = (newData || [])
-                  .map((it) => it?.value)
-                  .filter(Boolean);
-                onChange?.(values);
+                const next = (newData || []).map((it, index) => {
+                  const nextType = it?.type || it?.value;
+                  return {
+                    id: it?.id || createItemId(nextType || `section-${index}`),
+                    type: nextType,
+                    value: nextType,
+                  };
+                });
+                setSortableItems(next.filter((item) => item.type));
               }}
             />
             <FlatList
-              data={newItems}
+              data={optionalSegments}
               gap={12}
-              renderItem={({ item }) => (
-                <View style={{ marginTop: 12 }}>
-                  <Row item={item} />
-                </View>
-              )}
-              keyExtractor={(item) => item.id}
+              renderItem={({ item }) => {
+                const selected = selectedTypes.has(item.type);
+                return (
+                  <View style={{ marginTop: 12 }}>
+                    <Row
+                      item={{
+                        ...item,
+                        sortable: false,
+                        selected,
+                      }}
+                      onPress={() => toggleOptionalSegment(item.type)}
+                    />
+                  </View>
+                );
+              }}
+              keyExtractor={(item) => item.type}
               contentContainerStyle={{ paddingBottom: 24 }}
-              // Prevent FlatList from capturing scroll gestures so Sortable can handle drags
               scrollEnabled={false}
               nestedScrollEnabled={false}
             />
@@ -151,6 +226,9 @@ const CustomizeSongStructure = ({ baseStructure = [], onChange }) => {
 export default CustomizeSongStructure;
 
 const styles = StyleSheet.create({
+  touchable: {
+    width: "100%",
+  },
   itemContainer: {
     height: 54,
     backgroundColor: Palette.glass,
@@ -165,13 +243,32 @@ const styles = StyleSheet.create({
     shadowRadius: 3.84,
     elevation: 5,
   },
+  sortableItem: {
+    marginBottom: 0,
+  },
+  selectedItem: {
+    borderWidth: 1,
+    borderColor: Palette.white,
+  },
   rowBlur: {
     flex: 1,
     backgroundColor: Palette.glass,
     justifyContent: "center",
     paddingHorizontal: 12,
+    flexDirection: "row",
+    alignItems: "center",
     height: "100%",
   },
+  buttonBlur: {
+    justifyContent: "space-between",
+  },
+  selectedBlur: {
+    backgroundColor: Palette.transparentWhite,
+  },
+  rowContent: {
+    flex: 1,
+    justifyContent: "center",
+  },
   rowText: {
     fontSize: 16,
     color: Palette.white,
@@ -182,4 +279,9 @@ const styles = StyleSheet.create({
     height: 22,
     tintColor: Palette.white,
   },
+  optionIcon: {
+    width: 20,
+    height: 20,
+    tintColor: Palette.white,
+  },
 });
diff --git a/src/screens/Writing/CustomizeSongStructure.web.js b/src/screens/Writing/CustomizeSongStructure.web.js
index b70df4f..20b0601 100644
--- a/src/screens/Writing/CustomizeSongStructure.web.js
+++ b/src/screens/Writing/CustomizeSongStructure.web.js
@@ -1,30 +1,30 @@
 import React from "react";
-import { Image, StyleSheet, Text, View } from "react-native";
+import { Image, StyleSheet, Text, TouchableOpacity, View } from "react-native";
 import { icons } from "../../assets";
 import { Palette } from "../../styles";
 import { FONT_FAMILY } from "../../styles/Fonts";
+import {
+  formatStructureLabel,
+  getSegmentMeta,
+  OPTIONAL_STRUCTURE_SEGMENTS,
+  sanitizeStructureList,
+} from "../../utils/songStructure";
 import CreateLyricsHeader from "./components/CreateLyricsHeader";
 
 const ROW_HEIGHT = 54;
-const VALID_SEGMENTS = ["couplet", "refrain"];
 
 const getScrollY = () => (typeof window !== "undefined" ? window.scrollY : 0);
 
-const sanitizeStructure = (structure = []) =>
-  structure
-    .map((segment) => `${segment}`.trim().toLowerCase())
-    .filter((segment) => VALID_SEGMENTS.includes(segment));
+const randomSuffix = () => Math.random().toString(36).slice(2, 8);
 
 const buildItems = (structure = []) => {
-  const counters = { couplet: 0, refrain: 0 };
+  const counters = {};
   return structure.map((segment, index) => {
-    counters[segment] += 1;
+    counters[segment] = (counters[segment] || 0) + 1;
     return {
-      id: `${segment}-${index}-${counters[segment]}`,
+      id: `${segment}-${index}-${randomSuffix()}`,
+      type: segment,
       value: segment,
-      label: `${segment === "couplet" ? "Couplet" : "Refrain"} ${
-        counters[segment]
-      }`,
     };
   });
 };
@@ -41,7 +41,7 @@ const clamp = (value, min, max) => Math.max(min, Math.min(max, value));
 
 const CustomizeSongStructure = ({ baseStructure = [], onChange }) => {
   const sanitized = React.useMemo(
-    () => sanitizeStructure(baseStructure),
+    () => sanitizeStructureList(baseStructure),
     [baseStructure]
   );
   const [items, setItems] = React.useState(() => buildItems(sanitized));
@@ -55,11 +55,10 @@ const CustomizeSongStructure = ({ baseStructure = [], onChange }) => {
   React.useEffect(() => {
     console.debug("[CustomizeSongStructure.web] sanitized", sanitized);
     setItems((prev) => {
-      if (
-        prev.length === sanitized.length &&
-        prev.every((item, idx) => item.value === sanitized[idx])
-      ) {
-        return prev;
+      const prevTypes = prev.map((item) => item.type);
+      if (prevTypes.length === sanitized.length) {
+        const same = prevTypes.every((type, idx) => type === sanitized[idx]);
+        if (same) return prev;
       }
       return buildItems(sanitized);
     });
@@ -69,11 +68,59 @@ const CustomizeSongStructure = ({ baseStructure = [], onChange }) => {
 
   React.useEffect(() => {
     console.debug("[CustomizeSongStructure.web] items", items);
-    onChange?.(items.map((item) => item.value));
+    onChange?.(items.map((item) => item.type));
   }, [items, onChange]);
 
+  const labeledItems = React.useMemo(() => {
+    const counts = {};
+    return items.map((item) => {
+      counts[item.type] = (counts[item.type] || 0) + 1;
+      return {
+        ...item,
+        label: formatStructureLabel(item.type, counts[item.type]),
+      };
+    });
+  }, [items]);
+
+  const selectedTypes = React.useMemo(
+    () => new Set(items.map((item) => item.type)),
+    [items]
+  );
+
+  const optionalSegments = React.useMemo(
+    () =>
+      OPTIONAL_STRUCTURE_SEGMENTS.map((type) => {
+        const meta = getSegmentMeta(type);
+        return { type, label: meta?.label };
+      }),
+    []
+  );
+
+  const toggleOptionalSegment = React.useCallback((type) => {
+    setItems((prev) => {
+      const exists = prev.some((item) => item.type === type);
+      if (exists) {
+        return prev.filter((item) => item.type !== type);
+      }
+      const meta = getSegmentMeta(type);
+      let next = [...prev];
+      if (meta?.exclusiveGroup) {
+        next = next.filter((item) => {
+          const itemMeta = getSegmentMeta(item.type);
+          return itemMeta?.exclusiveGroup !== meta.exclusiveGroup;
+        });
+      }
+      next.push({
+        id: `${type}-${Date.now()}-${randomSuffix()}`,
+        type,
+        value: type,
+      });
+      return next;
+    });
+  }, []);
+
   const handleGrant = (index, event) => {
-    const item = items[index];
+    const item = labeledItems[index];
     if (!item) return;
     const rect = containerRef.current?.getBoundingClientRect();
     const scrollY = getScrollY();
@@ -132,13 +179,32 @@ const CustomizeSongStructure = ({ baseStructure = [], onChange }) => {
     }
   };
 
-  if (!items.length) {
+  if (!labeledItems.length) {
     return (
       <View style={{ flex: 1, gap: 10, marginTop: 16 }}>
         <CreateLyricsHeader
           title="Personnalise la structure de ta chanson"
           subTitle="Sélectionne une structure pour commencer"
         />
+        <View style={styles.optionsContainer}>
+          {optionalSegments.map((segment) => {
+            const selected = selectedTypes.has(segment.type);
+            return (
+              <TouchableOpacity
+                key={segment.type}
+                activeOpacity={0.85}
+                onPress={() => toggleOptionalSegment(segment.type)}
+                style={[styles.optionItem, selected && styles.selectedItem]}
+              >
+                <Text style={styles.optionText}>{segment.label}</Text>
+                <Image
+                  source={selected ? icons.check : icons.add}
+                  style={[styles.optionIcon]}
+                />
+              </TouchableOpacity>
+            );
+          })}
+        </View>
       </View>
     );
   }
@@ -150,7 +216,7 @@ const CustomizeSongStructure = ({ baseStructure = [], onChange }) => {
         subTitle="Glisse-dépose pour réorganiser"
       />
       <View style={styles.listContainer} ref={containerRef}>
-        {items.map((item, index) => (
+        {labeledItems.map((item, index) => (
           <View
             key={item.id}
             style={[
@@ -170,6 +236,28 @@ const CustomizeSongStructure = ({ baseStructure = [], onChange }) => {
           </View>
         ))}
       </View>
+      <View style={styles.optionsContainer}>
+        {optionalSegments.map((segment) => {
+          const selected = selectedTypes.has(segment.type);
+          return (
+            <TouchableOpacity
+              key={segment.type}
+              activeOpacity={0.85}
+              onPress={() => toggleOptionalSegment(segment.type)}
+              style={[styles.optionItem, selected && styles.selectedItem]}
+            >
+              <Text style={styles.optionText}>{segment.label}</Text>
+              <Image
+                source={selected ? icons.check : icons.add}
+                style={[
+                  styles.optionIcon,
+                  selected && styles.optionIconSelected,
+                ]}
+              />
+            </TouchableOpacity>
+          );
+        })}
+      </View>
     </View>
   );
 };
@@ -214,4 +302,38 @@ const styles = StyleSheet.create({
     tintColor: Palette.white,
     cursor: "grab",
   },
+  optionsContainer: {
+    marginTop: 16,
+    gap: 12,
+  },
+  optionItem: {
+    height: ROW_HEIGHT,
+    borderRadius: 14,
+    backgroundColor: Palette.glass,
+    shadowColor: "#00000040",
+    shadowOffset: { width: 0, height: 2 },
+    shadowOpacity: 0.25,
+    shadowRadius: 3.84,
+    elevation: 5,
+    overflow: "hidden",
+    paddingHorizontal: 16,
+    flexDirection: "row",
+    alignItems: "center",
+    justifyContent: "space-between",
+  },
+  optionText: {
+    fontSize: 16,
+    color: Palette.white,
+    fontFamily: FONT_FAMILY.InterRegular,
+  },
+  optionIcon: {
+    width: 20,
+    height: 20,
+    tintColor: Palette.white,
+  },
+
+  selectedItem: {
+    borderWidth: 1,
+    borderColor: Palette.white,
+  },
 });
diff --git a/src/screens/Writing/Lyrics.js b/src/screens/Writing/Lyrics.js
index 7c50abb..1ae48b0 100644
--- a/src/screens/Writing/Lyrics.js
+++ b/src/screens/Writing/Lyrics.js
@@ -15,6 +15,12 @@ import { navigate } from "../../navigation/NavigationService";
 import { useUser } from "../../providers/UserDataProvider";
 import { Palette, gutters } from "../../styles";
 import { FONT_FAMILY } from "../../styles/Fonts";
+import {
+  formatStructureLabel,
+  getSegmentMeta,
+  normalizeStructureType,
+  sanitizeStructureList,
+} from "../../utils/songStructure";
 import CustomInput from "./components/CustomInput";
 
 const Lyrics = ({ navigation }) => {
@@ -36,26 +42,23 @@ const Lyrics = ({ navigation }) => {
 
   const initial = useMemo(() => {
     const title = projectTitle || "";
-    const aiSections = Array.isArray(projectLyrics) ? projectLyrics : [];
-    // Respecter l'ordre de la structure choisie si disponible
+    const normalizedSections = Array.isArray(projectLyrics)
+      ? projectLyrics.map((s) => ({
+          type: normalizeStructureType(s?.type),
+          lyrics: s?.lyrics || "",
+        }))
+      : [];
     const targetStructure = Array.isArray(projectConfig?.structure)
-      ? projectConfig.structure.map((t) => (t || "").toLowerCase())
+      ? sanitizeStructureList(projectConfig.structure)
       : null;
 
-    // 1) Si des paroles existent déjà, les utiliser en priorité
-    if (aiSections.length) {
-      // Optionnel: si une structure cible de même longueur existe, garder l'ordre courant
-      // et harmoniser les types en minuscule.
+    if (normalizedSections.length) {
       return {
         title,
-        sections: aiSections.map((s) => ({
-          type: (s?.type || "").toLowerCase(),
-          lyrics: s?.lyrics || "",
-        })),
+        sections: normalizedSections,
       };
     }
 
-    // 2) Sinon, créer à partir de la structure si fournie
     if (targetStructure && targetStructure.length) {
       return {
         title,
@@ -63,7 +66,6 @@ const Lyrics = ({ navigation }) => {
       };
     }
 
-    // 3) Fallback vide
     return { title, sections: [] };
   }, [projectTitle, projectLyrics, projectConfig]);
 
@@ -133,17 +135,17 @@ const Lyrics = ({ navigation }) => {
       if (invalid) {
         alertMessage(
           "Champs incomplets",
-          "Chaque couplet et refrain doit contenir du texte."
+          "Chaque section doit contenir du texte."
         );
         return;
       }
       const normalizedNewLyrics = (sections || []).map((s) => ({
-        type: (s?.type || "").toLowerCase(),
+        type: normalizeStructureType(s?.type),
         lyrics: (s?.lyrics || "").trim(),
       }));
       const normalizedOldLyrics = Array.isArray(projectLyrics)
         ? projectLyrics.map((s) => ({
-            type: (s?.type || "").toLowerCase(),
+            type: normalizeStructureType(s?.type),
             lyrics: (s?.lyrics || "").trim(),
           }))
         : [];
@@ -264,6 +266,8 @@ const Lyrics = ({ navigation }) => {
     projectLyrics,
   ]);
 
+  const typeOccurrences = {};
+
   return (
     <Page
       backgroundImg={isWeb ? background.libraryBgWeb : background.writingBG}
@@ -332,19 +336,25 @@ const Lyrics = ({ navigation }) => {
               }}
             />
             {sections.map((s, idx) => {
-              // Calculer l'index humain par type
-              const type = (s?.type || "").toLowerCase();
-              const countBefore = sections
-                .slice(0, idx)
-                .filter((x) => (x?.type || "").toLowerCase() === type).length;
-              const labelBase = type === "refrain" ? "Refrain" : "Couplet";
-              const label = `${labelBase} ${countBefore + 1}`;
+              const normalizedType = normalizeStructureType(s?.type);
+              const key = normalizedType || "section";
+              typeOccurrences[key] = (typeOccurrences[key] || 0) + 1;
+              const occurrence = typeOccurrences[key];
+              const label = formatStructureLabel(key, occurrence);
+              const meta = getSegmentMeta(key);
+              const inputHeight =
+                typeof meta?.inputHeight === "number"
+                  ? meta.inputHeight
+                  : key === "refrain"
+                    ? 170
+                    : 225;
+              const placeholder = meta?.label || label;
               return (
                 <CustomInput
                   key={idx}
                   label={label}
-                  placeholder={labelBase}
-                  height={type === "refrain" ? 170 : 225}
+                  placeholder={placeholder}
+                  height={inputHeight}
                   value={s?.lyrics || ""}
                   setValue={(val) => setSectionAt(idx, val)}
                   onFocus={() => {
diff --git a/src/utils/songStructure.js b/src/utils/songStructure.js
new file mode 100644
index 0000000..935da45
--- /dev/null
+++ b/src/utils/songStructure.js
@@ -0,0 +1,191 @@
+const START_CASE_REGEX = /[_\-\s]+/g;
+
+const toStartCase = (value) => {
+  const str = String(value || "")
+    .replace(START_CASE_REGEX, " ")
+    .trim();
+  if (!str) return "";
+  return str
+    .split(" ")
+    .filter(Boolean)
+    .map((word) => word.charAt(0).toUpperCase() + word.slice(1).toLowerCase())
+    .join(" ");
+};
+
+export const STRUCTURE_SEGMENTS = {
+  couplet: {
+    label: "Couplet",
+    promptLabel: "Couplet",
+    showIndex: true,
+    allowMultiple: true,
+    optional: false,
+    inputHeight: 225,
+    aliases: ["vers", "verse", "couplet"],
+  },
+  refrain: {
+    label: "Refrain",
+    promptLabel: "Refrain",
+    showIndex: true,
+    allowMultiple: true,
+    optional: false,
+    inputHeight: 170,
+    aliases: ["chorus", "refrain"],
+  },
+  short_intro: {
+    label: "Introduction instrumentale courte",
+    promptLabel: "Introduction instrumentale courte",
+    showIndex: false,
+    allowMultiple: false,
+    optional: true,
+    inputHeight: 150,
+    exclusiveGroup: "intro",
+    aliases: [
+      "introduction instrumentale courte",
+      "intro courte",
+      "intro instrumentale courte",
+      "short intro",
+    ],
+  },
+  long_intro: {
+    label: "Introduction instrumentale longue",
+    promptLabel: "Introduction instrumentale longue",
+    showIndex: false,
+    allowMultiple: false,
+    optional: true,
+    inputHeight: 150,
+    exclusiveGroup: "intro",
+    aliases: [
+      "introduction instrumentale longue",
+      "intro longue",
+      "long intro",
+      "intro instrumentale longue",
+    ],
+  },
+  pre_chorus: {
+    label: "Pré-refrain",
+    promptLabel: "Pré-refrain",
+    showIndex: false,
+    allowMultiple: false,
+    optional: true,
+    inputHeight: 150,
+    aliases: [
+      "pré-refrain",
+      "pre-refrain",
+      "prechorus",
+      "pre chorus",
+      "pré chorus",
+    ],
+  },
+};
+
+const ALIAS_TO_KEY = Object.entries(STRUCTURE_SEGMENTS).reduce(
+  (acc, [key, meta]) => {
+    const aliases = Array.isArray(meta.aliases) ? meta.aliases : [];
+    aliases.forEach((alias) => {
+      acc[String(alias).toLowerCase()] = key;
+    });
+    return acc;
+  },
+  {}
+);
+
+const sanitizeToken = (value) =>
+  String(value || "")
+    .trim()
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, "_")
+    .replace(/^_+|_+$/g, "");
+
+export const getSegmentMeta = (type) => {
+  const key = String(type || "").toLowerCase();
+  return STRUCTURE_SEGMENTS[key] || null;
+};
+
+export const OPTIONAL_STRUCTURE_SEGMENTS = Object.keys(
+  STRUCTURE_SEGMENTS
+).filter((key) => STRUCTURE_SEGMENTS[key]?.optional);
+
+export const normalizeStructureType = (value) => {
+  const raw = String(value || "").trim();
+  if (!raw) return "";
+  const lower = raw.toLowerCase();
+  if (STRUCTURE_SEGMENTS[lower]) return lower;
+  if (ALIAS_TO_KEY[lower]) return ALIAS_TO_KEY[lower];
+
+  const sanitized = sanitizeToken(raw);
+  if (STRUCTURE_SEGMENTS[sanitized]) return sanitized;
+  if (ALIAS_TO_KEY[sanitized]) return ALIAS_TO_KEY[sanitized];
+  return sanitized;
+};
+
+export const sanitizeStructureList = (structure = []) => {
+  if (!Array.isArray(structure)) return [];
+  const output = [];
+
+  structure.forEach((segment) => {
+    const type = normalizeStructureType(segment);
+    if (!type) return;
+    const meta = getSegmentMeta(type);
+
+    if (meta) {
+      if (meta.allowMultiple === false) {
+        const alreadyIncluded = output.some((item) => item === type);
+        if (alreadyIncluded) return;
+      }
+
+      if (meta.exclusiveGroup) {
+        const previousIndex = output.findIndex((item) => {
+          const existingMeta = getSegmentMeta(item);
+          return existingMeta?.exclusiveGroup === meta.exclusiveGroup;
+        });
+        if (previousIndex !== -1) {
+          output.splice(previousIndex, 1);
+        }
+      }
+    }
+
+    output.push(type);
+  });
+
+  return output;
+};
+
+export const formatStructureLabel = (type, occurrence = 1) => {
+  const normalized = normalizeStructureType(type);
+  const meta = getSegmentMeta(normalized);
+  const baseLabel = meta?.label || toStartCase(normalized || type);
+  const showIndex = meta?.showIndex === true;
+  if (showIndex) return `${baseLabel} ${occurrence}`;
+  if (!meta && occurrence > 1) return `${baseLabel} ${occurrence}`;
+  return baseLabel;
+};
+
+export const getStructureInputHeight = (type) => {
+  const normalized = normalizeStructureType(type);
+  const meta = getSegmentMeta(normalized);
+  return typeof meta?.inputHeight === "number" ? meta.inputHeight : undefined;
+};
+
+export const getPromptLabelForStructure = (type) => {
+  const normalized = normalizeStructureType(type);
+  const meta = getSegmentMeta(normalized);
+  if (meta?.promptLabel) return meta.promptLabel;
+  if (meta?.label) return meta.label;
+  return toStartCase(normalized || type);
+};
+
+export const isOptionalStructureType = (type) => {
+  const normalized = normalizeStructureType(type);
+  const meta = getSegmentMeta(normalized);
+  return !!meta?.optional;
+};
+
+export const arraysAreSame = (a = [], b = []) => {
+  if (a === b) return true;
+  if (!Array.isArray(a) || !Array.isArray(b)) return false;
+  if (a.length !== b.length) return false;
+  for (let i = 0; i < a.length; i += 1) {
+    if (a[i] !== b[i]) return false;
+  }
+  return true;
+};