diff --git a/app/components/ComponentModelStructureEditor.vue b/app/components/ComponentModelStructureEditor.vue
index f69c3a0..14869e2 100644
--- a/app/components/ComponentModelStructureEditor.vue
+++ b/app/components/ComponentModelStructureEditor.vue
@@ -10,6 +10,7 @@
       :locked-type-label="displayedRootTypeLabel"
       :allow-subcomponents="allowSubcomponents"
       :max-subcomponent-depth="maxSubcomponentDepth"
+      :restricted-mode="restrictedMode"
       is-root
     />
   </div>
@@ -55,6 +56,10 @@ const props = defineProps({
     type: Number,
     default: Infinity,
   },
+  restrictedMode: {
+    type: Boolean,
+    default: false,
+  },
 })
 
 const emit = defineEmits(['update:modelValue'])
diff --git a/app/components/PieceModelStructureEditor.vue b/app/components/PieceModelStructureEditor.vue
index 599f053..27e2a82 100644
--- a/app/components/PieceModelStructureEditor.vue
+++ b/app/components/PieceModelStructureEditor.vue
@@ -7,10 +7,10 @@
             Produits inclus par défaut
           </h3>
           <p class="text-xs text-base-content/70">
-            Ces produits s’afficheront lors de la création d’une pièce basée sur cette catégorie.
+            Ces produits s'afficheront lors de la création d'une pièce basée sur cette catégorie.
           </p>
         </div>
-        <button type="button" class="btn btn-outline btn-xs" @click="addProduct">
+        <button v-if="!restrictedMode" type="button" class="btn btn-outline btn-xs" @click="addProduct">
           <IconLucidePlus class="w-3 h-3 mr-2" aria-hidden="true" />
           Ajouter
         </button>
@@ -35,6 +35,7 @@
                 <select
                   v-model="product.typeProductId"
                   class="select select-bordered select-xs"
+                  :disabled="isProductLocked(product)"
                   @change="handleProductTypeSelect(product)"
                 >
                   <option value="">
@@ -51,12 +52,22 @@
               </div>
             </div>
             <button
+              v-if="!isProductLocked(product)"
               type="button"
               class="btn btn-error btn-xs btn-square"
               @click="removeProduct(index)"
             >
               <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
             </button>
+            <div v-else class="tooltip tooltip-left" data-tip="Ce produit ne peut pas être supprimé car des éléments utilisent cette catégorie">
+              <button
+                type="button"
+                class="btn btn-ghost btn-xs btn-square opacity-30 cursor-not-allowed"
+                disabled
+              >
+                <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
+              </button>
+            </div>
           </div>
         </li>
       </ul>
@@ -107,8 +118,9 @@
                 type="text"
                 class="input input-bordered input-xs"
                 placeholder="Nom du champ"
+                :disabled="isFieldLocked(field)"
               >
-              <select v-model="field.type" class="select select-bordered select-xs">
+              <select v-model="field.type" class="select select-bordered select-xs" :disabled="isFieldLocked(field)">
                 <option value="text">
                   Texte
                 </option>
@@ -128,7 +140,7 @@
             </div>
 
             <div class="flex items-center gap-2 text-xs">
-              <input v-model="field.required" type="checkbox" class="checkbox checkbox-xs">
+              <input v-model="field.required" type="checkbox" class="checkbox checkbox-xs" :disabled="isFieldLocked(field)">
               Obligatoire
             </div>
 
@@ -137,16 +149,27 @@
               v-model="field.optionsText"
               class="textarea textarea-bordered textarea-xs h-20"
               placeholder="Option 1&#10;Option 2"
+              :disabled="isFieldLocked(field)"
             />
           </div>
 
           <button
+            v-if="!isFieldLocked(field)"
             type="button"
             class="btn btn-error btn-xs btn-square"
             @click="removeField(index)"
           >
             <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
           </button>
+          <div v-else class="tooltip tooltip-left" data-tip="Ce champ ne peut pas être supprimé car des éléments utilisent cette catégorie">
+            <button
+              type="button"
+              class="btn btn-ghost btn-xs btn-square opacity-30 cursor-not-allowed"
+              disabled
+            >
+              <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
+            </button>
+          </div>
         </div>
       </li>
     </ul>
@@ -181,6 +204,7 @@ type EditorProduct = {
 
 const props = defineProps<{
   modelValue?: PieceModelStructure | null
+  restrictedMode?: boolean
 }>()
 
 const emit = defineEmits<{
@@ -330,6 +354,19 @@ const fields = ref<EditorField[]>(hydrateFields(props.modelValue))
 const products = ref<EditorProduct[]>(hydrateProducts(props.modelValue))
 const restState = ref<Record<string, unknown>>(extractRest(props.modelValue))
 
+const initialFieldUids = ref<Set<string>>(new Set(fields.value.map(f => f.uid)))
+const initialProductUids = ref<Set<string>>(new Set(products.value.map(p => p.uid)))
+
+const isFieldLocked = (field: EditorField): boolean => {
+  return props.restrictedMode === true && initialFieldUids.value.has(field.uid)
+}
+
+const isProductLocked = (product: EditorProduct): boolean => {
+  return props.restrictedMode === true && initialProductUids.value.has(product.uid)
+}
+
+const restrictedMode = computed(() => props.restrictedMode === true)
+
 const applyOrderIndex = (list: EditorField[]): EditorField[] =>
   list.map((field, index) => ({
     ...field,
@@ -438,6 +475,8 @@ watch(
     products.value = hydrateProducts(value)
     products.value.forEach((product) => updateProductTypeMetadata(product))
     lastEmitted = incomingSerialized
+    initialFieldUids.value = new Set(fields.value.map(f => f.uid))
+    initialProductUids.value = new Set(products.value.map(p => p.uid))
   },
   { deep: true },
 )
diff --git a/app/components/StructureNodeEditor.vue b/app/components/StructureNodeEditor.vue
index f520923..bce8a43 100644
--- a/app/components/StructureNodeEditor.vue
+++ b/app/components/StructureNodeEditor.vue
@@ -17,6 +17,7 @@
             <select
               v-model="node.typeComposantId"
               class="select select-bordered select-sm w-full"
+              :disabled="isLocked"
               @change="handleComponentTypeSelect(node)"
             >
               <option value="">
@@ -42,6 +43,7 @@
                 type="text"
                 class="input input-bordered input-xs"
                 placeholder="Alias du sous-composant"
+                :disabled="isLocked"
               />
             </div>
           </template>
@@ -52,13 +54,18 @@
           </template>
         </div>
         <button
-          v-if="!isRoot"
+          v-if="!isRoot && !isLocked"
           type="button"
           class="btn btn-error btn-xs btn-square"
           @click="emit('remove')"
         >
           <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
         </button>
+        <div v-else-if="!isRoot && isLocked" class="tooltip tooltip-left" data-tip="Ce sous-composant ne peut pas être supprimé">
+          <button type="button" class="btn btn-ghost btn-xs btn-square opacity-30 cursor-not-allowed" disabled>
+            <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
+          </button>
+        </div>
       </div>
 
       <div class="px-4 py-4 space-y-5">
@@ -107,8 +114,9 @@
                       type="text"
                       class="input input-bordered input-xs"
                       placeholder="Nom du champ"
+                      :disabled="isCustomFieldLocked(index)"
                     />
-                    <select v-model="field.type" class="select select-bordered select-xs">
+                    <select v-model="field.type" class="select select-bordered select-xs" :disabled="isCustomFieldLocked(index)">
                       <option value="text">Texte</option>
                       <option value="number">Nombre</option>
                       <option value="select">Liste</option>
@@ -117,7 +125,7 @@
                     </select>
                   </div>
                   <div class="flex items-center gap-2 text-xs">
-                    <input v-model="field.required" type="checkbox" class="checkbox checkbox-xs" />
+                    <input v-model="field.required" type="checkbox" class="checkbox checkbox-xs" :disabled="isCustomFieldLocked(index)" />
                     Obligatoire
                   </div>
                   <textarea
@@ -125,15 +133,26 @@
                     v-model="field.optionsText"
                     class="textarea textarea-bordered textarea-xs h-20"
                     placeholder="Option 1&#10;Option 2"
+                    :disabled="isCustomFieldLocked(index)"
                   ></textarea>
                 </div>
                 <button
+                  v-if="!isCustomFieldLocked(index)"
                   type="button"
                   class="btn btn-error btn-xs btn-square"
                   @click="removeCustomField(index)"
                 >
                   <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
                 </button>
+                <div v-else class="tooltip tooltip-left" data-tip="Ce champ ne peut pas être supprimé car des éléments utilisent cette catégorie">
+                  <button
+                    type="button"
+                    class="btn btn-ghost btn-xs btn-square opacity-30 cursor-not-allowed"
+                    disabled
+                  >
+                    <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
+                  </button>
+                </div>
               </div>
             </div>
           </div>
@@ -144,7 +163,7 @@
             <h4 :class="headingClass">
               {{ isRoot ? 'Produits inclus par défaut' : 'Produits' }}
             </h4>
-            <button type="button" class="btn btn-outline btn-xs" @click="addProduct">
+            <button v-if="!restrictedMode" type="button" class="btn btn-outline btn-xs" @click="addProduct">
               <IconLucidePlus class="w-3 h-3 mr-2" aria-hidden="true" />
               Ajouter
             </button>
@@ -179,6 +198,7 @@
                     <select
                       v-model="product.typeProductId"
                       class="select select-bordered select-xs"
+                      :disabled="isProductLocked(index)"
                       @change="handleProductTypeSelect(product)"
                     >
                       <option value="">
@@ -194,9 +214,18 @@
                     </select>
                   </div>
                 </div>
-                <button type="button" class="btn btn-error btn-xs btn-square" @click="removeProduct(index)">
+                <button v-if="!isProductLocked(index)" type="button" class="btn btn-error btn-xs btn-square" @click="removeProduct(index)">
                   <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
                 </button>
+                <div v-else class="tooltip tooltip-left" data-tip="Ce produit ne peut pas être supprimé car des éléments utilisent cette catégorie">
+                  <button
+                    type="button"
+                    class="btn btn-ghost btn-xs btn-square opacity-30 cursor-not-allowed"
+                    disabled
+                  >
+                    <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
+                  </button>
+                </div>
               </div>
             </div>
           </div>
@@ -207,7 +236,7 @@
             <h4 :class="headingClass">
               {{ isRoot ? 'Pièces incluses par défaut' : 'Pièces' }}
             </h4>
-            <button type="button" class="btn btn-outline btn-xs" @click="addPiece">
+            <button v-if="!restrictedMode" type="button" class="btn btn-outline btn-xs" @click="addPiece">
               <IconLucidePlus class="w-3 h-3 mr-2" aria-hidden="true" />
               Ajouter
             </button>
@@ -243,6 +272,7 @@
                       <select
                         v-model="piece.typePieceId"
                         class="select select-bordered select-xs"
+                        :disabled="isPieceLocked(index)"
                         @change="handlePieceTypeSelect(piece)"
                       >
                         <option value="">
@@ -262,9 +292,14 @@
                     </p>
                   </div>
                 </div>
-                <button type="button" class="btn btn-error btn-xs btn-square" @click="removePiece(index)">
+                <button v-if="!isPieceLocked(index)" type="button" class="btn btn-error btn-xs btn-square" @click="removePiece(index)">
                   <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
                 </button>
+                <div v-else class="tooltip tooltip-left" data-tip="Cette pièce ne peut pas être supprimée">
+                  <button type="button" class="btn btn-ghost btn-xs btn-square opacity-30 cursor-not-allowed" disabled>
+                    <IconLucideTrash class="w-4 h-4" aria-hidden="true" />
+                  </button>
+                </div>
               </div>
             </div>
           </div>
@@ -274,7 +309,7 @@
           <div class="flex items-center justify-between gap-2">
             <h4 :class="headingClass">Sous-composants</h4>
             <button
-              v-if="canManageSubcomponents"
+              v-if="canManageSubcomponents && !restrictedMode"
               type="button"
               class="btn btn-outline btn-xs"
               @click="addSubComponent"
@@ -317,6 +352,8 @@
                 :product-types="productTypes"
                 :allow-subcomponents="childAllowSubcomponents"
                 :max-subcomponent-depth="maxSubcomponentDepth"
+                :restricted-mode="restrictedMode"
+                :is-locked="isSubcomponentLocked(index)"
                 @remove="removeSubComponent(index)"
               />
             </div>
@@ -359,6 +396,8 @@ const props = withDefaults(defineProps<{
   lockedTypeLabel?: string
   allowSubcomponents?: boolean
   maxSubcomponentDepth?: number
+  restrictedMode?: boolean
+  isLocked?: boolean
 }>(), {
   depth: 0,
   componentTypes: () => [],
@@ -369,10 +408,52 @@ const props = withDefaults(defineProps<{
   lockedTypeLabel: '',
   allowSubcomponents: true,
   maxSubcomponentDepth: Infinity,
+  restrictedMode: false,
+  isLocked: false,
 })
 
 const emit = defineEmits(['remove'])
 
+const initialCustomFieldIndices = ref<Set<number>>(new Set())
+const initialPieceIndices = ref<Set<number>>(new Set())
+const initialProductIndices = ref<Set<number>>(new Set())
+const initialSubcomponentIndices = ref<Set<number>>(new Set())
+
+const initializeLockedIndices = () => {
+  if (props.restrictedMode) {
+    const customFieldsLength = Array.isArray(props.node.customFields) ? props.node.customFields.length : 0
+    const piecesLength = Array.isArray(props.node.pieces) ? props.node.pieces.length : 0
+    const productsLength = Array.isArray(props.node.products) ? props.node.products.length : 0
+    const subcomponentsLength = Array.isArray(props.node.subcomponents) ? props.node.subcomponents.length : 0
+
+    initialCustomFieldIndices.value = new Set(Array.from({ length: customFieldsLength }, (_, i) => i))
+    initialPieceIndices.value = new Set(Array.from({ length: piecesLength }, (_, i) => i))
+    initialProductIndices.value = new Set(Array.from({ length: productsLength }, (_, i) => i))
+    initialSubcomponentIndices.value = new Set(Array.from({ length: subcomponentsLength }, (_, i) => i))
+  }
+}
+
+initializeLockedIndices()
+
+const isCustomFieldLocked = (index: number): boolean => {
+  return props.restrictedMode === true && initialCustomFieldIndices.value.has(index)
+}
+
+const isPieceLocked = (index: number): boolean => {
+  return props.restrictedMode === true && initialPieceIndices.value.has(index)
+}
+
+const isProductLocked = (index: number): boolean => {
+  return props.restrictedMode === true && initialProductIndices.value.has(index)
+}
+
+const isSubcomponentLocked = (index: number): boolean => {
+  return props.restrictedMode === true && initialSubcomponentIndices.value.has(index)
+}
+
+const isLocked = computed(() => props.isLocked === true)
+const restrictedMode = computed(() => props.restrictedMode === true)
+
 const componentTypes = computed(() => props.componentTypes ?? [])
 const pieceTypes = computed(() => props.pieceTypes ?? [])
 const productTypes = computed(() => props.productTypes ?? [])
diff --git a/app/components/model-types/ModelTypeForm.vue b/app/components/model-types/ModelTypeForm.vue
index 84cb4b4..b4ca544 100644
--- a/app/components/model-types/ModelTypeForm.vue
+++ b/app/components/model-types/ModelTypeForm.vue
@@ -15,6 +15,7 @@
           minlength="2"
           maxlength="120"
           required
+          :disabled="restrictedMode"
         />
         <p v-if="errors.name" class="mt-1 text-sm text-error">{{ errors.name }}</p>
       </div>
@@ -47,6 +48,7 @@
           rows="4"
           name="notes"
           maxlength="2000"
+          :disabled="restrictedMode"
         ></textarea>
         <p class="mt-1 text-xs text-base-content/70">Saisissez des informations complémentaires (facultatif).</p>
       </div>
@@ -81,6 +83,7 @@
             v-model="componentStructure"
             :allow-subcomponents="allowComponentSubcomponents"
             :max-subcomponent-depth="componentSubcomponentMaxDepth"
+            :restricted-mode="restrictedMode"
           />
         </div>
 
@@ -92,7 +95,7 @@
             Aperçu :
             <span class="font-medium text-base-content">{{ pieceStructurePreview }}</span>
           </p>
-          <PieceModelStructureEditor v-model="pieceStructure" />
+          <PieceModelStructureEditor v-model="pieceStructure" :restricted-mode="restrictedMode" />
         </div>
 
         <div
@@ -103,11 +106,21 @@
             Aperçu :
             <span class="font-medium text-base-content">{{ productStructurePreview }}</span>
           </p>
-          <PieceModelStructureEditor v-model="productStructure" />
+          <PieceModelStructureEditor v-model="productStructure" :restricted-mode="restrictedMode" />
         </div>
       </template>
     </section>
 
+    <div
+      v-if="restrictedMode && restrictedModeMessage"
+      class="alert alert-info"
+      role="status"
+      aria-live="polite"
+    >
+      <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" class="stroke-current shrink-0 w-6 h-6"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"></path></svg>
+      <span>{{ restrictedModeMessage }}</span>
+    </div>
+
     <div
       v-if="disableSubmit"
       class="alert alert-warning"
@@ -161,6 +174,8 @@ const props = withDefaults(defineProps<{
   componentSubcomponentMaxDepth?: number
   disableSubmit?: boolean
   disableSubmitMessage?: string
+  restrictedMode?: boolean
+  restrictedModeMessage?: string
 }>(), {
   initialData: null,
   saving: false,
@@ -170,6 +185,8 @@ const props = withDefaults(defineProps<{
   componentSubcomponentMaxDepth: 1,
   disableSubmit: false,
   disableSubmitMessage: '',
+  restrictedMode: false,
+  restrictedModeMessage: '',
 })
 
 const emit = defineEmits<{
@@ -192,6 +209,12 @@ const disableSubmitMessage = computed(() =>
     ? props.disableSubmitMessage
     : 'Cette catégorie ne peut pas être modifiée car des éléments y sont déjà liés.',
 )
+const restrictedMode = computed(() => props.restrictedMode === true)
+const restrictedModeMessage = computed(() =>
+  (props.restrictedModeMessage && props.restrictedModeMessage.trim())
+    ? props.restrictedModeMessage
+    : '',
+)
 
 const form = reactive<ModelTypePayload>({
   name: '',
diff --git a/app/composables/useCategoryEditGuard.ts b/app/composables/useCategoryEditGuard.ts
index 2cfbf1e..74cb23d 100644
--- a/app/composables/useCategoryEditGuard.ts
+++ b/app/composables/useCategoryEditGuard.ts
@@ -32,7 +32,7 @@ const extractTotal = (payload: any, fallbackLength: number) => {
 
 export function useCategoryEditGuard (config: GuardConfig) {
   const { get } = useApi()
-  const { showError } = useToast()
+  const { showInfo } = useToast()
 
   const linkedCount = ref(0)
   const linkedLoading = ref(false)
@@ -64,11 +64,15 @@ export function useCategoryEditGuard (config: GuardConfig) {
     }
   }
 
-  const isSubmitBlocked = computed(
-    () => linkedLoading.value || linkedCount.value > 0,
+  const isRestrictedMode = computed(
+    () => !linkedLoading.value && linkedCount.value > 0,
   )
 
-  const submitBlockMessage = computed(() => {
+  const isSubmitBlocked = computed(
+    () => linkedLoading.value,
+  )
+
+  const restrictedModeMessage = computed(() => {
     if (linkedLoading.value) {
       return config.labels.verifying
     }
@@ -76,23 +80,32 @@ export function useCategoryEditGuard (config: GuardConfig) {
       return ''
     }
     if (linkedCount.value === 1) {
-      return `Modification bloquée : 1 ${config.labels.singular} est déjà lié à cette catégorie.`
+      return `Mode restreint : 1 ${config.labels.singular} est déjà lié à cette catégorie. Vous pouvez ajouter de nouveaux champs personnalisés, mais pas modifier ou supprimer les existants.`
     }
-    return `Modification bloquée : ${linkedCount.value} ${config.labels.plural} sont déjà liés à cette catégorie.`
+    return `Mode restreint : ${linkedCount.value} ${config.labels.plural} sont déjà liés à cette catégorie. Vous pouvez ajouter de nouveaux champs personnalisés, mais pas modifier ou supprimer les existants.`
+  })
+
+  const submitBlockMessage = computed(() => {
+    if (linkedLoading.value) {
+      return config.labels.verifying
+    }
+    return ''
   })
 
   const guardSubmitOrNotify = () => {
     if (!isSubmitBlocked.value) {
       return false
     }
-    showError(submitBlockMessage.value || 'Modification bloquée pour cette catégorie.')
+    showInfo(submitBlockMessage.value || 'Veuillez patienter...')
     return true
   }
 
   return {
     linkedCount,
     linkedLoading,
+    isRestrictedMode,
     isSubmitBlocked,
+    restrictedModeMessage,
     submitBlockMessage,
     loadLinkedCount,
     guardSubmitOrNotify,
diff --git a/app/pages/component-category/[id]/edit.vue b/app/pages/component-category/[id]/edit.vue
index 567390b..4e0f5af 100644
--- a/app/pages/component-category/[id]/edit.vue
+++ b/app/pages/component-category/[id]/edit.vue
@@ -28,6 +28,8 @@
         :saving="saving"
         :disable-submit="isSubmitBlocked"
         :disable-submit-message="submitBlockMessage"
+        :restricted-mode="isRestrictedMode"
+        :restricted-mode-message="restrictedModeMessage"
         @submit="handleSubmit"
         @cancel="handleCancel"
       />
@@ -52,7 +54,9 @@ const saving = ref(false)
 const initialData = ref<Partial<ModelTypePayload> | null>(null)
 
 const {
+  isRestrictedMode,
   isSubmitBlocked,
+  restrictedModeMessage,
   submitBlockMessage,
   loadLinkedCount,
   guardSubmitOrNotify,
diff --git a/app/pages/piece-category/[id]/edit.vue b/app/pages/piece-category/[id]/edit.vue
index f816c8d..7b17bbc 100644
--- a/app/pages/piece-category/[id]/edit.vue
+++ b/app/pages/piece-category/[id]/edit.vue
@@ -28,6 +28,8 @@
         :saving="saving"
         :disable-submit="isSubmitBlocked"
         :disable-submit-message="submitBlockMessage"
+        :restricted-mode="isRestrictedMode"
+        :restricted-mode-message="restrictedModeMessage"
         @submit="handleSubmit"
         @cancel="handleCancel"
       />
@@ -52,7 +54,9 @@ const saving = ref(false)
 const initialData = ref<Partial<ModelTypePayload> | null>(null)
 
 const {
+  isRestrictedMode,
   isSubmitBlocked,
+  restrictedModeMessage,
   submitBlockMessage,
   loadLinkedCount,
   guardSubmitOrNotify,
diff --git a/app/pages/product-category/[id]/edit.vue b/app/pages/product-category/[id]/edit.vue
index 3707006..687d16d 100644
--- a/app/pages/product-category/[id]/edit.vue
+++ b/app/pages/product-category/[id]/edit.vue
@@ -28,6 +28,8 @@
         :saving="saving"
         :disable-submit="isSubmitBlocked"
         :disable-submit-message="submitBlockMessage"
+        :restricted-mode="isRestrictedMode"
+        :restricted-mode-message="restrictedModeMessage"
         @submit="handleSubmit"
         @cancel="handleCancel"
       />
@@ -52,7 +54,9 @@ const saving = ref(false)
 const initialData = ref<Partial<ModelTypePayload> | null>(null)
 
 const {
+  isRestrictedMode,
   isSubmitBlocked,
+  restrictedModeMessage,
   submitBlockMessage,
   loadLinkedCount,
   guardSubmitOrNotify,