diff --git a/app_new/interventions/templates/detail.html b/app_new/interventions/templates/detail.html
index 85dc684..e640590 100644
--- a/app_new/interventions/templates/detail.html
+++ b/app_new/interventions/templates/detail.html
@@ -596,6 +596,26 @@
   const category = document.getElementById('intervention-category');
   const equipment = document.getElementById('intervention-equipment');
   if (!room || !category || !equipment) return;
+  const equipmentOptions = [...equipment.options].filter(option => option.value);
+  const filterCategories = () => {
+    const roomId = room.value;
+    const presentCategories = new Set(
+      equipmentOptions
+        .filter(option => roomId && option.dataset.room === roomId)
+        .map(option => option.dataset.category)
+        .filter(Boolean)
+    );
+    [...category.options].forEach(option => {
+      if (!option.value) {
+        option.hidden = false;
+        option.textContent = roomId ? '— Choisir un type présent —' : '— Sélectionnez d’abord une salle —';
+        return;
+      }
+      option.hidden = !roomId || !presentCategories.has(option.value);
+      if (option.hidden && option.selected) category.value = '';
+    });
+    category.disabled = !roomId || presentCategories.size === 0;
+  };
   const filter = () => {
     const roomId = room.value;
     const categoryId = category.value;
@@ -607,8 +627,9 @@
       if (option.hidden && option.selected) equipment.value = '';
     });
   };
-  room.addEventListener('change', filter);
+  room.addEventListener('change', () => { filterCategories(); filter(); });
   category.addEventListener('change', filter);
+  filterCategories();
   filter();
 })();
 </script>