diff --git a/web/templates/index.html b/web/templates/index.html
index 1c2dd24..b99276c 100644
--- a/web/templates/index.html
+++ b/web/templates/index.html
@@ -474,9 +474,17 @@ let TAB_CONFIG = {
     }
 };
 
-let ASSIGNED_CATEGORIES = Object.values(TAB_CONFIG)
-    .flatMap(t => t.categories)
-    .map(c => ciStr(c));
+// Categories belonging to any real tab (everything except "other").
+// "other" is defined as "whatever isn't in this set" — it must never
+// contribute to it, or its own contents would exclude themselves.
+function computeAssignedCategories() {
+    return Object.entries(TAB_CONFIG)
+        .filter(([key]) => key !== 'other')
+        .flatMap(([, t]) => t._allCategories || t.categories)
+        .map(c => ciStr(c));
+}
+
+let ASSIGNED_CATEGORIES = computeAssignedCategories();
 
 // State
 let configUUID = '{{.ConfigUUID}}';
@@ -822,19 +830,16 @@ async function loadCategoriesFromAPI() {
             categoryOrderMap[ciStr(cat.code)] = cat.display_order;
         });
 
-        // Build list of unassigned categories
-        const knownCodes = Object.values(TAB_CONFIG)
-            .flatMap(t => t.categories)
-            .map(c => ciStr(c));
+        // Build list of unassigned categories (excludes "other" itself, so
+        // this stays correct even if it's re-run after "other" was already
+        // populated by a previous call).
+        const knownCodes = computeAssignedCategories();
 
         const unassignedCategories = cats
             .filter(cat => !knownCodes.includes(ciStr(cat.code)))
             .sort((a, b) => a.display_order - b.display_order)
             .map(cat => cat.code);
 
-        // Rebuild ASSIGNED_CATEGORIES from known (non-"other") tabs before
-        // populating "other", so unassigned categories aren't immediately
-        // excluded from the "other" tab by their own assignment.
         ASSIGNED_CATEGORIES = knownCodes;
 
         // Update "other" tab with unassigned categories
@@ -886,7 +891,7 @@ function applyServerSettings(settings) {
         // before restoring .other — otherwise categories already parked in
         // .other (e.g. by loadCategoriesFromAPI) get counted as "assigned"
         // and immediately excluded from the "other" tab again.
-        ASSIGNED_CATEGORIES = Object.values(TAB_CONFIG).flatMap(t => t.categories).map(c => ciStr(c));
+        ASSIGNED_CATEGORIES = computeAssignedCategories();
         TAB_CONFIG.other = otherTab || { categories: [], singleSelect: false, label: 'Other' };
     }
 
@@ -1398,11 +1403,10 @@ function applyConfigTypeToTabs() {
         }
     });
 
-    // Rebuild assigned categories index using the full static list (_allCategories),
-    // not the filtered one — hidden categories still belong to their tab, not to Other.
-    ASSIGNED_CATEGORIES = Object.values(TAB_CONFIG)
-        .flatMap(t => t._allCategories || t.categories)
-        .map(c => ciStr(c));
+    // Rebuild assigned categories index using the full static list
+    // (_allCategories), not the filtered one — hidden categories still
+    // belong to their tab, not to Other.
+    ASSIGNED_CATEGORIES = computeAssignedCategories();
 }
 
 function updateTabVisibility() {