diff --git a/client/api.ts b/client/api.ts
index fbd82de..d35a734 100644
--- a/client/api.ts
+++ b/client/api.ts
@@ -1,4 +1,4 @@
-import type { Bill, Payment, TrackerResponse } from '@/types';
+import type { Bill, Category, Payment, TrackerResponse } from '@/types';
 
 // Fetch CSRF token from the server once and cache in memory.
 // The cookie is httpOnly so document.cookie cannot access it directly.
@@ -332,10 +332,10 @@ export const api = {
   abandonSnowballPlan:   (id: Id)  => post(`/snowball/plans/${id}/abandon`, {}),
 
   // Categories
-  categories:         ()          => get('/categories'),
-  createCategory:     (data: Body) => post('/categories', data),
+  categories:         ()          => get<Category[]>('/categories'),
+  createCategory:     (data: Body) => post<Category>('/categories', data),
   reorderCategories:  (order: Body) => put('/categories/reorder', order),
-  updateCategory:     (id: Id, data: Body) => put(`/categories/${id}`, data),
+  updateCategory:     (id: Id, data: Body) => put<Category>(`/categories/${id}`, data),
   toggleCategorySpending: (id: Id, val: unknown) => patch(`/categories/${id}/spending`, { spending_enabled: val }),
   deleteCategory:     (id: Id)    => del(`/categories/${id}`),
   restoreCategory:    (id: Id)    => post(`/categories/${id}/restore`),
diff --git a/client/hooks/useQueries.ts b/client/hooks/useQueries.ts
index 31c713f..ee71991 100644
--- a/client/hooks/useQueries.ts
+++ b/client/hooks/useQueries.ts
@@ -184,8 +184,8 @@ export function useSpendingCategories() {
   return useQuery({
     queryKey: ['spending-categories'],
     queryFn: async () => {
-      const d = await api.categories() as any;
-      return (d.categories || d || []).filter((c: any) => !c.deleted_at && c.spending_enabled);
+      const cats = await api.categories();
+      return cats.filter(c => !c.deleted_at && c.spending_enabled);
     },
     staleTime: 1000 * 60 * 5,
   });
diff --git a/client/types.ts b/client/types.ts
index 8a035e4..cf8a0df 100644
--- a/client/types.ts
+++ b/client/types.ts
@@ -30,6 +30,39 @@ export interface Payment {
   [key: string]: unknown;
 }
 
+// A category's per-bill rollup (categories list endpoint). `total_paid` here is a
+// raw SQL sum (not run through fromCents), so it is deliberately NOT branded.
+export interface CategoryBillSummary {
+  id: number;
+  name: string;
+  active: boolean;
+  payment_count: number;
+  total_paid: number;
+  last_paid_date: string | null;
+  [key: string]: unknown;
+}
+
+// A spending/bill category. Has no money field of its own (budgets live on the
+// spending endpoints). The list endpoint adds bill rollups; create/update return
+// the bare row — so the rollup fields are optional.
+export interface Category {
+  id: number;
+  user_id?: number;
+  name: string;
+  sort_order?: number;
+  spending_enabled: boolean;
+  group_id: number | null;
+  created_at?: string;
+  updated_at?: string;
+  bill_count?: number;
+  active_bill_count?: number;
+  inactive_bill_count?: number;
+  payment_count?: number;
+  bill_names?: string[];
+  bills?: CategoryBillSummary[];
+  [key: string]: unknown;
+}
+
 // A bill as serialized by the server (billsService.serializeBill spreads the DB
 // row and converts the three money columns to dollars). SQLite booleans come back
 // as 0/1 integers. Extra joined columns (sparkline, has_merchant_rule, …) pass