diff --git a/backlog/tasks/task-13 - Improve-transaction-category-picker.md b/backlog/tasks/task-13 - Improve-transaction-category-picker.md
new file mode 100644
index 0000000..5eac260
--- /dev/null
+++ b/backlog/tasks/task-13 - Improve-transaction-category-picker.md	
@@ -0,0 +1,53 @@
+---
+id: TASK-13
+title: Improve transaction category picker
+status: Done
+assignee: []
+created_date: '2026-06-16 10:08'
+updated_date: '2026-06-23 09:45'
+labels: []
+dependencies: []
+priority: high
+ordinal: 13000
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Replace the cramped inline category Select in the transactions table with a polished popover picker that preserves row height, supports search, and groups categories.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [x] #1 Clicking a transaction category badge opens a compact popover instead of the current narrow Select.
+- [x] #2 The picker supports client-side category search and groups income, fixed expense, and variable expense categories.
+- [x] #3 Long category names are truncated cleanly without increasing table row height.
+- [x] #4 Selecting a category updates the transaction, closes the popover, and reports failures with a toast.
+- [x] #5 The project builds successfully.
+<!-- AC:END -->
+
+## Implementation Plan
+
+<!-- SECTION:PLAN:BEGIN -->
+1. Extract category grouping/search helpers and cover them with tests
+2. Replace inline category Select with a stable Popover picker
+3. Wire async update handling and failure toast
+4. Verify build and relevant tests
+<!-- SECTION:PLAN:END -->
+
+## Implementation Notes
+
+<!-- SECTION:NOTES:BEGIN -->
+Implemented CategoryPicker popover with search, grouped category options, selected-state checkmark, truncation, and async update error toast.
+Verification: categoryPickerModel test passes; npm run build passes.
+Lint: changed files pass with one existing TanStack React Compiler warning in TransactionsPage; full npm run lint still fails on pre-existing unrelated project errors.
+Manual browser verification is still open because the in-app browser redirects to /login without the user session.
+
+Final verification: npx vitest run src/components/transactions/categoryPickerModel.test.ts passed (2 tests); npm run build passed; targeted eslint on changed files exited 0 with the existing TanStack useReactTable compiler warning only.
+<!-- SECTION:NOTES:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+Shipped a reusable inline CategoryPicker popover for transaction category changes, with grouped searchable categories, truncation for long labels, async update handling, and a regression test for grouping/search behavior.
+<!-- SECTION:FINAL_SUMMARY:END -->
diff --git a/src/components/transactions/CategoryPicker.tsx b/src/components/transactions/CategoryPicker.tsx
new file mode 100644
index 0000000..f0ff37e
--- /dev/null
+++ b/src/components/transactions/CategoryPicker.tsx
@@ -0,0 +1,154 @@
+import { useMemo, useRef, useState } from "react";
+import * as Popover from "@radix-ui/react-popover";
+import { Check, ChevronDown, Search } from "lucide-react";
+import type { Doc, Id } from "../../../convex/_generated/dataModel";
+import { Badge } from "@/components/ui/badge";
+import { Input } from "@/components/ui/input";
+import { cn } from "@/lib/utils";
+import { groupCategoryOptions, searchCategoryOptions } from "./categoryPickerModel";
+import { toast } from "sonner";
+
+type Category = Doc<"categories">;
+
+export function CategoryPicker({
+  categories,
+  value,
+  onSelect,
+}: {
+  categories: Category[] | undefined;
+  value: Id<"categories"> | undefined;
+  onSelect: (categoryId: Id<"categories">) => Promise<void>;
+}) {
+  const [open, setOpen] = useState(false);
+  const [query, setQuery] = useState("");
+  const [pendingId, setPendingId] = useState<Id<"categories"> | null>(null);
+  const searchRef = useRef<HTMLInputElement>(null);
+
+  const selectedCategory = useMemo(
+    () => categories?.find((category) => category._id === value),
+    [categories, value],
+  );
+  const groupedCategories = useMemo(
+    () => groupCategoryOptions(searchCategoryOptions(categories ?? [], query)),
+    [categories, query],
+  );
+
+  const handleSelect = async (categoryId: Id<"categories">) => {
+    if (categoryId === value) {
+      setOpen(false);
+      return;
+    }
+
+    setPendingId(categoryId);
+    try {
+      await onSelect(categoryId);
+      setOpen(false);
+    } catch (error) {
+      toast.error(error instanceof Error ? error.message : "Kategorie konnte nicht gespeichert werden");
+    } finally {
+      setPendingId(null);
+    }
+  };
+
+  return (
+    <Popover.Root
+      open={open}
+      onOpenChange={(nextOpen) => {
+        setOpen(nextOpen);
+        if (!nextOpen) setQuery("");
+      }}
+    >
+      <Popover.Trigger asChild>
+        <button
+          type="button"
+          className="group inline-flex h-7 max-w-[180px] items-center gap-1 rounded px-1 text-left text-xs transition-colors hover:bg-accent focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring"
+          aria-label={
+            selectedCategory
+              ? `Kategorie ändern: ${selectedCategory.name}`
+              : "Kategorie auswählen"
+          }
+        >
+          {selectedCategory ? (
+            <Badge
+              className="max-w-[155px] whitespace-nowrap border-none px-2 py-0.5 text-[11px] leading-4 shadow-none"
+              style={{ backgroundColor: selectedCategory.color, color: "#fff" }}
+            >
+              <span className="min-w-0 truncate">{selectedCategory.name}</span>
+            </Badge>
+          ) : (
+            <span className="max-w-[145px] truncate text-muted-foreground">Kategorie...</span>
+          )}
+          <ChevronDown className="h-3.5 w-3.5 shrink-0 text-muted-foreground opacity-0 transition-opacity group-hover:opacity-70 group-focus-visible:opacity-70 group-data-[state=open]:opacity-70" />
+        </button>
+      </Popover.Trigger>
+      <Popover.Portal>
+        <Popover.Content
+          align="start"
+          sideOffset={6}
+          className="z-50 w-[min(320px,calc(100vw-2rem))] rounded-md border bg-popover p-2 text-popover-foreground shadow-lg"
+          onOpenAutoFocus={(event) => {
+            event.preventDefault();
+            searchRef.current?.focus();
+          }}
+        >
+          <div className="relative mb-2">
+            <Search className="pointer-events-none absolute left-2.5 top-1/2 h-4 w-4 -translate-y-1/2 text-muted-foreground" />
+            <Input
+              ref={searchRef}
+              value={query}
+              onChange={(event) => setQuery(event.target.value)}
+              placeholder="Kategorie suchen..."
+              className="h-8 pl-8 text-sm"
+            />
+          </div>
+
+          <div className="max-h-80 overflow-y-auto pr-1">
+            {groupedCategories.length === 0 ? (
+              <div className="px-2 py-6 text-center text-sm text-muted-foreground">
+                Keine Kategorie gefunden
+              </div>
+            ) : (
+              groupedCategories.map((group) => (
+                <div key={group.key} className="pb-1 last:pb-0">
+                  <div className="px-2 py-1 text-[11px] font-semibold uppercase tracking-wide text-muted-foreground">
+                    {group.label}
+                  </div>
+                  <div className="space-y-0.5">
+                    {group.options.map((category) => {
+                      const selected = category._id === value;
+                      const pending = category._id === pendingId;
+
+                      return (
+                        <button
+                          key={category._id}
+                          type="button"
+                          disabled={pendingId !== null}
+                          onClick={() => void handleSelect(category._id)}
+                          className={cn(
+                            "flex h-8 w-full items-center gap-2 rounded-sm px-2 text-left text-sm transition-colors hover:bg-accent focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring disabled:pointer-events-none disabled:opacity-60",
+                            selected && "bg-accent/70",
+                          )}
+                        >
+                          <span
+                            className="h-2.5 w-2.5 shrink-0 rounded-full"
+                            style={{ backgroundColor: category.color }}
+                          />
+                          <span className="min-w-0 flex-1 truncate">{category.name}</span>
+                          {pending ? (
+                            <span className="text-xs text-muted-foreground">Speichert</span>
+                          ) : (
+                            selected && <Check className="h-4 w-4 shrink-0" />
+                          )}
+                        </button>
+                      );
+                    })}
+                  </div>
+                </div>
+              ))
+            )}
+          </div>
+        </Popover.Content>
+      </Popover.Portal>
+    </Popover.Root>
+  );
+}
diff --git a/src/components/transactions/categoryPickerModel.test.ts b/src/components/transactions/categoryPickerModel.test.ts
new file mode 100644
index 0000000..b436666
--- /dev/null
+++ b/src/components/transactions/categoryPickerModel.test.ts
@@ -0,0 +1,71 @@
+import { describe, expect, it } from "vitest";
+import { groupCategoryOptions, searchCategoryOptions } from "./categoryPickerModel";
+
+const categories = [
+  {
+    _id: "income-1",
+    name: "Gehalt & Besoldung",
+    kind: "einnahme",
+    color: "#22c55e",
+    sortOrder: 1,
+  },
+  {
+    _id: "fixed-1",
+    name: "Miete & Wohnen",
+    kind: "ausgabe",
+    block: "wiederkehrend",
+    color: "#6366f1",
+    sortOrder: 10,
+  },
+  {
+    _id: "variable-1",
+    name: "Restaurant, Lieferdienst & Gastro",
+    kind: "ausgabe",
+    block: "variabel",
+    color: "#dc2626",
+    sortOrder: 37,
+  },
+  {
+    _id: "fallback-1",
+    name: "Nicht zugeordnetes Einkommen",
+    kind: "einnahme",
+    color: "#6ee7b7",
+    sortOrder: 99,
+  },
+] as const;
+
+describe("categoryPickerModel", () => {
+  it("groups category options by income, fixed expenses, and variable expenses", () => {
+    const groups = groupCategoryOptions(categories);
+
+    expect(groups).toEqual([
+      {
+        key: "income",
+        label: "Einnahmen",
+        options: [categories[0], categories[3]],
+      },
+      {
+        key: "fixed-expenses",
+        label: "Fixe Ausgaben",
+        options: [categories[1]],
+      },
+      {
+        key: "variable-expenses",
+        label: "Variable Ausgaben",
+        options: [categories[2]],
+      },
+    ]);
+  });
+
+  it("filters category options by name before grouping them", () => {
+    const filtered = searchCategoryOptions(categories, "liefer");
+
+    expect(groupCategoryOptions(filtered)).toEqual([
+      {
+        key: "variable-expenses",
+        label: "Variable Ausgaben",
+        options: [categories[2]],
+      },
+    ]);
+  });
+});
diff --git a/src/components/transactions/categoryPickerModel.ts b/src/components/transactions/categoryPickerModel.ts
new file mode 100644
index 0000000..c2a68c7
--- /dev/null
+++ b/src/components/transactions/categoryPickerModel.ts
@@ -0,0 +1,56 @@
+export type CategoryPickerOption = {
+  _id: string;
+  name: string;
+  kind: "einnahme" | "ausgabe";
+  block?: "wiederkehrend" | "variabel";
+  color: string;
+  sortOrder: number;
+};
+
+export type CategoryPickerGroup<T extends CategoryPickerOption = CategoryPickerOption> = {
+  key: "income" | "fixed-expenses" | "variable-expenses";
+  label: string;
+  options: T[];
+};
+
+const GROUPS: Array<Pick<CategoryPickerGroup, "key" | "label">> = [
+  { key: "income", label: "Einnahmen" },
+  { key: "fixed-expenses", label: "Fixe Ausgaben" },
+  { key: "variable-expenses", label: "Variable Ausgaben" },
+];
+
+export function searchCategoryOptions<T extends CategoryPickerOption>(
+  categories: readonly T[],
+  query: string,
+): T[] {
+  const normalizedQuery = query.trim().toLocaleLowerCase("de-DE");
+
+  if (!normalizedQuery) return [...categories];
+
+  return categories.filter((category) =>
+    category.name.toLocaleLowerCase("de-DE").includes(normalizedQuery),
+  );
+}
+
+export function groupCategoryOptions<T extends CategoryPickerOption>(
+  categories: readonly T[],
+): Array<CategoryPickerGroup<T>> {
+  const groups = new Map<CategoryPickerGroup["key"], T[]>(
+    GROUPS.map((group) => [group.key, []]),
+  );
+
+  for (const category of categories) {
+    groups.get(getCategoryGroupKey(category))?.push(category);
+  }
+
+  return GROUPS.map((group) => ({
+    ...group,
+    options: groups.get(group.key) ?? [],
+  })).filter((group) => group.options.length > 0);
+}
+
+function getCategoryGroupKey(category: CategoryPickerOption): CategoryPickerGroup["key"] {
+  if (category.kind === "einnahme") return "income";
+  if (category.block === "wiederkehrend") return "fixed-expenses";
+  return "variable-expenses";
+}
diff --git a/src/pages/TransactionsPage.tsx b/src/pages/TransactionsPage.tsx
index b2a5c9b..c7de79d 100644
--- a/src/pages/TransactionsPage.tsx
+++ b/src/pages/TransactionsPage.tsx
@@ -28,6 +28,7 @@ import { Badge } from "@/components/ui/badge";
 import { amountClass, formatAmount, formatDate, formatMonth } from "@/lib/format";
 import { TransactionFormDialog } from "@/components/transactions/TransactionFormDialog";
 import { AssignMonthDialog } from "@/components/transactions/AssignMonthDialog";
+import { CategoryPicker } from "@/components/transactions/CategoryPicker";
 import { toast } from "sonner";
 import {
   getVisibleSelectionState,
@@ -82,64 +83,18 @@ const AccountCell = memo(function AccountCell({ name }: { name: string | undefin
 const CategoryCell = memo(function CategoryCell({
   tx,
   categories,
-  categoryMap,
   onUpdate,
 }: {
   tx: Tx;
   categories: Category[] | undefined;
-  categoryMap: Map<Id<"categories">, Category>;
-  onUpdate: (id: Id<"transactions">, categoryId: Id<"categories">) => void;
+  onUpdate: (id: Id<"transactions">, categoryId: Id<"categories">) => Promise<void>;
 }) {
-  const [open, setOpen] = useState(false);
-  const cat = tx.categoryId ? categoryMap.get(tx.categoryId) : null;
-
-  if (!open) {
-    return (
-      <button
-        type="button"
-        onClick={() => setOpen(true)}
-        className="inline-flex h-6 items-center rounded px-1.5 text-xs hover:bg-accent"
-      >
-        {cat ? (
-          <Badge style={{ backgroundColor: cat.color, color: "#fff", border: "none" }}>
-            {cat.name}
-          </Badge>
-        ) : (
-          <span className="text-muted-foreground">Kategorie…</span>
-        )}
-      </button>
-    );
-  }
-
   return (
-    <Select
-      defaultOpen
-      value={tx.categoryId ?? "none"}
-      onValueChange={(v) => {
-        if (v !== "none") onUpdate(tx._id, v as Id<"categories">);
-        setOpen(false);
-      }}
-      onOpenChange={(o) => {
-        if (!o) setOpen(false);
-      }}
-    >
-      <SelectTrigger className="h-7 w-[130px]">
-        <SelectValue placeholder="Kategorie" />
-      </SelectTrigger>
-      <SelectContent>
-        {categories?.map((c) => (
-          <SelectItem key={c._id} value={c._id}>
-            <span className="inline-flex items-center gap-1.5">
-              <span
-                className="inline-block h-2.5 w-2.5 rounded-full"
-                style={{ backgroundColor: c.color }}
-              />
-              {c.name}
-            </span>
-          </SelectItem>
-        ))}
-      </SelectContent>
-    </Select>
+    <CategoryPicker
+      categories={categories}
+      value={tx.categoryId}
+      onSelect={(categoryId) => onUpdate(tx._id, categoryId)}
+    />
   );
 });
 
@@ -228,10 +183,6 @@ export function TransactionsPage() {
     { initialNumItems: 50 },
   );
 
-  const categoryMap = useMemo(
-    () => new Map(categories?.map((c) => [c._id, c])),
-    [categories],
-  );
   const accountMap = useMemo(
     () => new Map(accounts?.map((a) => [a._id, a.name])),
     [accounts],
@@ -247,8 +198,8 @@ export function TransactionsPage() {
   );
 
   const handleUpdateCategory = useCallback(
-    (id: Id<"transactions">, categoryId: Id<"categories">) => {
-      void updateTx({ id, categoryId });
+    async (id: Id<"transactions">, categoryId: Id<"categories">) => {
+      await updateTx({ id, categoryId });
     },
     [updateTx],
   );
@@ -343,7 +294,6 @@ export function TransactionsPage() {
           <CategoryCell
             tx={row.original}
             categories={categories}
-            categoryMap={categoryMap}
             onUpdate={handleUpdateCategory}
           />
         ),
@@ -382,7 +332,6 @@ export function TransactionsPage() {
     ],
     [
       categories,
-      categoryMap,
       accountMap,
       handleUpdateCategory,
       handleEdit,