diff --git a/src/components/balance/LinkTransfersModal.render.test.tsx b/src/components/balance/LinkTransfersModal.render.test.tsx
new file mode 100644
index 0000000..392ff03
--- /dev/null
+++ b/src/components/balance/LinkTransfersModal.render.test.tsx
@@ -0,0 +1,69 @@
+// LinkTransfersModal — the category filter is a combobox (#429). No jsdom:
+// react-dom/server renders the initial markup in vitest's node environment.
+// It cannot render a portal, and the window is one: `createPortal` becomes
+// the identity, and `document` a stub for the `document.body` it is given.
+import { describe, it, expect, vi, beforeAll, afterAll } from "vitest";
+import type { ReactNode } from "react";
+import { renderToStaticMarkup } from "react-dom/server";
+
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
+vi.mock("react-dom", async (orig) => ({
+  ...(await orig<typeof import("react-dom")>()),
+  createPortal: (children: ReactNode) => children,
+}));
+vi.mock("../../services/transactionService", () => ({
+  getTransactionPage: vi.fn(() => new Promise(() => undefined)),
+}));
+vi.mock("../../services/balance.service", () => ({
+  linkTransfer: vi.fn(),
+  suggestTransferDirection: vi.fn(() => "in"),
+  BalanceServiceError: class extends Error {},
+}));
+
+import LinkTransfersModal from "./LinkTransfersModal";
+import type { Category } from "../../shared/types";
+
+const TRANSFERS: Category = {
+  id: 7,
+  name: "Virements",
+  type: "transfer",
+  is_active: true,
+  is_inputable: true,
+  sort_order: 1,
+  created_at: "",
+};
+
+beforeAll(() => {
+  vi.stubGlobal("document", { body: {} });
+});
+
+afterAll(() => {
+  vi.unstubAllGlobals();
+});
+
+const markup = () =>
+  renderToStaticMarkup(
+    <LinkTransfersModal
+      accountId={1}
+      accountName="CELI"
+      categories={[TRANSFERS]}
+      initialFrom="2026-07-01"
+      initialTo="2026-09-30"
+      onClose={vi.fn()}
+    />,
+  );
+
+describe("LinkTransfersModal — category filter (#429)", () => {
+  it("renders the filter as a combobox, and no select", () => {
+    const html = markup();
+    expect(html.match(/<input [^>]*role="combobox"[^>]*>/g) ?? []).toHaveLength(1);
+    expect(html).not.toContain("<select");
+  });
+
+  it("opens on 'any category', named, compact like the other filters", () => {
+    const [input] = markup().match(/<input [^>]*role="combobox"[^>]*>/g) ?? [];
+    expect(input).toContain('value="t(balance.transfers.modal.anyCategory)"');
+    expect(input).toContain('aria-label="t(balance.transfers.modal.category)"');
+    expect(input).toMatch(/class="w-full px-2 py-1 /);
+  });
+});
diff --git a/src/components/balance/LinkTransfersModal.tsx b/src/components/balance/LinkTransfersModal.tsx
index 3a74b86..3157e78 100644
--- a/src/components/balance/LinkTransfersModal.tsx
+++ b/src/components/balance/LinkTransfersModal.tsx
@@ -3,7 +3,7 @@
 //
 // Filters available:
 //   - Period (from / to ISO dates) — default: last 90 days.
-//   - Category dropdown.
+//   - Category combobox, "any category" first (#429).
 //   - Free-text search on description.
 //
 // Each row shows: date, description, amount, suggested direction
@@ -29,6 +29,7 @@ import type {
   TransactionRow,
   BalanceTransferDirection,
 } from "../../shared/types";
+import CategoryCombobox from "../shared/CategoryCombobox";
 
 const DEFAULT_PAGE_SIZE = 100;
 
@@ -49,7 +50,7 @@ export interface LinkTransfersModalProps {
   /** Account that the selected transfers will be attached to. */
   accountId: number;
   accountName: string;
-  /** Full category list for the filter dropdown. */
+  /** Categories offered by the filter combobox. */
   categories: Category[];
   /** Optional pre-fill date bounds (defaults to last 90 days). */
   initialFrom?: string;
@@ -96,6 +97,13 @@ export default function LinkTransfersModal({
     [i18n.language]
   );
 
+  // "Any category" first: the filter's empty value (null), as on the
+  // Transactions page's filter bar.
+  const categoryExtras = useMemo(
+    () => [{ value: "", label: t("balance.transfers.modal.anyCategory") }],
+    [t]
+  );
+
   // Re-fetch whenever the filters change. Debounced via React's render cycle
   // — typing in the search box re-runs the SQL but at < 500 rows that's fine.
   useEffect(() => {
@@ -256,20 +264,16 @@ export default function LinkTransfersModal({
             <span className="block text-[var(--muted-foreground)] mb-1">
               {t("balance.transfers.modal.category")}
             </span>
-            <select
-              value={categoryId === null ? "" : String(categoryId)}
-              onChange={(e) =>
-                setCategoryId(e.target.value === "" ? null : Number(e.target.value))
-              }
-              className="w-full px-2 py-1.5 bg-[var(--background)] border border-[var(--border)] rounded text-sm"
-            >
-              <option value="">{t("balance.transfers.modal.anyCategory")}</option>
-              {categories.map((c) => (
-                <option key={c.id} value={c.id}>
-                  {c.name}
-                </option>
-              ))}
-            </select>
+            <CategoryCombobox
+              categories={categories}
+              value={categoryId}
+              onChange={(id) => setCategoryId(id)}
+              compact
+              ariaLabel={t("balance.transfers.modal.category")}
+              extraOptions={categoryExtras}
+              activeExtra={categoryId === null ? "" : null}
+              onExtraSelect={() => setCategoryId(null)}
+            />
           </label>
           <label className="text-xs">
             <span className="block text-[var(--muted-foreground)] mb-1">
diff --git a/src/components/balance/LinkTransfersModal.wiring.test.ts b/src/components/balance/LinkTransfersModal.wiring.test.ts
new file mode 100644
index 0000000..acd9e53
--- /dev/null
+++ b/src/components/balance/LinkTransfersModal.wiring.test.ts
@@ -0,0 +1,129 @@
+// LinkTransfersModal — what the category filter changes (#429).
+//
+// A static render runs no effect and clicks nothing. React's hooks come from
+// the shared harness (src/test/hookHarness.ts, #409): the window runs as a
+// plain function, its state survives from one call to the next, the test
+// calls the props it hands to its CategoryCombobox, renders again to read the
+// filter, and `commit()` runs the effect that reloads the transactions.
+// `createPortal` is the identity and `document` a stub: the window is a portal.
+import { describe, it, expect, vi, beforeAll, afterAll, beforeEach } from "vitest";
+import { isValidElement, type ReactElement, type ReactNode } from "react";
+
+vi.mock("react", async (orig) => (await import("../../test/hookHarness")).fakeReact(await orig()));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
+vi.mock("react-dom", async (orig) => ({
+  ...(await orig<typeof import("react-dom")>()),
+  createPortal: (children: ReactNode) => children,
+}));
+const { getTransactionPage } = vi.hoisted(() => ({ getTransactionPage: vi.fn() }));
+vi.mock("../../services/transactionService", () => ({ getTransactionPage }));
+vi.mock("../../services/balance.service", () => ({
+  linkTransfer: vi.fn(),
+  suggestTransferDirection: vi.fn(() => "in"),
+  BalanceServiceError: class extends Error {},
+}));
+
+import { hookHarness } from "../../test/hookHarness";
+import LinkTransfersModal from "./LinkTransfersModal";
+import CategoryCombobox from "../shared/CategoryCombobox";
+import type { Category } from "../../shared/types";
+
+const harness = hookHarness();
+
+type Props = Record<string, unknown> & { children?: ReactNode };
+
+function find(node: ReactNode, type: unknown): ReactElement<Props>[] {
+  if (Array.isArray(node)) return node.flatMap((n) => find(n, type));
+  if (!isValidElement(node)) return [];
+  const el = node as ReactElement<Props>;
+  return [...(el.type === type ? [el] : []), ...find(el.props.children, type)];
+}
+
+const TRANSFERS: Category = {
+  id: 7,
+  name: "Virements",
+  type: "transfer",
+  is_active: true,
+  is_inputable: true,
+  sort_order: 1,
+  created_at: "",
+};
+const CATEGORIES = [TRANSFERS];
+
+const PROPS = {
+  accountId: 1,
+  accountName: "CELI",
+  categories: CATEGORIES,
+  initialFrom: "2026-07-01",
+  initialTo: "2026-09-30",
+  onClose: vi.fn(),
+};
+
+/** One render of the mounted window; its category filter. */
+const filter = () => {
+  const [combobox] = find(harness.render(() => LinkTransfersModal(PROPS)), CategoryCombobox);
+  return combobox.props;
+};
+
+/** The category of the last transaction query. */
+const queriedCategory = () => {
+  const calls = getTransactionPage.mock.calls;
+  return (calls[calls.length - 1][0] as { categoryId: number | null }).categoryId;
+};
+
+/** Lets the query's promise settle. */
+const flush = async () => {
+  for (let i = 0; i < 10; i++) await Promise.resolve();
+};
+
+beforeAll(() => {
+  vi.stubGlobal("document", { body: {} });
+});
+
+afterAll(() => {
+  vi.unstubAllGlobals();
+});
+
+beforeEach(() => {
+  harness.clear();
+  getTransactionPage.mockReset();
+  getTransactionPage.mockResolvedValue({ rows: [], total: 0 });
+});
+
+describe("LinkTransfersModal — category filter (#429)", () => {
+  it("opens on 'any category', first of the list, with the categories it is given", () => {
+    const props = filter();
+    expect(props.extraOptions).toEqual([{ value: "", label: "t(balance.transfers.modal.anyCategory)" }]);
+    expect(props.activeExtra).toBe("");
+    expect(props.value).toBeNull();
+    expect(props.categories).toBe(CATEGORIES);
+    expect(props.compact).toBe(true);
+    expect(props.ariaLabel).toBe("t(balance.transfers.modal.category)");
+  });
+
+  it("filters on the category picked, then 'any category' empties the filter again", async () => {
+    filter();
+    harness.commit();
+    await flush();
+    expect(getTransactionPage).toHaveBeenCalledTimes(1);
+    expect(queriedCategory()).toBeNull();
+
+    (filter().onChange as (id: number) => void)(TRANSFERS.id);
+    let props = filter();
+    expect(props.value).toBe(TRANSFERS.id);
+    expect(props.activeExtra).toBeNull();
+    harness.commit();
+    await flush();
+    expect(getTransactionPage).toHaveBeenCalledTimes(2);
+    expect(queriedCategory()).toBe(TRANSFERS.id);
+
+    (props.onExtraSelect as (value: string) => void)("");
+    props = filter();
+    expect(props.value).toBeNull();
+    expect(props.activeExtra).toBe("");
+    harness.commit();
+    await flush();
+    expect(getTransactionPage).toHaveBeenCalledTimes(3);
+    expect(queriedCategory()).toBeNull();
+  });
+});