diff --git a/src/actions/housekeeping-preferences.test.ts b/src/actions/housekeeping-preferences.test.ts
index 767ad753..1f34c2b6 100644
--- a/src/actions/housekeeping-preferences.test.ts
+++ b/src/actions/housekeeping-preferences.test.ts
@@ -1,4 +1,4 @@
-import { beforeEach, describe, expect, it, vi } from "vitest";
+import { beforeEach, describe, expect, expectTypeOf, it, vi } from "vitest";
 
 vi.mock("@/features/housekeeping/foundation/server-capability-context", () => ({
 	getHousekeepingCapabilityContext: vi.fn(),
@@ -40,6 +40,15 @@ describe("housekeeping preference actions", () => {
 		expect(saveHousekeepingPreferences).toHaveLength(1);
 	});
 
+	it("publishes exact action signatures without caller-controlled dependencies", () => {
+		expectTypeOf<
+			Parameters<typeof loadHousekeepingPreferences>
+		>().toEqualTypeOf<[]>();
+		expectTypeOf<
+			Parameters<typeof saveHousekeepingPreferences>
+		>().toEqualTypeOf<[input: unknown]>();
+	});
+
 	it("derives the read owner from the server capability context", async () => {
 		const result = await loadHousekeepingPreferences();
 
diff --git a/src/features/housekeeping/foundation/preferences/schema.test.ts b/src/features/housekeeping/foundation/preferences/schema.test.ts
index 8067ce16..7c9687dd 100644
--- a/src/features/housekeeping/foundation/preferences/schema.test.ts
+++ b/src/features/housekeeping/foundation/preferences/schema.test.ts
@@ -71,4 +71,21 @@ describe("housekeeping preferences schema", () => {
 			}).success,
 		).toBe(false);
 	});
+
+	it("rejects a Unicode payload whose UTF-8 bytes exceed the 4096-byte limit", () => {
+		const value = {
+			...defaultHousekeepingPreferences(),
+			pinnedRouteIds: Array.from(
+				{ length: 29 },
+				(_, index) => `${index.toString().padStart(3, "0")}${"é".repeat(125)}`,
+			),
+		};
+		const serialized = JSON.stringify(value);
+
+		expect(serialized.length).toBeLessThanOrEqual(4096);
+		expect(new TextEncoder().encode(serialized).byteLength).toBeGreaterThan(
+			4096,
+		);
+		expect(housekeepingPreferencesSchema.safeParse(value).success).toBe(false);
+	});
 });
diff --git a/src/features/housekeeping/foundation/preferences/schema.ts b/src/features/housekeeping/foundation/preferences/schema.ts
index 0bed8f8f..f1dba0df 100644
--- a/src/features/housekeeping/foundation/preferences/schema.ts
+++ b/src/features/housekeeping/foundation/preferences/schema.ts
@@ -45,7 +45,7 @@ export const housekeepingPreferencesSchema: z.ZodType<HousekeepingPreferences> =
 		.strict()
 		.superRefine((preferences, context) => {
 			if (
-				JSON.stringify(preferences).length >
+				new TextEncoder().encode(JSON.stringify(preferences)).byteLength >
 				HOUSEKEEPING_PREFERENCE_MAX_SERIALIZED_BYTES
 			) {
 				context.addIssue({