diff --git a/src/test-utils/session-state-cleanup.test.ts b/src/test-utils/session-state-cleanup.test.ts
index 2259369005f..9c469a313c2 100644
--- a/src/test-utils/session-state-cleanup.test.ts
+++ b/src/test-utils/session-state-cleanup.test.ts
@@ -1,12 +1,29 @@
 import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
-import { afterEach, describe, expect, it } from "vitest";
-import {
-  getSessionStoreLockQueueSizeForTest,
-  withSessionStoreLockForTest,
-} from "../config/sessions/store.js";
-import { cleanupSessionStateForTest } from "./session-state-cleanup.js";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+const acquireSessionWriteLockMock = vi.hoisted(() =>
+  vi.fn(async () => ({ release: vi.fn(async () => {}) })),
+);
+
+let getSessionStoreLockQueueSizeForTest: typeof import("../config/sessions/store.js").getSessionStoreLockQueueSizeForTest;
+let withSessionStoreLockForTest: typeof import("../config/sessions/store.js").withSessionStoreLockForTest;
+let cleanupSessionStateForTest: typeof import("./session-state-cleanup.js").cleanupSessionStateForTest;
+
+async function loadFreshCleanupModules() {
+  vi.resetModules();
+  vi.doMock("../agents/session-write-lock.js", async (importOriginal) => {
+    const original = await importOriginal<typeof import("../agents/session-write-lock.js")>();
+    return {
+      ...original,
+      acquireSessionWriteLock: acquireSessionWriteLockMock,
+    };
+  });
+  ({ getSessionStoreLockQueueSizeForTest, withSessionStoreLockForTest } =
+    await import("../config/sessions/store.js"));
+  ({ cleanupSessionStateForTest } = await import("./session-state-cleanup.js"));
+}
 
 function createDeferred<T>() {
   let resolve!: (value: T | PromiseLike<T>) => void;
@@ -19,8 +36,14 @@ function createDeferred<T>() {
 }
 
 describe("cleanupSessionStateForTest", () => {
+  beforeEach(async () => {
+    acquireSessionWriteLockMock.mockClear();
+    await loadFreshCleanupModules();
+  });
+
   afterEach(async () => {
     await cleanupSessionStateForTest();
+    vi.restoreAllMocks();
   });
 
   it("waits for in-flight session store locks before clearing test state", async () => {