diff --git a/src/agents/subagent-announce.format.e2e.test.ts b/src/agents/subagent-announce.format.e2e.test.ts
index e30b313f49d..be1d287aa3c 100644
--- a/src/agents/subagent-announce.format.e2e.test.ts
+++ b/src/agents/subagent-announce.format.e2e.test.ts
@@ -118,14 +118,18 @@ vi.mock("./tools/agent-step.js", () => ({
   readLatestAssistantReply: readLatestAssistantReplyMock,
 }));
 
-vi.mock("../config/sessions.js", () => ({
-  loadSessionStore: vi.fn(() => loadSessionStoreFixture()),
-  resolveAgentIdFromSessionKey: () => "main",
-  resolveStorePath: () => "/tmp/sessions.json",
-  resolveMainSessionKey: () => "agent:main:main",
-  readSessionUpdatedAt: vi.fn(() => undefined),
-  recordSessionMetaFromInbound: vi.fn().mockResolvedValue(undefined),
-}));
+vi.mock("../config/sessions.js", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("../config/sessions.js")>();
+  return {
+    ...actual,
+    loadSessionStore: vi.fn(() => loadSessionStoreFixture()),
+    resolveAgentIdFromSessionKey: () => "main",
+    resolveStorePath: () => "/tmp/sessions.json",
+    resolveMainSessionKey: () => "agent:main:main",
+    readSessionUpdatedAt: vi.fn(() => undefined),
+    recordSessionMetaFromInbound: vi.fn().mockResolvedValue(undefined),
+  };
+});
 
 vi.mock("./pi-embedded.js", () => embeddedRunMock);
 
diff --git a/src/telegram/bot.media.e2e-harness.ts b/src/telegram/bot.media.e2e-harness.ts
index fec64cbdbf0..58628df522b 100644
--- a/src/telegram/bot.media.e2e-harness.ts
+++ b/src/telegram/bot.media.e2e-harness.ts
@@ -83,11 +83,15 @@ vi.mock("@grammyjs/transformer-throttler", () => ({
 
 vi.mock("../media/store.js", async (importOriginal) => {
   const actual = await importOriginal<typeof import("../media/store.js")>();
-  return {
-    ...actual,
-    saveMediaBuffer: (...args: Parameters<typeof saveMediaBufferSpy>) =>
-      saveMediaBufferSpy(...args),
-  };
+  const mockModule = Object.create(null) as Record<string, unknown>;
+  Object.defineProperties(mockModule, Object.getOwnPropertyDescriptors(actual));
+  Object.defineProperty(mockModule, "saveMediaBuffer", {
+    configurable: true,
+    enumerable: true,
+    writable: true,
+    value: (...args: Parameters<typeof saveMediaBufferSpy>) => saveMediaBufferSpy(...args),
+  });
+  return mockModule;
 });
 
 vi.mock("../config/config.js", async (importOriginal) => {
diff --git a/src/web/test-helpers.ts b/src/web/test-helpers.ts
index b4cbe125f66..3e8964b507d 100644
--- a/src/web/test-helpers.ts
+++ b/src/web/test-helpers.ts
@@ -64,14 +64,23 @@ vi.mock("../../config/config.js", async (importOriginal) => {
   };
 });
 
-vi.mock("../media/store.js", () => ({
-  saveMediaBuffer: vi.fn().mockImplementation(async (_buf: Buffer, contentType?: string) => ({
-    id: "mid",
-    path: "/tmp/mid",
-    size: _buf.length,
-    contentType,
-  })),
-}));
+vi.mock("../media/store.js", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("../media/store.js")>();
+  const mockModule = Object.create(null) as Record<string, unknown>;
+  Object.defineProperties(mockModule, Object.getOwnPropertyDescriptors(actual));
+  Object.defineProperty(mockModule, "saveMediaBuffer", {
+    configurable: true,
+    enumerable: true,
+    writable: true,
+    value: vi.fn().mockImplementation(async (_buf: Buffer, contentType?: string) => ({
+      id: "mid",
+      path: "/tmp/mid",
+      size: _buf.length,
+      contentType,
+    })),
+  });
+  return mockModule;
+});
 
 vi.mock("@whiskeysockets/baileys", () => {
   const created = createMockBaileys();
diff --git a/vitest.e2e.config.ts b/vitest.e2e.config.ts
index f21205c1abe..b70d8c8eedb 100644
--- a/vitest.e2e.config.ts
+++ b/vitest.e2e.config.ts
@@ -21,7 +21,9 @@ export default defineConfig({
   ...base,
   test: {
     ...baseTest,
-    pool: "vmForks",
+    // vmForks reuses VM contexts in ways that can leak module state/mocks across
+    // files for our e2e harnesses. Use process forks for deterministic isolation.
+    pool: "forks",
     maxWorkers: e2eWorkers,
     silent: !verboseE2E,
     include: ["test/**/*.e2e.test.ts", "src/**/*.e2e.test.ts"],