diff --git a/src/auto-reply/reply/session.heartbeat-no-reset.test.ts b/src/auto-reply/reply/session.heartbeat-no-reset.test.ts
index fa1d515ccaa..583b59cdd3f 100644
--- a/src/auto-reply/reply/session.heartbeat-no-reset.test.ts
+++ b/src/auto-reply/reply/session.heartbeat-no-reset.test.ts
@@ -82,6 +82,14 @@ describe("initSessionState - heartbeat should not trigger session reset", () =>
     });
   };
 
+  const expectPersistedSession = (sessionStore: Record<string, SessionEntry>): SessionEntry => {
+    const entry = sessionStore["main:user123"];
+    if (!entry) {
+      throw new Error("Expected persisted session for main:user123");
+    }
+    return entry;
+  };
+
   it("should NOT reset session when Provider is 'heartbeat'", async () => {
     // Setup: Create a session entry that is "stale" (older than idle timeout)
     const now = Date.now();
@@ -191,7 +199,7 @@ describe("initSessionState - heartbeat should not trigger session reset", () =>
     expect(heartbeatResult.sessionEntry.lastInteractionAt).toBe(staleTime);
 
     const persistedAfterHeartbeat = loadSessionStore(storePath);
-    expect(persistedAfterHeartbeat["main:user123"]?.lastInteractionAt).toBe(staleTime);
+    expect(expectPersistedSession(persistedAfterHeartbeat).lastInteractionAt).toBe(staleTime);
 
     const userResult = await initSessionState({
       ctx: createBaseCtx({
@@ -278,7 +286,7 @@ describe("initSessionState - heartbeat should not trigger session reset", () =>
     expect(heartbeatResult.sessionId).toBe("legacy-idle-session");
 
     const persistedAfterHeartbeat = loadSessionStore(storePath);
-    expect(persistedAfterHeartbeat["main:user123"]?.lastInteractionAt).toBeUndefined();
+    expect(expectPersistedSession(persistedAfterHeartbeat).lastInteractionAt).toBeUndefined();
 
     const userResult = await initSessionState({
       ctx: createBaseCtx({