Enforce session ownership in VertexAiSessionService.listEvents

core/src/main/java/com/google/adk/sessions/VertexAiSessionService.java

@@ -165,7 +165,26 @@ private ListSessionsResponse parseListSessionsResponse(
   @Override
   public Single<ListEventsResponse> listEvents(String appName, String userId, String sessionId) {
     validateSessionId(sessionId);
-    return listEventsInternal(appName, sessionId, /* filter= */ null);
+    String reasoningEngineId = parseReasoningEngineId(appName);
+    return client
+        .getSession(reasoningEngineId, sessionId)
+        .flatMapSingle(
+            getSessionResponseMap -> {
+              // Enforce ownership using the owner reported by the backend, not the
+              // requested user id, mirroring the check getSession/deleteSession use.
+              // Deny as empty so existence is not revealed to a non-owner.
+              String ownerUserId =
+                  Optional.ofNullable(getSessionResponseMap.get("userId"))
+                      .map(JsonNode::asText)
+                      .orElse(null);
+              if (!userId.equals(ownerUserId)) {
+                return Single.just(ListEventsResponse.builder().build());
+              }
+              return listEventsInternal(appName, sessionId, /* filter= */ null);
+            })
+        // No session found at all (rather than an ownership mismatch): behave the
+        // same as before, returning an empty response instead of erroring.
+        .defaultIfEmpty(ListEventsResponse.builder().build());
   }
 
   private Single<ListEventsResponse> listEventsInternal(

core/src/test/java/com/google/adk/sessions/VertexAiSessionServiceTest.java

@@ -422,6 +422,17 @@ public void getSession_wrongUser_returnsEmpty() {
         .isNull();
   }
 
+  @Test
+  public void listEvents_wrongUser_returnsEmpty() {
+    // Session "1" belongs to "user" and has an event in eventMap (MOCK_EVENT_STRING).
+    // A different user must not be able to read those events - mirrors
+    // getSession_wrongUser_returnsEmpty above, applied to listEvents.
+    ListEventsResponse response =
+        vertexAiSessionService.listEvents("123", "attacker", "1").blockingGet();
+
+    assertThat(response.events()).isEmpty();
+  }
+
   @Test
   public void deleteSession_wrongUser_deniedAndSessionKept() {
     // The ownership error surfaces on subscription, so hoist the Completable out.