fix(memory): skip non-text parts and use millis timestamps in memory search

core/src/main/java/com/google/adk/memory/InMemoryMemoryService.java

@@ -136,6 +136,6 @@ public Single<SearchMemoryResponse> searchMemory(String appName, String userId,
   }
 
   private String formatTimestamp(long timestamp) {
-    return Instant.ofEpochSecond(timestamp).toString();
+    return Instant.ofEpochMilli(timestamp).toString();
   }
 }

core/src/test/java/com/google/adk/memory/InMemoryMemoryServiceTimestampTest.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.adk.memory;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.adk.events.Event;
+import com.google.adk.sessions.Session;
+import com.google.common.collect.ImmutableList;
+import com.google.genai.types.Content;
+import com.google.genai.types.Part;
+import java.time.Instant;
+import java.util.concurrent.ConcurrentHashMap;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public final class InMemoryMemoryServiceTimestampTest {
+
+  private final InMemoryMemoryService memoryService = new InMemoryMemoryService();
+
+  /** Memory timestamps are rendered from epoch milliseconds, matching {@link Event#timestamp()}. */
+  @Test
+  public void searchMemory_formatsTimestampAsEpochMillis() {
+    long epochMillis = 1_700_000_000_000L;
+    Session session =
+        Session.builder("session-1")
+            .appName("app")
+            .userId("user")
+            .state(new ConcurrentHashMap<>())
+            .events(
+                ImmutableList.of(
+                    Event.builder()
+                        .author("user")
+                        .content(
+                            Content.builder()
+                                .role("user")
+                                .parts(Part.fromText("My name is James"))
+                                .build())
+                        .timestamp(epochMillis)
+                        .build()))
+            .build();
+
+    memoryService.addSessionToMemory(session).blockingAwait();
+
+    SearchMemoryResponse response = memoryService.searchMemory("app", "user", "name").blockingGet();
+
+    assertThat(response.memories()).hasSize(1);
+    assertThat(response.memories().get(0).timestamp())
+        .isEqualTo(Instant.ofEpochMilli(epochMillis).toString());
+  }
+}