feat: Adding a Builder for EventsCompactionConfig

core/src/main/java/com/google/adk/summarizer/EventsCompactionConfig.java

@@ -16,6 +16,8 @@
 
 package com.google.adk.summarizer;
 
+import com.google.auto.value.AutoBuilder;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import javax.annotation.Nullable;
 
 /**
@@ -39,6 +41,35 @@ public record EventsCompactionConfig(
     @Nullable Integer tokenThreshold,
     @Nullable Integer eventRetentionSize) {
 
+  public static Builder builder() {
+    return new AutoBuilder_EventsCompactionConfig_Builder();
+  }
+
+  public Builder toBuilder() {
+    return new AutoBuilder_EventsCompactionConfig_Builder(this);
+  }
+
+  /** Builder for {@link EventsCompactionConfig}. */
+  @AutoBuilder
+  public abstract static class Builder {
+    @CanIgnoreReturnValue
+    public abstract Builder compactionInterval(@Nullable Integer compactionInterval);
+
+    @CanIgnoreReturnValue
+    public abstract Builder overlapSize(@Nullable Integer overlapSize);
+
+    @CanIgnoreReturnValue
+    public abstract Builder summarizer(@Nullable BaseEventSummarizer summarizer);
+
+    @CanIgnoreReturnValue
+    public abstract Builder tokenThreshold(@Nullable Integer tokenThreshold);
+
+    @CanIgnoreReturnValue
+    public abstract Builder eventRetentionSize(@Nullable Integer eventRetentionSize);
+
+    public abstract EventsCompactionConfig build();
+  }
+
   public EventsCompactionConfig(int compactionInterval, int overlapSize) {
     this(compactionInterval, overlapSize, null, null, null);
   }

core/src/test/java/com/google/adk/summarizer/EventsCompactionConfigTest.java

@@ -0,0 +1,55 @@
+/*
+ * 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.summarizer;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public final class EventsCompactionConfigTest {
+
+  @Test
+  public void builder_buildsConfig() {
+    EventsCompactionConfig config =
+        EventsCompactionConfig.builder()
+            .compactionInterval(10)
+            .overlapSize(2)
+            .tokenThreshold(100)
+            .eventRetentionSize(5)
+            .build();
+
+    assertThat(config.compactionInterval()).isEqualTo(10);
+    assertThat(config.overlapSize()).isEqualTo(2);
+    assertThat(config.tokenThreshold()).isEqualTo(100);
+    assertThat(config.eventRetentionSize()).isEqualTo(5);
+    assertThat(config.summarizer()).isNull();
+  }
+
+  @Test
+  public void toBuilder_rebuildsConfig() {
+    EventsCompactionConfig config =
+        EventsCompactionConfig.builder().compactionInterval(10).overlapSize(2).build();
+
+    EventsCompactionConfig rebuilt = config.toBuilder().compactionInterval(20).build();
+
+    assertThat(rebuilt.compactionInterval()).isEqualTo(20);
+    assertThat(rebuilt.overlapSize()).isEqualTo(2);
+  }
+}