feat: Add Compact processor to SingleFlow

PiperOrigin-RevId: 865218993

Author: google-genai-bot

core/src/main/java/com/google/adk/flows/llmflows/SingleFlow.java

@@ -30,6 +30,7 @@ public class SingleFlow extends BaseLlmFlow {
           new RequestConfirmationLlmRequestProcessor(),
           new Instructions(),
           new Identity(),
+          new Compaction(),
           new Contents(),
           new Examples(),
           CodeExecution.requestProcessor);

core/src/test/java/com/google/adk/flows/llmflows/SingleFlowTest.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2026 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.flows.llmflows;
+
+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 SingleFlowTest {
+
+  @Test
+  public void requestProcessors_containsCompaction() {
+    boolean hasCompaction =
+        SingleFlow.REQUEST_PROCESSORS.stream()
+            .anyMatch(processor -> processor instanceof Compaction);
+    assertThat(hasCompaction).isTrue();
+  }
+}