feat: Update event compaction logic to include events after compaction end times

Events are retained if they occur before the start of any compaction or after the end of any compaction.

PiperOrigin-RevId: 856868176

Author: google-genai-bot

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

@@ -209,12 +209,15 @@ private List<Event> processCompactionEvent(List<Event> events) {
     List<Event> result = new ArrayList<>();
     ListIterator<Event> iter = events.listIterator(events.size());
     Long lastCompactionStartTime = null;
+    Long lastCompactionEndTime = null;
 
     while (iter.hasPrevious()) {
       Event event = iter.previous();
       EventCompaction compaction = event.actions().compaction().orElse(null);
       if (compaction == null) {
-        if (lastCompactionStartTime == null || event.timestamp() < lastCompactionStartTime) {
+        if (lastCompactionStartTime == null
+            || event.timestamp() < lastCompactionStartTime
+            || (lastCompactionEndTime != null && event.timestamp() > lastCompactionEndTime)) {
           result.add(event);
         }
         continue;
@@ -233,6 +236,10 @@ private List<Event> processCompactionEvent(List<Event> events) {
           lastCompactionStartTime == null
               ? compaction.startTimestamp()
               : Long.min(lastCompactionStartTime, compaction.startTimestamp());
+      lastCompactionEndTime =
+          lastCompactionEndTime == null
+              ? compaction.endTimestamp()
+              : Long.max(lastCompactionEndTime, compaction.endTimestamp());
     }
     return Lists.reverse(result);
   }

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

@@ -561,6 +561,22 @@ public void processRequest_multipleCompactions() {
         .containsExactly("Summary 1-4", "content 5", "Summary 6-9", "content 10");
   }
 
+  @Test
+  public void processRequest_compactionWithUncompactedEventsBetween() {
+    ImmutableList<Event> events =
+        ImmutableList.of(
+            createUserEvent("e1", "content 1", "inv1", 1),
+            createUserEvent("e2", "content 2", "inv2", 2),
+            createUserEvent("e3", "content 3", "inv3", 3),
+            createCompactedEvent(1, 2, "Summary 1-2"));
+
+    List<Content> contents = runContentsProcessor(events);
+    assertThat(contents)
+        .comparingElementsUsing(
+            transforming((Content c) -> c.parts().get().get(0).text().get(), "content text"))
+        .containsExactly("content 3", "Summary 1-2");
+  }
+
   private static Event createUserEvent(String id, String text) {
     return Event.builder()
         .id(id)