fix: rehydration of EventActions in StorageEvent.to_event

The change updates the `StorageEvent.to_event` method to use `EventActions.model_validate` when rehydrating the `actions` field. This ensures that nested models within `EventActions`, such as `EventCompaction`, are correctly reconstructed from the stored data

Close #4047

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 852408683

src/google/adk/sessions/schemas/v0.py

@@ -310,7 +310,11 @@ class StorageEvent(Base):
         branch=self.branch,
         # This is needed as previous ADK version pickled actions might not have
         # value defined in the current version of the EventActions model.
-        actions=EventActions().model_copy(update=self.actions.model_dump()),
+        actions=(
+            EventActions.model_validate(self.actions.model_dump())
+            if self.actions
+            else EventActions()
+        ),
         timestamp=self.timestamp.timestamp(),
         long_running_tool_ids=self.long_running_tool_ids,
         partial=self.partial,

tests/unittests/sessions/test_v0_storage_event.py

@@ -0,0 +1,50 @@
+# 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.
+
+from datetime import datetime
+from datetime import timezone
+
+from google.adk.events.event_actions import EventActions
+from google.adk.events.event_actions import EventCompaction
+from google.adk.sessions.schemas.v0 import StorageEvent
+from google.genai import types
+
+
+def test_storage_event_v0_to_event_rehydrates_compaction_model():
+  compaction = EventCompaction(
+      start_timestamp=1.0,
+      end_timestamp=2.0,
+      compacted_content=types.Content(
+          role="user",
+          parts=[types.Part(text="compacted")],
+      ),
+  )
+  actions = EventActions(compaction=compaction)
+  storage_event = StorageEvent(
+      id="event_id",
+      invocation_id="invocation_id",
+      author="author",
+      actions=actions,
+      session_id="session_id",
+      app_name="app_name",
+      user_id="user_id",
+      timestamp=datetime.fromtimestamp(3.0, tz=timezone.utc),
+  )
+
+  event = storage_event.to_event()
+
+  assert event.actions is not None
+  assert isinstance(event.actions.compaction, EventCompaction)
+  assert event.actions.compaction.start_timestamp == 1.0
+  assert event.actions.compaction.end_timestamp == 2.0