From eb5333931d4bad827039a8ff6fab1e36164cc57f Mon Sep 17 00:00:00 2001
From: KoushikReddy <koushik.7rdd@gmail.com>
Date: Wed, 17 Jun 2026 12:23:02 -0700
Subject: [PATCH] fix(evaluation): skip invocations without user events in
 convert_events_to_eval_invocations

Sessions can contain invocation_ids whose events are all authored by agents
or tools (e.g. internal/background turns with no corresponding user message).
Previously, convert_events_to_eval_invocations left user_content as an empty
Content(parts=[]), which produces a semantically meaningless eval case, and
earlier versions used an empty string which raised a Pydantic ValidationError
because Invocation.user_content requires a genai_types.Content object.

Invocations without a user-authored event are not meaningful for evaluation,
so skip them instead of constructing an Invocation with a placeholder
user_content. A debug log line is emitted for each skipped invocation to aid
troubleshooting.

Fixes #3760
---
 .../adk/evaluation/evaluation_generator.py    | 14 +++++-
 .../evaluation/test_evaluation_generator.py   | 46 +++++++++++++++++++
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/src/google/adk/evaluation/evaluation_generator.py b/src/google/adk/evaluation/evaluation_generator.py
index e277a43d9d..edf8273cdd 100644
--- a/src/google/adk/evaluation/evaluation_generator.py
+++ b/src/google/adk/evaluation/evaluation_generator.py
@@ -628,7 +628,7 @@ def convert_events_to_eval_invocations(
     for invocation_id, events in events_by_invocation_id.items():
       final_response = None
       final_event: Optional[Event] = None
-      user_content = Content(parts=[])
+      user_content = None
       invocation_timestamp = 0
       app_details = None
       if (
@@ -664,6 +664,18 @@ def convert_events_to_eval_invocations(
               events_to_add.append(event)
               break
 
+      if user_content is None:
+        # Skip invocations that have no user-authored event.  Such invocations
+        # arise from internal/system-driven turns (e.g. background agent tasks)
+        # and are not meaningful for evaluation purposes.  Including them would
+        # also cause a Pydantic ValidationError because Invocation.user_content
+        # requires a Content object.
+        logger.debug(
+            "Skipping invocation %s: no user-authored event found.",
+            invocation_id,
+        )
+        continue
+
       invocation_events = [
           InvocationEvent(author=e.author, content=e.content)
           for e in events_to_add
diff --git a/tests/unittests/evaluation/test_evaluation_generator.py b/tests/unittests/evaluation/test_evaluation_generator.py
index 76e0379142..4c524f61de 100644
--- a/tests/unittests/evaluation/test_evaluation_generator.py
+++ b/tests/unittests/evaluation/test_evaluation_generator.py
@@ -231,6 +231,52 @@ def test_convert_multi_agent_final_responses(
     assert intermediate_events[0].author == "agent1"
     assert intermediate_events[0].content.parts[0].text == "First response"
 
+  def test_invocation_without_user_event_is_skipped(self):
+    """Invocations with no user-authored event must be skipped.
+
+    Regression test for https://github.com/google/adk-python/issues/3760.
+    When a session contains an invocation_id whose events are all authored by
+    agents or tools (no 'user' event), convert_events_to_eval_invocations used
+    to leave user_content as a bare string, causing a Pydantic ValidationError
+    from Invocation.user_content which requires genai_types.Content.
+    The fix skips such invocations because they represent internal/system-driven
+    turns that are not meaningful for evaluation.
+    """
+    events = [
+        _build_event("agent", [types.Part(text="agent-only event")], "inv1"),
+    ]
+
+    # Must not raise a Pydantic ValidationError.
+    invocations = EvaluationGenerator.convert_events_to_eval_invocations(events)
+
+    assert (
+        invocations == []
+    ), "Invocations without a user event should be skipped."
+
+  def test_mixed_invocations_skips_only_agent_only_ones(self):
+    """Only agent-only invocations are skipped; normal invocations are kept.
+
+    Regression test for https://github.com/google/adk-python/issues/3760.
+    """
+    events = [
+        # inv1: normal user+agent turn — should be kept.
+        _build_event("user", [types.Part(text="Hello")], "inv1"),
+        _build_event("agent", [types.Part(text="Hi there!")], "inv1"),
+        # inv2: agent-only turn (e.g. background/system task) — should be skipped.
+        _build_event("agent", [types.Part(text="Internal work")], "inv2"),
+        # inv3: normal user+agent turn — should be kept.
+        _build_event("user", [types.Part(text="Follow-up")], "inv3"),
+        _build_event("agent", [types.Part(text="Sure!")], "inv3"),
+    ]
+
+    invocations = EvaluationGenerator.convert_events_to_eval_invocations(events)
+
+    assert len(invocations) == 2
+    assert invocations[0].invocation_id == "inv1"
+    assert invocations[0].user_content.parts[0].text == "Hello"
+    assert invocations[1].invocation_id == "inv3"
+    assert invocations[1].user_content.parts[0].text == "Follow-up"
+
 
 class TestGetAppDetailsByInvocationId:
   """Test cases for EvaluationGenerator._get_app_details_by_invocation_id method."""