fix: Update empty event check to include executable code and execution results

Close #3859
Close #3921

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 852375447

tests/unittests/flows/llm_flows/test_contents.py

@@ -572,6 +572,38 @@ async def test_events_with_empty_content_are_skipped():
               role="user",
           ),
       ),
+      # Event with content that has executable code part
+      Event(
+          invocation_id="inv10",
+          author="test_agent",
+          content=types.Content(
+              parts=[
+                  types.Part(
+                      executable_code=types.ExecutableCode(
+                          code="print('hello')",
+                          language="PYTHON",
+                      )
+                  )
+              ],
+              role="model",
+          ),
+      ),
+      # Event with content that has code execution result part
+      Event(
+          invocation_id="inv11",
+          author="test_agent",
+          content=types.Content(
+              parts=[
+                  types.Part(
+                      code_execution_result=types.CodeExecutionResult(
+                          outcome="OUTCOME_OK",
+                          output="hello",
+                      )
+                  )
+              ],
+              role="model",
+          ),
+      ),
   ]
   invocation_context.session.events = events
 
@@ -608,4 +640,153 @@ async def test_events_with_empty_content_are_skipped():
           parts=[types.Part(text=""), types.Part(text="Mixed content")],
           role="user",
       ),
+      types.Content(
+          parts=[
+              types.Part(
+                  executable_code=types.ExecutableCode(
+                      code="print('hello')",
+                      language="PYTHON",
+                  )
+              )
+          ],
+          role="model",
+      ),
+      types.Content(
+          parts=[
+              types.Part(
+                  code_execution_result=types.CodeExecutionResult(
+                      outcome="OUTCOME_OK",
+                      output="hello",
+                  )
+              )
+          ],
+          role="model",
+      ),
   ]
+
+
+@pytest.mark.asyncio
+async def test_code_execution_result_events_are_not_skipped():
+  """Test that events with code execution result are not skipped.
+
+  This is a regression test for the endless loop bug where code executor
+  outputs were not passed to the LLM because the events were incorrectly
+  filtered as empty.
+  """
+  agent = Agent(model="gemini-2.5-flash", name="test_agent")
+  llm_request = LlmRequest(model="gemini-2.5-flash")
+  invocation_context = await testing_utils.create_invocation_context(
+      agent=agent
+  )
+
+  events = [
+      Event(
+          invocation_id="inv1",
+          author="user",
+          content=types.UserContent("Write code to calculate factorial"),
+      ),
+      # Model generates code
+      Event(
+          invocation_id="inv2",
+          author="test_agent",
+          content=types.Content(
+              parts=[
+                  types.Part(text="Here's the code:"),
+                  types.Part(
+                      executable_code=types.ExecutableCode(
+                          code=(
+                              "def factorial(n):\n  return 1 if n <= 1 else n *"
+                              " factorial(n-1)\nprint(factorial(5))"
+                          ),
+                          language="PYTHON",
+                      )
+                  ),
+              ],
+              role="model",
+          ),
+      ),
+      # Code execution result
+      Event(
+          invocation_id="inv3",
+          author="test_agent",
+          content=types.Content(
+              parts=[
+                  types.Part(
+                      code_execution_result=types.CodeExecutionResult(
+                          outcome="OUTCOME_OK",
+                          output="120",
+                      )
+                  )
+              ],
+              role="model",
+          ),
+      ),
+  ]
+  invocation_context.session.events = events
+
+  # Process the request
+  async for _ in contents.request_processor.run_async(
+      invocation_context, llm_request
+  ):
+    pass
+
+  # Verify all three events are included, especially the code execution result
+  assert len(llm_request.contents) == 3
+  assert llm_request.contents[0] == types.UserContent(
+      "Write code to calculate factorial"
+  )
+  # Second event has executable code
+  assert llm_request.contents[1].parts[1].executable_code is not None
+  # Third event has code execution result - this was the bug!
+  assert llm_request.contents[2].parts[0].code_execution_result is not None
+  assert llm_request.contents[2].parts[0].code_execution_result.output == "120"
+
+
+@pytest.mark.asyncio
+async def test_code_execution_result_not_in_first_part_is_not_skipped():
+  """Test that code execution results aren't skipped.
+
+  This covers results that appear in a non-first part.
+  """
+  agent = Agent(model="gemini-2.5-flash", name="test_agent")
+  llm_request = LlmRequest(model="gemini-2.5-flash")
+  invocation_context = await testing_utils.create_invocation_context(
+      agent=agent
+  )
+
+  events = [
+      Event(
+          invocation_id="inv1",
+          author="user",
+          content=types.UserContent("Run some code."),
+      ),
+      Event(
+          invocation_id="inv2",
+          author="test_agent",
+          content=types.Content(
+              parts=[
+                  types.Part(text=""),
+                  types.Part(
+                      code_execution_result=types.CodeExecutionResult(
+                          outcome="OUTCOME_OK",
+                          output="42",
+                      )
+                  ),
+              ],
+              role="model",
+          ),
+      ),
+  ]
+  invocation_context.session.events = events
+
+  async for _ in contents.request_processor.run_async(
+      invocation_context, llm_request
+  ):
+    pass
+
+  assert len(llm_request.contents) == 2
+  assert any(
+      part.code_execution_result is not None
+      and part.code_execution_result.output == "42"
+      for part in llm_request.contents[1].parts
+  )