fix: remove stdout prints, improve test determinism, and update trace handling

Removed `print` statements from the `LLMStreamChunkEvent` handler to prevent
LLM response chunks from being written directly to stdout. The listener now
only tracks chunks internally.

Fixes #3715

Added explicit return statements for trace-related tests.

Updated cassette for `test_failed_evaluation` to reflect new behavior where
an empty trace dict is used instead of returning early.

Ensured deterministic cleanup order in test fixtures by making
`clear_event_bus_handlers` depend on `setup_test_environment`. This guarantees
event bus shutdown and file handle cleanup occur before temporary directory
deletion, resolving intermittent “Directory not empty” errors in CI.

lib/crewai/src/crewai/events/event_listener.py

@@ -53,7 +53,6 @@ from crewai.task import Task
 from crewai.telemetry.telemetry import Telemetry
 from crewai.utilities import Logger
 from crewai.utilities.constants import EMITTER_COLOR
-from crewai.utilities.printer import Printer
 
 from .listeners.memory_listener import MemoryListener
 from .types.flow_events import (
@@ -76,8 +75,6 @@ from .types.tool_usage_events import (
     ToolUsageStartedEvent,
 )
 
-_printer = Printer()
-
 
 class EventListener(BaseEventListener):
     _instance = None
@@ -381,12 +378,8 @@ class EventListener(BaseEventListener):
         @crewai_event_bus.on(LLMStreamChunkEvent)
         def on_llm_stream_chunk(source, event: LLMStreamChunkEvent):
             self.text_stream.write(event.chunk)
-
             self.text_stream.seek(self.next_chunk)
-
+            self.text_stream.read()
-            # Read from the in-memory stream
-            content = self.text_stream.read()
-            _printer.print(content)
             self.next_chunk = self.text_stream.tell()
 
         # ----------- LLM GUARDRAIL EVENTS -----------

lib/crewai/src/crewai/experimental/evaluation/agent_evaluator.py

@@ -97,7 +97,7 @@ class AgentEvaluator:
             )
 
             if not trace:
-                return
+                trace = {}
 
             result = self.evaluate(
                 agent=agent,
@@ -151,7 +151,7 @@ class AgentEvaluator:
             )
 
             if not trace:
-                return
+                trace = {}
 
             result = self.evaluate(
                 agent=target_agent,

lib/crewai/tests/cassettes/TestAgentEvaluator.test_failed_evaluation.yaml

@@ -120,4 +120,105 @@ interactions:
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       message: OK
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+      0, "task_count": 0, "flow_method_count": 0, "execution_started_at": "2025-10-18T15:21:00.300365+00:00"},
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+      X-Crewai-Version:
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+    uri: https://app.crewai.com/crewai_plus/api/v1/tracing/ephemeral/batches
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lib/crewai/tests/conftest.py

@@ -160,11 +160,13 @@ def mock_opentelemetry_components():
 
 
 @pytest.fixture(autouse=True)
-def clear_event_bus_handlers():
+def clear_event_bus_handlers(setup_test_environment):
     """Clear event bus handlers after each test for isolation.
 
     Handlers registered during the test are allowed to run, then cleaned up
     after the test completes.
+
+    Depends on setup_test_environment to ensure cleanup happens in correct order.
     """
     from crewai.events.event_bus import crewai_event_bus
     from crewai.experimental.evaluation.evaluation_listener import (
@@ -173,6 +175,7 @@ def clear_event_bus_handlers():
 
     yield
 
+    # Shutdown event bus and wait for all handlers to complete
     crewai_event_bus.shutdown(wait=True)
     crewai_event_bus._initialize()