Add event emission for agent execution lifecycle

- Emit AgentExecutionStarted and AgentExecutionError events
- Update CrewAgentExecutor to use event_bus for tracking agent execution
- Refactor error handling to include event emission
- Minor code formatting improvements in task.py and crew_agent_executor.py
- Fix a typo in test file

src/crewai/agents/crew_agent_executor.py

@@ -18,6 +18,11 @@ from crewai.tools.base_tool import BaseTool
 from crewai.tools.tool_usage import ToolUsage, ToolUsageErrorException
 from crewai.utilities import I18N, Printer
 from crewai.utilities.constants import MAX_LLM_RETRY, TRAINING_DATA_FILE
+from crewai.utilities.events import event_bus
+from crewai.utilities.events.agent_events import (
+    AgentExecutionError,
+    AgentExecutionStarted,
+)
 from crewai.utilities.exceptions.context_window_exceeding_exception import (
     LLMContextLengthExceededException,
 )
@@ -85,6 +90,15 @@ class CrewAgentExecutor(CrewAgentExecutorMixin):
         self.llm.stop = list(set(self.llm.stop + self.stop))
 
     def invoke(self, inputs: Dict[str, str]) -> Dict[str, Any]:
+        event_bus.emit(
+            self,
+            event=AgentExecutionStarted(
+                agent=self.agent,
+                task=self.task,
+                tools=self.tools,
+                inputs=inputs,
+            ),
+        )
         if "system" in self.prompt:
             system_prompt = self._format_prompt(self.prompt.get("system", ""), inputs)
             user_prompt = self._format_prompt(self.prompt.get("user", ""), inputs)
@@ -107,11 +121,11 @@ class CrewAgentExecutor(CrewAgentExecutorMixin):
             )
             raise
         except Exception as e:
+            self._handle_unknown_error(e)
             if e.__class__.__module__.startswith("litellm"):
                 # Do not retry on litellm errors
                 raise e
             else:
-                self._handle_unknown_error(e)
                 raise e
 
         if self.ask_for_human_input:
@@ -177,6 +191,12 @@ class CrewAgentExecutor(CrewAgentExecutorMixin):
 
     def _handle_unknown_error(self, exception: Exception) -> None:
         """Handle unknown errors by informing the user."""
+        event_bus.emit(
+            self,
+            event=AgentExecutionError(
+                agent=self.agent, task=self.task, error=str(exception)
+            ),
+        )
         self._printer.print(
             content="An unknown error occurred. Please check the details below.",
             color="red",

src/crewai/task.py

@@ -430,23 +430,23 @@ class Task(BaseModel):
             if self.callback:
                 self.callback(self.output)
 
-        crew = self.agent.crew  # type: ignore[union-attr]
-        if crew and crew.task_callback and crew.task_callback != self.callback:
-            crew.task_callback(self.output)
+            crew = self.agent.crew  # type: ignore[union-attr]
+            if crew and crew.task_callback and crew.task_callback != self.callback:
+                crew.task_callback(self.output)
 
-        if self._execution_span:
-            self._telemetry.task_ended(self._execution_span, self, agent.crew)
-            self._execution_span = None
+            if self._execution_span:
+                self._telemetry.task_ended(self._execution_span, self, agent.crew)
+                self._execution_span = None
 
-            if self.output_file:
-                content = (
-                    json_output
-                    if json_output
-                    else pydantic_output.model_dump_json()
-                    if pydantic_output
-                    else result
-                )
-                self._save_file(content)
+                if self.output_file:
+                    content = (
+                        json_output
+                        if json_output
+                        else pydantic_output.model_dump_json()
+                        if pydantic_output
+                        else result
+                    )
+                    self._save_file(content)
             event_bus.emit(self, TaskCompleted(task=self, output=task_output))
             return task_output
         except Exception as e:
@@ -732,10 +732,9 @@ class Task(BaseModel):
                     file.write(str(result))
         except (OSError, IOError) as e:
             raise RuntimeError(
-                "\n".join([
-                    f"Failed to save output file: {e}",
-                    FILEWRITER_RECOMMENDATION
-                ])
+                "\n".join(
+                    [f"Failed to save output file: {e}", FILEWRITER_RECOMMENDATION]
+                )
             )
         return None
 

tests/utilities/test_events.py

@@ -190,7 +190,7 @@ def test_agent_emits_execution_started_and_completed_events():
         "ask_for_human_input": False,
         "input": "Just say hi\n"
         "\n"
-        "This is the expect criteria for your final answer: hi\n"
+        "This is the expected criteria for your final answer: hi\n"
         "you MUST return the actual complete content as the final answer, not a "
         "summary.",
         "tool_names": "",