Better support async flows (#2193)

* Better support async

* Drop coroutine

src/crewai/flow/flow.py

@@ -713,16 +713,35 @@ class Flow(Generic[T], metaclass=FlowMeta):
             raise TypeError(f"State must be dict or BaseModel, got {type(self._state)}")
 
     def kickoff(self, inputs: Optional[Dict[str, Any]] = None) -> Any:
-        """Start the flow execution.
+        """
+        Start the flow execution in a synchronous context.
+
+        This method wraps kickoff_async so that all state initialization and event
+        emission is handled in the asynchronous method.
+        """
+
+        async def run_flow():
+            return await self.kickoff_async(inputs)
+
+        return asyncio.run(run_flow())
+
+    @init_flow_main_trace
+    async def kickoff_async(self, inputs: Optional[Dict[str, Any]] = None) -> Any:
+        """
+        Start the flow execution asynchronously.
+
+        This method performs state restoration (if an 'id' is provided and persistence is available)
+        and updates the flow state with any additional inputs. It then emits the FlowStartedEvent,
+        logs the flow startup, and executes all start methods. Once completed, it emits the
+        FlowFinishedEvent and returns the final output.
 
         Args:
-            inputs: Optional dictionary containing input values and potentially a state ID to restore
-        """
-        # Handle state restoration if ID is provided in inputs
-        if inputs and "id" in inputs and self._persistence is not None:
-            restore_uuid = inputs["id"]
-            stored_state = self._persistence.load_state(restore_uuid)
+            inputs: Optional dictionary containing input values and/or a state ID for restoration.
 
+        Returns:
+            The final output from the flow, which is the result of the last executed method.
+        """
+        if inputs:
             # Override the id in the state if it exists in inputs
             if "id" in inputs:
                 if isinstance(self._state, dict):
@@ -730,24 +749,27 @@ class Flow(Generic[T], metaclass=FlowMeta):
                 elif isinstance(self._state, BaseModel):
                     setattr(self._state, "id", inputs["id"])
 
-            if stored_state:
-                self._log_flow_event(
-                    f"Loading flow state from memory for UUID: {restore_uuid}",
-                    color="yellow",
-                )
-                # Restore the state
-                self._restore_state(stored_state)
-            else:
-                self._log_flow_event(
-                    f"No flow state found for UUID: {restore_uuid}", color="red"
-                )
+            # If persistence is enabled, attempt to restore the stored state using the provided id.
+            if "id" in inputs and self._persistence is not None:
+                restore_uuid = inputs["id"]
+                stored_state = self._persistence.load_state(restore_uuid)
+                if stored_state:
+                    self._log_flow_event(
+                        f"Loading flow state from memory for UUID: {restore_uuid}",
+                        color="yellow",
+                    )
+                    self._restore_state(stored_state)
+                else:
+                    self._log_flow_event(
+                        f"No flow state found for UUID: {restore_uuid}", color="red"
+                    )
 
-            # Apply any additional inputs after restoration
+            # Update state with any additional inputs (ignoring the 'id' key)
             filtered_inputs = {k: v for k, v in inputs.items() if k != "id"}
             if filtered_inputs:
                 self._initialize_state(filtered_inputs)
 
-        # Start flow execution
+        # Emit FlowStartedEvent and log the start of the flow.
         crewai_event_bus.emit(
             self,
             FlowStartedEvent(
@@ -760,27 +782,18 @@ class Flow(Generic[T], metaclass=FlowMeta):
             f"Flow started with ID: {self.flow_id}", color="bold_magenta"
         )
 
-        if inputs is not None and "id" not in inputs:
-            self._initialize_state(inputs)
-
-        async def run_flow():
-            return await self.kickoff_async()
-
-        return asyncio.run(run_flow())
-
-    @init_flow_main_trace
-    async def kickoff_async(self, inputs: Optional[Dict[str, Any]] = None) -> Any:
         if not self._start_methods:
             raise ValueError("No start method defined")
 
+        # Execute all start methods concurrently.
         tasks = [
             self._execute_start_method(start_method)
             for start_method in self._start_methods
         ]
         await asyncio.gather(*tasks)
-
         final_output = self._method_outputs[-1] if self._method_outputs else None
 
+        # Emit FlowFinishedEvent after all processing is complete.
         crewai_event_bus.emit(
             self,
             FlowFinishedEvent(