[BREAKING] Python: Move single-config fluent methods to constructor parameters (#3693)

* Move single-config fluent methods to constructor parameters

* Updates

* Adjust magentic and group chat

python/samples/getting_started/workflows/_start-here/step1_executors_and_edges.py

@@ -160,10 +160,10 @@ async def main():
     upper_case = UpperCase(id="upper_case_executor")
 
     # Build the workflow using a fluent pattern:
-    # 1) add_edge(from_node, to_node) defines a directed edge upper_case -> reverse_text
-    # 2) set_start_executor(node) declares the entry point
+    # 1) start_executor=... in constructor declares the entry point
+    # 2) add_edge(from_node, to_node) defines a directed edge upper_case -> reverse_text
     # 3) build() finalizes and returns an immutable Workflow object
-    workflow1 = WorkflowBuilder().add_edge(upper_case, reverse_text).set_start_executor(upper_case).build()
+    workflow1 = WorkflowBuilder(start_executor=upper_case).add_edge(upper_case, reverse_text).build()
 
     # Run the workflow by sending the initial message to the start node.
     # The run(...) call returns an event collection; its get_outputs() method
@@ -181,10 +181,9 @@ async def main():
     # exclamation_adder uses @handler(input=str, output=str) to
     # explicitly declare types instead of relying on introspection.
     workflow2 = (
-        WorkflowBuilder()
+        WorkflowBuilder(start_executor=upper_case)
         .add_edge(upper_case, exclamation_adder)
         .add_edge(exclamation_adder, reverse_text)
-        .set_start_executor(upper_case)
         .build()
     )
 

python/samples/getting_started/workflows/_start-here/step2_agents_in_a_workflow.py

@@ -45,8 +45,8 @@ async def main():
     )
 
     # Build the workflow using the fluent builder.
-    # Set the start node and connect an edge from writer to reviewer.
-    workflow = WorkflowBuilder().set_start_executor(writer_agent).add_edge(writer_agent, reviewer_agent).build()
+    # Set the start node via constructor and connect an edge from writer to reviewer.
+    workflow = WorkflowBuilder(start_executor=writer_agent).add_edge(writer_agent, reviewer_agent).build()
 
     # Run the workflow with the user's initial message.
     # For foundational clarity, use run (non streaming) and print the terminal event.

python/samples/getting_started/workflows/_start-here/step3_streaming.py

@@ -44,8 +44,8 @@ async def main():
     )
 
     # Build the workflow using the fluent builder.
-    # Set the start node and connect an edge from writer to reviewer.
-    workflow = WorkflowBuilder().set_start_executor(writer_agent).add_edge(writer_agent, reviewer_agent).build()
+    # Set the start node via constructor and connect an edge from writer to reviewer.
+    workflow = WorkflowBuilder(start_executor=writer_agent).add_edge(writer_agent, reviewer_agent).build()
 
     # Track the last author to format streaming output.
     last_author: str | None = None

python/samples/getting_started/workflows/_start-here/step4_using_factories.py

@@ -73,12 +73,11 @@ async def main():
     # 4) set_start_executor(node) declares the entry point
     # 5) build() finalizes and returns an immutable Workflow object
     workflow = (
-        WorkflowBuilder()
+        WorkflowBuilder(start_executor="UpperCase")
         .register_executor(lambda: UpperCase(id="upper_case_executor"), name="UpperCase")
         .register_executor(lambda: reverse_text, name="ReverseText")
         .register_agent(create_agent, name="DecoderAgent")
         .add_chain(["UpperCase", "ReverseText", "DecoderAgent"])
-        .set_start_executor("UpperCase")
         .build()
     )