[BREAKING] Python: Add factory pattern to GroupChat and Magentic

python/packages/core/agent_framework/_workflows/_concurrent.py

@@ -292,9 +292,7 @@ class MyCustomExecutor(Executor): ...
             wf2 = ConcurrentBuilder().register_participants([create_researcher, MyCustomExecutor]).build()
         """
         if self._participants:
-            raise ValueError(
-                "Cannot mix .participants([...]) and .register_participants() in the same builder instance."
-            )
+            raise ValueError("Cannot mix .participants() and .register_participants() in the same builder instance.")
 
         if self._participant_factories:
             raise ValueError("register_participants() has already been called on this builder instance.")
@@ -330,9 +328,7 @@ def participants(self, participants: Sequence[AgentProtocol | Executor]) -> "Con
             wf2 = ConcurrentBuilder().participants([researcher_agent, my_custom_executor]).build()
         """
         if self._participant_factories:
-            raise ValueError(
-                "Cannot mix .participants([...]) and .register_participants() in the same builder instance."
-            )
+            raise ValueError("Cannot mix .participants() and .register_participants() in the same builder instance.")
 
         if self._participants:
             raise ValueError("participants() has already been called on this builder instance.")
@@ -498,6 +494,10 @@ def with_request_info(
 
     def _resolve_participants(self) -> list[Executor]:
         """Resolve participant instances into Executor objects."""
+        if not self._participants and not self._participant_factories:
+            raise ValueError("No participants provided. Call .participants() or .register_participants() first.")
+        # We don't need to check if both are set since that is handled in the respective methods
+
         participants: list[Executor | AgentProtocol] = []
         if self._participant_factories:
             # Resolve the participant factories now. This doesn't break the factory pattern
@@ -549,11 +549,6 @@ def build(self) -> Workflow:
 
             workflow = ConcurrentBuilder().participants([agent1, agent2]).build()
         """
-        if not self._participants and not self._participant_factories:
-            raise ValueError(
-                "No participants provided. Call .participants([...]) or .register_participants([...]) first."
-            )
-
         # Internal nodes
         dispatcher = _DispatchToAllParticipants(id="dispatcher")
         aggregator = (

python/packages/core/agent_framework/_workflows/_handoff.py

@@ -603,7 +603,7 @@ def __init__(
         self._participant_factories: dict[str, Callable[[], AgentProtocol]] = {}
         self._start_id: str | None = None
         if participant_factories:
-            self.participant_factories(participant_factories)
+            self.register_participants(participant_factories)
 
         if participants:
             self.participants(participants)
@@ -623,7 +623,7 @@ def __init__(
         # Termination related members
         self._termination_condition: Callable[[list[ChatMessage]], bool | Awaitable[bool]] | None = None
 
-    def participant_factories(
+    def register_participants(
         self, participant_factories: Mapping[str, Callable[[], AgentProtocol]]
     ) -> "HandoffBuilder":
         """Register factories that produce agents for the handoff workflow.
@@ -641,7 +641,7 @@ def participant_factories(
             Self for method chaining.
 
         Raises:
-            ValueError: If participant_factories is empty or `.participants(...)`  or `.participant_factories(...)`
+            ValueError: If participant_factories is empty or `.participants(...)`  or `.register_participants(...)`
                         has already been called.
 
         Example:
@@ -670,17 +670,14 @@ def create_billing_agent() -> ChatAgent:
 
             # Handoff will be created automatically unless specified otherwise
             # The default creates a mesh topology where all agents can handoff to all others
-            builder = HandoffBuilder().participant_factories(factories)
+            builder = HandoffBuilder().register_participants(factories)
             builder.with_start_agent("triage")
         """
         if self._participants:
-            raise ValueError(
-                "Cannot mix .participants([...]) and .participant_factories() in the same builder instance."
-            )
+            raise ValueError("Cannot mix .participants() and .register_participants() in the same builder instance.")
 
         if self._participant_factories:
-            raise ValueError("participant_factories() has already been called on this builder instance.")
-
+            raise ValueError("register_participants() has already been called on this builder instance.")
         if not participant_factories:
             raise ValueError("participant_factories cannot be empty")
 
@@ -698,8 +695,8 @@ def participants(self, participants: Sequence[AgentProtocol]) -> "HandoffBuilder
             Self for method chaining.
 
         Raises:
-            ValueError: If participants is empty, contains duplicates, or `.participants(...)` or
-                        `.participant_factories(...)` has already been called.
+            ValueError: If participants is empty, contains duplicates, or `.participants()` or
+                        `.register_participants()` has already been called.
             TypeError: If participants are not AgentProtocol instances.
 
         Example:
@@ -718,9 +715,7 @@ def participants(self, participants: Sequence[AgentProtocol]) -> "HandoffBuilder
             builder.with_start_agent(triage)
         """
         if self._participant_factories:
-            raise ValueError(
-                "Cannot mix .participants([...]) and .participant_factories() in the same builder instance."
-            )
+            raise ValueError("Cannot mix .participants() and .register_participants() in the same builder instance.")
 
         if self._participants:
             raise ValueError("participants have already been assigned")
@@ -900,7 +895,7 @@ def with_start_agent(self, agent: str | AgentProtocol) -> "HandoffBuilder":
                 if agent not in self._participant_factories:
                     raise ValueError(f"Start agent factory name '{agent}' is not in the participant_factories list")
             else:
-                raise ValueError("Call participant_factories(...) before with_start_agent(...)")
+                raise ValueError("Call register_participants(...) before with_start_agent(...)")
             self._start_id = agent
         elif isinstance(agent, AgentProtocol):
             resolved_id = self._resolve_to_id(agent)
@@ -1043,15 +1038,6 @@ def build(self) -> Workflow:
             ValueError: If participants or coordinator were not configured, or if
                        required configuration is invalid.
         """
-        if not self._participants and not self._participant_factories:
-            raise ValueError(
-                "No participants or participant_factories have been configured. "
-                "Call participants(...) or participant_factories(...) first."
-            )
-
-        if self._start_id is None:
-            raise ValueError("Must call with_start_agent(...) before building the workflow.")
-
         # Resolve agents (either from instances or factories)
         # The returned map keys are either executor IDs or factory names, which is need to resolve handoff configs
         resolved_agents = self._resolve_agents()
@@ -1062,6 +1048,8 @@ def build(self) -> Workflow:
         executors = self._resolve_executors(resolved_agents, resolved_handoffs)
 
         # Build the workflow graph
+        if self._start_id is None:
+            raise ValueError("Must call with_start_agent(...) before building the workflow.")
         start_executor = executors[self._resolve_to_id(resolved_agents[self._start_id])]
         builder = WorkflowBuilder(
             name=self._name,
@@ -1100,8 +1088,9 @@ def _resolve_agents(self) -> dict[str, AgentProtocol]:
         Returns:
             Map of executor IDs or factory names to `AgentProtocol` instances
         """
-        if self._participants and self._participant_factories:
-            raise ValueError("Cannot have both executors and participant_factories configured")
+        if not self._participants and not self._participant_factories:
+            raise ValueError("No participants provided. Call .participants() or .register_participants() first.")
+        # We don't need to check if both are set since that is handled in the respective methods
 
         if self._participants:
             return self._participants