fix: Type create_tracker as Optional to fix mypy errors

Change AgentGraphDefinition.create_tracker from
Callable[[], AIGraphTracker] with default lambda: None to
Optional[Callable[[], AIGraphTracker]] with default None. Guard
call sites in both runners with `is not None` before invoking.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jsonbailey

packages/ai-providers/server-ai-langchain/src/ldai_langchain/langgraph_agent_graph_runner.py

@@ -260,7 +260,7 @@ def route(state: WorkflowState) -> str:
 
         self._graph.traverse(fn=handle_traversal)
 
-        tracker = self._graph.create_tracker()
+        tracker = self._graph.create_tracker() if self._graph.create_tracker is not None else None
         graph_key_str = tracker.graph_key if tracker else 'unknown'
         log.debug(
             f"LangGraphAgentGraphRunner: graph='{graph_key_str}', root='{root_key}', "
@@ -281,7 +281,7 @@ async def run(self, input: Any) -> AgentGraphResult:
         :param input: The string prompt to send to the agent graph
         :return: AgentGraphResult with the final output and metrics
         """
-        tracker = self._graph.create_tracker()
+        tracker = self._graph.create_tracker() if self._graph.create_tracker is not None else None
         start_ns = time.perf_counter_ns()
 
         try:

packages/ai-providers/server-ai-openai/src/ldai_openai/openai_agent_graph_runner.py

@@ -70,7 +70,7 @@ async def run(self, input: Any) -> AgentGraphResult:
         :param input: The string prompt to send to the agent graph
         :return: AgentGraphResult with the final output and metrics
         """
-        tracker = self._graph.create_tracker()
+        tracker = self._graph.create_tracker() if self._graph.create_tracker is not None else None
         path: List[str] = []
         root_node = self._graph.root()
         root_key = root_node.get_key() if root_node else ''

packages/sdk/server-ai/src/ldai/agent_graph/__init__.py

@@ -54,7 +54,7 @@ def __init__(
         nodes: Dict[str, AgentGraphNode],
         context: Context,
         enabled: bool,
-        create_tracker: Callable[[], AIGraphTracker] = lambda: None,
+        create_tracker: Optional[Callable[[], AIGraphTracker]] = None,
     ):
         self._agent_graph = agent_graph
         self._context = context