fix(python): persist usage_info on session create/resume and update v…

…ia events

python/copilot/client.py

@@ -504,6 +504,9 @@ async def create_session(self, config: Optional[SessionConfig] = None) -> Copilo
         session_id = response["sessionId"]
         workspace_path = response.get("workspacePath")
         session = CopilotSession(session_id, self._client, workspace_path)
+        usage_info = response.get("usageInfo")
+        if usage_info:
+            session.usage_info = usage_info
         session._register_tools(tools)
         if on_permission_request:
             session._register_permission_handler(on_permission_request)
@@ -634,7 +637,7 @@ async def resume_session(
         resumed_session_id = response["sessionId"]
         workspace_path = response.get("workspacePath")
         session = CopilotSession(resumed_session_id, self._client, workspace_path)
-        usage_info = response.get("usageInfo") or response.get("usage_info")
+        usage_info = response.get("usageInfo")
         if usage_info:
             session.usage_info = usage_info
         session._register_tools(cfg.get("tools"))

python/copilot/session.py

@@ -79,6 +79,7 @@ def __init__(self, session_id: str, client: Any, workspace_path: Optional[str] =
         self._user_input_handler_lock = threading.Lock()
         self._hooks: Optional[SessionHooks] = None
         self._hooks_lock = threading.Lock()
+        self.usage_info = None
 
     @property
     def workspace_path(self) -> Optional[str]:
@@ -232,6 +233,9 @@ def _dispatch_event(self, event: SessionEvent) -> None:
         Args:
             event: The session event to dispatch to all handlers.
         """
+        if hasattr(event, "usage_info") and event.usage_info:
+            self.usage_info = event.usage_info
+
         with self._event_handlers_lock:
             handlers = list(self._event_handlers)