diff --git a/pageindex/agent.py b/pageindex/agent.py
index fd7508d..4ffce61 100644
--- a/pageindex/agent.py
+++ b/pageindex/agent.py
@@ -114,23 +114,29 @@ class QueryStream:
         from openai.types.responses import ResponseTextDeltaEvent
 
         streamed_run = Runner.run_streamed(self._agent, self._question)
-        async for event in streamed_run.stream_events():
-            if isinstance(event, RawResponsesStreamEvent):
-                if isinstance(event.data, ResponseTextDeltaEvent):
-                    yield QueryEvent(type="text_delta", data=event.data.delta)
-            elif isinstance(event, RunItemStreamEvent):
-                item = event.item
-                if item.type == "tool_call_item":
-                    raw = item.raw_item
-                    yield QueryEvent(type="tool_call", data={
-                        "name": raw.name, "args": getattr(raw, "arguments", "{}"),
-                    })
-                elif item.type == "tool_call_output_item":
-                    yield QueryEvent(type="tool_result", data=str(item.output))
-                elif item.type == "message_output_item":
-                    text = ItemHelpers.text_message_output(item)
-                    if text:
-                        yield QueryEvent(type="text_done", data=text)
+        # cancel() in finally: the SDK starts the run eagerly, and abandoning
+        # this generator (consumer breaks / client disconnects) would otherwise
+        # leave the agent loop running — and billing LLM calls — to completion.
+        try:
+            async for event in streamed_run.stream_events():
+                if isinstance(event, RawResponsesStreamEvent):
+                    if isinstance(event.data, ResponseTextDeltaEvent):
+                        yield QueryEvent(type="text_delta", data=event.data.delta)
+                elif isinstance(event, RunItemStreamEvent):
+                    item = event.item
+                    if item.type == "tool_call_item":
+                        raw = item.raw_item
+                        yield QueryEvent(type="tool_call", data={
+                            "name": raw.name, "args": getattr(raw, "arguments", "{}"),
+                        })
+                    elif item.type == "tool_call_output_item":
+                        yield QueryEvent(type="tool_result", data=str(item.output))
+                    elif item.type == "message_output_item":
+                        text = ItemHelpers.text_message_output(item)
+                        if text:
+                            yield QueryEvent(type="text_done", data=text)
+        finally:
+            streamed_run.cancel()
 
     def __aiter__(self):
         return self.stream_events()