fix: Update hello world test client to match sdk behavior. Also down-level required python version

examples/helloworld/pyproject.toml

@@ -3,7 +3,7 @@ name = "helloworld"
 version = "0.1.0"
 description = "HelloWorld agent example that only returns Messages"
 readme = "README.md"
-requires-python = ">=3.13"
+requires-python = ">=3.12"
 dependencies = [
     "a2a-sdk",
     "click>=8.1.8",

examples/helloworld/test_client.py

@@ -59,7 +59,7 @@ async def main() -> None:
             logger.error(f"Critical error fetching public agent card: {e}", exc_info=True)
             raise RuntimeError("Failed to fetch the public agent card. Cannot continue.") from e
 
-       
+
         client = A2AClient(
             httpx_client=httpx_client, agent_card=final_agent_card_to_use
         )
@@ -80,14 +80,19 @@ async def main() -> None:
 
         response = await client.send_message(request)
         print(response.model_dump(mode='json', exclude_none=True))
-
-        streaming_request = SendStreamingMessageRequest(
-            params=MessageSendParams(**send_message_payload)
-        )
-
-        stream_response = client.send_message_streaming(streaming_request)
-        async for chunk in stream_response:
-            print(chunk.model_dump(mode='json', exclude_none=True))
+        # The HelloWorld agent doesn't support streaming requests. Validate
+        # this throws an error.
+        try:
+            streaming_request = SendStreamingMessageRequest(
+                params=MessageSendParams(**send_message_payload)
+            )
+
+            stream_response = client.send_message_streaming(streaming_request)
+            print("Got an unexpected response:")
+            async for chunk in stream_response:
+                print(chunk.model_dump(mode='json', exclude_none=True))
+        except Exception:
+          pass
 
 
 if __name__ == '__main__':

examples/langgraph/pyproject.toml

@@ -3,7 +3,7 @@ name = "langgraph-example"
 version = "0.1.0"
 description = "Currency conversion agent example"
 readme = "README.md"
-requires-python = ">=3.13"
+requires-python = ">=3.12"
 dependencies = [
     "a2a-sdk",
     "click>=8.1.8",