From 9d4263f93e59afad58e0bd348bcf0688185f2b65 Mon Sep 17 00:00:00 2001
From: jmaeagle99 <44687433+jmaeagle99@users.noreply.github.com>
Date: Thu, 21 May 2026 13:44:49 -0700
Subject: [PATCH] fix(external-storage): correct the reference check

---
 external_storage/handler.py | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/external_storage/handler.py b/external_storage/handler.py
index 0e1ea5ac..1ba8035a 100644
--- a/external_storage/handler.py
+++ b/external_storage/handler.py
@@ -22,17 +22,20 @@
 from aiohttp import web
 from google.protobuf import json_format
 from temporalio.api.common.v1 import Payload, Payloads
+from temporalio.api.sdk.v1 import ExternalStorageReference
 from temporalio.converter import ExternalStorage, PayloadCodec
 
+_REFERENCE_MESSAGE_TYPE = ExternalStorageReference.DESCRIPTOR.full_name.encode()
 
-def _is_storage_reference(payload: Payload) -> bool:
-    """A payload is an external-storage reference iff it carries external_payloads metadata.
 
-    When the SDK offloads a payload to external storage it replaces the
-    in-band bytes with a small protobuf "claim check" — the ``external_payloads``
-    repeated field is the marker the SDK uses to recognize it on the way back.
+def _is_storage_reference(payload: Payload) -> bool:
+    """A payload is an external-storage reference iff its metadata identifies
+    it as a serialized :class:`ExternalStorageReference` claim check.
     """
-    return len(payload.external_payloads) > 0
+    return (
+        payload.metadata.get("encoding") == b"json/protobuf"
+        and payload.metadata.get("messageType") == _REFERENCE_MESSAGE_TYPE
+    )
 
 
 def payload_routes(