diff --git a/semconv/registry/model/attributes-bare.yaml b/semconv/registry/model/attributes-bare.yaml
index 9db2eed..6e4bcde 100644
--- a/semconv/registry/model/attributes-bare.yaml
+++ b/semconv/registry/model/attributes-bare.yaml
@@ -195,6 +195,12 @@ groups:
     brief: Examined on log, written by order.
     examples:
     - 1
+  - id: failure_reason
+    type: string
+    stability: development
+    brief: Why a Temporal activity execution failed, on the SDK's activity failure counter (SDK >= 1.49).
+    examples:
+    - ActivityError
   - id: found
     type: boolean
     stability: development
diff --git a/semconv/registry/model/metrics-vendor.yaml b/semconv/registry/model/metrics-vendor.yaml
index a51d006..b1cc1ad 100644
--- a/semconv/registry/model/metrics-vendor.yaml
+++ b/semconv/registry/model/metrics-vendor.yaml
@@ -180,6 +180,7 @@ groups:
   attributes:
   - ref: activity_type
   - ref: client_name
+  - ref: failure_reason
   - ref: namespace
   - ref: task_queue
   - ref: worker_type