fix otel tests

Author: AbhiPrasad

py/src/braintrust/otel/__init__.py

@@ -74,6 +74,11 @@ def on_start(self, span, parent_context=None):
         """Forward span start events to the inner processor."""
         self._processor.on_start(span, parent_context)
 
+    def _on_ending(self, span):
+        """Called by the OTel SDK before on_end. Forward to inner processor if it supports it."""
+        if hasattr(self._processor, "_on_ending"):
+            self._processor._on_ending(span)
+
     def on_end(self, span):
         """Apply filtering logic and conditionally forward span end events."""
         if self._should_keep_filtered_span(span):
@@ -318,6 +323,11 @@ def _get_parent_otel_braintrust_parent(self, parent_context):
         except Exception:
             return None
 
+    def _on_ending(self, span):
+        """Called by the OTel SDK before on_end. Forward to inner processor if it supports it."""
+        if hasattr(self._processor, "_on_ending"):
+            self._processor._on_ending(span)
+
     def on_end(self, span):
         """Forward span end events to the inner processor."""
         self._processor.on_end(span)

py/src/braintrust/wrappers/_anthropic_utils.py

@@ -85,6 +85,9 @@ def finalize_anthropic_tokens(metrics: dict[str, float]) -> dict[str, float]:
     Returns:
         Updated metrics with total prompt tokens and total tokens fields
     """
+    if not metrics:
+        return metrics
+
     total_prompt_tokens = (
         metrics.get("prompt_tokens", 0)
         + metrics.get("prompt_cached_tokens", 0)