add gen_ai.usage span attributes from conversation response

ai_core_api_client/api/ai_api.py

@@ -26,6 +26,27 @@ from ai_core_api_client.api_response import ApiResponse
 from ai_core_api_client.rest import RESTResponseType
 
 
+def _record_usage_to_span(response) -> None:
+    """Record token usage from ai-core-api response as OTel span attributes."""
+    try:
+        usage = getattr(response, 'usage', None)
+        if usage is None:
+            return
+        from opentelemetry import trace
+        span = trace.get_current_span()
+        if not span.is_recording():
+            return
+        model = getattr(usage, 'model', None)
+        if model:
+            span.set_attribute("gen_ai.usage.model", model)
+        for attr in ('prompt_tokens', 'completion_tokens', 'total_tokens', 'cached_tokens'):
+            val = getattr(usage, attr, None)
+            if val is not None:
+                span.set_attribute(f"gen_ai.usage.{attr}", val)
+    except Exception:
+        pass
+
+
 class AiApi:
     """NOTE: This class is auto generated by OpenAPI Generator
     Ref: https://openapi-generator.tech
@@ -103,11 +124,15 @@ class AiApi:
             _request_timeout=_request_timeout
         )
         response_data.read()
-        return self.api_client.response_deserialize(
+        result = self.api_client.response_deserialize(
             response_data=response_data,
             response_types_map=_response_types_map,
         ).data
 
+        _record_usage_to_span(result)
+
+        return result
+
 
     @validate_call
     def conversation_post_with_http_info(