diff --git a/miles/rollout/generate_utils/openai_endpoint_utils.py b/miles/rollout/generate_utils/openai_endpoint_utils.py
index 645742afb37..f1cb76f1565 100644
--- a/miles/rollout/generate_utils/openai_endpoint_utils.py
+++ b/miles/rollout/generate_utils/openai_endpoint_utils.py
@@ -7,7 +7,7 @@
 import logging
 import random
 from argparse import Namespace
-from copy import deepcopy
+from copy import copy, deepcopy
 from typing import Any
 
 import httpx
@@ -743,7 +743,10 @@ def _compute_sample_from_openai_record(
     output_token_ids = [item[1] for item in choice["meta_info"]["output_token_logprobs"]]
     output_log_probs = [item[0] for item in choice["meta_info"]["output_token_logprobs"]]
 
-    sample = deepcopy(input_sample)
+    sample = copy(input_sample)
+    sample.metadata = dict(input_sample.metadata)
+    sample.weight_versions = list(input_sample.weight_versions)
+    sample.prefix_cache_info = deepcopy(input_sample.prefix_cache_info)
     request_input_ids = record.request.get("input_ids")
     if request_input_ids is not None:
         assert (
diff --git a/miles/rollout/generate_utils/sample_utils.py b/miles/rollout/generate_utils/sample_utils.py
index b909551e564..5844f09b91b 100644
--- a/miles/rollout/generate_utils/sample_utils.py
+++ b/miles/rollout/generate_utils/sample_utils.py
@@ -1,4 +1,4 @@
-from copy import deepcopy
+from copy import copy
 from dataclasses import fields
 
 from miles.utils.types import Sample
@@ -30,7 +30,7 @@ def merge_samples(samples: list[Sample], tokenizer) -> Sample:
 
 def _merge_sample_pair(a: Sample, b: Sample, tokenizer) -> Sample:
     """Merge two samples generated from sibling inference engine calls."""
-    a, b = deepcopy(a), deepcopy(b)
+    a, b = copy(a), copy(b)
 
     def _merge_equal_value(field):
         x = getattr(a, field)