From 3ed3b861fa495fc32bffef989c05eea9075b2b3b Mon Sep 17 00:00:00 2001
From: yryzhan <yryzhan@users.noreply.github.com>
Date: Wed, 20 May 2026 15:25:25 +0200
Subject: [PATCH] fix(core): snapshot dict in safe_json_dumps to prevent
 concurrent mutation crash

_serialize iterates obj.items() directly, which raises RuntimeError
if another thread mutates the dict concurrently. Snapshot via
list(obj.items()) eliminates the race.
---
 litellm/litellm_core_utils/safe_json_dumps.py |  2 +-
 .../test_safe_json_dumps.py                   | 30 +++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/litellm/litellm_core_utils/safe_json_dumps.py b/litellm/litellm_core_utils/safe_json_dumps.py
index 051aa2f27a5..afb6c018a2d 100644
--- a/litellm/litellm_core_utils/safe_json_dumps.py
+++ b/litellm/litellm_core_utils/safe_json_dumps.py
@@ -26,7 +26,7 @@ def safe_dumps(data: Any, max_depth: int = DEFAULT_MAX_RECURSE_DEPTH) -> str:
         result: Union[dict, list, tuple, set, str]
         if isinstance(obj, dict):
             result = {}
-            for k, v in obj.items():
+            for k, v in list(obj.items()):
                 if isinstance(k, (str)):
                     result[k] = _serialize(v, seen, depth + 1)
             seen.remove(id(obj))
diff --git a/tests/test_litellm/litellm_core_utils/test_safe_json_dumps.py b/tests/test_litellm/litellm_core_utils/test_safe_json_dumps.py
index c71a229cca5..26157e003f1 100644
--- a/tests/test_litellm/litellm_core_utils/test_safe_json_dumps.py
+++ b/tests/test_litellm/litellm_core_utils/test_safe_json_dumps.py
@@ -1,6 +1,7 @@
 import json
 import os
 import sys
+import threading
 
 import pytest
 
@@ -172,3 +173,32 @@ def test_pydantic_base_model():
     assert len(result["healthy_endpoints"]) == 2
     assert result["healthy_endpoints"][0]["name"] == "test"
     assert result["healthy_endpoints"][1] == {"value": 1, "label": "one"}
+
+
+def test_no_runtime_error_on_concurrent_dict_mutation():
+    """safe_dumps must not raise RuntimeError when another thread mutates the dict."""
+    data = {f"key_{i}": f"value_{i}" for i in range(200)}
+    barrier = threading.Barrier(2, timeout=5)
+    errors = []
+
+    def mutator():
+        barrier.wait()
+        for i in range(200, 400):
+            data[f"key_{i}"] = f"value_{i}"
+
+    def serializer():
+        barrier.wait()
+        try:
+            safe_dumps(data)
+        except RuntimeError as e:
+            if "dictionary changed size during iteration" in str(e):
+                errors.append(e)
+
+    t1 = threading.Thread(target=mutator)
+    t2 = threading.Thread(target=serializer)
+    t1.start()
+    t2.start()
+    t1.join(timeout=5)
+    t2.join(timeout=5)
+
+    assert not errors, "safe_dumps raised RuntimeError on concurrent mutation"