From 105b45967add1d5713340405bc9e3d2ffbff6612 Mon Sep 17 00:00:00 2001
From: PRABHU KIRAN VANDRANKI <72809214+VANDRANKI@users.noreply.github.com>
Date: Tue, 19 May 2026 18:21:06 -0400
Subject: [PATCH] fix: avoid mutating caller fallback dicts in
 async_completion_with_fallbacks

---
 litellm/litellm_core_utils/fallback_utils.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/litellm/litellm_core_utils/fallback_utils.py b/litellm/litellm_core_utils/fallback_utils.py
index 52eb35663bd..fefc143ef3a 100644
--- a/litellm/litellm_core_utils/fallback_utils.py
+++ b/litellm/litellm_core_utils/fallback_utils.py
@@ -47,8 +47,9 @@ async def async_completion_with_fallbacks(**kwargs):
             completion_kwargs = safe_deep_copy(base_kwargs)
             # Handle dictionary fallback configurations
             if isinstance(fallback, dict):
-                model = fallback.pop("model", original_model)
-                completion_kwargs.update(fallback)
+                fallback_copy = dict(fallback)  # avoid mutating caller's dict
+                model = fallback_copy.pop("model", original_model)
+                completion_kwargs.update(fallback_copy)
             else:
                 model = fallback