From 2973ff8be958961bb0a8f8db154fac30b3ab5e88 Mon Sep 17 00:00:00 2001
From: Alexsander Hamir <alexsanderhamirgomesbaptista@gmail.com>
Date: Fri, 26 Sep 2025 13:25:59 -0700
Subject: [PATCH] fix: remove slow string operation (#14955)

* fix: remove slow string operation

* fix: behavior change

* fix: behavior change

* fix: avoid default call
---
 litellm/litellm_core_utils/rules.py |  5 +++++
 litellm/utils.py                    | 17 +++++++++++------
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/litellm/litellm_core_utils/rules.py b/litellm/litellm_core_utils/rules.py
index beeb012d032..717ff55ab22 100644
--- a/litellm/litellm_core_utils/rules.py
+++ b/litellm/litellm_core_utils/rules.py
@@ -23,6 +23,11 @@ class Rules:
     def __init__(self) -> None:
         pass
 
+    @staticmethod
+    def has_pre_call_rules() -> bool:
+        """Check if any pre-call rules are configured"""
+        return len(litellm.pre_call_rules) > 0
+
     def pre_call_rules(self, input: str, model: str):
         for rule in litellm.pre_call_rules:
             if callable(rule):
diff --git a/litellm/utils.py b/litellm/utils.py
index 0721b023d2b..cb340735b4e 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -7,6 +7,7 @@
 #
 #  Thank you users! We ❤️ you! - Krrish & Ishaan
 
+from io import StringIO
 import ast
 import asyncio
 import base64
@@ -724,17 +725,21 @@ def function_setup(  # noqa: PLR0915
                 messages = kwargs["messages"]
             ### PRE-CALL RULES ###
             if (
-                isinstance(messages, list)
+                Rules.has_pre_call_rules()
+                and isinstance(messages, list)
                 and len(messages) > 0
                 and isinstance(messages[0], dict)
                 and "content" in messages[0]
             ):
+
+                buffer = StringIO()
+                for m in messages:
+                    content = m.get("content", "")
+                    if content is not None and isinstance(content, str):
+                        buffer.write(content)
+
                 rules_obj.pre_call_rules(
-                    input="".join(
-                        m.get("content", "")
-                        for m in messages
-                        if "content" in m and isinstance(m["content"], str)
-                    ),
+                    input=buffer.getvalue(),
                     model=model,
                 )
         elif (