From 5ceaddd0b9f3fd0e5be83f453c8bddae0868ac82 Mon Sep 17 00:00:00 2001
From: "moyai-berriai[bot]"
 <336287033+moyai-berriai[bot]@users.noreply.github.com>
Date: Tue, 20 Oct 2026 15:07:31 +0000
Subject: [PATCH] fix(cache): enforce byte-size limits for cached strings

---
 litellm/caching/in_memory_cache.py         |  5 ++---
 tests/unit/caching/test_in_memory_cache.py | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/litellm/caching/in_memory_cache.py b/litellm/caching/in_memory_cache.py
index cb6426f64ff..a9af7237141 100644
--- a/litellm/caching/in_memory_cache.py
+++ b/litellm/caching/in_memory_cache.py
@@ -62,13 +62,12 @@ class InMemoryCache(BaseCache):
         try:
             # Fast path for common primitive types that are typically small
             if (
-                isinstance(value, (bool, int, float, str))
+                isinstance(value, (bool, int, float))
                 and len(str(value)) < self.max_size_per_item * MAX_SIZE_PER_ITEM_IN_MEMORY_CACHE_IN_KB
             ):  # Conservative estimate
                 return True
 
-            # Direct size check for bytes objects
-            if isinstance(value, bytes):
+            if isinstance(value, (str, bytes)):
                 return sys.getsizeof(value) / 1024 <= self.max_size_per_item
 
             # Handle special types without full conversion when possible
diff --git a/tests/unit/caching/test_in_memory_cache.py b/tests/unit/caching/test_in_memory_cache.py
index 214f4ecf301..48d9229499c 100644
--- a/tests/unit/caching/test_in_memory_cache.py
+++ b/tests/unit/caching/test_in_memory_cache.py
@@ -76,6 +76,28 @@ def test_in_memory_cache_max_size_per_item():
     assert result is False
 
 
+@pytest.mark.parametrize(
+    ("character", "count", "should_cache"),
+    [
+        ("a", 100, True),
+        ("\u00e9", 100, True),
+        ("\u6f22", 100, True),
+        ("\U0001f600", 100, True),
+        ("a", 1023, False),
+        ("\u00e9", 1023, False),
+        ("\u6f22", 600, False),
+        ("\U0001f600", 300, False),
+    ],
+)
+def test_string_cache_admission_respects_byte_size(character: str, count: int, should_cache: bool) -> None:
+    cache: Final = InMemoryCache(max_size_per_item=1, clock=lambda: 1000.0)
+    value: Final = character * count
+
+    cache.set_cache("text", value)
+
+    assert cache.get_cache("text") == (value if should_cache else None)
+
+
 def test_in_memory_cache_ttl():
     """
     Check that