From 8cb52ce0bbcae4d1e421796224543a4c118fa41f Mon Sep 17 00:00:00 2001
From: user <70670632+stuxf@users.noreply.github.com>
Date: Fri, 1 May 2026 22:15:03 -0700
Subject: [PATCH] fix(caching): handle stale isolated Redis semantic index

---
 litellm/caching/redis_semantic_cache.py       | 38 +++++++---
 .../caching/test_redis_semantic_cache.py      | 73 +++++++++++++++++++
 2 files changed, 102 insertions(+), 9 deletions(-)

diff --git a/litellm/caching/redis_semantic_cache.py b/litellm/caching/redis_semantic_cache.py
index 85d3a4f1b4..27538530bc 100644
--- a/litellm/caching/redis_semantic_cache.py
+++ b/litellm/caching/redis_semantic_cache.py
@@ -128,6 +128,9 @@ class RedisSemanticCache(BaseCache):
         redis_url: str,
         cache_vectorizer: Any,
     ) -> Any:
+        def _is_schema_mismatch(exc: ValueError) -> bool:
+            return "schema does not match" in str(exc)
+
         try:
             return semantic_cache_cls(
                 name=index_name,
@@ -138,7 +141,7 @@ class RedisSemanticCache(BaseCache):
                 overwrite=False,
             )
         except ValueError as exc:
-            if "schema does not match" not in str(exc):
+            if not _is_schema_mismatch(exc):
                 raise
 
             isolated_index_name = f"{index_name}_isolated"
@@ -146,14 +149,31 @@ class RedisSemanticCache(BaseCache):
                 "Redis semantic-cache existing index schema is not isolated; "
                 f"using isolated index - {isolated_index_name}"
             )
-            return semantic_cache_cls(
-                name=isolated_index_name,
-                redis_url=redis_url,
-                vectorizer=cache_vectorizer,
-                distance_threshold=self.distance_threshold,
-                filterable_fields=[self.CACHE_KEY_FILTERABLE_FIELD],
-                overwrite=False,
-            )
+            try:
+                return semantic_cache_cls(
+                    name=isolated_index_name,
+                    redis_url=redis_url,
+                    vectorizer=cache_vectorizer,
+                    distance_threshold=self.distance_threshold,
+                    filterable_fields=[self.CACHE_KEY_FILTERABLE_FIELD],
+                    overwrite=False,
+                )
+            except ValueError as isolated_exc:
+                if not _is_schema_mismatch(isolated_exc):
+                    raise
+
+                print_verbose(
+                    "Redis semantic-cache isolated index schema is stale; "
+                    f"recreating isolated index - {isolated_index_name}"
+                )
+                return semantic_cache_cls(
+                    name=isolated_index_name,
+                    redis_url=redis_url,
+                    vectorizer=cache_vectorizer,
+                    distance_threshold=self.distance_threshold,
+                    filterable_fields=[self.CACHE_KEY_FILTERABLE_FIELD],
+                    overwrite=True,
+                )
 
     def _get_cache_filters(self, key: str) -> Dict[str, str]:
         return {self.CACHE_KEY_FIELD_NAME: str(key)}
diff --git a/tests/test_litellm/caching/test_redis_semantic_cache.py b/tests/test_litellm/caching/test_redis_semantic_cache.py
index f5c84c9d3e..02b06bed62 100644
--- a/tests/test_litellm/caching/test_redis_semantic_cache.py
+++ b/tests/test_litellm/caching/test_redis_semantic_cache.py
@@ -232,6 +232,79 @@ def test_redis_semantic_cache_uses_isolated_index_for_old_schema(monkeypatch):
         ]
 
 
+def test_redis_semantic_cache_overwrites_stale_isolated_index(monkeypatch):
+    fallback_cache_mock = MagicMock()
+    semantic_cache_mock = MagicMock(
+        side_effect=[
+            ValueError("Existing index schema does not match"),
+            ValueError("Existing index schema does not match"),
+            fallback_cache_mock,
+        ]
+    )
+    custom_vectorizer_mock = MagicMock()
+
+    with patch.dict(
+        "sys.modules",
+        {
+            "redisvl.extensions.llmcache": MagicMock(SemanticCache=semantic_cache_mock),
+            "redisvl.utils.vectorize": MagicMock(
+                CustomTextVectorizer=custom_vectorizer_mock
+            ),
+        },
+    ):
+        from litellm.caching.redis_semantic_cache import RedisSemanticCache
+
+        monkeypatch.setenv("REDIS_HOST", "localhost")
+        monkeypatch.setenv("REDIS_PORT", "6379")
+        monkeypatch.setenv("REDIS_PASSWORD", "test_password")
+
+        redis_semantic_cache = RedisSemanticCache(
+            similarity_threshold=0.8,
+            index_name="existing_index",
+        )
+
+        assert redis_semantic_cache.llmcache is fallback_cache_mock
+        assert (
+            semantic_cache_mock.call_args_list[2].kwargs["name"]
+            == "existing_index_isolated"
+        )
+        assert semantic_cache_mock.call_args_list[2].kwargs["overwrite"] is True
+        assert semantic_cache_mock.call_args_list[2].kwargs["filterable_fields"] == [
+            RedisSemanticCache.CACHE_KEY_FILTERABLE_FIELD
+        ]
+
+
+def test_redis_semantic_cache_reraises_unexpected_isolated_index_error(monkeypatch):
+    semantic_cache_mock = MagicMock(
+        side_effect=[
+            ValueError("Existing index schema does not match"),
+            ValueError("connection failed"),
+        ]
+    )
+    custom_vectorizer_mock = MagicMock()
+
+    with patch.dict(
+        "sys.modules",
+        {
+            "redisvl.extensions.llmcache": MagicMock(SemanticCache=semantic_cache_mock),
+            "redisvl.utils.vectorize": MagicMock(
+                CustomTextVectorizer=custom_vectorizer_mock
+            ),
+        },
+    ):
+        from litellm.caching.redis_semantic_cache import RedisSemanticCache
+
+        monkeypatch.setenv("REDIS_HOST", "localhost")
+        monkeypatch.setenv("REDIS_PORT", "6379")
+        monkeypatch.setenv("REDIS_PASSWORD", "test_password")
+
+        with pytest.raises(ValueError, match="connection failed"):
+            RedisSemanticCache(
+                similarity_threshold=0.8,
+                index_name="existing_index",
+            )
+
+
 def test_redis_semantic_cache_reraises_unexpected_index_error():
     from litellm.caching.redis_semantic_cache import RedisSemanticCache