fix redis version compat errors flagged

litellm/caching/redis_cache.py

@@ -94,6 +94,24 @@ def _get_call_stack_info(num_frames: int = 2) -> str:
         return "unknown"
 
 
+def _is_expire_nx_unsupported_error(error: Exception) -> bool:
+    """
+    Return True when EXPIRE ... NX is unsupported and we should fallback.
+
+    Compatibility cases:
+    - Older redis-py clients that do not accept `nx` -> TypeError
+    - Redis < 7 servers that reject `EXPIRE key ttl NX` -> ResponseError syntax/arity errors
+    """
+    if isinstance(error, TypeError):
+        return True
+
+    if error.__class__.__name__ != "ResponseError":
+        return False
+
+    error_message = str(error).lower()
+    return "syntax error" in error_message or "wrong number of arguments" in error_message
+
+
 class RedisCircuitBreaker:
     """
     Tracks Redis health for a RedisCache instance.
@@ -850,9 +868,12 @@ class RedisCache(BaseCache):
                     # hot increment path while preserving window semantics.
                     try:
                         await _redis_client.expire(key, _used_ttl, nx=True)
-                    except TypeError:
+                    except Exception as e:
+                        if not _is_expire_nx_unsupported_error(e):
+                            raise
                         # Backward-compatible fallback if the Redis client does
-                        # not support the "nx" kwarg on expire().
+                        # not support the "nx" kwarg on expire(), or if an
+                        # older Redis server rejects EXPIRE ... NX.
                         current_ttl = await _redis_client.ttl(key)
                         if current_ttl == -1:
                             await _redis_client.expire(key, _used_ttl)

tests/test_litellm/caching/test_redis_cache.py

@@ -163,6 +163,62 @@ async def test_redis_cache_async_increment_default_fallback_existing_ttl_skips_s
     mock_redis_instance.ttl.assert_awaited_once_with("rate_limit:window")
 
 
+@pytest.mark.asyncio
+async def test_redis_cache_async_increment_default_falls_back_on_redis6_expire_nx_syntax_error(
+    monkeypatch, redis_no_ping
+):
+    """If Redis server rejects EXPIRE ... NX, fallback to TTL-check + conditional EXPIRE."""
+    monkeypatch.setenv("REDIS_HOST", "https://my-test-host")
+    redis_cache = RedisCache()
+    mock_redis_instance = AsyncMock()
+    mock_redis_instance.__aenter__.return_value = mock_redis_instance
+    mock_redis_instance.__aexit__.return_value = None
+
+    class ResponseError(Exception):
+        pass
+
+    mock_redis_instance.expire.side_effect = [
+        ResponseError("ERR syntax error"),
+        True,
+    ]
+    mock_redis_instance.ttl.return_value = -1
+
+    with patch.object(
+        redis_cache, "init_async_client", return_value=mock_redis_instance
+    ):
+        await redis_cache.async_increment(key="rate_limit:window", value=1)
+
+    assert mock_redis_instance.expire.await_count == 2
+    assert mock_redis_instance.expire.await_args_list[0].kwargs == {"nx": True}
+    assert mock_redis_instance.expire.await_args_list[1].kwargs == {}
+    mock_redis_instance.ttl.assert_awaited_once_with("rate_limit:window")
+
+
+@pytest.mark.asyncio
+async def test_redis_cache_async_increment_default_raises_non_compat_expire_error(
+    monkeypatch, redis_no_ping
+):
+    """Non-compatibility expire errors should still propagate."""
+    monkeypatch.setenv("REDIS_HOST", "https://my-test-host")
+    redis_cache = RedisCache()
+    mock_redis_instance = AsyncMock()
+    mock_redis_instance.__aenter__.return_value = mock_redis_instance
+    mock_redis_instance.__aexit__.return_value = None
+
+    class ResponseError(Exception):
+        pass
+
+    mock_redis_instance.expire.side_effect = ResponseError("READONLY You can't write")
+
+    with patch.object(
+        redis_cache, "init_async_client", return_value=mock_redis_instance
+    ):
+        with pytest.raises(ResponseError, match="READONLY"):
+            await redis_cache.async_increment(key="rate_limit:window", value=1)
+
+    mock_redis_instance.ttl.assert_not_awaited()
+
+
 @pytest.mark.asyncio
 async def test_redis_client_init_with_socket_timeout(monkeypatch, redis_no_ping):
     monkeypatch.setenv("REDIS_HOST", "my-fake-host")