diff --git a/tests/test_bugfix_encoder_window_optional.py b/tests/test_bugfix_encoder_window_optional.py
new file mode 100644
index 0000000..ce4744a
--- /dev/null
+++ b/tests/test_bugfix_encoder_window_optional.py
@@ -0,0 +1,69 @@
+import importlib.util
+import os
+import unittest
+
+
+class EncoderWindowBugfixOptionalTests(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        enabled = os.getenv("VOXMLX_ENABLE_MLX_RUNTIME_TESTS", "").strip().lower() in {
+            "1",
+            "true",
+            "yes",
+            "on",
+        }
+        if not enabled:
+            raise unittest.SkipTest(
+                "Set VOXMLX_ENABLE_MLX_RUNTIME_TESTS=1 to run MLX runtime optional tests"
+            )
+        if importlib.util.find_spec("mlx") is None:
+            raise unittest.SkipTest("mlx is required for runtime optional tests")
+
+    def test_encode_step_uses_encoder_sliding_window(self):
+        import mlx.core as mx
+
+        from voxmlx.model import VoxtralRealtime
+
+        sliding_window = 7
+        config = {
+            "dim": 16,
+            "ada_rms_norm_t_cond_dim": 16,
+            "n_layers": 1,
+            "n_heads": 2,
+            "n_kv_heads": 1,
+            "head_dim": 8,
+            "hidden_dim": 32,
+            "vocab_size": 256,
+            "rope_theta": 1e6,
+            "multimodal": {
+                "whisper_model_args": {
+                    "encoder_args": {
+                        "audio_encoding_args": {"num_mel_bins": 128},
+                        "dim": 16,
+                        "n_layers": 2,
+                        "n_heads": 2,
+                        "head_dim": 8,
+                        "hidden_dim": 32,
+                        "rope_theta": 1e6,
+                        "sliding_window": sliding_window,
+                    },
+                    "downsample_args": {"downsample_factor": 4},
+                }
+            },
+        }
+        model = VoxtralRealtime(config)
+        mel_chunk = mx.zeros((128, 16), dtype=mx.float32)
+        _, _, _, encoder_cache, _ = model.encode_step(
+            mel_chunk,
+            conv1_tail=None,
+            conv2_tail=None,
+            encoder_cache=None,
+            ds_buf=None,
+        )
+        self.assertEqual(len(encoder_cache), 2)
+        for layer_cache in encoder_cache:
+            self.assertEqual(layer_cache.max_size, sliding_window)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/voxmlx/model.py b/voxmlx/model.py
index e2fd37e..1c712ab 100644
--- a/voxmlx/model.py
+++ b/voxmlx/model.py
@@ -118,8 +118,9 @@ def encode_step(self, new_mel, conv1_tail, conv2_tail, encoder_cache, ds_buf):
 
         # Create encoder cache on first call
         if encoder_cache is None:
+            window = int(self.encoder.sliding_window)
             encoder_cache = [
-                RotatingKVCache(100_000)
+                RotatingKVCache(window)
                 for _ in range(len(self.encoder.layers))
             ]