diff --git a/src/alpamayo_r1/helper.py b/src/alpamayo_r1/helper.py
index b5ae4da..74779f0 100644
--- a/src/alpamayo_r1/helper.py
+++ b/src/alpamayo_r1/helper.py
@@ -86,11 +86,12 @@ def to_device(
 ) -> Any:
     """Recursively cast data into the specified device, dtype."""
     if isinstance(data, torch.Tensor):
-        data = data.to(
-            device=device,
-            dtype=dtype,
-        )
-        return data
+        # Only apply dtype conversion to floating-point tensors.
+        # Integer tensors (e.g., input_ids, attention_mask) must preserve their dtype
+        # for compatibility with Hugging Face models during mixed-precision inference.
+        if dtype is not None and data.is_floating_point():
+            return data.to(device=device, dtype=dtype)
+        return data.to(device=device)
     elif isinstance(data, collections.abc.Mapping):
         return {key: to_device(data[key], device=device, dtype=dtype) for key in data}
     elif isinstance(data, collections.abc.Sequence) and not isinstance(data, (str, bytes)):