From 5d58b930b575e48bbb1aa5f705c9585eed9ebaad Mon Sep 17 00:00:00 2001
From: John Gibson <5562125+jgibson2@users.noreply.github.com>
Date: Fri, 28 Nov 2025 17:32:29 +0000
Subject: [PATCH 1/2] Support negative dimensions on
 "aten.split_with_sizes_copy.default"

---
 backends/apple/mps/operators/shape_ops.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/backends/apple/mps/operators/shape_ops.py b/backends/apple/mps/operators/shape_ops.py
index 76c559018be..528a6b60bd8 100644
--- a/backends/apple/mps/operators/shape_ops.py
+++ b/backends/apple/mps/operators/shape_ops.py
@@ -243,6 +243,8 @@ def define_node(
         split_sizes = eval_shape(cast(torch.SymInt, node.args[1]))
         dim = cast(int, node.args[2])
         input_shape = get_shape(get_input_node(node, 0))
+        if dim < 0:
+            dim += len(input_shape)
 
         if dim < 0 or dim >= len(input_shape):
             raise RuntimeError(

From 5f1a078491d239e639c4e2517bcd02e26237ca7b Mon Sep 17 00:00:00 2001
From: John Gibson <5562125+jgibson2@users.noreply.github.com>
Date: Fri, 28 Nov 2025 17:42:49 +0000
Subject: [PATCH 2/2] Report original uncorrected dimension on failure.

---
 backends/apple/mps/operators/shape_ops.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/backends/apple/mps/operators/shape_ops.py b/backends/apple/mps/operators/shape_ops.py
index 528a6b60bd8..d75e42d1c45 100644
--- a/backends/apple/mps/operators/shape_ops.py
+++ b/backends/apple/mps/operators/shape_ops.py
@@ -248,7 +248,7 @@ def define_node(
 
         if dim < 0 or dim >= len(input_shape):
             raise RuntimeError(
-                f"split_copy: dim {dim} out of range for input tensor with {len(input_shape)} dimensions"
+                f"split_copy: dim {cast(int, node.args[2])} out of range for input tensor with {len(input_shape)} dimensions"
             )
 
         mps_node = MPSNode(