From f768be6744559797fb3c4b23e299ab593bc6ac96 Mon Sep 17 00:00:00 2001
From: Mateusz Sluszniak <56299341+msluszniak@users.noreply.github.com>
Date: Tue, 28 Jul 2026 22:09:49 +0200
Subject: [PATCH] fix(mlx): forward boundary-partitioned getitem instead of
 indexing a Slot

The MLX partitioner can place a getitem in a partition while leaving its
multi-output parent (e.g. aten.native_layer_norm, common in DETR) outside it. In
that case _getitem_handler receives the already-selected element as a single
boundary-input Slot, not the source tuple, so a[idx] raised
"Slot object is not subscriptable" and aborted the export. Forward the Slot
directly when it isn't a tuple/list. Unblocks transformer/layer-norm models
(RF-DETR) through the MLX delegate.
---
 backends/mlx/ops.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/backends/mlx/ops.py b/backends/mlx/ops.py
index 002cda892f3..4053688b121 100644
--- a/backends/mlx/ops.py
+++ b/backends/mlx/ops.py
@@ -2272,9 +2272,13 @@ def _getitem_handler(P: MLXProgramBuilder, n: Node) -> Slot:
     require_kwargs(P.kwargs(n), set(), "operator.getitem")
     a, idx = args
     out = P.make_or_get_slot(n)
+    # When the multi-output parent is left outside the partition, the partitioner
+    # feeds this getitem the already-selected element as a single boundary-input
+    # Slot (not the source tuple). In that case forward it directly.
+    src = a[idx] if isinstance(a, (tuple, list)) else a
     P.emit(
         IdCopyNode(
-            x=P.slot_to_tid(a[idx]),
+            x=P.slot_to_tid(src),
             out=P.slot_to_tid(out),
         )
     )