From 83ec64158a2afc285f6d8add776fbf2ad48f7e61 Mon Sep 17 00:00:00 2001
From: Jan Petykiewicz <jan@mpxd.net>
Date: Tue, 31 Mar 2026 00:24:52 -0700
Subject: [PATCH] [AutoTool] fix exact s-bend validation

---
 masque/builder/tools.py               |  2 +-
 masque/test/test_autotool_refactor.py | 56 +++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/masque/builder/tools.py b/masque/builder/tools.py
index 4a82b34..68e89df 100644
--- a/masque/builder/tools.py
+++ b/masque/builder/tools.py
@@ -1031,7 +1031,7 @@ class AutoTool(Tool, metaclass=ABCMeta):
                 jog_remaining = jog - itrans_dxy[1] - otrans_dxy[1]
                 if sbend.jog_range[0] <= jog_remaining < sbend.jog_range[1]:
                     sbend_dxy = self._sbend2dxy(sbend, jog_remaining)
-                    success = numpy.isclose(length, sbend_dxy[0] + itrans_dxy[1] + otrans_dxy[1])
+                    success = numpy.isclose(length, sbend_dxy[0] + itrans_dxy[0] + otrans_dxy[0])
                     if success:
                         b_transition = None
                         straight_length = 0
diff --git a/masque/test/test_autotool_refactor.py b/masque/test/test_autotool_refactor.py
index 677ddd6..d93f935 100644
--- a/masque/test/test_autotool_refactor.py
+++ b/masque/test/test_autotool_refactor.py
@@ -108,6 +108,62 @@ def test_autotool_planS_double_L(multi_bend_tool) -> None:
     assert data.ldata1.straight_length == 0
     assert data.l2_length == 6
 
+
+def test_autotool_planS_pure_sbend_with_transition_dx() -> None:
+    lib = Library()
+
+    def make_straight(length: float) -> Pattern:
+        pat = Pattern()
+        pat.ports["A"] = Port((0, 0), 0, ptype="core")
+        pat.ports["B"] = Port((length, 0), pi, ptype="core")
+        return pat
+
+    def make_sbend(jog: float) -> Pattern:
+        pat = Pattern()
+        pat.ports["A"] = Port((0, 0), 0, ptype="core")
+        pat.ports["B"] = Port((10, jog), pi, ptype="core")
+        return pat
+
+    trans_pat = Pattern()
+    trans_pat.ports["EXT"] = Port((0, 0), 0, ptype="ext")
+    trans_pat.ports["CORE"] = Port((5, 0), pi, ptype="core")
+    lib["xin"] = trans_pat
+
+    tool = AutoTool(
+        straights=[
+            AutoTool.Straight(
+                ptype="core",
+                fn=make_straight,
+                in_port_name="A",
+                out_port_name="B",
+                length_range=(1, 1e8),
+                )
+            ],
+        bends=[],
+        sbends=[
+            AutoTool.SBend(
+                ptype="core",
+                fn=make_sbend,
+                in_port_name="A",
+                out_port_name="B",
+                jog_range=(0, 1e8),
+                )
+            ],
+        transitions={
+            ("ext", "core"): AutoTool.Transition(lib.abstract("xin"), "EXT", "CORE"),
+            },
+        default_out_ptype="core",
+        )
+
+    p, data = tool.planS(15, 4, in_ptype="ext")
+
+    assert_allclose(p.offset, [15, 4])
+    assert_allclose(p.rotation, pi)
+    assert data.straight_length == 0
+    assert data.jog_remaining == 4
+    assert data.in_transition is not None
+
+
 def test_renderpather_autotool_double_L(multi_bend_tool) -> None:
     tool, lib = multi_bend_tool
     rp = RenderPather(lib, tools=tool)