From 037daf1121e8870007fdf2bf3c8cc60cd32d93b1 Mon Sep 17 00:00:00 2001
From: "R. Timothy Edwards" <tim@opencircuitdesign.com>
Date: Thu, 5 Mar 2026 18:04:53 -0500
Subject: [PATCH] Found an issue with coupling capacitance where contact types
 not surrounded by metal are not checked for perimeter coupling parasitic
 capacitance to other layers.

---
 extract/ExtCouple.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/extract/ExtCouple.c b/extract/ExtCouple.c
index 95edd2c7..96b7b1ed 100644
--- a/extract/ExtCouple.c
+++ b/extract/ExtCouple.c
@@ -1289,6 +1289,14 @@ extFindOverlap(tp, area, esws)
     TileType tin = TiGetType(bp->b_inside);
     TileType tout = TiGetType(bp->b_outside);
 
+    /* Get residues
+     * (Note:  Isn't it better to include contacts in the tables?)
+     */
+    if (DBIsContact(tin))
+	tin = DBPlaneToResidue(tin, esws->plane_of_boundary);
+    if (DBIsContact(tout))
+	tout = DBPlaneToResidue(tout, esws->plane_of_boundary);
+
     pMask = ExtCurStyle->exts_sideOverlapOtherPlanes[tin][tout];
     extOverlapDef = esws->def;