diff --git a/svelte-app/src/lib/canvas/collision.ts b/svelte-app/src/lib/canvas/collision.ts
index fdede1e..76809fa 100644
--- a/svelte-app/src/lib/canvas/collision.ts
+++ b/svelte-app/src/lib/canvas/collision.ts
@@ -401,9 +401,10 @@ function getEpcCollisionQuads(
   // Right box quad
   const last = waypoints[waypoints.length - 1];
   const prev = waypoints[waypoints.length - 2];
+  const rbDx = last.x - prev.x, rbDy = last.y - prev.y;
   const rbQ = boxQuad(
     ox + last.x, oy + last.y,
-    last.x - prev.x, last.y - prev.y,
+    rbDy, -rbDx, // rotated -90° to match perpendicular end box
     EPC_CONFIG.rightBox.w, EPC_CONFIG.rightBox.h,
     'right'
   );
diff --git a/svelte-app/src/lib/canvas/interactions.ts b/svelte-app/src/lib/canvas/interactions.ts
index 01dcb22..9d5ab85 100644
--- a/svelte-app/src/lib/canvas/interactions.ts
+++ b/svelte-app/src/lib/canvas/interactions.ts
@@ -360,8 +360,8 @@ function recalcEpcBounds(sym: typeof layout.symbols[0]) {
   // Right box corners (oriented along last segment)
   const last = wps[wps.length - 1];
   const prev = wps[wps.length - 2];
-  const rbDir = { x: last.x - prev.x, y: last.y - prev.y };
-  const rbCorners = orientedBoxCorners(last.x, last.y, rbDir.x, rbDir.y, EPC_CONFIG.rightBox.w, EPC_CONFIG.rightBox.h, 'right');
+  const rbDx = last.x - prev.x, rbDy = last.y - prev.y;
+  const rbCorners = orientedBoxCorners(last.x, last.y, rbDy, -rbDx, EPC_CONFIG.rightBox.w, EPC_CONFIG.rightBox.h, 'right');
   for (const [bx, by] of rbCorners) {
     minX = Math.min(minX, bx); minY = Math.min(minY, by);
     maxX = Math.max(maxX, bx); maxY = Math.max(maxY, by);