diff --git a/src/lib/layout/Gutter.tsx b/src/lib/layout/Gutter.tsx
index b0c28a8..49e9399 100644
--- a/src/lib/layout/Gutter.tsx
+++ b/src/lib/layout/Gutter.tsx
@@ -106,7 +106,20 @@ export default function Gutter({
       // Promote gesture: armed iff cursor is inside the sibling box AND
       // past PROMOTE_TRIGGER_FRAC along the exit direction.
       if (info.promote) {
-        setArmed(isArmed(info.promote, xFrac, yFrac));
+        const armed = isArmed(info.promote, xFrac, yFrac);
+        // TEMP DEBUG: trace cursor + promote-eval each move so we can
+        // see why the gesture isn't arming on the user's setup.
+        // Remove this once the issue's diagnosed.
+        console.log("[gutter-drag]", {
+          splitId: info.splitId,
+          cursor: { x: xFrac.toFixed(3), y: yFrac.toFixed(3) },
+          siblingBox: info.promote.siblingBox,
+          exitDirection: info.promote.exitDirection,
+          armed,
+        });
+        setArmed(armed);
+      } else {
+        console.log("[gutter-drag] no promote context on", info.splitId);
       }
     },
     [containerRef, info, flushPending, setArmed],