diff --git a/results-loop/PROTOCOL_UNIFIED.md b/results-loop/PROTOCOL_UNIFIED.md
index 7ea28e4..e7c15e4 100644
--- a/results-loop/PROTOCOL_UNIFIED.md
+++ b/results-loop/PROTOCOL_UNIFIED.md
@@ -54,3 +54,13 @@ number for the unified adapter exists at time of writing.
    add 1-3 extra KV-recomputing attention channels) → holds or improves.
    Body-length confound noted: earlier anchors lengthen the loop body; if
    results shift, run matched-length control (12,28) before interpreting.
+
+10. **L9 discriminator arm (pre-registered 2026-07-14 ~10:00, before running).**
+    Band (9,30): anchor at L9 — the only other full-attention, KV-computing
+    layer below the boundary — deep in the lens's sensor regime, tap fixed at
+    L30. Separates the two cliff explanations: (a) "lens boundary" predicts
+    catastrophic (like anchors 11-13: 25-34% overall); (b) "full-attention
+    KV-layer entry" predicts partial recovery (clearly above the L11-13
+    trend, i.e. >40% overall or hard >25%). Registered prediction: (a) —
+    the sensor-region content dominates; layer type does not rescue it.
+    Same recipe/checkpoint/eval as the anchor sweep (250 items, ks 0,2,4).