diff --git a/tests/attention/test_gqa_decode_opt2.py b/tests/attention/test_gqa_decode_opt2.py
index 459b228..9314cda 100644
--- a/tests/attention/test_gqa_decode_opt2.py
+++ b/tests/attention/test_gqa_decode_opt2.py
@@ -97,12 +97,20 @@ def test_opt3_dispatch_exceeds_opt2_by_2x():
 
 
 def test_dispatch_ratio_R_sensitivity():
-    """ADR-0064 Test #9 — opt2 < opt3 across the queue-bandwidth range."""
-    for R in (0.25, 0.0625, 0.03125):
+    """ADR-0064 Test #9 — opt2 < opt3 across the queue-bandwidth range, and
+    the opt3/opt2 ratio increases as R decreases (the cost becomes more
+    FIXED-dominated, i.e. command-count-driven). Absolute ratio values are
+    informative only; the gate is the direction + opt2 < opt3."""
+    ratios = []
+    for R in (0.25, 0.0625, 0.03125):          # strictly decreasing R
         cm = PeCostModel(fixed_per_cmd_cycles=40, byte_cycles_recip=R)
         opt3 = _dispatch_cycles(_opt3_tile, cm)
         opt2 = _dispatch_cycles(_opt2_tile, cm)
         assert opt2 < opt3, f"R={R}: opt2={opt2} !< opt3={opt3}"
+        ratios.append(opt3 / opt2)
+    assert ratios[0] < ratios[1] < ratios[2], (
+        f"opt3/opt2 ratio must increase as R decreases; got {ratios}"
+    )
 
 
 # ── K-before-V DMA priority (ADR-0065 Test #3) ───────────────────────