diff --git a/eval/cold_run_b/measure.py b/eval/cold_run_b/measure.py
index f1c3d6d8..da5feca0 100644
--- a/eval/cold_run_b/measure.py
+++ b/eval/cold_run_b/measure.py
@@ -79,8 +79,18 @@ def report(m, label):
           f"total=${m['total']:.6f}   per attempt (from trace_id): {m['per_attempt']}")
     print(f"  UNITS total={m['units']}   paid (sum cost>0)={m['paid_units']}   "
           f"{'⚠ the paid filter removed nothing — its behaviour is still unexercised' if m['units'] == m['paid_units'] else 'the paid filter DID remove units'}")
+    # ⛔ THE DIVISION IS GUARDED, AND THE REASON IS THE BEST ARGUMENT THIS FILE CARRIES. Two lines above,
+    # this same report prints "the paid filter removed nothing — its behaviour is still unexercised"
+    # whenever every unit was paid for. On run A and run B that was true, so the branch where NOTHING was
+    # paid for never ran — and the first time it did (the $0 smoke base, and any empty project), the
+    # instrument died with ZeroDivisionError instead of printing its own zero. An unexercised branch of a
+    # MEASURING tool is not a cosmetic gap: the one reading where the share is undefined is exactly the
+    # reading a $0 arm produces, which is where an instrument is supposed to be rehearsed before it meets
+    # money. Found by the acceptance, not by the author, on a base this file had already been run against.
+    share = f"{100 * m['n1'] / m['paid_units']:.1f}% of units" if m["paid_units"] else \
+            "share UNDEFINED — no unit was paid for at all (not the same statement as 0%)"
     print(f"  NUMERATOR 1 — a paid attempt that was not kept: {m['n1']} of {m['paid_units']} units = "
-          f"{100 * m['n1'] / m['paid_units']:.1f}% of units   (money ${m['n1_money']:.6f} = {pct(m['n1_money'])})")
+          f"{share}   (money ${m['n1_money']:.6f} = {pct(m['n1_money'])})")
     for k in m["n1_keys"]:
         print(f"      {k}")
     print(f"  NUMERATOR 2 — a cell whose KEPT result was paid for more than once: {m['n2']} units")