Slot 2, the decision place: Chandrupatla's own acceptance band, put inside our step rule as an instrument, does NOT close the gap - CHA 3066 (project) / 2899 (credit) against his 2423, while APS doubles 2806 -> 5432, and the band is not idle (63.6% refusals). The fifth independent test of one conclusion: the remaining gap is the ORDER of the model the step is built on, not the place the similarity is read in. By the declared stop rule (M1 and M2 both false) the 'where is the similarity read' line is closed: all four places measured.

Not empty-handed: our own parameter-free reading 'defect' - refuse when |phi - xi| > min(xi, 1 - xi) - sets a new canonical best, APS 2523 at 153/154 (previous 2527, Chandrupatla 2785), guarantee intact (0 of 135 family cells), refusing on 7.0% of steps. It is a second point on the same trade, not a replacement: 5733 over both sets against 5511, because CHA gives back 3210. Also: _shape_ratios crashed on a missing third point, which evaluate would have turned into a silent sweep of zeros; the slope-gate pin was anchored on line spelling; and the server copy had drifted (stale relax/sor.py, test_relaxation.py absent - 746 tests instead of 755). All synced, 92/92 files identical by content, 755 pass on the server.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

sweep_full.py

@@ -204,6 +204,29 @@ def build_grid_log(smoke):
             for sim in sims for sc in ("derived", "derived3") for gu in guards]
 
 
+def _preflight_decision_mode():
+    """Fail LOUDLY if the decision readings are not deployed (see _preflight_log_mode)."""
+    for md in ("band", "defect", "simpair"):
+        x, _n, ok = pure_root(lambda t: t - 1.0, 0.0, 3.0, 1e-10, 100,
+                              similarity="ratio", scale="derived3", guard="credit",
+                              prestep=md)
+        if not (ok and abs(x - 1.0) < 1e-8):
+            raise SystemExit(f"decision-mode preflight FAILED for prestep={md}: "
+                             "refusing to run a sweep that would report zeros")
+
+
+def build_grid_decision(smoke):
+    """Slot 2 of PREREG 2026-09-21: the DECISION place.  One thing moves against the
+    published cells — the reading in the gate — so 'none' and 'slope' are in the grid as
+    its own controls.  'band' is Chandrupatla's rule and is an instrument, not a claim."""
+    _preflight_decision_mode()
+    sims = ["ratio", "rational"] if smoke else sorted(PURE_SIMS)
+    guards = ("credit", "safe") if smoke else GUARD_MODES
+    modes = ("none", "slope", "band", "defect", "simpair")
+    return [("pure", sim, "derived3", gu, "x", md, "recent", "distance", "none")
+            for sim in sims for md in modes for gu in guards]
+
+
 def _preflight_order_mode():
     """Fail LOUDLY if the per-place reading is not actually deployed.
 
@@ -310,10 +333,12 @@ def main():
     slopemode = "--slope" in sys.argv      # the slope-stability gate grid
     capmode = "--cap" in sys.argv          # scale selected between the two computed ones
     ordermode = "--order" in sys.argv      # slot 1: the similarity read BY PLACE
+    decmode = "--decision" in sys.argv     # slot 2: the reading in the DECISION place
     combomode = "--combo" in sys.argv      # modes A and B together
     pointsmode = "--points" in sys.argv    # mode A: triple by shape
     dirmode = "--direction" in sys.argv    # mode B: far end by dissimilarity
-    specs = (build_grid_order(smoke) if ordermode else
+    specs = (build_grid_decision(smoke) if decmode else
+             build_grid_order(smoke) if ordermode else
              build_grid_cap(smoke) if capmode else
              build_grid_combo(smoke) if combomode else
              build_grid_points(smoke) if pointsmode else
@@ -336,8 +361,9 @@ def main():
 
     # the published sweep_full.json is what verify_article.py checks the paper
     # against, so the log grid never writes into it
-    if ordermode or capmode or combomode or pointsmode or dirmode:
-        base = ("sweep_order" if ordermode else
+    if decmode or ordermode or capmode or combomode or pointsmode or dirmode:
+        base = ("sweep_decision" if decmode else
+                "sweep_order" if ordermode else
                 "sweep_cap" if capmode else
                 "sweep_combo" if combomode else
                 "sweep_points" if pointsmode else "sweep_direction")