diff --git a/app/services/regime_monitor_service.py b/app/services/regime_monitor_service.py
index dd2632f..8dae0f1 100644
--- a/app/services/regime_monitor_service.py
+++ b/app/services/regime_monitor_service.py
@@ -139,8 +139,10 @@ P3_DRAWDOWN_ANCHORS = (
 # why the crossing gets a floor of 20 rather than starting at 0. Calibrated to
 # sit alongside P3 rather than swamp it -- the 200-DMA lags, so a 20% drawdown
 # typically coincides with ~10% below the average, where this reads ~61 against
-# P3's ~59. Over the 408 sessions to 2026-07-24 P1 is the sole price argmax on
-# 17 of them (4.2%), so it informs the pillar without owning it.
+# P3's ~59. On the population the P1_SCORE_CAP rule actually names -- sessions
+# with State >= 40 -- P1 is the sole price argmax on 17 of 47 (36.2%), against
+# P2's 16 and P3's 14, so it informs the pillar without owning it and no cap
+# was needed.
 P1_TREND_BREAK_ANCHORS = (
     (0.0, 20.0), (3.0, 35.0), (8.0, 55.0), (15.0, 75.0), (25.0, 100.0),
 )
diff --git a/docs/research/regime-monitor-v4.md b/docs/research/regime-monitor-v4.md
index 4649cf6..494bbfd 100644
--- a/docs/research/regime-monitor-v4.md
+++ b/docs/research/regime-monitor-v4.md
@@ -57,9 +57,11 @@ used to read 100.
 
 `max()` was **kept**. The defect was the step function feeding it, not the vote
 itself, and v3's "one capped vote for correlated reads" rationale still holds.
-Over the window P1 is the sole price argmax on 17 of 408 sessions (4.2%), so it
-informs the pillar without owning it — the `P1_SCORE_CAP` fallback considered
-during design was measured as unnecessary and not shipped.
+The `P1_SCORE_CAP` fallback drafted during design was to fire if P1 became the
+sole price argmax on **more than 80% of sessions with State ≥ 40** — i.e. if it
+had quietly become a second drawdown sensor. Measured on that population: 47
+qualifying sessions, P1 sole argmax on **17 of them (36.2%)**, against P2's 16
+and P3's 14. Well under the threshold, so the cap is not shipped.
 
 **The top State band moved 80 → 65.** See Calibration; this is the one change
 that is about the band rather than a sensor.
@@ -148,7 +150,7 @@ against P3's ~59.
 V1 reaches full scale at 55 rather than at 2020's ~82: anchoring the top at a
 once-in-a-generation print would make VIX 50 — a genuine crisis — read only ~70.
 The anchors encode the long-run distribution as constants, the same argument the
-credit level uses. Unlike P3 and V1, whose slopes ease off monotonically, P3's do
+credit level uses. Unlike P1 and V1, whose slopes ease off monotonically, P3's do
 not (2.5, 3.75, 3.125, 2.33, 1.83) — its gentle onset is intentional and the
 monotone-slope test excludes it.
 
diff --git a/scripts/run_regime_monitor_calibration.py b/scripts/run_regime_monitor_calibration.py
index d6a2499..fb1ff8c 100644
--- a/scripts/run_regime_monitor_calibration.py
+++ b/scripts/run_regime_monitor_calibration.py
@@ -267,7 +267,11 @@ OAS_SOURCE_TRUNCATION = {"v2_reconstruction_oas400": 400}
 
 # A v4 recommendation is meaningless without both of these: the row-wise
 # state_v4 <= state_v3 invariant needs them, and it is a hard gate.
-REQUIRED_VARIANTS = ("v3", "v4")
+# v2_reconstruction is required too: it carries every published figure the
+# reproduction rests on (avg/p80/max/P3-pegged/W1-live). Without it a run could
+# emit a confident recommendation having checked nothing against v2 at all,
+# while the methodology doc claims v2 and v3 are reproduced first.
+REQUIRED_VARIANTS = ("v2_reconstruction", "v3", "v4")
 
 
 @contextlib.contextmanager
@@ -681,7 +685,7 @@ def _parse_args() -> argparse.Namespace:
                    help="per-session slice for the canonical run")
     p.add_argument("--oas-fetch-days", type=int, default=int(365.25 * 13),
                    help="fetch range; matches v2's request (ICE truncates to ~3y)")
-    p.add_argument("--methodology", default="v3,v4")
+    p.add_argument("--methodology", default=",".join(REQUIRED_VARIANTS))
     p.add_argument("--expected-first-session", default=None,
                    help="assert the first replayed date. Defaults to the published "
                         "window's start; REQUIRED when --end/--sessions are overridden, "
@@ -748,7 +752,8 @@ async def _main() -> int:
     missing = [v for v in REQUIRED_VARIANTS if v not in variants]
     if missing:
         print(f"--methodology must include {list(REQUIRED_VARIANTS)}; missing {missing}. "
-              "The state_v4 <= state_v3 invariant is a hard gate and needs both.",
+              "v2_reconstruction carries the published reproduction figures, and "
+              "v3+v4 are needed for the state_v4 <= state_v3 invariant gate.",
               file=sys.stderr)
         return 2
 
diff --git a/tests/unit/test_regime_calibration_script.py b/tests/unit/test_regime_calibration_script.py
index fdb80f1..0f9984f 100644
--- a/tests/unit/test_regime_calibration_script.py
+++ b/tests/unit/test_regime_calibration_script.py
@@ -139,3 +139,45 @@ class TestScenarios:
         # ...and it must clear the chosen threshold under either P2 assumption.
         assert min(rows["S3a"]["state"], rows["S3b"]["state"]) > 65.0
         assert rows["S1"]["state"] < 20.0
+
+
+class TestRefusals:
+    """The harness's safety contract: it must decline rather than under-report.
+
+    Both paths return before any network call, so these are fast and offline.
+    """
+
+    def _run(self, argv, monkeypatch):
+        import asyncio
+        import sys
+
+        monkeypatch.setattr(sys, "argv", ["run_regime_monitor_calibration.py", *argv])
+        return asyncio.run(calib._main())
+
+    def test_refuses_without_every_required_variant(self, monkeypatch):
+        assert self._run(["--methodology", "v3,v4"], monkeypatch) == 2
+        assert self._run(["--methodology", "v2_reconstruction,v3"], monkeypatch) == 2
+
+    def test_refuses_an_unknown_variant(self, monkeypatch):
+        assert self._run(["--methodology", "v3,v4,nonsense"], monkeypatch) == 2
+
+    def test_refuses_a_custom_window_without_a_calendar_anchor(self, monkeypatch):
+        """--sessions alone can only ever be tautological, so the start date must
+        be supplied explicitly once the published window is left behind."""
+        assert self._run(
+            ["--methodology", ",".join(calib.REQUIRED_VARIANTS), "--sessions", "100"],
+            monkeypatch,
+        ) == 2
+        assert self._run(
+            ["--methodology", ",".join(calib.REQUIRED_VARIANTS), "--end", "2026-01-05"],
+            monkeypatch,
+        ) == 2
+
+    def test_the_default_invocation_satisfies_its_own_requirement(self, monkeypatch):
+        """A default that the requirement rejects would make every bare run fail."""
+        import sys
+
+        monkeypatch.setattr(sys, "argv", ["run_regime_monitor_calibration.py"])
+        default = calib._parse_args().methodology.split(",")
+        assert set(calib.REQUIRED_VARIANTS) <= set(default)
+        assert set(calib.REQUIRED_VARIANTS) <= set(calib.VARIANTS)