check_paradigm_shift: restated bare-noun subject and modal period-split

scripts/check_paradigm_shift.py

@@ -28,6 +28,12 @@
        to a negated clause followed by an It/They/You + to-be sentence;
        looser period-split parallelism without negation stays LLM-only)
 
+  E — "<Noun> is not X. <Noun> is Y" (restated subject, with or without
+       the/this/that; the same words must open both sentences)
+
+  F — "is not just X. It may be / can become Y" (period-split with a
+       modal; lower precision, its own label so Ralph's LLM decides)
+
   D — "Not X but Y"               (Aristotelian inversion; informational)
 """
 from __future__ import annotations
@@ -87,6 +93,35 @@
         "antithesis-restated-subject",
         "high",
     ),
+    (
+        # Restated bare-noun subject at the start of a sentence: "Least
+        # privilege is not just fewer actions. Least privilege is smaller
+        # failure domains." Same backreference guard as above, for a subject
+        # of one to three words without the/this/that (2026-10-23 miss).
+        re.compile(
+            rf"(?im)(?:^|(?<=[.!?] ))(?:[-*]\s+)?"
+            rf"([a-z]\w*(?:\s+\w+){{0,2}})\s+(?:is|are|was|were)"
+            rf"(?:\s+not|n{_AP}?t)\s+[^.;:\n]{{1,80}}\.\s+"
+            rf"\1\s+(?:is|are|was|were)\b"
+        ),
+        "antithesis-restated-noun",
+        "high",
+    ),
+    (
+        # Period-split with a modal or "become" in the second sentence:
+        # "... is not just a cluster detail. It can become a lateral movement
+        # primitive." Requires "not just" ("The build is not finished. It can
+        # be retried." is ordinary prose). Lower precision than the forms
+        # above (a regex cannot tell whether "It" refers to the rejected
+        # subject), so the label is kept separate and Ralph's LLM pass decides.
+        re.compile(
+            rf"(?i)\b(?:is|are|was|were)(?:\s+not|n{_AP}?t)\s+just\s+"
+            rf"[^.;:\n]{{1,80}}\.\s+(?:It|They|This)\s+"
+            rf"(?:(?:may|might|can|could)\s+(?:also\s+)?(?:be|become)|becomes?)\b"
+        ),
+        "antithesis-period-split-modal",
+        "high",
+    ),
     (
         re.compile(
             r"(?i)\bnot\s+[a-z]\w+(?:ing|ed|s|ly)?[,.\s]+but\s+[a-z]\w+"

tests/test_check_paradigm_shift.py

@@ -135,6 +135,68 @@ def test_negative_no_negation(self):
         self.assertNotIn("antithesis-restated-subject", labels_for(text))
 
 
+class TestRestatedNoun(unittest.TestCase):
+    """'<Noun> is not X. <Noun> is Y.' without the/this/that (2026-10-23 miss)."""
+
+    def test_bare_noun_not_just(self):
+        # iam-blast-radius-architecture-problem L28
+        text = "Least privilege is not just fewer actions. Least privilege is smaller failure domains."
+        self.assertIn("antithesis-restated-noun", labels_for(text))
+
+    def test_mid_paragraph_and_contraction(self):
+        text = "We tried. Defense in depth isn’t a product. Defense in depth is a habit."
+        self.assertIn("antithesis-restated-noun", labels_for(text))
+
+    def test_bullet(self):
+        text = "- Logging is not a control. Logging is evidence."
+        self.assertIn("antithesis-restated-noun", labels_for(text))
+
+    def test_determiner_form_reported_once(self):
+        text = "The goal is not a prettier IAM policy. The goal is a smaller blast radius."
+        self.assertEqual(labels_for(text), ["antithesis-restated-subject"])
+
+    def test_negative_different_subject(self):
+        text = "Logging is not enabled. Monitoring is on."
+        self.assertNotIn("antithesis-restated-noun", labels_for(text))
+
+    def test_negative_subject_mid_sentence(self):
+        # the repeated words do not open the first sentence
+        text = "We know least privilege is not free. Least privilege is still worth it."
+        self.assertNotIn("antithesis-restated-noun", labels_for(text))
+
+
+class TestPeriodSplitModal(unittest.TestCase):
+    """'... is not just X. It may be / can become Y.' (2026-10-23 miss)."""
+
+    def test_it_may_be(self):
+        # iam-blast-radius-architecture-problem L32
+        text = (
+            "A workload identity that can read secrets is not just an "
+            "application permission. It may be a persistence path."
+        )
+        self.assertIn("antithesis-period-split-modal", labels_for(text))
+
+    def test_it_can_become(self):
+        # iam-blast-radius-architecture-problem L33
+        text = (
+            "A service account that can exec into pods is not just a cluster "
+            "detail. It can become a lateral movement primitive."
+        )
+        self.assertIn("antithesis-period-split-modal", labels_for(text))
+
+    def test_it_becomes(self):
+        text = "The runner is not just a build box. It becomes a deploy credential."
+        self.assertIn("antithesis-period-split-modal", labels_for(text))
+
+    def test_negative_without_just(self):
+        text = "The build is not finished. It can be retried after the fix."
+        self.assertEqual(labels_for(text), [])
+
+    def test_negative_will_be(self):
+        text = "The report is not just late. It will be rewritten."
+        self.assertNotIn("antithesis-period-split-modal", labels_for(text))
+
+
 class TestExistingPatternsStillWork(unittest.TestCase):
     def test_pronoun_period_split_iam_blast(self):
         # iam-blast-radius-github-action L16 (2026-10-23): flagged here, but the