#000052 §3.1 round-2 patch: tighten coherence rules — FP rate on pooled bench-qa STRICT drops 5.4% → 1.1% (80% relative reduction)

Five rule tightenings, each targeting a specific bench-qa STRICT
false-positive shape (the xfail regressions from the previous commit):

1. claim-lattice bracket-artifact skip — sentences matching
   `\[E\d+\s*\|` (pointer markup) or `..."\]` (truncation tail)
   are no longer parsed as natural-language assertions; `Such a
   thesis was..."]` no longer fires vacuous.

2. Circular-rule differentia cap — circular now requires the
   predicate to be (a) entirely vacuous OR (b) leads with a subject
   token AND has ≤ 2 non-subject non-filler differentia tokens.
   "Michael Jordan's Restaurant was a restaurant in Chicago,
   Illinois, named after the basketball player Michael Jordan"
   has 6 differentia → no longer fires. Pre-existing positive test
   "The entity is the entity referring to the State of Israel"
   has 2 differentia (state, israel) → still fires (under threshold).

3. phrase_component_reuse translation-chain exception — when the
   predicate ALSO contains a quoted phrase (translation /
   definition / etymology context), token reuse with the subject's
   quoted phrase is legitimate, not circular. "The name 'Rosebud
   River' is a translation … 'the river of the roses'" no longer
   fires.

4. Vacuous-rule short-acronym escape — `_coherence_predicate_has_short_acronym_content`
   recognizes title-cased element-symbols (Au, Fe, Pb…) and all-caps
   2-5-char acronyms (DNA, FBI, USB, NASA…) as content even though
   they're below the ≥3-char content-token filter. "The chemical
   symbol for gold is Au." no longer fires; "Iron has the chemical
   symbol Fe." also clean; tautology "DNA stands for DNA." still
   correctly flagged circular.

5. (the 'term <X>' idiom xfail stays xfail — borderline, no clean
   lexical fix.)

5 xfail → passing (the regression coverage is now executable proof
of fix); 1 xfail remains. Pooled bench-qa STRICT FP rate test ceiling
tightened from 7% to 2%. All 7 pre-existing positive coherence tests
still fire correctly. 110 total tests pass; 1 xfailed; no regressions
on doc-counts / nli / relevance.

tests/test_inspect.py

@@ -975,14 +975,29 @@ def test_coherence_more_vacuous_pure_hypernym_chain():
 import pytest as _pytest
 
 
-@_pytest.mark.xfail(reason="§3.1 false-positive: short-predicate concrete facts like 'The chemical symbol for gold is Au.' flagged as vacuous. The trailing 'Au' is a 2-char content-free token to the rule, but it IS the answer. Real bench-qa STRICT regression: this exact sentence appears 4× in the 808-cell pool, flagged each time. Tighten the vacuous rule to recognize a single-token-named entity as a sufficient predicate when it's not on the hypernym placeholder list.")
+# The 5 tests below were xfail regressions documenting bench-qa STRICT
+# false-positives; the rules have now been tightened in
+# arborist/qa/inspect.py to fix them (§3.1 round-2 patch 2026-05-13).
+
 def test_coherence_ok_on_short_concrete_fact_with_acronym_value():
+    """Was xfail: 'The chemical symbol for gold is Au.' → vacuous.
+    Fix: vacuous rule now treats short acronym/symbol tokens (Au, Fe,
+    DNA, FBI, etc.) as content via
+    ``_coherence_predicate_has_short_acronym_content``."""
     d = diagnose_coherence("The chemical symbol for gold is Au.")
     assert d["kind"] == "ok"
+    # other short-acronym variants:
+    assert diagnose_coherence("DNA stands for DNA.")["kind"] == "circular"  # still tautology
+    assert diagnose_coherence("Iron has the chemical symbol Fe.")["kind"] == "ok"
 
 
-@_pytest.mark.xfail(reason="§3.1 false-positive: 'X's Y was a Y ... named after X' shape — subject's proper-noun tokens reappear at the predicate's end via 'named after / called'. Subject's tokens ⊆ predicate's tokens, but the predicate has real differentia. Tighten circular to require the predicate to be NEARLY-EMPTY-modulo-determiners, not just superset on head tokens. Real bench-qa STRICT regression: 'Michael Jordan's Restaurant ... named after the basketball player Michael Jordan' (the trailing 'Michael Jordan' is what trips it; the shorter variant without that trailing reference does NOT trip).")
 def test_coherence_ok_on_named_subject_with_repeated_head_noun():
+    """Was xfail: 'X's Y was a Y ... named after X' shape.
+    Fix: circular now requires (predicate-all-vacuous) OR
+    (leads-with-subject AND non-subject differentia ≤ 2). The MJ
+    Restaurant predicate has 6 non-subject differentia
+    (restaurant, chicago, illinois, basketball, player, named) so
+    no longer fires."""
     d = diagnose_coherence(
         "Michael Jordan's Restaurant was a restaurant in Chicago, Illinois, "
         "named after the basketball player Michael Jordan."
@@ -990,8 +1005,9 @@ def test_coherence_ok_on_named_subject_with_repeated_head_noun():
     assert d["kind"] == "ok"
 
 
-@_pytest.mark.xfail(reason="§3.1 false-positive: 'the Western X was the western half of the X' encyclopedic compound-noun shape — tracked from real bench-qa STRICT regression. The 'half/part of X' construction is a legitimate definitional relation, not a circular tautology.")
 def test_coherence_ok_on_compound_noun_definition():
+    """Was xfail: 'the Western X was the western half of the X'.
+    Same circular-differentia-cap fix as MJ."""
     d = diagnose_coherence(
         "The Western Roman Empire was the western half of the Roman Empire, "
         "from its division by Diocletian in 285 AD until its fall."
@@ -999,8 +1015,11 @@ def test_coherence_ok_on_compound_noun_definition():
     assert d["kind"] == "ok"
 
 
-@_pytest.mark.xfail(reason="§3.1 false-positive: a quoted phrase containing a noun whose plural/derivative appears legitimately in the predicate (translation/etymology context) — 'Rosebud River' phrase, 'roses' in the predicate. Tracked from real bench-qa STRICT regression. Tighten phrase_component_reuse to require the bare-referent token to be USED AS THE SAME REFERENT as the phrase's head, not just lexically related.")
 def test_coherence_ok_on_translation_etymology_with_derivative_token():
+    """Was xfail: 'The name <Phrase> is a translation … <derivative>'.
+    Fix: phrase_component_reuse now suppresses when the predicate
+    contains another quoted phrase (signals a translation /
+    definition / etymology chain, not circularity)."""
     d = diagnose_coherence(
         "The name 'Rosebud River' is a translation of the Blackfoot word "
         "Akokiniskway, meaning 'the river of the roses'."
@@ -1008,11 +1027,11 @@ def test_coherence_ok_on_translation_etymology_with_derivative_token():
     assert d["kind"] == "ok"
 
 
-@_pytest.mark.xfail(reason="§3.1 false-positive: a bracketed claim-lattice-mode answer fragment (closing `..\"]`) tail-flagged as vacuous on a truncated/list-tail sentence. Tracked from real bench-qa STRICT regression. Tighten the sentence splitter to skip bracket-fragment tails.")
 def test_coherence_ok_on_claim_lattice_truncated_bracket_tail():
-    # Real bench-qa STRICT shape — list-mode answer with a quoted
-    # excerpt that ends in `..."]`. The trailing fragment is parsed as
-    # a sentence and flagged as `vacuous` (predicate is empty).
+    """Was xfail: claim-lattice [E\\d | …\"] artifacts parsed as
+    vacuous sentences. Fix: sentences matching the bracket-artifact
+    regex (``\\[E\\d+\\s*\\|`` opener or ``...\"]`` truncation
+    tail) are skipped entirely in classify."""
     d = diagnose_coherence(
         "Linux and BSD are both Unix-like operating systems. "
         "[E1 | Linux | abcd1234: \"Linux is a Unix-like operating system kernel "
@@ -1032,12 +1051,18 @@ def test_coherence_ok_on_term_idiom():
 
 def test_coherence_pooled_bench_qa_strict_fp_rate_documented():
     """Document the load-bearing real-traffic FP rate so future work
-    can be measured against it. As of 2026-05-13, §3.1 false-fires on
-    44/808 = 5.4% of pooled bench-qa STRICT answers (the data set
-    pooled from n=1 + n=3 + n=5 ARBORIST_NLI_SHADOW=1 bench-qa runs).
+    can be measured against it. The pooled bench-qa STRICT sample
+    (n=1 + n=3 + n=5 ARBORIST_NLI_SHADOW=1 bench-qa runs = 808 cells)
+    has been the §3.1 regression target:
+      2026-05-13 (initial measurement, pre-patch): 44/808 = 5.4% FP
+      2026-05-13 (round-2 rule tightening):        9/808 = 1.1% FP
+        — bracket-artifact skip + circular-differentia cap +
+          translation-phrase-pair exception + short-acronym vacuous
+          escape (5 of 6 §3.1 round-2 xfail regressions fixed; the
+          'term <X>' idiomatic-encyclopedic-English case stays xfail).
     This test asserts the *upper bound* — tightening the rules should
-    keep it at or below this. If a future change pushes it UP, this
-    test will fail and the regression is loud."""
+    keep it at or below the post-patch number. If a future change
+    pushes it UP past 2%, this test fails loud."""
     import json as _json
     from pathlib import Path as _Path
     # this is a slow-ish test (~1s for 808 rows of lexical regex);
@@ -1058,6 +1083,7 @@ def test_coherence_pooled_bench_qa_strict_fp_rate_documented():
     flagged = sum(1 for r in rows
                   if diagnose_coherence(r["answer_text"])["kind"] not in ("ok", "empty"))
     assert len(rows) >= 800, f"pooled STRICT sample shrunk unexpectedly ({len(rows)} rows; expected ~808)"
-    # current rate: 44/808 = 0.0545; ceiling at 0.07 leaves a tiny bit of headroom for fixture churn
-    assert flagged / len(rows) <= 0.07, \
+    # post round-2 rate: 9/808 = 0.011; ceiling at 0.02 leaves a tiny
+    # bit of headroom for fixture churn but fires loud on regressions.
+    assert flagged / len(rows) <= 0.02, \
         f"§3.1 FP rate on real STRICT regressed: {flagged}/{len(rows)} = {flagged/len(rows):.3f}"