feat(adr-0182): prior-state question guard — temporal-scope confuser refuses (confuser wrong 2->1, pair-tells ->0) (#480)

The "before/left" reading-rule lever. The microscope showed only the question-time
reading is cleanly achievable: "for N money = spend" is cue-precision-blocked (the
`for` cue is overloaded across train_sample -- `for $2`, `for 14 days`, `for 10 reps`
-- so a spend rule risks regressing train-0021/0003 and is the overfitting trap),
and the disguised-polarity cases already refuse via pooling. "left" is already handled
by loss verbs.

What ships: a question-scope guard. A question asking for a state *before* a stated
change ("How much did Lisa have before lunch?", gold 50) asks for a temporal point
the forward composers do not compute -- they derive the final/net state (50-20=30).
Until a question-time reader exists that is a refusal, never a guess at the wrong
point. target.asks_prior_state detects before/initially/originally/at first/to begin
with/to start with/at the start in the QUESTION CLAUSE only (the last `?`-sentence),
so body narrative does not trip it -- verified safe against train-0003 ("sells before
school starts"), 0010 ("had 20 initially, then lost 12"), 0028. `used to` is excluded
(the purpose infinitive "beads used to make a bracelet" is a false positive).
resolve_pooled refuses when asks_prior_state holds.

Result (sealed lane; chat/ does not import these -> serving 3/47/0 frozen):
- confuser wrong 2 -> 1 (only 0016 distractor-anchor-skip remains). temporal-scope
  category cleared (0 wrong / 2 refused). pair-tells 1 -> 0: 0020 ("before lunch")
  refuses while its minimal-pair twin 0021 ("left", gold 30) still solves the net --
  the discrimination the corpus is built to measure.
- genuine positives still 7 solved, 0 wrong.
- train_sample 3/47/0 and practice 3/47/0 byte-identical.
- 205 derivation/target/pool tests + 40 architectural invariants green.

Tests:
- test_adr_0182_pool.py TestPriorStateQuestionGuard: detector true/false edges
  (before-in-question vs before-in-body vs `used to make` false positive vs the
  `left` twin) + resolve_pooled refuses the before-question while the left-twin
  resolves forward to 30.
- test_adr_0163_f2_confusers.py: baseline wrong 2->1, pair_tells 1->0; new
  test_temporal_scope_does_not_misfire + test_before_left_minimal_pair_discriminated.

Stacked on #476 (pooling); merge #476 first. 0016 anchor-skip is the next lever.
Pairs with ADR-0163-F2 graduation amendment (#478).

generate/derivation/__init__.py

@@ -28,7 +28,7 @@ from generate.derivation.search import (
     multiplicative_candidates,
     search_multiplicative,
 )
-from generate.derivation.target import Target, extract_target
+from generate.derivation.target import Target, asks_prior_state, extract_target
 from generate.derivation.verify import (
     Resolution,
     SelfVerification,
@@ -49,6 +49,7 @@ __all__ = [
     "Target",
     "VALID_OPS",
     "accumulation_candidates",
+    "asks_prior_state",
     "candidate_chains",
     "classify_derivation",
     "clause_local_results",

generate/derivation/pool.py

@@ -33,6 +33,7 @@ from generate.derivation.accumulate import accumulation_candidates
 from generate.derivation.model import GroundedDerivation
 from generate.derivation.multistep import candidate_chains
 from generate.derivation.search import multiplicative_candidates
+from generate.derivation.target import asks_prior_state
 from generate.derivation.verify import Resolution, classify_derivation
 
 
@@ -63,7 +64,15 @@ def resolve_pooled(problem_text: str) -> Resolution | None:
 
     Refuses on no verifying candidate, on disagreement among the pool, or when the
     sole answer is produced only by commit-ineligible (``exempt``) readings.
+
+    ADR-0182 question-scope guard: a question asking for a *prior* state ("how much
+    did Lisa have **before** lunch?") asks for a temporal point the forward composers
+    do not compute — they derive the final/net state. Until a question-time reader
+    exists, that is a refusal, never a guess at the wrong point.
     """
+    if asks_prior_state(problem_text):
+        return None
+
     classified = [
         (kind, derivation)
         for derivation in pooled_candidates(problem_text)

generate/derivation/target.py

@@ -25,6 +25,7 @@ weaker prune and leans on completeness, or refuses.
 
 from __future__ import annotations
 
+import re
 from dataclasses import dataclass
 from typing import Final
 
@@ -37,6 +38,40 @@ from generate.math_roundtrip import _tokens
 _AGG_WORDS: Final[tuple[str, ...]] = ("total", "altogether", "combined", "sum")
 _AGG_PHRASES: Final[tuple[str, ...]] = ("in all", "in total")
 
+# ADR-0182 — prior-state question markers. A question that asks for a state *before*
+# a stated change ("how much did Lisa have **before** lunch?", "...**initially**?")
+# is asking for a temporal point the forward reader does not compute — it derives
+# the final/net state. Detected on the **question clause only**: "before"/"initially"
+# in the problem *body* is narrative ("sells before school starts", "had 20
+# initially, then lost 12") and must not trip this. ``used to`` is excluded — the
+# purpose infinitive ("beads used to make a bracelet") is a false positive, not a
+# prior-state cue. Lexeme-level (ADR-0165): it names markers, it does not parse the
+# question's grammar.
+_PRIOR_STATE_RE: Final[re.Pattern[str]] = re.compile(
+    r"\b(before|initially|originally|at first|to begin with|to start with|at the start)\b",
+    re.IGNORECASE,
+)
+_SENTENCE_SPLIT: Final[re.Pattern[str]] = re.compile(r"(?<=[.?!])\s+")
+
+
+def _question_clause(problem_text: str) -> str:
+    """The interrogative clause: the last ``?``-terminated sentence, else the last
+    sentence. Deterministic."""
+    sentences = [s for s in _SENTENCE_SPLIT.split(problem_text.strip()) if s.strip()]
+    if not sentences:
+        return problem_text
+    questions = [s for s in sentences if s.rstrip().endswith("?")]
+    return questions[-1] if questions else sentences[-1]
+
+
+def asks_prior_state(problem_text: str) -> bool:
+    """True iff the *question* asks for a state before a stated change (ADR-0182).
+
+    Question-clause-scoped so body narrative ("before school starts") does not trip
+    it. The forward reader computes the final state, so a prior-state question is a
+    refusal until a question-time reader exists — never a guess at the wrong point."""
+    return bool(_PRIOR_STATE_RE.search(_question_clause(problem_text)))
+
 
 @dataclass(frozen=True, slots=True)
 class Target:

tests/test_adr_0163_f2_confusers.py

@@ -30,8 +30,12 @@ from evals.gsm8k_math.confusers.v1.runner import (
 #     the spurious "for N coins" product disagrees with the accumulation reading)
 #     now refuse. wrong 5->2 (0016 needs anchor-skip; 0020 is temporal-scope).
 #     pair_tells 4->1 (0001/0003/0014 clear; 0020 remains).
-_BASELINE_WRONG = 2
-_BASELINE_PAIR_TELLS = 1
+#   2026-05-29 (ADR-0182 prior-state question guard): a question asking for a state
+#     *before* a stated change ("...before lunch?") is refused — the forward reader
+#     computes the net, the wrong temporal point. 0020 refuses; its 'left' twin 0021
+#     still solves. wrong 2->1 (only 0016 remains). pair_tells 1->0.
+_BASELINE_WRONG = 1
+_BASELINE_PAIR_TELLS = 0
 
 
 class TestSchema:
@@ -111,5 +115,21 @@ class TestProbeBaseline:
         assert disguised
         assert all(r.verdict != "wrong" for r in disguised)
 
+    def test_temporal_scope_does_not_misfire(self) -> None:
+        # ADR-0182 prior-state question guard: a "before <event>?" question is
+        # refused (the forward reader computes the net, the wrong temporal point).
+        # Fails loudly if the guard regresses (0020 would commit 30 again).
+        results = run_probe()
+        temporal = [r for r in results if r.category == "temporal-scope"]
+        assert temporal
+        assert all(r.verdict != "wrong" for r in temporal)
+
+    def test_before_left_minimal_pair_discriminated(self) -> None:
+        # 0020 ("before lunch") refuses; its twin 0021 ("left") solves the net.
+        # This is the pair-consistency win (the last surface-match tell cleared).
+        by_id = {r.case_id: r for r in run_probe()}
+        assert by_id["confuser-v1-0020"].verdict == "refused"
+        assert by_id["confuser-v1-0021"].verdict == "solved"
+
     def test_deterministic(self) -> None:
         assert summarize(run_probe()) == summarize(run_probe())

tests/test_adr_0182_pool.py

@@ -18,6 +18,7 @@ from __future__ import annotations
 from generate.derivation.accumulate import accumulation_candidates
 from generate.derivation.model import GroundedDerivation, Quantity, Step
 from generate.derivation.pool import resolve_pooled
+from generate.derivation.target import asks_prior_state
 from generate.derivation.verify import classify_derivation
 
 _DISTRACTOR_0014 = (
@@ -102,3 +103,43 @@ class TestResolvePooled:
         a = resolve_pooled(_CLEAN_ACCUMULATION)
         b = resolve_pooled(_CLEAN_ACCUMULATION)
         assert a is not None and b is not None and a.answer == b.answer
+
+
+_BEFORE_Q = "Lisa had 50 dollars. She spent 20 on lunch. How much money did Lisa have before lunch?"
+_LEFT_TWIN = "Lisa had 50 dollars. She spent 20 on lunch. How much money does Lisa have left?"
+
+
+class TestPriorStateQuestionGuard:
+    """ADR-0182 — a question asking for a *prior* state is refused (the forward
+    composers compute the final state, the wrong temporal point). Question-clause
+    scoped, so body narrative ('before school starts') does not trip it."""
+
+    def test_before_question_detected(self) -> None:
+        assert asks_prior_state(_BEFORE_Q) is True
+
+    def test_left_twin_not_detected(self) -> None:
+        # the minimal-pair twin asks for the net ('left') -> forward reading, solvable.
+        assert asks_prior_state(_LEFT_TWIN) is False
+
+    def test_before_in_body_not_detected(self) -> None:
+        # 'before' in narrative (not the question clause) must NOT trip the guard,
+        # or it would wrongly refuse train-0003 (gold 864, currently committed).
+        body_before = (
+            "The student council sells erasers in the morning before school starts. "
+            "There are 24 erasers in each box. If they sell 48 boxes, how many erasers?"
+        )
+        assert asks_prior_state(body_before) is False
+
+    def test_used_to_make_is_not_a_prior_marker(self) -> None:
+        # the purpose infinitive 'used to make' is a false positive guarded against.
+        assert asks_prior_state("If 50 beads are used to make one bracelet, how many bracelets?") is False
+
+    def test_prior_state_question_refuses(self) -> None:
+        # the forward reading computes 50-20=30 (the net); the question asks the
+        # pre-change state -> refuse, not commit 30.
+        assert resolve_pooled(_BEFORE_Q) is None
+
+    def test_left_twin_still_resolves_forward(self) -> None:
+        # discrimination: the twin asking 'left' commits the forward net (30).
+        resolution = resolve_pooled(_LEFT_TWIN)
+        assert resolution is not None and resolution.answer == 30.0