fix(rules): helpless Dex-0 AC adds exactly -5 on flat-footed base; touch base strips full Dex mod when helpless (no negative-Dex double count)

tests/test_conformance_p1.py

@@ -328,8 +328,9 @@ def test_stunned_is_not_helpless() -> None:
 
 
 def test_helpless_dex_zero_replaces_a_native_dex_penalty() -> None:
-    # A Dex 8 (-1) helpless target: the -1 penalty gives way to the Dex-0 -5
-    # (adjustment -5 - (-1) = -4 on top of the flat-footed base).
+    # A Dex 8 (-1) helpless target: the flat-footed base already excludes
+    # ALL Dex (bonus and penalty alike), so effective Dex 0 adds exactly -5.
+    # The old formula added -5 - (-1) = -4, double-counting the Dex penalty.
     eng = _engine(
         [_combatant("atk"), _combatant("def", ac=14, dex=8)],
         [(0, 0), (0, 1)],
@@ -337,7 +338,68 @@ def test_helpless_dex_zero_replaces_a_native_dex_penalty() -> None:
     )
     _add_condition(eng._states[1], PARALYZED)
     result = eng.resolve_attack(eng._states[0], eng._states[1], _melee("atk"))
-    assert result.ac == 10  # 14 - 4
+    assert result.ac == 9  # 14 - 5
+
+
+def _touch(cid: str) -> AttackSpec:
+    return AttackSpec(
+        id=f"{cid}-touch",
+        name="touch",
+        kind="touch",
+        attack_bonus=5,
+        damage=[DamageComponent(formula=parse_dice("1d6"), types=["cold"])],
+    )
+
+
+def test_helpless_positive_dex_melee_ac_is_flat_footed_minus5() -> None:
+    # Dex 16 (+3): flat-footed base drops the +3 already; Dex-0 adds -5.
+    eng = _engine(
+        [_combatant("atk"), _combatant("def", ac=16, dex=16)],
+        [(0, 0), (0, 1)],
+        [10, 4],
+    )
+    _add_condition(eng._states[1], PARALYZED)
+    result = eng.resolve_attack(eng._states[0], eng._states[1], _melee("atk"))
+    assert result.ac == 11  # 16 - 5
+
+
+def test_helpless_positive_dex_touch_ac_strips_dex_then_minus5() -> None:
+    # Dex 16 (+3): touch base 16 includes the +3; effective Dex 0 strips it
+    # (16 - 3) and adds -5 -> 8.
+    eng = _engine(
+        [_combatant("atk"), _combatant("def", ac=16, dex=16)],
+        [(0, 0), (0, 1)],
+        [10, 4],
+    )
+    _add_condition(eng._states[1], PARALYZED)
+    result = eng.resolve_attack(eng._states[0], eng._states[1], _touch("atk"))
+    assert result.ac == 8
+
+
+def test_helpless_negative_dex_touch_ac_strips_penalty_then_minus5() -> None:
+    # Dex 8 (-1): touch base 14 includes the -1; effective Dex 0 replaces it
+    # (14 + 1) and adds -5 -> 10.
+    eng = _engine(
+        [_combatant("atk"), _combatant("def", ac=14, dex=8)],
+        [(0, 0), (0, 1)],
+        [10, 4],
+    )
+    _add_condition(eng._states[1], PARALYZED)
+    result = eng.resolve_attack(eng._states[0], eng._states[1], _touch("atk"))
+    assert result.ac == 10
+
+
+def test_flat_footed_negative_dex_touch_keeps_penalty_without_minus5() -> None:
+    # Control: a merely flat-footed (NOT helpless) Dex 8 target loses only a
+    # positive Dex bonus — the -1 stays on touch AC and no Dex-0 -5 applies.
+    eng = _engine(
+        [_combatant("atk"), _combatant("def", ac=14, dex=8)],
+        [(0, 0), (0, 1)],
+        [10, 4],
+    )
+    _add_condition(eng._states[1], CONDITIONS_BY_NAME["flat_footed"])
+    result = eng.resolve_attack(eng._states[0], eng._states[1], _touch("atk"))
+    assert result.ac == 14
 
 
 # ── B6: nauseated — single move action only, no casting ──────────────────────