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)

src/pf1e_simulator/combat.py

@@ -2707,9 +2707,11 @@ class CombatEngine:
         PF1e (CRB): a prone defender takes -4 AC against melee attacks but
         gains +4 AC against ranged attacks; a helpless defender (paralyzed,
         asleep, unconscious, helpless) has an effective Dexterity score of 0,
-        so its whole Dex modifier gives way to the Dex-0 penalty (-5) —
-        flat-footed AC already drops a positive Dex bonus, a native Dex
-        penalty must still be replaced."""
+        so its whole Dex modifier gives way to the Dex-0 penalty (-5). The
+        flat-footed base already excludes ALL Dex (bonus and penalty alike),
+        so the mod is exactly -5 there; on the touch base the stored Dex
+        modifier is stripped at the base (see resolve_attack) before this
+        -5 is added."""
         mods = self._stat_modifiers(target, "ac")
         if self._has_condition_named(target, "prone"):
             mods.append(
@@ -2718,8 +2720,7 @@ class CombatEngine:
                 )
             )
         if self._is_helpless(target):
-            dex_penalty = min(0, target.combatant.abilities.dex_mod)
-            mods.append(StatModifier(target="ac", value=_DEX_ZERO_MOD - dex_penalty))
+            mods.append(StatModifier(target="ac", value=_DEX_ZERO_MOD))
         return mods
 
     def resolve_attack(
@@ -2804,9 +2805,14 @@ class CombatEngine:
             ):
                 base_ac = full_ac_base
             elif denies_dex:
-                base_ac = (
-                    target.combatant.ac.touch - max(0, target.combatant.abilities.dex_mod)
-                )
+                # A flat-footed defender loses only a POSITIVE Dex bonus (a
+                # Dex penalty stays on touch AC); a HELPLESS defender has an
+                # effective Dex score of 0, so its whole stored Dex modifier
+                # is stripped here and the exact -5 Dex-0 penalty is added by
+                # _attack_ac_mods.
+                dex_mod = target.combatant.abilities.dex_mod
+                strip = dex_mod if self._is_helpless(target) else max(0, dex_mod)
+                base_ac = target.combatant.ac.touch - strip
             else:
                 base_ac = target.combatant.ac.touch
         else: