feat(combat): add concealment miss chance, sneak attack, and Precise Shot

README.md

@@ -410,16 +410,41 @@ Règles modélisées :
   chemin de la RD. La résistance énergétique s'applique au dégât final (même étape
   que la RD), y compris aux dégâts de sorts et aux composantes énergétiques des
   armes.
+- Concealment (chance de rater) : les conditions `blurred` (20 %, sort flou) et
+  `displaced` (50 %, concealment total) portent un champ `miss_chance` ; quand la
+  cible en porte une, après la touche et la confirmation de critique, le moteur
+  tire un d100 : si `d100 ≤ miss_chance`, l'attaque rate complètement (aucun
+  dégât, pas de critique, deed non consommé — journalisé « concealment »). Une
+  cible avec concealment ne peut pas être la victime d'une attaque sournoise.
+- Attaque sournoise : un combattant avec la capacité « Sneak Attack » inflige des
+  d6 de dégâts de précision ((niveau + 1) // 2 dés : 1d6 au niveau 1, 2d6 au
+  niveau 3…) si la cible est flanquée (attaque de mêlée uniquement) ou privée de
+  son bonus de Dextérité à la CA (condition `denies_dex_to_ac` ; mêlée, ou
+  attaque à distance à ≤ 30 ft). Les dés sont jetés avec le RNG du moteur et
+  ajoutés APRÈS le multiplicateur de critique (la précision n'est jamais
+  multipliée) et AVANT la RD et les résistances énergétiques ; jamais contre une
+  cible avec concealment.
+- Tirer dans une mêlée / Precise Shot : toute attaque à distance (kind `ranged`
+  ou `touch` avec incrément) contre une cible engagée dans une mêlée subit −4 au
+  jet d'attaque ET au jet de confirmation (la cible est « engagée » quand un
+  ennemi actif autre que l'attaquant, doté d'une arme de mêlée, menace ses
+  cases) ; la pénalité tombe à −2 si la cible ou l'adversaire menaçant est à
+  ≥ 10 ft (2 cases) de l'attaquant. Le don « Precise Shot » annule la pénalité.
+  Les attaques de mêlée ne sont pas concernées.
+- Couvert : seul le couvert standard (+4, terrain et couvert mou des créatures)
+  est modélisé ; le couvert partiel (+2) et le couvert amélioré (+8) ne sont PAS
+  modélisés.
 - Invocation : les créatures invoquées agissent (calées sur la case d'initiative de
   leur conjurateur via `_build_round_order`) puis expirent après leur `summon_duration`
   (`_expire_summons` décrémente puis retire).
-- Conditions effectives : 18 conditions prédéfinies (`conditions.py`). Leurs drapeaux
+- Conditions effectives : 23 conditions prédéfinies (`conditions.py`). Leurs drapeaux
   comportementaux sont appliqués par le moteur : `cant_act` (étourdi, paralysé, dazed,
   endormi) annule le tour ; `cant_attack` (nauséeux) n'autorise qu'une unique action
   simple et bloque toute attaque / manœuvre ; `staggered` restreint à une action
   simple (pas d'attaque à outrance) ; `cant_move` bloque le déplacement ;
   `denies_dex_to_ac` (à plat ventre, paralysé…) fait perdre le bonus de Dextérité à
-  la CA (CA flat-footed). À plat ventre : −4 CA et −4 aux attaques à distance.
+  la CA (CA flat-footed) ; `miss_chance` (flou 20 %, déplacement 50 %) impose la
+  chance de rater du concealment. À plat ventre : −4 CA et −4 aux attaques à distance.
   Agrippé : −4 Dextérité, −2 attaque/CA/Réflexes, sans déplacement ni AoO.
 - Manœuvres de combat : trip, disarm, bull_rush, sunder, grapple, escape,
   overrun, dirty trick, steal, reposition et drag sont modélisées, chacune
@@ -496,7 +521,10 @@ Règles modélisées :
     spells (résumés enrichis du registre : name, level, school, range_ft,
     save, dc, summary, half_on_save, save_negates (E4)),
     spell_resistance (int), resistances {type: montant}, immunities
-    (tuple triée des types immunisés).
+    (tuple triée des types immunisés), sneak_dice (dés de précision disponibles :
+    (niveau + 1) // 2 avec « Sneak Attack », sinon 0), engaged_in_melee (bool —
+    une cible engagée dans une mêlée, signal pour le tir dans la mêlée et
+    l'attaque sournoise).
   - Par paire combattant actif × cible : target_index, distance_ft, weapon_for,
     range_penalty, can_charge, can_step5_to_attack, has_line_of_effect,
     flanking, movement_cost_ft, target_threatens_me, enemies_threatening_me.
@@ -504,9 +532,9 @@ Règles modélisées :
     threatened (grille bool des cases menacées par les ennemis),
     terrain_semantics (un dict par type de terrain : type, move_cost,
     blocks_los, cover), condition_definitions (C2 : tuple trié de (nom,
-    {mods, flags, speed_mult}) — définitions complètes des 21 conditions de
+    {mods, flags, speed_mult, miss_chance}) — définitions complètes des 23
-    CONDITIONS_BY_NAME pour que la LLM interprète les drapeaux et
+    conditions de CONDITIONS_BY_NAME pour que la LLM interprète les drapeaux,
-    modificateurs).
+    les modificateurs et les chances de rater (concealment)).
   Les helpers publics du moteur (L5) sont désormais embarqués EN DONNÉES dans
   le snapshot (`threatened`, `terrain_semantics`, `movement_cost_ft`,
   `target_threatens_me`, `enemies_threatening_me`) — une `LLMPolicy` ne peut
@@ -563,7 +591,7 @@ la lecture mais non appliquée dans la résolution.
   enhancement…) gardent la valeur la plus élevée. Les pénalités suivent les
   mêmes règles. Fondation pour sorts, conditions, dons et capacités de classe.
 - `conditions.py` — conditions PF1e : `Condition` (dataclass avec
-  modificateurs + flags comportementaux) et 18 conditions prédéfinies
+  modificateurs + flags comportementaux + `miss_chance`) et 23 conditions prédéfinies
   (shaken, sickened, fatigued, exhausted, entangled, dazzled, blinded,
   deafened, flat-footed, prone, stunned, paralyzed, nauseated, dazed,
   staggered, frightened, panicked, cowering). Les modificateurs sont intégrés

src/pf1e_simulator/combat.py

@@ -138,6 +138,11 @@ _CHARGE_MIN_CELLS = 2  # PF1e: charge must move at least 10 ft (2 squares)
 _UP_CLOSE_RANGE_FT = 30  # PF1e: Up Close and Deadly works within 30 ft
 # PF1e: Point-Blank Shot grants +1/+1 within 30 ft with ranged weapons
 _POINT_BLANK_RANGE_FT = 30
+_FIRING_MELEE_PENALTY = -4  # PF1e: ranged attack into melee
+_FIRING_MELEE_REDUCED_PENALTY = -2  # PF1e: -2 when the melee is 10+ ft away
+_FIRING_MELEE_SAFE_FT = 10  # PF1e: 2 cells (10 ft) from attacker = reduced penalty
+_SNEAK_ATTACK_FEATURE = "Sneak Attack"  # PF1e: rogue class feature (precision dice)
+_PRECISE_SHOT_FEATURE = "Precise Shot"  # PF1e: feat negating firing-into-melee penalty
 _SAVE_DESCRIPTOR_CONDITIONS = frozenset({
     "fear", "cold", "electricity", "fey", "divination", "poison", "disease",
     "mind_affecting",
@@ -236,6 +241,7 @@ def _condition_definition_dict(cond: Condition) -> dict[str, object]:
         "mods": [_stat_modifier_dict(m) for m in cond.modifiers],
         "flags": flags,
         "speed_mult": cond.speed_mult,
+        "miss_chance": cond.miss_chance,
     }
 
 
@@ -395,6 +401,7 @@ class AttackResult:
     flank_bonus: int = 0
     high_ground_bonus: int = 0
     base_bonus: int = 0
+    melee_penalty: int = 0
 
 
 @dataclass(frozen=True)
@@ -845,6 +852,12 @@ class CombatEngine:
             "spell_resistance": state.combatant.spell_resistance,
             "resistances": dict(state.combatant.resistances),
             "immunities": tuple(state.combatant.immunities),
+            "sneak_dice": (
+                (state.combatant.level + 1) // 2
+                if self._has_feat(state, _SNEAK_ATTACK_FEATURE)
+                else 0
+            ),
+            "engaged_in_melee": self._engaged_in_melee(state),
         }
 
     def _pair_snapshot(
@@ -1311,6 +1324,11 @@ class CombatEngine:
             else 0
         )
         base_bonus = bonus_override if bonus_override is not None else weapon.attack_bonus
+        fim_penalty = (
+            self._firing_into_melee_penalty(attacker, target)
+            if self._is_ranged_attack(weapon)
+            else 0
+        )
         atk_mods = self._stat_modifiers(
             attacker, "attack", weapon_name=weapon.name, weapon=weapon, dist_ft=dist_ft
         )
@@ -1318,7 +1336,10 @@ class CombatEngine:
             atk_mods.append(StatModifier(target="attack", value=-4))
         attack_mod = resolve_modifiers(atk_mods)
         pa_amt = self._power_attack_amt(attacker) if weapon.kind == "melee" else 0
-        total = roll + base_bonus + penalty + flank + high_ground + attack_mod - pa_amt
+        total = (
+            roll + base_bonus + penalty + flank + high_ground + attack_mod - pa_amt
+            + fim_penalty
+        )
         # Check if target denies DEX to AC (flat-footed)
         denies_dex = self.has_condition_flag(target, "denies_dex_to_ac")
         full_ac_base = (
@@ -1358,30 +1379,17 @@ class CombatEngine:
         ):
             ac += _COVER_AC_BONUS
         hit = roll == _NATURAL_TWENTY or (roll != _NATURAL_ONE and total >= ac)
-        crit = False
         damage = 0
+        concealment_miss = False
+        crit = False
         if hit:
-            if roll != _NATURAL_ONE and roll >= weapon.crit_range:
+            crit, concealment_miss, damage = self._resolve_hit_damage(
-                confirm = self._rng.d20()
+                attacker, target, weapon, roll=roll, ac=ac, base_bonus=base_bonus,
-                confirm_total = (
+                penalty=penalty, flank=flank, high_ground=high_ground,
-                    confirm + base_bonus + penalty + flank + high_ground + attack_mod - pa_amt
+                attack_mod=attack_mod, pa_amt=pa_amt, fim_penalty=fim_penalty,
-                )
+                dist_ft=dist_ft, denies_dex=denies_dex,
-                crit = confirm != _NATURAL_ONE and confirm_total >= ac
-            dmg_mods = self._stat_modifiers(
-                attacker, "damage", weapon_name=weapon.name, weapon=weapon, dist_ft=dist_ft
-            )
-            damage = sum(c.formula.roll(self._rng) for c in weapon.damage) + weapon.damage_bonus
-            damage += resolve_modifiers(dmg_mods)
-            damage += pa_amt * 2 if weapon.kind == "melee" else 0
-            if crit:
-                damage *= weapon.crit_mult
-            damage = self._apply_dr(damage, weapon, target)
-            weapon_types = frozenset(
-                t for comp in weapon.damage for t in comp.types
-            )
-            damage = self._apply_energy_resistance(
-                damage, weapon_types, target
             )
+        if not concealment_miss:
             target.hp -= damage
             damage = self._consume_up_close_and_deadly(
                 attacker, target, weapon, dist_ft, damage, hit=hit
@@ -1389,7 +1397,155 @@ class CombatEngine:
         return AttackResult(
             hit=hit, crit=crit, damage=damage, roll=roll, total=total, ac=ac,
             penalty=penalty, flank_bonus=flank, high_ground_bonus=high_ground,
-            base_bonus=base_bonus,
+            base_bonus=base_bonus, melee_penalty=fim_penalty,
+        )
+
+    def _resolve_hit_damage(
+        self,
+        attacker: CombatantState,
+        target: CombatantState,
+        weapon: AttackSpec,
+        *,
+        roll: int,
+        ac: int,
+        base_bonus: int,
+        penalty: int,
+        flank: int,
+        high_ground: int,
+        attack_mod: int,
+        pa_amt: int,
+        fim_penalty: int,
+        dist_ft: int,
+        denies_dex: bool,
+    ) -> tuple[bool, bool, int]:
+        """Resolve a successful attack roll: crit confirm, concealment miss
+        chance, sneak attack dice, then damage (PF1e order).
+
+        Returns ``(crit, concealment_miss, damage)``. Sneak precision dice are
+        added after the crit multiplier and before DR / energy resistance.
+        """
+        crit = False
+        if roll != _NATURAL_ONE and roll >= weapon.crit_range:
+            confirm = self._rng.d20()
+            confirm_total = (
+                confirm + base_bonus + penalty + flank + high_ground
+                + attack_mod - pa_amt + fim_penalty
+            )
+            crit = confirm != _NATURAL_ONE and confirm_total >= ac
+        concealment = self._concealment_chance(target)
+        if concealment > 0:
+            pct = self._rng.d100()
+            missed = pct <= concealment
+            self._log(
+                f"round {self._current_round} {attacker.combatant.id}: "
+                f"concealment vs {target.combatant.id}: "
+                f"d100({pct}) {'<=' if missed else '>'} {concealment}% "
+                f"— attack {'misses' if missed else 'lands'}"
+            )
+            if missed:
+                return False, True, 0
+        sneak_total = 0
+        sneak_dice = self._sneak_attack_dice(
+            attacker, target, weapon, dist_ft=dist_ft,
+            denies_dex=denies_dex, concealment=concealment,
+        )
+        if sneak_dice > 0:
+            sneak_total = sum(self._rng.roll_die(6) for _ in range(sneak_dice))
+            self._log(
+                f"round {self._current_round} {attacker.combatant.id}: "
+                f"sneak attack vs {target.combatant.id}: "
+                f"{sneak_dice}d6 = {sneak_total} precision damage"
+            )
+        dmg_mods = self._stat_modifiers(
+            attacker, "damage", weapon_name=weapon.name, weapon=weapon, dist_ft=dist_ft
+        )
+        damage = (
+            sum(c.formula.roll(self._rng) for c in weapon.damage) + weapon.damage_bonus
+        )
+        damage += resolve_modifiers(dmg_mods)
+        damage += pa_amt * 2 if weapon.kind == "melee" else 0
+        if crit:
+            damage *= weapon.crit_mult
+        damage += sneak_total
+        damage = self._apply_dr(damage, weapon, target)
+        weapon_types = frozenset(t for comp in weapon.damage for t in comp.types)
+        damage = self._apply_energy_resistance(damage, weapon_types, target)
+        return crit, False, damage
+
+    def _concealment_chance(self, target: CombatantState) -> int:
+        """Highest miss chance (%) among the target's active concealment conditions."""
+        chances = [ac.condition.miss_chance for ac in target.active_conditions]
+        chances += [cond.miss_chance for cond in target.conditions]
+        return max((c for c in chances if c > 0), default=0)
+
+    def _sneak_attack_dice(
+        self,
+        attacker: CombatantState,
+        target: CombatantState,
+        weapon: AttackSpec,
+        *,
+        dist_ft: int,
+        denies_dex: bool,
+        concealment: int,
+    ) -> int:
+        """Sneak attack d6 count for this swing (0 when the sneak does not apply).
+
+        PF1e: precision damage when the target is flanked (melee only) or
+        denied its Dex bonus to AC (melee, or ranged within 30 ft); dice =
+        (level + 1) // 2; concealment denies the sneak attack entirely.
+        """
+        if concealment > 0 or not self._has_feat(attacker, _SNEAK_ATTACK_FEATURE):
+            return 0
+        dice = (attacker.combatant.level + 1) // 2
+        is_melee = weapon.kind == "melee"
+        if is_melee and self._flanking_bonus(attacker, target) > 0:
+            return dice
+        if denies_dex and (
+            is_melee
+            or (self._is_ranged_attack(weapon) and dist_ft <= _POINT_BLANK_RANGE_FT)
+        ):
+            return dice
+        return 0
+
+    def _firing_into_melee_penalty(
+        self, attacker: CombatantState, target: CombatantState
+    ) -> int:
+        """PF1e firing into melee: -4 on a ranged attack whose target is
+        engaged in melee, reduced to -2 when the target or every threatening
+        opponent stands 10+ ft from the attacker. Precise Shot removes it.
+
+        The target is engaged when an active enemy of the target (not the
+        attacker itself) threatens the target's occupied cells with a melee
+        weapon.
+        """
+        if self._has_feat(attacker, _PRECISE_SHOT_FEATURE):
+            return 0
+        threats = [
+            s
+            for s in self._states
+            if s is not attacker
+            and s.active
+            and s.side != target.side
+            and self.threatened_squares(s) & target.occupied_cells()
+        ]
+        if not threats:
+            return 0
+        if self.creature_distance(attacker, target) * _SQUARE_FT >= _FIRING_MELEE_SAFE_FT:
+            return _FIRING_MELEE_REDUCED_PENALTY
+        for threat in threats:
+            dist = self.creature_distance(attacker, threat) * _SQUARE_FT
+            if dist >= _FIRING_MELEE_SAFE_FT:
+                return _FIRING_MELEE_REDUCED_PENALTY
+        return _FIRING_MELEE_PENALTY
+
+    def _engaged_in_melee(self, state: CombatantState) -> bool:
+        """True when an active enemy with a melee weapon threatens this
+        combatant's occupied cells (same threat machinery as AoO/flanking)."""
+        occupied = state.occupied_cells()
+        return any(
+            self.threatened_squares(s) & occupied
+            for s in self._states
+            if s is not state and s.active and s.side != state.side
         )
 
     def _consume_up_close_and_deadly(
@@ -3355,10 +3511,11 @@ class CombatEngine:
         high_ground_str = (
             f"+{result.high_ground_bonus}(high)" if result.high_ground_bonus else ""
         )
+        melee_str = f"{result.melee_penalty}(melee)" if result.melee_penalty else ""
         bonus_str = (
-            f"{result.base_bonus}{result.penalty:+d}{flank_str}{high_ground_str}"
+            f"{result.base_bonus}{result.penalty:+d}{flank_str}{high_ground_str}{melee_str}"
             if result.penalty
-            else f"{result.base_bonus}{flank_str}{high_ground_str}"
+            else f"{result.base_bonus}{flank_str}{high_ground_str}{melee_str}"
         )
         line = (
             f"round {self._current_round} {attacker.combatant.id}: {label} "

src/pf1e_simulator/conditions.py

@@ -37,6 +37,7 @@ class Condition:
     cant_aoo: bool = False
     must_flee: bool = False
     speed_mult: float = 1.0
+    miss_chance: int = 0
 
 
 # ── Fear conditions ──────────────────────────────────────────────────────────
@@ -253,6 +254,19 @@ STAGGERED = Condition(
     name="staggered",
 )
 
+# ── Concealment conditions ───────────────────────────────────────────────────
+# Blurred (blur spell): concealment — 20% miss chance on attacks (CRB)
+BLURRED = Condition(
+    name="blurred",
+    miss_chance=20,
+)
+
+# Displaced (displacement spell): total concealment — 50% miss chance (CRB)
+DISPLACED = Condition(
+    name="displaced",
+    miss_chance=50,
+)
+
 # ── Registry ─────────────────────────────────────────────────────────────────
 CONDITIONS_BY_NAME: dict[str, Condition] = {
     c.name: c
@@ -260,6 +274,6 @@ CONDITIONS_BY_NAME: dict[str, Condition] = {
         SHAKEN, SICKENED, FATIGUED, EXHAUSTED, ENTANGLED, DAZZLED,
         BLINDED, DEAFENED, FLAT_FOOTED, PRONE, STUNNED, PARALYZED,
         NAUSEATED, DAZED, STAGGERED, FRIGHTENED, PANICKED, COWERING,
-        ASLEEP, GRAPPLED, PINNED,
+        ASLEEP, GRAPPLED, PINNED, BLURRED, DISPLACED,
     ]
 }

src/pf1e_simulator/rng.py

@@ -32,6 +32,10 @@ class Rng(Protocol):
         """Return roll_die(20)."""
         ...
 
+    def d100(self) -> int:
+        """Return roll_die(100)."""
+        ...
+
     def choice_index(self, n: int) -> int:
         """Return a uniform integer in 0..n-1 for deterministic tie-breaks."""
         ...
@@ -49,6 +53,9 @@ class SeededRng:
     def d20(self) -> int:
         return self.roll_die(20)
 
+    def d100(self) -> int:
+        return self.roll_die(100)
+
     def choice_index(self, n: int) -> int:
         return self._rng.randrange(n)
 
@@ -56,7 +63,7 @@ class SeededRng:
 class ScriptedRng:
     """Rng that pops predetermined values from a queue.
 
-    Each call to roll_die, d20, or choice_index consumes one value.
+    Each call to roll_die, d20, d100, or choice_index consumes one value.
     Raises RngExhaustedError when the queue is empty.
     """
 
@@ -71,6 +78,9 @@ class ScriptedRng:
     def d20(self) -> int:
         return self.roll_die(20)
 
+    def d100(self) -> int:
+        return self.roll_die(100)
+
     def choice_index(self, _n: int) -> int:
         if not self._queue:
             raise RngExhaustedError(_EXHAUSTED_MSG)

tests/test_accuracy_rules.py

@@ -0,0 +1,432 @@
+"""Concealment miss chance, sneak attack, and firing into melee (Package P2)."""
+from __future__ import annotations
+
+from pf1e_simulator.abilities import AbilitySpec
+from pf1e_simulator.combat import CombatantState, CombatEngine
+from pf1e_simulator.conditions import CONDITIONS_BY_NAME
+from pf1e_simulator.dice import parse_dice
+from pf1e_simulator.effects import ActiveCondition
+from pf1e_simulator.models import (
+    AbilityScores,
+    ACProfile,
+    AttackSpec,
+    Combatant,
+    DamageComponent,
+    Saves,
+)
+from pf1e_simulator.rng import ScriptedRng
+from tests.test_observation_enriched import _snapshot, make_grid, make_state
+
+
+def _melee(name: str, attack_bonus: int = 5) -> AttackSpec:
+    return AttackSpec(
+        id=f"{name}-sword",
+        name="short sword",
+        kind="melee",
+        attack_bonus=attack_bonus,
+        damage=[DamageComponent(formula=parse_dice("1d6"), types=["slashing"])],
+    )
+
+
+def _bow(name: str, attack_bonus: int = 5) -> AttackSpec:
+    return AttackSpec(
+        id=f"{name}-bow",
+        name="short bow",
+        kind="ranged",
+        attack_bonus=attack_bonus,
+        damage=[DamageComponent(formula=parse_dice("1d6"), types=["piercing"])],
+        range_increment_ft=60,
+    )
+
+
+def _combatant(
+    id_: str,
+    *,
+    level: int = 1,
+    ac: int = 10,
+    attacks: tuple[AttackSpec, ...] = (),
+    features: tuple[str, ...] = (),
+) -> Combatant:
+    return Combatant(
+        id=id_,
+        name=id_,
+        level=level,
+        abilities=AbilityScores(
+            str_score=10, dex_score=10, con_score=10,
+            int_score=10, wis_score=10, cha_score=10,
+        ),
+        ac=ACProfile(total=ac, touch=ac, flat_footed=ac),
+        bab=1,
+        initiative_mod=0,
+        speed_land_ft=30,
+        hp_max=100,
+        saves=Saves(fort=0, ref=0, will=0),
+        attacks=list(attacks) or [_melee(id_)],
+        features=[AbilitySpec(name=f, category="class") for f in features],
+    )
+
+
+def _engine(
+    combatants: list[Combatant],
+    positions: list[tuple[int, int]],
+    sides: list[str],
+    rng: list[int],
+) -> CombatEngine:
+    states = [
+        make_state(c, side, pos)
+        for c, side, pos in zip(combatants, sides, positions, strict=True)
+    ]
+    return CombatEngine(ScriptedRng(rng), make_grid(), states)
+
+
+def _add_condition(state: CombatantState, name: str, rounds: int = 5) -> None:
+    state.active_conditions.append(
+        ActiveCondition(
+            condition=CONDITIONS_BY_NAME[name],
+            rounds_left=rounds,
+            source="test",
+        )
+    )
+
+
+# ── Rule A: concealment miss chance ──────────────────────────────────────────
+
+
+def test_concealment_blur_misses_on_low_d100() -> None:
+    eng = _engine(
+        [_combatant("atk"), _combatant("tgt")],
+        [(0, 0), (0, 1)],
+        ["players", "monsters"],
+        [15, 10],
+    )
+    a, t = eng._states
+    _add_condition(t, "blurred")
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.hit is True
+    assert result.damage == 0
+    assert t.hp == 100
+    assert any("concealment" in line for line in eng._transcript)
+
+
+def test_concealment_blur_lands_on_high_d100() -> None:
+    eng = _engine(
+        [_combatant("atk"), _combatant("tgt")],
+        [(0, 0), (0, 1)],
+        ["players", "monsters"],
+        [15, 50, 4],
+    )
+    a, t = eng._states
+    _add_condition(t, "blurred")
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.hit is True
+    assert result.damage == 4
+    assert t.hp == 96
+
+
+def test_total_concealment_triggers_at_50() -> None:
+    eng = _engine(
+        [_combatant("atk"), _combatant("tgt")],
+        [(0, 0), (0, 1)],
+        ["players", "monsters"],
+        [15, 50],
+    )
+    a, t = eng._states
+    _add_condition(t, "displaced")
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.hit is True
+    assert result.damage == 0
+    assert t.hp == 100
+
+
+def test_concealment_denies_sneak_attack() -> None:
+    sneak = _combatant("atk", level=3, features=("Sneak Attack",))
+    eng = _engine(
+        [sneak, _combatant("tgt")],
+        [(0, 0), (0, 1)],
+        ["players", "monsters"],
+        [15, 90, 3],
+    )
+    a, t = eng._states
+    _add_condition(t, "flat_footed")
+    _add_condition(t, "blurred")
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.damage == 3
+    assert t.hp == 97
+    assert not any("sneak" in line for line in eng._transcript)
+
+
+def test_concealment_miss_does_not_consume_deed() -> None:
+    eng = _engine(
+        [
+            _combatant("atk", attacks=(_bow("atk", attack_bonus=15),)),
+            _combatant("tgt"),
+        ],
+        [(0, 0), (0, 2)],
+        ["players", "monsters"],
+        [15, 5],
+    )
+    a, t = eng._states
+    a.deed_up_close_and_deadly = True
+    _add_condition(t, "blurred")
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.damage == 0
+    assert t.hp == 100
+    assert a.deed_up_close_and_deadly is True
+
+
+# ── Rule B: sneak attack ─────────────────────────────────────────────────────
+
+
+def test_sneak_flanked_melee_dice_count() -> None:
+    rogue = _combatant("rogue", level=5, features=("Sneak Attack",))
+    eng = _engine(
+        [rogue, _combatant("tgt"), _combatant("ally")],
+        [(0, 0), (0, 1), (0, 2)],
+        ["players", "monsters", "players"],
+        [15, 2, 3, 4, 5],
+    )
+    a, t, _ally = eng._states
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.total == 22
+    assert result.damage == 14
+    assert t.hp == 86
+    assert any("sneak attack" in line and "3d6" in line for line in eng._transcript)
+
+
+def test_sneak_not_multiplied_on_crit() -> None:
+    rogue = _combatant("rogue", level=3, features=("Sneak Attack",))
+    weapon = AttackSpec(
+        id="rogue-sword",
+        name="short sword",
+        kind="melee",
+        attack_bonus=5,
+        damage=[DamageComponent(formula=parse_dice("1d6"), types=["slashing"])],
+        crit_range=20,
+        crit_mult=2,
+    )
+    eng = _engine(
+        [rogue, _combatant("tgt")],
+        [(0, 0), (0, 1)],
+        ["players", "monsters"],
+        [20, 20, 6, 6, 2],
+    )
+    a, t = eng._states
+    _add_condition(t, "flat_footed")
+    result = eng.resolve_attack(a, t, weapon)
+    assert result.crit is True
+    assert result.damage == 16
+    assert t.hp == 84
+
+
+def test_sneak_ranged_within_30ft() -> None:
+    rogue = _combatant(
+        "rogue", level=1, features=("Sneak Attack",), attacks=(_bow("rogue"),)
+    )
+    eng = _engine(
+        [rogue, _combatant("tgt")],
+        [(0, 0), (0, 4)],
+        ["players", "monsters"],
+        [15, 4, 3],
+    )
+    a, t = eng._states
+    _add_condition(t, "flat_footed")
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.damage == 7
+    assert t.hp == 93
+
+
+def test_sneak_ranged_beyond_30ft_denied() -> None:
+    rogue = _combatant(
+        "rogue", level=1, features=("Sneak Attack",), attacks=(_bow("rogue"),)
+    )
+    eng = _engine(
+        [rogue, _combatant("tgt")],
+        [(0, 0), (0, 7)],
+        ["players", "monsters"],
+        [15, 3],
+    )
+    a, t = eng._states
+    _add_condition(t, "flat_footed")
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.damage == 3
+    assert t.hp == 97
+    assert not any("sneak" in line for line in eng._transcript)
+
+
+def test_sneak_denied_dex_melee() -> None:
+    rogue = _combatant("rogue", level=1, features=("Sneak Attack",))
+    eng = _engine(
+        [rogue, _combatant("tgt")],
+        [(0, 0), (0, 1)],
+        ["players", "monsters"],
+        [15, 2, 3],
+    )
+    a, t = eng._states
+    _add_condition(t, "flat_footed")
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.damage == 5
+    assert t.hp == 95
+
+
+def test_no_sneak_without_feature() -> None:
+    eng = _engine(
+        [_combatant("atk"), _combatant("tgt")],
+        [(0, 0), (0, 1)],
+        ["players", "monsters"],
+        [15, 3],
+    )
+    a, t = eng._states
+    _add_condition(t, "flat_footed")
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.damage == 3
+    assert not any("sneak" in line for line in eng._transcript)
+
+
+# ── Rule C: firing into melee / Precise Shot ─────────────────────────────────
+
+
+def _firing_setup(rng: list[int], *, precise: bool = False) -> CombatEngine:
+    archer = _combatant(
+        "archer",
+        ac=99,
+        attacks=(_bow("archer", attack_bonus=8),),
+        features=("Precise Shot",) if precise else (),
+    )
+    tgt = _combatant("tgt", ac=15, attacks=(_bow("tgt"),))
+    guard = _combatant("guard", ac=99)
+    return _engine(
+        [archer, tgt, guard],
+        [(0, 0), (0, 1), (1, 1)],
+        ["players", "monsters", "players"],
+        rng,
+    )
+
+
+def test_firing_into_melee_minus4() -> None:
+    eng = _firing_setup([10])
+    a, t, _g = eng._states
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.total == 14
+    assert result.melee_penalty == -4
+    assert result.hit is False
+    assert t.hp == 100
+
+
+def test_firing_into_melee_minus2_when_target_10ft_away() -> None:
+    archer = _combatant("archer", ac=99, attacks=(_bow("archer", attack_bonus=8),))
+    tgt = _combatant("tgt", ac=15, attacks=(_bow("tgt"),))
+    guard = _combatant("guard", ac=99)
+    eng = _engine(
+        [archer, tgt, guard],
+        [(0, 0), (0, 2), (0, 3)],
+        ["players", "monsters", "players"],
+        [9, 3],
+    )
+    a, t, _g = eng._states
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.total == 15
+    assert result.melee_penalty == -2
+    assert result.hit is True
+    assert result.damage == 3
+
+
+def test_precise_shot_negates_penalty() -> None:
+    eng = _firing_setup([10, 3], precise=True)
+    a, t, _g = eng._states
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.total == 18
+    assert result.melee_penalty == 0
+    assert result.hit is True
+    assert result.damage == 3
+
+
+def test_melee_attack_unaffected_by_firing_rule() -> None:
+    eng = _engine(
+        [_combatant("atk"), _combatant("tgt"), _combatant("ally")],
+        [(0, 0), (0, 2), (0, 3)],
+        ["players", "monsters", "players"],
+        [15, 3],
+    )
+    a, t, _al = eng._states
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.melee_penalty == 0
+    assert result.total == 20
+
+
+def test_firing_into_melee_shown_in_transcript() -> None:
+    eng = _firing_setup([10])
+    a, t, _g = eng._states
+    eng._single_attack(a, t, a.combatant.attacks[0])
+    line = [ln for ln in eng._transcript if "short bow" in ln][-1]
+    assert "8-4(melee)=14" in line
+    assert "MISS" in line
+
+
+def test_firing_into_melee_applies_to_crit_confirm() -> None:
+    archer = _combatant(
+        "archer",
+        ac=99,
+        attacks=(
+            AttackSpec(
+                id="archer-bow",
+                name="short bow",
+                kind="ranged",
+                attack_bonus=8,
+                damage=[
+                    DamageComponent(formula=parse_dice("1d6"), types=["piercing"])
+                ],
+                crit_range=20,
+                range_increment_ft=60,
+            ),
+        ),
+    )
+    tgt = _combatant("tgt", ac=15, attacks=(_bow("tgt"),))
+    guard = _combatant("guard", ac=99)
+    # d20=20 hits (nat 20); confirm d20=1 -> 1+8-4=5 < 15 -> no crit.
+    eng = _engine(
+        [archer, tgt, guard],
+        [(0, 0), (0, 1), (1, 1)],
+        ["players", "monsters", "players"],
+        [20, 1, 3],
+    )
+    a, t, _g = eng._states
+    result = eng.resolve_attack(a, t, a.combatant.attacks[0])
+    assert result.hit is True
+    assert result.crit is False
+    assert result.damage == 3
+
+
+# ── Snapshot keys ────────────────────────────────────────────────────────────
+
+
+def test_snapshot_sneak_dice_and_engaged() -> None:
+    rogue = _combatant("rogue", level=5, features=("Sneak Attack",))
+    brute = _combatant("brute")
+    distant = _combatant("distant", attacks=(_bow("distant"),))
+    eng = _engine(
+        [rogue, brute, distant],
+        [(0, 0), (0, 1), (0, 7)],
+        ["players", "monsters", "players"],
+        [],
+    )
+    obs = _snapshot(eng, eng._states[0])
+    by_id = {c["id"]: c for c in obs["combatants"]}
+    assert by_id["rogue"]["sneak_dice"] == 3
+    assert by_id["brute"]["sneak_dice"] == 0
+    assert by_id["rogue"]["engaged_in_melee"] is True
+    assert by_id["brute"]["engaged_in_melee"] is True
+    assert by_id["distant"]["engaged_in_melee"] is False
+
+
+def test_condition_definitions_carry_miss_chance() -> None:
+    eng = _engine(
+        [_combatant("a"), _combatant("b")],
+        [(0, 0), (0, 3)],
+        ["players", "monsters"],
+        [],
+    )
+    obs = _snapshot(eng, eng._states[0])
+    defs = dict(obs["condition_definitions"])
+    assert defs["blurred"]["miss_chance"] == 20
+    assert defs["displaced"]["miss_chance"] == 50
+    assert defs["shaken"]["miss_chance"] == 0

tests/test_combat.py

@@ -794,7 +794,7 @@ def test_ranged_attack_ignores_flanking() -> None:
         "initiative: aly d20=9+0=9",
         "initiative: tgt d20=8+0=8",
         "round 1 tgt: AoO vs arc d20=15+2=17 AC 13 -> HIT 3 damage (6->3)",
-        "round 1 arc: short bow vs tgt d20=12+2=14 AC 15 -> MISS",
+        "round 1 arc: short bow vs tgt d20=12+2-2(melee)=12 AC 15 -> MISS",
         "round 1 aly: short sword vs tgt d20=10+0=10 AC 15 -> MISS",
         "round 1 tgt: short sword vs arc d20=5+2=7 AC 13 -> MISS",
         "battle over: draw after 1 rounds",

tests/test_observation_enriched.py

@@ -1232,7 +1232,7 @@ def test_observation_enriched_condition_definitions_present() -> None:
     """Given: an Observation built over any combat
     When: the top-level dict is inspected
     Then: condition_definitions is a sorted tuple of (name, {mods, flags,
-    speed_mult}) covering every entry of CONDITIONS_BY_NAME."""
+    speed_mult, miss_chance}) covering every entry of CONDITIONS_BY_NAME."""
     hero = make_combatant("hero")
     foe = make_combatant("foe")
     hero_state = make_state(hero, "players", (0, 0))
@@ -1246,10 +1246,11 @@ def test_observation_enriched_condition_definitions_present() -> None:
     # Sorted by name for determinism.
     assert [n for n, _ in defs] == sorted(CONDITIONS_BY_NAME)
     for _name, body in defs:
-        assert set(body) == {"mods", "flags", "speed_mult"}
+        assert set(body) == {"mods", "flags", "speed_mult", "miss_chance"}
         assert isinstance(body["mods"], list)
         assert isinstance(body["flags"], list)
         assert isinstance(body["speed_mult"], float)
+        assert isinstance(body["miss_chance"], int)
 
 
 def test_observation_enriched_condition_definitions_shaken() -> None: