diff --git a/README.md b/README.md
index 1ed3c93..3b3f728 100644
--- a/README.md
+++ b/README.md
@@ -1235,7 +1235,14 @@ Règles modélisées :
   coin/case selon le CRB ; les créatures 1×1 sont inchangées.
 - 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).
+  (`_expire_summons` décrémente puis retire). La durée des sorts `summon monster` est
+  `1 round/level` (SRD spells/summon-monster-1.md : « Duration 1 round/level (D) ») :
+  un `SummonEffect` déclare `duration_rounds_per_level` (défaut 0 = durée fixe,
+  comportement pré-conformance) et la durée est résolue au moment de l'incantation
+  comme `max(1, niveau du lanceur × duration_rounds_per_level)`, selon la même
+  convention de scalage par niveau que `ConditionEffect` (voir « Formes de zone et
+  scalage »). Les deux sorts importés (`summon_monster_i/ii.json`) portent
+  `duration_rounds_per_level: 1`.
 - Conditions effectives : 28 conditions prédéfinies (`conditions.py`). Leurs drapeaux
   comportementaux sont appliqués par le moteur : `cant_act` (étourdi, paralysé, dazed,
   endormi, inerme, fasciné) annule le tour ; `cant_attack` (nauséeux, épinglé) n'autorise qu'une unique action
diff --git a/data/spells/summon_monster_i.json b/data/spells/summon_monster_i.json
index 2c6cda0..b338c76 100644
--- a/data/spells/summon_monster_i.json
+++ b/data/spells/summon_monster_i.json
@@ -11,8 +11,9 @@
     {
       "type": "summon",
       "creature": "data/monsters/celestial_wolf.json",
-      "duration_rounds": 4
+      "duration_rounds": 1,
+      "duration_rounds_per_level": 1
     }
   ],
-  "description": "Casting time 1 round: summons one extraplanar creature from the 1st-level list (e.g. dire rat, dog, eagle) to fight for you for 1 round/level. Simplified: the engine bestiary holds no 1st-level summon, so the celestial wolf model is reused and the duration is set to 4 rounds (1 round/level at caster level 4)."
+  "description": "Casting time 1 round: summons one extraplanar creature from the 1st-level list (e.g. dire rat, dog, eagle) to fight for you. SRD duration 1 round/level (D), resolved at cast time from the caster level. Simplified: the engine bestiary holds no 1st-level summon, so the celestial wolf model is reused."
 }
diff --git a/data/spells/summon_monster_ii.json b/data/spells/summon_monster_ii.json
index aef9f6c..a0d3b96 100644
--- a/data/spells/summon_monster_ii.json
+++ b/data/spells/summon_monster_ii.json
@@ -11,8 +11,9 @@
     {
       "type": "summon",
       "creature": "data/monsters/celestial_wolf.json",
-      "duration_rounds": 5
+      "duration_rounds": 1,
+      "duration_rounds_per_level": 1
     }
   ],
-  "description": "Summons a celestial wolf to fight for you."
+  "description": "Summons a celestial wolf to fight for you. SRD duration 1 round/level (D), resolved at cast time from the caster level."
 }
diff --git a/src/pf1e_simulator/combat.py b/src/pf1e_simulator/combat.py
index da265a7..1adffce 100644
--- a/src/pf1e_simulator/combat.py
+++ b/src/pf1e_simulator/combat.py
@@ -7220,6 +7220,15 @@ class CombatEngine:
         _spell_name: str,
     ) -> str:
         """Apply a summoning effect - create a summoned creature."""
+        # PF1e (SRD spells/summon-monster-1.md): "Duration 1 round/level (D)"
+        # - a per-level duration resolves against the caster's level at cast
+        # time, mirroring the ConditionEffect convention; a fixed duration is
+        # the pre-conformance fallback.
+        duration = effect.duration_rounds
+        if effect.duration_rounds_per_level > 0:
+            duration = max(
+                1, state.combatant.level * effect.duration_rounds_per_level
+            )
         # Load the summoned creature
         try:
             summoned_combatant = load_combatant(Path(effect.creature))
@@ -7256,7 +7265,7 @@ class CombatEngine:
         self._states.insert(caster_idx + 1, summoned_state)
 
         # Set expiration
-        summoned_state.summon_duration = effect.duration_rounds
+        summoned_state.summon_duration = duration
         summoned_state.summon_caster_id = state.combatant.id
         self._apply_simple_monster_death(summoned_state)
 
@@ -7265,7 +7274,7 @@ class CombatEngine:
 
         self._log(
             f"round {self._current_round} {state.combatant.id}: "
-            f"summon {summoned_combatant.id} at {spawn_pos} ({effect.duration_rounds}r)"
+            f"summon {summoned_combatant.id} at {spawn_pos} ({duration}r)"
         )
         return f"summoned {summoned_combatant.id}"
 
diff --git a/src/pf1e_simulator/spells.py b/src/pf1e_simulator/spells.py
index bbb93f3..1ed6218 100644
--- a/src/pf1e_simulator/spells.py
+++ b/src/pf1e_simulator/spells.py
@@ -296,10 +296,17 @@ class SummonEffect:
     """Summoning spell effect.
 
     - creature: path to the creature JSON file (e.g., "data/monsters/celestial_wolf.json")
-    - duration_rounds: how long the summoned creature stays
+    - duration_rounds: fixed rounds the summoned creature stays, used when
+      ``duration_rounds_per_level`` is 0
+    - duration_rounds_per_level: PF1e "1 round/level" summoning duration
+      (SRD spells/summon-monster-1.md: "Duration 1 round/level (D)") - when
+      > 0 the rounds resolve at cast time as
+      ``max(1, caster_level * duration_rounds_per_level)``, mirroring
+      ``ConditionEffect``'s field of the same name.
     """
     creature: str
     duration_rounds: int
+    duration_rounds_per_level: int = 0
 
 
 SpellEffect = (
@@ -690,6 +697,9 @@ def _parse_summon_effect(effect: dict[str, Json]) -> SummonEffect:
     return SummonEffect(
         creature=_as_str(effect["creature"]),
         duration_rounds=_as_int(effect["duration_rounds"]),
+        duration_rounds_per_level=_as_int(
+            effect.get("duration_rounds_per_level", 0)
+        ),
     )
 
 
diff --git a/tests/test_summoning.py b/tests/test_summoning.py
index 7c15c98..c77ccac 100644
--- a/tests/test_summoning.py
+++ b/tests/test_summoning.py
@@ -20,7 +20,7 @@ from pf1e_simulator.models import (
     Saves,
 )
 from pf1e_simulator.rng import SeededRng
-from pf1e_simulator.spells import SpellSpec, SummonEffect
+from pf1e_simulator.spells import SPELLS_DIR, SpellSpec, SummonEffect, load_spell
 
 
 def _make_caster() -> Combatant:
@@ -260,3 +260,78 @@ class TestSummonedCreatureExpires:
             assert not wolf_states[0].active, (
                 "Wolf should be inactive after expiration"
             )
+
+
+class TestSummonDurationScalesWithCasterLevel:
+    """SRD spells/summon-monster-1.md: "Duration 1 round/level (D)" - the
+    summon's rounds resolve at cast time from the caster's level, mirroring
+    the ConditionEffect per-level duration convention."""
+
+    def _cast(self, caster_level: int, *, per_level: int) -> CombatEngine:
+        caster = _make_caster()
+        caster = caster.model_copy(update={"level": caster_level})
+        enemy = _make_enemy()
+        c = CombatantState(combatant=caster, side="players", pos=(0, 0), hp=caster.hp_max)
+        e = CombatantState(combatant=enemy, side="monsters", pos=(5, 0), hp=enemy.hp_max)
+        spell = SpellSpec(
+            name="Summon Monster II",
+            level=2,
+            school="conjuration",
+            range="close",
+            effects=(
+                SummonEffect(
+                    creature="data/monsters/celestial_wolf.json",
+                    duration_rounds=1,
+                    duration_rounds_per_level=per_level,
+                ),
+            ),
+        )
+        legend = {".": TerrainType(type="floor", move_cost=1)}
+        spec = MapSpec(name="test", terrain=tuple(["." * 12] * 12), legend=legend)
+        engine = CombatEngine(
+            SeededRng(1), Grid.from_spec(spec), [c, e],
+            spell_registry={"Summon Monster II": spell},
+        )
+        engine._cast_spell(c, e, "Summon Monster II")
+        return engine
+
+    def test_duration_equals_caster_level_rounds(self) -> None:
+        # Given/When: a level 5 caster summons with 1 round/level
+        # Then: the wolf lives for 5 rounds.
+        engine = self._cast(5, per_level=1)
+        wolf = next(s for s in engine._states if s.combatant.id == "celestial_wolf")
+        assert wolf.summon_duration == 5
+
+    def test_duration_scales_for_a_higher_caster(self) -> None:
+        # Given: a level 9 caster
+        # Then: 9 rounds - the duration is not the fixed JSON value.
+        engine = self._cast(9, per_level=1)
+        wolf = next(s for s in engine._states if s.combatant.id == "celestial_wolf")
+        assert wolf.summon_duration == 9
+
+    def test_fixed_duration_still_used_without_per_level_field(self) -> None:
+        # Given: a summon declaring only a fixed duration (per_level = 0)
+        # Then: the fixed value applies unchanged (pre-conformance fallback).
+        caster = _make_caster()
+        enemy = _make_enemy()
+        c = CombatantState(combatant=caster, side="players", pos=(0, 0), hp=caster.hp_max)
+        e = CombatantState(combatant=enemy, side="monsters", pos=(5, 0), hp=enemy.hp_max)
+        legend = {".": TerrainType(type="floor", move_cost=1)}
+        spec = MapSpec(name="test", terrain=tuple(["." * 12] * 12), legend=legend)
+        reg = {"Summon Monster II": _make_summon_spell(duration_rounds=3)}
+        engine = CombatEngine(
+            SeededRng(1), Grid.from_spec(spec), [c, e], spell_registry=reg
+        )
+        engine._cast_spell(c, e, "Summon Monster II")
+        wolf = next(s for s in engine._states if s.combatant.id == "celestial_wolf")
+        assert wolf.summon_duration == 3
+
+    def test_shipped_summon_spells_declare_per_level_duration(self) -> None:
+        # Given: the shipped spell data
+        # When: Summon Monster I/II are loaded
+        # Then: they carry the SRD 1 round/level duration (no fixed value).
+        for name in ("summon_monster_i.json", "summon_monster_ii.json"):
+            spell = load_spell(SPELLS_DIR / name)
+            effect = spell.effects[0]
+            assert isinstance(effect, SummonEffect)
+            assert effect.duration_rounds_per_level == 1