fix(rules): metamagic no longer raises the save DC - only Heighten Spell does (SRD empower-spell: saving throws not affected; heighten-spell: DCs calculated at the heightened level, modeled at its minimum +1 slot adjustment)

tests/test_conformance_spellflow.py

@@ -1,8 +1,11 @@
 """PF1e conformance: spell-casting flow fixes B7 / B14 / B24.
 
 B7  (CRB, Metamagic Feats): metamagic is chosen PER CAST, costs slot levels
-    (Empower +2, Maximize +3, Extend +1), the DC uses the slot level, and
-    only feats the caster knows can apply.
+    (Empower +2, Maximize +3, Extend +1, Heighten +1 modeled minimum), and
+    only feats the caster knows can apply. The save DC uses the spell's
+    BASE level - metamagic does not raise it (SRD empower: "Saving throws
+    and opposed rolls are not affected"); only Heighten Spell raises the DC
+    to the heightened level (SRD heighten-spell).
 B14 (CRB, Magic, Range: Touch): delivering a touch spell to an unwilling
     creature requires a melee touch attack (miss = spell wasted); a willing
     target (self/ally) needs no roll.
@@ -182,13 +185,16 @@ def _state(combatant: Combatant, side: str, pos: tuple[int, int]) -> CombatantSt
 
 
 class TestMetamagicPerCast:
-    """B7: metamagic is chosen per cast, costs slot levels, and the DC uses
-    the slot level (CRB, Metamagic Feats)."""
+    """B7: metamagic is chosen per cast and costs slot levels, but the save
+    DC stays at the spell's base level - only Heighten Spell raises it
+    (SRD, Metamagic Feats)."""
 
-    def test_empower_costs_slot_two_levels_higher_and_dc_uses_it(self) -> None:
+    def test_empower_costs_slot_two_levels_higher_but_dc_stays_base(self) -> None:
         # Given: a caster who knows Empower Spell with a level-3 slot
         # When: casting Bolt (lvl 1) with Empower Spell
-        # Then: the level-3 slot burns and the DC is 10 + 3 + int 4 = 17.
+        # Then: the level-3 slot burns but the DC is 10 + 1 + int 4 = 15
+        # (SRD empower-spell: "Saving throws and opposed rolls are not
+        # affected" - the higher slot does not raise the DC).
         caster = _caster(metamagic=["Empower Spell"])
         c, f = _state(caster, "players", (0, 0)), _state(_foe(), "monsters", (3, 0))
         engine = _engine([c, f], [3, 3])  # 2d4 -> 6, empowered -> 9
@@ -196,21 +202,23 @@ class TestMetamagicPerCast:
         assert c.spell_slots_left[3] == 0
         assert c.spell_slots_left[1] == 1
         assert f.hp == 100 - 9
-        assert any("DC17" in line for line in engine._transcript)
+        assert any("DC15" in line for line in engine._transcript)
+        assert not any("DC17" in line for line in engine._transcript)
 
-    def test_maximize_costs_slot_three_levels_higher(self) -> None:
+    def test_maximize_costs_slot_three_levels_higher_dc_stays_base(self) -> None:
         # Given: a caster who knows Maximize Spell
         # When: casting Bolt maximized (2d4 max = 8)
-        # Then: the level-4 slot burns and the DC is 10 + 4 + 4 = 18.
+        # Then: the level-4 slot burns but the DC is 10 + 1 + 4 = 15.
         caster = _caster(metamagic=["Maximize Spell"])
         c, f = _state(caster, "players", (0, 0)), _state(_foe(), "monsters", (3, 0))
         engine = _engine([c, f], [1, 1])  # dice overwritten by maximize
         engine._cast_spell(c, f, "Bolt", metamagic=("Maximize Spell",))
         assert c.spell_slots_left[4] == 0
         assert f.hp == 100 - 8
-        assert any("DC18" in line for line in engine._transcript)
+        assert any("DC15" in line for line in engine._transcript)
+        assert not any("DC18" in line for line in engine._transcript)
 
-    def test_extend_costs_one_slot_level_and_doubles_duration(self) -> None:
+    def test_extend_costs_one_slot_level_doubles_duration_and_dc_stays_base(self) -> None:
         # Given: a caster who knows Extend Spell, self-targeting a touch buff
         # When: casting Grace (2r) extended
         # Then: the level-2 slot burns and the condition lasts 4 rounds.
@@ -221,6 +229,30 @@ class TestMetamagicPerCast:
         assert c.spell_slots_left[2] == 0
         assert c.spell_slots_left[1] == 1
         assert c.active_conditions[0].rounds_left == 4
+        # Extend raises the slot cost but never the DC: a hostile extended
+        # Bolt still DCs at its base level.
+        c2 = _state(caster, "players", (0, 0))
+        f2 = _state(_foe(), "monsters", (3, 0))
+        engine2 = _engine([c2, f2], [3, 3])
+        engine2._cast_spell(c2, f2, "Bolt", metamagic=("Extend Spell",))
+        assert any("DC15" in line for line in engine2._transcript)
+        assert not any("DC16" in line for line in engine2._transcript)
+
+    def test_heighten_spell_raises_the_dc_to_the_heightened_level(self) -> None:
+        # Given: a caster who knows Heighten Spell (modeled at its minimum
+        # +1 adjustment - the engine's per-cast API carries feat names only)
+        # When: casting Bolt (lvl 1) heightened
+        # Then: the level-2 slot burns AND the DC is 10 + 2 + int 4 = 16
+        # (SRD heighten-spell: "All effects dependent on spell level (such
+        # as saving throw DCs [...]) are calculated according to the
+        # heightened level").
+        caster = _caster(metamagic=["Heighten Spell"])
+        c, f = _state(caster, "players", (0, 0)), _state(_foe(), "monsters", (3, 0))
+        engine = _engine([c, f], [3, 3])
+        engine._cast_spell(c, f, "Bolt", metamagic=("Heighten Spell",))
+        assert c.spell_slots_left[2] == 0
+        assert c.spell_slots_left[1] == 1
+        assert any("DC16" in line for line in engine._transcript)
 
     def test_unknown_metamagic_feat_is_never_applied(self) -> None:
         # Given: a caster who knows NO metamagic