fix(rules): a cone/line template excludes the caster's whole footprint, not just the anchor cell (SRD aiming-a-spell.md: 'It starts from any corner of your square' - every occupied square is origin space and never inside its own area) - cone_cells/line_cells take caster_cells; combat passes caster.occupied_cells(); 1x1 casters bit-identical; documented simplification: a grazed caster cell still consumes a length slot

src/pf1e_simulator/areas.py

@@ -5,7 +5,8 @@ PF1e (CRB, Magic — Aiming a Spell):
   direction you designate. It starts from any corner of your square and
   widens out as it goes." — modeled here as every cell whose center lies
   within the cone's length of the origin and within ±45° of the aim
-  direction (a 90°-wide quarter circle), excluding the origin cell.
+  direction (a 90°-wide quarter circle), excluding the caster's whole
+  space (every cell of the footprint, not just the anchor).
 - "A line-shaped spell shoots away from you in a line in the direction you
   designate. It starts from any corner of your square and extends to the
   limit of its range [...]. A line-shaped spell affects all creatures in
@@ -45,7 +46,11 @@ if TYPE_CHECKING:
 
 
 def cone_cells(
-    grid: Grid, origin: Pos, aim: Pos, radius_cells: int
+    grid: Grid,
+    origin: Pos,
+    aim: Pos,
+    radius_cells: int,
+    caster_cells: frozenset[Pos] = frozenset(),
 ) -> frozenset[Pos]:
     """Cells of a 90° cone of ``radius_cells`` squares starting at ``origin``.
 
@@ -53,8 +58,11 @@ def cone_cells(
     resolved target or point-cast center). A cell is affected when its offset
     from the origin is within ``radius_cells`` (5-10-5 grid distance), points
     strictly into the cone's forward half-plane, and stays within ±45° of the
-    aim bearing. The origin cell itself is never affected (CRB: the cone
-    "shoots away from you"). A cell with no line of effect from the origin
+    aim bearing. The caster's own space is never affected: the cone "starts
+    from any corner of your square" (CRB: it "shoots away from you"), so
+    EVERY cell in ``caster_cells`` (the caster's whole footprint; the anchor
+    ``origin`` is always one of them) is outside the template, not just the
+    origin. A cell with no line of effect from the origin
     is dropped (CRB, Line of Effect: a cone "affects only an area, creature,
     or object to which it has line of effect from its origin" - a solid wall
     stops the cone, it does not pass through). A degenerate aim
@@ -68,12 +76,13 @@ def cone_cells(
     d_col = aim[1] - origin[1]
     if d_row == 0 and d_col == 0:
         return frozenset()
+    skip = caster_cells | {origin}
     aim_sq = d_row * d_row + d_col * d_col
     cells: set[Pos] = set()
     for row in range(origin[0] - radius_cells, origin[0] + radius_cells + 1):
         for col in range(origin[1] - radius_cells, origin[1] + radius_cells + 1):
             cell = (row, col)
-            if cell == origin or not grid.in_bounds(cell):
+            if cell in skip or not grid.in_bounds(cell):
                 continue
             v_row = row - origin[0]
             v_col = col - origin[1]
@@ -91,16 +100,25 @@ def cone_cells(
 
 
 def line_cells(
-    grid: Grid, origin: Pos, aim: Pos, length_cells: int
+    grid: Grid,
+    origin: Pos,
+    aim: Pos,
+    length_cells: int,
+    caster_cells: frozenset[Pos] = frozenset(),
 ) -> frozenset[Pos]:
     """Cells of a 5-ft-wide line of ``length_cells`` squares from ``origin``.
 
     The line runs along the Bresenham ray from the origin toward ``aim``,
     extended to ``length_cells`` squares (CRB: it "extends to the limit of
     its range"). The line "starts from any corner of your square" (CRB, Magic
-    - Aiming a Spell), so the CASTER's own square is NOT affected: the
-    ``length_cells`` affected squares are the ones *beyond* the origin along
-    the ray. Out-of-bounds cells simply drop out of the template (creatures
+    - Aiming a Spell), so the CASTER's whole space is NOT affected: every
+    caster cell the ray grazes (the anchor ``origin`` included, i.e. all of
+    ``caster_cells``) is outside the template. For a 1x1 caster that is just
+    the origin, so the ``length_cells`` affected squares are the ones
+    *beyond* the origin along the ray. Documented simplification: a caster
+    cell the ray crosses still consumes one of the ``length_cells`` slots, so
+    a multi-cell caster's line is at most its own footprint shorter.
+    Out-of-bounds cells simply drop out of the template (creatures
     only exist in bounds). The ray stops at the first cell that blocks line
     of effect (CRB, Line: "or until it strikes a barrier that blocks line of
     effect") - the barrier cell itself is the last cell of the template (the
@@ -113,6 +131,7 @@ def line_cells(
     d_col = aim[1] - origin[1]
     if d_row == 0 and d_col == 0:
         return frozenset()
+    skip = caster_cells | {origin}
     # Extend the aim vector so the ray reaches `length_cells` squares BEYOND
     # the origin (the dominant-axis step count of a Bresenham line is
     # max(|d_row|, |d_col|)); the +1 accounts for the origin square we drop.
@@ -124,7 +143,7 @@ def line_cells(
     ray = _bresenham(origin, end)
     cells: list[Pos] = []
     for cell in ray[1 : length_cells + 1]:
-        if not grid.in_bounds(cell):
+        if cell in skip or not grid.in_bounds(cell):
             continue
         cells.append(cell)
         if grid.terrain_at(cell).blocks_los:

src/pf1e_simulator/combat.py

@@ -7255,9 +7255,15 @@ class CombatEngine:
         else:
             origin = caster.pos
             if effect.shape == "cone":
-                cells = cone_cells(self._grid, origin, aim, span_cells)
+                cells = cone_cells(
+                    self._grid, origin, aim, span_cells,
+                    caster_cells=caster.occupied_cells(),
+                )
             else:
-                cells = line_cells(self._grid, origin, aim, span_cells)
+                cells = line_cells(
+                    self._grid, origin, aim, span_cells,
+                    caster_cells=caster.occupied_cells(),
+                )
             affected = [
                 state
                 for state in self._states

tests/test_conformance_caster_footprint_origin.py

@@ -0,0 +1,74 @@
+"""A multi-cell caster's WHOLE footprint is outside its own cone/line.
+
+PF1e SRD "Aiming a Spell" (aiming-a-spell.md): a cone and a line "start from
+any corner of your square" -- for a creature with a space larger than one
+square, every occupied square is part of the origin space, so none of them is
+ever inside the creature's own area (the template "shoots away from you").
+The engine used to exclude only the anchor cell, so a Large caster's other
+cells fell inside its own cone/line template.
+"""
+
+from __future__ import annotations
+
+from pf1e_simulator.areas import cone_cells, line_cells
+from pf1e_simulator.combat import CombatEngine
+from pf1e_simulator.grid import Grid
+from pf1e_simulator.map import MapSpec, TerrainType
+from pf1e_simulator.rng import ScriptedRng
+from pf1e_simulator.spells import AreaEffect
+from tests.test_observation_enriched import make_combatant, make_state
+
+_FLOOR = TerrainType(type="floor", move_cost=1)
+
+
+def _open_grid() -> Grid:
+    return Grid.from_spec(
+        MapSpec(
+            name="footprint-origin",
+            terrain=tuple(["." * 8] * 8),
+            legend={".": _FLOOR},
+        )
+    )
+
+
+# A Large caster anchored at (1,1) occupies the 2x2 block below. Aiming east
+# from the anchor, the ray/cone grazes the caster's own cells (1,2) and (2,2).
+_FOOTPRINT = frozenset({(1, 1), (1, 2), (2, 1), (2, 2)})
+
+
+def test_cone_excludes_the_whole_caster_footprint() -> None:
+    grid = _open_grid()
+    cells = cone_cells(grid, (1, 1), (1, 6), 4, caster_cells=_FOOTPRINT)
+    assert not cells & _FOOTPRINT
+    # The exclusion is the footprint only: the cone keeps everything past it.
+    assert (1, 3) in cells
+    assert (2, 3) in cells
+
+
+def test_line_excludes_the_whole_caster_footprint() -> None:
+    grid = _open_grid()
+    cells = line_cells(grid, (1, 1), (1, 6), 6, caster_cells=_FOOTPRINT)
+    assert (1, 2) not in cells
+    assert (1, 3) in cells
+    assert (1, 7) in cells
+
+
+def test_single_cell_caster_templates_are_unchanged() -> None:
+    """1x1 regression: the footprint is just the anchor, which the old code
+    already dropped -- both templates must be identical to the pre-fix set."""
+    grid = _open_grid()
+    old_cone = cone_cells(grid, (1, 1), (1, 6), 4)
+    new_cone = cone_cells(grid, (1, 1), (1, 6), 4, caster_cells=frozenset({(1, 1)}))
+    assert old_cone == new_cone
+    old_line = line_cells(grid, (1, 1), (1, 6), 6)
+    new_line = line_cells(grid, (1, 1), (1, 6), 6, caster_cells=frozenset({(1, 1)}))
+    assert old_line == new_line
+
+
+def test_large_caster_is_not_caught_by_its_own_cone() -> None:
+    caster_spec = make_combatant("ogre", size="Large", hp=20)
+    caster = make_state(caster_spec, "players", (1, 1))
+    engine = CombatEngine(ScriptedRng([]), _open_grid(), [caster])
+    effect = AreaEffect(shape="cone", radius_ft=30)
+    affected = engine._area_creatures(effect, caster, (1, 6))
+    assert affected == []