diff --git a/src/woodshop/cutplan.py b/src/woodshop/cutplan.py
index 56c0cfd..f7cb89d 100644
--- a/src/woodshop/cutplan.py
+++ b/src/woodshop/cutplan.py
@@ -309,10 +309,40 @@ def _pack_lumber_exact(items, stock, s, ids) -> tuple[list, list]:
     return sticks, oversize
 
 
-def _pack_plywood_guillotine(items, stock, s, ids) -> tuple[list, list]:
-    """Guillotine free-rectangle packing (best-area-fit + rotation) — usually
-    tighter than shelf packing for mixed panel sizes."""
-    sheets, unplaced, rects = [], [], {}
+def _free_rects_sheet(sp, s) -> list[list]:
+    """Non-overlapping free rectangles on a sheet, carved around its (locked)
+    placements with a kerf clearance. Guillotine subtraction: below/above span the
+    full width, then the middle band is cut left/right of the obstacle."""
+    rects = [[0.0, 0.0, sp.length_in, sp.width_in]]
+    k = s.kerf_in
+    for p in sp.placements:
+        ox, oy = p.x_in - k, p.y_in - k
+        ox1, oy1 = p.x_in + p.len_in + k, p.y_in + p.wid_in + k
+        new = []
+        for fx, fy, fw, fh in rects:
+            fx1, fy1 = fx + fw, fy + fh
+            if ox >= fx1 or ox1 <= fx or oy >= fy1 or oy1 <= fy:
+                new.append([fx, fy, fw, fh])                 # no overlap — keep
+                continue
+            cx0, cy0 = max(ox, fx), max(oy, fy)              # obstacle clipped to rect
+            cx1, cy1 = min(ox1, fx1), min(oy1, fy1)
+            for r in ([fx, fy, fw, cy0 - fy],                # below
+                      [fx, cy1, fw, fy1 - cy1],              # above
+                      [fx, cy0, cx0 - fx, cy1 - cy0],        # left of obstacle
+                      [cx1, cy0, fx1 - cx1, cy1 - cy0]):     # right of obstacle
+                if r[2] > 0.5 and r[3] > 0.5:
+                    new.append(r)
+        rects = new
+    return rects
+
+
+def _guillotine_pack(items, stock, s, ids, seed_sheets) -> tuple[list, list]:
+    """Guillotine free-rectangle packing (best-area-fit + rotation). `seed_sheets`
+    is a list of (StockPiece, free_rect_list) to pack into first (their existing
+    placements are kept); fresh sheets are opened as needed."""
+    sheets = [sp for sp, _ in seed_sheets]
+    rects = {sp.id: list(fr) for sp, fr in seed_sheets}
+    unplaced = []
 
     def orientations(it):
         opts = [(it.length_in, it.width_in, False)]
@@ -359,6 +389,19 @@ def _pack_plywood_guillotine(items, stock, s, ids) -> tuple[list, list]:
     return sheets, unplaced
 
 
+def _pack_plywood_guillotine(items, stock, s, ids) -> tuple[list, list]:
+    """Guillotine free-rectangle packing — usually tighter than shelf packing."""
+    return _guillotine_pack(items, stock, s, ids, [])
+
+
+def _pack_plywood_seeded(items, stock, s, ids, seeds) -> tuple[list, list]:
+    """Pack unlocked panels into the free space AROUND locked panels on seeded
+    sheets first, then onto fresh sheets — the plywood analogue of
+    `_pack_lumber_seeded`."""
+    seed_sheets = [(sp, _free_rects_sheet(sp, s)) for sp in seeds]
+    return _guillotine_pack(items, stock, s, ids, seed_sheets)
+
+
 def build_cut_plan(scene, settings: ShopSettings | None = None,
                    strategy: str = "decreasing") -> CutPlan:
     s = settings or ShopSettings()
@@ -442,9 +485,9 @@ def _free_segments(sp: StockPiece, kerf: float) -> list:
 
 
 def reoptimize(scene, base_plan: CutPlan, strategy: str = "decreasing") -> CutPlan:
-    """Re-pack while PRESERVING locked placements where they sit. Unlocked lumber
-    is packed into the free space around locked pieces (then new sticks); unlocked
-    plywood goes onto fresh sheets (locked sheets keep their locked panels)."""
+    """Re-pack while PRESERVING locked placements where they sit. Unlocked pieces
+    are packed into the free space around locked ones first (free segments on
+    seeded sticks / free rectangles on seeded sheets), then onto new stock."""
     s = base_plan.settings
     items = _cut_items(scene)
     locked = [p for sp in base_plan.stock_pieces for p in sp.placements if p.locked]
@@ -479,11 +522,10 @@ def reoptimize(scene, base_plan: CutPlan, strategy: str = "decreasing") -> CutPl
         seed_pieces = list(seeds.get(stock, {}).values())
         is_sheet = (its and its[0].is_sheet) or (seed_pieces and seed_pieces[0].is_sheet)
         if is_sheet:
-            new_sheets, un = _pack_plywood(its, stock, s, ids) if its else ([], [])
-            stock_pieces += seed_pieces + new_sheets
+            sps, un = _pack_plywood_seeded(its, stock, s, ids, seed_pieces)
         else:
             sps, un = _pack_lumber_seeded(its, stock, s, ids, seed_pieces)
-            stock_pieces += sps
+        stock_pieces += sps
         unplaced += un
     for iid in unplaced:
         it = next(i for i in items if i.id == iid)
diff --git a/src/woodshop/gui/bom_window.py b/src/woodshop/gui/bom_window.py
index 987a886..55bd962 100644
--- a/src/woodshop/gui/bom_window.py
+++ b/src/woodshop/gui/bom_window.py
@@ -285,10 +285,12 @@ class BomWindow(QDialog):
     def _best_of_n(self) -> None:
         self._optimized = True
         if self._has_locks():
-            best = min((reoptimize(self.c.scene, self._plan, st) for st in STRATEGIES),
+            strategies = list(STRATEGIES)
+            strategies += [f"shuffle{i}" for i in range(max(100 - len(strategies), 0))]
+            best = min((reoptimize(self.c.scene, self._plan, st) for st in strategies),
                        key=_plan_key)
             self._set_plan(best)
-            self._status.setText("✓ best around locked pieces")
+            self._status.setText("✓ best of 100 around locked pieces")
         else:
             self._set_plan(best_cut_plan(self.c.scene, attempts=100))
             self._status.setText("✓ best of 100 attempts")
diff --git a/tests/test_bom_window.py b/tests/test_bom_window.py
index 4e58ecd..3ec1292 100644
--- a/tests/test_bom_window.py
+++ b/tests/test_bom_window.py
@@ -58,6 +58,19 @@ def test_best_of_n_button_keeps_valid_plan(tmp_path):
     assert "best" in w._status.text().lower()
 
 
+def test_best_of_n_with_lock_runs_and_validates(tmp_path):
+    from woodshop.cutplan import validate_cut_plan
+    c = Controller(str(tmp_path / "s.json"))
+    for ln in (50, 46, 40, 30):
+        c.place("2x4", ln)
+    w = BomWindow(c)
+    p = next(p for sp in w._plan.stock_pieces for p in sp.placements)
+    p.locked = True
+    w._best_of_n()                           # locked path: strategies + shuffles
+    assert validate_cut_plan(w._plan) == []
+    assert "locked" in w._status.text()
+
+
 def test_valid_move_commits(tmp_path):
     c = Controller(str(tmp_path / "s.json"))
     c.place("2x4", 20)
diff --git a/tests/test_cutplan.py b/tests/test_cutplan.py
index 1760a8a..e46302e 100644
--- a/tests/test_cutplan.py
+++ b/tests/test_cutplan.py
@@ -259,6 +259,31 @@ def test_best_of_n_no_worse():
     assert validate_cut_plan(best) == []
 
 
+def test_reoptimize_plywood_keeps_unlocked_on_locked_sheet():
+    """Locking one panel must NOT push the other onto a fresh sheet when they
+    still share one sheet (Codex finding #1)."""
+    from woodshop.cutplan import reoptimize
+    s = Scene()
+    s.place("ply-3/4", 40, width_in=20)
+    s.place("ply-3/4", 40, width_in=20)
+    plan = build_cut_plan(s, strategy="guillotine")
+    sheets = [sp for sp in plan.stock_pieces if sp.is_sheet]
+    assert len(sheets) == 1
+    locked = sheets[0].placements[0]
+    locked.locked = True
+    lx, ly, lid = locked.x_in, locked.y_in, locked.id
+
+    re = reoptimize(s, plan, "guillotine")
+    re_sheets = [sp for sp in re.stock_pieces if sp.is_sheet]
+    assert len(re_sheets) == 1                       # still one sheet, not split
+    placed = {p.item_id for sp in re.stock_pieces for p in sp.placements}
+    assert {it.id for it in re.items} <= placed | set(re.unplaced)
+    kept = [p for sp in re.stock_pieces for p in sp.placements if p.id == lid]
+    assert kept and kept[0].locked
+    assert abs(kept[0].x_in - lx) < 1e-6 and abs(kept[0].y_in - ly) < 1e-6
+    assert validate_cut_plan(re) == []
+
+
 def test_custom_settings_kerf():
     s = Scene()
     s.place("2x4", 48)