Count copper already on the board as connections already made

Fixed tracks and vias only kept other nets away, so a pin fanned out to
its plane was routed to the plane again, beside its own fan-out. Pins,
zones and planes that fixed copper of their net touches now form one
connected group: a fanned-out supply pin needs nothing more, a fanned-out
signal routes from its via, and copper touching no pin or zone adds
nothing to route.

bench/diagnose.py

@@ -106,6 +106,15 @@ def _capture_conflicts() -> list:
     return log
 
 
+def _wall_name(wall, names) -> str:
+    if isinstance(wall, str):
+        if wall.startswith("fixed copper of net "):
+            net = int(wall.rsplit(" ", 1)[1])
+            return f"fixed copper of {names.get(net, net)}"
+        return wall
+    return names.get(wall, "pads/keepouts")
+
+
 def _gap(a, b) -> int:
     dx = max(b.ll.x - a.ur.x, a.ll.x - b.ur.x, 0)
     dy = max(b.ll.y - a.ur.y, a.ll.y - b.ur.y, 0)
@@ -118,6 +127,25 @@ def _fresh(seen) -> GridRouter:
     return router
 
 
+def _static_wall(router: GridRouter, node) -> str:
+    """What static copper closes a node: a keepout, copper already on the
+    board (a fixed via or track, by net), or a pad."""
+    if node in router._keepout:
+        return "keepout"
+    fixed = getattr(router, "_diag_fixed", None)
+    if fixed is None:
+        fixed = router._diag_fixed = {}
+        margin = router.clearance + router.half_width
+        for net, layers, box in router.board.get_fixed_copper():
+            for cell in router._cells_in_box(box, margin):
+                for layer in layers:
+                    fixed[(*cell, layer)] = net
+    net = fixed.get(node)
+    if net is not None:
+        return f"fixed copper of net {net}"
+    return "pads"
+
+
 def _flood(router: GridRouter, pin, net_no: int, conns) -> tuple[int, Counter]:
     """How many nodes a pin can reach through free cells (up to FLOOD_LIMIT),
     and which other nets' copper bounds the region."""
@@ -146,7 +174,7 @@ def _flood(router: GridRouter, pin, net_no: int, conns) -> tuple[int, Counter]:
                 for owner in owners:
                     walls[conns[owner].net_no] += 1
                 if not owners:
-                    walls[0] += 1  # a pad or keepout
+                    walls[_static_wall(router, n)] += 1
                 continue
             seen.add(n)
             frontier.append(n)
@@ -224,7 +252,9 @@ def diagnose(
                     if reach < FLOOD_LIMIT:
                         walled.append({
                             "pin": end, "reach": reach,
-                            "walls": [names.get(n, "pads/keepouts") for n, _ in walls.most_common(4)],
+                            "walls": [
+                                _wall_name(n, names) for n, _ in walls.most_common(4)
+                            ],
                         })
             row["kind"] = "walled-in" if walled else "congestion"
             if walled:

src/freeroute/board/board.py

@@ -70,6 +70,27 @@ class BasicBoard:
     def get_traces(self) -> list[Trace]:
         return [it for it in self._items if isinstance(it, Trace)]
 
+    def get_fixed_copper(self) -> list[tuple[int, frozenset[int], IntBox]]:
+        """Copper already routed on the board (the DSN's ``wiring``), as
+        ``(net, layers, box)``. A track is its segments, its corners and the
+        round caps at its ends (as squares); a via is its largest pad."""
+        from freeroute.geometry.polyline import Polyline, PolylineShape, corner_box
+
+        out: list[tuple[int, frozenset[int], IntBox]] = []
+        for item in self._items:
+            if not item.fixed or not item.net_nos:
+                continue
+            net = item.net_nos[0]
+            if isinstance(item, Trace) and not item.is_empty():
+                layers = frozenset({item.layer})
+                for box in PolylineShape(Polyline(item.corners), item.half_width).tiles():
+                    out.append((net, layers, box))
+                for end in (item.corners[0], item.corners[-1]):
+                    out.append((net, layers, corner_box(end, item.half_width)))
+            elif isinstance(item, Via) and item.shape is not None:
+                out.append((net, frozenset(item.layers), item.shape.bounding_box()))
+        return out
+
     def get_vias(self) -> list[Via]:
         return [it for it in self._items if isinstance(it, Via)]
 

src/freeroute/board/build.py

@@ -31,7 +31,7 @@ from freeroute.geometry.polygon_shape import PolygonShape
 
 from .board import BasicBoard
 from .clearance import ClearanceMatrix
-from .items import ConductionArea, ObstacleArea, Pin
+from .items import ConductionArea, ObstacleArea, Pin, Trace, Via
 from .layer import Layer, LayerStructure
 from .net import Nets
 from .transform import CoordinateTransform
@@ -56,6 +56,7 @@ def build_board(dsn: DsnBoard) -> BasicBoard:
     _insert_keepouts(dsn, board, transform)
     _insert_image_keepouts(dsn, board, transform)
     _insert_zones(dsn, board, transform, nets)
+    _insert_wiring(dsn, board, transform, nets)
     return board
 
 
@@ -471,6 +472,47 @@ def _placed_area_tiles(shape: Shape, place, transform: CoordinateTransform) -> l
     return [tile for tile in PolygonShape(pts).split_to_convex() if not tile.is_empty()]
 
 
+def _insert_wiring(dsn: DsnBoard, board: BasicBoard, transform: CoordinateTransform, nets) -> None:
+    """Tracks and vias already on the board, as fixed copper of their nets."""
+    layer_no = {layer.name: i for i, layer in enumerate(dsn.layers)}
+    signal_layers = [i for i, layer in enumerate(dsn.layers) if layer.is_signal]
+    numbers = {net.name: net.net_number for net in nets}
+    for wire in dsn.wires:
+        if wire.net not in numbers or wire.layer not in layer_no:
+            continue
+        c = wire.coords
+        corners = [transform.dsn_to_board_point(c[i], c[i + 1]) for i in range(0, len(c) - 1, 2)]
+        if len(corners) < 2:
+            continue
+        board.insert(
+            Trace(
+                net_nos=[numbers[wire.net]], fixed=True, layer=layer_no[wire.layer],
+                half_width=max(round(transform.dsn_to_board(wire.width / 2)), 1), corners=corners,
+            )
+        )
+    for via in dsn.vias:
+        padstack = dsn.padstack(via.padstack)
+        if via.net not in numbers or padstack is None or not padstack.shapes:
+            continue
+        layers: set[int] = set()
+        for shape in padstack.shapes:
+            if shape.layer in ("signal", "pcb"):
+                layers.update(signal_layers)
+            elif shape.layer in layer_no:
+                layers.add(layer_no[shape.layer])
+        location = transform.dsn_to_board_point(via.x, via.y)
+        pad = _pad_tile(max(padstack.shapes, key=_shape_extent), transform)
+        box = pad.bounding_box()
+        board.insert(
+            Via(
+                net_nos=[numbers[via.net]], fixed=True, padstack_name=via.padstack,
+                location=location, layers=sorted(layers or signal_layers),
+                shape=IntBox(box.ll.x + location.x, box.ll.y + location.y,
+                             box.ur.x + location.x, box.ur.y + location.y),
+            )
+        )
+
+
 def _insert_zones(dsn: DsnBoard, board: BasicBoard, transform: CoordinateTransform, nets) -> None:
     """Each DSN plane as a ConductionArea of its net on its layer."""
     layer_no = {layer.name: i for i, layer in enumerate(dsn.layers)}

src/freeroute/board/items.py

@@ -114,6 +114,9 @@ class Via(Item):
 
     padstack_name: str = ""
     location: IntPoint = field(default_factory=lambda: IntPoint(0, 0))
+    #: layer indices the via's pads occupy, and the largest pad as a box
+    layers: list[int] = field(default_factory=list)
+    shape: object = None
 
 
 @dataclass

src/freeroute/cli.py

@@ -30,8 +30,8 @@ from freeroute.ses import write_ses
 #: which optional flags each engine actually implements. Anything not listed for
 #: an engine is rejected by :func:`_validate` rather than quietly ignored.
 ENGINE_OPTIONS: dict[str, frozenset[str]] = {
-    "grid": frozenset({"rip_up", "max_passes", "seed", "orders", "promote", "access", "escapes"}),
-    "exact": frozenset({"shove", "diagonal", "rip_up", "max_passes", "seed", "orders", "promote", "access", "escapes"}),
+    "grid": frozenset({"rip_up", "max_passes", "seed", "orders", "promote", "access", "rollback"}),
+    "exact": frozenset({"shove", "diagonal", "rip_up", "max_passes", "seed", "orders", "promote", "access", "rollback"}),
     "room": frozenset({"shove", "pack"}),
 }
 
@@ -46,7 +46,7 @@ _FLAG_NAMES = {
     "orders": "--orders",
     "promote": "--promote-failures",
     "access": "--access-cost",
-    "escapes": "--reserve-escapes",
+    "rollback": "--no-rollback",
 }
 
 
@@ -168,10 +168,20 @@ def build_parser() -> argparse.ArgumentParser:
         "another pin's way out while that pin still has connections to route (default 0: off)",
     )
     parser.add_argument(
-        "--reserve-escapes",
-        action="store_true",
-        help="grid and exact engines: before routing, reserve a way out for every fine-pitch "
-        "pin that no other net may use until that pin's connections are routed",
+        "--no-rollback",
+        dest="rollback",
+        action="store_false",
+        help="grid and exact engines: keep every rip-up, as before. By default the "
+        "connections a rip-up displaces are rerouted at once and the rip-up is undone "
+        "if fewer connections end up routed",
+    )
+    parser.add_argument(
+        "--hole-to-hole",
+        type=float,
+        default=0.25,
+        metavar="MM",
+        help="grid and exact engines: least distance between the edges of any two via "
+        "holes, of one net or two (KiCad's min_hole_to_hole; default 0.25)",
     )
     parser.add_argument(
         "--jobs",
@@ -202,7 +212,7 @@ def main(argv: list[str] | None = None) -> int:
             ("orders", args.orders is not None),
             ("promote", args.promote_failures is not None),
             ("access", args.access_cost is not None),
-            ("escapes", args.reserve_escapes),
+            ("rollback", not args.rollback),
         )
         if asked
     ]
@@ -237,7 +247,8 @@ def main(argv: list[str] | None = None) -> int:
             "resolution": 2 if args.grid_resolution is None else args.grid_resolution,
             "heuristic_weight": args.heuristic_weight,
             "access_cost": args.access_cost or 0.0,
-            "reserve_escapes": args.reserve_escapes,
+            "hole_to_hole_mm": args.hole_to_hole,
+            "rollback": args.rollback,
         }
     elif args.engine == "grid":
         options = {
@@ -247,7 +258,8 @@ def main(argv: list[str] | None = None) -> int:
             "edge_clearance_mm": args.edge_clearance,
             "resolution": 1 if args.grid_resolution is None else args.grid_resolution,
             "access_cost": args.access_cost or 0.0,
-            "reserve_escapes": args.reserve_escapes,
+            "hole_to_hole_mm": args.hole_to_hole,
+            "rollback": args.rollback,
         }
     if args.engine == "room":
         result = build_rooms_routing_result(
@@ -285,6 +297,14 @@ def main(argv: list[str] | None = None) -> int:
         print(f"freeroute: {len(missing)} connection(s) not routed:", file=sys.stderr)
         for net, a, b, _zone in missing:
             print(f"  {net}: {a} to {b}", file=sys.stderr)
+    if result.narrowed:
+        print(
+            f"freeroute: {len(result.narrowed)} connection(s) of a wider net class only fitted "
+            "at the default width; their nets are written at the default width:",
+            file=sys.stderr,
+        )
+        for net, a, b in result.narrowed:
+            print(f"  {net}: {a} to {b}", file=sys.stderr)
     if in_zone:
         print(
             f"freeroute: {len(in_zone)} more connection(s) left to a zone fill that may join them:",

src/freeroute/dsn/model.py

@@ -27,6 +27,8 @@ __all__ = [
     "NetPin",
     "Net",
     "NetClass",
+    "WiringVia",
+    "WiringWire",
     "Keepout",
     "DsnBoard",
 ]
@@ -186,6 +188,26 @@ class Keepout:
     kind: str = "keepout"  # keepout | via_keepout | wire_keepout | place_keepout
 
 
+@dataclass
+class WiringWire:
+    """A track already on the board: ``(wire (path LAYER WIDTH x y ...) (net N))``."""
+
+    net: str
+    layer: str
+    width: float
+    coords: list[float] = field(default_factory=list)
+
+
+@dataclass
+class WiringVia:
+    """A via already on the board: ``(via PADSTACK x y (net N))``."""
+
+    net: str
+    padstack: str
+    x: float
+    y: float
+
+
 @dataclass
 class DsnBoard:
     """The fully parsed DSN file."""
@@ -197,6 +219,9 @@ class DsnBoard:
     layers: list[Layer] = field(default_factory=list)
     #: copper zones, as planes of a net
     planes: list[Plane] = field(default_factory=list)
+    #: copper already routed (the ``wiring`` scope), kept fixed
+    wires: list[WiringWire] = field(default_factory=list)
+    vias: list[WiringVia] = field(default_factory=list)
     #: bounding-box boundary shape (layer ``pcb``), if present
     boundary: Shape | None = None
     #: outline shapes (layer ``signal``)

src/freeroute/dsn/reader.py

@@ -27,6 +27,8 @@ from .model import (
     Pin,
     Resolution,
     WidthRule,
+    WiringVia,
+    WiringWire,
 )
 from .sexp import SExp, parse
 from .shapes import Shape, read_area, read_shape
@@ -531,11 +533,45 @@ def parse_dsn(text: str) -> DsnBoard:
             _read_placement(it, board)
         elif head == "network":
             _read_network(it, board)
-        # `wiring` and unknown scopes are intentionally ignored for now.
+        elif head == "wiring":
+            _read_wiring(it, board)
+        # unknown scopes are ignored
 
     return board
 
 
+def _read_wiring(node: SExp, board: DsnBoard) -> None:
+    """Tracks and vias already on the board. They stay where they are: the
+    router treats them as copper of their net that other nets keep clear of."""
+    for it in node.items:
+        if not isinstance(it, SExp):
+            continue
+        net_scope = it.child("net")
+        net = _first_value(net_scope) if net_scope is not None else None
+        if not net:
+            continue  # netless copper would need a keepout, not a wire
+        if it.head == "wire":
+            path = it.child("path") or it.child("polyline_path")
+            vals = [v.text for v in path.values()] if path is not None else []
+            if len(vals) < 6:
+                continue
+            try:
+                width = float(vals[1])
+                coords = [float(v) for v in vals[2:]]
+            except ValueError:
+                continue
+            board.wires.append(WiringWire(net=net, layer=vals[0], width=width, coords=coords))
+        elif it.head == "via":
+            vals = [v.text for v in it.values()]
+            if len(vals) < 3:
+                continue
+            try:
+                x, y = float(vals[1]), float(vals[2])
+            except ValueError:
+                continue
+            board.vias.append(WiringVia(net=net, padstack=vals[0], x=x, y=y))
+
+
 def _read_plane(node: SExp):
     """``(plane <net> (polygon <layer> <width> x y ...))`` -> :class:`Plane`."""
     from .model import Plane

src/freeroute/route/exact_router.py

@@ -31,7 +31,7 @@ from dataclasses import dataclass, field
 import math
 
 from freeroute.board.board import BasicBoard
-from freeroute.board.items import Pin
+from freeroute.board.items import Pin, Via
 from freeroute.board.search_tree import ShapeSearchTree, TreeShape
 from freeroute.geometry import (
     IntBox,
@@ -98,7 +98,10 @@ def route_board_exact(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
-    reserve_escapes: bool = False,
+    rollback: bool = True,
+    net_widths: dict[int, int] | None = None,
+    via_drill: int | None = None,
+    hole_to_hole: int = 0,
 ) -> ExactRouteResult:
     """Route ``board`` orthogonally and verify the result with exact geometry.
 
@@ -130,7 +133,10 @@ def route_board_exact(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
-        reserve_escapes=reserve_escapes,
+        rollback=rollback,
+        net_widths=net_widths,
+        via_drill=via_drill,
+        hole_to_hole=hole_to_hole,
     )
     edge = 0 if edge_clearance is None else edge_clearance
     outline = board.outline
@@ -149,6 +155,10 @@ def route_board_exact(
         pin_layers = frozenset(layer for layer in pin.layers if layer in signal_layers)
         if pin_layers:
             tree.insert(TreeShape(next(owner), net, pin_layers, box))
+    for net, copper_layers, box in board.get_fixed_copper():
+        on = frozenset(layer for layer in copper_layers if layer in signal_layers)
+        if on and not box.is_empty():
+            tree.insert(TreeShape(next(owner), net, on, box))
     for obstacle in board.get_obstacle_areas():
         if obstacle.layer not in signal_layers:
             continue
@@ -168,23 +178,32 @@ def route_board_exact(
 
     via_layers = frozenset(signal_layers)
     accepted: dict[int, _Accepted] = {}
+    fixed_vias = {
+        (item.net_nos[0], item.location)
+        for item in board.get_items()
+        if isinstance(item, Via) and item.fixed and item.net_nos
+    }
 
     # Verify connection by connection, so one conflicting segment of a
     # 25-pin supply net costs that one connection, not the whole net.
     rejected: list[tuple[int, str, str]] = []
     ends_list = result.connection_ends or [("?", "?", "")] * len(result.connections)
+    # each net is checked at the width it will be written at: its class's
+    # when all of its connections went in at that, else the default
+    net_half = dict(result.net_half)
     for (net_no, wires, vias), ends in sorted(
         zip(result.connections, ends_list, strict=False), key=lambda c: c[0][0]
     ):
-        boxes = _copper_boxes(wires, vias, half_width, via_layers, via_half)
-        wire_count = len(_copper_boxes(wires, [], half_width, via_layers, via_half))
+        wire_half = net_half.get(net_no, half_width)
+        boxes = _copper_boxes(wires, vias, wire_half, via_layers, via_half)
+        wire_count = len(_copper_boxes(wires, [], wire_half, via_layers, via_half))
         if any(
             tree.clearance_conflict(
                 box, net_no, layer, clearance, "wire" if i < wire_count else "via"
             )
             for i, (box, box_layers) in enumerate(boxes)
             for layer in box_layers
-        ) or _end_in_rule_area(tree, wires, half_width) or (
+        ) or _end_in_rule_area(tree, wires, wire_half) or (
             outline is not None and not all(outline.box_clear(b, edge) for b, _ in boxes)
         ):
             rejected.append((net_no, *ends))
@@ -193,7 +212,11 @@ def route_board_exact(
         if acc is None:
             acc = accepted[net_no] = _Accepted(wires=[], vias=[])
         acc.wires.extend(wires)
-        acc.vias.extend(vias)
+        # connections of one net that end on the same plane cell share its
+        # via: write it once, and never on top of a via already on the board
+        acc.vias.extend(
+            v for v in dict.fromkeys(vias) if v not in acc.vias and (net_no, v) not in fixed_vias
+        )
         for box, box_layers in boxes:
             oid = next(owner)
             tree.insert(TreeShape(oid, net_no, box_layers, box, routed=True))
@@ -243,6 +266,17 @@ def route_board_exact(
     for net_no, acc in accepted.items():
         clean.wires[net_no] = acc.wires
         clean.vias[net_no] = acc.vias
+    # shove and the diagonal pass lay copper at the default width: nets they
+    # recovered, and nets whose traces shove pushed aside
+    reshaped = (set(accepted) - accepted_before_recovery) | {
+        net for net, acc in accepted.items() if acc.shove_count
+    }
+    if diagonal:
+        reshaped = set(accepted)
+    clean.net_half = {
+        net: half for net, half in net_half.items() if net in accepted and net not in reshaped
+    }
+    clean.narrowed = list(result.narrowed)
 
     drc_clean = tree.has_violation(clearance) is None
     return ExactRouteResult(result=clean, tree=tree, drc_clean=drc_clean, shoves=shoves)

src/freeroute/route/grid_router.py

@@ -31,7 +31,7 @@ import math
 import random
 
 from freeroute.board.board import BasicBoard
-from freeroute.board.items import ConductionArea, ObstacleArea, Pin
+from freeroute.board.items import ConductionArea, ObstacleArea, Pin, Via
 from freeroute.geometry import IntBox, IntPoint
 from freeroute.geometry.polyline import corner_box
 
@@ -61,7 +61,10 @@ class RouteResult:
     ``routed_net_numbers`` are the nets that got any wire or via.
     """
 
-    __slots__ = ("wires", "vias", "half_width", "unrouted", "connections", "connection_ends", "failed")
+    __slots__ = (
+        "wires", "vias", "half_width", "unrouted", "connections", "connection_ends", "failed",
+        "net_half", "narrowed",
+    )
 
     def __init__(self, half_width: int) -> None:
         self.wires: dict[int, list[tuple[int, list[IntPoint]]]] = {}
@@ -76,6 +79,10 @@ class RouteResult:
         self.connection_ends: list[tuple[str, str, str]] = []
         #: connections left unrouted: (net_no, one end, the other end)
         self.failed: list[tuple[int, str, str]] = []
+        #: half width of each net routed wider than the default (its class)
+        self.net_half: dict[int, int] = {}
+        #: connections of a wider class that only fitted at the default width
+        self.narrowed: list[tuple[int, str, str]] = []
 
     def add_wire(self, net_no: int, layer: int, path: list[IntPoint]) -> None:
         self.wires.setdefault(net_no, []).append((layer, path))
@@ -113,6 +120,9 @@ class _Connection:
         "b_group",
         "a_end",
         "b_end",
+        "path",
+        "narrow",
+        "half",
     )
 
     def __init__(self, index: int, net_no: int, a: Pin, b: Pin) -> None:
@@ -134,6 +144,12 @@ class _Connection:
         self.b_group: tuple[list[Pin], list] = ([b], [])
         self.a_end: Pin | None = a
         self.b_end: Pin | None = b
+        # the node path last committed, so a rip-up can be undone
+        self.path: list[Node] | None = None
+        # a connection of a wider class that did not fit at that width is
+        # routed at the default width instead; the half width it went in at
+        self.narrow = False
+        self.half = 0
 
 
 class GridRouter:
@@ -159,7 +175,10 @@ class GridRouter:
         seed: int | None = None,
         route_first: frozenset | None = None,
         access_cost: float = 0.0,
-        reserve_escapes: bool = False,
+        rollback: bool = True,
+        net_widths: dict[int, int] | None = None,
+        via_drill: int | None = None,
+        hole_to_hole: int = 0,
     ) -> None:
         self.board = board
         # Pin access: while a pin still has connections to route, the cells
@@ -169,12 +188,12 @@ class GridRouter:
         self.access_cost = max(float(access_cost), 0.0)
         self._doorways: dict[Node, list[tuple[int, int]]] = {}
         self._pending: dict[int, int] = {}
-        # Escape reservations: before routing, every crowded (fine-pitch) pin
-        # gets a short way out to open board, and while it still has
-        # connections to route no other net may use those cells (nor come
-        # within clearance of them).
-        self.reserve_escapes = bool(reserve_escapes)
-        self._reserved: dict[Node, list[tuple[int, int]]] = {}
+        # Rip-up as a transaction: the connections a rip-up route crosses are
+        # rerouted at once, and if fewer connections are routed afterwards
+        # than before, everything goes back as it was. On by default: over
+        # 8 net orders it left 25 to 30 fewer connections unrouted on dense
+        # boards and was never clearly worse.
+        self.rollback = bool(rollback)
         # None keeps the deterministic order; a seed shuffles which connection
         # routes first, to measure how much a result owes to the order
         self.seed = seed
@@ -220,6 +239,34 @@ class GridRouter:
         self.edge_clearance = 0 if edge_clearance is None else edge_clearance
         need = self.via_half + self.clearance + self.half_width
         self.via_reach = max(0, math.ceil(need / self.step) - 1)
+        # Net classes wider than the default: the grid is laid out for the
+        # default width, so a wider trace must also find the cells around its
+        # own free, out to its extra half width, and claims a wider halo.
+        self._net_half = {
+            net: max(width // 2, 1)
+            for net, width in (net_widths or {}).items()
+            if width // 2 > self.half_width
+        }
+        self._spread: list[tuple[int, int]] = []  # the current search's
+        self._cur_half = self.half_width
+        self._halo_by_half: dict[int, list[tuple[int, int]]] = {self.half_width: self._halo_offsets}
+        # Hole-to-hole spacing holds between any two vias, of one net or two.
+        # Other nets' vias are kept further apart already; a net's own vias
+        # (every pin of a supply dropping to its plane) are not, so a via
+        # must keep its drill plus the spacing from every via centre, except
+        # an own-net via at the very same cell, which it simply reuses.
+        drill = via_drill if via_drill else 2 * self.via_half
+        need = drill + max(hole_to_hole, 0)
+        reach = math.ceil(need / self.step)
+        self._hole_offsets = [
+            (dx, dy)
+            for dx in range(-reach, reach + 1)
+            for dy in range(-reach, reach + 1)
+            if (dx or dy) and math.hypot(dx, dy) * self.step < need
+        ]
+        self._via_nets: dict[Cell, dict[int, int]] = {}  # routed via centres
+        self._fixed_vias: dict[Cell, int] = {}
+        self._fixed_via_points: set[tuple[int, IntPoint]] = set()
 
         if layers is None:
             layers = [i for i, layer in enumerate(board.layer_structure.arr) if layer.is_signal]
@@ -247,6 +294,11 @@ class GridRouter:
         # trace halos: node -> indices of the connections claiming it
         self._halo: dict[Node, list[int]] = {}
         self._rasterize_obstacles()
+        self._rasterize_fixed_copper()
+        for item in board.get_items():
+            if isinstance(item, Via) and item.fixed and item.net_nos:
+                self._fixed_vias[self._cell_of(item.location)] = item.net_nos[0]
+                self._fixed_via_points.add((item.net_nos[0], item.location))
 
     # --- grid helpers -------------------------------------------------------
 
@@ -307,6 +359,9 @@ class GridRouter:
         self._via_edge_block: set[Cell] = set()
         # wire keepouts as boxes, to check a pin stub the way the exact engine will
         self._keepout_boxes: dict[int, list[tuple[IntBox, bool]]] = {}
+        # via keepouts as boxes, and other copper a via in a pad must clear
+        self._via_keepout_boxes: list[tuple[IntBox, bool]] = []
+        self._static_copper: list[tuple[IntBox, int]] | None = None
         # pin end nodes no wire can reach without entering a keepout
         self._via_only: set[Node] = set()
         if outline is not None:
@@ -356,6 +411,18 @@ class GridRouter:
                             self._keepout.add((*cell, item.layer))
                         if item.blocks_vias:
                             self._via_keepout.add((*cell, item.layer))
+                    if item.blocks_vias:
+                        self._via_keepout_boxes.append((box, item.clearance))
+
+    def _rasterize_fixed_copper(self) -> None:
+        """Tracks and vias already on the board: copper of their net, which
+        other nets keep the same distance from as from a pad."""
+        margin = self.clearance + self.half_width
+        for net, layers, box in self.board.get_fixed_copper():
+            on = [layer for layer in layers if layer in self.layers]
+            for cell in self._cells_in_box(box, margin):
+                for layer in on:
+                    self._pad_block.setdefault((*cell, layer), set()).add(net)
 
     # --- occupancy cost -----------------------------------------------------
 
@@ -367,6 +434,30 @@ class GridRouter:
         allow_ripup: bool,
         conns: list[_Connection],
         wire_keepout: bool = True,
+    ) -> float | None:
+        """:meth:`_enter_cost_base`, and for a trace wider than the default
+        the same for every cell its extra width reaches (the worst of them)."""
+        cost = self._enter_cost_base(cell, layer, net_no, allow_ripup, conns, wire_keepout)
+        if cost is None or not self._spread:
+            return cost
+        for dx, dy in self._spread:
+            c = (cell[0] + dx, cell[1] + dy)
+            if not (0 <= c[0] < self.cols and 0 <= c[1] < self.rows):
+                return None
+            more = self._enter_cost_base(c, layer, net_no, allow_ripup, conns, wire_keepout)
+            if more is None:
+                return None
+            cost = max(cost, more)
+        return cost
+
+    def _enter_cost_base(
+        self,
+        cell: Cell,
+        layer: int,
+        net_no: int,
+        allow_ripup: bool,
+        conns: list[_Connection],
+        wire_keepout: bool = True,
     ) -> float | None:
         """Cost to enter ``(cell, layer)`` for ``net_no``; ``None`` if blocked.
 
@@ -378,10 +469,6 @@ class GridRouter:
         node = (*cell, layer)
         if wire_keepout and node in self._keepout:
             return None
-        if self._reserved:
-            for pin_id, owner_net in self._reserved.get(node, ()):
-                if owner_net != net_no and self._pending.get(pin_id, 0) > 0:
-                    return None  # another pin's reserved way out
         pads = self._pad_block.get(node)
         if pads and any(n != net_no for n in pads) and net_no not in self._pad_own.get(node, ()):
             return None
@@ -425,14 +512,72 @@ class GridRouter:
             for layer in self.layers:
                 if (*c, layer) in self._via_keepout:
                     return False
-                if self._enter_cost(c, layer, net_no, False, conns, wire_keepout=False) != 0.0:
+                if self._enter_cost_base(c, layer, net_no, False, conns, wire_keepout=False) != 0.0:
                     return False
-        return True
+        return self._holes_clear(cell, net_no)
+
+    def _via_nets_at(self, cell: Cell) -> set[int]:
+        nets = {net for net, n in self._via_nets.get(cell, {}).items() if n > 0}
+        fixed = self._fixed_vias.get(cell)
+        if fixed is not None:
+            nets.add(fixed)
+        return nets
+
+    def _holes_clear(self, cell: Cell, net_no: int) -> bool:
+        """No via centre within hole-to-hole reach, but an own-net one here."""
+        if self._via_nets_at(cell) - {net_no}:
+            return False
+        cx, cy = cell
+        return not any(self._via_nets_at((cx + dx, cy + dy)) for dx, dy in self._hole_offsets)
 
     # --- A* search ----------------------------------------------------------
 
+    def _conn_half(self, conn: _Connection) -> int:
+        """The half width a connection is routed at: its class's, unless it
+        has fallen back to the default."""
+        return self.half_width if conn.narrow else self._net_half.get(conn.net_no, self.half_width)
+
+    def _spread_for(self, half: int) -> list[tuple[int, int]]:
+        """Cells a trace of ``half`` also needs free: those whose centre is
+        within its extra half width (plus half a cell, for the grid)."""
+        extra = half - self.half_width
+        if extra <= 0:
+            return []
+        reach = math.ceil(extra / self.step) + 1
+        limit = extra + self.step / 2
+        return [
+            (dx, dy)
+            for dx in range(-reach, reach + 1)
+            for dy in range(-reach, reach + 1)
+            if (dx or dy) and math.hypot(dx, dy) * self.step <= limit
+        ]
+
+    def _halo_for(self, half: int) -> list[tuple[int, int]]:
+        """Cells a committed trace of ``half`` claims from default-width traces."""
+        offsets = self._halo_by_half.get(half)
+        if offsets is None:
+            need = half + self.clearance + self.half_width
+            reach = math.ceil(need / self.step)
+            offsets = self._halo_by_half[half] = [
+                (dx, dy)
+                for dx in range(-reach, reach + 1)
+                for dy in range(-reach, reach + 1)
+                if (dx or dy) and math.hypot(dx, dy) * self.step < need
+            ]
+        return offsets
+
     def _search(
         self, conn: _Connection, allow_ripup: bool, conns: list[_Connection]
+    ) -> list[Node] | None:
+        half = self._conn_half(conn)
+        self._cur_half, self._spread = half, self._spread_for(half)
+        try:
+            return self._search_at_width(conn, allow_ripup, conns)
+        finally:
+            self._cur_half, self._spread = self.half_width, []
+
+    def _search_at_width(
+        self, conn: _Connection, allow_ripup: bool, conns: list[_Connection]
     ) -> list[Node] | None:
         goal_cell = self._group_target(conn.b_group)
         if not conn.b_group[0] and any(z.layer in self._power_layers for z in conn.b_group[1]):
@@ -442,7 +587,14 @@ class GridRouter:
         goals = self._group_ends(conn.b_group, conn.net_no, conns)
         if not starts or not goals:
             return None
-        common = sorted(set(starts) & set(goals))
+        # A start that is already an end joins at once, except that ending on
+        # a plane there needs a via: one that cannot be placed (a via keepout,
+        # another net's pad) is no end, and the search goes on from there.
+        common = [
+            n for n in sorted(set(starts) & set(goals))
+            if not isinstance(goals[n], ConductionArea)
+            or self._via_placeable((n[0], n[1]), conn.net_no, conns)
+        ]
         if common:
             conn.a_end, conn.b_end = starts[common[0]], goals[common[0]]
             return [common[0]]
@@ -452,10 +604,11 @@ class GridRouter:
         g_score: dict[Node, float] = {}
         came_from: dict[Node, Node] = {}
         # a stub costs its length, so the nearest cell wins unless it is blocked
-        goal_stub = {n: self._stub_cost(p, n) for n, p in goals.items() if p is not None}
+        # a pin end costs its stub; a zone or plane end is entered normally
+        goal_stub = {n: self._stub_cost(p, n) for n, p in goals.items() if isinstance(p, Pin)}
         for s in sorted(starts):
             pin = starts[s]
-            g_score[s] = self._stub_cost(pin, s) if pin is not None else 0.0
+            g_score[s] = self._stub_cost(pin, s) if isinstance(pin, Pin) else 0.0
             heapq.heappush(open_heap, (g_score[s] + self._h(s, goal_cell), s))
 
         # Via footprints are checked lazily: a layer change goes on the heap as
@@ -474,6 +627,12 @@ class GridRouter:
                 ok = via_ok.get(cell)
                 if ok is None:
                     ok = via_ok[cell] = self._via_placeable(cell, net_no, conns)
+                # a via leaving or reaching a walled-in pin goes in its pad
+                # (see _commit), so it has to fit there exactly
+                for node, ends in ((source, starts), (target, goals)):
+                    pin = ends.get(node)
+                    if ok and isinstance(pin, Pin) and self._walled(node):
+                        ok = self._via_fits_at(pin.location, net_no)
                 if ok:
                     self._relax(source, target, g_via, goal_cell, g_score, came_from, open_heap)
                 continue
@@ -537,12 +696,35 @@ class GridRouter:
     # copper too, or a stub ends up closer than clearance to a trace in the
     # cell beside it.
 
-    def _stub_cells(self, pin_location: IntPoint, cell: Cell) -> list[Cell]:
+    def _walled(self, node: Node) -> bool:
+        """A pin end no wire may leave or reach: only a via in its pad will do."""
+        return node in self._keepout or node in self._via_only
+
+    def _via_fits_at(self, point: IntPoint, net_no: int) -> bool:
+        """A via centred exactly on ``point`` clears every via keepout and all
+        other nets' pads and fixed copper (what a via in a pad must meet)."""
+        via = IntBox(point.x - self.via_half, point.y - self.via_half,
+                     point.x + self.via_half, point.y + self.via_half)
+        grown = via.offset(self.clearance)
+        for box, needs in self._via_keepout_boxes:
+            if box.overlaps(grown if needs else via):
+                return False
+        if self._static_copper is None:
+            copper = [
+                (p.shape.bounding_box(), p.net_nos[0] if p.net_nos else -1)
+                for p in self.board.get_pins()
+                if p.shape is not None and any(layer in self.layers for layer in p.layers)
+            ]
+            copper += [(box, net) for net, _, box in self.board.get_fixed_copper()]
+            self._static_copper = copper
+        return not any(net != net_no and box.overlaps(grown) for box, net in self._static_copper)
+
+    def _stub_cells(self, pin_location: IntPoint, cell: Cell, half: int | None = None) -> list[Cell]:
         """Cells where another net's trace would come too close to the stub."""
         from freeroute.board.outline import _point_segment
 
         end = self._cell_center(cell)
-        reach = 2 * self.half_width + self.clearance
+        reach = (half or self._cur_half) + self.half_width + self.clearance
         box = IntBox(
             min(pin_location.x, end.x), min(pin_location.y, end.y),
             max(pin_location.x, end.x), max(pin_location.y, end.y),
@@ -564,12 +746,12 @@ class GridRouter:
 
             end = self._cell_center(cell)
             if end != pin.location:
-                for tile in PolylineShape(Polyline([pin.location, end]), self.half_width).tiles():
+                for tile in PolylineShape(Polyline([pin.location, end]), self._cur_half).tiles():
                     grown = tile.offset(self.clearance)
                     if any(k.overlaps(grown if needs else tile) for k, needs in keepouts):
                         return False
                 # the track's round end at the pin, for a rule area
-                cap = corner_box(pin.location, self.half_width)
+                cap = corner_box(pin.location, self._cur_half)
                 if any(not needs and k.overlaps(cap) for k, needs in keepouts):
                     return False
         if keepouts_only:
@@ -799,6 +981,7 @@ class GridRouter:
     # --- commit / rip -------------------------------------------------------
 
     def _commit(self, conn: _Connection, path: list[Node]) -> None:
+        conn.path = list(path)
         wire_segs, via_cells = _split_path(path)
         via_cells = list(via_cells)
         if isinstance(conn.a_end, ConductionArea):
@@ -807,11 +990,16 @@ class GridRouter:
             via_cells.append((path[-1][0], path[-1][1]))
         conn.trace_cells = [(cell, layer) for layer, cells in wire_segs for cell in cells]
         conn.via_cells = list(via_cells)
+        for cell in conn.via_cells:
+            count = self._via_nets.setdefault(cell, {})
+            count[conn.net_no] = count.get(conn.net_no, 0) + 1
         for cell, layer in conn.trace_cells:
             self._cell_owner[(*cell, layer)] = conn.index
+        conn.half = half = self._conn_half(conn)
+        halo = self._halo_for(half)
         conn.halo_nodes = []
         for (cx, cy), layer in conn.trace_cells:
-            for dx, dy in self._halo_offsets:
+            for dx, dy in halo:
                 x, y = cx + dx, cy + dy
                 if 0 <= x < self.cols and 0 <= y < self.rows:
                     node = (x, y, layer)
@@ -828,7 +1016,7 @@ class GridRouter:
             if not isinstance(pin, Pin):
                 continue  # ended on a zone or a plane: no stub
             cell = cells[at]
-            for c in self._stub_cells(pin.location, cell):
+            for c in self._stub_cells(pin.location, cell, half):
                 node = (*c, layer)
                 if node not in self._cell_owner:
                     self._cell_owner[node] = conn.index
@@ -879,6 +1067,10 @@ class GridRouter:
                     del self._halo[node]
         conn.halo_nodes = []
         conn.trace_cells = []
+        for cell in conn.via_cells:
+            count = self._via_nets.get(cell)
+            if count and count.get(conn.net_no):
+                count[conn.net_no] -= 1
         conn.via_cells = []
         conn.wires = []
         conn.vias = []
@@ -912,6 +1104,7 @@ class GridRouter:
         done: set[int] = set()
         for conn in conns:
             for pin in self._group_pins(conn):
+                self._pending[id(pin)] = self._pending.get(id(pin), 0) + 1
                 if id(pin) in done:
                     continue
                 done.add(id(pin))
@@ -929,76 +1122,6 @@ class GridRouter:
                 for node in cells:
                     self._doorways.setdefault(node, []).append(claim)
 
-    def _count_pending(self, conns: list[_Connection]) -> None:
-        """How many unrouted connections each pin is an end of."""
-        for conn in conns:
-            for pin in self._group_pins(conn):
-                self._pending[id(pin)] = self._pending.get(id(pin), 0) + 1
-
-    def _reserve_escapes(self, conns: list[_Connection]) -> None:
-        """Give every crowded pin a way out before anything is routed."""
-        blocked: set[Node] = set()  # earlier escapes and their clearance
-        spread = [(0, 0), *self._halo_offsets]
-        seen: set[int] = set()
-        for conn in conns:
-            for pin in self._group_pins(conn):
-                if id(pin) in seen or not self._crowded(pin, conn.net_no):
-                    continue
-                seen.add(id(pin))
-                path = self._escape_path(pin, conn.net_no, conns, blocked)
-                if not path:
-                    continue
-                claim = (id(pin), conn.net_no)
-                for x, y, layer in path:
-                    for dx, dy in spread:
-                        node = (x + dx, y + dy, layer)
-                        if 0 <= node[0] < self.cols and 0 <= node[1] < self.rows:
-                            self._reserved.setdefault(node, []).append(claim)
-                            blocked.add(node)
-
-    def _escape_path(self, pin: Pin, net_no: int, conns, blocked: set[Node]) -> list[Node]:
-        """The shortest way from a pin to a cell clear of other nets' pads,
-        against pads, keepouts and earlier escapes only (breadth first, on
-        the pin's own layers, at most ``2 * _escape_cells`` long)."""
-        starts = [n for n in self._end_nodes(pin, net_no, conns) if n not in blocked]
-        came: dict[Node, Node | None] = dict.fromkeys(starts)
-        frontier = list(starts)
-        limit = 2 * self._escape_cells
-        for _depth in range(limit):
-            nxt: list[Node] = []
-            for node in frontier:
-                if node not in starts and self._open_ground(node, net_no):
-                    path = [node]
-                    while came[path[-1]] is not None:
-                        path.append(came[path[-1]])
-                    return path[::-1]
-                x, y, layer = node
-                for dx, dy in self._neighbours:
-                    n = (x + dx, y + dy, layer)
-                    if n in came or n in blocked:
-                        continue
-                    if not (0 <= n[0] < self.cols and 0 <= n[1] < self.rows):
-                        continue
-                    if not self._static_open(n, net_no):
-                        continue
-                    came[n] = node
-                    nxt.append(n)
-            frontier = nxt
-            if not frontier:
-                break
-        return []
-
-    def _open_ground(self, node: Node, net_no: int) -> bool:
-        """Clear of every other net's pad by a full trace spacing all round."""
-        x, y, layer = node
-        for dx, dy in self._halo_offsets:
-            n = (x + dx, y + dy, layer)
-            if not (0 <= n[0] < self.cols and 0 <= n[1] < self.rows):
-                return False
-            if not self._static_open(n, net_no):
-                return False
-        return True
-
     def _settle(self, conn: _Connection, delta: int) -> None:
         if not self._pending:
             return
@@ -1021,17 +1144,14 @@ class GridRouter:
         self._conns = conns
         if not conns:
             return RouteResult(self.half_width)
-        if self.access_cost or self.reserve_escapes:
-            self._count_pending(conns)
         if self.access_cost:
             self._build_doorways(conns)
-        if self.reserve_escapes:
-            self._reserve_escapes(conns)
 
         passes = self.max_passes if self.rip_up else 1
         best_count = -1
         best_snapshot: list[tuple[int, list, list]] | None = None
         best_unrouted = len(conns)
+        best_widths: tuple[dict[int, int], list] = ({}, [])
         # conns[i].index == i is what rip-up relies on, so shuffle a view
         order = list(conns)
         if self.seed is not None:
@@ -1051,13 +1171,25 @@ class GridRouter:
                 best_count = routed_count
                 best_unrouted = len(conns) - routed_count
                 best_snapshot = self._snapshot(conns)
+                best_widths = self._net_widths(conns)
             if routed_count == len(conns):
                 break
             if not changed:
                 break
-        return self._result_from(best_snapshot or [], best_unrouted)
+        result = self._result_from(best_snapshot or [], best_unrouted)
+        result.net_half, result.narrowed = best_widths
+        return result
 
     def _try_route(self, conn: _Connection, conns: list[_Connection]) -> bool:
+        if self._route_once(conn, conns):
+            return True
+        if conn.narrow or conn.net_no not in self._net_half:
+            return False
+        # a wider class that does not fit: route it at the default width
+        conn.narrow = True
+        return self._route_once(conn, conns)
+
+    def _route_once(self, conn: _Connection, conns: list[_Connection]) -> bool:
         path = self._search(conn, allow_ripup=False, conns=conns)
         if path is None:
             if not self.rip_up:
@@ -1065,11 +1197,41 @@ class GridRouter:
             path = self._search(conn, allow_ripup=True, conns=conns)
             if path is None:
                 return False
-            for idx in sorted(self._crossed_owners(path, conn.net_no, conns)):
-                self._rip(conns[idx])
+            victims = [conns[i] for i in sorted(self._crossed_owners(path, conn.net_no, conns))]
+            if self.rollback:
+                return self._ripup_transaction(conn, path, victims, conns)
+            for victim in victims:
+                self._rip(victim)
         self._commit(conn, path)
         return True
 
+    def _ripup_transaction(self, conn, path, victims, conns) -> bool:
+        """Route ``conn`` through ``victims``, reroute them at once in free
+        space, and undo it all if fewer connections end up routed."""
+        saved = [(v, v.path, v.a_end, v.b_end, v.rip_count) for v in victims]
+        own_rips = conn.rip_count
+        for victim in victims:
+            self._rip(victim)
+        self._commit(conn, path)
+        rerouted = 0
+        for victim in victims:
+            again = self._search(victim, allow_ripup=False, conns=conns)
+            if again is not None:
+                self._commit(victim, again)
+                rerouted += 1
+        if 1 + rerouted >= len(victims):
+            return True  # a gain, or an even trade that may pay off later
+        for victim in victims:
+            if victim.routed:
+                self._rip(victim)
+        self._rip(conn)
+        conn.rip_count = own_rips
+        for victim, old_path, a_end, b_end, rips in saved:
+            victim.a_end, victim.b_end = a_end, b_end
+            self._commit(victim, old_path)
+            victim.rip_count = rips
+        return False
+
     def _build_connections(self) -> list[_Connection]:
         pins_by_net = self._pins_by_net()
         zones_by_net: dict[int, list] = {}
@@ -1091,7 +1253,9 @@ class GridRouter:
         # deterministic: fewer-pin nets first, then by net number
         for net_no in sorted(nets, key=lambda n: (len(pins_by_net.get(n, [])), n)):
             zones = zones_by_net.get(net_no, []) + planes_by_net.get(net_no, [])
-            groups = _connected_groups(pins_by_net.get(net_no, []), zones, plane_ids)
+            groups = _connected_groups(
+                pins_by_net.get(net_no, []), zones, plane_ids, self._fixed_pieces(net_no)
+            )
             hubs = [g for g in groups if any(id(z) in plane_ids for z in g[1])]
             if hubs:
                 # a plane net: every other group goes straight to the plane
@@ -1105,6 +1269,28 @@ class GridRouter:
                 conns.append(conn)
         return conns
 
+    def _fixed_pieces(self, net_no: int) -> list[_FixedPiece]:
+        """The net's tracks and vias already on the board, as connectivity."""
+        cache = getattr(self, "_fixed_cache", None)
+        if cache is None:
+            from freeroute.board.items import Trace
+            from freeroute.geometry.polyline import Polyline, PolylineShape, corner_box
+
+            cache = self._fixed_cache = {}
+            for item in self.board.get_items():
+                if not item.fixed or not item.net_nos:
+                    continue
+                if isinstance(item, Via) and item.shape is not None:
+                    piece = _FixedPiece(item.layers, [item.shape.bounding_box()], via=item)
+                elif isinstance(item, Trace) and not item.is_empty():
+                    boxes = list(PolylineShape(Polyline(item.corners), item.half_width).tiles())
+                    boxes += [corner_box(e, item.half_width) for e in (item.corners[0], item.corners[-1])]
+                    piece = _FixedPiece([item.layer], boxes)
+                else:
+                    continue
+                cache.setdefault(item.net_nos[0], []).append(piece)
+        return cache.get(net_no, [])
+
     def _pins_by_net(self) -> dict[int, list[Pin]]:
         by_net: dict[int, list[Pin]] = {}
         for pin in self.board.get_pins():
@@ -1114,6 +1300,21 @@ class GridRouter:
                 by_net.setdefault(net_no, []).append(pin)
         return by_net
 
+    def _net_widths(self, conns: list[_Connection]) -> tuple[dict[int, int], list]:
+        """Half width of each wider-class net whose routed connections all went
+        in at it (a net is written at one width), and the connections that
+        had to fall back to the default."""
+        halves: dict[int, int] = {}
+        narrowed = []
+        for c in conns:
+            if not c.routed:
+                continue
+            halves[c.net_no] = min(halves.get(c.net_no, c.half), c.half)
+            if c.narrow:
+                narrowed.append((c.net_no, *_ends_of(c)))
+        wide = {net: half for net, half in halves.items() if half > self.half_width}
+        return wide, narrowed
+
     def _snapshot(self, conns: list[_Connection]) -> list[tuple]:
         return [
             (c.net_no, [(layer, list(pts)) for layer, pts in c.wires], list(c.vias),
@@ -1124,11 +1325,16 @@ class GridRouter:
 
     def _result_from(self, snapshot, unrouted: int) -> RouteResult:
         result = RouteResult(self.half_width)
+        written: set[tuple[int, IntPoint]] = set()
         result.unrouted = unrouted
         for net_no, wires, vias, ends in snapshot:
             for layer, points in wires:
                 result.add_wire(net_no, layer, points)
             for location in vias:
+                spot = (net_no, location)
+                if spot in written or spot in self._fixed_via_points:
+                    continue  # a via reused by another connection, or already on the board
+                written.add(spot)
                 result.add_via(net_no, location)
             result.connections.append((net_no, wires, vias))
             result.connection_ends.append(ends)
@@ -1179,13 +1385,49 @@ def _pin_touches_zone(pin: Pin, zone, plane: bool = False) -> bool:
     return any(zone.polygon.contains(c) for c in corners)
 
 
+def _touches(a: IntBox, b: IntBox) -> bool:
+    return not (a.ur.x < b.ll.x or b.ur.x < a.ll.x or a.ur.y < b.ll.y or b.ur.y < a.ll.y)
+
+
+def _fixed_joins_zone(piece, zone, plane: bool) -> bool:
+    """A through via inside a plane joins it; copper inside a zone on its
+    own layer joins that zone."""
+    if zone.polygon is None:
+        return False
+    if piece.via is not None:
+        if plane or zone.layer in piece.layers:
+            return zone.polygon.contains(piece.via.location)
+        return False
+    return zone.layer in piece.layers and any(
+        zone.polygon.contains(IntPoint((b.ll.x + b.ur.x) // 2, (b.ll.y + b.ur.y) // 2))
+        for b in piece.boxes
+    )
+
+
+class _FixedPiece:
+    """One track or via already on the board, as connectivity."""
+
+    __slots__ = ("layers", "boxes", "via")
+
+    def __init__(self, layers, boxes, via=None) -> None:
+        self.layers = frozenset(layers)
+        self.boxes = boxes
+        self.via = via  # the Via item, for a via
+
+
 def _connected_groups(
-    pins: list[Pin], zones: list, planes: frozenset = frozenset()
+    pins: list[Pin], zones: list, planes: frozenset = frozenset(), fixed: list | None = None
 ) -> list[tuple[list[Pin], list]]:
     """Pins and zones of one net that copper already joins: a pad in a zone
-    is connected to it, and two zones sharing a pad are one. Only the groups
-    need routing between them. Pin groups come first, in pin order."""
-    parent = list(range(len(pins) + len(zones)))
+    is connected to it, two zones sharing a pad are one, and copper already
+    on the board (tracks and vias, ``fixed``) joins whatever it touches. Only
+    the groups need routing between them. Pin groups come first, in pin
+    order. A group's fixed vias join its pins as extra route ends, so a
+    fanned-out pin is routed from its via; copper that touches no pin and no
+    zone adds nothing to route."""
+    fixed = fixed or []
+    n_pins, n_zones = len(pins), len(zones)
+    parent = list(range(n_pins + n_zones + len(fixed)))
 
     def find(i: int) -> int:
         while parent[i] != i:
@@ -1197,6 +1439,24 @@ def _connected_groups(
         for i, pin in enumerate(pins):
             if _pin_touches_zone(pin, zone, id(zone) in planes):
                 parent[find(i)] = find(len(pins) + j)
+    base = n_pins + n_zones
+    for k, piece in enumerate(fixed):
+        me = base + k
+        for i, pin in enumerate(pins):
+            if pin.shape is None or not piece.layers & set(pin.layers):
+                continue
+            pad = pin.shape.bounding_box()
+            if any(_touches(pad, b) for b in piece.boxes):
+                parent[find(i)] = find(me)
+        for j, zone in enumerate(zones):
+            if _fixed_joins_zone(piece, zone, id(zone) in planes):
+                parent[find(n_pins + j)] = find(me)
+        for k2 in range(k):
+            other = fixed[k2]
+            if piece.layers & other.layers and any(
+                _touches(a, b) for a in piece.boxes for b in other.boxes
+            ):
+                parent[find(base + k2)] = find(me)
     groups: dict[int, tuple[list[Pin], list]] = {}
     order: list[int] = []
     for i, pin in enumerate(pins):
@@ -1211,9 +1471,22 @@ def _connected_groups(
             groups[root] = ([], [])
             order.append(root)
         groups[root][1].append(zone)
+    for k, piece in enumerate(fixed):
+        root = find(base + k)
+        if piece.via is not None and root in groups:
+            groups[root][0].append(_via_end(piece.via))
     return [groups[r] for r in order]
 
 
+def _via_end(via) -> Pin:
+    """A fixed via as a place a route may start or end (not a pad to route)."""
+    return Pin(
+        net_nos=list(via.net_nos), fixed=True, name="via", component_ref="",
+        padstack_name=via.padstack_name, location=via.location,
+        layers=list(via.layers), shape=via.shape,
+    )
+
+
 def _split_path(path: list[Node]) -> tuple[list[tuple[int, list[Cell]]], list[Cell]]:
     """Split a node path into per-layer wire segments and via cells."""
     wires: list[tuple[int, list[Cell]]] = []
@@ -1273,7 +1546,10 @@ def route_board(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
-    reserve_escapes: bool = False,
+    rollback: bool = True,
+    net_widths: dict[int, int] | None = None,
+    via_drill: int | None = None,
+    hole_to_hole: int = 0,
 ) -> RouteResult:
     """Convenience wrapper: build a :class:`GridRouter` and route the board."""
     router = GridRouter(
@@ -1292,6 +1568,9 @@ def route_board(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
-        reserve_escapes=reserve_escapes,
+        rollback=rollback,
+        net_widths=net_widths,
+        via_drill=via_drill,
+        hole_to_hole=hole_to_hole,
     )
     return router.route()

src/freeroute/route/pipeline.py

@@ -12,6 +12,8 @@ to DSN units (dividing by the resolution) for the SES ``(wire (path ...))`` and
 
 from __future__ import annotations
 
+import re
+
 from freeroute.board import build_board
 from freeroute.dsn import DsnBoard, parse_dsn
 from freeroute.ses import RoutedVia, RoutedWire, RoutingResult, write_ses
@@ -34,6 +36,25 @@ def _rule_width_dsn(dsn: DsnBoard) -> float:
     return rules[0].value if rules else _DEFAULT_WIDTH_DSN
 
 
+def _net_widths_board(dsn: DsnBoard, scale: int) -> dict[int, int]:
+    """Track width of every net whose class asks for more than the default,
+    in board units, by net number (build_board numbers nets in DSN order)."""
+    default = _rule_width_dsn(dsn)
+    by_name: dict[str, float] = {}
+    for net_class in dsn.net_classes:
+        if not net_class.width_rules:
+            continue
+        width = net_class.width_rules[0].value
+        if width > default:
+            for name in net_class.net_names:
+                by_name[name] = max(by_name.get(name, 0.0), width)
+    return {
+        i + 1: round(by_name[net.name] * scale)
+        for i, net in enumerate(dsn.nets)
+        if net.name in by_name
+    }
+
+
 def _rule_clearance_dsn(dsn: DsnBoard) -> float:
     for rule in dsn.structure_rules.clearance_rules:
         if not rule.class_pairs:  # the layer-wide default clearance
@@ -53,6 +74,20 @@ def _mm_to_board(dsn: DsnBoard, scale: int, value_mm: float | None) -> int | Non
     return round(value_mm / unit_mm * scale)
 
 
+def _via_drill_board(dsn: DsnBoard, scale: int) -> int | None:
+    """The via's drill in board units, from KiCad's padstack name
+    (``Via[0-1]_600:300_um`` is a 600 um pad with a 300 um drill); None when
+    the name does not say, and the pad size stands in for it."""
+    match = re.search(r"_([\d.]+):([\d.]+)_um", _via_padstack(dsn))
+    if not match:
+        return None
+    return round(float(match.group(2)) * _dsn_units_per_um(dsn) * scale)
+
+
+def _dsn_units_per_um(dsn: DsnBoard) -> float:
+    return {"um": 1.0, "mm": 0.001, "mil": 1 / 25.4, "inch": 1 / 25400}.get(dsn.unit, 1.0)
+
+
 def _via_half_board(dsn: DsnBoard, scale: int) -> int | None:
     """Half the via pad's size in board units, from the DSN's via padstack.
 
@@ -83,7 +118,8 @@ def route_dsn_board(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
-    reserve_escapes: bool = False,
+    hole_to_hole_mm: float = 0.25,
+    rollback: bool = True,
 ) -> tuple[RouteResult, int, list[str]]:
     """Route a parsed :class:`DsnBoard`; return the board-unit result, the scale,
     and the layer names. ``layers`` restricts routing to those signal-layer
@@ -107,7 +143,10 @@ def route_dsn_board(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
-        reserve_escapes=reserve_escapes,
+        rollback=rollback,
+        net_widths=_net_widths_board(dsn, scale),
+        via_drill=_via_drill_board(dsn, scale),
+        hole_to_hole=_mm_to_board(dsn, scale, hole_to_hole_mm) or 0,
     )
     return result, scale, [layer.name for layer in dsn.layers]
 
@@ -122,6 +161,9 @@ def _to_routing_result(route, dsn: DsnBoard, scale: int, layer_names: list[str])
     result = RoutingResult()
     for net_no, segments in route.wires.items():
         name = numbers_to_names.get(net_no, str(net_no))
+        # its class's width when every connection of the net went in at it
+        half = getattr(route, "net_half", {}).get(net_no)
+        net_width = 2 * half / scale if half else width_dsn
         for layer_index, path in segments:
             layer_name = layer_names[layer_index] if layer_index < len(layer_names) else "F.Cu"
             coords: list[float] = []
@@ -129,7 +171,7 @@ def _to_routing_result(route, dsn: DsnBoard, scale: int, layer_names: list[str])
                 coords.append(point.x / scale)
                 coords.append(point.y / scale)
             if len(coords) >= 4:
-                result.add_wire(name, RoutedWire(layer=layer_name, width=width_dsn, coords=coords))
+                result.add_wire(name, RoutedWire(layer=layer_name, width=net_width, coords=coords))
     for net_no, locations in route.vias.items():
         name = numbers_to_names.get(net_no, str(net_no))
         for loc in locations:
@@ -137,6 +179,9 @@ def _to_routing_result(route, dsn: DsnBoard, scale: int, layer_names: list[str])
     result.unrouted = [
         (numbers_to_names.get(n, str(n)), a, b, zone) for n, a, b, zone in getattr(route, "failed", [])
     ]
+    result.narrowed = [
+        (numbers_to_names.get(n, str(n)), a, b) for n, a, b in getattr(route, "narrowed", [])
+    ]
     return result
 
 
@@ -151,7 +196,8 @@ def build_routing_result(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
-    reserve_escapes: bool = False,
+    hole_to_hole_mm: float = 0.25,
+    rollback: bool = True,
 ) -> RoutingResult:
     """Route ``dsn`` (grid track) and convert to a DSN-unit RoutingResult."""
     route, scale, layer_names = route_dsn_board(
@@ -159,7 +205,8 @@ def build_routing_result(
         edge_clearance_mm=edge_clearance_mm, resolution=resolution, seed=seed,
         route_first=route_first,
         access_cost=access_cost,
-        reserve_escapes=reserve_escapes,
+        hole_to_hole_mm=hole_to_hole_mm,
+        rollback=rollback,
     )
     return _to_routing_result(route, dsn, scale, layer_names)
 
@@ -178,7 +225,8 @@ def route_dsn_board_exact(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
-    reserve_escapes: bool = False,
+    hole_to_hole_mm: float = 0.25,
+    rollback: bool = True,
 ) -> tuple[ExactRouteResult, int, list[str]]:
     """Route a parsed :class:`DsnBoard` with the exact-geometry (orthogonal,
     DRC-verified) track; return the exact result, the scale, and layer names.
@@ -206,7 +254,10 @@ def route_dsn_board_exact(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
-        reserve_escapes=reserve_escapes,
+        rollback=rollback,
+        net_widths=_net_widths_board(dsn, scale),
+        via_drill=_via_drill_board(dsn, scale),
+        hole_to_hole=_mm_to_board(dsn, scale, hole_to_hole_mm) or 0,
     )
     return exact, scale, [layer.name for layer in dsn.layers]
 
@@ -225,7 +276,8 @@ def build_exact_routing_result(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
-    reserve_escapes: bool = False,
+    hole_to_hole_mm: float = 0.25,
+    rollback: bool = True,
 ) -> RoutingResult:
     """Route ``dsn`` (exact track) and convert to a DSN-unit RoutingResult."""
     exact, scale, layer_names = route_dsn_board_exact(
@@ -241,7 +293,8 @@ def build_exact_routing_result(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
-        reserve_escapes=reserve_escapes,
+        hole_to_hole_mm=hole_to_hole_mm,
+        rollback=rollback,
     )
     return _to_routing_result(exact.result, dsn, scale, layer_names)
 

src/freeroute/route/room_router.py

@@ -515,6 +515,10 @@ def route_board_rooms(
         pin_layers = frozenset(layer for layer in pin.layers if layer in signal_layers)
         if pin_layers:
             tree.insert(TreeShape(next(owner), net, pin_layers, box))
+    for net, copper_layers, box in board.get_fixed_copper():
+        on = frozenset(layer for layer in copper_layers if layer in signal_layers)
+        if on and not box.is_empty():
+            tree.insert(TreeShape(next(owner), net, on, box))
     for obstacle in board.get_obstacle_areas():
         if obstacle.layer not in signal_layers:
             continue

src/freeroute/ses/model.py

@@ -60,6 +60,9 @@ class RoutingResult:
     #: connections the router could not make: (net name, one end, other end,
     #: the zone both ends sit in or "") -- a zone's fill may join the latter
     unrouted: list[tuple[str, str, str, str]] = field(default_factory=list)
+    #: connections of a wider net class that only fitted at the default width
+    #: (net name, one end, other end); their net is written at the default
+    narrowed: list[tuple[str, str, str]] = field(default_factory=list)
 
     def net(self, name: str, *, create: bool = False) -> RoutedNet | None:
         """Return the :class:`RoutedNet` with ``name`` (creating it if asked)."""

tests/route/test_escapes.py

@@ -1,65 +0,0 @@
-"""--reserve-escapes: a crowded pin keeps a way out until it is routed."""
-
-from __future__ import annotations
-
-from pathlib import Path
-
-from freeroute.board import build_board
-from freeroute.dsn import parse_dsn
-from freeroute.route.grid_router import GridRouter
-from freeroute.route.pipeline import (
-    _rule_clearance_dsn,
-    _rule_width_dsn,
-    build_exact_routing_result,
-)
-
-SMD = (Path(__file__).resolve().parent.parent / "dsn" / "fixtures" / "smd_demo.dsn").read_text()
-
-
-def _router():
-    dsn = parse_dsn(SMD)
-    s = dsn.resolution.value
-    router = GridRouter(
-        build_board(dsn),
-        trace_width=round(_rule_width_dsn(dsn) * s),
-        clearance=round(_rule_clearance_dsn(dsn) * s),
-        orthogonal=True,
-        resolution=2,
-        reserve_escapes=True,
-    )
-    conns = router._build_connections()
-    router._conns = conns
-    router._count_pending(conns)
-    router._reserve_escapes(conns)
-    return router, conns
-
-
-def test_a_reserved_escape_is_closed_to_other_nets_and_open_to_its_own():
-    router, conns = _router()
-    assert router._reserved
-    node, claims = next(iter(router._reserved.items()))
-    pin_id, owner = claims[0]
-    other = next(c.net_no for c in conns if c.net_no != owner)
-    cell, layer = node[:2], node[2]
-    assert router._enter_cost(cell, layer, other, True, conns) is None  # even for rip-up
-    assert router._enter_cost(cell, layer, owner, False, conns) is not None or node in router._keepout
-
-
-def test_the_escape_is_released_once_its_pin_is_routed():
-    router, conns = _router()
-    node, claims = next(iter(router._reserved.items()))
-    other = next(c.net_no for c in conns if c.net_no != claims[0][1])
-    cell, layer = node[:2], node[2]
-    assert router._enter_cost(cell, layer, other, False, conns) is None
-    for c in conns:  # every connection routed: no pin is pending any more
-        router._settle(c, -1)
-    released = router._enter_cost(cell, layer, other, False, conns)
-    reserved, router._reserved = router._reserved, {}
-    assert released == router._enter_cost(cell, layer, other, False, conns)
-    router._reserved = reserved
-
-
-def test_reserving_escapes_loses_nothing_on_the_demo_board():
-    plain = build_exact_routing_result(parse_dsn(SMD), resolution=2)
-    reserved = build_exact_routing_result(parse_dsn(SMD), resolution=2, reserve_escapes=True)
-    assert len(reserved.unrouted) <= len(plain.unrouted)

tests/route/test_fixed_wiring.py

@@ -0,0 +1,93 @@
+"""Tracks and vias already on the board (the DSN's wiring) are fixed copper."""
+
+from __future__ import annotations
+
+from freeroute.board import build_board
+from freeroute.dsn import parse_dsn
+from freeroute.route.pipeline import route_dsn_board_exact
+
+_DSN = """(pcb wired (parser) (resolution um 10) (unit um)
+  (structure
+    (layer F.Cu (type signal)) (layer B.Cu (type signal))
+    (boundary (path pcb 0  0 0  30000 0  30000 -20000  0 -20000  0 0))
+    (via "Via[0-1]_600:300_um") (rule (width 250) (clearance 200)))
+  (placement (component S (place A1 5000 -10000 front 0) (place A2 25000 -10000 front 0)))
+  (library
+    (image S (pin smd 1 0 0))
+    (padstack smd (shape (rect F.Cu -400 -400 400 400)) (attach off))
+    (padstack "Via[0-1]_600:300_um" (shape (circle F.Cu 600)) (shape (circle B.Cu 600)) (attach off)))
+  (network (net SIG (pins A1-1 A2-1)) (net GND))
+  (wiring
+    (wire (path F.Cu 400  15000 0  15000 -20000) (net GND) (type route))
+    (via "Via[0-1]_600:300_um"  8000 -14000 (net GND) (type route))))"""
+
+
+def test_wiring_is_read_with_its_nets():
+    dsn = parse_dsn(_DSN)
+    assert [(w.net, w.layer, w.width) for w in dsn.wires] == [("GND", "F.Cu", 400.0)]
+    assert [(v.net, v.x, v.y) for v in dsn.vias] == [("GND", 8000.0, -14000.0)]
+
+
+def test_wiring_is_fixed_copper_and_not_a_connection_to_route():
+    board = build_board(parse_dsn(_DSN))
+    copper = board.get_fixed_copper()
+    gnd = next(n.net_number for n in board.nets if n.name == "GND")
+    assert copper and all(net == gnd for net, _, _ in copper)
+    assert not any(gnd in p.net_nos for p in board.get_pins())
+
+
+def test_other_nets_route_around_a_fixed_track():
+    dsn = parse_dsn(_DSN)
+    exact, scale, names = route_dsn_board_exact(dsn, resolution=2)
+    sig = next(i + 1 for i, n in enumerate(dsn.nets) if n.name == "SIG")
+    assert sig in exact.result.routed_net_numbers
+    assert exact.drc_clean
+    wall = 15000 * scale
+    for layer, pts in exact.result.wires.get(sig, []):
+        if names[layer] != "F.Cu":
+            continue
+        for p, q in zip(pts, pts[1:], strict=False):
+            assert not (min(p.x, q.x) < wall < max(p.x, q.x)), "crossed the GND track on F.Cu"
+
+
+# --- fixed wiring as connectivity ------------------------------------------
+
+_FANOUT = """(pcb fanout (parser) (resolution um 10) (unit um)
+  (structure
+    (layer F.Cu (type signal)) (layer In1.Cu (type power)) (layer In2.Cu (type power))
+    (layer B.Cu (type signal))
+    (boundary (path pcb 0  0 0  30000 0  30000 -20000  0 -20000  0 0))
+    (plane GND (polygon In1.Cu 0  500 -500  29500 -500  29500 -19500  500 -19500  500 -500))
+    (via "Via[0-3]_600:300_um") (rule (width 150) (clearance 150)))
+  (placement (component S (place G1 5000 -10000 front 0) (place A 10000 -10000 front 0)
+                          (place B 25000 -11500 back 0)))
+  (library
+    (image S (pin smd 1 0 0))
+    (padstack smd (shape (rect F.Cu -300 -300 300 300)) (attach off))
+    (padstack "Via[0-3]_600:300_um" (shape (circle F.Cu 600)) (shape (circle B.Cu 600)) (attach off)))
+  (network (net GND (pins G1-1)) (net SIG (pins A-1 B-1)))
+  (wiring
+    (wire (path F.Cu 150  5000 -10000  5000 -11500) (net GND) (type route))
+    (via "Via[0-3]_600:300_um"  5000 -11500 (net GND) (type route))
+    (wire (path F.Cu 150  10000 -10000  10000 -11500) (net SIG) (type route))
+    (via "Via[0-3]_600:300_um"  10000 -11500 (net SIG) (type route))
+    (wire (path F.Cu 300  2000 -2000  8000 -2000) (net GND) (type route))))"""
+
+
+def test_a_pad_fanned_out_to_its_plane_needs_no_route():
+    dsn = parse_dsn(_FANOUT)
+    exact, _scale, _names = route_dsn_board_exact(dsn, resolution=2)
+    gnd = next(i + 1 for i, n in enumerate(dsn.nets) if n.name == "GND")
+    assert exact.result.failed == []
+    assert not exact.result.vias.get(gnd) and not exact.result.wires.get(gnd)
+
+
+def test_a_fanned_out_signal_is_routed_from_its_via():
+    # B is on the bottom face, level with A's fan-out via: starting from that
+    # via on B.Cu is the cheapest way, and needs no via of its own
+    dsn = parse_dsn(_FANOUT)
+    exact, scale, names = route_dsn_board_exact(dsn, resolution=2)
+    sig = next(i + 1 for i, n in enumerate(dsn.nets) if n.name == "SIG")
+    assert sig in exact.result.routed_net_numbers
+    assert not exact.result.vias.get(sig), "the fan-out via is already there"
+    assert {names[layer] for layer, _ in exact.result.wires[sig]} == {"B.Cu"}

tests/route/test_net_widths.py

@@ -0,0 +1,42 @@
+"""Net classes wider than the default are routed at their width where it fits."""
+
+from __future__ import annotations
+
+from freeroute.dsn import parse_dsn
+from freeroute.route.pipeline import build_exact_routing_result
+
+_BOARD = """(pcb widths (parser) (resolution um 10) (unit um)
+  (structure
+    (layer F.Cu (type signal))
+    (boundary (path pcb 0  0 0  20000 0  20000 -10000  0 -10000  0 0))
+    {keepouts}
+    (rule (width 150) (clearance 150)))
+  (placement (component S (place P1 2000 -5000 front 0) (place P2 18000 -5000 front 0)))
+  (library (image S (pin pad 1 0 0)) (padstack pad (shape (rect F.Cu -600 -600 600 600)) (attach off)))
+  (network (net PWR (pins P1-1 P2-1))
+    (class Power PWR (rule (width 400) (clearance 150)))))"""
+
+# two keepouts leave a 0.65 mm channel: room for 0.15 mm (0.45), not for 0.4 mm (0.7)
+_CHANNEL = (
+    '(keepout "" (polygon F.Cu 0  9000 0  11000 0  11000 -4675  9000 -4675))\n'
+    '    (keepout "" (polygon F.Cu 0  9000 -5325  11000 -5325  11000 -10000  9000 -10000))'
+)
+
+
+def _route(keepouts=""):
+    return build_exact_routing_result(parse_dsn(_BOARD.format(keepouts=keepouts)), resolution=2)
+
+
+def test_a_wider_class_is_routed_and_written_at_its_width():
+    result = _route()
+    assert result.unrouted == [] and result.narrowed == []
+    widths = {w.width for net in result.nets for w in net.wires}
+    assert widths == {400.0}
+
+
+def test_a_wider_class_that_does_not_fit_falls_back_to_the_default():
+    result = _route(_CHANNEL)
+    assert result.unrouted == []
+    assert [net for net, _a, _b in result.narrowed] == ["PWR"]
+    widths = {w.width for net in result.nets for w in net.wires}
+    assert widths == {150.0}

tests/route/test_real_board_geometry.py

@@ -202,6 +202,18 @@ def test_smd_pads_reach_an_inner_plane_by_their_own_via():
     assert all(names[layer] in ("F.Cu", "B.Cu") for segs in result.result.wires.values() for layer, _ in segs)
 
 
+def test_a_pad_outside_the_plane_routes_to_it():
+    # G1 sits left of a plane that covers only the right half, so its route
+    # has to reach the plane's cells: those ends are the plane, not a pin
+    dsn_text = _four_layer_dsn().replace(
+        "(plane GND (polygon In1.Cu 0  500 -500  29500 -500  29500 -29500  500 -29500  500 -500))",
+        "(plane GND (polygon In1.Cu 0  15000 -500  29500 -500  29500 -29500  15000 -29500  15000 -500))",
+    )
+    result, _scale, _names = route_dsn_board_exact(parse_dsn(dsn_text))
+    gnd = next(i + 1 for i, n in enumerate(parse_dsn(dsn_text).nets) if n.name == "GND")
+    assert gnd in result.result.routed_net_numbers
+
+
 def test_a_through_hole_pad_inside_a_plane_needs_no_route():
     from freeroute.route.grid_router import _connected_groups
 
@@ -211,3 +223,29 @@ def test_a_through_hole_pad_inside_a_plane_needs_no_route():
     groups = _connected_groups(gnd_pins, plane, frozenset(id(z) for z in plane))
     hub = next(g for g in groups if g[1])
     assert [p.component_ref for p in hub[0]] == ["GT"]
+
+
+def test_a_pad_inside_a_via_keepout_reaches_the_plane_by_a_via_outside_it():
+    # a sensor's GND pad: vias are forbidden under the body, so the route
+    # has to leave on the top layer and drop to the plane past the keepout
+    dsn = parse_dsn("""(pcb repro (parser) (resolution um 10) (unit um)
+  (structure
+    (layer F.Cu (type signal)) (layer In1.Cu (type power)) (layer In2.Cu (type power))
+    (layer B.Cu (type signal))
+    (boundary (path pcb 0  0 0  20000 0  20000 -20000  0 -20000  0 0))
+    (plane GND (polygon In1.Cu 0  500 -500  19500 -500  19500 -19500  500 -19500  500 -500))
+    (via_keepout "" (polygon signal 0  8500 -8500  11500 -8500  11500 -11500  8500 -11500  8500 -8500))
+    (via "Via[0-3]_600:300_um") (rule (width 150) (clearance 150)))
+  (placement (component S (place G1 10000 -10000 front 0)))
+  (library
+    (image S (pin smd 1 0 0))
+    (padstack smd (shape (rect F.Cu -175 -300 175 300)) (attach off))
+    (padstack "Via[0-3]_600:300_um" (shape (circle F.Cu 600)) (shape (circle B.Cu 600)) (attach off)))
+  (network (net GND (pins G1-1))))""")
+    exact, scale, _names = route_dsn_board_exact(dsn, resolution=2)
+    assert exact.result.failed == []
+    (via,) = exact.result.vias[1]
+    half = 300 * scale  # the via's radius
+    outside = (via.x + half <= 8500 * scale or via.x - half >= 11500 * scale
+               or via.y - half >= -8500 * scale or via.y + half <= -11500 * scale)
+    assert outside, f"via at {via} is inside the via keepout"

tests/route/test_rollback.py

@@ -0,0 +1,43 @@
+"""--rollback: a rip-up that loses connections is undone, leaving no trace."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+from freeroute.board import build_board
+from freeroute.dsn import parse_dsn
+from freeroute.route.grid_router import GridRouter
+from freeroute.route.pipeline import _rule_clearance_dsn, _rule_width_dsn, route_dsn_board
+
+FIXTURES = Path(__file__).resolve().parent.parent / "dsn" / "fixtures"
+
+
+def _routed_router(name):
+    dsn = parse_dsn((FIXTURES / name).read_text())
+    s = dsn.resolution.value
+    router = GridRouter(
+        build_board(dsn),
+        trace_width=round(_rule_width_dsn(dsn) * s),
+        clearance=round(_rule_clearance_dsn(dsn) * s),
+        rollback=True,
+    )
+    return router, router.route()
+
+
+@pytest.mark.parametrize("name", ["ripup_needed.dsn", "true_density.dsn", "kicad_routable.dsn"])
+def test_occupancy_only_holds_routed_connections(name):
+    router, _ = _routed_router(name)
+    conns = router._conns
+    assert all(conns[i].routed for i in router._cell_owner.values())
+    assert all(conns[i].routed for i in router._via_owner.values())
+    assert all(conns[i].routed for claims in router._halo.values() for i in claims)
+
+
+@pytest.mark.parametrize("name", ["ripup_needed.dsn", "true_density.dsn", "kicad_routable.dsn"])
+def test_rollback_never_routes_fewer_than_plain_rip_up(name):
+    text = (FIXTURES / name).read_text()
+    plain, _, _ = route_dsn_board(parse_dsn(text), rollback=False)
+    undo, _, _ = route_dsn_board(parse_dsn(text))
+    assert undo.unrouted <= plain.unrouted

tests/route/test_via_spacing.py

@@ -0,0 +1,56 @@
+"""Vias keep hole-to-hole spacing, even within one net."""
+
+from __future__ import annotations
+
+import itertools
+import math
+
+from freeroute.dsn import parse_dsn
+from freeroute.route.pipeline import route_dsn_board_exact
+
+# four GND pads 0.5 mm apart over a GND plane: each drops a via to the plane
+_DSN = """(pcb holes (parser) (resolution um 10) (unit um)
+  (structure
+    (layer F.Cu (type signal)) (layer In1.Cu (type power)) (layer In2.Cu (type power))
+    (layer B.Cu (type signal))
+    (boundary (path pcb 0  0 0  20000 0  20000 -20000  0 -20000  0 0))
+    (plane GND (polygon In1.Cu 0  500 -500  19500 -500  19500 -19500  500 -19500  500 -500))
+    (via "Via[0-3]_500:300_um") (rule (width 150) (clearance 150)))
+  (placement (component S (place G1 9000 -10000 front 0) (place G2 9500 -10000 front 0)
+                          (place G3 10000 -10000 front 0) (place G4 10500 -10000 front 0)))
+  (library
+    (image S (pin smd 1 0 0))
+    (padstack smd (shape (rect F.Cu -150 -300 150 300)) (attach off))
+    (padstack "Via[0-3]_500:300_um" (shape (circle F.Cu 500)) (shape (circle B.Cu 500)) (attach off)))
+  (network (net GND (pins G1-1 G2-1 G3-1 G4-1))))"""
+
+
+def test_a_nets_own_vias_keep_hole_to_hole_spacing():
+    dsn = parse_dsn(_DSN)
+    exact, scale, _ = route_dsn_board_exact(dsn, resolution=2)
+    assert exact.result.failed == []
+    vias = exact.result.vias[1]
+    assert len(set(vias)) == len(vias), "a via written twice"
+    need = (300 + 250) * scale  # drill + 0.25 mm, centre to centre
+    for a, b in itertools.combinations(vias, 2):
+        assert math.hypot(a.x - b.x, a.y - b.y) >= need, f"vias at {a} and {b} too close"
+
+
+def test_connections_sharing_a_plane_via_write_it_once():
+    # eight GND pads 0.4 mm apart: the hole spacing makes several of them
+    # end on the same plane via, which must come out once, not once each
+    pads = " ".join(f"(place G{i} {9000 + 400 * i} -10000 front 0)" for i in range(8))
+    pins = " ".join(f"G{i}-1" for i in range(8))
+    dsn = parse_dsn(
+        _DSN.replace(
+            "(place G1 9000 -10000 front 0) (place G2 9500 -10000 front 0)\n"
+            "                          (place G3 10000 -10000 front 0) (place G4 10500 -10000 front 0)",
+            pads,
+        )
+        .replace("(pins G1-1 G2-1 G3-1 G4-1)", f"(pins {pins})")
+        .replace("(rect F.Cu -150 -300 150 300)", "(rect F.Cu -125 -300 125 300)")
+    )
+    exact, _scale, _ = route_dsn_board_exact(dsn, resolution=2)
+    vias = exact.result.vias[1]
+    assert len(vias) < 8, "no via is shared, so this board no longer tests sharing"
+    assert len(set(vias)) == len(vias), "a shared via written more than once"

tests/test_cli.py

@@ -158,7 +158,7 @@ def test_cli_supported_combinations_are_accepted(tmp_path):
         "orders": ["--orders", "2"],
         "promote": ["--promote-failures", "2"],
         "access": ["--access-cost", "5"],
-        "escapes": ["--reserve-escapes"],
+        "rollback": ["--no-rollback"],
     }
     for engine, options in ENGINE_OPTIONS.items():
         for option in options: