Let pins on turned fine-pitch pads leave along the pad's axis

A QFN placed at 45 degrees had no exit on the grid: every horizontal or
vertical step from a pin passes its neighbours inside clearance. A pin whose
pad is turned more than ten degrees off the grid axes now leaves along the
pad's own axis, away from the part, until an L from there to a grid cell
clears every other net's pad, then searches as usual. The slanted leg is
checked and stored as an exact slab (segment_slab), not its bounding box,
in the grid stub checks and in the exact engine.

Where pins leave side by side, a cell names only its first owner, so stubs
are also indexed per cell for every connection near them; the exact
stub-vs-stub check, trace entry and rip-up all consult that index. A pin
with an axis exit and no clear cell reports no way out instead of falling
back to a cell on another net's route. diagnose.py replays with the exits.

bench/diagnose.py

@@ -32,8 +32,10 @@ from freeroute.route.exact_router import route_board_exact
 from freeroute.route.grid_router import GridRouter, _ends_of
 from freeroute.route.pipeline import (
     _mm_to_board,
+    _net_widths_board,
     _rule_clearance_dsn,
     _rule_width_dsn,
+    _via_drill_board,
     _via_half_board,
 )
 
@@ -183,7 +185,8 @@ def _flood(router: GridRouter, pin, net_no: int, conns) -> tuple[int, Counter]:
 
 def diagnose(
     dsn_text: str, edge_clearance_mm: float | None, resolution: int = 2, shove: bool = False,
-    access_cost: float = 0.0,
+    access_cost: float = 0.0, hole_to_hole_mm: float = 0.25, seed: int | None = None,
+    negotiate: int = 0,
 ) -> dict:
     dsn = parse_dsn(dsn_text)
     names = {i + 1: n.name for i, n in enumerate(dsn.nets)}
@@ -199,6 +202,12 @@ def diagnose(
         resolution=resolution,
         shove=shove,
         access_cost=access_cost,
+        seed=seed,
+        negotiate=negotiate,
+        # the product's configuration: net-class widths and hole spacing
+        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,
     )
     routed = seen["router"]
     best = routed._diag_best
@@ -206,6 +215,8 @@ def diagnose(
 
     # the board as the best pass left it
     state = _fresh(seen)
+    # pins on turned pads leave along their pad's axis: replay with the same exits
+    state._axis_exits = dict(routed._axis_exits)
     conns = state._conns
     for idx, (path, a_end, b_end) in best.items():
         conns[idx].a_end, conns[idx].b_end = a_end, b_end
@@ -270,11 +281,14 @@ def main(argv: list[str] | None = None) -> int:
     ap.add_argument("--grid-resolution", type=int, default=2, metavar="K")
     ap.add_argument("--shove", action="store_true", help="as mckicad routes")
     ap.add_argument("--access-cost", type=float, default=0.0)
+    ap.add_argument("--seed", type=int, help="route in this shuffled order, as bench.py does")
+    ap.add_argument("--negotiate", type=int, default=0, metavar="N", help="as the router's --negotiate")
+    ap.add_argument("--hole-to-hole", type=float, default=0.25, metavar="MM")
     ap.add_argument("--json", type=Path, help="also write the full table here")
     args = ap.parse_args(argv)
 
     report = diagnose(args.dsn.read_text(), args.edge_clearance, args.grid_resolution, args.shove,
-                      args.access_cost)
+                      args.access_cost, args.hole_to_hole, args.seed, args.negotiate)
     for row in report["failures"]:
         extra = ""
         for w in row.get("walled", []):

bench/drc_check.sh

@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+# Route one KiCad board with freeroute and judge the result with KiCad's DRC.
+#
+#   bench/drc_check.sh [--keep] <board.kicad_pcb> <out-dir> [freeroute args...]
+#
+# Copies the board (and its .kicad_pro) into <out-dir>, strips its tracks and
+# vias unless --keep is given (then they reach the router as fixed wiring),
+# exports the DSN through mckicad, routes, applies the session, and runs DRC
+# with zones refilled at every severity. Prints one line: time, copper added,
+# shorts, opens, hole problems (whatever severity the board gives them) and
+# the other errors. The source board is never touched.
+#
+# FREEROUTE (default: this checkout's .venv/bin/freeroute) and MCK (default
+# ~/claude/mckicad) pick the builds to judge.
+set -euo pipefail
+keep=0
+if [[ "${1:-}" == "--keep" ]]; then keep=1; shift; fi
+src="$1"; out="$2"; shift 2
+here="$(cd "$(dirname "$0")/.." && pwd)"
+FREEROUTE="${FREEROUTE:-$here/.venv/bin/freeroute}"
+MCK="${MCK:-$HOME/claude/mckicad}"
+rm -rf "$out"; mkdir -p "$out"
+cp "${src%.kicad_pcb}.kicad_pro" "$out/board.kicad_pro" 2>/dev/null || true
+
+if [[ $keep == 1 ]]; then
+    cp "$src" "$out/board.kicad_pcb"
+else
+    (cd "$MCK" && uv run --no-sync python - "$src" "$out/board.kicad_pcb" <<'EOF'
+import sys
+from mckicad.utils.sexp_tree import parse
+text = open(sys.argv[1]).read()
+spans = sorted((c.span for c in parse(text).children if c.tag in ("segment", "arc", "via")), reverse=True)
+for a, b in spans:
+    text = text[:a] + text[b:]
+open(sys.argv[2], "w").write(text)
+EOF
+    )
+fi
+
+(cd "$MCK" && uv run --no-sync python -c "
+from mckicad.utils.freerouting import FreeRoutingEngine
+assert FreeRoutingEngine().export_dsn_from_kicad('$out/board.kicad_pcb', '$out/board.dsn', {})") \
+    >/dev/null 2>&1 || { echo "$out: DSN export failed"; exit 1; }
+
+start=$(date +%s.%N)
+"$FREEROUTE" "$out/board.dsn" -do "$out/board.ses" "$@" >"$out/route.log" 2>&1 || true
+secs=$(python3 -c "print(round($(date +%s.%N)-$start,1))")
+[[ -s "$out/board.ses" ]] || { echo "$out: no session ($(tail -1 "$out/route.log"))"; exit 1; }
+
+(cd "$MCK" && uv run --no-sync python -c "
+from mckicad.utils.ses_apply import apply_ses_to_board as a
+r = a('$out/board.kicad_pcb', '$out/board.ses', '$out/board.kicad_pcb')
+print(r['segments_added'], r['vias_added'])" 2>/dev/null) >"$out/apply.txt"
+
+kicad-cli pcb drc --refill-zones --format json --severity-all \
+    -o "$out/drc.json" "$out/board.kicad_pcb" >/dev/null 2>&1 || true
+python3 - "$out" "$secs" <<'EOF'
+import collections, json, sys
+out, secs = sys.argv[1:]
+seg, via = open(f"{out}/apply.txt").read().split()
+d = json.load(open(f"{out}/drc.json"))
+errors = collections.Counter(v["type"] for v in d["violations"] if v.get("severity") == "error")
+other = collections.Counter(v["type"] for v in d["violations"] if v.get("severity") != "error")
+holes = {k: errors.pop(k, 0) + other.get(k, 0) for k in ("holes_co_located", "hole_to_hole")}
+print(f"{out}: {secs}s  {seg} seg {via} via  shorts {errors.pop('shorting_items', 0)}  "
+      f"opens {len(d.get('unconnected_items', []))}  holes {holes}  errors {dict(errors)}")
+EOF

src/freeroute/board/build.py

@@ -12,9 +12,10 @@ model. It mirrors what FreeRouting's ``Structure.create_board`` / ``Library`` /
 * padstacks x placement -> :class:`Pin` items
 * keepouts -> :class:`ObstacleArea` items
 
-Pad geometry: a rectangle pad becomes an exact :class:`IntBox`; a circle pad its
-bounding box (documented approximation pending an exact circle tile); a convex
-polygon pad an exact :class:`Simplex`. Every pad is placed centred on its pin
+Pad geometry: a rectangle pad becomes an exact :class:`IntBox`; a circle pad a
+16-sided :class:`Simplex` drawn just outside it (its corners stand out by 2% of
+the radius, where the bounding box's stood out by 41%); a convex polygon pad an
+exact :class:`Simplex`. Every pad is placed centred on its pin
 location, so it contains that location by construction. Component rotation is
 applied to the pin position; the pad tile itself is not rotated (irrelevant to
 the containment invariant, and pads are centre-symmetric in practice).
@@ -249,7 +250,7 @@ def _placed_pad_tile(shape: Shape, place, dsn_pin, transform: CoordinateTransfor
         r = round(transform.dsn_to_board(shape.diameter / 2))
         cx = round(transform.dsn_to_board(centre.x))
         cy = round(transform.dsn_to_board(centre.y))
-        return IntBox(cx - r, cy - r, cx + r, cy + r)
+        return _circle_tile(cx, cy, r)
     if isinstance(shape, Rectangle):
         x0, y0, x1, y1 = shape.coords[:4]
         corners = [(x0, y0), (x1, y0), (x1, y1), (x0, y1)]
@@ -268,15 +269,65 @@ def _placed_pad_tile(shape: Shape, place, dsn_pin, transform: CoordinateTransfor
     for x, y in corners:
         p = _to_board_offset(place, x, y, dsn_pin.rotation)
         pts.append(IntPoint(round(transform.dsn_to_board(p.x)), round(transform.dsn_to_board(p.y))))
-    if len(pts) >= 3:
-        simplex = Simplex.from_corners(pts)
-        if not simplex.is_empty():
-            return simplex
+    # An oval's padded corners are not in outline order, and a mirrored
+    # part reverses the winding: take the convex hull, then either winding.
+    hull = _convex_hull(pts)
+    if len(hull) >= 3:
+        for corners in (hull, hull[::-1]):
+            simplex = Simplex.from_corners(corners)
+            if not simplex.is_empty():
+                return simplex
     xs = [p.x for p in pts] or [0]
     ys = [p.y for p in pts] or [0]
     return IntBox(min(xs), min(ys), max(xs), max(ys))
 
 
+_CIRCLE_SIDES = 16
+
+
+def _circle_tile(cx: int, cy: int, r: int):
+    """A polygon around the circle, every side touching it. A square around a
+    big round pad (a mounting hole) puts phantom copper in its corners that
+    blocks legal routes past it; this stays outside the circle, so the router
+    is still never closer than KiCad measures."""
+    if r < 8:
+        return IntBox(cx - r, cy - r, cx + r, cy + r)
+    reach = r / math.cos(math.pi / _CIRCLE_SIDES)
+    corners = []
+    for k in range(_CIRCLE_SIDES):
+        a = (k + 0.5) * 2 * math.pi / _CIRCLE_SIDES
+        dx, dy = reach * math.cos(a), reach * math.sin(a)
+        # round away from the centre so the polygon never cuts into the circle
+        corners.append(IntPoint(cx + math.copysign(math.ceil(abs(dx)), dx),
+                                cy + math.copysign(math.ceil(abs(dy)), dy)))
+    corners = [IntPoint(int(p.x), int(p.y)) for p in corners]
+    for winding in (corners, corners[::-1]):
+        simplex = Simplex.from_corners(winding)
+        if not simplex.is_empty():
+            return simplex
+    return IntBox(cx - r, cy - r, cx + r, cy + r)
+
+
+def _convex_hull(pts: list[IntPoint]) -> list[IntPoint]:
+    """The convex hull of ``pts`` counter-clockwise, collinear points dropped."""
+    ps = sorted({(p.x, p.y) for p in pts})
+    if len(ps) < 3:
+        return [IntPoint(x, y) for x, y in ps]
+
+    def cross(o, a, b):
+        return (a[0] - o[0]) * (b[1] - o[1]) - (a[1] - o[1]) * (b[0] - o[0])
+
+    def half(points):
+        out: list[tuple[int, int]] = []
+        for p in points:
+            while len(out) >= 2 and cross(out[-2], out[-1], p) <= 0:
+                out.pop()
+            out.append(p)
+        return out[:-1]
+
+    return [IntPoint(x, y) for x, y in half(ps) + half(ps[::-1])]
+
+
 def _pad_tile(shape: Shape, transform: CoordinateTransform):
     """A board-relative pad tile from a DSN padstack shape (centred near origin)."""
     if isinstance(shape, Rectangle):
@@ -286,7 +337,7 @@ def _pad_tile(shape: Shape, transform: CoordinateTransform):
         r = round(transform.dsn_to_board(shape.diameter / 2))
         cx = round(transform.dsn_to_board(shape.center_x))
         cy = round(transform.dsn_to_board(shape.center_y))
-        return IntBox(cx - r, cy - r, cx + r, cy + r)  # bounding-box approximation
+        return _circle_tile(cx, cy, r)
     if isinstance(shape, (Polygon, Path)):
         coords = shape.coords
         pts = [

src/freeroute/board/search_tree.py

@@ -18,7 +18,7 @@ from __future__ import annotations
 
 from dataclasses import dataclass
 
-from freeroute.geometry import IntBox, Simplex, overlaps_2d, segment_octagon
+from freeroute.geometry import IntBox, IntPoint, Simplex, overlaps_2d, segment_octagon, segment_slab
 
 __all__ = ["TreeShape", "ShapeSearchTree"]
 
@@ -63,7 +63,9 @@ class TreeShape:
         segment swept by ``half_width + clearance`` (exact integer superset)."""
         if self.seg is None:
             return self.tile.offset(clearance)
-        a, b, half_width = self.seg
+        a, b, half_width = self.seg[-3:]
+        if self.seg[0] == "slab":  # a slanted pin exit, at any angle
+            return segment_slab(a, b, half_width + clearance)
         return segment_octagon(a, b, half_width + clearance)
 
 
@@ -151,6 +153,25 @@ class ShapeSearchTree:
                 return True
         return False
 
+    def segment_conflict(
+        self, a: IntPoint, b: IntPoint, half_width: int, net_no: int, layer: int,
+        clearance: int, kind: str = "wire",
+    ) -> bool:
+        """:meth:`clearance_conflict` for a slanted segment, checked on its
+        exact swept copper instead of its bounding box (which would reach the
+        neighbouring pads of a pin leaving along its turned pad's axis)."""
+        copper = segment_slab(a, b, half_width)
+        grown = segment_slab(a, b, half_width + clearance)
+        for shape in self.overlapping(grown.bounding_box()):
+            if shape.net_no == net_no or not shape.on_layer(layer):
+                continue
+            if shape.blocks != "all" and shape.blocks != kind + "s":
+                continue
+            other = shape.exact if shape.exact is not None else shape.tile
+            if overlaps_2d(copper if not shape.clearance else grown, other):
+                return True
+        return False
+
     def rule_area_overlap(self, box: IntBox, layer: int, kind: str = "wire") -> bool:
         """True if ``box`` overlaps a rule area on ``layer`` that stops ``kind``."""
         for shape in self.overlapping(box):
@@ -188,6 +209,8 @@ class ShapeSearchTree:
         overlap). Static pad-vs-pad spacing in the source design is not counted.
         """
         for shape in self.all_shapes():
+            if not shape.routed:
+                continue  # a pair with routed copper is checked from that side
             expanded = shape.tile.offset(clearance)
             grown = None  # exact clearance region, built lazily only for diagonals
             for other in self.overlapping(expanded):

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", "rollback"}),
-    "exact": frozenset({"shove", "diagonal", "rip_up", "max_passes", "seed", "orders", "promote", "access", "rollback"}),
+    "grid": frozenset({"rip_up", "max_passes", "seed", "orders", "promote", "access", "negotiate", "rollback"}),
+    "exact": frozenset({"shove", "diagonal", "rip_up", "max_passes", "seed", "orders", "promote", "access", "negotiate", "rollback"}),
     "room": frozenset({"shove", "pack"}),
 }
 
@@ -46,6 +46,7 @@ _FLAG_NAMES = {
     "orders": "--orders",
     "promote": "--promote-failures",
     "access": "--access-cost",
+    "negotiate": "--negotiate",
     "rollback": "--no-rollback",
 }
 
@@ -167,6 +168,14 @@ def build_parser() -> argparse.ArgumentParser:
         help="grid and exact engines: extra cost for a route to pass where it would close "
         "another pin's way out while that pin still has connections to route (default 0: off)",
     )
+    parser.add_argument(
+        "--negotiate",
+        type=int,
+        metavar="N",
+        help="grid and exact engines: before routing, N rounds of negotiation on the empty "
+        "board, where routes may share space at a price that rises where they compete; "
+        "the contested cells then cost extra in the real routing (default 0: off)",
+    )
     parser.add_argument(
         "--no-rollback",
         dest="rollback",
@@ -212,6 +221,7 @@ 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),
+            ("negotiate", args.negotiate is not None),
             ("rollback", not args.rollback),
         )
         if asked
@@ -247,6 +257,7 @@ 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,
+            "negotiate": args.negotiate or 0,
             "hole_to_hole_mm": args.hole_to_hole,
             "rollback": args.rollback,
         }
@@ -258,6 +269,7 @@ 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,
+            "negotiate": args.negotiate or 0,
             "hole_to_hole_mm": args.hole_to_hole,
             "rollback": args.rollback,
         }

src/freeroute/geometry/__init__.py

@@ -21,7 +21,7 @@ from .direction import Direction, IntDirection
 from .float_point import FloatPoint
 from .limits import CRIT_DOUBLE, CRIT_INT
 from .line import Line
-from .octagon import ceil_sqrt2, overlaps_2d, segment_octagon
+from .octagon import ceil_sqrt2, overlaps_2d, segment_octagon, segment_slab
 from .point import IntPoint, Point, RationalPoint, point, rational_point
 from .polygon import Polygon
 from .polygon_shape import PolygonShape
@@ -59,5 +59,6 @@ __all__ = [
     "shove_segment",
     "ceil_sqrt2",
     "segment_octagon",
+    "segment_slab",
     "overlaps_2d",
 ]

src/freeroute/geometry/octagon.py

@@ -29,7 +29,7 @@ from .line import Line
 from .point import IntPoint
 from .simplex import Simplex
 
-__all__ = ["ceil_sqrt2", "segment_octagon", "overlaps_2d"]
+__all__ = ["ceil_sqrt2", "segment_octagon", "segment_slab", "overlaps_2d"]
 
 
 def ceil_sqrt2(radius: int) -> int:
@@ -82,6 +82,46 @@ def segment_octagon(a: IntPoint, b: IntPoint, radius: int) -> Simplex:
     return Simplex.get_instance(lines)
 
 
+def segment_slab(a: IntPoint, b: IntPoint, radius: int) -> Simplex:
+    """Convex cover of segment ``a``-``b`` swept by ``radius``, at any angle.
+
+    The rectangle along the segment, ``radius`` either side, with flush ends
+    like :func:`polyline.segment_box`: the ends of a trace leg sit on a pad or
+    on the square corner tile of the next leg, which cover them. Corners are
+    rounded away from the middle and the radius gets one unit more, so the
+    side bounds never under-report, and it stays tight for a slanted segment
+    off the 45-degree lines (a pin leaving along its pad's axis on a part
+    turned 30 degrees).
+    """
+    dx, dy = b.x - a.x, b.y - a.y
+    length = math.hypot(dx, dy)
+    r = max(radius, 0) + 1
+    if length == 0:
+        return Simplex.from_corners([
+            IntPoint(a.x - r, a.y - r), IntPoint(a.x + r, a.y - r),
+            IntPoint(a.x + r, a.y + r), IntPoint(a.x - r, a.y + r),
+        ])
+    ux, uy = dx / length, dy / length
+    nx, ny = -uy, ux
+    mx, my = (a.x + b.x) / 2, (a.y + b.y) / 2
+
+    def out(x: float, y: float) -> IntPoint:
+        return IntPoint(math.ceil(x) if x >= mx else math.floor(x),
+                        math.ceil(y) if y >= my else math.floor(y))
+
+    corners = [
+        out(a.x + nx * r, a.y + ny * r),
+        out(b.x + nx * r, b.y + ny * r),
+        out(b.x - nx * r, b.y - ny * r),
+        out(a.x - nx * r, a.y - ny * r),
+    ]
+    for winding in (corners, corners[::-1]):
+        slab = Simplex.from_corners(winding)
+        if not slab.is_empty():
+            return slab
+    return Simplex(())
+
+
 def overlaps_2d(shape_a, shape_b) -> bool:
     """True if the two convex tiles share 2-D area (a real clearance overlap).
 

src/freeroute/route/exact_router.py

@@ -38,8 +38,10 @@ from freeroute.geometry import (
     IntPoint,
     Polyline,
     PolylineShape,
+    Simplex,
     segment_box,
     segment_octagon,
+    segment_slab,
     shove_segment,
 )
 from freeroute.geometry.polyline import corner_box
@@ -98,6 +100,7 @@ def route_board_exact(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
+    negotiate: int = 0,
     rollback: bool = True,
     net_widths: dict[int, int] | None = None,
     via_drill: int | None = None,
@@ -133,6 +136,7 @@ def route_board_exact(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
+        negotiate=negotiate,
         rollback=rollback,
         net_widths=net_widths,
         via_drill=via_drill,
@@ -154,7 +158,9 @@ def route_board_exact(
         net = pin.net_nos[0] if pin.net_nos else -1
         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))
+            # a rotated pad is checked against its outline, not its box
+            exact = pin.shape if _is_rotated(pin.shape) else None
+            tree.insert(TreeShape(next(owner), net, pin_layers, box, exact=exact))
     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():
@@ -195,16 +201,23 @@ def route_board_exact(
         zip(result.connections, ends_list, strict=False), key=lambda c: c[0][0]
     ):
         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))
+        pieces = _copper_pieces(wires, vias, wire_half, via_layers, via_half)
+        boxes = [(box, box_layers) for box, box_layers, _ in pieces]
+        wire_count = len(_copper_pieces(wires, [], wire_half, via_layers, via_half))
         if any(
-            tree.clearance_conflict(
-                box, net_no, layer, clearance, "wire" if i < wire_count else "via"
+            (
+                tree.segment_conflict(*seg, wire_half, net_no, layer, clearance)
+                if seg is not None
+                else tree.clearance_conflict(
+                    box, net_no, layer, clearance, "wire" if i < wire_count else "via"
+                )
             )
-            for i, (box, box_layers) in enumerate(boxes)
+            for i, (box, box_layers, seg) in enumerate(pieces)
             for layer in box_layers
         ) 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)
+            outline is not None and not _inside_outline(
+                outline, boxes[:wire_count], vias, (via_half or wire_half) + edge, edge
+            )
         ):
             rejected.append((net_no, *ends))
             continue  # exact-clearance conflict -> drop (may be recovered by shove)
@@ -218,9 +231,15 @@ def route_board_exact(
             v for v in dict.fromkeys(vias)
             if v not in acc.vias and not _on_fixed_via(net_no, v, fixed_vias, via_half)
         )
-        for box, box_layers in boxes:
+        for box, box_layers, seg in pieces:
             oid = next(owner)
-            tree.insert(TreeShape(oid, net_no, box_layers, box, routed=True))
+            if seg is None:
+                tree.insert(TreeShape(oid, net_no, box_layers, box, routed=True))
+            else:  # a slanted pin exit: its exact copper, rebuilt for the DRC check
+                tree.insert(TreeShape(
+                    oid, net_no, box_layers, box, routed=True,
+                    exact=segment_slab(*seg, wire_half), seg=("slab", *seg, wire_half),
+                ))
             acc.owners.append(oid)
 
     accepted_before_recovery = set(accepted)
@@ -655,6 +674,27 @@ def _on_fixed_via(net_no, point, fixed_vias, via_half) -> bool:
     )
 
 
+def _copper_pieces(wires, vias, half_width, via_layers, via_half=None):
+    """Like :func:`_copper_boxes`, but a slanted wire segment (a pin leaving
+    along a turned pad's axis) comes with its end points, so it can be checked
+    on its exact copper: ``(box, layers, (a, b) or None)``."""
+    via_half = via_half or half_width
+    pieces: list[tuple[IntBox, frozenset[int], tuple | None]] = []
+    for layer, points in wires:
+        on = frozenset({layer})
+        for a, b in zip(points, points[1:], strict=False):
+            if a.x == b.x or a.y == b.y:
+                pieces.append((segment_box(a, b, half_width), on, None))
+            else:
+                pieces.append((segment_slab(a, b, half_width).bounding_box(), on, (a, b)))
+        for c in points[1:-1]:
+            pieces.append((corner_box(c, half_width), on, None))
+    for loc in vias:
+        vbox = IntBox(loc.x - via_half, loc.y - via_half, loc.x + via_half, loc.y + via_half)
+        pieces.append((vbox, via_layers, None))
+    return pieces
+
+
 def _copper_boxes(wires, vias, half_width, via_layers, via_half=None):
     via_half = via_half or half_width
     boxes: list[tuple[IntBox, frozenset[int]]] = []
@@ -667,6 +707,19 @@ def _copper_boxes(wires, vias, half_width, via_layers, via_half=None):
     return boxes
 
 
+def _inside_outline(outline, wire_boxes, vias, via_reach, edge) -> bool:
+    """Copper inside the board, ``edge`` from its outline. A via is round, as
+    the grid and KiCad take it: its square box would reach past a chamfered
+    corner where the via itself does not."""
+    return all(outline.box_clear(b, edge) for b, _ in wire_boxes) and all(
+        outline.point_clear(v, via_reach) for v in vias
+    )
+
+
+def _is_rotated(shape) -> bool:
+    return isinstance(shape, Simplex) and not shape.is_int_box()
+
+
 def _net_pins(board: BasicBoard, net_no: int, signal_layers) -> list[Pin]:
     return [
         pin

src/freeroute/route/grid_router.py

@@ -27,13 +27,15 @@ DRC-clean geometry, and blind/buried via spans.
 from __future__ import annotations
 
 import heapq
+import itertools
 import math
 import random
 
 from freeroute.board.board import BasicBoard
 from freeroute.board.items import ConductionArea, ObstacleArea, Pin, Via
-from freeroute.geometry import IntBox, IntPoint
-from freeroute.geometry.polyline import corner_box
+from freeroute.geometry import IntBox, IntPoint, Simplex
+from freeroute.geometry.octagon import overlaps_2d, segment_slab
+from freeroute.geometry.polyline import corner_box, segment_box
 
 __all__ = ["GridRouter", "RouteResult", "route_board"]
 
@@ -123,6 +125,8 @@ class _Connection:
         "path",
         "narrow",
         "half",
+        "stubs",
+        "stub_near",
     )
 
     def __init__(self, index: int, net_no: int, a: Pin, b: Pin) -> None:
@@ -138,6 +142,10 @@ class _Connection:
         self.via_cells: list[Cell] = []
         self.via_halo: list[Cell] = []
         self.halo_nodes: list[Node] = []
+        # each end's stub: its layer, its copper tiles, and the nodes it claims
+        self.stubs: list[tuple[int, list[IntBox], set[Node]]] = []
+        # every node its stubs come near, claimed or not (see GridRouter._stub_near)
+        self.stub_near: list[Node] = []
         # the pins and zones each end may use, and which pin the route ended
         # on (None when it ended on a zone)
         self.a_group: tuple[list[Pin], list] = ([a], [])
@@ -175,6 +183,7 @@ class GridRouter:
         seed: int | None = None,
         route_first: frozenset | None = None,
         access_cost: float = 0.0,
+        negotiate: int = 0,
         rollback: bool = True,
         net_widths: dict[int, int] | None = None,
         via_drill: int | None = None,
@@ -186,6 +195,15 @@ class GridRouter:
         # and the clearance around both) cost other nets this much extra, so
         # they route round a fine-pitch pin's way out instead of sealing it.
         self.access_cost = max(float(access_cost), 0.0)
+        # Negotiated congestion (PathFinder): before the real routing, every
+        # connection is routed this many times on the empty board, where routes
+        # may overlap at a price that grows where they compete. The cells that
+        # stay contested keep a history cost the real routing pays, so the first
+        # routes leave room around the places later routes have no way round.
+        self.negotiate = max(int(negotiate), 0)
+        self._history: dict[Node, float] = {}
+        self._present: dict[Node, dict[int, int]] | None = None
+        self._present_cost = 0.0
         self._doorways: dict[Node, list[tuple[int, int]]] = {}
         self._pending: dict[int, int] = {}
         # Rip-up as a transaction: the connections a rip-up route crosses are
@@ -203,6 +221,12 @@ class GridRouter:
         self._escape_cells = 12
         self._crowded_cache: dict = {}
         self._trapped_cache: dict = {}
+        # pin location -> where a pin on a turned fine-pitch pad leaves its
+        # pin row along the pad's axis (None: it leaves like any other pin)
+        self._axis_exits: dict[IntPoint, IntPoint | None] = {}
+        # and the other nets' pads near each such pin, its stubs' obstacles
+        self._axis_pads: dict[IntPoint, list] = {}
+        self._part_centres: dict[int, tuple[float, float] | None] = {}
         self.heuristic_weight = max(float(heuristic_weight), 1.0)
         self.trace_width = max(trace_width, 1)
         self.clearance = max(clearance, 0)
@@ -229,7 +253,7 @@ class GridRouter:
             (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
+            if (dx or dy) and max(abs(dx), abs(dy)) * self.step < need
         ]
         # A via's copper is wider than a trace. Another net's trace needs its
         # centre via_half + clearance + half_width from the via's centre, so a
@@ -294,7 +318,16 @@ class GridRouter:
         self._zone_cells: dict[int, list[Node]] = {}
         # per-connection occupancy (owner = connection index)
         self._cell_owner: dict[Node, int] = {}
-        self._via_owner: dict[Cell, int] = {}
+        # Node -> connections whose stub comes near it. A cell has one owner,
+        # and a stub claims only cells nobody owns yet, so where several pins
+        # leave side by side (a QFN turned 45 degrees: neighbours 0.35 mm apart
+        # on each axis) the cell two stubs share names only the first, and the
+        # exact check between the later stubs would never run.
+        self._stub_near: dict[Node, set[int]] = {}
+        # every connection whose via covers a cell, in claim order: a via two
+        # connections share still blocks after the first of them is ripped,
+        # and a route through it must rip all of them
+        self._via_claims: dict[Cell, list[int]] = {}
         # trace halos: node -> indices of the connections claiming it
         self._halo: dict[Node, list[int]] = {}
         self._rasterize_obstacles()
@@ -375,6 +408,19 @@ class GridRouter:
             shape.contains(IntPoint(c.x + dx, c.y + dy)) for dx in (-h, h) for dy in (-h, h)
         )
 
+    def _pad_cells(self, shape, box: IntBox, margin: int):
+        """Cells where a trace square ``margin`` wide around the centre overlaps
+        the pad: its box when it is one, else its exact (rotated) outline,
+        which is what the exact engine checks against."""
+        cells = self._cells_in_box(box, margin)
+        if not isinstance(shape, Simplex) or shape.is_int_box():
+            yield from cells
+            return
+        for cell in cells:
+            c = self._cell_center(cell)
+            if overlaps_2d(shape, IntBox(c.x - margin, c.y - margin, c.x + margin, c.y + margin)):
+                yield cell
+
     def _rasterize_obstacles(self) -> None:
         margin = self.clearance + self.half_width
         outline = self.board.outline
@@ -400,7 +446,7 @@ class GridRouter:
                     continue
                 net = item.net_nos[0] if item.net_nos else 0
                 pin_layers = [layer for layer in item.layers if layer in self.layers]
-                for cell in self._cells_in_box(box, margin):
+                for cell in self._pad_cells(item.shape, box, margin):
                     for layer in pin_layers:
                         self._pad_block.setdefault((*cell, layer), set()).add(net)
                 # Copper of the pin's own net: a trace inside it adds nothing,
@@ -499,14 +545,19 @@ class GridRouter:
         if owner is not None and conns[owner].net_no != net_no:
             blocking = owner
         else:
-            via_owner = self._via_owner.get(cell)
-            if via_owner is not None and conns[via_owner].net_no != net_no:
-                blocking = via_owner
+            blocking = self._via_blocker(cell, net_no, conns)
         if blocking is None:
             for i in self._halo.get(node, ()):
                 if conns[i].net_no != net_no:
                     blocking = i
                     break
+        if blocking is None:
+            # another net's pin stub comes too close, though the cell it once
+            # claimed may since have been freed by a rip of its first owner
+            for i in self._stub_near.get(node, ()):
+                if conns[i].net_no != net_no:
+                    blocking = i
+                    break
         if blocking is None:
             return 0.0
         if not allow_ripup:
@@ -516,6 +567,17 @@ class GridRouter:
             return None
         return self.rip_penalty * (1 + rip_count)
 
+    def _via_others(self, cell: Cell, net_no: int, conns: list[_Connection]) -> list[int]:
+        """Connections of other nets whose via covers ``cell``: all of them,
+        since two connections of a net can share one via."""
+        return [i for i in self._via_claims.get(cell, ()) if conns[i].net_no != net_no]
+
+    def _via_blocker(self, cell: Cell, net_no: int, conns: list[_Connection]) -> int | None:
+        """The other net's via connection on ``cell`` hardest to rip (the
+        penalty and the rip cap go by it), or None."""
+        others = self._via_others(cell, net_no, conns)
+        return max(others, key=lambda i: conns[i].rip_count) if others else None
+
     def _via_cells(self, cell: Cell) -> list[Cell]:
         """The cell a via sits in plus the neighbours its copper reaches."""
         r = self.via_reach
@@ -589,18 +651,19 @@ class GridRouter:
         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)."""
+        """Cells a trace of ``half`` also needs free: every cell out to its
+        extra half width, rounded up to whole cells. Blocks, halos and via
+        footprints are sized for a default-width trace, and copper is checked
+        as boxes, so anything within that square could be too close."""
         extra = half - self.half_width
         if extra <= 0:
             return []
-        reach = math.ceil(extra / self.step) + 1
-        limit = extra + self.step / 2
+        reach = math.ceil(extra / self.step)
         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
+            if dx or dy
         ]
 
     def _halo_for(self, half: int) -> list[tuple[int, int]]:
@@ -613,7 +676,7 @@ class GridRouter:
                 (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
+                if (dx or dy) and max(abs(dx), abs(dy)) * self.step < need
             ]
         return offsets
 
@@ -634,8 +697,8 @@ class GridRouter:
         if not conn.b_group[0] and any(z.layer in self._power_layers for z in conn.b_group[1]):
             # the plane is everywhere: aim at where the route starts instead
             goal_cell = self._group_target(conn.a_group)
-        starts = self._group_ends(conn.a_group, conn.net_no, conns)
-        goals = self._group_ends(conn.b_group, conn.net_no, conns)
+        starts = self._group_ends(conn.a_group, conn.net_no, conns, allow_ripup)
+        goals = self._group_ends(conn.b_group, conn.net_no, conns, allow_ripup)
         if not starts or not goals:
             return None
         # A start that is already an end joins at once, except that ending on
@@ -656,10 +719,19 @@ class GridRouter:
         came_from: dict[Node, Node] = {}
         # a stub costs its length, so the nearest cell wins unless it is blocked
         # 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)}
+        # (and in rip-up mode the rip penalty of whatever lies on it)
+        goal_stub = {
+            n: self._stub_cost(p, n) + self._end_penalty(p, n, net_no, allow_ripup, conns)
+            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 isinstance(pin, Pin) else 0.0
+            g_score[s] = (
+                self._stub_cost(pin, s) + self._end_penalty(pin, s, net_no, allow_ripup, conns)
+                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
@@ -727,6 +799,8 @@ class GridRouter:
                         continue
                     if self._doorways:
                         enter += self._access(nxt, net_no)
+                    if self._history or self._present is not None:
+                        enter += self._congestion(nxt, net_no)
                 step = 1.0 if dx == 0 or dy == 0 else math.sqrt(2)
                 self._relax(
                     current, nxt, base + step + enter, goal_cell, g_score, came_from, open_heap
@@ -739,9 +813,12 @@ class GridRouter:
                     if layer == cl:
                         continue
                     nxt = (cx, cy, layer)
-                    if g_via < g_score.get(nxt, math.inf):
+                    g_layer = g_via
+                    if self._history or self._present is not None:
+                        g_layer += self._congestion(nxt, net_no)
+                    if g_layer < g_score.get(nxt, math.inf):
                         heapq.heappush(
-                            open_heap, (g_via + self._h(nxt, goal_cell), nxt, g_via, current)
+                            open_heap, (g_layer + self._h(nxt, goal_cell), nxt, g_layer, current)
                         )
         return None
 
@@ -790,36 +867,176 @@ class GridRouter:
             math.hypot(loc.x - point.x, loc.y - point.y) < reach for loc, reach in self._tht_holes
         )
 
+    def _stub_points(self, pin_location: IntPoint, cell: Cell) -> list[IntPoint]:
+        """The stub's corners, from the pin to its cell centre.
+
+        The direct segment is fine for 45-degree routing. Orthogonal routing
+        leaves the pin straight along the axis it is further off the cell on
+        and jogs across to the centre at the end: an L of two flush boxes,
+        which is what the exact check sees. A single slanted segment is
+        checked as its bounding box there, and a 1 mm trace to a column
+        0.1 mm off a 1.27 mm pitch pin's centreline then lands inside the
+        clearance of the pad next door, though the straight exit clears it.
+        """
+        end = self._cell_center(cell)
+        head = [pin_location]
+        start = pin_location
+        exit_point = self._axis_exits.get(pin_location)
+        if exit_point is not None:
+            # a pin on a turned fine-pitch pad first leaves along the pad's
+            # axis, past the pin row, then takes the usual L to its cell
+            head = [pin_location, exit_point]
+            start = exit_point
+        dx, dy = end.x - start.x, end.y - start.y
+        if not self._orthogonal or dx == 0 or dy == 0:
+            tail = [end]
+        elif abs(dx) >= abs(dy):
+            tail = [IntPoint(end.x, start.y), end]
+        else:
+            tail = [IntPoint(start.x, end.y), end]
+        points = []
+        for point in head + tail:
+            if not points or points[-1] != point:
+                points.append(point)
+        return points if len(points) > 1 else [pin_location, end]
+
+    def _leg_shapes(self, points: list[IntPoint], half: int, grow: int = 0) -> list:
+        """A stub's copper, grown by ``grow``: a box per straight leg and per
+        inner corner, and an exact slab for a slanted leg (a pad-axis exit),
+        whose bounding box would reach the neighbouring pads."""
+        shapes: list = []
+        for a, b in zip(points, points[1:], strict=False):
+            if a == b:
+                continue
+            if a.x == b.x or a.y == b.y:
+                box = segment_box(a, b, half)
+                shapes.append(box.offset(grow) if grow else box)
+            else:
+                shapes.append(segment_slab(a, b, half + grow))
+        for c in points[1:-1]:
+            box = corner_box(c, half)
+            shapes.append(box.offset(grow) if grow else box)
+        return shapes
+
+    def _axis_exit(self, pin: Pin) -> IntPoint | None:
+        """Where a pin on a turned fine-pitch pad clears its pin row.
+
+        A QFN placed at 45 degrees has no straight exit on the grid: every
+        horizontal or vertical step from a pin passes its neighbours closer
+        than the clearance. The way out is along the pad's own axis, away
+        from the part, until an L from there to a grid cell clears every
+        other net's pad (checked on exact shapes, as the exact engine will).
+        Any angle off the grid axes counts, not just 45 degrees.
+        """
+        loc = pin.location
+        if loc in self._axis_exits:
+            return self._axis_exits[loc]
+        self._axis_exits[loc] = None
+        shape = pin.shape
+        if not isinstance(shape, Simplex) or shape.is_int_box():
+            return None
+        corners = [shape.corner_approx(i) for i in range(shape.border_line_count())]
+        edges = [(b.x - a.x, b.y - a.y) for a, b in zip(corners, corners[1:] + corners[:1], strict=False)]
+        lengths = [math.hypot(dx, dy) for dx, dy in edges]
+        if len(edges) < 3 or max(lengths) < 1.25 * min(lengths):
+            return None  # no long axis to leave along
+        dx, dy = edges[lengths.index(max(lengths))]
+        ux, uy = dx / max(lengths), dy / max(lengths)
+        if min(abs(ux), abs(uy)) < 0.17:
+            return None  # within ten degrees of a grid axis: the usual exits work
+        centre = self._part_centre(pin)
+        if centre is None:
+            return None
+        if (loc.x - centre[0]) * ux + (loc.y - centre[1]) * uy < 0:
+            ux, uy = -ux, -uy
+        reach = max((c.x - loc.x) * ux + (c.y - loc.y) * uy for c in corners)
+        h, cl = self.half_width, self.clearance
+        span = reach + h + cl + 16 * self.step
+        others = [
+            p.shape for p in self.board.get_pins()
+            if p.shape is not None and p is not pin and not set(p.net_nos) & set(pin.net_nos)
+            and set(p.layers) & set(pin.layers)
+            and abs(p.location.x - loc.x) < 2 * span and abs(p.location.y - loc.y) < 2 * span
+        ]
+        self._axis_pads[loc] = others
+        for j in range(16):
+            d = reach + h + cl + j * self.step / 2
+            exit_point = IntPoint(round(loc.x + ux * d), round(loc.y + uy * d))
+            out = segment_slab(loc, exit_point, h + cl)
+            if any(overlaps_2d(out, o) for o in others):
+                continue
+            ex, ey = self._cell_of(exit_point)
+            self._axis_exits[loc] = exit_point
+            for ddx, ddy in itertools.product((0, -1, 1), repeat=2):
+                cell = (ex + ddx, ey + ddy)
+                if not (0 <= cell[0] < self.cols and 0 <= cell[1] < self.rows):
+                    continue
+                legs = self._leg_shapes(self._stub_points(loc, cell)[1:], h, cl)
+                if not any(overlaps_2d(g, o) for g in legs for o in others):
+                    return exit_point
+            self._axis_exits[loc] = None
+        return None
+
+    def _exit_clips_a_pad(self, pin: Pin, cell: Cell) -> bool:
+        """Whether the stub from an axis exit to ``cell`` comes closer than the
+        clearance to another net's pad (exactly, as the exact engine checks):
+        the exit was chosen with one clear cell, not every cell around it."""
+        legs = self._leg_shapes(
+            self._stub_points(pin.location, cell)[1:], self._cur_half, self.clearance
+        )
+        return any(overlaps_2d(g, pad) for g in legs for pad in self._axis_pads.get(pin.location, ()))
+
+    def _part_centre(self, pin: Pin) -> tuple[float, float] | None:
+        key = pin.component_no
+        if key not in self._part_centres:
+            mates = [p.location for p in self.board.get_pins() if p.component_no == key] if key else []
+            self._part_centres[key] = (
+                (sum(m.x for m in mates) / len(mates), sum(m.y for m in mates) / len(mates))
+                if len(mates) > 2 else None
+            )
+        return self._part_centres[key]
+
     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)
+        points = self._stub_points(pin_location, cell)
         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),
+            min(p.x for p in points), min(p.y for p in points),
+            max(p.x for p in points), max(p.y for p in points),
         )
-        return [
-            c
-            for c in self._cells_in_box(box, reach)
-            if _point_segment(self._cell_center(c), pin_location, end) < reach
-        ]
+        legs = list(zip(points, points[1:], strict=False))
+        joints = points[1:]  # each carries a square corner tile
+
+        def near(c) -> bool:
+            p = self._cell_center(c)
+            if min(_point_segment(p, a, b) for a, b in legs) < reach:
+                return True
+            return any(max(abs(p.x - j.x), abs(p.y - j.y)) < reach for j in joints)
+
+        return [c for c in self._cells_in_box(box, reach) if near(c)]
 
     def _stub_clear(
-        self, pin: Pin, cell: Cell, layer: int, net_no: int, conns, keepouts_only: bool = False
+        self,
+        pin: Pin,
+        cell: Cell,
+        layer: int,
+        net_no: int,
+        conns,
+        keepouts_only: bool = False,
+        allow_ripup: bool = False,
     ) -> bool:
         keepouts = self._keepout_boxes.get(layer)
         if keepouts:
             # the stub is off the grid, so check it exactly, as the exact
             # engine will: its copper grown by clearance must miss every keepout
-            from freeroute.geometry.polyline import Polyline, PolylineShape
-
-            end = self._cell_center(cell)
-            if end != pin.location:
-                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):
+            points = self._stub_points(pin.location, cell)
+            if points[-1] != pin.location:
+                legs = self._leg_shapes(points, self._cur_half)
+                grown_legs = self._leg_shapes(points, self._cur_half, self.clearance)
+                for tile, grown in zip(legs, grown_legs, strict=True):
+                    if any(overlaps_2d(k, 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._cur_half)
@@ -827,14 +1044,69 @@ class GridRouter:
                     return False
         if keepouts_only:
             return True
-        for c in self._stub_cells(pin.location, cell):
-            owner = self._cell_owner.get((*c, layer))
-            if owner is not None and conns[owner].net_no != net_no:
-                return False
-            via_owner = self._via_owner.get(c)
-            if via_owner is not None and conns[via_owner].net_no != net_no:
-                return False
-        return True
+        owners = self._stub_owners(pin, cell, layer, net_no, conns)
+        # in rip-up mode a route on the stub is one more to rip, unless it may not be
+        return not owners or (
+            allow_ripup and all(conns[i].rip_count < self.rip_cap for i in owners)
+        )
+
+    def _stub_tiles(self, pin_location: IntPoint, cell: Cell, half: int, grow: int = 0) -> list:
+        """The stub's copper (grown by ``grow``): its legs, and a square at each
+        corner and at the cell end, where the route carries on."""
+        points = self._stub_points(pin_location, cell)
+        tiles: list = [
+            corner_box(point, half).offset(grow) if grow else corner_box(point, half)
+            for point in points[1:]
+        ]
+        if len(points) > 1 and points[-1] != pin_location:
+            tiles += self._leg_shapes(points, half, grow)
+        return tiles
+
+    def _stub_owners(
+        self, pin: Pin, cell: Cell, layer: int, net_no: int, conns, half: int | None = None
+    ) -> set[int]:
+        """Other nets' routes whose copper the stub from ``pin`` to ``cell`` would touch."""
+        owners: set[int] = set()
+        grown = None
+        for c in self._stub_cells(pin.location, cell, half):
+            node = (*c, layer)
+            owner = self._cell_owner.get(node)
+            if owner is not None and conns[owner].net_no != net_no and owner not in owners:
+                # Both stubs are off the grid, and each claims the cells a
+                # trace centred there would crowd, so two stubs side by side
+                # (neighbouring pins leaving straight) overlap in claims well
+                # before their copper comes near. Check those exactly.
+                other = [tiles for lay, tiles, nodes in conns[owner].stubs if node in nodes]
+                if other:
+                    if grown is None:
+                        grown = self._stub_tiles(
+                            pin.location, cell, half or self._cur_half, self.clearance
+                        )
+                    if not any(overlaps_2d(g, t) for tiles in other for t in tiles for g in grown):
+                        continue
+                owners.add(owner)
+            for idx in self._stub_near.get(node, ()):
+                if idx in owners or conns[idx].net_no == net_no:
+                    continue
+                theirs = [tiles for lay, tiles, _ in conns[idx].stubs if lay == layer]
+                if theirs:
+                    if grown is None:
+                        grown = self._stub_tiles(
+                            pin.location, cell, half or self._cur_half, self.clearance
+                        )
+                    if any(overlaps_2d(g, t) for tiles in theirs for t in tiles for g in grown):
+                        owners.add(idx)
+            owners.update(self._via_others(c, net_no, conns))
+        return owners
+
+    def _end_penalty(self, pin: Pin, node: Node, net_no: int, allow_ripup: bool, conns) -> float:
+        """Rip-up cost of starting or ending on ``node``: the routes on its
+        cell and on the stub to it, each at the penalty entering it would cost."""
+        if not allow_ripup:
+            return 0.0
+        owners = self._stub_owners(pin, node[:2], node[2], net_no, conns)
+        owners |= self._crossed_owners([node], net_no, conns)
+        return sum(self.rip_penalty * (1 + conns[i].rip_count) for i in owners)
 
     def _zone_nodes(self, zone) -> list[Node]:
         """Cells of a zone where a via of this net fits inside its copper; for a
@@ -882,11 +1154,13 @@ class GridRouter:
                 return zone.name or "zone"
         return ""
 
-    def _group_ends(self, group, net_no: int, conns) -> dict[Node, Pin | None]:
+    def _group_ends(
+        self, group, net_no: int, conns, allow_ripup: bool = False
+    ) -> dict[Node, Pin | None]:
         """End nodes of a group, each mapped to its pin (None for a zone cell)."""
         ends: dict[Node, Pin | None] = {}
         for pin in group[0]:
-            for node in sorted(self._end_nodes(pin, net_no, conns)):
+            for node in sorted(self._end_nodes(pin, net_no, conns, allow_ripup)):
                 ends.setdefault(node, pin)
         for zone in group[1]:
             plane = zone.layer in self._power_layers
@@ -902,34 +1176,54 @@ class GridRouter:
         return self._cell_of(IntPoint((box.ll.x + box.ur.x) // 2, (box.ll.y + box.ur.y) // 2))
 
     def _stub_cost(self, pin: Pin, node: Node) -> float:
-        c = self._cell_center(node[:2])
-        dx, dy = abs(c.x - pin.location.x), abs(c.y - pin.location.y)
-        if self._orthogonal:  # measured the way the route itself is allowed to move
-            return (dx + dy) / self.step
-        return math.hypot(dx, dy) / self.step
+        if self._axis_exits.get(pin.location) is None:
+            c = self._cell_center(node[:2])
+            dx, dy = abs(c.x - pin.location.x), abs(c.y - pin.location.y)
+            if self._orthogonal:  # measured the way the route itself is allowed to move
+                return (dx + dy) / self.step
+            return math.hypot(dx, dy) / self.step
+        points = self._stub_points(pin.location, node[:2])
+        return sum(
+            math.hypot(b.x - a.x, b.y - a.y) for a, b in zip(points, points[1:], strict=False)
+        ) / self.step
 
-    def _end_nodes(self, pin: Pin, net_no: int, conns) -> set[Node]:
+    def _end_nodes(self, pin: Pin, net_no: int, conns, allow_ripup: bool = False) -> set[Node]:
         """Nodes a route may start or end on for ``pin``: the nearest cell and
         its neighbours, where the cell is enterable and the stub to it is clear.
-        A crowded fine-pitch pin gets more than one way out."""
+        A crowded fine-pitch pin gets more than one way out. In rip-up mode a
+        cell or stub another route is on counts as enterable, as it does
+        everywhere else, or a pin whose only way out another net has taken
+        could never have it back."""
         layers = [layer for layer in pin.layers if layer in self.layers]
-        cx, cy = self._cell_of(pin.location)
+        exit_point = None
+        if self._orthogonal and self._crowded(pin, net_no):
+            exit_point = self._axis_exit(pin)
+        cx, cy = self._cell_of(exit_point if exit_point is not None else pin.location)
         nodes: set[Node] = set()
         for dx, dy in ((0, 0), *self._neighbours):
             cell = (cx + dx, cy + dy)
             if not (0 <= cell[0] < self.cols and 0 <= cell[1] < self.rows):
                 continue
+            if exit_point is not None and self._exit_clips_a_pad(pin, cell):
+                continue
             for layer in layers:
-                if (dx or dy) and self._enter_cost(cell, layer, net_no, False, conns) is None:
+                # the pin's own cell is in its pad; an exit cell is not
+                checked = dx or dy or exit_point is not None
+                if checked and self._enter_cost(cell, layer, net_no, allow_ripup, conns) is None:
                     continue
-                if self._stub_clear(pin, cell, layer, net_no, conns):
+                if self._stub_clear(pin, cell, layer, net_no, conns, allow_ripup=allow_ripup):
                     nodes.add((*cell, layer))
         # Also offer exact escape stubs: a fine-pitch pin's nearby cells can be
         # a pocket inside its own pad that leads nowhere (the grid columns miss
         # the narrow legal band past the pad tip). The stub's length is its
         # cost, so it is only taken where a short step would not do.
         if self._orthogonal and self._crowded(pin, net_no) and self._trapped(pin, net_no, nodes):
-            nodes |= self._escape_nodes(pin, net_no, conns, layers, (cx, cy))
+            nodes |= self._escape_nodes(pin, net_no, conns, layers, (cx, cy), allow_ripup)
+        if not nodes and exit_point is not None:
+            # every cell past the pin row is taken: report no way out, so the
+            # search goes on to rip-up, rather than fall back to a cell out in
+            # the open on top of another net's route
+            return nodes
         if not nodes:  # nothing clear: fall back to the nearest cell, as before
             nodes = {(cx, cy, layer) for layer in layers}
             if self._keepout_boxes and not any(
@@ -995,14 +1289,15 @@ class GridRouter:
         self._trapped_cache[key] = trapped
         return trapped
 
-    def _escape_nodes(self, pin: Pin, net_no: int, conns, layers, origin: Cell) -> set[Node]:
+    def _escape_nodes(
+        self, pin: Pin, net_no: int, conns, layers, origin: Cell, allow_ripup: bool = False
+    ) -> set[Node]:
         """For a pin walled in on the grid (a fine-pitch pin whose legal band
         the grid columns miss): look along each axis for the first open cell
-        whose straight stub from the pin clears every other net's pad by the
-        full margin, measured exactly rather than on the grid."""
-        from freeroute.board.outline import _segment_box
+        whose stub from the pin clears every other net's pad by the full
+        clearance, checked on the stub's copper tiles as the exact engine
+        will rather than on the grid."""
 
-        margin = self.half_width + self.clearance
         reach = self._escape_cells
         near = [
             (p.shape.bounding_box(), set(p.layers))
@@ -1014,24 +1309,30 @@ class GridRouter:
         ]
         cx, cy = origin
         nodes: set[Node] = set()
-        for dx, dy in _NEIGHBOURS[:4]:
+        # the pin's own column or row and the one either side: two pins side
+        # by side can then jog apart at the end of their straight exits
+        for (dx, dy), side in itertools.product(_NEIGHBOURS[:4], (0, -1, 1)):
+            sx, sy = (side, 0) if dx == 0 else (0, side)
+            nodes_before = len(nodes)
             for k in range(2, reach + 1):
-                cell = (cx + dx * k, cy + dy * k)
+                cell = (cx + dx * k + sx, cy + dy * k + sy)
                 if not (0 <= cell[0] < self.cols and 0 <= cell[1] < self.rows):
                     break
-                end = self._cell_center(cell)
+                grown = self._leg_shapes(
+                    self._stub_points(pin.location, cell), self._cur_half, self.clearance
+                )
                 for layer in layers:
-                    if self._enter_cost(cell, layer, net_no, False, conns) is None:
+                    if self._enter_cost(cell, layer, net_no, allow_ripup, conns) is None:
                         continue
                     if any(
-                        layer in box_layers and _segment_box(pin.location, end, box) < margin
+                        layer in box_layers and any(overlaps_2d(g, box) for g in grown)
                         for box, box_layers in near
                     ):
                         continue
-                    if self._stub_clear(pin, cell, layer, net_no, conns):
+                    if self._stub_clear(pin, cell, layer, net_no, conns, allow_ripup=allow_ripup):
                         nodes.add((*cell, layer))
-                if any(n[:2] == cell for n in nodes):
-                    break  # the first open cell along this axis is enough
+                if len(nodes) > nodes_before:
+                    break  # the first open cell along this line is enough
         return nodes
 
     def _relax(self, current, nxt, tentative, goal_cell, g_score, came_from, open_heap):
@@ -1081,19 +1382,27 @@ class GridRouter:
         conn.via_halo = []
         for cell in conn.via_cells:
             for c in self._via_cells(cell):
-                if c not in self._via_owner:
-                    self._via_owner[c] = conn.index
+                claims = self._via_claims.setdefault(c, [])
+                if conn.index not in claims:
+                    claims.append(conn.index)
                     conn.via_halo.append(c)
         ends = ((conn.a_end, wire_segs[0], 0), (conn.b_end, wire_segs[-1], -1)) if wire_segs else ()
+        conn.stubs = []
+        self._forget_stubs(conn)
         for pin, (layer, cells), at in ends:
             if not isinstance(pin, Pin):
                 continue  # ended on a zone or a plane: no stub
             cell = cells[at]
+            claimed: set[Node] = set()
             for c in self._stub_cells(pin.location, cell, half):
                 node = (*c, layer)
+                self._stub_near.setdefault(node, set()).add(conn.index)
+                conn.stub_near.append(node)
                 if node not in self._cell_owner:
                     self._cell_owner[node] = conn.index
                     conn.trace_cells.append((c, layer))
+                    claimed.add(node)
+            conn.stubs.append((layer, self._stub_tiles(pin.location, cell, half), claimed))
         # A pin inside a wire keepout can only leave by a via. Its stub to the
         # cell centre would be track inside the keepout, so the via goes on
         # the pin itself (a via in its own pad) and the stub is left out.
@@ -1111,9 +1420,9 @@ class GridRouter:
                 continue
             points = [self._cell_center(c) for c in cells]
             if idx == 0 and isinstance(conn.a_end, Pin):
-                points.insert(0, conn.a_end.location)
+                points[0:0] = self._stub_points(conn.a_end.location, cells[0])[:-1]
             if idx == len(wire_segs) - 1 and isinstance(conn.b_end, Pin):
-                points.append(conn.b_end.location)
+                points.extend(self._stub_points(conn.b_end.location, cells[-1])[-2::-1])
             points = _simplify(points)
             if len(points) >= 2:
                 conn.wires.append((layer, points))
@@ -1124,13 +1433,25 @@ class GridRouter:
         conn.routed = True
         self._settle(conn, -1)
 
+    def _forget_stubs(self, conn: _Connection) -> None:
+        for node in conn.stub_near:
+            near = self._stub_near.get(node)
+            if near is not None:
+                near.discard(conn.index)
+                if not near:
+                    del self._stub_near[node]
+        conn.stub_near = []
+
     def _rip(self, conn: _Connection) -> None:
         for cell, layer in conn.trace_cells:
             if self._cell_owner.get((*cell, layer)) == conn.index:
                 del self._cell_owner[(*cell, layer)]
         for cell in conn.via_halo:
-            if self._via_owner.get(cell) == conn.index:
-                del self._via_owner[cell]
+            claims = self._via_claims.get(cell)
+            if claims is not None and conn.index in claims:
+                claims.remove(conn.index)
+            if claims is not None and not claims:
+                del self._via_claims[cell]
         conn.via_halo = []
         for node in conn.halo_nodes:
             claims = self._halo.get(node)
@@ -1140,6 +1461,8 @@ class GridRouter:
                     del self._halo[node]
         conn.halo_nodes = []
         conn.trace_cells = []
+        conn.stubs = []
+        self._forget_stubs(conn)
         for cell in conn.via_cells:
             count = self._via_nets.get(cell)
             if count and count.get(conn.net_no):
@@ -1153,18 +1476,32 @@ class GridRouter:
         conn.rip_count += 1
         self._settle(conn, +1)
 
-    def _crossed_owners(self, path: list[Node], net_no: int, conns: list[_Connection]) -> set[int]:
+    def _crossed_owners(
+        self, path: list[Node], net_no: int, conns: list[_Connection], spread=None
+    ) -> set[int]:
+        """Connections whose copper or clearance ``path`` crosses; a trace
+        wider than the default crosses them on its ``spread`` cells too."""
+        spread = self._spread if spread is None else spread
+        if spread:
+            path = list(
+                dict.fromkeys(
+                    (x + dx, y + dy, layer)
+                    for x, y, layer in path
+                    for dx, dy in ((0, 0), *spread)
+                )
+            )
         owners: set[int] = set()
         for cx, cy, cl in path:
             owner = self._cell_owner.get((cx, cy, cl))
             if owner is not None and conns[owner].net_no != net_no:
                 owners.add(owner)
-            via_owner = self._via_owner.get((cx, cy))
-            if via_owner is not None and conns[via_owner].net_no != net_no:
-                owners.add(via_owner)
+            owners.update(self._via_others((cx, cy), net_no, conns))
             for i in self._halo.get((cx, cy, cl), ()):
                 if conns[i].net_no != net_no:
                     owners.add(i)
+            for i in self._stub_near.get((cx, cy, cl), ()):
+                if conns[i].net_no != net_no:
+                    owners.add(i)
         return owners
 
     # --- pin access ---------------------------------------------------------
@@ -1211,6 +1548,74 @@ class GridRouter:
                 return self.access_cost
         return 0.0
 
+    # --- negotiated congestion --------------------------------------------
+
+    def _congestion(self, node: Node, net_no: int) -> float:
+        """History of a contested cell, plus while negotiating the price of
+        sharing it with the other nets on it now."""
+        cost = self._history.get(node, 0.0)
+        if self._present is not None:
+            users = self._present.get(node)
+            if users:
+                others = len(users) - (1 if net_no in users else 0)
+                cost += self._present_cost * others
+        return cost
+
+    def _footprint(self, path: list[Node]) -> set[Node]:
+        """The nodes a route claims: its cells and their clearance halo on
+        its layer, and every via's footprint on all layers."""
+        wire_segs, via_cells = _split_path(path)
+        halo = [(0, 0), *self._halo_offsets]
+        nodes: set[Node] = set()
+        for layer, cells in wire_segs:
+            for cx, cy in cells:
+                for dx, dy in halo:
+                    nodes.add((cx + dx, cy + dy, layer))
+        for cell in via_cells:
+            for c in self._via_cells(cell):
+                for layer in self.layers:
+                    nodes.add((*c, layer))
+        return nodes
+
+    def _negotiate(self, order: list[_Connection], conns: list[_Connection]) -> None:
+        """Route every connection on the empty board ``self.negotiate`` times,
+        letting routes share cells at a price: the number of other nets on a
+        cell times a factor that doubles every round, plus the cell's history,
+        which grows by one for every extra net each round it stays shared.
+        Only the history is kept; the board is left empty."""
+        present: dict[Node, dict[int, int]] = {}
+        claimed: dict[int, set[Node]] = {}
+        ends = [(c, c.a_end, c.b_end) for c in conns]
+        self._present, self._present_cost = present, 0.5
+        try:
+            for _ in range(self.negotiate):
+                for conn in order:
+                    for node in claimed.pop(conn.index, ()):
+                        users = present[node]
+                        users[conn.net_no] -= 1
+                        if not users[conn.net_no]:
+                            del users[conn.net_no]
+                    path = self._search(conn, allow_ripup=False, conns=conns)
+                    if path is None:
+                        continue
+                    nodes = self._footprint(path)
+                    claimed[conn.index] = nodes
+                    for node in nodes:
+                        users = present.setdefault(node, {})
+                        users[conn.net_no] = users.get(conn.net_no, 0) + 1
+                shared = 0
+                for node, users in present.items():
+                    if len(users) > 1:
+                        shared += 1
+                        self._history[node] = self._history.get(node, 0.0) + len(users) - 1
+                if not shared:
+                    break
+                self._present_cost *= 2
+        finally:
+            self._present = None
+            for conn, a_end, b_end in ends:  # the search picks ends; undo that
+                conn.a_end, conn.b_end = a_end, b_end
+
     # --- passes -------------------------------------------------------------
 
     def route(self) -> RouteResult:
@@ -1234,6 +1639,8 @@ class GridRouter:
         if self.route_first:
             # stable: the promoted keep their order among themselves, as do the rest
             order.sort(key=lambda c: (c.net_no, *_ends_of(c)) not in self.route_first)
+        if self.negotiate:
+            self._negotiate(order, conns)
         for _ in range(passes):
             changed = False
             for conn in order:
@@ -1272,7 +1679,16 @@ class GridRouter:
             path = self._search(conn, allow_ripup=True, conns=conns)
             if path is None:
                 return False
-            victims = [conns[i] for i in sorted(self._crossed_owners(path, conn.net_no, conns))]
+            crossed = self._crossed_owners(
+                path, conn.net_no, conns, self._spread_for(self._conn_half(conn))
+            )
+            # and the routes on the stubs from the pins to the path's ends
+            for end, node in ((conn.a_end, path[0]), (conn.b_end, path[-1])):
+                if isinstance(end, Pin):
+                    crossed |= self._stub_owners(
+                        end, node[:2], node[2], conn.net_no, conns, self._conn_half(conn)
+                    )
+            victims = [conns[i] for i in sorted(crossed)]
             if self.rollback:
                 return self._ripup_transaction(conn, path, victims, conns)
             for victim in victims:
@@ -1621,6 +2037,7 @@ def route_board(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
+    negotiate: int = 0,
     rollback: bool = True,
     net_widths: dict[int, int] | None = None,
     via_drill: int | None = None,
@@ -1643,6 +2060,7 @@ def route_board(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
+        negotiate=negotiate,
         rollback=rollback,
         net_widths=net_widths,
         via_drill=via_drill,

src/freeroute/route/pipeline.py

@@ -118,6 +118,7 @@ def route_dsn_board(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
+    negotiate: int = 0,
     hole_to_hole_mm: float = 0.25,
     rollback: bool = True,
 ) -> tuple[RouteResult, int, list[str]]:
@@ -143,6 +144,7 @@ def route_dsn_board(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
+        negotiate=negotiate,
         rollback=rollback,
         net_widths=_net_widths_board(dsn, scale),
         via_drill=_via_drill_board(dsn, scale),
@@ -196,6 +198,7 @@ def build_routing_result(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
+    negotiate: int = 0,
     hole_to_hole_mm: float = 0.25,
     rollback: bool = True,
 ) -> RoutingResult:
@@ -205,6 +208,7 @@ def build_routing_result(
         edge_clearance_mm=edge_clearance_mm, resolution=resolution, seed=seed,
         route_first=route_first,
         access_cost=access_cost,
+        negotiate=negotiate,
         hole_to_hole_mm=hole_to_hole_mm,
         rollback=rollback,
     )
@@ -225,6 +229,7 @@ def route_dsn_board_exact(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
+    negotiate: int = 0,
     hole_to_hole_mm: float = 0.25,
     rollback: bool = True,
 ) -> tuple[ExactRouteResult, int, list[str]]:
@@ -254,6 +259,7 @@ def route_dsn_board_exact(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
+        negotiate=negotiate,
         rollback=rollback,
         net_widths=_net_widths_board(dsn, scale),
         via_drill=_via_drill_board(dsn, scale),
@@ -276,6 +282,7 @@ def build_exact_routing_result(
     seed: int | None = None,
     route_first: frozenset | None = None,
     access_cost: float = 0.0,
+    negotiate: int = 0,
     hole_to_hole_mm: float = 0.25,
     rollback: bool = True,
 ) -> RoutingResult:
@@ -293,6 +300,7 @@ def build_exact_routing_result(
         seed=seed,
         route_first=route_first,
         access_cost=access_cost,
+        negotiate=negotiate,
         hole_to_hole_mm=hole_to_hole_mm,
         rollback=rollback,
     )

tests/route/test_axis_escapes.py

@@ -0,0 +1,113 @@
+"""Pins of a fine-pitch part turned off the grid axes leave along their pads.
+
+A QFN at 45 degrees has no straight exit: every horizontal or vertical step
+from a pin passes its neighbours closer than the clearance (0.35 mm away on
+each axis at 0.5 mm pitch). The grid leaves along the pad's own axis first,
+past the pin row, and the exact engine checks that slanted leg on its exact
+copper. Found on th-eda's lift ESC, where a QFN-24 at 45 degrees left 15
+connections unroutable on an empty board.
+"""
+
+from __future__ import annotations
+
+import math
+
+import pytest
+
+from freeroute.board import build_board
+from freeroute.dsn import parse_dsn
+from freeroute.geometry import IntPoint, overlaps_2d, segment_slab
+from freeroute.route.grid_router import GridRouter
+from freeroute.route.pipeline import (
+    _rule_clearance_dsn,
+    _rule_width_dsn,
+    _via_half_board,
+    build_exact_routing_result,
+)
+
+
+def _qfn_side_dsn(rotation: float) -> str:
+    """Two rows of five 0.25 x 0.8 mm pads at 0.5 mm pitch (one side of a
+    QFN and its opposite side), turned by ``rotation``; each pin of the top
+    row is its own net, routed to a pad 4.5 mm out, the pads fanned 1.5 mm
+    apart."""
+    cx, cy = 100000, -100000
+    t = math.radians(rotation)
+    out = (-math.sin(t), math.cos(t))  # the pads' outward axis after turning
+    along = (math.cos(t), math.sin(t))  # the pin row
+    pins, targets, nets = [], [], []
+    for i in range(5):
+        x = -1000 + 500 * i
+        pins += [f"(pin P {i + 1} {x} 1000)", f"(pin P {i + 6} {x} -1000)"]
+        px = cx + x * math.cos(t) - 1000 * math.sin(t)
+        py = cy + x * math.sin(t) + 1000 * math.cos(t)
+        spread = 1500 * (i - 2) - x  # fan the far pads out to 1.5 mm apart
+        tx = px + 4500 * out[0] + spread * along[0]
+        ty = py + 4500 * out[1] + spread * along[1]
+        targets.append(f"(place T{i + 1} {round(tx)} {round(ty)} front 0)")
+        nets.append(f"(net N{i} (pins U1-{i + 1} T{i + 1}-1))")
+    return f"""(pcb qfn (parser) (resolution um 10) (unit um)
+  (structure
+    (layer F.Cu (type signal)) (layer B.Cu (type signal))
+    (boundary (path pcb 0  115000 -115000  85000 -115000  85000 -85000  115000 -85000
+      115000 -115000))
+    (via "Via[0-1]_450:200_um")
+    (rule (width 150) (clearance 150)))
+  (placement
+    (component Q (place U1 {cx} {cy} front {rotation}))
+    (component T {" ".join(targets)}))
+  (library
+    (image Q {" ".join(pins)})
+    (image T (pin t 1 0 0))
+    (padstack P (shape (rect F.Cu -125 -400 125 400)) (attach off))
+    (padstack t (shape (rect F.Cu -300 -300 300 300)) (attach off))
+    (padstack "Via[0-1]_450:200_um" (shape (circle F.Cu 450)) (shape (circle B.Cu 450))
+      (attach off)))
+  (network {" ".join(nets)}))"""
+
+
+@pytest.mark.parametrize("rotation", [45, 30, -45])
+def test_a_turned_fine_pitch_part_gets_its_pins_out(rotation):
+    result = build_exact_routing_result(parse_dsn(_qfn_side_dsn(rotation)), resolution=2, shove=True)
+    assert result.unrouted == []
+
+
+def test_the_exit_runs_along_the_pad_axis_and_clears_the_neighbours():
+    dsn = parse_dsn(_qfn_side_dsn(45))
+    s = dsn.resolution.value
+    board = build_board(dsn)
+    router = GridRouter(
+        board,
+        trace_width=round(_rule_width_dsn(dsn) * s),
+        clearance=round(_rule_clearance_dsn(dsn) * s),
+        via_half=_via_half_board(dsn, s),
+        orthogonal=True,
+    )
+    pins = {p.name: p for p in board.get_pins() if p.component_ref == "U1"}
+    pin = pins["3"]
+    exit_point = router._axis_exit(pin)
+    assert exit_point is not None
+    dx, dy = exit_point.x - pin.location.x, exit_point.y - pin.location.y
+    assert abs(abs(dx) - abs(dy)) <= 2  # along the 45-degree axis
+    leg = segment_slab(pin.location, exit_point, router.half_width + router.clearance)
+    for name in ("2", "4"):
+        assert not overlaps_2d(leg, pins[name].shape)
+
+
+def test_a_pad_on_the_grid_axes_keeps_the_usual_exits():
+    dsn = parse_dsn(_qfn_side_dsn(0))
+    s = dsn.resolution.value
+    board = build_board(dsn)
+    router = GridRouter(board, trace_width=round(_rule_width_dsn(dsn) * s),
+                        clearance=round(_rule_clearance_dsn(dsn) * s), via_half=_via_half_board(dsn, s))
+    pin = next(p for p in board.get_pins() if p.component_ref == "U1" and p.name == "3")
+    assert router._axis_exit(pin) is None
+
+
+def test_a_slanted_slab_is_tight_where_a_bounding_box_is_not():
+    slab = segment_slab(IntPoint(0, 0), IntPoint(10000, 10000), 750)
+    # a point beside the diagonal but inside its bounding box
+    from freeroute.geometry import IntBox
+
+    assert not overlaps_2d(slab, IntBox(8000, 0, 8100, 100))
+    assert overlaps_2d(slab, IntBox(4900, 4900, 5100, 5100))

tests/route/test_grid_exact_agreement.py

@@ -0,0 +1,284 @@
+"""The grid must not believe copper legal that the exact check then refuses.
+
+Each case is one way the two used to disagree on roomba-ESP12E: a rotated oval
+pad modelled as an inflated box (and opened to its own net), a via shared by
+two connections of a net losing its footprint when one of them is ripped, and
+a wider net class searched as if it were the default width.
+"""
+
+from __future__ import annotations
+
+import math
+
+import pytest
+
+from freeroute.board import build_board
+from freeroute.dsn import parse_dsn
+from freeroute.geometry import IntBox, Simplex
+from freeroute.route.grid_router import GridRouter
+from freeroute.route.pipeline import (
+    _rule_clearance_dsn,
+    _rule_width_dsn,
+    _via_half_board,
+    build_exact_routing_result,
+)
+
+# --- rotated oval pads -------------------------------------------------------
+
+
+def _socket_dsn(rotation: float, layout: str) -> str:
+    """A 1x4 2.54 mm socket strip (rect pin 1, oval pins 2-4) at ``rotation``,
+    each pin its own net, routed to a small SMD pad 0.9 mm away."""
+    cx, cy = 100000, -100000
+    t = math.radians(rotation)
+    ax = (math.cos(t), math.sin(t))
+    perp = (-math.sin(t), math.cos(t))
+    places = []
+    for i in range(4):
+        px, py = cx + 2540 * i * ax[0], cy + 2540 * i * ax[1]
+        side = 1 if i % 2 == 0 else -1
+        if layout == "y":
+            tx, ty = px, py + side * 9000
+        else:
+            tx, ty = px + side * 8000 * perp[0], py + side * 8000 * perp[1]
+        places.append(f"(place T{i + 1} {round(tx)} {round(ty)} front 0)")
+    nets = " ".join(f"(net N{i} (pins P3-{i + 1} T{i + 1}-1))" for i in range(4))
+    return f"""(pcb socket (parser) (resolution um 10) (unit um)
+  (structure
+    (layer F.Cu (type signal)) (layer B.Cu (type signal))
+    (boundary (path pcb 0  125000 -115000  85000 -115000  85000 -75000  125000 -75000
+      125000 -115000))
+    (via "Via[0-1]_800:400_um")
+    (rule (width 300) (clearance 250)))
+  (placement
+    (component S (place P3 {cx} {cy} front {rotation}))
+    (component T {" ".join(places)}))
+  (library
+    (image S (pin R 1 0 0) (pin O 2 2540 0) (pin O 3 5080 0) (pin O 4 7620 0))
+    (image T (pin t 1 0 0))
+    (padstack O (shape (path F.Cu 1727.2 0 -152.4 0 152.4))
+      (shape (path B.Cu 1727.2 0 -152.4 0 152.4)) (attach off))
+    (padstack R (shape (rect F.Cu -863.6 -1016 863.6 1016))
+      (shape (rect B.Cu -863.6 -1016 863.6 1016)) (attach off))
+    (padstack t (shape (rect F.Cu -500 -500 500 500)) (attach off))
+    (padstack "Via[0-1]_800:400_um" (shape (circle F.Cu 800)) (shape (circle B.Cu 800))
+      (attach off)))
+  (network {nets}
+    (class c N0 N1 N2 N3 (circuit (use_via "Via[0-1]_800:400_um"))
+      (rule (width 300) (clearance 250)))))"""
+
+
+def test_a_rotated_oval_pad_is_its_outline_not_its_bounding_box():
+    board = build_board(parse_dsn(_socket_dsn(60, "y")))
+    oval = next(p for p in board.get_pins() if p.component_ref == "P3" and p.name == "2")
+    assert isinstance(oval.shape, Simplex) and not oval.shape.is_int_box()
+    box = oval.shape.bounding_box()
+    assert oval.shape.contains(oval.location)
+    assert not oval.shape.contains(box.ll) and not oval.shape.contains(box.ur)
+
+
+@pytest.mark.parametrize("layout", ["y", "perp"])
+def test_routes_leaving_a_rotated_socket_pass_the_exact_check(layout):
+    result = build_exact_routing_result(
+        parse_dsn(_socket_dsn(60, layout)), resolution=2, shove=True
+    )
+    assert result.unrouted == []
+
+
+# --- a via two connections share --------------------------------------------
+
+_SHARED_VIA = """(pcb shared (parser) (resolution um 10) (unit um)
+  (structure
+    (layer Top (type signal)) (layer Bottom (type signal))
+    (boundary (path pcb 0  0 0  20000 0  20000 -20000  0 -20000  0 0))
+    (via "Via[0-1]_800:400_um")
+    (rule (width 300) (clearance 250)))
+  (library
+    (padstack p (shape (rect Top -400 -400 400 400)) (attach off))
+    (padstack "Via[0-1]_800:400_um" (shape (circle Top 800)) (shape (circle Bottom 800))
+      (attach off))
+    (image PAD (pin p 1 0 0)))
+  (placement (component PAD
+    (place G1 3000 -5000 front 0) (place G2 3000 -15000 front 0)
+    (place G3 17000 -10000 front 0) (place S1 3000 -10000 front 0)
+    (place S2 17000 -3000 front 0)))
+  (network (net GND (pins G1-1 G2-1 G3-1)) (net SIG (pins S1-1 S2-1))))"""
+
+
+def _line(a, b, layer):
+    (x, y), (x1, y1) = a, b
+    out = [(x, y, layer)]
+    while x != x1:
+        x += 1 if x1 > x else -1
+        out.append((x, y, layer))
+    while y != y1:
+        y += 1 if y1 > y else -1
+        out.append((x, y, layer))
+    return out
+
+
+def test_a_shared_via_keeps_its_footprint_when_one_user_is_ripped():
+    dsn = parse_dsn(_SHARED_VIA)
+    s = dsn.resolution.value
+    router = GridRouter(
+        build_board(dsn),
+        trace_width=round(_rule_width_dsn(dsn) * s),
+        clearance=round(_rule_clearance_dsn(dsn) * s),
+        via_half=_via_half_board(dsn, s),
+    )
+    conns = router._conns = router._build_connections()
+    gnd = [c for c in conns if len({c.a.component_ref, c.b.component_ref} & {"G1", "G2", "G3"})]
+    sig = next(c for c in conns if c not in gnd)
+    first, second = gnd
+    g3 = router._cell_of(next(p for p in router.board.get_pins() if p.component_ref == "G3").location)
+    via = (g3[0] - 10, g3[1])
+
+    def through_via(conn):
+        a, b = router._cell_of(conn.a.location), router._cell_of(conn.b.location)
+        return _line(a, via, 0) + _line(via, b, 1)
+
+    router._commit(first, through_via(first))
+    router._commit(second, through_via(second))
+    footprint = [c for c in router._via_cells(via) if c != via]
+    router._rip(first)
+
+    assert second.routed and via in second.via_cells
+    assert all(router._via_claims.get(c) == [second.index] for c in footprint)
+    # another net still keeps its distance from the via that is left
+    assert all(router._enter_cost_base(c, 0, sig.net_no, False, conns) is None for c in footprint)
+
+
+def test_a_route_through_a_shared_via_rips_every_user():
+    """Two connections of a net share a via. Another net routed through it
+    in rip-up mode has to rip both, or the one left keeps its via under the
+    new trace and the exact check throws one of them out."""
+    dsn = parse_dsn(_SHARED_VIA)
+    s = dsn.resolution.value
+    router = GridRouter(
+        build_board(dsn),
+        trace_width=round(_rule_width_dsn(dsn) * s),
+        clearance=round(_rule_clearance_dsn(dsn) * s),
+        via_half=_via_half_board(dsn, s),
+    )
+    conns = router._conns = router._build_connections()
+    gnd = [c for c in conns if len({c.a.component_ref, c.b.component_ref} & {"G1", "G2", "G3"})]
+    sig = next(c for c in conns if c not in gnd)
+    first, second = gnd
+    g3 = router._cell_of(next(p for p in router.board.get_pins() if p.component_ref == "G3").location)
+    via = (g3[0] - 10, g3[1])
+
+    def through_via(conn):
+        a, b = router._cell_of(conn.a.location), router._cell_of(conn.b.location)
+        return _line(a, via, 0) + _line(via, b, 1)
+
+    router._commit(first, through_via(first))
+    router._commit(second, through_via(second))
+    # the via's copper alone: footprint cells no trace or trace halo covers
+    crossing = [
+        node
+        for c in router._via_cells(via)
+        for node in ((*c, 0), (*c, 1))
+        if node not in router._cell_owner and node not in router._halo
+    ]
+    assert crossing
+
+    assert router._crossed_owners(crossing, sig.net_no, conns) == {first.index, second.index}
+
+
+# --- a wider net class --------------------------------------------------------
+
+_WIDE = """(pcb wide (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))
+    (rule (width 300) (clearance 250)))
+  (placement (component S (place P1 2000 -5000 front 0) (place P2 18000 -5000 front 0)
+     (place Q1 10000 {ylo} front 0) (place Q2 10000 {yhi} front 0)
+     (place Q3 10000 -1000 front 0) (place Q4 10000 -9000 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)) (net SIG (pins Q1-1 Q3-1)) (net SIG2 (pins Q2-1 Q4-1))
+    (class Power PWR (rule (width 500) (clearance 250)))))"""
+
+
+@pytest.mark.parametrize("resolution", [1, 2])
+@pytest.mark.parametrize("gap", [900, 1000, 1075])
+def test_a_wide_net_past_pads_it_does_not_fit_between_is_not_refused(gap, resolution):
+    # 0.3 mm fits the gap between the two pads, 0.5 mm does not: the grid
+    # must see that, rather than lay it wide and have the exact check drop it
+    ylo, yhi = -5000 - gap // 2 - 600, -5000 + gap // 2 + 600
+    result = build_exact_routing_result(
+        parse_dsn(_WIDE.format(ylo=ylo, yhi=yhi)), resolution=resolution
+    )
+    assert result.unrouted == []
+
+
+def _wide_router():
+    dsn = parse_dsn(_WIDE.format(ylo=-6050, yhi=-3950))
+    s = dsn.resolution.value
+    pwr = next(i for i, net in enumerate(dsn.nets, 1) if net.name == "PWR")
+    return GridRouter(
+        build_board(dsn),
+        trace_width=round(_rule_width_dsn(dsn) * s),
+        clearance=round(_rule_clearance_dsn(dsn) * s),
+        resolution=2,
+        net_widths={pwr: 5000},
+    ), pwr
+
+
+def test_a_wide_trace_keeps_clear_of_a_default_one_at_the_grid_diagonal():
+    router, _pwr = _wide_router()
+    # 0.5 mm against 0.3 mm needs 0.25 + 0.25 + 0.15 = 0.65 mm between centres,
+    # on either axis, since the exact check compares boxes
+    need = 2500 + router.clearance + router.half_width
+    for dx, dy in [(2, 2), (2, 1), (1, 2)]:
+        assert max(dx, dy) * router.step < need
+        assert (dx, dy) in router._halo_for(2500)
+
+
+def test_a_wide_rip_up_route_counts_what_its_extra_width_crosses():
+    router, pwr_net = _wide_router()
+    conns = router._conns = router._build_connections()
+    pwr = next(c for c in conns if c.net_no == pwr_net)
+    other = next(c for c in conns if c.net_no != pwr_net)
+    # a default-width trace two cells from the wide route's path
+    x, y = 20, 5
+    router._commit(other, _line((x - 3, y + 2), (x + 3, y + 2), 0))
+    path = _line((x - 3, y), (x + 3, y), 0)
+    spread = router._spread_for(2500)
+    assert other.index not in router._crossed_owners(path, pwr.net_no, conns)
+    assert other.index in router._crossed_owners(path, pwr.net_no, conns, spread)
+
+
+def test_a_pad_cell_check_uses_the_rotated_outline():
+    board = build_board(parse_dsn(_socket_dsn(60, "y")))
+    router = GridRouter(board, trace_width=3000, clearance=2500, resolution=2)
+    oval = next(p for p in board.get_pins() if p.component_ref == "P3" and p.name == "2")
+    box = oval.shape.bounding_box()
+    margin = router.clearance + router.half_width
+    exact = set(router._pad_cells(oval.shape, box, margin))
+    boxed = set(router._cells_in_box(box, margin))
+    assert exact < boxed
+    for cell in boxed - exact:
+        c = router._cell_center(cell)
+        square = IntBox(c.x - margin, c.y - margin, c.x + margin, c.y + margin)
+        assert oval.shape.intersection(square).dimension() != 2
+
+
+def test_a_via_by_a_chamfered_corner_is_judged_round():
+    """The grid keeps a via's centre its radius plus the edge clearance from
+    the outline. The exact check used the via's square, whose corner reaches
+    past a 45-degree chamfer where the round via does not."""
+    from freeroute.board.outline import BoardOutline
+    from freeroute.geometry import IntBox, IntPoint
+    from freeroute.route.exact_router import _inside_outline
+
+    # a 10 mm square with its lower-left corner cut at 45 degrees
+    outline = BoardOutline([IntPoint(*p) for p in
+                            [(30, 0), (100, 0), (100, 100), (0, 100), (0, 30)]])
+    half, edge = 4, 1
+    via = IntPoint(19, 20)  # its centre 6.4 from the chamfer x + y = 30
+    square = IntBox(via.x - half, via.y - half, via.x + half, via.y + half)
+    assert not outline.box_clear(square, edge)  # the square's corner: 0.7 away
+    assert _inside_outline(outline, [], [via], half + edge, edge)
+    # 4.2 from the chamfer: the round via itself is too close
+    assert not _inside_outline(outline, [], [IntPoint(18, 18)], half + edge, edge)

tests/route/test_negotiate.py

@@ -0,0 +1,65 @@
+"""--negotiate: PathFinder-style rounds on the empty board before routing."""
+
+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 _router(name, negotiate):
+    dsn = parse_dsn((FIXTURES / name).read_text())
+    s = dsn.resolution.value
+    return GridRouter(
+        build_board(dsn),
+        trace_width=round(_rule_width_dsn(dsn) * s),
+        clearance=round(_rule_clearance_dsn(dsn) * s),
+        negotiate=negotiate,
+    )
+
+
+def test_negotiation_leaves_the_board_empty_and_the_ends_as_they_were():
+    router = _router("true_density.dsn", 3)
+    conns = router._conns = router._build_connections()
+    ends = [(c.a_end, c.b_end) for c in conns]
+    router._negotiate(list(conns), conns)
+    assert router._history  # a dense board has contested cells
+    assert not router._cell_owner and not router._halo and not router._via_claims
+    assert not any(c.routed for c in conns)
+    assert [(c.a_end, c.b_end) for c in conns] == ends
+    assert router._present is None
+
+
+def test_sharing_is_priced_only_for_other_nets():
+    router = _router("true_density.dsn", 1)
+    node = (3, 4, 0)
+    router._history[node] = 2.0
+    router._present, router._present_cost = {node: {7: 1, 9: 2}}, 0.5
+    assert router._congestion(node, 7) == pytest.approx(2.5)  # one other net
+    assert router._congestion(node, 5) == pytest.approx(3.0)  # two other nets
+    router._present = None
+    assert router._congestion(node, 5) == pytest.approx(2.0)  # history only, after
+
+
+@pytest.mark.parametrize("name", ["ripup_needed.dsn", "true_density.dsn", "kicad_routable.dsn"])
+def test_negotiated_routing_keeps_the_occupancy_honest(name):
+    """Only routed connections hold cells afterwards, as without negotiation."""
+    router = _router(name, 3)
+    router.route()
+    conns = router._conns
+    assert all(conns[i].routed for i in router._cell_owner.values())
+    assert all(conns[i].routed for claims in router._halo.values() for i in claims)
+
+
+def test_option_reaches_the_router_and_is_off_by_default():
+    text = (FIXTURES / "kicad_routable.dsn").read_text()
+    plain, _, _ = route_dsn_board(parse_dsn(text))
+    again, _, _ = route_dsn_board(parse_dsn(text), negotiate=0)
+    assert plain.unrouted == again.unrouted

tests/route/test_real_board_geometry.py

@@ -51,19 +51,22 @@ def test_routes_keep_edge_clearance_at_a_rounded_corner():
                 assert outline.edge_distance(p) >= half + 500 * scale - 1
 
 
-@pytest.mark.parametrize(("resolution", "escape"), [(1, 2), (4, 5)])
-def test_every_pin_of_a_half_millimetre_pitch_row_escapes(resolution, escape):
+@pytest.mark.parametrize("resolution", [1, 4])
+def test_every_pin_of_a_half_millimetre_pitch_row_escapes(resolution):
     # Five 0.3 mm pads at 0.5 mm pitch, each wired to its own pad 8 mm away.
     # Between two neighbours a trace's centre has a legal band only 0.15 mm
-    # wide. At resolution 1 the 0.4 mm grid misses most bands; at 4 its
-    # 0.1 mm columns cannot, and every pin gets out, as the JAR manages.
+    # wide. At resolution 4 the 0.1 mm columns cannot miss it. At resolution
+    # 1 the 0.4 mm grid misses most bands, but a stub leaves its pin straight
+    # along the band and jogs to the column only past the pads, so every pin
+    # gets out there too, as the JAR manages (only 2 did before).
     places = " ".join(f"(place R{i} {6000 + 500 * i} -6000 front 0)" for i in range(5))
     places += " " + " ".join(f"(place F{i} {6000 + 500 * i} -14000 front 0)" for i in range(5))
     nets = " ".join(f"(net N{i} (pins R{i}-1 F{i}-1))" for i in range(5))
     result, _, _ = route_dsn_board_exact(
         parse_dsn(_dsn(f"(component P {places})", nets)), resolution=resolution
     )
-    assert len(result.routed_net_numbers) == escape
+    assert len(result.routed_net_numbers) == 5
+    assert result.drc_clean
 
 
 def test_resolution_one_has_no_halo_so_the_grid_is_unchanged():

tests/route/test_rollback.py

@@ -31,7 +31,7 @@ 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._via_claims.values() for i in claims)
     assert all(conns[i].routed for claims in router._halo.values() for i in claims)
 
 

tests/route/test_straight_pin_exits.py

@@ -0,0 +1,58 @@
+"""Pins of a 1.27 mm pitch row routed at 1.0 mm (the RN2483 module on the
+TTN Enschede mote). A trace centre has to stay within 0.06 mm of a pin's
+centreline to pass its neighbours, which no grid column hits, so a route
+leaves each pin straight along that line and only jogs to its column once
+past the pads. FreeRouting routes this row in full the same way."""
+
+from __future__ import annotations
+
+import pytest
+
+from freeroute.board import build_board
+from freeroute.board.items import Pin
+from freeroute.dsn import parse_dsn
+from freeroute.geometry import IntPoint
+from freeroute.route.grid_router import GridRouter
+from freeroute.route.pipeline import route_dsn_board_exact
+
+
+def _row(x0: int, pins: int = 6, skew: int = 3000) -> str:
+    places = " ".join(f"(place R{i} {x0 + 1270 * i} -5000 front 0)" for i in range(pins))
+    places += " " + " ".join(
+        f"(place T{i} {x0 + 1270 * i + skew} -15000 front 0)" for i in range(pins)
+    )
+    nets = " ".join(f"(net N{i} (pins R{i}-1 T{i}-1))" for i in range(pins))
+    return f"""(pcb t (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]_600:400_um") (rule (width 1000) (clearance 200)))
+  (placement (component P {places}))
+  (library (image P (pin pad 1 0 0))
+    (padstack pad (shape (rect F.Cu -508 -762 508 762)) (attach off))
+    (padstack "Via[0-1]_600:400_um" (shape (circle F.Cu 600)) (shape (circle B.Cu 600))
+      (attach off)))
+  (network {nets}))"""
+
+
+@pytest.mark.parametrize("x0", [5000, 5150, 5300])
+def test_every_pin_of_a_row_leaves_straight_and_routes(x0):
+    # three offsets of the row against the grid; before, 2 or 3 of 6 routed
+    result, _, _ = route_dsn_board_exact(parse_dsn(_row(x0)), resolution=2)
+    assert len(result.routed_net_numbers) == 6
+    assert result.drc_clean
+
+
+def test_a_walled_in_pin_may_escape_to_the_column_either_side():
+    # two pins side by side leaving the same way can then jog apart
+    board = build_board(parse_dsn(_row(5000)))
+    router = GridRouter(board, trace_width=10000, clearance=2000, orthogonal=True, resolution=2)
+    router._conns = router._build_connections()
+    pin = next(
+        p for p in board.get_items()
+        if isinstance(p, Pin) and p.location == IntPoint(50000 + 2 * 12700, -50000)
+    )
+    net = pin.net_nos[0]
+    cx, cy = router._cell_of(pin.location)
+    nodes = router._escape_nodes(pin, net, router._conns, [0], (cx, cy))
+    columns = {x for x, y, _ in nodes if y != cy}
+    assert {cx - 1, cx, cx + 1} <= columns

tests/test_cli.py

@@ -158,6 +158,7 @@ def test_cli_supported_combinations_are_accepted(tmp_path):
         "orders": ["--orders", "2"],
         "promote": ["--promote-failures", "2"],
         "access": ["--access-cost", "5"],
+        "negotiate": ["--negotiate", "2"],
         "rollback": ["--no-rollback"],
     }
     for engine, options in ENGINE_OPTIONS.items():