diff --git a/src/freeroute/route/exact_router.py b/src/freeroute/route/exact_router.py
index 4db2f55..c9dd55b 100644
--- a/src/freeroute/route/exact_router.py
+++ b/src/freeroute/route/exact_router.py
@@ -207,7 +207,9 @@ def route_board_exact(
             for i, (box, box_layers) in enumerate(boxes)
             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)
@@ -670,6 +672,15 @@ 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()
 
diff --git a/src/freeroute/route/grid_router.py b/src/freeroute/route/grid_router.py
index 47c3ca6..597794c 100644
--- a/src/freeroute/route/grid_router.py
+++ b/src/freeroute/route/grid_router.py
@@ -299,9 +299,9 @@ 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] = {}
         # every connection whose via covers a cell, in claim order: a via two
-        # connections share still blocks after the first of them is ripped
+        # 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]] = {}
@@ -520,9 +520,7 @@ 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:
@@ -537,6 +535,17 @@ 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
@@ -927,9 +936,7 @@ class GridRouter:
                     if not any(g.overlaps(t) for tiles in other for t in tiles for g in grown):
                         continue
                 owners.add(owner)
-            via_owner = self._via_owner.get(c)
-            if via_owner is not None and conns[via_owner].net_no != net_no:
-                owners.add(via_owner)
+            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:
@@ -1206,7 +1213,6 @@ class GridRouter:
                 if conn.index not in claims:
                     claims.append(conn.index)
                     conn.via_halo.append(c)
-                self._via_owner.setdefault(c, conn.index)
         ends = ((conn.a_end, wire_segs[0], 0), (conn.b_end, wire_segs[-1], -1)) if wire_segs else ()
         conn.stubs = []
         for pin, (layer, cells), at in ends:
@@ -1259,11 +1265,6 @@ class GridRouter:
             claims = self._via_claims.get(cell)
             if claims is not None and conn.index in claims:
                 claims.remove(conn.index)
-            if self._via_owner.get(cell) == conn.index:
-                if claims:
-                    self._via_owner[cell] = claims[0]
-                else:
-                    del self._via_owner[cell]
             if claims is not None and not claims:
                 del self._via_claims[cell]
         conn.via_halo = []
@@ -1308,9 +1309,7 @@ class GridRouter:
             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)
diff --git a/tests/route/test_grid_exact_agreement.py b/tests/route/test_grid_exact_agreement.py
index 9c08559..af234f7 100644
--- a/tests/route/test_grid_exact_agreement.py
+++ b/tests/route/test_grid_exact_agreement.py
@@ -143,11 +143,48 @@ def test_a_shared_via_keeps_its_footprint_when_one_user_is_ripped():
     router._rip(first)
 
     assert second.routed and via in second.via_cells
-    assert all(router._via_owner.get(c) == second.index for c in footprint)
+    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)
@@ -225,3 +262,23 @@ def test_a_pad_cell_check_uses_the_rotated_outline():
         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)
diff --git a/tests/route/test_rollback.py b/tests/route/test_rollback.py
index 38ab250..1d3edd6 100644
--- a/tests/route/test_rollback.py
+++ b/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)