diff --git a/common/router2.cc b/common/router2.cc
index 1f9196ab..813249b4 100644
--- a/common/router2.cc
+++ b/common/router2.cc
@@ -355,8 +355,7 @@ struct Router2
     {
         auto &wd = wire_data(wire);
         auto &nd = nets.at(net->udata);
-        float base_cost = ctx->getDelayNS(ctx->getPipDelay(pip).maxDelay() + ctx->getWireDelay(wire).maxDelay() +
-                                          ctx->getDelayEpsilon());
+        float base_cost = cfg.get_base_cost(ctx, wire, pip, crit_weight);
         int overuse = wd.curr_cong;
         float hist_cost = 1.0f + crit_weight * (wd.hist_cong_cost - 1.0f);
         float bias_cost = 0;
diff --git a/common/router2.h b/common/router2.h
index 34102f44..629453c6 100644
--- a/common/router2.h
+++ b/common/router2.h
@@ -21,6 +21,13 @@
 
 NEXTPNR_NAMESPACE_BEGIN
 
+inline float default_base_cost(Context *ctx, WireId wire, PipId pip, float crit_weight)
+{
+    (void)crit_weight; // unused
+    return ctx->getDelayNS(ctx->getPipDelay(pip).maxDelay() + ctx->getWireDelay(wire).maxDelay() +
+                           ctx->getDelayEpsilon());
+}
+
 struct Router2Cfg
 {
     Router2Cfg(Context *ctx);
@@ -51,6 +58,7 @@ struct Router2Cfg
     bool perf_profile = false;
 
     std::string heatmap;
+    std::function<float(Context *ctx, WireId wire, PipId pip, float crit_weight)> get_base_cost = default_base_cost;
 };
 
 void router2(Context *ctx, const Router2Cfg &cfg);