diff -r 221728aeeb7e -r fa8df5a14486 src/bisection_tree/btfn.rs
--- a/src/bisection_tree/btfn.rs	Wed Sep 03 19:55:05 2025 -0500
+++ b/src/bisection_tree/btfn.rs	Wed Sep 03 20:19:41 2025 -0500
@@ -435,7 +435,7 @@
     type Codomain = V;
 
     fn apply<I: Instance<Loc<N, F>>>(&self, x: I) -> Self::Codomain {
-        let xc = x.cow();
+        let xc = x.decompose();
         self.bt
             .iter_at(&*xc)
             .map(|&d| self.generator.support_for(d).apply(&*xc))
@@ -454,7 +454,7 @@
     type Derivative = V;
 
     fn differential_impl<I: Instance<Loc<N, F>>>(&self, x: I) -> Self::Derivative {
-        let xc = x.cow();
+        let xc = x.decompose();
         self.bt
             .iter_at(&*xc)
             .map(|&d| self.generator.support_for(d).differential(&*xc))