more ucp

cmd/checkout/main.go

@@ -194,8 +194,12 @@ func main() {
 		checkoutUCP = ucp.WithSigning(checkoutUCP, signer)
 		log.Print("ucp signing enabled")
 	}
-	mux.Handle("/ucp/v1/checkout-sessions", checkoutUCP)
-	mux.Handle("/ucp/v1/checkout-sessions/", checkoutUCP)
+	// StripPrefix is required because the sub-mux (CheckoutHandler) registers
+	// routes like "GET /{id}" which expect a relative path; Go's ServeMux
+	// passes the full request path without stripping the prefix.
+	// Only the subtree pattern is registered (see comment in cmd/cart/main.go
+	// for why the exact-match pattern is omitted).
+	mux.Handle("/ucp/v1/checkout-sessions/", http.StripPrefix("/ucp/v1/checkout-sessions", checkoutUCP))
 
 	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
 		grainCount, capacity := pool.LocalUsage()