fix: prevent URL parameter loss during path rewrites

go.mod

@@ -0,0 +1,5 @@
+module github.com/madalynerlge2/chi
+
+go 1.25.12
+
+require github.com/go-chi/chi/v5 v5.3.1 // indirect

go.sum

@@ -0,0 +1,2 @@
+github.com/go-chi/chi/v5 v5.3.1 h1:3j4HZLGZQ3JpMCrPJF/Jl3mYJfWLKBfNJ6quurUGCf8=
+github.com/go-chi/chi/v5 v5.3.1/go.mod h1:R+tYY2hNuVUUjxoPtqUdgBqevM9s9njzkTLutVsOCto=

rewrite.go

@@ -0,0 +1,16 @@
+package chi
+
+import (
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+)
+
+// RewritePath safely updates both the Request URL Path and the chi routing context.
+// This prevents URL parameter loss when middleware forcibly overwrites Request.URL.Path.
+func RewritePath(r *http.Request, newPath string) {
+	r.URL.Path = newPath
+	if rctx := chi.RouteContext(r.Context()); rctx != nil {
+		rctx.RoutePath = newPath
+	}
+}

rewrite_test.go

@@ -0,0 +1,42 @@
+package chi
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/go-chi/chi/v5"
+)
+
+func TestRewritePath(t *testing.T) {
+	r := chi.NewRouter()
+
+	// Middleware that rewrites the path using the new helper
+	r.Use(func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+			if req.URL.Path == "/legacy/123" {
+				RewritePath(req, "/users/123")
+			}
+			next.ServeHTTP(w, req)
+		})
+	})
+
+	r.Get("/users/{id}", func(w http.ResponseWriter, req *http.Request) {
+		id := chi.URLParam(req, "id")
+		if id != "123" {
+			t.Errorf("expected URL param 'id' to be '123', got '%s'", id)
+		}
+		w.Write([]byte("ok"))
+	})
+
+	ts := httptest.NewServer(r)
+	defer ts.Close()
+
+	res, err := http.Get(ts.URL + "/legacy/123")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.StatusCode != http.StatusOK {
+		t.Errorf("expected status 200, got %d", res.StatusCode)
+	}
+}