@@ -16,12 +16,8 @@ export function toPortableDevHandlers<T extends Pick<DevServerHandler, 'handler'
     }
     return {
       ...entry,
-      handler: defineEventHandler((event) => {
-        const portable = toPortableEvent(event)
-        // nitro mounts dev handlers by prefix, which strips the route from `event.path`
-        portable.url = getRequestURL(event)
-        return handler(portable)
-      }),
+      // nitro mounts dev handlers by prefix, which strips the route from `event.path`
+      handler: defineEventHandler(event => handler(toPortableEvent(event, () => getRequestURL(event)))),
     }
   })
 }
 
@@ -197,25 +197,26 @@ const portableEvents = new WeakMap<H3Event, RequestEvent>()
  *
  * Both shapes are served from one object: `req`, `res`, `url` and `~app` resolve to the web
  * view, everything else to the h3 v1 event, so h3's own helpers work on it too (they read
- * `event.node`, not its deprecated `req`/`res` aliases). Cached per event.
+ * `event.node`, not its deprecated `req`/`res` aliases). Cached per event, with the web view
+ * built on first access. `resolveURL` replaces how `url` is derived from the event's path.
  */
-export function toPortableEvent (event: H3Event): RequestEvent {
+export function toPortableEvent (event: H3Event, resolveURL?: () => URL): RequestEvent {
   const cached = portableEvents.get(event)
   if (cached) { return cached }
 
-  const web = toWebView(event)
+  let web: RendererEvent | undefined
   const portable = new Proxy(event, {
     get (target, property) {
       if (property === PORTABLE_EVENT) {
         return true
       }
       return WEB_PROPERTIES.has(property as string)
-        ? web[property as keyof RendererEvent]
+        ? (web ??= toWebView(event, resolveURL))[property as keyof RendererEvent]
         : Reflect.get(target, property, target)
     },
     set (target, property, value) {
       if (property === 'url') {
-        web.url = value
+        (web ??= toWebView(event, resolveURL)).url = value
         return true
       }
       return Reflect.set(target, property, value, target)
@@ -260,7 +261,7 @@ export function toRequestEvent (event: H3Event): RendererEvent {
  * than a copy of it, so a header the application sets through h3 and a header the renderer
  * sets are the same header.
  */
-function toWebView (event: H3Event): RendererEvent {
+function toWebView (event: H3Event, resolveURL = () => new URL(encodeEventPath(event.path), `${getRequestProtocol(event)}://${getRequestHost(event)}`)): RendererEvent {
   const node = event.node
   let request: Request | undefined
   let url: URL | undefined
@@ -286,7 +287,7 @@ function toWebView (event: H3Event): RendererEvent {
       return (request ??= toWebRequest(event))
     },
     get url () {
-      return (url ??= new URL(encodeEventPath(event.path), `${getRequestProtocol(event)}://${getRequestHost(event)}`))
+      return (url ??= resolveURL())
     },
     // the renderer rewrites the URL when a payload request renders the page it belongs to
     set url (value: URL) {
Original file line number	Diff line number	Diff line change
`@@ -16,12 +16,8 @@ export function toPortableDevHandlers<T extends Pick<DevServerHandler, 'handler'`
`16`	`16`	`}`
`17`	`17`	`return {`
`18`	`18`	`...entry,`
`19`		`- handler: defineEventHandler((event) => {`
`20`		`- const portable = toPortableEvent(event)`
`21`		- // nitro mounts dev handlers by prefix, which strips the route from `event.path`
`22`		`- portable.url = getRequestURL(event)`
`23`		`- return handler(portable)`
`24`		`- }),`
	`19`	+ // nitro mounts dev handlers by prefix, which strips the route from `event.path`
	`20`	`+ handler: defineEventHandler(event => handler(toPortableEvent(event, () => getRequestURL(event)))),`
`25`	`21`	`}`
`26`	`22`	`})`
`27`	`23`	`}`