diff --git a/package/package.json b/package/package.json
index 39d12e3..2d4e8fd 100644
--- a/package/package.json
+++ b/package/package.json
@@ -63,15 +63,15 @@
   },
   "devDependencies": {
     "@sveltejs/kit": "^1.27.0",
-    "@trpc/client": "^10.45.2",
-    "@trpc/server": "^10.45.2",
+    "@trpc/client": "^11.4.3",
+    "@trpc/server": "^11.4.3",
     "@types/ws": "^8.18.0",
     "typescript": "^5.8.2"
   },
   "peerDependencies": {
     "@sveltejs/adapter-node": ">=1.2",
-    "@trpc/client": "^10.0.0",
-    "@trpc/server": "^10.0.0",
+    "@trpc/client": "^11.4.3",
+    "@trpc/server": "^11.4.3",
     "ws": ">=8"
   }
 }
diff --git a/package/src/client.ts b/package/src/client.ts
index 14e0f6a..6a18e0c 100644
--- a/package/src/client.ts
+++ b/package/src/client.ts
@@ -47,7 +47,7 @@ type CreateTRPCClientOptions<Router extends AnyRouter> = (
    * A function that transforms the data before transferring it.
    * @see https://trpc.io/docs/data-transformers
    */
-  transformer?: Router['_def']['_config']['transformer'];
+  transformer?: any;
 };
 
 /**
@@ -59,7 +59,7 @@ export function createTRPCClient<Router extends AnyRouter>(
     url: '/trpc'
   }
 ) {
-  if (links) return internalCreateTRPCClient<Router>({ transformer, links });
+  if (links) return internalCreateTRPCClient<Router>({ links });
 
   if (typeof window === 'undefined' && !init) {
     throw new Error(
@@ -68,13 +68,13 @@ export function createTRPCClient<Router extends AnyRouter>(
   }
 
   return internalCreateTRPCClient<Router>({
-    transformer,
     links: [
       httpBatchLink({
         url:
           typeof window === 'undefined' ? `${init.url.origin}${url}` : `${location.origin}${url}`,
-        fetch: typeof window === 'undefined' ? init.fetch : init?.fetch ?? window.fetch,
-        headers
+        fetch: typeof window === 'undefined' ? init.fetch : (init?.fetch ?? window.fetch),
+        headers,
+        ...(transformer && { transformer })
       })
     ]
   });
diff --git a/package/src/server.ts b/package/src/server.ts
index 3037ed0..8f9fa21 100644
--- a/package/src/server.ts
+++ b/package/src/server.ts
@@ -6,7 +6,7 @@ import type {
   inferRouterContext,
   inferRouterError
 } from '@trpc/server';
-import { resolveHTTPResponse, type ResponseMeta } from '@trpc/server/http';
+import { resolveResponse, type ResponseMeta } from '@trpc/server/http';
 import type { TRPCResponse } from '@trpc/server/rpc';
 import { serialize, type CookieSerializeOptions } from 'cookie';
 import type { ValidRoute } from './ValidRoute';
@@ -52,8 +52,8 @@ export function createTRPCHandle<Router extends AnyRouter, URL extends string>({
   responseMeta?: (opts: {
     data: TRPCResponse<unknown, inferRouterError<Router>>[];
     ctx?: inferRouterContext<Router>;
-    paths?: string[];
-    type: ProcedureType;
+    paths: readonly string[];
+    type: ProcedureType | 'unknown';
     errors: TRPCError[];
   }) => ResponseMeta;
 
@@ -72,16 +72,7 @@ export function createTRPCHandle<Router extends AnyRouter, URL extends string>({
 }): Handle {
   return async ({ event, resolve }) => {
     if (event.url.pathname.startsWith(url + '/')) {
-      const request = event.request as Request & {
-        headers: Record<string, string | string[]>;
-      };
-
-      const req = {
-        method: request.method,
-        headers: request.headers,
-        query: event.url.searchParams,
-        body: await request.text()
-      };
+      const request = event.request;
 
       // Using the default `event.setHeaders` and `event.cookies` will not work
       // as the event in not resolved by SvelteKit. Instead, we "proxy" the access
@@ -115,27 +106,26 @@ export function createTRPCHandle<Router extends AnyRouter, URL extends string>({
         originalDeleteCookies(name, options);
       };
 
-      const httpResponse = await resolveHTTPResponse({
+      const httpResponse = await resolveResponse({
         router,
-        req,
+        req: request,
         path: event.url.pathname.substring(url.length + 1),
         createContext: async () => createContext?.(event),
         responseMeta,
         // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        onError: onError as any
+        error: onError as any
       });
 
-      const { status, headers, body } = httpResponse as {
-        status: number;
-        headers: Record<string, string>;
-        body: string;
-      };
+      const status = httpResponse.status;
+      const body = await httpResponse.text();
 
       const finalHeaders = new Headers();
 
-      for (const [key, value] of Object.entries(headers)) {
+      // Copy headers from response
+      httpResponse.headers.forEach((value, key) => {
         finalHeaders.set(key, value);
-      }
+      });
+
       for (const [key, value] of Object.entries(headersProxy)) {
         finalHeaders.set(key, value);
       }
diff --git a/package/src/websocket/client.ts b/package/src/websocket/client.ts
index ef8661b..71c7684 100644
--- a/package/src/websocket/client.ts
+++ b/package/src/websocket/client.ts
@@ -6,9 +6,9 @@ import {
 } from '@trpc/client';
 import { AnyRouter } from '@trpc/server';
 
-export function createTRPCWebSocketClient<Router extends AnyRouter>(): ReturnType<
-  typeof createTRPCProxyClient<Router>
-> {
+export function createTRPCWebSocketClient<Router extends AnyRouter>(opts?: {
+  transformer?: any;
+}): ReturnType<typeof createTRPCProxyClient<Router>> {
   if (typeof location === 'undefined') return;
 
   const uri = `${location.protocol === 'http:' ? 'ws:' : 'wss:'}//${location.host}/trpc`;
@@ -18,6 +18,11 @@ export function createTRPCWebSocketClient<Router extends AnyRouter>(): ReturnTyp
   });
 
   return createTRPCProxyClient<Router>({
-    links: [wsLink({ client: wsClient })]
-  } as CreateTRPCClientOptions<Router>);
+    links: [
+      wsLink({
+        client: wsClient,
+        ...(opts?.transformer && { transformer: opts.transformer })
+      })
+    ]
+  });
 }