diff --git a/src/types/fetch/fetch.ts b/src/types/fetch/fetch.ts
index 2f0e2dd704..07251a82c5 100644
--- a/src/types/fetch/fetch.ts
+++ b/src/types/fetch/fetch.ts
@@ -5,14 +5,24 @@ import type { MatchedRoutes } from "./_match.ts";
 // An interface to extend in a local project
 export interface InternalApi {}
 
+// Opt-in configuration interface to augment in a local project, e.g.
+//   declare module "nitropack" {
+//     interface NitroFetchConfig { flatRequest: true }
+//   }
+export interface NitroFetchConfig {}
+
 // TODO: upgrade to uppercase for h3 v2 types and web consistency
 type RouterMethod = Lowercase<HTTPMethod>;
 
-export type NitroFetchRequest =
+type TypedNitroFetchRequest =
   | Exclude<keyof InternalApi, `/_${string}` | `/api/_${string}`>
   | Exclude<FetchRequest, string>
   | (string & {});
 
+export type NitroFetchRequest = NitroFetchConfig extends { flatRequest: true }
+  ? string
+  : TypedNitroFetchRequest;
+
 export type MiddlewareOf<
   Route extends string,
   Method extends RouterMethod | "default",