aklinker1 · aklinker1 · Mar 14, 2026 · Mar 14, 2026
diff --git a/bun.lock b/bun.lock
diff --git a/jsr.json b/jsr.json
@@ -15,6 +15,7 @@
     "./schema": "./src/schema.ts",
     "./adapters/zod-schema-adapter": "./src/adapters/zod-schema-adapter.ts",
     "./transports/bun-transport": "./src/transports/bun-transport.ts",
+    "./transports/fetch-transport": "./src/transports/fetch-transport.ts",
     "./transports/deno-transport": "./src/transports/deno-transport.ts"
   }
 }
diff --git a/package.json b/package.json
@@ -36,6 +36,10 @@
       "types": "./dist/transports/bun-transport.d.mts",
       "default": "./dist/transports/bun-transport.mjs"
     },
+    "./transports/fetch-transport": {
+      "types": "./dist/transports/fetch-transport.d.mts",
+      "default": "./dist/transports/fetch-transport.mjs"
+    },
     "./transports/deno-transport": {
       "types": "./dist/transports/deno-transport.d.mts",
       "default": "./dist/transports/deno-transport.mjs"
@@ -58,7 +62,7 @@
   ],
   "scripts": {
     "dev": "bun test --watch",
-    "build": "tsdown src/{index,types,client,testing,schema,adapters/zod-schema-adapter,transports/bun-transport,transports/deno-transport}.ts",
+    "build": "tsdown src/{index,types,client,testing,schema,adapters/zod-schema-adapter,transports/bun-transport,transports/fetch-transport,transports/deno-transport}.ts",
     "bench": "bun run src/__tests__/bench.ts",
     "example": "bun --watch run example.ts",
     "example:prod": "NODE_ENV=production bun run example",
@@ -80,6 +84,7 @@
     "@opentelemetry/sdk-trace-node": "^2.5.0",
     "@opentelemetry/semantic-conventions": "^1.39.0",
     "@types/bun": "latest",
+    "@types/deno": "^2.5.0",
     "@typescript/native-preview": "^7.0.0-dev.20260202.1",
     "changelogen": "^0.6.2",
     "cookie": "^1.1.1",
@@ -99,11 +104,15 @@
     "zod": "^4.1.11"
   },
   "peerDependencies": {
-    "@types/bun": "*"
+    "@types/bun": "*",
+    "@types/deno": "*"
   },
   "peerDependenciesMeta": {
     "@types/bun": {
       "optional": true
+    },
+    "@types/deno": {
+      "optional": true
     }
   }
 }
diff --git a/src/__tests__/app.test.ts b/src/__tests__/app.test.ts
@@ -6,7 +6,8 @@ import { zodSchemaAdapter } from "../adapters/zod-schema-adapter";
 import { createApp } from "../app";
 import { HttpStatus } from "../status";
 import { createTestAppClient } from "../testing";
-import type { AnyDef, GetAppData } from "../types";
+import type { AnyDef, GetAppData, Transport } from "../types";
+import { createBunTransport } from "../transports/bun-transport";
 
 // Silence console.error logs
 globalThis.console.error = mock();
@@ -466,6 +467,7 @@ describe("App", () => {
             "/": AnyDef;
           };
         };
+        transport: Transport;
       }>();
       expect(actual).not.toMatchObject({ a: "A" });
     });
@@ -489,6 +491,7 @@ describe("App", () => {
             "/": AnyDef;
           };
         };
+        transport: Transport;
       }>();
       expect(actual).toMatchObject({ a: "A" });
     });
@@ -608,4 +611,21 @@ describe("App", () => {
       });
     });
   });
+
+  describe("transports", () => {
+    it("should include transport decorations", async () => {
+      const expected = Symbol("server") as any;
+
+      let actual: Bun.Server;
+      const app = createApp({
+        schemaAdapter: zodSchemaAdapter,
+        transport: createBunTransport(),
+      }).get("/", (ctx) => {
+        actual = ctx.server;
+      });
+      await app.build()(new Request("http://localhost:3000"), expected);
+
+      expect(actual!).toBe(expected);
+    });
+  });
 });
diff --git a/src/__tests__/client.test.ts b/src/__tests__/client.test.ts
@@ -1,7 +1,7 @@
 import { describe, it, expect, mock } from "bun:test";
 import { createApp } from "../app";
 import { createTestAppClient } from "../testing";
-import type { App } from "../types";
+import type { App, Transport } from "../types";
 import type { GetClientRoutes } from "../client";
 import { expectTypeOf } from "expect-type";
 import { z } from "zod/v4";
@@ -154,6 +154,7 @@ describe("Client", () => {
             "/images": {};
           };
         };
+        transport: Transport;
       }>;
       type Expected = {
         GET: {

diff --git a/src/__tests__/types.test.ts b/src/__tests__/types.test.ts
@@ -5,6 +5,7 @@ import { z } from "zod/v4";
 import type { StandardSchemaV1 } from "@standard-schema/spec";
 import { ErrorResponse } from "../schema";
 import type { HttpStatus } from "../status";
+import type { BunTransport } from "../transports/bun-transport";
 
 describe("Types", () => {
   describe("MergeRoutes", () => {
@@ -86,6 +87,7 @@ describe("Types", () => {
         routes: {};
         exported: false;
         ctx: { a: "A" };
+        transport: t.Transport;
       };
       type B = {
         routes: { GET: { "/b": {} } };
@@ -95,6 +97,7 @@ describe("Types", () => {
         exported: A["exported"];
         ctx: { a: "A" };
         routes: { GET: { "/b": {} } };
+        transport: t.Transport;
       };
 
       type Actual = t.MergeAppData<A, B>;
@@ -108,18 +111,21 @@ describe("Types", () => {
         exported: false;
         ctx: { a: "A" };
         routes: { GET: { "/a": {} } };
+        transport: t.Transport;
       };
       type B = {
         prefix: "/test";
         exported: true;
         ctx: { b: "B" };
         routes: { GET: { "/b": {} } };
+        transport: BunTransport;
       };
       type Expected = {
         prefix: "/test";
         exported: true;
         ctx: { a: "A"; b: "B" };
         routes: { GET: { "/a": {}; "/b": {} } };
+        transport: t.Transport;
       };
 
       type Actual = t.MergeAppData<A, B>;
@@ -389,6 +395,7 @@ describe("Types", () => {
             [p in Path]: Def;
           };
         };
+        transport: t.Transport;
       };
       type Expected = {
         params: Record<string, string>;
@@ -414,6 +421,7 @@ describe("Types", () => {
             [p in Path]: Def;
           };
         };
+        transport: t.Transport;
       };
       type Expected = Ctx;
 
@@ -434,6 +442,7 @@ describe("Types", () => {
             [p in Path]: Def;
           };
         };
+        transport: t.Transport;
       };
       type Expected = {
         route: Path;
@@ -464,6 +473,7 @@ describe("Types", () => {
             [p in Path]: Def;
           };
         };
+        transport: t.Transport;
       };
       type Expected = {
         route: Path;
@@ -487,6 +497,7 @@ describe("Types", () => {
         routes: {
           GET: { "/test": { body: z.ZodObject<{ id: z.ZodString }> } };
         };
+        transport: t.Transport;
       }>;
       type Expected = MyApp;
 
@@ -503,6 +514,7 @@ describe("Types", () => {
         routes: {
           GET: { "/test": { body: z.ZodObject<{ id: z.ZodString }> } };
         };
+        transport: t.Transport;
       }>;
       type Expected = t.App<{
         prefix: "";
@@ -511,6 +523,7 @@ describe("Types", () => {
         routes: {
           GET: { "/api/test": { body: z.ZodObject<{ id: z.ZodString }> } };
         };
+        transport: t.Transport;
       }>;
 
       type Actual = t.ApplyAppPrefix<MyApp>;
@@ -541,6 +554,7 @@ describe("Types", () => {
             };
           };
         };
+        transport: t.Transport;
       };
       type Expected = {
         ctx: AppData["ctx"];
@@ -555,6 +569,7 @@ describe("Types", () => {
             "/api/users": AppData["routes"]["POST"]["/users"];
           };
         };
+        transport: t.Transport;
       };
 
       type Actual = t.ApplyAppDataPrefix<AppData>;
@@ -570,6 +585,7 @@ describe("Types", () => {
         exported: false;
         prefix: "/api";
         routes: {};
+        transport: t.Transport;
       };
       type ChildAppData = {
         ctx: { b: "b" };
@@ -578,12 +594,14 @@ describe("Types", () => {
         routes: {
           GET: { "/users": t.AnyDef };
         };
+        transport: BunTransport;
       };
       type Expected = {
         ctx: { a: "a" };
         exported: false;
         prefix: "/api";
         routes: ChildAppData["routes"];
+        transport: t.Transport;
       };
 
       type Actual = t.UseAppData<ParentAppData, ChildAppData>;
@@ -597,6 +615,7 @@ describe("Types", () => {
         exported: false;
         prefix: "/api";
         routes: {};
+        transport: t.Transport;
       };
       type ChildAppData = {
         ctx: { b: "b" };
@@ -605,6 +624,7 @@ describe("Types", () => {
         routes: {
           GET: { "/users": t.AnyDef };
         };
+        transport: BunTransport;
       };
       type Expected = {
         ctx: { a: "a"; b: "b" };
@@ -613,6 +633,7 @@ describe("Types", () => {
         routes: {
           GET: { "/users": t.AnyDef };
         };
+        transport: t.Transport;
       };
 
       type Actual = t.UseAppData<ParentAppData, ChildAppData>;

diff --git a/src/app.ts b/src/app.ts
@@ -3,9 +3,9 @@ import { addRoute, createRouter } from "rou3";
 import { compileRouter } from "rou3/compiler";
 import { compileFetchFunction } from "./internal/compile-fetch-function";
 import { compileRouteHandler } from "./internal/compile-route-handler";
-import { detectTransport } from "./internal/utils";
 import { buildOpenApiDocs, buildScalarHtml } from "./open-api";
 import type {
+  AnyTransport,
   App,
   BasePath,
   BasePrefix,
@@ -18,6 +18,7 @@ import type {
   ServerSideFetch,
   Transport,
 } from "./types";
+import { createFetchTransport } from "./transports/fetch-transport";
 
 let appIdInc = 0;
 const nextAppId = () => `app-${appIdInc++}`;
@@ -47,25 +48,33 @@ const nextHookId = (appId: string) => `${appId}/hook-${_hookIdInc++}`;
  * // Or serve the app yourself
  * const fetch = app.build();
  * Bun.serve({ fetch, ... });
- * Deno.serve({ fetch, ... });
+ * Deno.serve({ ... }, fetch);
  * ```
  *
  * @param options Configure application behavior.
  */
-export function createApp<TPrefix extends BasePrefix = "">(
-  options?: CreateAppOptions<TPrefix>,
+export function createApp<
+  TPrefix extends BasePrefix = "",
+  TTransport extends AnyTransport = Transport,
+>(
+  options?: CreateAppOptions<TPrefix, TTransport>,
 ): App<{
   ctx: {};
   exported: false;
   prefix: TPrefix;
   routes: {};
+  transport: TTransport;
 }> {
   const appId = nextAppId();
 
   const { origin = "http://localhost", prefix = "" } = options ?? {};
   const hooks: App["~zeta"]["hooks"] = {};
   const routes: App["~zeta"]["routes"] = {};
 
+  let _transport: AnyTransport;
+  const getTransport = (): AnyTransport =>
+    (_transport ??= options?.transport ?? createFetchTransport());
+
   const addRoutesEntry = (method: string, route: string, data: RouterData) => {
     routes[method] ??= {};
     if (routes[method][route]) {
@@ -132,7 +141,8 @@ export function createApp<TPrefix extends BasePrefix = "">(
       }
 
       const getRoute = compileRouter(router);
-      return compileFetchFunction({ getRoute, hooks, origin });
+      const transport = getTransport();
+      return compileFetchFunction({ getRoute, hooks, origin, transport });
     },
 
     getOpenApiSpec: () => {
@@ -148,7 +158,7 @@ export function createApp<TPrefix extends BasePrefix = "">(
     },
 
     listen: (port, cb) => {
-      const transport = options?.transport ?? detectTransport();
+      const transport = getTransport();
       transport.listen(port, app.build(), cb);
       return app;
     },
@@ -352,7 +362,10 @@ export function createApp<TPrefix extends BasePrefix = "">(
 /**
  * Configure how the app is created.
  */
-export type CreateAppOptions<TPrefix extends BasePrefix = ""> = {
+export type CreateAppOptions<
+  TPrefix extends BasePrefix = "",
+  TTransport extends AnyTransport = Transport,
+> = {
   /**
    * The origin to use when constructing URLs.
    * @default "http://localhost"
@@ -397,7 +410,7 @@ export type CreateAppOptions<TPrefix extends BasePrefix = ""> = {
    * });
    * ```
    */
-  transport?: Transport;
+  transport?: TTransport;
 
   /**
    * Where the OpenAPI JSON docs is hosted.