fix(dev-server): route server.fn() RPC to a handler in production

server.fn() posts to POST /__wrnexus/rpc. Dev intercepts that path before
handlers.fetch and routes it to a createRpcHandler instance built from
loadWrnServerModule; createProductionServer/createProductionHandlers had no
such route, so the request fell through to the internal-caller-gated
inter-app service RPC and 404'd.

Add resolveProdServerFunctions(), a synchronous equivalent of dev's resolve
that searches the already-statically-imported ProdManifest components/pages/
layouts for __wrnexusServerFunctions + __wrnexusRpcManifest, and wire it into
createProductionHandlers with the same validateCsrf + withServerFnRequestContext
wrapping dev uses. Move those two helpers into a new rpc-shared.ts so prod.ts
can use them without a circular import through index.ts.

Add packages/dev-server/test/prod-server-fn-rpc.test.ts covering a successful
call, CSRF rejection, and clean 404s for an unknown component/function.

packages/dev-server/src/index.ts

@@ -8,14 +8,7 @@
 
 import { mkdirSync, readFileSync, rmSync, writeFileSync } from "node:fs";
 import { resolve, dirname, isAbsolute, join } from "node:path";
-import {
+import { type Middleware, type Mode, type SecurityConfig, type SeoConfig } from "@wrnexus/core";
-  createContext,
-  runWithRequestContext,
-  type Middleware,
-  type Mode,
-  type SecurityConfig,
-  type SeoConfig,
-} from "@wrnexus/core";
 import { buildRouter, type Router } from "@wrnexus/router";
 import {
   resolveThemeConfig,
@@ -83,36 +76,11 @@ export { getWrnCompileMetrics, resetWrnCompileMetrics } from "./pipeline.ts";
 export type { WrnCompileMetrics } from "./pipeline.ts";
 import { resetDevCache } from "./cache.ts";
 
-export function validateRpcCsrf(request: Request): boolean {
+// Shared with prod.ts — kept in their own module to avoid a circular import
-  const url = new URL(request.url);
+// (index.ts re-exports createProductionServer/createProductionHandlers from
-  const origin = request.headers.get("origin");
+// prod.ts, so prod.ts cannot import these back from index.ts).
-  if (origin && origin !== url.origin) return false;
+import { validateRpcCsrf, withServerFnRequestContext } from "./rpc-shared.ts";
-  const cookieHeader = request.headers.get("cookie") ?? "";
+export { validateRpcCsrf, withServerFnRequestContext };
-  const cookieToken =
-    /(?:^|;\s*)wrn-csrf=([^;]+)/.exec(cookieHeader)?.[1] ??
-    /(?:^|;\s*)wrnexus_csrf=([^;]+)/.exec(cookieHeader)?.[1];
-  const headerToken = request.headers.get("x-csrf-token") ?? request.headers.get("x-wrnexus-csrf");
-  return Boolean(cookieToken && headerToken && decodeURIComponent(cookieToken) === headerToken);
-}
-
-/**
- * Wrap the server-function RPC handler so it runs inside the request's
- * AsyncLocalStorage context. `/__wrnexus/rpc` is intercepted BEFORE
- * `handlers.fetch` (fetchHandler) in the dev server, so a server function
- * called via `server.fn()` from the browser runs entirely outside
- * fetchHandler's own context wrap. It runs user code directly, so — like
- * every other entry point that runs user server code — it needs the request
- * context too.
- */
-export function withServerFnRequestContext(
-  handler: (request: Request) => Promise<Response>,
-): (request: Request) => Promise<Response> {
-  return (request: Request) => {
-    const url = new URL(request.url);
-    const ctx = createContext(request, url);
-    return runWithRequestContext(ctx, () => handler(request));
-  };
-}
 
 import type { DevToolbarConfig } from "@wrnexus/dev-toolbar/types";
 import { createPluginRunner, discoverPlugins, type PluginInput } from "@wrnexus/plugin";

packages/dev-server/src/prod.ts

@@ -54,6 +54,8 @@ import { createHandlers, type AssetServer, type WsData } from "./runtime.ts";
 import { servePublicAsset } from "./public.ts";
 import type { ClientRuntimeDefinition } from "@wrnexus/plugin";
 import { HmrHub } from "./hmr.ts";
+import { createRpcHandler, type RpcManifestContract } from "@wrnexus/ssr/rpc";
+import { validateRpcCsrf, withServerFnRequestContext } from "./rpc-shared.ts";
 
 type RouteModule = Record<string, unknown>;
 
@@ -429,6 +431,48 @@ function createProdAssetServer(opts: ProdOptions): AssetServer {
  * wraps it in `Bun.serve`, `serveNode` bridges it onto `node:http`, and edge or
  * serverless targets can call `fetch` directly.
  */
+/**
+ * Resolve the `.wrn` server-function module owning `rawComponent`, from the
+ * manifest's already-loaded static imports (production has no dynamic module
+ * loading, so unlike dev's `resolve` this is a synchronous in-memory search).
+ * Searches components (preferring an exact name match), then pages, then
+ * layouts — mirroring the candidate order dev's `resolve` walks in
+ * index.ts, minus `router.stores`, which the production router never
+ * populates (see `buildProdRouter` above).
+ */
+function resolveProdServerFunctions(
+  manifest: ProdManifest,
+  rawComponent: string,
+): {
+  functions: Record<string, (...args: any[]) => any>;
+  manifest: RpcManifestContract[];
+} | null {
+  const componentName = rawComponent.split(":", 1)[0] ?? rawComponent;
+  const preferred = manifest.components.find(
+    (entry) => entry.name.toLowerCase() === componentName.toLowerCase(),
+  );
+  const candidates: RouteModule[] = [
+    ...(preferred ? [preferred.mod] : []),
+    ...manifest.pages.map((entry) => entry.mod),
+    ...manifest.layouts.map((entry) => entry.mod),
+    ...manifest.components.filter((entry) => entry !== preferred).map((entry) => entry.mod),
+  ];
+  for (const mod of new Set(candidates)) {
+    const functions = mod.__wrnexusServerFunctions;
+    const rpcManifest = mod.__wrnexusRpcManifest;
+    if (!functions || typeof functions !== "object" || !Array.isArray(rpcManifest)) continue;
+    const ownsComponent = rpcManifest.some(
+      (entry: any) => String(entry?.component ?? "").toLowerCase() === componentName.toLowerCase(),
+    );
+    if (!ownsComponent) continue;
+    return {
+      functions: functions as Record<string, (...args: any[]) => any>,
+      manifest: rpcManifest as RpcManifestContract[],
+    };
+  }
+  return null;
+}
+
 export function createProductionHandlers(
   manifest: ProdManifest,
   opts: ProdOptions,
@@ -529,7 +573,22 @@ export function createProductionHandlers(
     realtimeBus: realtimeBusFromConfig(opts.realtime),
   });
 
-  return handlers;
+  // `/__wrnexus/rpc` (server.fn() calls from the browser) must be intercepted
+  // BEFORE handlers.fetch, exactly as dev does in index.ts — it is NOT an app
+  // route and must never fall through to isRpcPath/handleRpcRequest (the
+  // internal-caller-gated inter-app service RPC), which would 404 it.
+  const rpcHandler = createRpcHandler({
+    resolve: async (rawComponent) => resolveProdServerFunctions(manifest, rawComponent),
+    validateCsrf: validateRpcCsrf,
+  });
+  const serverFnRpcHandler = withServerFnRequestContext(rpcHandler);
+  const appFetch = handlers.fetch;
+  const fetchWithServerFnRpc: typeof handlers.fetch = (request, server) => {
+    if (new URL(request.url).pathname === "/__wrnexus/rpc") return serverFnRpcHandler(request);
+    return appFetch(request, server);
+  };
+
+  return { ...handlers, fetch: fetchWithServerFnRpc };
 }
 
 /**

packages/dev-server/src/rpc-shared.ts

@@ -0,0 +1,46 @@
+/**
+ * Shared server-function RPC helpers used by both the dev server (index.ts)
+ * and the production server (prod.ts). Kept in their own module so prod.ts
+ * can import them without creating a circular dependency on index.ts (which
+ * itself re-exports `createProductionServer`/`createProductionHandlers` from
+ * prod.ts).
+ */
+
+import { createContext, runWithRequestContext } from "@wrnexus/core";
+
+/**
+ * CSRF check for `/__wrnexus/rpc` (the server-function RPC endpoint the
+ * browser runtime calls for `server.fn()`). Requires a same-origin request
+ * carrying a matching CSRF cookie + header pair — the standard double-submit
+ * cookie pattern.
+ */
+export function validateRpcCsrf(request: Request): boolean {
+  const url = new URL(request.url);
+  const origin = request.headers.get("origin");
+  if (origin && origin !== url.origin) return false;
+  const cookieHeader = request.headers.get("cookie") ?? "";
+  const cookieToken =
+    /(?:^|;\s*)wrn-csrf=([^;]+)/.exec(cookieHeader)?.[1] ??
+    /(?:^|;\s*)wrnexus_csrf=([^;]+)/.exec(cookieHeader)?.[1];
+  const headerToken = request.headers.get("x-csrf-token") ?? request.headers.get("x-wrnexus-csrf");
+  return Boolean(cookieToken && headerToken && decodeURIComponent(cookieToken) === headerToken);
+}
+
+/**
+ * Wrap the server-function RPC handler so it runs inside the request's
+ * AsyncLocalStorage context. `/__wrnexus/rpc` is intercepted BEFORE
+ * `handlers.fetch` (fetchHandler) in both dev and production, so a server
+ * function called via `server.fn()` from the browser runs entirely outside
+ * fetchHandler's own context wrap. It runs user code directly, so — like
+ * every other entry point that runs user server code — it needs the request
+ * context too.
+ */
+export function withServerFnRequestContext(
+  handler: (request: Request) => Promise<Response>,
+): (request: Request) => Promise<Response> {
+  return (request: Request) => {
+    const url = new URL(request.url);
+    const ctx = createContext(request, url);
+    return runWithRequestContext(ctx, () => handler(request));
+  };
+}

packages/dev-server/test/prod-server-fn-rpc.test.ts

@@ -0,0 +1,103 @@
+import { describe, expect, test } from "bun:test";
+import { createProductionHandlers, type ProdManifest } from "../src/prod.ts";
+
+/**
+ * Production-only regression test for server.fn() RPC. The browser runtime
+ * posts server-function calls to `/__wrnexus/rpc`. Dev intercepts that path
+ * with a handler built from `createRpcHandler` (index.ts). Production had no
+ * such route: the request fell through to `isRpcPath`/`handleRpcRequest` —
+ * the *inter-app service* RPC, gated by an internal-caller header a browser
+ * never sends — and 404'd. See `resolveProdServerFunctions` in prod.ts.
+ */
+
+// Shape emitted by the compiler for a `.wrn` file with server functions
+// (packages/compiler/src/server-codegen.ts): a plain functions object plus a
+// manifest array of `{ component, function, parameters?, returnType? }`.
+function serverModule(component: string) {
+  return {
+    __wrnexusServerFunctions: {
+      async greet(name: string) {
+        return `hello ${name}`;
+      },
+    },
+    __wrnexusRpcManifest: [
+      {
+        component,
+        function: "greet",
+        parameters: [{ name: "name", type: "string", optional: false }],
+        returnType: "string",
+      },
+    ],
+  };
+}
+
+function manifest(): ProdManifest {
+  return {
+    pages: [],
+    api: [],
+    realtime: [],
+    middleware: [],
+    components: [{ name: "Greeter", mod: serverModule("Greeter") }],
+    layouts: [],
+  };
+}
+
+const CSRF_TOKEN = "test-token";
+const CSRF_HEADERS = {
+  origin: "http://localhost",
+  cookie: `wrn-csrf=${CSRF_TOKEN}`,
+  "x-csrf-token": CSRF_TOKEN,
+};
+
+function rpcRequest(body: unknown, headers: Record<string, string> = CSRF_HEADERS): Request {
+  return new Request("http://localhost/__wrnexus/rpc", {
+    method: "POST",
+    headers: { "content-type": "application/json", ...headers },
+    body: JSON.stringify(body),
+  });
+}
+
+describe("production server.fn() RPC (/__wrnexus/rpc)", () => {
+  test("a valid call to an existing server function succeeds, not 404", async () => {
+    const handlers = createProductionHandlers(manifest(), {});
+    const req = rpcRequest({ component: "Greeter", function: "greet", args: ["world"] });
+    const res = await handlers.fetch(req, {} as never);
+    expect(res).toBeDefined();
+    expect(res!.status).toBe(200);
+    const body = await res!.json();
+    expect(body).toMatchObject({ ok: true, value: "hello world" });
+  });
+
+  test("a request without a valid CSRF token is rejected", async () => {
+    const handlers = createProductionHandlers(manifest(), {});
+    const req = rpcRequest(
+      { component: "Greeter", function: "greet", args: ["world"] },
+      { "content-type": "application/json" },
+    );
+    const res = await handlers.fetch(req, {} as never);
+    expect(res).toBeDefined();
+    expect(res!.status).toBe(403);
+    const body = await res!.json();
+    expect(body.ok).toBe(false);
+  });
+
+  test("an unknown component fails cleanly (404), not with an internal error", async () => {
+    const handlers = createProductionHandlers(manifest(), {});
+    const req = rpcRequest({ component: "NoSuchComponent", function: "greet", args: [] });
+    const res = await handlers.fetch(req, {} as never);
+    expect(res).toBeDefined();
+    expect(res!.status).toBe(404);
+    const body = await res!.json();
+    expect(body.ok).toBe(false);
+  });
+
+  test("an unknown function on a known component fails cleanly (404)", async () => {
+    const handlers = createProductionHandlers(manifest(), {});
+    const req = rpcRequest({ component: "Greeter", function: "notARealFunction", args: [] });
+    const res = await handlers.fetch(req, {} as never);
+    expect(res).toBeDefined();
+    expect(res!.status).toBe(404);
+    const body = await res!.json();
+    expect(body.ok).toBe(false);
+  });
+});