fix(vite): propagate service fetch errors in dev to match production

src/runtime/internal/vite/dev-worker.mjs

@@ -63,28 +63,24 @@ class ViteEnvRunner {
     }
   }
 
+  // Errors are intentionally not caught here: like production services,
+  // they propagate to the caller (the nitro app's error handler or the
+  // env-runner fetch boundary below).
   async fetch(req, init) {
-    if (this.entryError) {
-      return renderError(req, this.entryError);
-    }
     for (let i = 0; i < 5 && !(this.entry || this.entryError); i++) {
       await new Promise((r) => setTimeout(r, 100 * Math.pow(2, i)));
     }
     if (this.entryError) {
-      return renderError(req, this.entryError);
+      throw this.entryError;
     }
     if (!this.entry) {
       throw httpError(503, `Vite environment "${this.name}" is unavailable`);
     }
-    try {
-      const entryFetch = this.entry.fetch || this.entry.default?.fetch;
-      if (!entryFetch) {
-        throw httpError(500, `No fetch handler exported from ${this.entryPath}`);
-      }
-      return await entryFetch(req, init);
-    } catch (error) {
-      return renderError(req, error);
+    const entryFetch = this.entry.fetch || this.entry.default?.fetch;
+    if (!entryFetch) {
+      throw httpError(500, `No fetch handler exported from ${this.entryPath}`);
     }
+    return entryFetch(req, init);
   }
 }
 
@@ -148,13 +144,17 @@ globalThis.__transform_html__ = async function (html) {
 
 // ----- Exports (env-runner AppEntry) -----
 
-export function fetch(req) {
+export async function fetch(req) {
   const viteEnv = req?.headers.get("x-vite-env") || "nitro";
   const env = envs[viteEnv];
   if (!env) {
     return renderError(req, httpError(500, `Unknown vite environment "${viteEnv}"`));
   }
-  return env.fetch(req);
+  try {
+    return await env.fetch(req);
+  } catch (error) {
+    return renderError(req, error);
+  }
 }
 
 export function upgrade(context) {

test/vite/app-fixture/app/entry-server.ts

@@ -1,8 +1,12 @@
+import { HTTPError } from "h3";
 import { useStorage } from "nitro/storage";
 import { useRuntimeConfig } from "nitro/runtime-config";
 
 export default {
-  async fetch() {
+  async fetch(req: Request) {
+    if (req.url.includes("?error")) {
+      throw new HTTPError({ status: 418, headers: { "x-test": "123" } });
+    }
     const storage = useStorage();
     const config = useRuntimeConfig();
     await storage.set("test:key", "value-from-ssr");

test/vite/app.test.ts

@@ -82,6 +82,17 @@ describe("vite:app", () => {
     expect(res.status).not.toBe(200);
   });
 
+  // HTTPError thrown from the SSR entry must propagate to the nitro app so the h3
+  // error handler preserves its status and headers (consistent with production).
+  test("propagates HTTPError status and headers from the SSR entry", async () => {
+    const res = await fetch(`${serverURL}/?error`, {
+      headers: { "sec-fetch-dest": "document", accept: "text/html" },
+      redirect: "manual",
+    });
+    expect(res.status).toBe(418);
+    expect(res.headers.get("x-test")).toBe("123");
+  });
+
   // A page navigation matching only the SSR `/**` catch-all must reach the renderer.
   test("routes page navigations to the SSR catch-all renderer", async () => {
     const res = await fetch(`${serverURL}/some/nested/page`, {