Reproduce dynamic import failure from redirected fallback module

samples/module-fallback-redirect/README.md

@@ -0,0 +1,45 @@
+# Module Fallback Redirect Reproduction
+
+This reproduces a V2 module fallback failure involving a redirected module that
+performs a dynamic import. It does not use Vite or Workers SDK.
+
+Start the fallback service from the repository root:
+
+```sh
+node samples/module-fallback-redirect/fallback.mjs
+```
+
+In another terminal, start Workerd:
+
+```sh
+npx workerd@latest serve samples/module-fallback-redirect/config.capnp --experimental
+```
+
+Then invoke the Worker:
+
+```sh
+curl http://127.0.0.1:8080
+```
+
+The Worker imports two bare dependencies. The fallback service redirects both
+to canonical `file:///project/node_modules/...` URLs. The `/project` path is a
+logical, portable stand-in for a resolved project path; this reproduction does
+not read the host filesystem.
+
+- `static-test-dependency` statically imports `./value.mjs`.
+- `dynamic-test-dependency` dynamically imports `./value.mjs` when `load()` is
+  called.
+
+If both imports succeeded, Workerd would log:
+
+```text
+static import: loaded
+dynamic import: loaded
+```
+
+Instead, the static import succeeds, but the dynamic import returns HTTP 500
+with:
+
+```text
+Referring module not found in the registry: file:///project/node_modules/dynamic-test-dependency/index.mjs
+```

samples/module-fallback-redirect/config.capnp

@@ -0,0 +1,19 @@
+using Workerd = import "/workerd/workerd.capnp";
+
+const config :Workerd.Config = (
+  services = [
+    (name = "main", worker = .worker),
+  ],
+  sockets = [
+    (name = "http", address = "127.0.0.1:8080", http = (), service = "main"),
+  ],
+);
+
+const worker :Workerd.Worker = (
+  modules = [
+    (name = "worker.js", esModule = embed "worker.js"),
+  ],
+  compatibilityDate = "2026-08-03",
+  compatibilityFlags = ["new_module_registry"],
+  moduleFallback = "127.0.0.1:8888",
+);

samples/module-fallback-redirect/fallback.mjs

@@ -0,0 +1,76 @@
+// Copyright (c) 2026 Cloudflare, Inc.
+// Licensed under the Apache 2.0 license found in the LICENSE file or at:
+//     https://opensource.org/licenses/Apache-2.0
+
+import { createServer } from 'node:http';
+
+function sendJson(response, value) {
+  response.writeHead(200, { 'content-type': 'application/json' });
+  response.end(JSON.stringify(value));
+}
+
+createServer(async (request, response) => {
+  let body = '';
+  for await (const chunk of request) {
+    body += chunk;
+  }
+
+  const resolution = JSON.parse(body);
+  console.log(resolution);
+
+  switch (resolution.specifier) {
+    case 'file:///bundle/static-test-dependency':
+      response.writeHead(301, {
+        location:
+          'file:///project/node_modules/static-test-dependency/index.mjs',
+      });
+      response.end();
+      return;
+    case 'file:///project/node_modules/static-test-dependency/index.mjs':
+      sendJson(response, {
+        esModule: [
+          'import { value } from "./value.mjs";',
+          'export { value };',
+        ].join('\n'),
+      });
+      return;
+    case 'file:///bundle/value.mjs':
+      response.writeHead(301, {
+        location:
+          'file:///project/node_modules/static-test-dependency/value.mjs',
+      });
+      response.end();
+      return;
+    case 'file:///project/node_modules/static-test-dependency/value.mjs':
+      sendJson(response, {
+        esModule: 'export const value = "loaded";',
+      });
+      return;
+    case 'file:///bundle/dynamic-test-dependency':
+      response.writeHead(301, {
+        location:
+          'file:///project/node_modules/dynamic-test-dependency/index.mjs',
+      });
+      response.end();
+      return;
+    case 'file:///project/node_modules/dynamic-test-dependency/index.mjs':
+      sendJson(response, {
+        esModule: [
+          'export async function load() {',
+          '  return await import("./value.mjs");',
+          '}',
+        ].join('\n'),
+      });
+      return;
+    case 'file:///project/node_modules/dynamic-test-dependency/value.mjs':
+      sendJson(response, {
+        esModule: 'export const value = "loaded";',
+      });
+      return;
+    default:
+      response.writeHead(404);
+      response.end();
+  }
+}).listen(8888, '127.0.0.1', () => {
+  console.log('Fallback service listening on http://127.0.0.1:8888');
+});

samples/module-fallback-redirect/worker.js

@@ -0,0 +1,15 @@
+// Copyright (c) 2026 Cloudflare, Inc.
+// Licensed under the Apache 2.0 license found in the LICENSE file or at:
+//     https://opensource.org/licenses/Apache-2.0
+
+import { load } from 'dynamic-test-dependency';
+import { value as staticValue } from 'static-test-dependency';
+
+export default {
+  async fetch() {
+    console.log('static import:', staticValue);
+    const dynamicModule = await load();
+    console.log('dynamic import:', dynamicModule.value);
+    return new Response('ok');
+  },
+};