Try importing custom-backend-task definitions directly to avoid bundling issues.

examples/pokedex/adapter.mjs

@@ -1,4 +1,5 @@
-import fs from "fs";
+import * as fs from "fs";
+import * as path from "path";
 
 export default async function run({
   renderFunctionFilePath,
@@ -19,11 +20,6 @@ export default async function run({
     renderFunctionFilePath,
     "./functions/server-render/elm-pages-cli.cjs"
   );
-  fs.copyFileSync(portsFilePath, "./functions/render/custom-backend-task.mjs");
-  fs.copyFileSync(
-    portsFilePath,
-    "./functions/server-render/custom-backend-task.mjs"
-  );
 
   fs.writeFileSync(
     "./functions/render/index.mjs",
@@ -108,6 +104,7 @@ import * as busboy from "busboy";
 import { fileURLToPath } from "url";
 import * as renderer from "../../../../generator/src/render.js";
 import * as preRenderHtml from "../../../../generator/src/pre-render-html.js";
+import * as customBackendTask from "${path.resolve(portsFilePath)}";
 const htmlTemplate = ${JSON.stringify(htmlTemplate)};
 
 ${
@@ -128,7 +125,6 @@ export const handler = render;`
 async function render(event, context) {
   const requestTime = new Date();
   console.log(JSON.stringify(event));
-  const compiledPortsFile = "./functions/server-render/custom-backend-task.mjs";
 
   try {
     const basePath = "/";
@@ -136,7 +132,7 @@ async function render(event, context) {
     const addWatcher = () => {};
 
     const renderResult = await renderer.render(
-      compiledPortsFile,
+      customBackendTask,
       basePath,
       (await import("./elm-pages-cli.cjs")).default,
       mode,

generator/src/render-worker.js

@@ -4,12 +4,13 @@ import * as fs from "./dir-helpers.js";
 import { readFileSync, writeFileSync } from "fs";
 import { stat } from "fs/promises";
 import { parentPort, threadId, workerData } from "worker_threads";
+import * as url from "url";
 
 async function run({ mode, pathname, serverRequest, portsFilePath }) {
   console.time(`${threadId} ${pathname}`);
   try {
     const renderResult = await renderer.render(
-      portsFilePath,
+      await import(url.pathToFileURL(path.resolve(portsFilePath)).href),
       workerData.basePath,
       await requireElm(mode),
       mode,

generator/src/request-cache.js

@@ -10,7 +10,7 @@ const defaultHttpCachePath = "./.elm-pages/http-cache";
 /**
  * @param {string} mode
  * @param {{url: string;headers: {[x: string]: string;};method: string;body: Body;}} rawRequest
- * @param {string} portsFile
+ * @param {Record<string, unknown>} portsFile
  * @param {boolean} hasFsAccess
  * @returns {Promise<Response>}
  */
@@ -27,16 +27,12 @@ export function lookupOrPerform(
   return new Promise(async (resolve, reject) => {
     const request = toRequest(rawRequest);
 
-    let portBackendTask = {};
+    let portBackendTask = portsFile;
     let portBackendTaskImportError = null;
     try {
       if (portsFile === undefined) {
         throw "missing";
       }
-      const portBackendTaskPath = path.resolve(portsFile);
-      // On Windows, we need cannot use paths directly and instead must use a file:// URL.
-      // portBackendTask = await require(url.pathToFileURL(portBackendTaskPath).href);
-      portBackendTask = await import(portBackendTaskPath);
     } catch (e) {
       portBackendTaskImportError = e;
     }