Start: Invalid lazy handler result and v1.121.0 migration failing

[heystevegray]

Which project does this relate to?

Start

Describe the bug

• The bug
• Trying to migrate
• Not migrating at this time
• New project

The bug

A few days ago I couldn't start my dev server anymore with npm run dev.

npm run dev

> app@1.0.0 dev
> vinxi dev --host

vinxi v0.5.7
Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './config' is not defined by "exports" in /Users/me/app/node_modules/@tanstack/react-start/package.json imported from /Users/me/app/app.config.timestamp_1750004498370.js
    at exportsNotFound (node:internal/modules/esm/resolve:296:10)
    at packageExportsResolve (node:internal/modules/esm/resolve:643:9)
    at packageResolve (node:internal/modules/esm/resolve:823:14)
    at moduleResolve (node:internal/modules/esm/resolve:907:18)
    at defaultResolve (node:internal/modules/esm/resolve:1037:11)
    at ModuleLoader.defaultResolve (node:internal/modules/esm/loader:650:12)
    at #cachedDefaultResolve (node:internal/modules/esm/loader:599:25)
    at ModuleLoader.resolve (node:internal/modules/esm/loader:582:38)
    at ModuleLoader.getModuleJobForImport (node:internal/modules/esm/loader:241:38)
    at ModuleJob._link (node:internal/modules/esm/module_job:132:49) {
  code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}

 ERROR  Cannot read properties of undefined (reading 'config')                                                                             12:21:38 PM

    at Object.run (node_modules/vinxi/bin/cli.mjs:79:9)
    at async runCommand (node_modules/citty/dist/index.mjs:316:16)
    at async runCommand (node_modules/citty/dist/index.mjs:307:11)
    at async runMain (node_modules/citty/dist/index.mjs:445:7) 



 ERROR  Cannot read properties of undefined (reading 'config')                                                                             12:21:38 PM

My package.json looked like this:

{
  "@tanstack/react-router": "^1.120.5",
  "@tanstack/react-start": "^1.120.5",
  "vinxi": "^0.5.6",
}

Trying to migrate

I then found this migration guide for v1.121.0 in Start BETA - Tracking: #2863 (comment). In a new branch I followed these steps. Then I ran npm run build and npm run start and I see this error:

TypeError: Invalid lazy handler result. It should be a function: at file:///Users/me/app/.output/server/index.mjs:1473:17

My localhost shows this in the browser:

{
  "error": true,
  "url": "http://[::]:3000/",
  "statusCode": 500,
  "statusMessage": "Server Error",
  "message": "Server Error"
}

And my terminal shows this:

 npm run start

> app@1.0.0 start
> node .output/server/index.mjs

Listening on http://[::]:3000
[request error] [unhandled] [GET] http://[::]:3000/
 TypeError: Invalid lazy handler result. It should be a function:
    at file:///Users/me/app/.output/server/index.mjs:1473:17
    at async Object.handler (file:///Users/me/app/.output/server/index.mjs:1557:19)
    at async Server.toNodeHandle (file:///Users/me/app/.output/server/index.mjs:1828:7) {
  cause: TypeError: Invalid lazy handler result. It should be a function:
      at file:///Users/me/app/.output/server/index.mjs:1473:17
      at async Object.handler (file:///Users/me/app/.output/server/index.mjs:1557:19)
      at async Server.toNodeHandle (file:///Users/me/app/.output/server/index.mjs:1828:7),
  statusCode: 500,
  fatal: false,
  unhandled: true,
  statusMessage: undefined,
  data: undefined
}
[unhandledRejection] Error: Invalid environment variables
    at onValidationError (file:///Users/me/app/.output/server/node_modules/@t3-oss/env-core/dist/src-Cq4nGjdj.js:53:9)
    at createEnv (file:///Users/me/app/.output/server/node_modules/@t3-oss/env-core/dist/src-Cq4nGjdj.js:58:28)
    at file:///Users/me/app/.output/server/chunks/_/ssr.mjs:2136:15
    at file:///Users/me/app/.output/server/chunks/_/ssr.mjs:5818:3
    at ModuleJob.run (node:internal/modules/esm/module_job:268:25)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:543:26)
    at async Object.handler (file:///Users/me/app/.output/server/index.mjs:1557:19)
    at async Server.toNodeHandle (file:///Users/me/app/.output/server/index.mjs:1828:7)
[request error] [unhandled] [GET] http://[::]:3000/favicon.ico
 TypeError: Invalid lazy handler result. It should be a function:
    at file:///Users/me/app/.output/server/index.mjs:1473:17
    at async Object.handler (file:///Users/me/app/.output/server/index.mjs:1557:19)
    at async Server.toNodeHandle (file:///Users/me/app/.output/server/index.mjs:1828:7) {
  cause: TypeError: Invalid lazy handler result. It should be a function:
      at file:///Users/me/app/.output/server/index.mjs:1473:17
      at async Object.handler (file:///Users/me/app/.output/server/index.mjs:1557:19)
      at async Server.toNodeHandle (file:///Users/me/app/.output/server/index.mjs:1828:7),
  statusCode: 500,
  fatal: false,
  unhandled: true,
  statusMessage: undefined,
  data: undefined
}

Here is my vite.config.ts file. I'm trying to use https://env.t3.gg/docs/core for environment variable safety, thats why you see these lines:

import 'dotenv/config'
import './src/env'

My vite.config.ts file:

import { tanstackStart } from '@tanstack/react-start/plugin/vite'
import { defineConfig } from 'vite'
import topLevelAwait from 'vite-plugin-top-level-await'
import tsConfigPaths from 'vite-tsconfig-paths'
import 'dotenv/config'
import './src/env'

export default defineConfig({
  server: {
    port: 3000,
  },
  plugins: [
    tsConfigPaths({
      projects: ['./tsconfig.json'],
    }),
    tanstackStart({
      target: 'node-server',
    }),
    topLevelAwait(),
  ],
})

Not migrating at this time

I also attempted the "pinning" suggestion at the bottom of this link: #2863 (comment)

npx create-start-app@latest pin-versions
10 packages updated.

Remove your node_modules directory and package lock file and re-install.

This updated the following packages in my package.json file

{
  "@tanstack/react-router": "1.120.5",
  "@tanstack/react-router-devtools": "1.120.5",
  "@tanstack/react-start": "1.120.5",
  "@tanstack/react-start-client": "1.120.5",
  "@tanstack/react-start-config": "1.120.5",
  "@tanstack/react-start-plugin": "1.120.5",
  "@tanstack/react-start-server": "1.120.5",
  "@tanstack/router-generator": "1.120.5",
  "@tanstack/router-plugin": "1.120.5",
  "@tanstack/start-server-core": "1.120.5",
}

I removed node_modules and package-lock.json, then ran npm i again. But then I see this error:

No matching version found for @tanstack/react-start-plugin@1.120.5

npm i

npm error code ETARGET
npm error notarget No matching version found for @tanstack/react-start-plugin@1.120.5.
npm error notarget In most cases you or one of your dependencies are requesting
npm error notarget a package version that doesn't exist.
npm error A complete log of this run can be found in: /Users/me/.npm/_logs/2025-06-15T17_20_33_118Z-debug-0.log

New project

I followed the steps here to build a project from scratch and I can successfully run npm run build and npm run start with these scripts:

"scripts": {
  "dev": "vite dev",
  "build": "vite build",
  "start": "node .output/server/index.mjs"
}

My working example repo is here: https://github.com/heystevegray/tanstack-start-beta-bug

I'm not sure why a new project seems to work but mine cannot start.

Your Example Website or App

https://github.com/heystevegray/tanstack-start-beta-bug

Steps to Reproduce the Bug or Issue

1. Follow this migration guide: Start BETA - Tracking #2863 (comment) with an older version of tanstack start

   {
     "@tanstack/react-router": "^1.120.5",
     "@tanstack/react-start": "^1.120.5",
     "vinxi": "^0.5.6",
   }

2. Run npm run build
3. Run npm run start
4. I see this in the terminal:

   TypeError: Invalid lazy handler result. It should be a function:
   at file:///Users/me/app/.output/server/index.mjs:1473:17

Expected behavior

I expect after following the migration guide here #2863 (comment) that I can build and start my project with:

"start": "node .output/server/index.mjs"

Screenshots or Videos

No response

Platform

• OS: macOS
• Browser: Arc
• Version: Arc 1.99.0 (64212)

Additional context

No response

[schiller-manuel]

can you please share a failing reproducer?

[heystevegray]

@schiller-manuel Here is a failing reproducer of he "pin-versions" error from the bottom of this guide #2863 (comment). The example is on a branch called pinning: https://github.com/heystevegray/tanstack-start-beta-bug/tree/pinning

Here are the commits I made following the migration guide: heystevegray/tanstack-start-beta-bug@main...pinning

Here is an old tanstack start starting point: heystevegray/tanstack-start-beta-bug@3c51754

1. Pull the repo and cd to the project

   git clone git@github.com:heystevegray/tanstack-start-beta-bug.git
   cd tanstack-start-beta-bug

2. Checkout the pinning branch

   git checkout pinning

3. Run npm i and it will fail

   npm i
   npm error code ETARGET
   npm error notarget No matching version found for @tanstack/react-router-devtools@1.121.13.
   npm error notarget In most cases you or one of your dependencies are requesting
   npm error notarget a package version that doesn't exist.
   npm error A complete log of this run can be found in: /Users/me/.npm/_logs/2025-06-15T19_57_19_616Z-debug-0.log

I'm still trying to make a failing reproducer for the TypeError: Invalid lazy handler result. It should be a function: issue.

[schiller-manuel]

that version does indeed not exist. see https://www.npmjs.com/package/@tanstack/react-router-devtools?activeTab=versions

[schiller-manuel]

please check if #4432 is showing the same issue as you have with the "invalid lazy handler"

[heystevegray]

that version does indeed not exist. see https://www.npmjs.com/package/@tanstack/react-router-devtools?activeTab=versions

I see, it seems the helper from the bottom of this guide #2863 (comment) (npx create-start-app@latest pin-versions) is behaving in different ways.

1. In my demo repository Start: Invalid lazy handler result and v1.121.0 migration failing #4431 (comment) it added @tanstack/react-router-devtools@1.121.13 to the package.json which doesn't exist.

2. In my project repo I tried the same helper and it added @tanstack/react-start-plugin@1.120.5 to the package.json which doesn't exist. https://www.npmjs.com/package/@tanstack/react-start-plugin?activeTab=versions

   

   npm i
   npm error code ETARGET
   npm error notarget No matching version found for @tanstack/react-start-plugin@1.120.5.
   npm error notarget In most cases you or one of your dependencies are requesting
   npm error notarget a package version that doesn't exist.
   npm error A complete log of this run can be found in: /Users/me/.npm/_logs/2025-06-15T20_33_39_932Z-debug

If I manually install this version I can get my dev server running

npm i @tanstack/react-start-plugin@1.120.17

But when I open localhost in the browser I see an issue with the loader data and the app never loads

Error in renderToPipeableStream: TypeError: Cannot destructure property 'defaultOpen' of 'Route.useLoaderData(...)' as it is undefined.

Error in renderToPipeableStream: TypeError: Cannot destructure property 'defaultOpen' of 'Route.useLoaderData(...)' as it is undefined.
    at RootDocument (/Users/me/app/app/routes/__root.tsx:88:11)
    at renderWithHooks (/Users/me/app/node_modules/react-dom/cjs/react-dom-server.node.development.js:5724:16)
    at renderIndeterminateComponent (/Users/me/app/node_modules/react-dom/cjs/react-dom-server.node.development.js:5798:15)
    at renderElement (/Users/me/app/node_modules/react-dom/cjs/react-dom-server.node.development.js:6023:7)
    at renderNodeDestructiveImpl (/Users/me/app/node_modules/react-dom/cjs/react-dom-server.node.development.js:6181:11)
    at renderNodeDestructive (/Users/me/app/node_modules/react-dom/cjs/react-dom-server.node.development.js:6153:14)
    at renderIndeterminateComponent (/Users/me/app/node_modules/react-dom/cjs/react-dom-server.node.development.js:5852:7)
    at renderElement (/Users/me/app/node_modules/react-dom/cjs/react-dom-server.node.development.js:6023:7)
    at renderNodeDestructiveImpl (/Users/me/app/node_modules/react-dom/cjs/react-dom-server.node.development.js:6181:11)
    at renderNodeDestructive (/Users/me/app/node_modules/react-dom/cjs/react-dom-server.node.development.js:6153:14) undefined

[heystevegray]

please check if #4432 is showing the same issue as you have with the "invalid lazy handler"

From #4432

Note: this works ok in dev. It is only triggered by building and running a server (tested with node-server and aws-lambda targets).

Yes this appears to be the same issue I'm seeing. I can run ok in dev, but I cannot build and start (Run node .output/server/index.mjs). I was targeting node-server.

[schiller-manuel]

so you also have tsr.srcDirectory set to . ?

[heystevegray]

Oh sorry, no I do not have tsr.srcDirectory set to . in vite.config.ts. I just set the target: 'node-server'

// vite.config.ts
import { tanstackStart } from '@tanstack/react-start/plugin/vite'
import { defineConfig } from 'vite'
import topLevelAwait from 'vite-plugin-top-level-await'
import tsConfigPaths from 'vite-tsconfig-paths'
import 'dotenv/config'
import './src/env'

export default defineConfig({
  server: {
    port: 3000,
  },
  plugins: [
    tsConfigPaths({
      projects: ['./tsconfig.json'],
    }),
    tanstackStart({
      target: 'node-server', // No tsr.srcDirectory
    }),
    topLevelAwait(),
  ],
})

I tried to set the value and and build and this happened:

tanstackStart({
    target: 'node-server',
    tsr: {
        srcDirectory: '.',
    },
})

Failed to build

Error: ENOENT: no such file or directory, scandir '/Users/me/app/routes'

and this

[vite]: Rollup failed to resolve import "/Users/me/app/router" from "/~start/default-client-entry.tsx".

npm run build

> app@1.0.0 build
> vite build && tsc --noEmit

vite v6.3.5 building for production...
Error: ENOENT: no such file or directory, scandir '/Users/me/app/routes'
    at file:///Users/me/app/node_modules/@tanstack/router-generator/dist/esm/generator.js:142:19
    at async generate (file:///Users/me/app/node_modules/@tanstack/router-plugin/dist/esm/core/router-generator-plugin.js:34:7)
    at async Object.buildStart (file:///Users/me/app/node_modules/@tanstack/router-plugin/dist/esm/core/router-generator-plugin.js:61:9)
    at async Promise.all (index 2)
    at async PluginDriver.hookParallel (file:///Users/me/app/node_modules/rollup/dist/es/shared/node-entry.js:22166:9)
    at async file:///Users/me/app/node_modules/rollup/dist/es/shared/node-entry.js:23130:13
    at async catchUnfinishedHookActions (file:///Users/me/app/node_modules/rollup/dist/es/shared/node-entry.js:22608:16)
    at async rollupInternal (file:///Users/me/app/node_modules/rollup/dist/es/shared/node-entry.js:23127:5)
    at async buildEnvironment (file:///Users/me/app/node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:46206:14)
    at async Object.buildApp (file:///Users/me/app/node_modules/@tanstack/start-plugin-core/dist/esm/nitro-plugin/plugin.js:45:15)
✓ 2 modules transformed.
✗ Build failed in 16ms
error during build:
[vite]: Rollup failed to resolve import "/Users/me/app/router" from "/~start/default-client-entry.tsx".
This is most likely unintended because it can break your application at runtime.
If you do want to externalize this module explicitly add it to
`build.rollupOptions.external`
    at viteLog (file:///Users/me/app/node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:46345:15)
    at file:///Users/me/app/node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:46403:18
    at onwarn (file:///Users/me/app/node_modules/@vitejs/plugin-react/dist/index.mjs:104:9)
    at file:///Users/me/app/node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:46401:7
    at onRollupLog (file:///Users/me/app/node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:46393:5)
    at onLog (file:///Users/me/app/node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:46043:7)
    at file:///Users/me/app/node_modules/rollup/dist/es/shared/node-entry.js:20772:32
    at Object.logger [as onLog] (file:///Users/me/app/node_modules/rollup/dist/es/shared/node-entry.js:22651:9)
    at ModuleLoader.handleInvalidResolvedId (file:///Users/me/app/node_modules/rollup/dist/es/shared/node-entry.js:21398:26)
    at file:///Users/me/app/node_modules/rollup/dist/es/shared/node-entry.js:21356:26

This migration guide #2863 (comment) said to delete the client entry files if you didn't customize them. I did not customize them and deleted them.

Delete src/client.tsx and src/ssr.tsx If you did NOT customize your src/client.tsx and src/ssr.tsx files, then you can delete them. - Source

[MathieuDoyon]

After I made sure to remove all Vinxi-related code from my workspace, it started working. A small change from the renamed file ssr.tsx to server.tsx allowed the API routes to function well.

You have modified your client.tsx file; make sure to remove all Vinxi references.

Remove all /// <reference types="vinxi/types/client" />

Change the import from import { getWebRequest } from "vinxi/http"; to import { getWebRequest } from "@tanstack/react-start/server"; in your server.ts file if you use it.

You need to remove all imports under the Vinxi namespace: import ... from "vinxi/...." and fix the API routes.

- import { createAPIFileRoute } from "@tanstack/react-start/api";
+ import { createServerFileRoute } from "@tanstack/react-start/server";

#2863 (comment)

[heystevegray]

@MathieuDoyon Here are some updates but I'm still seeing this error:

TypeError: Invalid lazy handler result. It should be a function: at file:///Users/me/app/.output/server/index.mjs:1473:17

1. I've uninstalled vinxi and didn't find any other instances of it.

2. I've deleted client.tsx as a part of this migration guide Start BETA - Tracking #2863 (comment).

3. My getWebRequest is coming from here:

   import { getWebRequest } from '@tanstack/react-start/server'

4. I've updated all the api routes to use ServerRoutes:

   import { createServerFileRoute } from '@tanstack/react-start/server'

5. /src/sever.tsx seemed optional if you use it, but as a test I tried to add it and still no luck

   // src/server.tsx
   import { createStartHandler, defaultStreamHandler } from '@tanstack/react-start/server'
   
   import { createRouter } from './router'
   
   export default createStartHandler({
     createRouter,
   })(defaultStreamHandler)

[Crsk]

Mmm there seems to be an issue with today's released versions 1.121.17 and 1.121.18, i noticed node_module packages depending on these versions don't have a dist folder causing not found errors here and there. My problems started to happen after deleted the lock file, new generated one depends on .17 or 18 even though i install packages with -E 1.121.16

[djgrant]

@heystevegray this workaround might help with your "Invalid lazy handler" error #4432 (comment)