TanStack Start + Sentry add-on not working

[markwoon]

Which project does this relate to?

Start

Describe the bug

Create a new TanStack Start app with Sentry add-on.
Run npm run dev.

Get: TypeError: Cannot read properties of undefined (reading 'VITE_SENTRY_DSN')

I've updated .env.local to include a valid DSN, but that doesn't make any difference.

Your Example Website or App

Steps to Reproduce the Bug or Issue

> npm create @tanstack/start@latest

> npx
> "create-start"

┌  Let's configure your TanStack Start application
│
◇  What would you like to name your project?
│  foo-sentry
│
◇  Would you like to use Tailwind CSS?
│  No
│
◇  Select toolchain
│  Biome
│
◇  What add-ons would you like for your project?
│  Sentry
│
◇  Would you like any examples?
│  none
│
◇  Initialized git repository
│
◇  Installed dependencies
│
└  Your TanStack Start app is ready in 'foo-sentry'.

Use the following commands to start your app:
% cd foo-sentry
% npm run dev

Please check the README.md for information on testing, styling, adding routes, etc.

> cd foo-sentry/
> npm run dev

> dev
> NODE_OPTIONS='--import ./instrument.server.mjs' vite dev --port 3000

file:///home/markwoon/Dev/foo-sentry/instrument.server.mjs:3
  dsn: import.meta.env.VITE_SENTRY_DSN,
                       ^

TypeError: Cannot read properties of undefined (reading 'VITE_SENTRY_DSN')
    at file:///home/user/foo-sentry/instrument.server.mjs:3:24
    at ModuleJob.run (node:internal/modules/esm/module_job:377:25)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:689:26)
    at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:96:9)

Expected behavior

I expect the app to start up. But it doesn't.

Screenshots or Videos

No response

Platform

• Router / Start Version: 1.132.0
• OS: Linux
• Bundler: vite
• Bundler Version: 7.1.7

Additional context

No response

[wilbertliu]

That happened to me as well.

Since instrument.server.mjs runs outside Vite's build/transform step, import.meta.env is not available there.

What works for me is to change import.meta.env.VITE_SENTRY_DSN to process.env.VITE_SENTRY_DSN. Make sure you put VITE_SENTRY_DSN on .env and use dotenv on instrument.server.mjs.

Here is my final instrument.server.mjs:

import * as Sentry from '@sentry/tanstackstart-react';
import 'dotenv/config';
Sentry.init({
  dsn: process.env.VITE_SENTRY_DSN,
  // Adds request headers and IP for users, for more info visit:
  // https://docs.sentry.io/platforms/javascript/guides/tanstackstart-react/configuration/options/#sendDefaultPii
  sendDefaultPii: true,
});

Hope that helps.

[MichaelFrieze]

import * as Sentry from '@sentry/tanstackstart-react';
import 'dotenv/config';
Sentry.init({...});

If you are using .env.local, you might need to add this:

import dotenv from 'dotenv'
dotenv.config({ path: '.env.local' })