Describe the bug

Optional chaining is removed during Vite 8 production bundling when accessing a property from an imported Svelte $state.

Example:

export const app = $state({ user: null })
Used as:

import * as h from './state.svelte.js'

h.app?.user?.name ?? 'ok'

Expected result:
The expression evaluates safely to "ok".

Actual result:
The console log throws:

TypeError: Cannot read properties of null (reading 'name')

It appears that the optional chaining is removed during bundling:

h.app?.user?.name
becomes

h.app.user.name

Reproduction

https://stackblitz.com/edit/vitejs-vite-bxd2fnks

Steps to reproduce

1. Open the StackBlitz link — preview shows "Result : ok" (dev mode, works fine)
2. In the StackBlitz terminal: Ctrl+C to stop the dev server
3. Run: npm run build
4. Run: npm run preview
5. The preview now shows the production build → check browser console for TypeError

project.zip

System Info

npmPackages:
    @sveltejs/vite-plugin-svelte: ^7.0.0 => 7.0.0
    svelte: ^5.53.0 => 5.53.12
    vite: ^8.0.0 => 8.0.0

  System:
    OS: Windows 11 10.0.26200
    CPU: (8) x64 AMD Ryzen 7 3700U with Radeon Vega Mobile Gfx
    Memory: 2.42 GB / 17.94 GB
  Binaries:
    Node: 24.11.1 - C:\Program Files\nodejs\node.EXE
    npm: 11.6.4 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Chrome: 145.0.7632.161

Used Package Manager

npm

Logs

There is not error in build

npm run build

vite8-svelte5-optional-chaining-bug@1.0.0 build
vite build

(node:28) ExperimentalWarning: WASI is an experimental feature and might change at any time
(Use node --trace-warnings ... to show where the warning was created)
(node:28) ExperimentalWarning: WASI is an experimental feature and might change at any time
(Use node --trace-warnings ... to show where the warning was created)
(node:28) ExperimentalWarning: WASI is an experimental feature and might change at any time
(Use node --trace-warnings ... to show where the warning was created)
vite v8.0.0 building client environment for production...
✓ 109 modules transformed.
computing gzip size...
dist/index.html 0.34 kB │ gzip: 0.27 kB
dist/assets/index-CMMK_kCj.js 91.59 kB │ gzip: 23.84 kB

✓ built in 2.41s

~/projects/vitejs-vite-bxd2fnks 13s
❯

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.