SvelteKit Vite plugin crash with remote functions and vitest 4

Describe the bug

When:

• You are running Vitest 4
• you have a test that runs in jsdom mode (not 100% sure this is necessary to reproduce)
• the test imports a component
• that component imports a remote function
• that remote function imports (directly or indirectly) the pg package

then the test will fail to run with the logs below. Looks like some issue with the export map conditions?

Same code works fine on Vitest 3.

Reproduction

https://github.com/dimfeld/vitest4-remotefunctions

pnpm install && pnpm test

Logs

~/Doc/pro/vitest4-remotefunctions ❯ pnpm test

> basic@0.0.1 test /Users/dimfeld/Documents/projects/vitest4-remotefunctions
> vitest run

The following Vite config options will be overridden by SvelteKit:
  - base

 RUN  v4.0.15 /Users/dimfeld/Documents/projects/vitest4-remotefunctions

11:05:30 PM [vite] (ssr) Error when evaluating SSR module /Users/dimfeld/Documents/projects/vitest4-remotefunctions/src/routes/query.remote.ts: require is not defined
      at eval (/Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/pg@8.16.3/node_modules/pg/lib/index.js:5:16)
      at ESModulesEvaluator.runInlinedModule (file:///Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/module-runner.js:913:161)
      at SSRCompatModuleRunner.directRequest (file:///Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/module-runner.js:1146:80)
      at SSRCompatModuleRunner.directRequest (file:///Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/chunks/config.js:15110:22)
      at SSRCompatModuleRunner.cachedRequest (file:///Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/module-runner.js:1053:73)
      at eval (/Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/pg@8.16.3/node_modules/pg/esm/index.mjs:15:31)
      at ESModulesEvaluator.runInlinedModule (file:///Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/module-runner.js:913:3)
      at SSRCompatModuleRunner.directRequest (file:///Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/module-runner.js:1146:59)
      at SSRCompatModuleRunner.directRequest (file:///Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/chunks/config.js:15110:22)
      at SSRCompatModuleRunner.cachedRequest (file:///Users/dimfeld/Documents/projects/vitest4-remotefunctions/node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/module-runner.js:1053:73)

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Failed Suites 1 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

 FAIL  src/routes/page.test.ts [ src/routes/page.test.ts ]
ReferenceError: require is not defined
  Plugin: vite-plugin-sveltekit-remote
  File: /Users/dimfeld/Documents/projects/vitest4-remotefunctions/src/routes/query.remote.ts
 ❯ eval node_modules/.pnpm/pg@8.16.3/node_modules/pg/lib/index.js:5:16
      3| const Client = require('./client')
      4| const defaults = require('./defaults')
      5| const Connection = require('./connection')
       |                ^
      6| const Result = require('./result')
      7| const utils = require('./utils')
 ❯ SSRCompatModuleRunner.directRequest node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/chunks/config.js:15110:22
 ❯ eval node_modules/.pnpm/pg@8.16.3/node_modules/pg/esm/index.mjs:15:31
 ❯ SSRCompatModuleRunner.directRequest node_modules/.pnpm/vite@7.2.6/node_modules/vite/dist/node/chunks/config.js:15110:22

System Info

System:
    OS: macOS 26.1
    CPU: (16) arm64 Apple M3 Max
    Memory: 4.91 GB / 128.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.11.1 - /opt/homebrew/opt/node@24/bin/node
    Yarn: 1.22.22 - /Users/dimfeld/Library/pnpm/yarn
    npm: 11.6.2 - /opt/homebrew/opt/node@24/bin/npm
    pnpm: 10.24.0 - /opt/homebrew/bin/pnpm
    bun: 1.3.4 - /opt/homebrew/bin/bun
    Deno: 2.5.6 - /opt/homebrew/bin/deno
    Watchman: 2025.11.10.00 - /opt/homebrew/bin/watchman
  Browsers:
    Brave Browser: 143.1.85.111
    Firefox: 134.0.1
    Safari: 26.1
  npmPackages:
    @sveltejs/adapter-auto: ^7.0.0 => 7.0.0
    @sveltejs/kit: ^2.5.27 => 2.49.1
    @sveltejs/vite-plugin-svelte: ^6.2.1 => 6.2.1
    svelte: ^5 => 5.45.6
    vite: ^7.0.0 => 7.2.6

Severity

blocking an upgrade

Additional Information

(blocking an upgrade to Vitest 4, not an upgrade of Svelte/Kit)

Clone the linked reproduction, inspect src/routes/query.remote.ts and src/routes/page.test.ts, then run pnpm install && pnpm test with Vitest 4. Start at the vite-plugin-sveltekit-remote failure and the pg import path shown in the logs. Done means the test suite runs without the require is not defined error.