SPA mode not working with vite-plugin-mkcert

[hungtcs]

Reproduction

pnpx create-react-router@latest my-react-router-app
cd my-react-router-app
pnpm update --latest
pnpm add -D vite-plugin-mkcert

import { reactRouter } from "@react-router/dev/vite";
import tailwindcss from "@tailwindcss/vite";
import { defineConfig } from "vite";
import mkcert from "vite-plugin-mkcert";

export default defineConfig({
  plugins: [tailwindcss(), reactRouter(), mkcert()],
  resolve: {
    tsconfigPaths: true,
  },
});

import type { Config } from "@react-router/dev/config";

export default {
  // Config options...
  // Server-side render by default, to enable SPA mode set this to `false`
  ssr: false,
} satisfies Config;

And then run pnpm run build

$ react-router build
Using Vite Environment API
vite v8.1.2 building client environment for production...
✓ 50 modules transformed.
computing gzip size...
dist/client/.vite/manifest.json                1.51 kB │ gzip:  0.42 kB
dist/client/assets/root-C9Wmugyj.css           4.77 kB │ gzip:  1.60 kB
dist/client/assets/home-B8i4DWWp.js            0.26 kB │ gzip:  0.21 kB
dist/client/assets/root-CuXVlrA-.js           11.40 kB │ gzip:  4.62 kB
dist/client/assets/components-CNU9cdDZ.js     33.36 kB │ gzip: 11.73 kB
dist/client/assets/jsx-runtime-DvHXw_r7.js    83.80 kB │ gzip: 27.90 kB
dist/client/assets/entry.client-Ca3bqa5R.js  185.90 kB │ gzip: 58.64 kB

✓ built in 131ms
vite v8.1.2 building ssr environment for production...
✓ 6 modules transformed.

✓ 1 asset cleaned from React Router server build.
dist/server/assets/server-build-C9Wmugyj.css

computing gzip size...
dist/server/.vite/manifest.json               0.22 kB │ gzip: 0.15 kB
dist/server/assets/server-build-C9Wmugyj.css  4.77 kB │ gzip: 1.60 kB
dist/server/index.js                          6.59 kB │ gzip: 2.32 kB

✓ built in 44ms
Error: Prerender: Request failed for /: Protocol "https:" not supported. Expected "http:"
    at defaultHandleError (file:///Users/hungtcs/Temp/my-react-router-app/node_modules/.pnpm/@react-router+dev@8.1.0_@react-router+serve@8.1.0_react-router@8.1.0_react-dom@19.2.7_r_e29186856b10882a1078faa579f9c032/node_modules/@react-router/dev/dist/vite.js:887:8)
    at attempt (file:///Users/hungtcs/Temp/my-react-router-app/node_modules/.pnpm/@react-router+dev@8.1.0_@react-router+serve@8.1.0_react-router@8.1.0_react-dom@19.2.7_r_e29186856b10882a1078faa579f9c032/node_modules/@react-router/dev/dist/vite.js:835:11)
    at process.processTicksAndRejections (node:internal/process/task_queues:104:5)
    at async prerender (file:///Users/hungtcs/Temp/my-react-router-app/node_modules/.pnpm/@react-router+dev@8.1.0_@react-router+serve@8.1.0_react-router@8.1.0_react-dom@19.2.7_r_e29186856b10882a1078faa579f9c032/node_modules/@react-router/dev/dist/vite.js:842:64)
    at async default.concurrency.concurrency (file:///Users/hungtcs/Temp/my-react-router-app/node_modules/.pnpm/@react-router+dev@8.1.0_@react-router+serve@8.1.0_react-router@8.1.0_react-dom@19.2.7_r_e29186856b10882a1078faa579f9c032/node_modules/@react-router/dev/dist/vite.js:859:9)
    at async file:///Users/hungtcs/Temp/my-react-router-app/node_modules/.pnpm/p-map@7.0.5/node_modules/p-map/index.js:121:20
[ELIFECYCLE] Command failed with exit code 1.

System Info

System:
  OS: macOS 26.5.1
  CPU: (8) arm64 Apple M3
  Memory: 179.78 MB / 24.00 GB
  Shell: 5.9 - /bin/zsh
Binaries:
  Node: 24.16.0 - /Users/hungtcs/.local/state/fnm_multishells/99313_1782956972899/bin/node
  Yarn: 1.22.22 - /opt/homebrew/bin/yarn
  npm: 11.13.0 - /Users/hungtcs/.local/state/fnm_multishells/99313_1782956972899/bin/npm
  pnpm: 11.5.3 - /opt/homebrew/bin/pnpm
  bun: 1.3.14 - /opt/homebrew/bin/bun
  Deno: 2.8.3 - /Users/hungtcs/.deno/bin/deno
Browsers:
  Chrome: 149.0.7827.201
  Firefox: 149.0
  Safari: 26.5
npmPackages:
  @react-router/dev: 8.1.0 => 8.1.0 
  @react-router/fs-routes: ^8.1.0 => 8.1.0 
  @react-router/node: 8.1.0 => 8.1.0 
  @react-router/serve: 8.1.0 => 8.1.0 
  react-router: 8.1.0 => 8.1.0 
  vite: ^8.1.2 => 8.1.2

Used Package Manager

pnpm

Expected Behavior

Built without any errors

Actual Behavior

Error: Prerender: Request failed for /: Protocol "https:" not supported. Expected "http:"