Pre-rendering hangs the build process

[inssein]

I'm using React Router as a...

framework

Reproduction

I've had a project that started with remix, which I recently migrated to react-router. Pre-rendering has been broken for me since I tried it when I moved to 7.1, and I tried it again after 7.2, and it's still broken: mnara-solutions/utiliti.dev#64

Unfortunately, the build process just hangs without any more info. I have tried providing only a single route to ensure it's not in my pre-render logic but that didn't help either.

Additionally, I had to adjust my import of renderToReadableStream from react-dom/server to react-dom/server.browser, which I don't see documented anywhere.

System Info

System:
    OS: macOS 15.3
    CPU: (14) arm64 Apple M3 Max
    Memory: 220.17 MB / 36.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.18.0 - ~/.nvm/versions/node/v20.18.0/bin/node
    npm: 10.8.2 - ~/.nvm/versions/node/v20.18.0/bin/npm
  Browsers:
    Chrome: 133.0.6943.55
    Safari: 18.3
  npmPackages:
    @react-router/cloudflare: ^7.2.0 => 7.2.0
    @react-router/dev: ^7.2.0 => 7.2.0
    react-router: ^7.2.0 => 7.2.0
    vite: ^6.0.7 => 6.1.0

Used Package Manager

npm

Expected Behavior

I expect the build command to be executed successfully.

Actual Behavior

The process hangs at the end of the build process:

➜  utiliti.dev git:(feature/pre-render) ✗ npm run build

> build
> NODE_ENV=production react-router build

vite v6.1.0 building for production...
✓ 2542 modules transformed.
Generated an empty chunk: "create".
build/client/.vite/manifest.json                               23.34 kB │ gzip:  2.33 kB
build/client/assets/stackoverflow-dark-Cx-PguMy.css             1.27 kB │ gzip:  0.60 kB
build/client/assets/tailwind-DyU7gPKC.css                      51.23 kB │ gzip:  8.94 kB
build/client/assets/create-l0sNRNKZ.js                          0.00 kB │ gzip:  0.02 kB
build/client/assets/convert-text-file-DJUzPpLu.js               0.11 kB │ gzip:  0.12 kB
build/client/assets/use-isomorphic-layout-effect-2c42DOkn.js    0.12 kB │ gzip:  0.13 kB
build/client/assets/meta-DIElYQO9.js                            0.18 kB │ gzip:  0.14 kB
build/client/assets/button-DcuqW6vU.js                          0.34 kB │ gzip:  0.27 kB
build/client/assets/number-input-DZbDzB0i.js                    0.36 kB │ gzip:  0.27 kB
build/client/assets/simple-output-BYcvYxBL.js                   0.40 kB │ gzip:  0.28 kB
build/client/assets/read-only-textarea-DET3cJ2O.js              0.43 kB │ gzip:  0.33 kB
build/client/assets/dropdown-D3yZNh9K.js                        0.52 kB │ gzip:  0.35 kB
build/client/assets/MagnifyingGlassIcon-BsCVPdbu.js             0.54 kB │ gzip:  0.39 kB
build/client/assets/use-local-storage-DpI-rBck.js               0.55 kB │ gzip:  0.36 kB
build/client/assets/ArrowLeftIcon-DwnJrsqm.js                   0.59 kB │ gzip:  0.41 kB
build/client/assets/icon-button-CBRrVueT.js                     0.62 kB │ gzip:  0.39 kB
build/client/assets/use-hydrated-4Kqb_AE9.js                    0.69 kB │ gzip:  0.47 kB
build/client/assets/index-BFTMnjod.js                           0.79 kB │ gzip:  0.53 kB
build/client/assets/checkbox-B33403AD.js                        0.90 kB │ gzip:  0.47 kB
build/client/assets/index-CpXKBTBY.js                           0.91 kB │ gzip:  0.51 kB
build/client/assets/layout-5ML8qZ8z.js                          1.04 kB │ gzip:  0.59 kB
build/client/assets/box-COFKvEvu.js                             1.12 kB │ gzip:  0.44 kB
build/client/assets/read-file-oVWGX_bV.js                       1.25 kB │ gzip:  0.81 kB
build/client/assets/aes-Bj6qpX1Y.js                             1.32 kB │ gzip:  0.75 kB
build/client/assets/utiliti-ByJwoYeB.js                         1.41 kB │ gzip:  0.75 kB
build/client/assets/content-wrapper-D-meDMf3.js                 1.60 kB │ gzip:  0.75 kB
build/client/assets/copy-3pRH-mRj.js                            1.84 kB │ gzip:  0.99 kB
build/client/assets/cuid-CNOgEfUN.js                            2.03 kB │ gzip:  1.00 kB
build/client/assets/utilities-BuKWQYs9.js                       2.34 kB │ gzip:  1.08 kB
build/client/assets/index-DpehTMXh.js                           2.65 kB │ gzip:  1.32 kB
build/client/assets/password-generator-K6Di2oda.js              2.97 kB │ gzip:  1.39 kB
build/client/assets/read-CUf43Fzd.js                            3.16 kB │ gzip:  1.43 kB
build/client/assets/ns-lookup-B1MGU17T.js                       3.34 kB │ gzip:  1.42 kB
build/client/assets/whois-D2Qm9nHZ.js                           3.87 kB │ gzip:  1.69 kB
build/client/assets/index-D1jatSMv.js                           3.92 kB │ gzip:  1.54 kB
build/client/assets/lorem-ipsum-CetD_upI.js                     4.08 kB │ gzip:  1.97 kB
build/client/assets/hashing-05fSGuQs.js                         4.70 kB │ gzip:  2.08 kB
build/client/assets/json-fz1WGH8m.js                            4.75 kB │ gzip:  2.03 kB
build/client/assets/dataurl-B96PRtSa.js                         4.80 kB │ gzip:  2.30 kB
build/client/assets/url-fH4UuOzx.js                             5.08 kB │ gzip:  2.04 kB
build/client/assets/uuid-CF5N5T8Y.js                            6.01 kB │ gzip:  2.55 kB
build/client/assets/convert-image-file-DtxHnUM0.js              8.92 kB │ gzip:  3.30 kB
build/client/assets/index-B0YDkp51.js                          11.26 kB │ gzip:  4.57 kB
build/client/assets/base64-DmXM8qwS.js                         12.12 kB │ gzip:  5.55 kB
build/client/assets/word-counter-CowxjIvF.js                   13.41 kB │ gzip:  5.20 kB
build/client/assets/transition-CJoS8xpa.js                     14.96 kB │ gzip:  5.84 kB
build/client/assets/common-onpKa1Wt.js                         20.78 kB │ gzip:  8.12 kB
build/client/assets/qr-code-DfwGU98A.js                        23.30 kB │ gzip:  9.10 kB
build/client/assets/tooltip-HYFeb3uA.js                        28.87 kB │ gzip: 10.52 kB
build/client/assets/unix-timestamp-BvIETa8U.js                 29.14 kB │ gzip:  8.88 kB
build/client/assets/code-BK1E5QhO.js                           47.20 kB │ gzip: 17.88 kB
build/client/assets/json-viewer-YIgRKUf8.js                    62.36 kB │ gzip: 22.03 kB
build/client/assets/markdown-to-html-DH4kPQze.js               65.33 kB │ gzip: 22.31 kB
build/client/assets/routes-DLbOHaFQ.js                         85.95 kB │ gzip: 19.75 kB
build/client/assets/image-converter-BMPV43IC.js               103.37 kB │ gzip: 32.59 kB
build/client/assets/chunk-HA7DTUK3-Bv1ZaYQK.js                109.19 kB │ gzip: 36.93 kB
build/client/assets/root-DOtebZ16.js                          168.40 kB │ gzip: 56.18 kB
build/client/assets/entry.client-DTQ4uIB-.js                  175.75 kB │ gzip: 56.04 kB
build/client/assets/sql-formatter-BYY2Ktyq.js                 235.31 kB │ gzip: 59.81 kB
✓ built in 2.87s
vite v6.1.0 building SSR bundle for production...
"default" is imported from external module "react" but never used in "virtual:react-router/with-props", "app/routes/hashing.tsx", "app/routes/url.tsx", "app/routes/uuid.tsx", "app/routes/cuid.tsx", "app/routes/sql-formatter.tsx", "app/components/utiliti.tsx", "app/routes/dataurl.tsx", "app/routes/base64.tsx", "app/components/number-input.tsx", "app/components/dropdown.tsx", "app/components/read-file.tsx", "app/routes/unix-timestamp.tsx", "app/components/json-viewer.tsx", "app/components/shadow-dom.tsx", "app/routes/markdown-to-html.tsx", "app/components/read-only-textarea.tsx", "app/routes/password-generator.tsx", "app/hooks/use-local-storage.ts", "app/routes/private-note/index.tsx", "app/hooks/use-isomorphic-layout-effect.ts", "app/routes/lorem-ipsum.tsx", "app/components/icon-button.tsx", "app/routes/qr-code.tsx", "app/hooks/use-hydrated.ts", "app/routes/private-note/read.tsx", "app/components/tooltip.tsx", "app/routes/word-counter.tsx", "app/components/copy.tsx", "app/routes/json.tsx", "app/routes/image-converter.tsx", "app/components/popular-utilities.tsx", "app/components/search.tsx", "app/hooks/use-keyboard-shortcut.ts" and "app/components/layout.tsx".
✓ 67 modules transformed.
build/server/.vite/manifest.json                       0.73 kB
build/server/assets/stackoverflow-dark-Cx-PguMy.css    1.27 kB
build/server/assets/tailwind-DyU7gPKC.css             51.23 kB
build/server/index.js                                248.11 kB
Prerender (html): /private-note/ -> build/client/private-note/index.html
Prerender (html): /json -> build/client/json/index.html
Prerender (html): /base64 -> build/client/base64/index.html
Prerender (html): /url -> build/client/url/index.html
Prerender (html): /dataurl -> build/client/dataurl/index.html
Prerender (html): /image-converter -> build/client/image-converter/index.html
Prerender (html): /word-counter -> build/client/word-counter/index.html
Prerender (html): /markdown-to-html -> build/client/markdown-to-html/index.html
Prerender (html): /lorem-ipsum -> build/client/lorem-ipsum/index.html
Prerender (html): /password-generator -> build/client/password-generator/index.html
Prerender (html): /uuid -> build/client/uuid/index.html
Prerender (html): /cuid -> build/client/cuid/index.html
Prerender (html): /ns-lookup -> build/client/ns-lookup/index.html
Prerender (html): /whois -> build/client/whois/index.html
Prerender (html): /unix-timestamp -> build/client/unix-timestamp/index.html
Prerender (html): /sql-formatter -> build/client/sql-formatter/index.html
Prerender (html): /qr-code -> build/client/qr-code/index.html
Prerender (html): /hashing -> build/client/hashing/index.html
✓ built in 646ms

[brophdawg11]

This doesn't hang for me but fails due to too many open files when trying to load your server build.

I added a debug log right before that to confirm that's what it fails on.

You could try using ulimit to increase the limit potentially?

build/client/assets/root-BeCdkc-D.js                          168.12 kB │ gzip: 56.11 kB
build/client/assets/entry.client-CcCvXKpG.js                  175.65 kB │ gzip: 55.98 kB
build/client/assets/sql-formatter-DRUD8jBg.js                 235.33 kB │ gzip: 59.82 kB
✓ built in 3.79s
vite v6.0.11 building SSR bundle for production...
"default" is imported from external module "react" but never used in "virtual:react-router/with-props", "app/routes/base64.tsx", "app/routes/hashing.tsx", "app/routes/uuid.tsx", "app/routes/cuid.tsx", "app/routes/sql-formatter.tsx", "app/components/dropdown.tsx", "app/routes/unix-timestamp.tsx", "app/components/utiliti.tsx", "app/routes/url.tsx", "app/components/read-file.tsx", "app/components/json-viewer.tsx", "app/routes/private-note/index.tsx", "app/routes/image-converter.tsx", "app/components/copy.tsx", "app/routes/json.tsx", "app/components/tooltip.tsx", "app/routes/lorem-ipsum.tsx", "app/components/read-only-textarea.tsx", "app/components/number-input.tsx", "app/routes/password-generator.tsx", "app/components/shadow-dom.tsx", "app/routes/markdown-to-html.tsx", "app/hooks/use-local-storage.ts", "app/routes/word-counter.tsx", "app/hooks/use-isomorphic-layout-effect.ts", "app/hooks/use-hydrated.ts", "app/routes/private-note/read.tsx", "app/routes/dataurl.tsx", "app/components/icon-button.tsx", "app/routes/qr-code.tsx", "app/components/popular-utilities.tsx", "app/hooks/use-keyboard-shortcut.ts", "app/components/search.tsx" and "app/components/layout.tsx".
✓ 67 modules transformed.
build/server/.vite/manifest.json                       0.84 kB
build/server/assets/stackoverflow-dark-Cx-PguMy.css    1.27 kB
build/server/assets/tailwind-DyU7gPKC.css             51.23 kB
build/server/index.js                                245.58 kB
importing  file:///.../utiliti.dev/build/server/index.js     ⚠️ <-- debugging log added by me
x Build failed in 370ms
[react-router] EMFILE: too many open files, open '/.../utiliti.dev/node_modules/jszip/lib/index.js'
    at Object.openSync (node:fs:561:18)
    at readFileSync (node:fs:445:35)
    at getSourceSync (node:internal/modules/esm/load:68:14)
    at getSource (node:internal/modules/esm/translators:65:10)
    at createCJSModuleWrap (node:internal/modules/esm/translators:181:32)
    at ModuleLoader.commonjsStrategy (node:internal/modules/esm/translators:272:10)
    at ModuleLoader.#translate (node:internal/modules/esm/loader:437:12)
    at ModuleLoader.loadAndTranslate (node:internal/modules/esm/loader:484:27) {
  errno: -24,
  code: 'PLUGIN_ERROR',
  syscall: 'open',
  path: '/.../utiliti.dev/node_modules/jszip/lib/index.js',
  pluginCode: 'EMFILE',
  plugin: 'react-router',
  hook: 'writeBundle'
}

[inssein]

I changed my session ulimit and had no luck, haven't tried changing it system-wide. Additionally, this doesn't fail just for me; it also fails in CI when Cloudflare tries to build the project with: "Failed: build exceeded the time limit and was terminated.".

[cwagner22]

Same issue for me on vercel at runtime, due to material-ui ESM icons...
Did you find a solution?

[inssein]

How do you know it's due to the icons? I don't have a solution yet (not urgent as I was just experimenting), but I actually don't even know what the actual problem is.

[tonny008]

for me it hangs at this line.

let build = await import(url.pathToFileURL(serverBuildPath).toString());

react-router/packages/react-router-dev/vite/plugin.ts

Line 2222 in 71be3d6

let build = await import(url.pathToFileURL(serverBuildPath).toString());

[azula9713]

Facing the same issue. Any fix?

[brophdawg11]

I'm going to close this out since we don't have a reproduction but if you can provide one please add it here and we can revisit.