buildCSS fails with "Missing closing } at @theme" on Linux CI (Cloudflare Workers Builds) — same code+lockfile, passes on Windows

[deadro22]

These tests were generated using Claude Code to further understand the issue.

Versions

• uniwind: 1.2.7
• tailwindcss: 4.1.18 (root) + 4.1.17 (bundled with @tailwindcss/node@4.1.17 that uniwind pins)
• expo: 54.0.33, metro per Expo defaults
• Node: 22.16.0
• pnpm: 10.28.2 with --config.node-linker=hoisted

What happens

Running pnpm expo export -p web on Cloudflare Workers Builds (Ubuntu CI) consistently fails at ~93% of bundling
with:

SyntaxError: node_modules/uniwind/dist/common/components/web/metro-injected.js: Missing closing } at @theme
Error: Missing closing } at @theme
at Ee (.../@tailwindcss/node/node_modules/tailwindcss/dist/lib.js:1:3353)
...
at Object.Jr (.../@tailwindcss/node/dist/index.js:10:3473)
at findVariantsRec (.../uniwind/dist/shared/uniwind.Hbe7II-i.cjs:225:5)
at generateCSSForThemes (.../uniwind/dist/shared/uniwind.Hbe7II-i.cjs:238:3)
at Object.buildCSS (.../uniwind/dist/shared/uniwind.Hbe7II-i.cjs:300:21)
at injectThemes (.../uniwind/dist/metro/metro-transformer.cjs:1515:3)
at Object.transform (.../uniwind/dist/metro/metro-transformer.cjs:1534:33)

The same code, same lockfile, same --config.node-linker=hoisted install layout succeeds on Windows (I verified
by running pnpm install --config.node-linker=hoisted && pnpm expo export -p web locally on Windows — full export
completes, 124 HTML files generated).

What I ruled out

Hypothesis	Test	Result
Cache poisoning	rm -rf node_modules/uniwind/uniwind.css before each build	Still fails
tailwindcss version drift	Pinned root to 4.1.17 to match @tailwindcss/node@4.1.17	Still fails
Metro worker race	config.maxWorkers = 1 in metro.config.js	Still fails
pnpm hoisted layout	Reproduced exact hoisted layout on Windows	Succeeds
Concurrent buildCSS calls	6 parallel await buildCSS(['light','dark'], cssPath) on Windows	All succeed
Tailwind parsing the regenerated uniwind.css	Manually ran @tailwindcss/node compile against the 421-line
regenerated file	Parses cleanly

The only difference between succeeding and failing is the host OS.

CSS input

global.css uses @variant dark { ... } blocks nested inside @layer theme { :root { ... } }:

@import 'tailwindcss';
@import 'uniwind';

@layer theme {
  :root {
    @variant dark {
      --color-primary: rgb(211, 6, 65);
      /* ... 15 more --color-* vars */
    }
    @variant light {
      /* ... same 16 vars */
    }
    --color-error: rgb(239, 68, 68);
    /* ... shared status colors */
  }
}

@theme {
  --color-primary: var(--color-primary);
  /* ... aliases */
  --font-sans: 'Quicksand-Regular';
}

lightningcss correctly extracts 16 light + 16 dark dashed-idents (confirmed by manually running uniwind's visitor on
Windows).

Suspected location

The error path is findVariantsRec → node.compile('@import "tailwindcss";\n@import "uniwind";') reading the regenerated
node_modules/uniwind/uniwind.css. Since the JS parser is identical across platforms but only fails on Linux, the
corruption likely comes from one of the native pieces upstream (@tailwindcss/oxide or lightningcss's Linux binary)
producing a malformed chunk that the JS parser then chokes on.

Asks

1. Could buildCSS write uniwind.css atomically (write-tmp + rename) and read its own freshly-written content from
   memory rather than re-reading from disk via Tailwind's @import?
2. Could injectThemes be guarded by an in-process mutex to prevent overlap when both the web bundle and the SSR bundle
   hit metro-injected.js?
3. Any known interactions with @tailwindcss/oxide on Linux x64 (gnu) at version 4.1.17?

Thank you in advance.

[github-actions]

This issue has been automatically closed because it lacks a clear, minimal reproduction that we can use to verify the reported bug.

[jpudysz]

Hey,

we don't accept issues without reproduction. I would start with updating Uniwind to 1.7.0.

You'r version is far behind: 1.2.7.

[deadro22]

Hello, Thank you for your quick response and I apologize, updating the Uniwind version to 1.7.0 fixed the issue.

[jpudysz]

Thats awesome, enjoy!