PostCSS issue with Tailwind 4.0

[yogeshbabu]

Which project does this relate to?

Start

Describe the bug

After recent updates. started getting this error with tailwind 4.0. It was working as expected earlier but now it is throwing error. Only solution i can see is old option of creating postcss config and plugin use. Tailwind has moved on from those.

[plugin:vite:css] [postcss] D:/Work/Dev/projects/tanstack/app/assets/styles/globals.css:10505:15: Unknown word err.plugin

Versions in use
"@tanstack/react-query": "^5.67.2", "@tanstack/react-router": "^1.114.13", "@tanstack/react-router-with-query": "^1.114.13", "@tanstack/react-start": "^1.114.13", "react": "^19.0.0", "react-dom": "^19.0.0", "vinxi": "^0.5.3", "tailwindcss": "^4.0.12", "typescript": "^5.8.2", "vite-tsconfig-paths": "^5.1.4", "@tailwindcss/vite": "^4.0.12", "@tailwindcss/typography": "^0.5.16",

Your Example Website or App

localhost

Steps to Reproduce the Bug or Issue

Build app with latest Tailwind 4.0 and use typography plugin in the global.css

Expected behavior

App should import the global.css without unknown error

Screenshots or Videos

No response

Platform

• OS: [e.g. Windows, Linux]
• Browser: [e.g. Chrome, Firefox]

Additional context

No response

[yogeshbabu]

Full error just in case. There isn't much to trace back.
[vite] Internal server error: [postcss] D:/Work/Dev/projects/tanstack/app/assets/styles/globals.css:10505:15: Unknown word err.plugin Plugin: vite:css File: D:/Work/Dev/projects/tanstack/app/assets/styles/globals.css:10505:14 at Input.error (D:\Work\Dev\projects\tanstack\node_modules\postcss\lib\input.js:113:16) at Parser.unknownWord (D:\Work\Dev\projects\tanstack\node_modules\postcss\lib\parser.js:595:22) at Parser.other (D:\Work\Dev\projects\tanstack\node_modules\postcss\lib\parser.js:437:12) at Parser.parse (D:\Work\Dev\projects\tanstack\node_modules\postcss\lib\parser.js:472:16) at parse (D:\Work\Dev\projects\tanstack\node_modules\postcss\lib\parse.js:11:12) at new LazyResult (D:\Work\Dev\projects\tanstack\node_modules\postcss\lib\lazy-result.js:165:16) at Processor.process (D:\Work\Dev\projects\tanstack\node_modules\postcss\lib\processor.js:53:14) at compileCSS (file:///D:/Work/Dev/projects/tanstack/node_modules/vite/dist/node/chunks/dep-Cg8OuIew.js:49895:59) at async TransformPluginContext.transform (file:///D:/Work/Dev/projects/tanstack/node_modules/vite/dist/node/chunks/dep-Cg8OuIew.js:49139:11) at async EnvironmentPluginContainer.transform (file:///D:/Work/Dev/projects/tanstack/node_modules/vite/dist/node/chunks/dep-Cg8OuIew.js:48465:18) at async loadAndTransform (file:///D:/Work/Dev/projects/tanstack/node_modules/vite/dist/node/chunks/dep-Cg8OuIew.js:42166:27) (x2)

[radzi00]

Yesterday I've added Tailwind v4 to Nuxt3 app as a plugin, via nuxt.config.ts and main.css file. (so not related to React framework)

When I run:
npm run dev I have the same error as OP.

But the command:
npm run generate makes static files without any issues.

My problem was solved by updating from tailwindcss 4.0.0 to 4.0.12 (but you are on 4.0.12, sorry)

[yogeshbabu]

Yeah, today tailwind 4.0.13 released, also tanstack elements released minor updates as well. Still same issue.

Also another thing to note, directly running on Vite does not throw this error. Only while using tanstack-start

[khalwat]

I'm also getting this error using Vite 6 + Tailwind CSS 4 -- but I'm not using TanStack, so I think the issue may be with Tailwind CSS and/or Vite rather than being related to TanStack.

vite-1        |   Plugin: vite:css                                                                                                                                                                         
vite-1        |   File: /var/www/project/buildchain/src/css/app.css:2027:14                                                                                                                                
vite-1        |       at Input.error (/var/www/project/buildchain/node_modules/postcss/lib/input.js:113:16)                                                                                                
vite-1        |       at Parser.unknownWord (/var/www/project/buildchain/node_modules/postcss/lib/parser.js:595:22)                                                                                        
vite-1        |       at Parser.other (/var/www/project/buildchain/node_modules/postcss/lib/parser.js:437:12)                                                                                              
vite-1        |       at Parser.parse (/var/www/project/buildchain/node_modules/postcss/lib/parser.js:472:16)                                                                                              
vite-1        |       at parse (/var/www/project/buildchain/node_modules/postcss/lib/parse.js:11:12)                                                                                                       
vite-1        |       at new LazyResult (/var/www/project/buildchain/node_modules/postcss/lib/lazy-result.js:165:16)                                                                                       
vite-1        |       at Processor.process (/var/www/project/buildchain/node_modules/postcss/lib/processor.js:53:14)                                                                                       
vite-1        |       at compileCSS (file:///var/www/project/buildchain/node_modules/vite/dist/node/chunks/dep-glQox-ep.js:49124:59)                                                                       
vite-1        |       at async TransformPluginContext.transform (file:///var/www/project/buildchain/node_modules/vite/dist/node/chunks/dep-glQox-ep.js:48310:11)                                           
vite-1        |       at async EnvironmentPluginContainer.transform (file:///var/www/project/buildchain/node_modules/vite/dist/node/chunks/dep-glQox-ep.js:47636:18)                                       

[yogeshbabu]

I have another project with Vite 6 + Tailwind 4 without any issues. I use Tanstack router and query in that one and running without this error.

I started testing new Start Framework and it was working fine at the beginning. now with recent updates it started throwing this error. It could be after when tanstack/start became tanstack/react-start. I am yet to test if that is the case