While upgrading an older phonix 1.7 app to the newer phoenix 1.8, I am running into an issue with the new tailwind css config mix assets.build 13:45:27.039 [debug] Downloading tailwind from https://github.com/tailwindlabs/tailwindcss/releases/download/v4.1.7/tailwindcss-macos-x64 ≈ tailwindcss v4…

Have a look at phoenixdiff.org this can help you check that other files need to be modified

The Updating from Tailwind v3 to v4 section might be what you’re looking for: https://github.com/phoenixframework/tailwind?tab=readme-ov-file#updating-from-tailwind-v3-to-v4

Thanks. I did all that this one shows. Still scratching my head.

Seems like if I switch from @import "tailwindcss" source(none); To @import "tailwindcss"; I don’t get the error anymore. Not sure why that would cause a problem though TBH.

OK. I give up. I added the source(none) again, and it works fine now. Totally lost and burned several hours on this only to not know what went wrong or why removing source(none) fixed it and why adding it back didn’t break it again.

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Phoenix 1.8 upgrade Tailwind issues

Questions & Help Questions

jdiago August 17, 2025, 7:54pm 7

Sometimes, turning it off and on again fixes things… lol