Running Ruby on Rails on Apple Silicon (M1/M2): Debugging Racc and Tailwindcss Issues

Running Ruby on Rails on Apple Silicon (M1/M2): Debugging Racc and Tailwindcss Issues

While working on a new Ruby on Rails app, I encountered an issue I hadn't seen before. The last Rails app I built was on my old Intel MacBook, but now I'm on an M1 MacBook Pro with the Apple Silicon chip.

Issue #1: racc/parser.rb LoadError

Every time I tried to run rails server or bin/dev, it failed with the following error:

$ rails server
/Users/chris/.local/share/mise/installs/ruby/3.4.5/lib/ruby/3.4.0/bundled_gems.rb:82:in 'Kernel.require': cannot load such file -- racc/parser.rb (LoadError)
        from /Users/chris/.local/share/mise/installs/ruby/3.4.5/lib/ruby/3.4.0/bundled_gems.rb:82:in 'block (2 levels) in Kernel#replace_require'
        
etc......

No matter what I tried, I couldn't get the gem to install correctly.

I believe the root issue was a compatibility conflict — even though the racc gem appeared to install without errors, it wasn’t actually usable due to native extension issues on Apple Silicon.

To resolve this, I manually installed the gem with architecture-specific flags:

$ gem install racc -v 1.8.1 -- --with-cflags="-arch arm64"

** Edit

So after some chatting on the Rails forum, I got told that this can be sorted by adding:

gem "nokogiri", force_ruby_platform: !RUBY_PLATFORM.include?("arm64-darwin")

to the Gemfile and running bundle install. I haven't tried this yet, but can't see any reason why it wouldn't work.

That fixed the cannot load such file -- racc/parser.rb error on my M1 Mac.

Issue #2: Tailwindcss Ruby Executable Not Found

Next, I wanted to use Tailwind CSS in my app. I followed the installation steps from the Tailwind website. However, when I ran bin/dev, it failed silently with an EXIT code.

To dig deeper, I tried running the watcher directly:

$ rails tailwindcss:watch

That returned the following error:

Source locally installed gems is ignoring #<Bundler::StubSpecification name=racc version=1.8.1 platform=ruby> because it is missing extensions
bin/rails aborted!
Tailwindcss::Ruby::ExecutableNotFoundException: Cannot find the tailwindcss executable for arm64-darwin in /opt/homebrew/Cellar/tmuxinator/3.3.4/libexec/gems/tailwindcss-ruby-4.1.11/exe (Tailwindcss::Ruby::ExecutableNotFoundException)
The solution was to ensure that Bundler recognized the Apple Silicon architecture and that force_ruby_platform wasn’t preventing native gems from being installed correctly.

Here’s what I did:

Delete the force_ruby_platform setting (if present):

$ bundle config --delete force_ruby_platform

You can check your current Bundler settings with:

$ bundle config

Add the correct platform to the lockfile and reset Tailwind:

$ bundle lock --add-platform arm64-darwin
$ bundle clean --force
$ bundle remove tailwindcss-rails
$ bundle add tailwindcss-rails
$ bundle install

After that, running:

$ rails tailwindcss:watch

finally worked, showing:

≈ tailwindcss v4.1.11

Done in 37ms
Final Setup

Running bin/dev still failed for me, but I was able to use separate Tmux tabs to run the processes independently:

$ rails server
$ rails tailwindcss:watch

Wrapping Up

I hope this helps someone else running into similar issues with Rails and Tailwind CSS on Apple Silicon Macs. It took me a few hours of trial and error to piece this together — hopefully you can save some time!