TruffleRuby 34 brings full Ruby 3.4 compatibility, big parsing wins, and a Prism Ripper that’s far faster

What landed

TruffleRuby 34 is released with full Ruby 3.4 compatibility and a stack of performance and maintenance wins. The build is available on GitHub, through common Ruby installers, and on Maven Central. The team says every item in the CRuby 3.4 changelog has been implemented — a milestone made easier because TruffleRuby already implements about 73% of core library methods in Ruby itself.

This release leans hard into startup and parser speed. TruffleRuby now deserializes methods lazily, pushing translation and compilation until a method is actually called, and the project reports parsing time reductions of up to 23%. Why does that matter? Faster startups and snappier test runs — the kind of QoL improvements that make a runtime feel modern, not ancient.

Prism replaces ripper.c — and it’s dramatic

One of the loudest changes is the switch from reusing CRuby’s ripper.c to a Prism-based Ripper translation layer. The rewrite removed roughly 77,000 lines of code — yes, 77k — and it has been reported that Ripper on TruffleRuby is now 20x to 40x faster due to far fewer Ruby↔C crossings. Tools are already waking up to Prism: IRB and RDoc adoption is rising because Prism is reportedly about 2.75x faster on CRuby and offers a nicer API. Deprecate Ripper? The project hints it’s time to consider it.

There are a few other changes worth a nod: the pure-Ruby StringScanner implementation now lives in the strscan gem (so updates flow via the gem), and several contributors got special mention — notably @herwinw and @Earlopain — for multiple PRs that pushed this release over the line.

If you’re curious, try your app or test suite on TruffleRuby 34 and see what pops. The team welcomes bug reports on GitHub and conversations on Slack or Bluesky, and if you’ll be at RubyKaigi 2026, Benoit Daloze will be talking about related optimizations — a good place to hear the behind-the-scenes. Big wins like this feel a bit like the moment your old clunker finally gets a tune-up: smoother, faster, and oddly gratifying.

Sources: truffleruby.dev, Lobsters