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Charles Oliver Nutter

@headius.bsky.social
1.8K followers 75 following 682 posts

JRuby co-lead, Java champion, Ruby hero, JavaOne Rockstar, international traveler and speaker. Book me for your next event! I depend on your donations and sponsorships! github.com/sponsors/headius

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Charles Oliver Nutter @headius.bsky.social · 29/09/2026
I've pushed a Rails 8.1-compatible activerecord-jdbc-adapter 81.0.pre1 for JRuby + SQLite and it can at least CRUD a scaffold app! I've provided a template here for generating a new app: (rails new -m <template>) buff.ly/uUPEfJn
buff.ly
https://raw.githubusercontent.com/jruby/rails_templates/refs/heads/main/rails-8.1.rb
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Donald Raab @thedonraab.bsky.social · 26/09/2026
"Eclipse Collections Categorically" is a thinking book. What if you could tell your data structures to do work for you? What categories of things would you ask for? 🤷‍♂️👇 *Note*: $0 to buy Amazon Kindle version for few more hours. Search title on website, not mobile. donraab.medium.com/my-ten-year-...
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Charles Oliver Nutter @headius.bsky.social · 25/09/2026
Top three questions I got at #railsworld: Q: Does Rails work on JRuby? A: Yes, for 20 years now. Q: Didn't JRuby already solve this? A: Yes. Q: Why aren't you speaking here? A: I tried. Ask the organizers.
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Charles Oliver Nutter @headius.bsky.social · 24/09/2026
I'll be hanging out at #railsworld in the hack space near the entry. Come on over to chat about JRuby, or claim a shirt if you're a current user or supporter!
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Charles Oliver Nutter @headius.bsky.social · 24/09/2026
Very interesting day of discussions at #railsworld! Introduced a few folks to JRuby, talked with some current users I did not know, even found one shop that only does JRuby. A bit sad to see folks struggling with problems JRuby solves. Hard to get the word out!
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Charles Oliver Nutter @headius.bsky.social · 23/09/2026
Calling all JRubyists at #railsworld! I HAVE T-SHIRTS! If you are using JRuby or officially support it in your app or library, come find me Thursday! I have L, XL, and one 3XL left.
JRuby "bird" T-shirt
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Janko Marohnić @janko.io · 23/09/2026
Yeah, I don't get why not just let this be CRuby's weakness. If you can't get rid of the GVL – which is understandable as even in Python it's still opt-in – then accept that and promote alternative solutions. I don't see how this level of restriction is ever going to work in practice 🤷‍♂️
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Charles Oliver Nutter @headius.bsky.social · 23/09/2026
Hello #railsworld! I'm here at the event running office hours and teaching people how to run Rails on JRuby. Find me in the vendor pavilion and grab a sticker!
me at rails world
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Charles Oliver Nutter @headius.bsky.social · 23/09/2026
It's incredible the amount of hacking required to get Rails to run in parallel with Ractors (and it still isn't there yet) when JRuby has been running Rails in parallel for decades. #railsworld
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The JRuby Project @jrubyproject.bsky.social · 21/09/2026
Hello JRubyists! Anyone planning to be at tiny ruby #{conf} 2026 presented by @helsinkiruby.fi next week? We'd love to help you spread the word about JRuby to the Helsinki Ruby community! Get in touch if we can help you in any way!
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Charles Oliver Nutter @headius.bsky.social · 20/09/2026
It occurs to me now: with the JVM now supporting native function calls and memory via the FFM API, could we not potentially treat it as a C compiler backend?
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Charles Oliver Nutter @headius.bsky.social · 20/09/2026
Would you buy JRuby swag to help fund the project? We recently did a run of JRuby "bird" t-shirts that have been very popular, but that stuff is expensive to give away for a little startup like ours.
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Charles Oliver Nutter @headius.bsky.social · 19/09/2026
Brno is a lovely little city. Don't know why I didn't see it when I visited in 2012.
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Charles Oliver Nutter @headius.bsky.social · 18/09/2026
It's amazing how quickly the toxic AI bros come out on X if you say one bad word about AI. Are they even real people?
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Charles Oliver Nutter @headius.bsky.social · 18/09/2026
I think I'm going to enable the JVM vector API (SSE etc, we already ship some optimizations that use it) by default for JRuby. Convince me not to.
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Charles Oliver Nutter @headius.bsky.social · 18/09/2026
After all these years, I just got burned (almost) by having a CI job not actually fail when one of the steps failed. It involved a subprocess launch with no error check, so even if it bombed out the job stayed green. 😩 A friendly reminder to make sure your CI jobs actually *can* fail.
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Charles Oliver Nutter @headius.bsky.social · 18/09/2026
Slides from my Euruko 2026 talk "JRuby: Past, Present, and Future" are now uploaded. I believe the talks were also recorded, so hopefully video will follow soon. Great event, I hope to return for 2027 in Modena, Italy! buff.ly/paSd5t9
buff.ly
JRuby: Past, Present, and Future
JRuby on Rails is 20 years old! This talk reviews the last 20 years of JRuby development, with a focus on the challenges of supporting Ruby and Rails ye…
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Charles Oliver Nutter @headius.bsky.social · 18/09/2026
AI is now the largest single point of failure in the history of software development. I know tons of developers that can't even work without an agent now. It's shocking how quickly the industry has become totally dependent on a few companies' services.
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Charles Oliver Nutter @headius.bsky.social · 18/09/2026
I'm finding more and more that agent-driven developers *really* appreciate having a human validate what they submit. nobody wants to be the asshole in an OSS project and being honest and communicative goes a long way toward making a good patch.
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Charles Oliver Nutter @headius.bsky.social · 17/09/2026
Like clockwork, I go to a Ruby event and meet JRuby users I never knew about! Just today, three people who used JRuby at previous jobs and two more that currently have apps in production. Gotta figure out how to reach these folks without speaking at every Ruby conference! 🤣
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Charles Oliver Nutter @headius.bsky.social · 17/09/2026
Interested in Ruby::Box? Use JRuby and you already have it! These are fully-isolated, fully-parallel JRuby VMs running in the same process. Here's a simple example from my Euruko 2026 talk. Let's work together to make Box work on ALL Rubies!
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Charles Oliver Nutter @headius.bsky.social · 15/09/2026
Feels nice to be back in Czechia! I'm currently transiting from Prague to Brno for Euruko 2026. I think the last time I visited was almost 14 years ago, shortly after first joining Red Hat. I have a free day before and after the conference so I'm hoping to do a bit of touring.
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Charles Oliver Nutter @headius.bsky.social · 14/09/2026
My own experiments using AI for JRuby work have been mixed, but I can report a great success: contributions from people that never would have attempted such things before, like Ruby core devs and Rubyists with no JVM experience. So many PRs lately! github.com/jruby/jruby
github.com
GitHub · Change is constant. GitHub keeps you ahead.
Join the world's most widely adopted, AI-powered developer platform where millions of developers, businesses, and the largest open source community build software that advances humanity.
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Euruko @euruko.org · 13/09/2026
Last call: EuRuKo 2026 tickets close tomorrow at midnight CEST. @matz.bsky.social opening, @ko1s.bsky.social closing, @headius.bsky.social on JRuby. Brno, Sept 17–18. After tomorrow there's no late registration. 2026.euruko.org
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Charles Oliver Nutter @headius.bsky.social · 02/09/2026
I recently had a nice chat on the Technology for Humans podcast about the past, present and future of JRuby... including some myth debunking that might help Ruby folks look past the "J" to the amazing tech underneath. Check out the video here: www.youtube.com/watch?v=Q9Sq...
youtube.com
The Ruby Runtime Built for Scale, Parallelism and Enterprise : JRuby
YouTube video by Technology For Humans
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Charles Oliver Nutter @headius.bsky.social · 02/09/2026
And thanks to JRuby friend @cglee.bsky.social I now also have a ticket! Super excited to join the hallway track and show folks how to do more with Rails using JRuby! 🤩
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Charles Oliver Nutter @headius.bsky.social · 01/09/2026
Good news! I will be in Austin during Rails World 2026 and available for JRuby office hours. I'm still looking for a ticket (budget is very tight!) but I can't miss out on meeting Rails folks from around the world. If you're a JRuby user or might like to be, let's grab a drink and chat!
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Charles Oliver Nutter @headius.bsky.social · 13/08/2026
Friendly reminder to JRuby users out there: JRuby dev is now funded almost exclusively by support services from headius.com/services, delivering priority bug fixes, security SLAs, codebase and performance help under NDA, and much more. Sign up today or ping me for more info... and tell your friends!
headius.com
JRuby Support Services
Enterprise JRuby support, consulting, and priority bug-fixing from the core developers who built it. 20+ years of JVM and Ruby expertise.
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Charles Oliver Nutter @headius.bsky.social · 07/08/2026
My experiments with agent-augmented dev feel like "coding by dictation", and always require manual review and MANY follow-ups. Code style: terrible. Naming things: terrible. Math: terrible. Forward-thinking design: terrible. Unsure if I'm more productive or less. 🫤
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Euruko @euruko.org · 06/08/2026
💎 20 years of JRuby. @headius.bsky.social joins EuRuKo 2026 in Brno to cover JRuby's past, present & what's next. Sep 17-18, Brno. Tickets: 2026.euruko.org
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Charles Oliver Nutter @headius.bsky.social · 27/07/2026
I occasionally want to close an experimental PR without losing the context and changes associated with it. Is there a better way than dumping a patch into comments as seen below? I don't want lingering topic branches. github.com/jruby/jruby/...
github.com
Allow binding instance/internal vars to fields by headius · Pull Request #8804 · jruby/jruby
This is an extension of the existing mechanism for reification of Ruby classes, allowing us to use normal Java fields for either instance or internal variables. The logic here is largely unchanged ...
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The JRuby Project @jrubyproject.bsky.social · 22/07/2026
JRuby 10.1.1.0 is released, with a bunch of compat fixes, more performance work, and several third-party CVEs resolved. JRuby 10.1 is our active development branch, with 10.0 being stable. Upgrading is recommended if you want the latest and greatest! www.jruby.org/2026/07/22/j...
jruby.org
JRuby 10.1.1.0 Released — JRuby.org
The JRuby community is pleased to announce the release of JRuby 10.1.1.0.
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Charles Oliver Nutter @headius.bsky.social · 23/07/2026
Is there any standard in place for marking content with its level of AI contribution? Basically, a *standard* way to mark your content as fully human generated all the way up to fully AI generated. Doesn't seem like there's a good standard.
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Charles Oliver Nutter @headius.bsky.social · 20/07/2026
I'm about ready to give up on GitHub Milestones altogether. * No linkage with releases or tags whatsoever * No way to mark multiple milestones * Crappy management UI What am I missing?
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Charles Oliver Nutter @headius.bsky.social · 20/07/2026
I think its time for dependabot-like automated dependency updates to get moved into a separate tab on GH. A few projects I audit for changes are now 90%+ dependabot noise, which adds no value when looking for substantive pull requests. Perhaps a default label for such PRs, with one-click filtering?
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Charles Oliver Nutter @headius.bsky.social · 16/07/2026
Loving #rubyconf this year and seeing so many friends! I'm holding office hours today by the pool at Red Rock Resort, if you're at the event or in the area. We're in cabana number 4 in the roped-off area to the left (see picture). Come say hi and get a JRuby t-shirt or sticker!
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Charles Oliver Nutter @headius.bsky.social · 13/07/2026
Oh boy... After a very long time, we have a new batch of JRuby t-shirts! Limited run so only folks at the JRuby talk, hack space, or cabana can get them! Also plenty of stickers for everyone! blog.headius.com/2026/07/jrub...
jruby tshirt with bird
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Sam Ruby @intertwingly.net · 10/07/2026
> My goal with JRuby has always been to give Rubyists more tools and more opportunities. By combining JRuby with the power and ecosystem of the JVM, we’ve brought Ruby and Rails to places it never could have gone before. Hold my beer. :-)
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Charles Oliver Nutter @headius.bsky.social · 10/07/2026
JRuby returns to RubyConf for the 2026 edition in Las Vegas! I will deliver a talk on Tuesday, run a Hack Space on Wednesday, and would love to hang out with you at JRubyKaraoke (Tuesday night) and the poolside JRuby Cabana (Thursday). Here's all the info: blog.headius.com/2026/07/jrub...
blog.headius.com
JRuby at RubyConf 2026
This year marks a big milestone in my history working on JRuby: twenty years ago, I joined Sun Microsystems to work on the project full-time. This month also marks another milestone for JRuby: two…
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Charles Oliver Nutter @headius.bsky.social · 01/07/2026
The more I see pull requests from LLMs and experiment with it myself the more convinced I am that it produces just about the worst code I've ever seen. Not just bad on style, but inefficient, often incorrect, and usually the wrong approach. It "works" in the loosest sense of the word.
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Charles Oliver Nutter @headius.bsky.social · 29/06/2026
I keep hearing how AI will make software so easy to write and yet Gmail still hasn't evolved beyond the mid 2010s.
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Charles Oliver Nutter @headius.bsky.social · 26/06/2026
I'm planning to add direct support for WASM libraries to JRuby so that you don't have to do any of the plumbing to boot up Chicory and bind the exposed functions. Imagine something like JRuby's Java integration, but you just `require 'mylib.wasm'` and call it from Ruby!
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Charles Oliver Nutter @headius.bsky.social · 26/06/2026
Here's a use of AI I can get behind: JRuby support for native Ruby libraries using Chicory WASM for JVM and JRuby's JVM integration! RBS (static types for Ruby) uses a C ext on CRuby, but with this PR it now works on JRuby. JRuby support could really expand with this pattern! buff.ly/SDAtXId
github.com
Build the RBS parser as a WebAssembly module (JRuby support, step 1) by soutaro · Pull Request #2998 · ruby/rbs
Why This is the first step toward running RBS on Ruby implementations that cannot load the MRI C extension — notably JRuby — using WebAssembly instead of an FFI/dylib. The parser under src/ is plai...
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The JRuby Project @jrubyproject.bsky.social · 26/06/2026
Our friends over at @fastruby.io have posted a nice compatibility matrix for JRuby versions, covering Ruby and Rails compatibility. Check it out to learn how the versions line up or if you haven't already discovered how JRuby can help you run Ruby and Rails better! www.fastruby.io/blog/jruby/r...
fastruby.io
JRuby & Rails Compatibility Table - FastRuby.io | Rails Upgrade Service
A complete table showing the compatibility between JRuby and Rails across each version, including the Ruby language level and the Java version that each JRuby line requires.
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Benoit Daloze @eregon.me · 16/06/2026
concurrent-ruby 1.3.7 is released and fixes 3 security vulnerabilities: github.com/ruby-concurr...
github.com
Release v1.3.7 · ruby-concurrency/concurrent-ruby
There are 3 security fixes in this release, so updating is recommended. These security vulnerabilities are not very likely to be hit in practice and have a corresponding Low severity score. What's...
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Charles Oliver Nutter @headius.bsky.social · 21/06/2026
githubstatus.com has overtaken github.com/<anything> in my local browser as the most frequent site I visit after typing "git..."
githubstatus.com
GitHub Status
Welcome to GitHub's home for real-time and historical data on system performance.
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Charles Oliver Nutter @headius.bsky.social · 21/06/2026
Today's AI test: see if Copilot can fix a networking test that sometimes times out. Ran for 5 minutes, changed two InetSocketAddress constructors to use getLoopbackAddress even though the old forms called anyLocalAddress. Fail. The actual fix was to increase the timeout due to slow GHA runners.
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Charles Oliver Nutter @headius.bsky.social · 11/06/2026
Exciting demonstration of how fast JRuby can really be when you sweep away some of the metaprogramming layers of a typical Rails application... even when it already handles Rails HTML requests 2x faster than CRuby! Looking forward to seeing more about Roundhouse.
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Charles Oliver Nutter @headius.bsky.social · 10/06/2026
And it's live! I'll show you the latest and greatest use cases for using JRuby with *real world* examples at RubyConf 2026 in Las Vegas, July 14 at 3:30PM! Tell your friends! rubyconf.org/schedule/
Expand your Ruby Potential with JRuby
Charles Nutter

Breakout 2 - Charleston E-B

JRuby is an implementation of Ruby 4.0 built on the Java Virtual Machine. For the past 20 years we've expanded the horizons of Ruby, bringing more jobs and more opportunities to Rubyists like you: * High-scale applications needing shared-memory parallelism and big data * Enterprise organizations with existing Java infrastructure * Cross-platform, commercial-off-the-shelf (COTS) application packaging that protects your code * Graphics-intensive applications including desktop, games, and visualization * Mobile and embedded solutions using Android And you can do it all in Ruby, with no Java experience required! This talk will review JRuby's history and show you what's possible when you bring the best of Ruby and the JVM together.
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Charles Oliver Nutter @headius.bsky.social · 10/06/2026
Good news! I have been added to the RubyConf 2026 schedule to present JRuby and all the ways it lets you use Ruby when CRuby doesn't fit! I'm glad that the new @rubycentral.org values community and understands the importance of JRuby. Twenty years of JRuby...don't miss this talk!
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