--- title: "A look into Ruby's JIT magic" publication: "Ruby Weekly" issue: 766 published_at: "2025-09-11" canonical_url: "https://rubyweekly.com/issues/766" --- Plus a detailed overview of DHH's Rails World keynote. | #​766 — September 11, 2025 [Read on the Web](https://rubyweekly.com/issues/766) I've put together a timestamped summary of the main points from DHH's Rails World keynote _at the end of this issue_ as I know not everyone has an hour free to watch it :-) __ _Your editor, Peter Cooper_ Together with [![FastRuby.io\](https://res.cloudinary.com/cpress/image/upload/c_fill,g_auto,w_467,h_106/e_make_transparent/co_white,e_outline:14/y65nyff19ylf5udphsq4.png)](https://go.fastruby.io/e79) Ruby Weekly [![\](https://res.cloudinary.com/cpress/image/upload/w_1280,e_sharpen:60,q_auto/oqr6lbbx5l3pykj8fchg.jpg)](https://railsatscale.com/2025-09-08-how-ruby-executes-jit-code-the-hidden-mechanics-behind-the-magic/) [How Ruby Executes JIT Code: The Hidden Mechanics Behind the Magic](https://railsatscale.com/2025-09-08-how-ruby-executes-jit-code-the-hidden-mechanics-behind-the-magic/) — Stan Lo works in the depths of Ruby’s tooling (most notably on IRB and `ruby/debug`) but still felt detached from how Ruby’s JIT compilers (like YJIT and ZJIT) actually work. This is his attempt at shining some light on the topic and might clarify your thinking too. Stan Lo [![\](https://res.cloudinary.com/cpress/image/upload/c_limit,w_480,h_480,q_auto/copm/859b5b29.png)](https://go.fastruby.io/e79) [📍Your AI-Powered Rails Roadmap is Here!](https://go.fastruby.io/e79) — 🗺️ Say goodbye to upgrade guesswork and get smarter Rails upgrades with AI. Our new Free Automated Roadmap uses an AI Agent to deliver a custom roadmap tailored to your application. FastRuby.io | Upgrade Experts sponsor **IN BRIEF:** - We're still waiting for full talk videos from _Rails World_, but the official Ruby on Rails YouTube channel has [a playlist of videos from Rails World](https://www.youtube.com/playlist?list=PLHFP2OPUpCebhAv1ZWb_978cTl1o-yue-) — focused, so far, on shorter interview segments. - Peter Zhu has, however, shared [the slides from his _Ruby Stability at Scale_talk.](https://blog.peterzhu.ca/assets/rails_world_2025_slides.pdf) - [Awesome Ruby Blogs](https://github.com/Yegorov/awesome-ruby-blogs) is a rather epic list of Ruby news sources, bloggers, aggregators, and more. - [ReActionView](https://reactionview.dev/) is a new ActionView-compatible ERB engine from the [Herb](https://herb-tools.dev/)project. ▶[A Fresh Look at the RubyMine IDE](https://www.driftingruby.com/episodes/rubymine) — After last week’s announcement that the RubyMine IDE is [now free for non-commercial use](https://blog.jetbrains.com/ruby/2025/09/rubymine-is-now-free-for-non-commercial-use/), David Kimura decided to take another look at it. David Kimura [Explaining `rv`: A Rust-Powered Ruby Version Manager](https://socket.dev/blog/rv-is-a-new-rust-powered-ruby-version-manager-inspired-by-uv) — A look into [rv](https://github.com/spinel-coop/rv), a new Ruby management tool inspired by Python’s [uv](https://github.com/astral-sh/uv). Why does it matter, what does it do, and what’s coming up next? Sarah Gooding (Socket) [Legacy System Refactor vs. Rewrite… or Something in Between? 🤔](https://link.testdouble.com/430146) — How do you decide which makes sense? A right-sized subsystem design with seam-based modernization can be useful. Curious? Test Double sponsor 📄 [Fibonacci Funhouse: Exploring Ruby Algorithms for Fibonacci Numbers](https://www.rorvswild.com/blog/2025/fibonacci-ruby-algorithms) – A look at implementing various algorithms to tackle a simple, well-known problem. Kyle d'Oliveira 📄 [File Preallocation on macOS in Ruby](https://tenderlovemaking.com/2025/09/10/file-preallocation-on-macos-in-ruby/) – This _is_ very niche, but a potentially handy technique. Aaron Patterson 📄 [Rails Without Ruby](https://www.dotruby.com/articles/rails-without-ruby) – Well, without Ruby being locally installed, anyway. How? Devcontainers! Victor Cobos 🛠 Code & Tools [![\](https://res.cloudinary.com/cpress/image/upload/w_1280,e_sharpen:60,q_auto/bopwllxff7naykzysmfk.jpg)](https://github.com/basecamp/once-campfire) [37signals' Campfire Chat App Now Open Source](https://github.com/basecamp/once-campfire) — As part of his keynote (more on that below), DHH announced that the source for Campfire is now generally available (previously you had to pay for it). It’s a great exemplar of a large, modern Rails app built by DHH and 37signals’ developers using standard Rails practices – I’ve learnt a lot from its source code. You can also customize and deploy it to have your own chat system too. 37signals [httpx 1.6: HTTP Client Library, Now with Fiber Concurrency](https://gitlab.com/os85/httpx) — A powerful HTTP client library with a particularly simple API. It supports HTTP/2 and HTTP/1, you get concurrent requests by default, a chainable API, compression support, and more. v1.6 adds [a new fiber concurrency plugin](https://honeyryderchuck.gitlab.io/httpx/wiki/Fiber-Concurrency) so a HTTPX session can be used seamlessly across fibers managed by a fiber scheduler. Tiago / HoneyryderChuck [🚅 Everyone Wants to Jump on the AI Train and We've Got Tickets](https://sinaptia.dev/posts/mcp-on-rails) — Join us on our trip to make your LLM agents interact with your Rails application with MCP. [Discover more destinations on our website](https://sinaptia.dev/blog/tags/ai/). SINAPTIA sponsor [Rails::Diff: Compare Rails-Generated Files with the Ones in Your App](https://github.com/MatheusRich/rails-diff) — You might diligently upgrade your app to new Rails versions but still have differences from how Rails’ default app generator now does things. This lets you see what those differences are (such as those introduced in [Rails 8.1 beta](https://rubyonrails.org/2025/9/4/rails-8-1-beta-1), for example). Matheus Richard - 🤖 [RubyLLM 1.7](https://github.com/crmne/ruby_llm/releases/tag/1.7.0) – A single Ruby interface to AI / LLM models and APIs. v1.7 overhauls the Rails integration significantly, introduces Google Cloud Vertex AI support, and adds a generator to build a chat UI in one command. - [Parklife 0.8](https://github.com/benpickles/parklife) – 🌳 Render a Rack app to a static build. Its Rails integration has been moved into a separate gem and now includes support for Active Storage. - [Rdkafka 0.23](https://github.com/karafka/rdkafka-ruby) – Fast Kafka client library based on`librdkafka`. - [rchardet 1.10](https://github.com/jmhodges/rchardet) – Character encoding auto-detection library. - [TinyTDS 3.3](https://github.com/rails-sqlserver/tiny_tds) – FreeTDS bindings for _SQL Server_users. - [Solidus 4.6](https://github.com/solidusio/solidus) – Rails-based ecommerce platform. - [Anthropic SDK for Ruby 1.9](https://github.com/anthropics/anthropic-sdk-ruby) 📰 Classifieds **Rails Paralysis? Query Analysis** [Scout Monitoring](https://www.scoutapm.com/ruby-monitoring?utm_content=09-11-2025&utm_medium=cooperpress&utm_source=sponsorship) brings you detailed insights about app database usage with a five-minute install. --- 🚀 Ruby developers ship code faster with [AppSignal](https://www.appsignal.com/?utm_source=cooperpress&utm_medium=cooperpress&utm_term=ruby_nl). Locate bugs, fix performance issues, and troubleshoot less. [Start your free trial today](https://www.appsignal.com/?utm_source=cooperpress&utm_medium=cooperpress&utm_term=ruby_nl). 🎬 A Guide to DHH's _Rails World_ Keynote [![\](https://res.cloudinary.com/cpress/image/upload/w_1280,e_sharpen:60,q_auto/e5kblbvwroyftqmcbpoy.jpg)](https://www.youtube.com/watch?v=gcwzWzC7gUA) David Heinemeier Hansson (DHH) [▶️ gave the opening keynote](https://www.youtube.com/watch?v=gcwzWzC7gUA) at [Rails World](https://rubyonrails.org/world/) last week, and it seemed to resonate strongly on social media with its mix of DHH's typically strong opinions, tech releases, and updates on what's coming to Rails. I appreciate not everyone will want, or have the time, to watch it, so _I did_ and here are the key points with timestamps: - `00:00`: DHH decides to start without an uplifting intro, instead focusing on getting us to think about the problems we're trying to solve. - `02:40`: Have we gone backwards from the era of being able to upload an app to a server in seconds over FTP versus the modern era of deploying 101 bits and pieces in 15 minutes? - `11:12`: DHH loves Markdown and shows off [how Rails 8.1 is making it easier to render Markdown](https://rubyonrails.org/2025/9/4/rails-8-1-beta-1#markdown-rendering). - `13:20`: He introduces [Lexxy](https://dev.37signals.com/announcing-lexxy-a-new-rich-text-editor-for-rails/), a new rich text editor for Rails to ultimately replace [Trix.](https://trix-editor.org/) - `16:30`: A quick look at [Active Job Continuations](https://github.com/rails/rails/pull/55127), a mechanism for interrupting and resuming jobs. - `17:38`: A focus on efforts to work with native apps, the forthcoming introduction of _Turbo Offline_, and push notifications via Action Push. - `24:00`: DHH announces [the Campfire source code](https://github.com/basecamp/once-campfire) is now free to obtain. - `25:30`: Thoughts around the problems and techniques around running apps locally during development, the pros and cons of Docker, and using [Mise](https://mise.jdx.dev/) to manage Ruby versions. - `29:00`: DHH talks about the pain of system tests and why he's gone fully sour on them. - `38:30`: After going through the performance benefits of [running CI locally](https://rubyonrails.org/2025/9/4/rails-8-1-beta-1#local-ci), DHH segues into a long section showing off [Omarchy](https://omarchy.org/), his new Arch Linux-based desktop configuration. - `56:35`: What if instead of one large database containing all your app users' data, you could split everything up and have numerous local servers each containing subsets of users? Enter _Active Record Tenanting_ to help with that. - `58:15`: _Beamer_ is a new system for replicating SQLite databases at scale. - `59:00`: _Kamal Geo Proxy_ is the final piece of the global distribution puzzle and will enable routing to instances of Rails apps located wherever they are. - `1:02:50`: DHH encourages us to do 'more end-to-end problem solving', to change things in the stack wherever we like, and to have end-to-end freedom over our stacks. You can [▶️ watch along here](https://www.youtube.com/watch?v=gcwzWzC7gUA) and jump to the timestamps above as appropriate. Curated by [Peter Cooper](https://twitter.com/cooperx86) and [Glenn Goodrich](https://twitter.com/ruprict). Published by [Cooperpress](https://cooperpress.com/). 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