How good different LLMs are at writing Ruby code

#​744 — March 27, 2025

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Ruby Weekly

Fast MCP: A Ruby Implementation of the Model Context Protocol— MCP (Model Context Protocol) servers enable certain LLM-based agents (such as Claude, Claude Code, and Cursor) to perform actions/call tools outside of their usual restricted environment. This library lets you build tools in Ruby which such agents can then reach out to and use.

Yorick Jacquin

💡 Interest in MCPs is taking off rapidly, with a Rails-focused MCP implementation also available. OpenAI is also beginning to show an interest in working with MCP, so it's becoming a bit of a standard now.

Ruby 3.2.8 and 3.1.7 Released— These minor releases fix the vulnerabilities in CGI and URIdescribed here. Ruby 3.1.7 is also considered the final release of the 3.1 series with users encouraged to upgrade to 3.3 or 3.4.

Hiroshi SHIBATA

NEW: Get Real-Time Alerts from Your Logs in Honeybadger— We just shipped a new feature for log management. Alarms allow you to combine a query (“count all slow requests in the past five minutes”) with a threshold (”when count is > 2”) and trigger alerts when the result exceeds the threshold. Read the blog post →

Honeybadger sponsor

Exploring Ruby Ractors— Inspired by some recent posts about Ractors, John set out to see if he could use them to peg his CPU usage (“I paid for 10 cores, I’m gonna use 10 cores”). A fun exploration, including a look at just how much YJIT contributes to the modern Ruby performance story.

John Terry

New Policies to Support the Growth of RubyGems— In response to a potential legal issue that arose around taking down a gem with a possibly trademarked name, Ruby Central is tightening up its official policies which can be read in full here– the policies will take final effect in late May, after a review period.

Marty Haught (Ruby Central)

IN BRIEF:

• 📕 It's great to hear from Russ Olsen that a second edition of Eloquent Ruby is under development.

• 🤖 Oskars Ezerins has benchmarked how good different LLMs are at generating Ruby code. Claude's Sonnet models currently lead the pack.

• 🇳🇱 There are just two weeks left to submit a talk if you want to speak at Rails World 2025.

A Practical Guide to Taming Postgres Isolation Anomalies— A practical, Ruby-themed (though SQL heavy) walkthrough of Postgres’ concurrency control, detailing real-world issues like lost updates, write skew, and other isolation anomalies. Even if you rarely run into conflicts, you’ll come away with valuable insights on managing transactions.

Dan Svetlov

Examples of Value Objects with Ruby's Data Class— We linked to Lucian’s article on value objects last week. He follows up with some useful examples of using them to remove boilerplate code and handle API responses.

Lucian Ghinda

🚀 FastRuby.io Makes Your Rails Upgrade Delightfully Boring with Bonsai— The team behind RailsBump.org offers gradual, 0-downtime upgrades — transform your engineering culture with our experts.

Bonsai | Upgrade Experts sponsor

📄 Running Interactive Sessions with Kamal– How to connect to a container on a server managed by Kamal and run an interactive session. Josef Strzibny

📄 Very-Nearly-Free HTTPS Redirects for Heroku and DNSimpleJustin Searls

📄 ActiveRecord Query Log Tags for GraphQLFritz Meissner

📄 Running JavaScript After a Turbo Stream RendersJosef Strzibny

📄 Using Postgres Database Constraints in Active RecordTejas Bubane

📄 Heroku and Ruby Compatibility TableLucero and Medeiros (FastRuby)

📄 Using the Presenter Pattern in RailsTrésor Bireke

🛠 Code & Tools

PicoRuby: A Tiny Ruby Implementation for Microcontrollers— An interesting alternative mruby implementation designed to get its footprint down even smaller to run on small one-chip microcontrollers. Just 256KB of ROM and 128KB of RAM is needed.

HASUMI Hitoshi

RuboCop v1.75.0: The Static Code Analyzer and Formatter— RuboCop gains improved support for Ruby 3.4. As creator Bozhidar Batsov noted on X: “You won’t be able to tell it from the outside, but this release required a ton of work to get to the point where Ruby 3.4 functionality was exposed via Prism’s Parser translation layer.”

Bozhidar Batsov

🐌 If Your Rails Team Needs a Little Boost…— We can augment your team with devs to help you keep up with your delivery schedule. Test us!

SINAPTIA sponsor

Terrapin 1.1: Run Shell Commands Safely— A little extra abstraction for running shell commands that provides safer interpolation, particularly if using user-supplied values.

thoughtbot, inc.

• Logger v1.7.0– Logging utility for outputting messages in Ruby apps.

• openapi_first v2.5.0– Validate requests and responses against an OpenAPI description.

• ViewComponent 3.22– Build encapsulated view components in Rails.

• counter_culture 3.9– Turbo-charged counter caches for Rails apps.

• RDoc 6.13– Ruby's long standing documentation generator.

• Vernier 1.6– Next generation CRuby profiler.

📢  Elsewhere

A quick roundup of some other interesting updates or useful resources in the broader developer landscape:

• Rubyist David Bryant Copeland has given desktop Linux a try after 20 years away and shares a lot of detail about his experiences in getting things set up for dev work.

• <select> elements have always been notoriously tricky to style with CSS but there's a new standardized approach beginning to become available.

• Ethan McCue has some 'life altering' Postgres patterns for you, and he promises the title isn't clickbait.

• 🛠️ Make Bookmarklets is a handy tool for turning JavaScript into bookmarklet code that you can use directly in a browser bookmark.

• Someone's managed to get Go code to compile and run on the PlayStation 2.