Codex skills for Ruby on Rails
With these skills Codex builds Rails 8 the omakase way: params.expect, Hotwire before custom JavaScript, Solid Queue jobs enqueued after commit and validations backed by database constraints. Active Record tuning starts from a measured slow action, RSpec suites lean on build_stubbed and verifying doubles, and Kamal deploys wait for your approval.
Start with these 3
- Ruby Idioms Ruby that reads like Ruby, not translated Java Codex checks the project's Ruby version and RuboCop config, then rewrites manual accumulators into filter_map, tally, partition and each_with_object, models values with Data.define, and destructures API payloads with case/in. It knows the lambda versus proc return rules, frozen string behaviour in Ruby 3.4, and when unsafe autocorrect needs a test run before it is trusted.
- Rails 8 Apps Omakase Rails: REST, Hotwire and Solid Queue done right Codex builds Rails 8 features along the framework's grain: resourceful routes, params.expect, lookups through the current user's associations, and validations mirrored by database constraints. It reaches for Turbo Frames, Streams and morph refreshes before custom JavaScript, enqueues idempotent Solid Queue jobs after commit, and finishes with tests, RuboCop, Brakeman and a migration rollback check. Kamal deploys wait for approval.
- Active Record Performance Faster Rails queries, proven with numbers Codex profiles the slow Rails action or job first, then picks the fix that matches: preload or eager_load for per-row queries, counter caches backfilled in batches for list counts, pluck for read-only data, and in_batches with throttling for mass updates. Index migrations use algorithm: :concurrently with the DDL transaction disabled, and strict_loading keeps lazy loads out of new code.
6 more Ruby on Rails skills
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RSpec Testing
Specs that read as sentences and skip needless rows -
Background Jobs
Jobs that survive retries, crashes and deploys -
SQLite in Production
WAL, short writes and backups that restore -
N+1 Query Fixes
Constant query counts, whatever the page size -
Database Seeding
Rerunnable seeds that look like production -
Kamal Deploys
Zero-downtime container deploys to your own servers
General skills with Ruby on Rails guidance
Not built around Ruby on Rails, but they include steps or tools for it. Not part of the install-all command.
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Zero-Downtime Migrations
Change big tables without a lock-queue outage -
Data Backfills
Touch 80 million rows without anyone noticing -
Flaky Test Triage
Name the cause, prove the fix, retire the retry -
htmx Patterns
Server-rendered interactivity without a SPA -
Session Auth
Revocable logins behind a locked-down cookie -
Auth Libraries
Pick the right auth stack, then wire it safely -
GraphQL Resolvers
Constant query counts and auth on every path -
Connection Pooling
Fit every pool inside max_connections -
CSRF Protection
Forged requests die at the middleware -
Security Headers
Every response, every header, one layer -
Test Data Factories
Valid by default, special only where it matters
Every Ruby on Rails skill in one command
Installs these 9 into ~/.agents/skills/. Add --project after -- to install into the current repository instead.
The installer is a 104-line POSIX shell script. It fetches the skills you name from codexskills.dev and unpacks each into its own folder in your skills directory. No sudo, no telemetry, and every skill page shows the full SKILL.md first. Read install.sh
curl -fsSL codexskills.dev/install.sh | sh -s -- ruby-idioms rails-apps active-record-performance rspec-testing background-jobs sqlite-production n-plus-one-queries database-seeding kamal-deploys Ruby on Rails FAQ
Is there a Codex skill for Rails 8?
Rails 8 Apps uses resourceful routes, params.expect, lookups through the current user's associations and the built-in authentication generator. It reaches for Turbo Frames, Streams and morph refreshes before custom JavaScript, enqueues idempotent Solid Queue jobs after commit, and finishes with tests, RuboCop, Brakeman and a migration rollback check. When a Rails 8.1 bin/ci exists, it treats that as the definition of all checks.
How does Codex fix N+1 queries in Rails?
Active Record Performance profiles the slow action or job first, then picks preload or eager_load for per-row queries, counter caches backfilled in batches for list counts, and pluck for read-only data. It catches N+1s with bullet or prosopite plus strict_loading in development and test, and adds indexes with algorithm: :concurrently and the DDL transaction disabled so large tables keep accepting writes.
Should a Rails app use Solid Queue or Sidekiq?
Background Jobs recommends Solid Queue, the Rails 8 default, or Sidekiq for high throughput, and applies the same rules to both: ID-only payloads, enqueue after the transaction commits and handlers that are safe to run twice. It sizes concurrency to the database pool, separates critical from bulk queues and alerts on oldest-job age rather than queue depth.
How do I install all 9 Ruby on Rails skills at once?
Pass every name to the installer in one command: curl -fsSL https://codexskills.dev/install.sh | sh -s -- ruby-idioms rails-apps active-record-performance rspec-testing background-jobs sqlite-production n-plus-one-queries database-seeding kamal-deploys. Add --project right after -- to put them in the current repository's .agents/skills/ so your team gets them too.
Which Ruby on Rails skill should I try first?
Ruby Idioms is the closest fit for most Ruby on Rails work. Mention it with $ruby-idioms in a prompt to load it on purpose; after that, Codex picks it up on its own whenever a task matches.