<essential_principles>

Core Philosophy

"The best code is the code you don't write. The second best is the code that's obviously correct."

Vanilla Rails is plenty:

• Rich domain models over service objects

• CRUD controllers over custom actions

• Concerns for horizontal code sharing

• Records as state instead of boolean columns

• Database-backed everything (no Redis)

• Build solutions before reaching for gems

What they deliberately avoid:

• devise (custom ~150-line auth instead)

• pundit/cancancan (simple role checks in models)

• sidekiq (Solid Queue uses database)

• redis (database for everything)

• view_component (partials work fine)

• GraphQL (REST with Turbo sufficient)

• factory_bot (fixtures are simpler)

• rspec (Minitest ships with Rails)

• Tailwind (native CSS with layers)

Development Philosophy:

• Ship, Validate, Refine - prototype-quality code to production to learn

• Fix root causes, not symptoms

• Write-time operations over read-time computations

• Database constraints over ActiveRecord validations </essential_principles>

• Controllers - REST mapping, concerns, Turbo responses, API patterns

• Models - Concerns, state records, callbacks, scopes, POROs

• Views & Frontend - Turbo, Stimulus, CSS, partials

• Architecture - Routing, multi-tenancy, authentication, jobs, caching

• Testing - Minitest, fixtures, integration tests

• Gems & Dependencies - What to use vs avoid

• Code Review - Review code against DHH style

• General Guidance - Philosophy and conventions

Specify a number or describe your task.

After reading relevant references, apply patterns to the user's code.

<quick_reference>

Naming Conventions

Verbs: card.close , card.gild , board.publish (not set_style methods)

Predicates: card.closed? , card.golden? (derived from presence of related record)

Concerns: Adjectives describing capability (Closeable , Publishable , Watchable )

Controllers: Nouns matching resources (Cards::ClosuresController )

Scopes:

• chronologically , reverse_chronologically , alphabetically , latest

• preloaded (standard eager loading name)

• indexed_by , sorted_by (parameterized)

• active , unassigned (business terms, not SQL-ish)

REST Mapping

Instead of custom actions, create new resources:

POST /cards/:id/close → POST /cards/:id/closure DELETE /cards/:id/close → DELETE /cards/:id/closure POST /cards/:id/archive → POST /cards/:id/archival

Ruby Syntax Preferences

Symbol arrays with spaces inside brackets

before_action :set_message, only: %i[ show edit update destroy ]

Private method indentation

private def set_message @message = Message.find(params[:id]) end

Expression-less case for conditionals

case when params[:before].present? messages.page_before(params[:before]) else messages.last_page end

Bang methods for fail-fast

@message = Message.create!(params)

Ternaries for simple conditionals

@room.direct? ? @room.users : @message.mentionees

Key Patterns

State as Records:

Card.joins(:closure) # closed cards Card.where.missing(:closure) # open cards

Current Attributes:

belongs_to :creator, default: -> { Current.user }

Authorization on Models:

class User < ApplicationRecord def can_administer?(message) message.creator == self || admin? end end

</quick_reference>

<reference_index>

Domain Knowledge

All detailed patterns in references/ :

File Topics

controllers.md REST mapping, concerns, Turbo responses, API patterns, HTTP caching

models.md Concerns, state records, callbacks, scopes, POROs, authorization, broadcasting

frontend.md Turbo Streams, Stimulus controllers, CSS layers, OKLCH colors, partials

architecture.md Routing, authentication, jobs, Current attributes, caching, database patterns

testing.md Minitest, fixtures, unit/integration/system tests, testing patterns

gems.md What they use vs avoid, decision framework, Gemfile examples

</reference_index>

<success_criteria> Code follows DHH style when:

• Controllers map to CRUD verbs on resources

• Models use concerns for horizontal behavior

• State is tracked via records, not booleans

• No unnecessary service objects or abstractions

• Database-backed solutions preferred over external services

• Tests use Minitest with fixtures

• Turbo/Stimulus for interactivity (no heavy JS frameworks)

• Native CSS with modern features (layers, OKLCH, nesting)

• Authorization logic lives on User model

• Jobs are shallow wrappers calling model methods </success_criteria>

Important Disclaimers:

• LLM-generated guide - may contain inaccuracies

• Code examples from Fizzy are licensed under the O'Saasy License

• Not affiliated with or endorsed by 37signals