Rails AI Agents

A production-ready Claude Code setup for Ruby on Rails development: 19 specialized agents, 26 slash commands (including the SDD kit), 18 skills, 14 rules (11 path-scoped + 3 always-on), 1 MCP, and 6 lifecycle hooks. Drop it into your project and your AI assistant instantly knows Rails conventions, TDD workflows, and production patterns.

Also includes:

• Spec Driven Development (SDD) kit — a full specification-to-implementation pipeline + lightweight mode for bug fixes.
• a separate 37signals-style conventions pack (.claude_37signals/) for teams that prefer rich models + Minitest over the default layered setup.
• Claude Code Extensibility Guide
• and more!

Quick Start

# Most projects: copy the default .claude/ directory into your Rails project
cp -r .claude/ /path/to/your-rails-app/.claude/

If you want...	Copy
Default setup (layered architecture, RSpec, Pundit, PostgreSQL)	.claude/
37signals-style conventions (rich models, concerns, Minitest)	.claude_37signals/ instead of .claude/
Spec Driven Development commands (/sdd:*, /sdd-change:*)	.specify/ in addition to your chosen .claude* pack
Statusline	statusline/
Sentry integration	mcp/sentry_monitor/

.specify/ is optional unless you want the SDD workflow. .claude_37signals/ is currently a conventions pack (instructions, agents, skills, rules, settings), while the slash-command set documented below lives under .claude/commands/.

What's Inside

Agents (.claude/agents/)

19 specialist agents, each with permissionMode: acceptEdits, memory: project, maxTurns limits, and WHEN/WHEN NOT descriptions for auto-delegation.

Agent	Domain	Model
model-agent	ActiveRecord models, validations, associations, scopes	sonnet
controller-agent	Thin RESTful controllers, strong params, Pundit	sonnet
service-agent	Service objects, Result pattern, SOLID	sonnet
migration-agent	Safe, reversible database migrations	haiku
policy-agent	Pundit authorization policies	sonnet
form-agent	Multi-model forms, wizard forms	sonnet
query-agent	Complex queries, N+1 prevention	sonnet
presenter-agent	View logic separation with SimpleDelegator	sonnet
viewcomponent-agent	Reusable, tested UI components	sonnet
job-agent	Background jobs with Solid Queue	sonnet
mailer-agent	ActionMailer with previews and templates	sonnet
turbo-agent	Turbo Frames, Streams, Drive	sonnet
stimulus-agent	Stimulus controllers	sonnet
tailwind-agent	Tailwind CSS styling	sonnet
rspec-agent	RSpec tests	sonnet
implementation-agent	TDD GREEN phase orchestrator (worktree isolation)	sonnet
tdd-refactoring-agent	TDD REFACTOR phase	sonnet
lint-agent	RuboCop linting and auto-correction	haiku
database-reviewer	PostgreSQL query optimization, schema design, performance	sonnet

Commands (.claude/commands/)

26 slash commands across 4 namespaces. See also SDD commands below.

Standalone (7)

Command	Purpose
/feature-spec	Structured interview to write a complete spec with Gherkin scenarios
/feature-spec-review	Scores specs, identifies gaps, generates missing scenarios
/feature-plan	Converts spec into TDD implementation plan with PR breakdown
/feature-tdd-implementation	Guides full Red-Green-Refactor TDD workflow
/frame-problem	Reframes vague requests into clear problems
/prompt-improver	Scores and rewrites vague prompts into specific, actionable ones
/catchup	"Welcome back" report on a feature branch — commits, authors, themes, and risks since the dev's last contribution

Sentry Commands (.claude/commands/sentry/)

Command	Purpose
/sentry:monitor	Check for new production errors and propose fixes
/sentry:fix-error	Launch a background agent in an isolated worktree to fix a Sentry error
/sentry:fix-status	List all active Sentry fix branches and their status
/sentry:report	Generate a markdown summary of Sentry error status for standups or PRs
/sentry:resolve	Resolve, ignore, or reopen a Sentry issue after a fix is deployed

Skills (.claude/skills/)

18 skills with reference docs. Two patterns: task skills (user-invocable workflows) and knowledge skills (auto-loaded conventions).

Skill	Type	Purpose
code-review	Task	SOLID analysis, N+1 detection, anti-patterns (read-only)
security-audit	Task	OWASP Top 10 audit with Brakeman (runs with opus)
accessibility-review	Task	WCAG 2.2 AA audit with axe-core / Lighthouse / Pa11y, progressive-disclosure references for ARIA patterns and Rails snippets (runs with opus)
codex-review	Task	Independent second opinion from OpenAI Codex CLI on plans, diffs, or specs
dependabot-review	Task	Reviews Dependabot gem upgrade PRs for breaking changes and merge readiness
behavioral-guidelines	Knowledge	Guidelines to reduce common LLM coding mistakes (auto-loaded)
rails-architecture	Knowledge	Layered architecture decisions (runs with opus)
postgres-patterns	Knowledge	PostgreSQL query optimization, schema design, indexing, and security
authentication-flow	Knowledge	Rails 8 built-in authentication
caching-strategies	Knowledge	Fragment, Russian doll, low-level caching
performance-optimization	Knowledge	N+1 detection, query optimization
extraction-timing	Knowledge	When and how to extract services, queries, concerns
action-cable-patterns	Knowledge	WebSocket real-time features
active-storage-setup	Knowledge	File uploads and variants
api-versioning	Knowledge	RESTful API design
i18n-patterns	Knowledge	Internationalization
solid-queue-setup	Knowledge	Background job configuration
rails-concern	Knowledge	Shared behavior with concerns

Rules (.claude/rules/)

14 rules: 11 path-scoped (auto-load when Claude works on matching files) and 3 always-on.

Path-scoped (11)

Rule	Scoped to
models.md	app/models/**, spec/models/**, spec/factories/**
controllers.md	app/controllers/**, spec/requests/**
services.md	app/services/**, spec/services/**
queries.md	app/queries/**, spec/queries/**
policies.md	app/policies/**, spec/policies/**
jobs.md	app/jobs/**, spec/jobs/**
mailers.md	app/mailers/**, spec/mailers/**
migrations.md	db/migrate/**, db/schema.rb
views.md	app/views/**, app/components/**, app/presenters/**
testing.md	spec/**
anti-patterns.md	app/**/*.rb, spec/**/*.rb

Always-on (3)

Rule	Purpose
principles.md	KISS, DRY, YAGNI, SRP, and Rails architecture principles
cli.md	Rails CLI commands reference (dev server, tests, db, generators)
cli-tools.md	Preferred CLI tools: rg over grep, fd over find

Hooks (.claude/settings.json)

Hook	Event	What it does
SessionStart	Session begins	Injects project context (branch, Ruby/Rails version, pending migrations)
PostToolUse	After Edit/Write	Auto-formats Ruby files with RuboCop
PreToolUse	Before Bash	Blocks destructive commands (rm -rf, DROP TABLE, force push to main)
TaskCompleted	Task marked done	Quality gate: reminds to run tests and linting
Stop	Response ends	Desktop notification

Settings

• Agent Teams enabled (CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS)
• JSON Schema for editor autocomplete
• Smart model routing: opus for architecture/security, sonnet for coding, haiku for linting

Statusline (statusline/)

A two-line statusline that surfaces the signals you actually need while working: git state, model, and usage budgets.

• Line 1 — current branch (with a ✗ marker when the working tree is dirty), model name, and reasoning effort level
• Line 2 — context window usage, 5-hour rate-limit usage with reset countdown, 7-day rate-limit usage with reset countdown
• Color-coded thresholds — green under 50%, yellow 50–79%, red at 80%+ so you can see budget pressure at a glance

Wire it up in ~/.claude/settings.json:

{
  "statusLine": {
    "type": "command",
    "command": "bash /absolute/path/to/statusline/statusline.sh"
  }
}

Spec Driven Development (SDD) Kit

A structured specification-to-implementation pipeline powered by 11 slash commands. SDD enforces a disciplined workflow: define what you're building before writing code, validate requirements quality, then implement from a task plan.

SDD Commands (.claude/commands/sdd/)

Command	Purpose
/sdd:constitution	Create or update the project constitution — core principles and governance rules
/sdd:specify	Generate a feature specification from a natural language description
/sdd:clarify	Ask up to 5 targeted questions to reduce ambiguity in the spec
/sdd:spec-review	Adversarial review of the spec from security, performance, edge-case, scalability, and compliance perspectives
/sdd:checklist	Generate a requirements quality checklist
/sdd:plan	Create a technical implementation plan with research, data model, and contracts
/sdd:tasks	Break the plan into dependency-ordered, executable tasks organized by user story
/sdd:analyze	Read-only consistency analysis across spec, plan, and tasks
/sdd:implement	Execute the task plan phase-by-phase with progress tracking
/sdd:implement-subagents	Same as implement, but spawns a fresh-context subagent per task to prevent context rot on large features
/sdd:validate	Post-implementation drift detection — verifies code implements what the spec promises (4-layer hybrid, no annotations needed)

SDD Workflow

/sdd:constitution                  # 1. Define project principles (once)
/sdd:specify user authentication   # 2. Write the feature spec
/sdd:clarify                       # 3. Resolve ambiguities (optional)
/sdd:spec-review                   # 4. Adversarial review from 5 perspectives (optional)
/sdd:checklist security            # 5. Validate requirements quality (optional)
/sdd:plan                          # 6. Generate technical plan + data model
/sdd:tasks                         # 7. Break into ordered tasks
/sdd:analyze                       # 8. Cross-artifact consistency check
/sdd:implement                     # 9. Execute tasks with verification
# Or for large features:
/sdd:implement-subagents           # 9. Fresh-context subagent per task (prevents context rot)
/sdd:validate                      # 10. Verify implementation matches spec (post-implementation)

Each command hands off to the next via suggested prompts. The pipeline creates a specs/<branch-name>/ directory with all artifacts:

specs/001-user-auth/
├── spec.md           # Feature specification (/sdd:specify)
├── plan.md           # Implementation plan (/sdd:plan)
├── research.md       # Technical research & decisions (/sdd:plan)
├── data-model.md     # Entity definitions (/sdd:plan)
├── quickstart.md     # Integration scenarios (/sdd:plan)
├── contracts/        # Route and API contracts (/sdd:plan)
├── tasks.md          # Executable task list (/sdd:tasks)
├── checklists/       # Requirements quality checklists (/sdd:checklist)
└── validation-report.md  # Post-implementation drift report (/sdd:validate)

SDD Infrastructure (.specify/)

The .specify/ directory contains the scaffolding that powers SDD commands. It is optional for normal prompting; you only need it for the /sdd:* and /sdd-change:* workflows:

• templates/ — Markdown templates for specs, plans, tasks, checklists, constitutions, and agent context files
• scripts/bash/ — Shell scripts for branch creation, prerequisite checking, plan setup, and agent context updates
• memory/ — Persistent project state (constitution, lessons learned across features)
• init-options.json — Configuration (branch numbering mode, AI agent type)

SDD supports extensibility via .specify/extensions.yml for before/after hooks on any command, template overrides in .specify/templates/overrides/, and presets in .specify/presets/.

Key SDD Concepts

• Constitution — Non-negotiable project principles validated at every planning gate
• Lessons Learned — Cross-feature learnings accumulate in .specify/memory/lessons-learned.md and feed into future planning and implementation
• Adversarial Spec Review — /sdd:spec-review challenges the spec from security, performance, edge-case, scalability, and compliance perspectives before planning begins
• Specs are stakeholder-facing — No implementation details; focus on WHAT and WHY
• Checklists are "unit tests for English" — They validate requirements quality, not implementation correctness
• Tasks organized by user story — Each story is independently implementable and testable (MVP-first)
• Fresh-context implementation — /sdd:implement-subagents spawns a clean subagent per task, preventing context rot on large features
• Post-implementation validation — /sdd:validate uses a 4-layer hybrid approach (structural scan, test mapping, AI semantic analysis, acceptance test generation) to verify the code matches the spec — works on day one, no code annotations needed

SDD Small-Change (Lightweight Mode)

For bug fixes and small features that don't need the full SDD ceremony. Three commands, no plan, no checklists, no analysis — just specify, task, implement.

Commands (.claude/commands/sdd-change/)

Command	Purpose
/sdd-change:specify	Create a minimal change spec (problem, fix, acceptance criteria, files affected)
/sdd-change:tasks	Generate a flat 3-8 task list from the change spec
/sdd-change:implement	Execute tasks sequentially with validation

Workflow

/sdd-change:specify Fix login timeout — sessions expire after 5min instead of 30
/sdd-change:tasks
/sdd-change:implement

When to Use Which

Situation	Use
Bug fix, patch, tweak	/sdd-change:specify
New feature, multi-story epic	/sdd:specify
Refactor touching 1-3 files	/sdd-change:specify
Refactor touching 6+ files	/sdd:specify

The lightweight pipeline warns you if your change looks too complex (>3 acceptance criteria or >6 files affected) and suggests switching to the full pipeline.

MCP Servers (mcp/)

Custom MCP servers that extend Claude Code with external integrations.

Server	Purpose	Docs
sentry_monitor	Exposes Sentry production errors as Claude Code tools — query issues, map stack traces to local files, detect new errors with persistent state tracking, PII redaction by default	README

Documentation

Document	Purpose
Your First SDD Feature	Step-by-step onboarding walkthrough for new developers using the SDD kit
SDD Team Scalability Analysis	Risks, gaps, and roadmap for scaling SDD to a 30-developer team
Rails Development Principles	Universal software principles, Rails doctrine, modern Rails 8 architecture, testing, security, and performance
Prompt Engineering for Claude Code	Writing effective prompts for Claude Code in web development, with Rails-specific patterns
Claude Code Extensibility Guide	All extension mechanisms: CLAUDE.md, skills, hooks, subagents, Agent Teams, MCP servers, and plugins
Claude Code Frontmatter Reference	YAML frontmatter syntax for configuring agents, skills, and commands in .claude/ files
MCP Servers for Rails	Extending Claude Code with Model Context Protocol servers for Rails, databases, and APIs
PRD Best Practices	Writing effective Product Requirements Documents in agile, AI-in-the-loop environments
Technical Design Documents	TDDs, ADRs, and Engineering RFCs for agentic SDLC teams
Design Specifications	UI/UX design specs and API specifications (OpenAPI) for frontend/backend contracts
Specification Document Hierarchy	Reference map showing which documents answer which core questions
AI Terminology Glossary	289 AI/ML terms across 25 categories — also available as a browsable HTML version

License

MIT