Claude

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Help make Claude Code write production-ready Elixir, every time.

Claude, not to be confused with the Claude (probably should have picked a better name 😅), is an elixir library, batteries-included integration that helps ensure every line of code Claude writes is checked for proper formatting, compiles without warnings, and follows your project's conventions—automatically.

🚀 Quickstart

New to Claude? Our quickstart guide walks you through a complete setup with real examples.

Installation

# Install Claude
mix igniter.install claude

# That's it! Now Claude:
# ✓ Checks if files need formatting after editing
# ✓ Detects compilation errors immediately
# ✓ Validates code before commits

The Problem

When Claude Code writes Elixir, you often need to:

  • Run mix format manually or prompt Claude to format the file
  • Discover compilation errors only when you run the code or tests

The Solution

This project hooks directly into Claude Code's workflow:

# When Claude writes this code with formatting and compilation issues:
defmodule MyModule do
  def process_user_data(user, _options) do
    {:ok, %{id: user.id, name: user.name, email: user.email, created_at: user.created_at, updated_at: user.updated_at, status: user.status, role: user.role}} # Line too long!
  end

  def calculate_total(items) do # Unused function!
    Enum.reduce(items, 0, fn item, acc -> acc + item.price * item.quantity end)
  end
end

# Claude immediately sees:
# ⚠️ File needs formatting (line too long)
# ❌ Compilation error: unused function `calculate_total/1`

Features

🎯 Smart Hooks

Automatically check formatting, catch compilation errors, validate commits, and more.

→ See Hooks Documentation for details and configuration.

🤖 Sub-agents

Create specialized AI assistants with built-in best practices from your dependencies.

→ See Sub-Agents Documentation for details and examples.

🔌 MCP Server Support

Integrate with Phoenix development tools via Tidewave. MCP servers are configured in .claude.exs and synced to .mcp.json when you run mix claude.install.

→ See MCP Servers Guide for details and configuration.

📚 Best Practices

Usage rules from your dependencies are automatically synced to CLAUDE.md, ensuring Claude follows library-specific best practices.

→ See Usage Rules Guide for how Claude integrates with usage rules.

Installation

Requirements

Install via Igniter

mix igniter.install claude

This will:

  1. Add claude to your dependencies
  2. Generate .claude.exs configuration file
  3. Configure hooks in .claude/settings.json
  4. Generate sub-agents in .claude/agents/
  5. Sync usage rules to CLAUDE.md
  6. Create .mcp.json for MCP servers (if configured)

Configuration File

All Claude settings are managed through .claude.exs:

%{
  hooks: %{
    stop: [:compile, :format],
    post_tool_use: [:compile, :format]
  },
  mcp_servers: [:tidewave],  # For Phoenix projects
  subagents: [...]            # Specialized AI assistants
}

Run mix claude.install after updating to apply changes.

How It Works

This library leverages Claude Code's hook system to intercept file operations:

  1. Claude edits a file → PostToolUse hook triggered
  2. Hook runs Mix tasks → mix format --check-formatted, mix compile --warnings-as-errors
  3. Feedback provided → Claude sees any issues and can fix them
  4. Process repeats → Until the code is production-ready

This happens automatically, without interrupting Claude's workflow.

Documentation

Contributing

We welcome contributions!

# Run tests
mix test

# Format code
mix format

# Run quality checks
mix compile --warnings-as-errors

Support

Roadmap

✅ Recently Added

Mix Task Generator

  • mix claude.gen.subagent - Interactive generator for new sub-agents with:
    • Name validation and formatting
    • Tool selection with warnings
    • Multi-line prompt support
    • Automatic .claude.exs integration

🚀 Coming Soon

Custom Slash Commands

  • /create-subagent - Generate a new sub-agent with guided prompts (wraps mix task)
  • Auto-generate commands in .claude/commands/ during installation

Scoped CLAUDE.md's

  • Directory-specific instructions (e.g., *_web/CLAUDE.md for Phoenix)

More MCP Servers

  • Database tools (PostgreSQL, MySQL, Redis)
  • Testing and documentation servers
  • Auto-configuration based on project dependencies

Dynamic Sub-agents

  • Generate sub-agents for each dependency with context automatically
  • Common workflow templates (LiveView, GraphQL, Testing)

Want to contribute? Open an issue on GitHub!

License

MIT - see LICENSE for details.

Made with ❤️ by the Elixir community