Elixir/Phoenix Template

A minimal CLAUDE.md template for Elixir backend projects using Phoenix and Ecto.

Template (34 lines)

# Project Context

## What This Is
[One sentence describing your project]

## Tech Stack
Elixir 1.17 + Phoenix 1.7 + Ecto + PostgreSQL

## Commands
- `mix phx.server` - Start dev server
- `mix test` - Run tests
- `mix format` - Format code
- `mix credo` - Lint (static analysis)
- `mix dialyzer` - Type checking
- `mix ecto.migrate` - Run migrations

## Architecture
- `/lib/app_web/` - Phoenix controllers, views, templates
- `/lib/app/` - Business logic (contexts)
- `/lib/app/repo.ex` - Ecto repository
- `/priv/repo/migrations/` - Database migrations
- `/test/` - ExUnit tests

## Gotchas
- [Add project-specific gotchas here]
- Example: Use contexts for business logic, not controllers
- Example: Background jobs use Oban - check `/lib/app/workers/`

## Code Style
- Follow Elixir formatter conventions
- Use pattern matching over conditionals
- Keep functions small, use pipelines
- Contexts encapsulate business logic

Usage

1. Copy the template above
2. Save as CLAUDE.md or AGENTS.md in your project root
3. Review and update the Tech Stack to match your project
4. Replace [One sentence describing your project] with your description
5. Replace app with your actual application name
6. Add your project-specific gotchas

Customization Tips

Add gotchas when the AI:

• Puts business logic in controllers instead of contexts
• Forgets about Ecto changesets for validation
• Uses synchronous calls where you need GenServer
• Suggests npm packages instead of Hex packages

Remove sections if:

• You don’t use Credo or Dialyzer
• Your project doesn’t use Phoenix (pure Elixir)
• The architecture is obvious from the folder structure

LiveView Projects

For Phoenix LiveView projects, update the architecture:

## Architecture
- `/lib/app_web/live/` - LiveView modules
- `/lib/app_web/components/` - Function components
- `/lib/app/` - Business logic (contexts)

## Gotchas
- Use `assign/3` and `assign_new/3` for socket assigns
- Handle_event returns `{:noreply, socket}`
- PubSub for real-time updates between clients