Mix Format

georgeguimaraes/claude-code-elixir

167 repo stars
Updated April 28, 2026
georgeguimaraes/claude-code-elixir

Auto-format Elixir files with mix format after edits to enforce consistent code style.

About

A hook that automatically formats Elixir files with mix format after edits. Developers use it to keep an Elixir codebase consistently styled without manual formatting.

Runs mix format after edits
Consistent Elixir code style
Automatic on save

Mix Format by the numbers

Data as of Jul 29, 2026 (Skillselion catalog sync)

/plugin marketplace add georgeguimaraes/claude-code-elixir

/plugin install mix-format@claude-code-elixir

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repo stars	★ 167
Last updated	April 28, 2026
Repository	georgeguimaraes/claude-code-elixir ↗

What it does

Auto-format Elixir files with mix format after edits to enforce consistent code style.

README.md

Claude Code Elixir

Claude Code plugins for Elixir development.

Installation

claude plugin marketplace add georgeguimaraes/claude-code-elixir

Install all plugins:

claude plugin install elixir-lsp@claude-code-elixir && \
claude plugin install mix-format@claude-code-elixir && \
claude plugin install mix-compile@claude-code-elixir && \
claude plugin install mix-credo@claude-code-elixir && \
claude plugin install elixir@claude-code-elixir

Prerequisites

Install the expert binary and make sure it's on your PATH. See installation instructions.

Note: mix-format, mix-compile, and mix-credo require bash (Git Bash or WSL on Windows).

Plugins

Overview

Plugin	Type	Description
elixir-lsp	LSP	Language Server with completions, go-to-definition, diagnostics
mix-format	Hook	Auto-format `.ex`/`.exs` files on save
mix-compile	Hook	Compile with `--warnings-as-errors` on save
mix-credo	Hook	Run Credo code quality checks on save
elixir	Skills	BEAM architecture, Phoenix, Ecto, OTP patterns

Tools

elixir-lsp

Elixir Language Server integration powered by Expert.

Feature	Description
Navigation	Go to definition, find references
Completions	With signature help and docs
Diagnostics	Compiler warnings and errors
File types	`.ex`, `.exs`, `.heex`, `.leex`

mix-format

Auto-runs mix format after editing .ex and .exs files.

mix-compile

Auto-runs mix compile --warnings-as-errors after editing .ex files.

Only .ex files (not .exs scripts/tests)
Finds mix.exs by walking up directories
Fails on warnings or errors

mix-credo

Auto-runs mix credo after editing .ex and .exs files to check code quality.

Runs on both .ex and .exs files
Uses project's default Credo configuration
Gracefully skips if Credo is not installed
Fails on code quality issues

Skills

elixir

Paradigm-shifting skills for Elixir, Phoenix, and OTP development. Includes a SessionStart hook that auto-suggests skills when working on Elixir code.

Included skills:

Skill	Use When
`elixir-thinking`	Designing modules, processes, data structures
`phoenix-thinking`	Working with Phoenix, LiveView, PubSub
`ecto-thinking`	Working with Ecto, contexts, schemas
`otp-thinking`	Implementing GenServers, supervisors, Tasks

elixir-thinking

Mental models for writing Elixir — how it differs from OOP.

Concept	Insight
Iron Law	NO PROCESS WITHOUT A RUNTIME REASON
Three dimensions	Behavior, state, mutability are decoupled
Processes	For runtime (state/concurrency/faults), not code organization
"Let it crash"	Means "let it heal" — supervisors restart
Polymorphism	Behaviors → Protocols → Message passing (least to most dynamic)

Sources

phoenix-thinking

Architectural patterns for Phoenix and LiveView.

Concept	Insight
Where to load data	mount/3 by default; handle_params/3 for live navigation (push_patch)
Initial double-load	mount and handle_params both run twice; use connected?/1, assign_async/3, or assign_new/3
Scopes (1.8+)	Security-first authorization threading
PubSub	Scoped topics, `broadcast_from` to avoid self-broadcast
Channel fastlane	Socket state can be stale — re-fetch or include in broadcast

Sources

ecto-thinking

Architectural patterns for Ecto and contexts.

Concept	Insight
Contexts	Bounded domains with their own "dialect"
Cross-context refs	Use IDs, not `belongs_to` associations
Schemas	Multiple changesets per schema, `embedded_schema` for forms
Preloads	Separate vs join — pick based on data shape
pool_count vs pool_size	pool_count = DBConnection pools, pool_size = connections per pool

Sources

Phoenix Contexts Guide
German Velasco - DDD for Phoenix Contexts (ElixirConf 2024)
Ecto Multi-Tenancy Guide

otp-thinking

OTP design patterns and when to use each abstraction.

Concept	Insight
Iron Law	GENSERVER IS A BOTTLENECK BY DESIGN
ETS	Bypasses bottleneck — concurrent reads with `:read_concurrency`
Task.Supervisor	THE pattern for async work (not raw `Task.async`)
Registry + DynamicSupervisor	Named dynamic processes without atom leaks
Broadway vs Oban	External queues vs background jobs — different problems

Sources

Known Issues

elixir-lsp: client/registerCapability workaround. Claude Code's LSP client doesn't respond to client/registerCapability requests that Expert sends during initialization (anthropics/claude-code#32595). The plugin includes a Python wrapper (expert-wrapper) that intercepts these requests and auto-responds so Expert can initialize properly. The wrapper will be removed once the upstream fix lands. Requires Python 3 on PATH.