ctx

Ferramenta CLI para compactar contexto de código antes de enviar ao Claude — economize tokens, expanda o que cabe na janela. → Leia em Português · → Read in English

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ctx — anti-tokens CLI para Claude Code

Analise seu projeto localmente. Envie ao Claude resumos densos, não arquivos brutos.

Status: alpha — em desenvolvimento ativo. Interfaces podem mudar.

Por que usar

Cada token que o Claude lê tem custo e consome janela de contexto. Ao trabalhar em projetos grandes, o Claude frequentemente gasta milhares de tokens apenas lendo arquivos para construir um modelo mental antes de fazer qualquer trabalho real.

ctx roda localmente, analisa seu projeto com ferramentas especializadas por linguagem (Roslyn para C#, tree-sitter para TypeScript), e emite resumos compactos em markdown que dão ao Claude tudo que ele precisa em uma fração dos tokens.

Benchmark

Teste real: análise de "o que preciso mudar para adicionar uma feature" em projeto em produção. Ambas as sessões iniciadas com /clear — condições equivalentes.

Teste	Consumo de janela de contexto
Sem ctx	+7%
Com ctx	+3%

Economia: 57%. Em sessões longas de desenvolvimento, onde o Claude faz a mesma exploração várias vezes ao longo da conversa, essa economia acumula.

Instalação

1. Instale o Go Baixe em https://go.dev/dl/ e siga o instalador. Requer Go 1.22+.

2. Instale o ctx

go install github.com/ricarneiro/ctx/cmd/ctx@latest

3. Verifique

ctx --version

Uso

# Contexto git: commits recentes, status, info da branch
ctx git

# Detectar stack e emitir visão geral do projeto
ctx auto project

# Estrutura de projeto C# (requer .NET SDK)
ctx csharp project

# Outline de arquivo C#: tipos, métodos, assinaturas
ctx csharp outline src/MyService.cs

# Listar erros de compilação
ctx csharp errors

Toda saída é markdown UTF-8 no stdout. Redirecione onde precisar:

ctx csharp project | clip     # Windows
ctx csharp project | pbcopy   # macOS

Integrando com Claude Code

Para que o Claude Code use o ctx automaticamente, adicione o ctx ao PATH do Windows e inclua as instruções abaixo no CLAUDE.md do seu projeto.

1. Adicionar ctx ao PATH no Windows

1. Copie o ctx.exe para uma pasta fixa (ex: C:\tools\ctx\)
2. Abra Configurações do Sistema → Variáveis de Ambiente
3. Em "Variáveis do sistema", selecione Path → Editar
4. Clique em Novo e adicione C:\tools\ctx\
5. Confirme com OK e reinicie o terminal

2. Adicionar ao CLAUDE.md do projeto

Crie ou edite o arquivo CLAUDE.md na raiz do seu projeto e inclua:

# Project instructions

## `ctx` — compact code analysis tool (use to save tokens)

This project has `ctx` in PATH. It produces compact markdown summaries of code structure.

### When to use `ctx` (saves tokens)

- **Understanding the whole project:** run `ctx csharp project` instead of exploring files one by one.
- **Understanding a large file (100+ lines):** run `ctx csharp outline <file>` before reading the full file. Only read the full file if you need method body details.
- **Checking build errors:** run `ctx csharp errors` instead of `dotnet build` (filtered output, 90% smaller).
- **Understanding git state:** run `ctx git` instead of running multiple git commands.

### When NOT to use `ctx`

- If you already know which specific small file to read, just read it directly.
- If you need to see method body logic, read the file — `ctx outline` only shows signatures.
- For simple `Search()` by pattern across files, search is already efficient.

### Commands

```
ctx csharp project           # solution overview: projects, refs, packages, structure
ctx csharp outline <file.cs> # class/method signatures without bodies (~85% smaller)
ctx csharp errors            # dotnet build filtered to errors + top warnings (~90% smaller)
ctx git                      # branch, status, recent commits, diff summary
```

### Rule of thumb

Ask yourself: "Am I about to read multiple files to understand structure?" If yes → `ctx` first. If you just need one specific file → read it directly.

Contribuindo

Contribuições são bem-vindas. Clone o repositório, faça suas alterações e abra um Pull Request. Para mudanças grandes, abra uma issue primeiro para alinhar o escopo.

git clone https://github.com/ricarneiro/CTX.git
cd CTX
go build -o ctx.exe ./cmd/ctx

Licença

MIT — veja LICENSE.

---

ctx — anti-tokens CLI for Claude Code

Analyze your codebase locally. Feed Claude dense summaries, not raw files.

Status: alpha — under active development. Interfaces will change.

Why

Every token Claude reads costs money and burns context window. When working on a large codebase, Claude often spends thousands of tokens just reading files to build a mental model before doing any actual work.

ctx runs locally, analyzes your project with language-aware tools (Roslyn for C#, tree-sitter for TypeScript), and emits compact markdown summaries that give Claude everything it needs in a fraction of the tokens.

Benchmark

Real test: analyzing "what needs to change to add a feature" on a production project. Both sessions started with /clear — equivalent conditions.

Test	Context window usage
Without ctx	+7%
With ctx	+3%

Savings: 57%. In long development sessions, where Claude performs the same exploration repeatedly throughout a conversation, the savings compound.

Installation

1. Install Go Download from https://go.dev/dl/ and run the installer. Requires Go 1.22+.

2. Install ctx

go install github.com/ricarneiro/ctx/cmd/ctx@latest

3. Verify

ctx --version

Usage

# Git context: recent commits, status, branch info
ctx git

# Auto-detect stack and emit project overview
ctx auto project

# C# project structure (requires .NET SDK)
ctx csharp project

# C# file outline: types, methods, signatures
ctx csharp outline src/MyService.cs

# List compilation errors
ctx csharp errors

All output is UTF-8 markdown on stdout. Pipe it where you need it:

ctx csharp project | pbcopy   # macOS
ctx csharp project | clip     # Windows

Integrating with Claude Code

To have Claude Code use ctx automatically, add ctx to your Windows PATH and include the instructions below in your project's CLAUDE.md.

1. Add ctx to PATH on Windows

1. Copy ctx.exe to a fixed folder (e.g. C:\tools\ctx\)
2. Open System Settings → Environment Variables
3. Under "System variables", select Path → Edit
4. Click New and add C:\tools\ctx\
5. Confirm with OK and restart your terminal

2. Add to your project's CLAUDE.md

Create or edit CLAUDE.md at the root of your project and include:

# Project instructions

## `ctx` — compact code analysis tool (use to save tokens)

This project has `ctx` in PATH. It produces compact markdown summaries of code structure.

### When to use `ctx` (saves tokens)

- **Understanding the whole project:** run `ctx csharp project` instead of exploring files one by one.
- **Understanding a large file (100+ lines):** run `ctx csharp outline <file>` before reading the full file. Only read the full file if you need method body details.
- **Checking build errors:** run `ctx csharp errors` instead of `dotnet build` (filtered output, 90% smaller).
- **Understanding git state:** run `ctx git` instead of running multiple git commands.

### When NOT to use `ctx`

- If you already know which specific small file to read, just read it directly.
- If you need to see method body logic, read the file — `ctx outline` only shows signatures.
- For simple `Search()` by pattern across files, search is already efficient.

### Commands

```
ctx csharp project           # solution overview: projects, refs, packages, structure
ctx csharp outline <file.cs> # class/method signatures without bodies (~85% smaller)
ctx csharp errors            # dotnet build filtered to errors + top warnings (~90% smaller)
ctx git                      # branch, status, recent commits, diff summary
```

### Rule of thumb

Ask yourself: "Am I about to read multiple files to understand structure?" If yes → `ctx` first. If you just need one specific file → read it directly.

Contributing

Contributions are welcome. Clone the repository, make your changes, and open a Pull Request. For large changes, open an issue first to align on scope.

git clone https://github.com/ricarneiro/CTX.git
cd CTX
go build -o ctx.exe ./cmd/ctx

License

MIT — see LICENSE.