Tetra

Fix typos, summarize, translate, and more.

Tetra lives in your menu bar. Select text in any app, open Tetra, pick a command from a list. Tetra grabs your selection, runs the command, and replaces the selection with the result.

Commands live in ~/.config/tetra/commands/. They're either small shell scripts or AI prompt files. An HTTP API is also available for driving Tetra from other apps and scripts.

Commands

Tetra ships with none by default — you add the ones you want. Drop files into ~/.config/tetra/commands/; the filename becomes the command name (extension stripped). Uppercase.sh shows up as Uppercase, Fix With AI.prompt.md as Fix With AI.

Need inspiration? There's a folder of ready-to-use examples — case conversions, wrapping, escaping, AI translation and grammar fixes, and more.

Shell scripts

Any executable language works — bash, Python, Ruby, JavaScript. The script reads the original text from stdin and prints the transformed text to stdout.

# Uppercase.sh
tr '[:lower:]' '[:upper:]'

AI prompts

For anything trickier, write a .prompt.md file. Tetra sends the prompt to a language model and replaces your selection with the reply. Inside the prompt, {{text}} becomes the selected text.

Connecting a language model

Tetra speaks the OpenAI API format, so anything compatible works — OpenAI, Groq, OpenRouter, local Ollama, LM Studio, etc. List your models under llms in ~/.config/tetra/config.json:

{
  "server": { "port": 24100 },
  "llms": {
    "groq_llama": {
      "baseUrl": "https://api.groq.com/openai/v1",
      "apiKey": "gsk_...",
      "model": "llama-3.3-70b-versatile"
    }
  }
}

HTTP API

Tetra runs a local server at http://localhost:24100:

curl http://localhost:24100/commands
# ["Fix With AI", "Lowercase", "Trim", "Uppercase"]

curl -X POST http://localhost:24100/transform \
  -H "Content-Type: application/json" \
  -d '{"command": "Uppercase", "text": "hello"}'
# {"result": "HELLO"}

On first launch, Tetra asks for Accessibility access — required to grab text from other apps.

Install

Download Tetra.zip, unzip, and drag Tetra.app to /Applications.

Requires macOS 15 (Sequoia) or later.