Lunar

Lunar is a terminal-based coding harness written in Rust and released under the MIT license by Guilherme Salazar. It connects to any OpenAI Chat Completions-compatible endpoint and exposes four primitive tools to the model—read, write, edit, and bash—letting the AI act on a codebase without prescribing a fixed workflow. The project is early-stage software targeting macOS and Linux.

What It Is

Lunar sits in the category of agent harnesses: minimal scaffolding that wires a language model to a local development environment. Rather than building opinionated workflows or multi-step pipelines, it hands the model a small, composable toolset and gets out of the way. The README describes it as "simple and fast like Pi, but using Lua for extensions," signaling a deliberate minimalism over feature richness.

Core Tool Model

The four tools Lunar exposes cover the essential file-system and shell operations a coding agent needs:

• read – read file contents into context
• write – write or create files
• edit – make targeted edits to existing files
• bash – execute shell commands

This flat, four-tool surface area is intentional. The harness does not impose a planning loop, a task queue, or a memory layer—those concerns are left to the model or to future Lua extensions.

Configuration and Provider Support

Lunar supports any OpenAI Chat Completions-compatible endpoint via environment variables (LUNAR_API_KEY, LUNAR_BASE_URL, LUNAR_MODEL) for quick starts, or a persistent ~/.lunar/init.lua file for full configuration. The Lua config lets users define named models, providers, context window sizes, and API types (Completions, Responses, or Messages). The /login TUI command supports xAI device-code auth or masked API key storage; /logout removes stored credentials. The README notes that Completions and Responses APIs currently send; Messages support is planned.

Mission and Context System

Lunar organizes work into "missions." The -c flag continues the latest mission for the current directory, -m opens the mission log, and passing a date (e.g., lunar -m 2026-08-19) opens that day's log. Lunar automatically includes AGENTS.md, CONTEXT.md, and skill summaries from .agents/skills/*/SKILL.md in its context window, giving teams a lightweight convention for injecting project-specific instructions.

Lua Extension Architecture

Lua extensions are planned but not yet implemented. The README shows a forward-looking API example where the local bash tool could be replaced with execution inside a remote Runta runtime, illustrating the intended extensibility model. This design means the harness itself stays small while power users can swap or augment tools via scripts.

Current Status

Lunar is explicitly described in the README as "early software for macOS and Linux." The repository was created on 2026-08-19 and last pushed on 2026-08-22, making it a very new project. Lua extensions are not yet implemented. The project has 10 stars and 0 forks at the time of indexing. Installation is available via Homebrew (brew install --HEAD gszr/taps/lunar) or Cargo (cargo install --git https://github.com/gszr/lunar).