# Introduction

> What elelem is, what it is not, and the principles behind it.


**Fast, correct, autonomous. Pick two.**

Every coding agent trades between speed, correctness, and how much it does on its own. elelem gives you the loop and lets you decide the trade: which model, which tools, which checks before a tool runs.

## What elelem is

A coding agent harness written in Ruby. It runs in your terminal, sends your prompt to a model, runs the tools the model asks for, and feeds the results back until the model stops asking.

The core gem, `elelem`, holds the agent loop, the REPL, the plugin loader, and a toolbox with JSON Schema validation. It is under 1,000 lines. It ships with one provider, `stub`, which talks to no model at all, and no tools.

Everything else is a plugin:

- **Providers** connect a model: `elelem-anthropic`, `elelem-openai`, `elelem-ollama`, or `elelem-llama`, which runs a GGUF file inside the elelem process.
- **Tools** are functions the model can call. `elelem-builtins` adds `read`, `write`, and `execute`. `elelem-tools` adds more.
- **Commands** are slash commands you type: `/help`, `/context`, `/reload`.

A plugin is any Ruby file or gem that calls `Elelem.configure`. Drop a `.rb` file in `.agents/plugins/` and it loads on the next start.

## What elelem is not

- **Not a framework.** There is no base class to inherit and no DSL beyond `Elelem.configure`. A tool is a name, a description, a JSON Schema, and a block.
- **Not configured by files.** elelem itself reads no config file. Behavior changes through plugins, command-line options, and environment variables. A few plugins read their own files, such as `elelem-mcp` reading `.agents/mcp.json`.
- **Not a sandbox.** Tools run with your permissions. `elelem-builtins` executes shell commands without asking. Add `elelem-tools` for a confirmation prompt, or write a `before` hook that refuses what you do not want.
- **Not an IDE.** It is a REPL in your terminal and a one-shot `ask` command for scripts.

## Design principles

These come from the core README.

- **Unix philosophy.** Simple, composable, minimal. `elelem ask` reads from a pipe and writes to stdout, so it fits in a shell pipeline.
- **Convention over configuration.** Plugins live in `.agents/plugins/`. Project instructions live in `AGENTS.md`. Models live in `~/.agents/models/`.
- **No defensive code beyond what is necessary.** Errors are caught at a few boundaries (provider calls, tool calls, slash commands, plugin loading) and reported. Nothing else is wrapped.
- **Trust the model.** elelem assumes a capable model that behaves like a responsible engineer. It does not second-guess tool calls unless a plugin asks it to.

## Next

[Install elelem](/docs/installation/), then follow the [quickstart](/docs/quickstart/).


Canonical: https://elelem.sh/docs/introduction/