---
title: Reference
sidebarTitle: "Reference index"
description: "Exact contracts: CLI, settings, environment variables, keybindings, tools, session format, provider, model, compaction, extension, SDK, RPC, and TUI references."
---

# Reference

Look up exact commands, settings, types, and tool contracts here. For a walkthrough, start with [Guides](/guides) or [Build with Atomic](/build).

## Everyday contracts

- [CLI reference](/reference/cli) — every command, flag, argument, and environment variable.
- [Settings](/settings) — every settings field, with defaults and constraints.
- [Environment variables](/environment-variables) — Atomic/Pi aliases, provider credentials, and bash session metadata.
- [Keybindings](/keybindings) — default shortcuts and custom keybinding actions.
- [Built-in tools](/tools), including [hashline editing](/tools#edit).
- [MCP Servers](/mcp-servers) for server configuration, tool discovery, and authentication.

## Domain contracts

- [Provider reference](/providers/reference) — stop reasons and credential resolution order.
- [Model configuration reference](/models/reference) — provider and model fields, overrides, variants, and API compatibility.
- [Compaction reference](/compaction/reference) — parameters, persistence, hooks, formats, settings, and historical formats.
- [Extension API reference](/extensions/api-reference) — `ExtensionContext`, `ExtensionCommandContext`, and `ExtensionAPI` methods.
- [Extension events](/extensions/events) — every event and its payload.
- [SDK API reference](/sdk/reference) — options, loaders, return values, run modes, and exports.
- [RPC protocol](/rpc/protocol) — commands, events, types, and errors.
- [TUI API reference](/tui/reference) — component, focusable, input, and rendering contracts.
- [Session format](/session-format) — the JSONL session file format, entry types, and `SessionManager` API.
- [Theme reference](/themes/reference) — theme file format, color tokens, and color values.
- [Skill reference](/skills/reference) — `SKILL.md` frontmatter and validation.
- [Subagent reference](/subagents/reference) — fallback models and reasoning levels.
- [Intercom reference](/intercom/reference) — the `intercom` tool contract and settings.
- [Package reference](/packages/reference) — filtering, scope, and deduplication.
- [Provider API reference](/custom-provider/api-reference) — provider config and model definition contracts.
- [Workflow API reference](/workflows/api-reference) — workflow, stage, and context contracts.

## Platform setup

- [Windows](/windows)
- [Termux on Android](/termux)
- [tmux](/tmux)
- [Terminal setup](/terminal-setup)
- [Shell aliases](/shell-aliases)

## Development

- [Development](/development) - local setup, project structure, and debugging.