Atomic fork note: this package is vendored from pi's packages/coding-agent and rebranded via package.json as @bastani/atomic, CLI binary atomic, piConfig.name = "atomic", and piConfig.configDir = ".atomic".

Atomic is a minimal terminal coding harness. Adapt Atomic to your workflows, not the other way around, without having to fork and modify Atomic internals. Extend it with TypeScript Extensions, Skills, Prompt Templates, and Themes. Put your extensions, skills, prompt templates, and themes in Atomic Packages and share them with others via npm or git.

Atomic ships with powerful defaults plus first-party bundled extensions for workflows, subagents, MCP, web access, and intercom. You can still adapt or replace any workflow by writing extensions, skills, prompt templates, themes, or Atomic packages that match how you work.

Atomic runs in four modes: interactive, print or JSON, RPC for process integration, and an SDK for embedding in your own apps. See openclaw/openclaw for a real-world SDK integration.

Share your OSS coding agent sessions

If you use Atomic for open source work, consider sharing coding-agent sessions using an Atomic-owned workflow or your team's dataset process.

Public OSS session data can help improve models, prompts, tools, and evaluations using real development workflows. Upstream Pi session-sharing resources may still be useful for historical context, but they are not the primary Atomic publication path.

Table of Contents

• Quick Start
• Providers & Models
• Interactive Mode
  • Editor
  • Commands
  • Keyboard Shortcuts
  • Message Queue
• Sessions
  • Branching
  • Compaction
• Settings
• Context Files
• Customization
  • Prompt Templates
  • Skills
  • Extensions
  • Themes
  • Atomic Packages
• Programmatic Usage
• Philosophy
• CLI Reference

Quick Start

bun install -g @bastani/atomic

Or with npm:

npm install -g @bastani/atomic

Authenticate with an API key:

export ANTHROPIC_API_KEY=sk-ant-...
atomic

Or use your existing subscription:

atomic
/login  # Then select provider

Then just talk to Atomic. By default, Atomic gives the model four tools: read, write, edit, and bash. The model uses these to fulfill your requests. Add capabilities via skills, prompt templates, extensions, or Atomic packages.

Platform notes: Windows | Termux (Android) | tmux | Terminal setup | Shell aliases

Providers & Models

For each built-in provider, Atomic maintains a list of tool-capable models, updated with every release. Authenticate via subscription (/login) or API key, then select any model from that provider via /model (or CTRL+L).

Subscriptions:

• Anthropic Claude Pro/Max
• OpenAI ChatGPT Plus/Pro (Codex)
• GitHub Copilot

API keys:

• Anthropic
• OpenAI
• Azure OpenAI
• DeepSeek
• Google Gemini
• Google Vertex
• Amazon Bedrock
• Mistral
• Groq
• Cerebras
• Cloudflare AI Gateway
• Cloudflare Workers AI
• xAI
• OpenRouter
• Vercel AI Gateway
• ZAI
• OpenCode Zen
• OpenCode Go
• Hugging Face
• Fireworks
• Together AI
• Kimi For Coding
• MiniMax
• Xiaomi MiMo
• Xiaomi MiMo Token Plan (China)
• Xiaomi MiMo Token Plan (Amsterdam)
• Xiaomi MiMo Token Plan (Singapore)

See docs/providers.md for detailed setup instructions.

Custom providers & models: Add providers via ~/.atomic/agent/models.json (legacy ~/.pi/agent/models.json also works) if they speak a supported API (OpenAI, Anthropic, Google). For custom APIs or OAuth, use extensions. See docs/models.md and docs/custom-provider.md.

Interactive Mode

The interface from top to bottom:

• Startup header - Shows shortcuts (/hotkeys for all), loaded AGENTS.md files, prompt templates, skills, and extensions
• Messages - Your messages, assistant responses, tool calls and results, notifications, errors, and extension UI
• Editor - Where you type; border color indicates thinking level
• Footer - Working directory, session name, total token/cache usage, cost, context usage, current model

The editor can be temporarily replaced by other UI, like built-in /settings or custom UI from extensions (e.g., a Q&A tool that lets the user answer model questions in a structured format). Extensions can also replace the editor, add widgets above/below it, a status line, custom footer, or overlays.

Editor

| Feature | How | |---------|-----| | File reference | Type @ to fuzzy-search project files | | Path completion | Tab to complete paths | | Multi-line | SHIFT+Enter (or CTRL+Enter on Windows Terminal) | | Images | CTRL+V to paste (ALT+V on Windows), or drag onto terminal | | Bash commands | !command runs and sends output to LLM, !!command runs without sending |

Standard editing keybindings for delete word, undo, etc. See docs/keybindings.md.

Commands

Type / in the editor to trigger commands. Extensions can register custom commands, skills are available as /skill:name, and prompt templates expand via /templatename.

| Command | Description | |---------|-------------| | /login, /logout | OAuth authentication | | /model | Switch models | | /scoped-models | Enable/disable models for CTRL+P cycling | | /settings | Thinking level, theme, message delivery, transport | | /resume | Pick from previous sessions | | /new | Start a new session | | /name <name> | Set session display name | | /session | Show session info (file, ID, messages, tokens, cost) | | /tree | Jump to any point in the session and continue from there | | /fork | Create a new session from a previous user message | | /clone | Duplicate the current active branch into a new session | | /compact | Delete safe older transcript objects verbatim | | /copy | Copy last assistant message to clipboard | | /export [file] | Export session to HTML file | | /share | Upload as private GitHub gist with shareable HTML link | | /reload | Reload keybindings, extensions, skills, prompts, and context files (themes hot-reload automatically) | | /hotkeys | Show all keyboard shortcuts | | /changelog | Display version history | | /exit | Exit Atomic | | /quit | Quit Atomic |

Keyboard Shortcuts

See /hotkeys for the full list. Customize via ~/.atomic/agent/keybindings.json (legacy ~/.pi/agent/keybindings.json also works). See docs/keybindings.md.

Commonly used:

| Key | Action | |-----|--------| | CTRL+C | Clear editor | | CTRL+C twice | Quit | | Escape | Cancel/abort | | Escape twice | Open /tree | | CTRL+L | Open model selector | | CTRL+P / SHIFT+CTRL+P | Cycle scoped models forward/backward | | SHIFT+Tab | Cycle thinking level | | CTRL+O | Collapse/expand tool output | | CTRL+T | Collapse/expand thinking blocks |

Message Queue

Submit messages while the agent is working:

• Enter queues a steering message, delivered after the current assistant turn finishes executing its tool calls
• ALT+Enter queues a follow-up message, delivered only after the agent finishes all work
• Escape aborts and restores queued messages to editor
• ALT+Up retrieves queued messages back to editor

On Windows Terminal, ALT+Enter is fullscreen by default. Remap it in docs/terminal-setup.md so Atomic can receive the follow-up shortcut.

Configure delivery in settings: steeringMode and followUpMode can be "one-at-a-time" (default, waits for response) or "all" (delivers all queued at once). transport selects provider transport preference ("sse", "websocket", or "auto") for providers that support multiple transports.

Sessions

Sessions are stored as JSONL files with a tree structure. Each entry has an id and parentId, enabling in-place branching without creating new files. See docs/session-format.md for file format.

Management

Sessions auto-save to ~/.atomic/agent/sessions/ organized by working directory (legacy ~/.pi/agent/sessions/ sessions remain readable for compatibility).

atomic -c                  # Continue most recent session
atomic -r                  # Browse and select from past sessions
atomic --no-session        # Ephemeral mode (don't save)
atomic --session <path|id> # Use specific session file or partial ID
atomic --session-id <id>   # Use/create an exact project-local session ID
atomic --name "Refactor"   # Set the session display name
atomic --fork <path|id>    # Fork specific session file or ID into a new session

Use /session in interactive mode to see the current session ID before reusing it with --session <id>, --session-id <id>, or --fork <id>.

Branching

/tree - Navigate the session tree in-place. Select any previous point, continue from there, and switch between branches. All history preserved in a single file.

• Search by typing, fold/unfold and jump between branches with CTRL+←/CTRL+→ or ALT+←/ALT+→, page with ←/→
• Filter modes (CTRL+O): default → no-tools → user-only → labeled-only → all
• Press SHIFT+L to label entries as bookmarks and SHIFT+T to toggle label timestamps

/fork - Create a new session file from a previous user message on the active branch. Opens a selector, copies the active path up to that point, and places the selected prompt in the editor for modification.

/clone - Duplicate the current active branch into a new session file at the current position. The new session keeps the full active-path history and opens with an empty editor.

--fork <path|id> - Fork an existing session file or partial session UUID directly from the CLI. This copies the full source session into a new session file in the current project.

Compaction

Long sessions can exhaust context windows. Compaction now uses deletion-only context compaction by default: the selected model proposes safe deletion targets, Atomic validates them locally, and retained transcript content stays verbatim.

Manual: /compact has no prompt arguments.

Automatic: Enabled by default. Triggers on context overflow (recovers and retries) or when approaching the limit (proactive). Configure via /settings or settings.json. Automatic compaction uses the same verbatim deletion path.

The full history still remains in the JSONL file; use /tree to revisit. See docs/compaction.md for internals.

Settings

Use /settings to modify common options, or edit JSON files directly:

| Location | Scope | |----------|-------| | ~/.atomic/agent/settings.json | Global (all projects; legacy ~/.pi/agent/settings.json also works) | | .atomic/settings.json | Project (overrides global; legacy .pi/settings.json also works after trust) |

See docs/settings.md for all options.

Telemetry and update checks

Atomic has two separate startup features:

• Update check: checks whether a newer Atomic version exists. Disable it with ATOMIC_SKIP_VERSION_CHECK=1 (PI_SKIP_VERSION_CHECK=1 remains a legacy alias). Disabling update checks only turns off this check.
• Install/update telemetry: after first install or a changelog-detected update, sends an anonymous version ping. Opt out by setting enableInstallTelemetry to false in settings.json, or by setting ATOMIC_TELEMETRY=0 (PI_TELEMETRY=0 remains a legacy alias). This does not disable update checks; Atomic may still check for the latest version unless update checks are disabled or offline mode is enabled.

Use --offline or ATOMIC_OFFLINE=1 (PI_OFFLINE=1 remains a legacy alias) to disable all startup network operations described here, including update checks, package update checks, and install/update telemetry.

Context Files

Atomic loads AGENTS.md (or CLAUDE.md) at startup from:

• ~/.atomic/agent/AGENTS.md (global; legacy ~/.pi/agent/AGENTS.md also works)
• Parent directories (walking up from cwd)
• Current directory

Use for project instructions, conventions, common commands. All matching files are concatenated.

Disable context file loading with --no-context-files (or -nc).

System Prompt

Replace the default system prompt with .atomic/SYSTEM.md (project; legacy .pi/SYSTEM.md also works) or ~/.atomic/agent/SYSTEM.md (global; legacy ~/.pi/agent/SYSTEM.md also works). Append without replacing via APPEND_SYSTEM.md.

Customization

Prompt Templates

Reusable prompts as Markdown files. Type /name to expand.

<!-- ~/.atomic/agent/prompts/review.md -->
Review this code for bugs, security issues, and performance problems.
Focus on: {{focus}}

Place in ~/.atomic/agent/prompts/, .atomic/prompts/ (legacy ~/.pi/agent/prompts/ and .pi/prompts/ also work), or an Atomic package to share with others. See docs/prompt-templates.md.

Skills

On-demand capability packages following the Agent Skills standard. Invoke via /skill:name or let the agent load them automatically.

<!-- ~/.atomic/agent/skills/my-skill/SKILL.md -->
# My Skill
Use this skill when the user asks about X.

## Steps
1. Do this
2. Then that

Place in ~/.atomic/agent/skills/, ~/.agents/skills/, .atomic/skills/ (legacy ~/.pi/agent/skills/ and .pi/skills/ also work), or .agents/skills/ (from cwd up through parent directories) or an Atomic package to share with others. See docs/skills.md.

Extensions

TypeScript modules that extend Atomic with custom tools, commands, keyboard shortcuts, event handlers, and UI components.

export default function (pi: ExtensionAPI) {
  pi.registerTool({ name: "deploy", ... });
  pi.registerCommand("stats", { ... });
  pi.on("tool_call", async (event, ctx) => { ... });
}

The default export can also be async. Atomic waits for async extension factories before startup continues, which is useful for one-time initialization such as fetching remote model lists before calling pi.registerProvider().

What's possible:

• Custom tools (or replace built-in tools entirely)
• Sub-agents and plan mode
• Custom compaction and summarization
• Permission gates and path protection
• Custom editors and UI components
• Status lines, headers, footers
• Git checkpointing and auto-commit
• SSH and sandbox execution
• MCP server integration
• Make Atomic look like Claude Code
• Games while waiting (yes, Doom runs)
• ...anything you can dream up

Place in ~/.atomic/agent/extensions/, .atomic/extensions/ (legacy ~/.pi/agent/extensions/ and .pi/extensions/ also work), or an Atomic package to share with others. See docs/extensions.md and examples/extensions/.

Themes

Built-in: dark, light, catppuccin-frappe, catppuccin-latte, catppuccin-macchiato, and catppuccin-mocha. Custom themes hot-reload: modify the active theme file and Atomic immediately applies changes.

Place in ~/.atomic/agent/themes/, .atomic/themes/ (legacy ~/.pi/agent/themes/ and .pi/themes/ also work), or an Atomic package to share with others. See docs/themes.md.

Atomic Packages

Bundle and share extensions, skills, prompts, and themes via npm or git. Find packages on npmjs.com or Discord.

Security: Atomic packages run with full system access. Extensions execute arbitrary code, and skills can instruct the model to perform any action including running executables. Review source code before installing third-party packages.

atomic install npm:@foo/atomic-tools
atomic install npm:@foo/[email protected]      # pinned version
atomic install git:github.com/user/repo
atomic install git:github.com/user/repo@v1  # tag or commit
atomic install git:[email protected]:user/repo
atomic install git:[email protected]:user/repo@v1  # tag or commit
atomic install https://github.com/user/repo
atomic install https://github.com/user/repo@v1      # tag or commit
atomic install ssh://[email protected]/user/repo
atomic install ssh://[email protected]/user/repo@v1    # tag or commit
atomic remove npm:@foo/atomic-tools
atomic uninstall npm:@foo/atomic-tools          # alias for remove
atomic list
atomic update                               # update Atomic only
atomic update --all                         # update Atomic and packages
atomic update --extensions                  # update packages only
atomic update --self                        # update Atomic only
atomic update --self --force                # reinstall Atomic even if current
atomic update npm:@foo/atomic-tools         # update one package
atomic config                               # enable/disable extensions, skills, prompts, themes

Packages install to ~/.atomic/agent/git/ (git) or global npm. Use -l for project-local installs (.atomic/git/, .atomic/npm/; legacy .pi/git/ and .pi/npm/ are compatibility fallbacks). Git @ref values are pinned tags or commits; pinned packages are skipped by atomic update --extensions and atomic update --all, so use atomic install git:host/user/repo@new-ref to move an existing package to a new ref. Git packages install dependencies with npm install --omit=dev by default, so runtime deps must be listed under dependencies; when npmCommand is configured, git packages use plain install for compatibility with wrappers. If you use a Node version manager and want package installs to reuse a stable npm context, set npmCommand in settings.json, for example ["mise", "exec", "node@20", "--", "npm"].

Create a package by adding an app-name manifest key to package.json (atomic for this package). The legacy pi key is still accepted as a backwards-compatible shim:

{
  "name": "my-atomic-package",
  "keywords": ["atomic-package"],
  "atomic": {
    "extensions": ["./extensions"],
    "skills": ["./skills"],
    "prompts": ["./prompts"],
    "themes": ["./themes"],
    "workflows": ["./workflows"]
  }
}

Without a manifest, Atomic auto-discovers from conventional directories (extensions/, skills/, prompts/, themes/, workflows/). Workflow packages may also use a singular workflow/ directory.

See docs/packages.md.

Programmatic Usage

SDK

import { AuthStorage, createAgentSession, ModelRegistry, SessionManager } from "@bastani/atomic";

const authStorage = AuthStorage.create();
const modelRegistry = ModelRegistry.create(authStorage);
const { session } = await createAgentSession({
  sessionManager: SessionManager.inMemory(),
  authStorage,
  modelRegistry,
});

await session.prompt("What files are in the current directory?");

For advanced multi-session runtime replacement, use createAgentSessionRuntime() and AgentSessionRuntime.

See docs/sdk.md and examples/sdk/.

RPC Mode

For non-Node.js integrations, use RPC mode over stdin/stdout:

atomic --mode rpc

RPC mode uses strict LF-delimited JSONL framing. Clients must split records on \n only. Do not use generic line readers like Node readline, which also split on Unicode separators inside JSON payloads.

See docs/rpc.md for the protocol.

Philosophy

Atomic is aggressively extensible so it does not have to dictate your workflow. The distribution bundles first-party extensions for workflows, subagents, MCP, web access, and intercom, while still letting you build or install alternative extensions, skills, and Atomic packages. This keeps Atomic adaptable without forcing every workflow into the core CLI.

Bundled subagents and workflows. Atomic includes the first-party subagents and workflows packages. Use them as shipped, customize them, or replace them with your own extensions if your workflow needs a different orchestration model.

Bundled MCP, web access, and intercom. Atomic ships first-party integrations for MCP tools, web/repository/document/video extraction, and cross-session coordination. These are packaged extensions rather than hard-coded agent behavior, so they remain configurable and replaceable.

Security stays explicit. Run in a container, use project trust controls, or build confirmation flows with extensions inline with your environment and security requirements.

Composable planning and task tracking. Use the bundled workflow/subagent/todo capabilities, write plans to files, or install a package that matches your team's process.

No hidden background bash. Use tmux or explicit extensions for background work. Full observability, direct interaction.

Upstream Pi's minimal-core rationale is documented in the original blog post; Atomic preserves the extensibility model while also bundling first-party capabilities for common workflows.

CLI Reference

atomic [options] [@files...] [messages...]

Package Commands

atomic install <source> [-l]         # Install package, -l for project-local
atomic remove <source> [-l]          # Remove package
atomic uninstall <source> [-l]       # Alias for remove
atomic update [source|self|atomic]   # Update Atomic only, or one package source
atomic update --all                  # Update Atomic and packages
atomic update --extensions           # Update packages only
atomic update --self                 # Update Atomic only
atomic update --self --force         # Reinstall Atomic even if current
atomic update --extension <src>      # Update one package
atomic list                          # List installed packages
atomic config                        # Enable/disable package resources

Modes

| Flag | Description | |------|-------------| | (default) | Interactive mode | | -p, --print | Print response and exit | | --mode json | Output all events as JSON lines (see docs/json.md) | | --mode rpc | RPC mode for process integration (see docs/rpc.md) | | --export <in> [out] | Export session to HTML |

In print mode, Atomic also reads piped stdin and merges it into the initial prompt:

cat README.md | atomic -p "Summarize this text"

Model Options

| Option | Description | |--------|-------------| | --provider <name> | Provider (anthropic, openai, google, etc.) | | --model <pattern> | Model pattern or ID (supports provider/id and optional :<thinking>) | | --api-key <key> | API key (overrides env vars) | | --thinking <level> | off, minimal, low, medium, high, xhigh | | --models <patterns> | Comma-separated patterns for CTRL+P cycling | | --list-models [search] | List available models |

Session Options

| Option | Description | |--------|-------------| | -c, --continue | Continue most recent session | | -r, --resume | Browse and select session | | --session <path\|id> | Use specific session file or partial UUID | | --session-id <id> | Use an exact project session ID, creating it if missing | | --fork <path\|id> | Fork specific session file or partial UUID into a new session | | --session-dir <dir> | Custom session storage directory | | --name <name>, -n <name> | Set the session display name | | --no-session | Ephemeral mode (don't save) |

Tool Options

| Option | Description | |--------|-------------| | --tools <list>, -t <list> | Allowlist specific tool names across built-in, extension, and custom tools | | --exclude-tools <list>, -xt <list> | Denylist specific built-in, extension, and custom tools | | --no-builtin-tools, -nbt | Disable built-in tools by default but keep extension/custom tools enabled | | --no-tools, -nt | Disable all tools by default |

Default built-in tools: read, bash, edit, write, ask_user_question, todo. Additional built-in read-only tools are available through tool options: grep, find, ls. Use --exclude-tools to disable one or more tools while leaving the rest available.

Project Trust Options

| Option | Description | |--------|-------------| | --approve, -a | Trust project-local files/resources for this run | | --no-approve, -na | Ignore project-local files/resources for this run |

Project trust gates .atomic/legacy .pi project resources, project package settings, project-local context files, and .agents/skills discovered from the project tree. Saved trust decisions can be managed with /trust; see docs/security.md.

Resource Options

| Option | Description | |--------|-------------| | -e, --extension <source> | Load extension from path, npm, or git (repeatable) | | --no-extensions | Disable extension discovery | | --skill <path> | Load skill (repeatable) | | --no-skills | Disable skill discovery | | --prompt-template <path> | Load prompt template (repeatable) | | --no-prompt-templates | Disable prompt template discovery | | --theme <path> | Load theme (repeatable) | | --no-themes | Disable theme discovery | | --no-context-files, -nc | Disable AGENTS.md and CLAUDE.md context file discovery |

Combine --no-* with explicit flags to load exactly what you need, ignoring settings.json (e.g., --no-extensions -e ./my-ext.ts).

Other Options

| Option | Description | |--------|-------------| | --system-prompt <text> | Replace default prompt (context files and skills still appended) | | --append-system-prompt <text> | Append to system prompt | | --verbose | Force verbose startup | | -h, --help | Show help | | -v, --version | Show version |

File Arguments

Prefix files with @ to include in the message:

atomic @prompt.md "Answer this"
atomic -p @screenshot.png "What's in this image?"
atomic @code.ts @test.ts "Review these files"

Examples

# Interactive with initial prompt
atomic "List all .ts files in src/"

# Non-interactive
atomic -p "Summarize this codebase"

# Non-interactive with piped stdin
cat README.md | atomic -p "Summarize this text"

# Different model
atomic --provider openai --model gpt-4o "Help me refactor"

# Model with provider prefix (no --provider needed)
atomic --model openai/gpt-4o "Help me refactor"

# Model with thinking level shorthand
atomic --model sonnet:high "Solve this complex problem"

# Limit model cycling
atomic --models "claude-*,gpt-4o"

# Read-only mode
atomic --tools read,grep,find,ls -p "Review the code"

# High thinking level
atomic --thinking high "Solve this complex problem"

Environment Variables

| Variable | Description | |----------|-------------| | ATOMIC_CODING_AGENT_DIR | Override config directory (default: ~/.atomic/agent; PI_CODING_AGENT_DIR is a legacy alias) | | ATOMIC_CODING_AGENT_SESSION_DIR | Override session storage directory (overridden by --session-dir; PI_CODING_AGENT_SESSION_DIR is a legacy alias) | | ATOMIC_PACKAGE_DIR | Override package directory (useful for Nix/Guix where store paths tokenize poorly; PI_PACKAGE_DIR is a legacy alias) | | ATOMIC_OFFLINE | Disable startup network operations, including update checks, package update checks, and install/update telemetry (PI_OFFLINE is a legacy alias) | | ATOMIC_SKIP_VERSION_CHECK | Skip the Atomic version update check at startup. PI_SKIP_VERSION_CHECK is a legacy alias. | | ATOMIC_TELEMETRY | Override install/update telemetry. Use 1/true/yes to enable or 0/false/no to disable. This does not disable update checks (PI_TELEMETRY is a legacy alias). | | PI_CACHE_RETENTION | Provider/upstream-specific prompt-cache retention knob; set to long where supported. This is not an ATOMIC_* alias and has no Atomic-prefixed equivalent. | | VISUAL, EDITOR | External editor for CTRL+G |

Contributing & Development

See CONTRIBUTING.md for guidelines and docs/development.md for setup, forking, and debugging.

License

MIT

See Also

• @earendil-works/pi-ai: Core LLM toolkit
• @earendil-works/pi-agent-core: Agent framework
• @earendil-works/pi-tui: Terminal UI components