Ein

An AI agent for your terminal — self-hosted, plugin-driven, and yours.

┌─────────────────────────────┐          ┌──────────────────────────────┐
│          ein                │  gRPC    │          eind                │
│                             │ (proto)  │                              │
│  Ratatui terminal UI        │◄────────►│  Agent loop + tool executor  │
│  Session picker on startup  │          │  WASM plugin host            │
│  Slash command autocomplete │          │  Pluggable model clients     │
│  Animated thinking spinner  │          │  Per-session sandboxing      │
│  Syntax-highlighted diffs   │          │  SQLite session persistence  │
└─────────────────────────────┘          └──────────────────────────────┘

ein is the terminal UI you interact with; eind is the agent server that runs as a background service. On first launch, ein downloads eind automatically and registers it as a system service — no separate server setup required. Tools and model clients are sandboxed WASM plugins: choose from OpenRouter, Anthropic, OpenAI, or Ollama, or write your own.

Features

• Works with OpenRouter, Anthropic, OpenAI, and Ollama — bring your own key or run locally with no API key
• Sessions persist to SQLite; resume any conversation where you left off
• Tools run as sandboxed WASM components with fine-grained filesystem and network controls per session
• Extend with custom tools or model client backends
• Syntax-highlighted edit diffs shown inline as the agent works
• Live config reload — update credentials without restarting

Installation

Install with cargo binstall:

cargo install cargo-binstall
cargo binstall --git https://github.com/mstallmo/ein ein

Or download pre-built archives directly from GitHub Releases.

Getting Started

Run ein. On first launch:

1. Server setup — eind is downloaded from GitHub Releases and registered as a background service automatically
2. Setup wizard — choose your model provider and enter your API credentials
3. Session picker — create a new session or resume an existing one; when starting a new session, a prompt asks whether to grant the agent access to your current working directory for that session

That's it. ein manages eind — you never need to run the server separately.

Configuration

The TUI stores configuration at ~/.ein/config.json, created on first run. You can also open it at any time with /config.

{
  "allowed_paths": [],
  "allowed_hosts": [],
  "plugin_configs": {
    "ein_openrouter": {
      "config": {
        "api_key": "sk-or-...",
        "base_url": "https://openrouter.ai/api/v1",
        "model": "anthropic/claude-haiku-4.5",
        "max_tokens": "2500"
      }
    }
  }
}

Global fields

Field	Description
allowed_paths	Filesystem paths all WASM plugins may read/write (preopened for every session)
allowed_hosts	Hostnames all WASM plugins may connect to (empty = deny all; "*" = allow all)

Credentials by provider

OpenRouter

{
  "plugin_configs": {
    "ein_openrouter": {
      "config": {
        "api_key": "sk-or-...",
        "base_url": "https://openrouter.ai/api/v1"
      }
    }
  }
}

Anthropic

{
  "plugin_configs": {
    "ein_anthropic": {
      "config": {
        "api_key": "sk-ant-..."
      }
    }
  }
}

OpenAI

{
  "plugin_configs": {
    "ein_openai": {
      "config": {
        "api_key": "sk-..."
      }
    }
  }
}

Ollama (no API key required)

{
  "plugin_configs": {
    "ein_ollama": {
      "config": {
        "base_url": "http://localhost:11434",
        "model": "llama3"
      }
    }
  }
}

Changes to config.json are picked up automatically while the TUI is running.

Usage

Type a message and press Enter to send. Type / to see available slash commands with autocomplete hints.

Key / Command	Action
Enter	Send message / run slash command
↑ / ↓	Scroll conversation history
Ctrl-C	Force quit
/exit	Exit the TUI
/config	Open ~/.ein/config.json in $EDITOR
/clear	Wipe the agent's in-memory context (SQLite history preserved)
/new	Drop current session and start a fresh one
/sessions	Re-open the session picker to switch sessions
/compact	Summarise the conversation via the LLM and replace history with the summary
/plugins	Manage installed plugins
/setup	Re-run the first-time setup wizard
/uninstall	Stop and remove the eind service and binary

While the agent is working, an animated thinking spinner appears in the conversation pane. Tool invocations are shown inline as the agent uses them:

 ▸ Bash  ls -la
 ▸ Read  src/main.rs
 ▸ Write  src/main.rs
 ▸ Edit  src/main.rs

Edit calls display a syntax-highlighted diff showing removed and added lines (up to 5 each), with line numbers.

The status bar shows the active model and cumulative token usage. Use Shift+D on a session in the picker to permanently delete it.

Connection behaviour

The TUI reconnects automatically every 3 seconds if the server is unavailable. Running /new or /sessions bypasses the retry delay and triggers an immediate reconnect attempt.

Tools

Tools are WASM components loaded at startup. Four are included:

Tool	Description
Bash	Execute shell commands (streams stdout in real time)
Read	Read a file from the filesystem
Write	Write content to a file
Edit	Replace a specific string in a file with new content

Adding a tool

1. Create a new package under plugins/ implementing the ToolPlugin trait from plugins/ein_tool/
2. Add it to scripts/build_install_plugins.sh
3. Rebuild — the server picks it up automatically on next start

Architecture

crates/
  ein_agent/        Agent component (agent loop, tool call logic, extension interface)
  ein_core/         Shared types and utilities between plugins and the harness
  ein_http/         WASM-native HTTP client (used by model client plugins)
  ein_plugin/       WASM plugin interface
  ein_proto/        Protocol Buffer definitions (gRPC service + message types)
ein/                Terminal UI client
eind/               gRPC server — WASM plugin host, session persistence
plugins/
  ein_anthropic/    Anthropic model client plugin
  ein_bash/         Bash tool plugin
  ein_edit/         Edit tool plugin
  ein_ollama/       Ollama model client plugin
  ein_openai/       OpenAI model client plugin
  ein_openrouter/   OpenRouter model client plugin
  ein_read/         Read tool plugin
  ein_write/        Write tool plugin

Protocol

The protocol (crates/ein_proto/proto/ein.proto) defines a bidirectional streaming AgentSession RPC, a ListSessions RPC, and a DeleteSession RPC. Each session opens with a SessionConfig init message followed by user prompts; the server streams back AgentEvent messages starting with a SessionStarted event that carries the session UUID and a resumed boolean.

Session persistence

Sessions are persisted to ~/.ein/sessions.db. Supplying a previously assigned session_id in SessionConfig restores the full conversation history so the agent picks up exactly where it left off.

Contributing

Contributions are welcome. See CONTRIBUTING.md for how to build from source, run in development, and cut a release.

License

Ein is licensed under the Apache License, Version 2.0.

Copyright 2026 Mason Stallmo.

By submitting a pull request, you agree that your contribution is licensed under the Apache License, Version 2.0.