Arbiter

A local agent runtime in a single native binary. Run multi-agent workflows on your machine — interactive TUI, one-shot CLI, or HTTP+SSE — with hard tool allowlists and a shared streaming event bus. Local-first; network is optional.

Not a library. Not a hosted platform. A process you run.

Quick start

# Install (macOS arm64)
curl -L https://github.com/tylerreckart/arbiter/releases/latest/download/arbiter-macos-arm64.tar.gz \
  | tar xz -C /usr/local/bin

export OPENROUTER_API_KEY="sk-or-..."   # or use Ollama — see docs
arbiter --init                          # seed starter agents under ~/.arbiter/
arbiter                                 # open the TUI

Linux binaries, source builds, Ollama, --send, and --api are in getting-started/local.

Same agents, three faces

Mode	Command	For
Interactive	arbiter	Multi-pane TUI, global conversation store
One-shot	arbiter --send <agent> "..."	Scripts, cron, CI
Server	arbiter --api	HTTP+SSE API, tenant-isolated, A2A v1.0

One binary. Shared storage under ~/.arbiter/. Provider keys (OpenRouter, Ollama, …) are the only external dependency for model calls.

Why run it

Own the harness. Orchestrate specialists, durable memory, and tool use without duct-taping a chat CLI to FastAPI and SQLite. The runtime stays thin; agent behavior lives in constitutions (JSON: model, role, rules, tool allowlist).

Hard limits, not prompt suggestions. Every agent's tool surface is an allowlist checked at dispatch. Optional advisor gate: a second model signs off before consequential turns reach you.

One event model everywhere. The orchestration loop streams the same SSE-shaped events the TUI already consumes — text, tool calls, files, sub-agent responses, done. API clients get that stream over the wire; durable request logs make reconnect and replay possible.

Route work in, don't write a dispatcher. Webhooks, queues, firmware, and sensors can POST /v1/events; declare a glob per agent and Arbiter routes matching events there.

Design in one line

Process-local multi-agent orchestration with a prose-embedded command DSL, shared storage, and a streaming event bus exposed as TUI / CLI / HTTP.

Deeper tradeoffs — why commands are inline rather than JSON tool-calling, why ops (TLS, WAF, rate limits) stay at the reverse proxy, how memory and tenants work — are in docs/philosophy.

Themeable

38 presets ship in the box (Nord, Dracula, Catppuccin, Gruvbox, Tokyo Night, Solarized, and more); export one as a starting point and edit hex values to make your own:

arbiter --export-theme high-contrast > ~/.arbiter/themes/mine.json

/theme list           # built-in presets + your custom themes
/theme mine           # switch instantly, no restart
/theme save mine      # write the current look back to disk

Backgrounds, text, borders, markdown and diff syntax colors, even the 12-color agent palette are all keyed in one schema — down to the padding and column breakpoints. Full reference in docs/tui/themes.md.

Documentation

• docs/getting-started — first agent reply
• docs/philosophy — why Arbiter is shaped this way
• docs/api/ — HTTP API, tenants, SSE, MCP, A2A, memory
• docs/cli/ — --init, --send, --api, env vars
• docs/tui/ — panes, keybindings, themes, sessions
• ROADMAP.md — phased plan toward 1.0 readiness
• CHANGELOG.md · CONTRIBUTING.md · SECURITY.md

Arbiter is experimental. The event surface, agent constitutions, and HTTP shape may change. /exec is unsandboxed by default; treat it accordingly.

Licensed under the Apache License 2.0.