Introduction

Castellan

Self-evolving agent coordination runtime — the harness is the castellan.

Rust MIT CI verified

Install

curl -fsSL https://raw.githubusercontent.com/Alphabetsoup16/Castellan/main/install.sh | bash

Terminal demo — run → episode → multiplexer

Offline / no CDN — static transcript

$ castellan plugin list
$ castellan run --goal "reach target" --plugin gridworld
episode satisfied
$ castellan run --json | head -3

Download castellan-demo.cast · Run live from repo root: ./docs/demo/castellan-demo.sh

Quickstart · Daily driver · Agent guide · Socket API · MCP tools

Castellan is a Rust coordination runtime: agents wake from a decaying pressure field, verify work through typed harness recursion (RAH), and improve topology from episode logs.

What makes Castellan different

Castellan is not a meta-harness wrapper or workflow DSL. Default castellan run uses deterministic plugins (gridworld, shell) — wire your LLM via MCP, ACP, or remote panes. See What Castellan is / is not.

Conventions

Episode flywheel

flowchart LR
    RUN[castellan run] --> LOG[.castellan/episodes]
    LOG --> EVOLVE[castellan evolve]
    EVOLVE --> GATE[castellan drift-check]
    GATE --> RUN

    classDef runtime stroke:#0969da,stroke-width:2px
    classDef evolve stroke:#d97706,stroke-width:2px
    classDef gate stroke:#1a7f37,stroke-width:2px

    class RUN,LOG runtime
    class EVOLVE evolve
    class GATE gate

1. Run — castellan run or castellan run --rlm
2. Log — episode JSON in .castellan/episodes/
3. Evolve — topology mutations from corpus
4. Gate — castellan drift-check manifest guardrails

castellan run --goal "reach target" --plugin gridworld

Full walkthrough: Quickstart.

Quick paths

Build this book locally

mdbook build book && mdbook serve book

See Deployment. Live site: castellan-docs.pages.dev.