Castle

Standing to author, run, govern, and maintain your own software.

A personal software platform. Castle manages independent services, tools, and frontends — and launches your coding agents — from a single CLI, with a unified gateway, systemd integration, and a web dashboard.

Historically, applications have usually been developed by third parties, packaged for distribution, installed through app stores or package managers, and updated through channels controlled by someone other than the user. That model still works for large applications, but it is often too heavy for the small, personal, situational software people increasingly want to create.

AI-assisted development changes the shape of this problem. Users can now create useful software directly: small services, scripts, dashboards, agents, automations, and configurations of existing tools. Many of these programs do not need a public release process, an app store listing, or a conventional distribution channel. They need a reliable place to run.

Castle provides that place.

Castle gives simple applications a consistent local environment for development, registration, deployment, discovery, and operation. Programs remain independent, but Castle provides the surrounding structure: process management, routing, metadata, service lifecycle, logs, and a common interface for running and inspecting the software in your domain.

In this sense, Castle is a personal software estate: a practical way to organize the software you create and run yourself, without requiring every tool to become a fully packaged product.

How it works

Castle separates what software exists from how it runs:

• Programs — the catalog. A program is a source repo Castle knows how to work with (dev verbs, build) and where it lives. One file per program under ~/.castle/programs/<name>.yaml.

• Deployments — how a program is realized on this node. One file per deployment under ~/.castle/deployments/<name>.yaml, discriminated by its manager:

  manager	what it is	derived kind
  systemd	a supervised process — or, with a schedule, a timer	service / job
  caddy	a static site served by the gateway from a build dir	static
  path	a CLI installed on your PATH (uv tool install)	tool
  none	an external service on another node (reference only)	reference

  For systemd, a nested run.launcher (python / command / container / compose / node) says how the process starts. The kind is always derived from the manager (+ schedule) — never stored.

A program can have several deployments — a CLI that is both a tool on PATH and a scheduled job — so a program has no single kind of its own; it has deployments, each with its own.

Standing everything up is the two honest steps castle deploy (regenerate systemd units and gateway config from your config) then castle start (enable/start it). There is no bundled "up".

Stacks

Castle stacks are pre-configured development environments that provide starting points for building Castle programs. A stack can define the language, framework, dependencies, tools, conventions, and Castle integration needed for a particular kind of application — python-fastapi, python-cli, react-vite, supabase.

Stacks are designed to work well with coding assistants. They give assistants a consistent target when generating Castle programs, making it easier to produce applications that are correctly structured, configured, and ready to run under Castle. If your coding assistant understands Castle, it can help you create, register, manage, and evolve custom applications more efficiently.

A stack seeds a new program's scaffold and default dev-verb commands, but it's optional at runtime: a program stands on its own via its declared commands: and source:, so you can adopt any existing repo with castle program add — no stack required.

Agents

Castle can launch your coding agents. Declare them in castle.yaml under agents: — each entry is just a command Castle runs in a terminal:

agents:
  claude:
    command: claude
    description: Anthropic Claude Code
  aider:
    command: aider
    args: ["--no-auto-commits"]
    cwd: /data/repos/my-project

The dashboard has a terminal dock that launches any declared agent in a pseudo-terminal (over a WebSocket) and manages live sessions (list, resume, kill). Castle is assistant-agnostic — it only ever runs command args in a pty and never parses the agent's output, so any interactive CLI works. With no agents: block set, a sensible default set (claude, opencode, amplifier, …) is offered.

Quick start

# Install the CLI (editable, onto your PATH)
uv tool install --editable cli/

# Bootstrap infrastructure + the ~/.castle tree and a default castle.yaml
./install.sh

castle list                     # what's registered
castle deploy && castle start   # apply config to the runtime, then bring it up
open http://localhost:9000      # the dashboard

Creating programs

castle program create scaffolds the source and its deployment from a stack:

# A service — FastAPI app + a systemd service deployment (health, unit, route)
castle program create my-api --stack python-fastapi --description "Does something"
castle program test my-api
castle deploy my-api && castle service enable my-api

# A tool — a CLI installed on your PATH
castle program create my-tool --stack python-cli --description "Does something"
castle tool install my-tool

# A static frontend — built once, served by the gateway
castle program create my-app --stack react-vite --description "Web interface"
castle program build my-app && castle deploy

# Adopt an existing repo (no stack needed — dev verbs detected or declared)
castle program add ~/projects/some-rust-tool

CLI

Operations live under the resource they act on. program is the catalog; service, job, and tool are views over the one deployment set; platform lifecycle is top-level.

# Programs — the software catalog
castle program list|info|create|add|clone|delete|run|install|uninstall
castle program build|test|lint|type-check|check [name]        # dev verbs

# Deployment lenses (service = systemd, job = systemd + schedule, tool = path)
castle service  list|info|create|delete|deploy|enable|disable|start|stop|restart|logs
castle job      …same verbs; create takes --schedule
castle tool     list|info|install|uninstall                    # CLIs on your PATH

# Platform-wide
castle list [--kind K] [--stack S] [--json]   # catalog + every deployment view
castle status                                 # unified status
castle deploy [name]                          # apply config → units + Caddyfile
castle start | stop | restart                 # all deployments (+ gateway)
castle gateway start|stop|reload|status

castle tool list --json is the machine-readable tool catalog assistants use to build context — it surfaces each tool's actual executable (which can differ from the program name, e.g. litellm-intent-router installs intent-router), its description, and whether it's installed.

Configuration

The registry lives under ~/.castle/: a global castle.yaml plus one file per resource under programs/ and deployments/.

# ~/.castle/castle.yaml — globals
gateway:
  port: 9000
repo: /data/repos/castle     # resolves `source: repo:<name>` for castle's own programs

# ~/.castle/programs/my-api.yaml — the catalog entry
description: Does something useful
source: /data/repos/my-api
stack: python-fastapi

# ~/.castle/deployments/my-api.yaml — a systemd service (derived kind: service)
program: my-api
manager: systemd
run: { launcher: python, program: my-api }
expose: { http: { internal: { port: 9001 }, health_path: /health } }
proxy: true                        # served at my-api.<gateway.domain>
manage: { systemd: {} }
defaults:
  env:
    MY_API_PORT: ${port}           # = expose.http.internal.port
    MY_API_DATA_DIR: ${data_dir}   # = $CASTLE_DATA_DIR/my-api
    API_KEY: ${secret:MY_API_KEY}

defaults.env is the single, explicit source of a deployment's environment — Castle injects nothing implicitly. The placeholders ${port}, ${data_dir}, ${name}, ${public_url}, and ${secret:NAME} map your program's own env var names to Castle's computed values. Secrets live in ~/.castle/secrets/ (never in a repo).

Gateway, DNS & TLS

Every gateway-exposed deployment gets its own subdomain — <name>.<gateway.domain> — routed to it by the Caddy gateway (there are no path-prefix routes). Exposure is a single checkbox: proxy: true on a service, while a static deployment is inherently served. The dashboard is castle.<domain> and the API castle-api.<domain>; on a node with no domain, :9000 serves the dashboard plus a /api proxy.

gateway.tls is a per-node choice: off (plain HTTP on :9000) or acme (a real Let's Encrypt wildcard *.<domain> via a DNS-01 challenge — publicly trusted, no CA to install, while the services stay internal-only). Reaching a service from the public internet is separately opt-in via a Cloudflare tunnel (public: true). See docs/dns-and-tls.md.

Layout

~/.castle/                 # instance: config, artifacts, secrets
  castle.yaml              #   globals (gateway, repo, agents)
  programs/  deployments/  #   one file per program / deployment
  secrets/                 #   secret files (mode 700)
  artifacts/specs/         #   generated Caddyfile, registry.yaml
/data/repos/<name>/        # your program source (absolute source:)
/data/castle/<name>/       # per-deployment data volume
<repo>/                    # castle itself: cli/ core/ castle-api/ app/ docs/

Independence principle: your programs never depend on Castle. They accept configuration (data dir, port, URLs) via environment variables; only Castle's own programs (CLI, API, gateway) know Castle internals.

Dashboard & API

The dashboard (app/, served at castle.<domain> or http://localhost:9000) lists programs and deployments, edits their config, drives lifecycle, shows the gateway route table and logs, and hosts the agent terminal dock.

castle-api (port 9020, proxied at castle-api.<domain>) is the control plane: /deployments, /programs, /services, /jobs, /gateway, /status, an SSE /stream, config editing under /config/…, and the agent session endpoints under /agents. The full endpoint reference is in CLAUDE.md.

Mesh (opt-in)

Castle nodes can discover each other via MQTT + mDNS to form a personal infrastructure mesh — the gateway can route to services on other nodes and the dashboard shows discovered nodes and cross-node routes. It's all off by default; single-node needs none of it. Enable on castle-api via CASTLE_API_MQTT_ENABLED and CASTLE_API_MDNS_ENABLED.

Docs

• docs/registry.md — the registry model, castle.yaml, deployment fields, lifecycle
• docs/dns-and-tls.md — gateway routing, DNS, the off / acme TLS modes
• docs/stacks/ — per-stack guides (python-fastapi, python-cli, react-vite, supabase)
• AGENTS.md — the canonical, assistant-agnostic operator guide (recipes, gateway, tunnel, mesh)