wild-pc/docs/component-registry.md

Registry

How castle tracks, configures, and manages programs, services, and jobs. This is the central reference for castle.yaml structure and the registry architecture.

castle.yaml

The single source of truth. Lives at ~/.castle/castle.yaml. Three top-level sections:

gateway:
  port: 9000

programs:
  my-tool:
    description: Does something useful
    source: code/my-tool
    stack: python-cli
    behavior: tool
    system_dependencies: [pandoc]

services:
  my-service:
    component: my-service
    run:
      runner: python
      program: my-service
    expose:
      http:
        internal: { port: 9001 }
        health_path: /health
    proxy:
      caddy: { path_prefix: /my-service }
    manage:
      systemd: {}

jobs:
  my-job:
    component: my-tool
    run:
      runner: command
      argv: [my-tool, sync]
    schedule: "0 2 * * *"
    manage:
      systemd: {}

Section semantics

Section	Purpose	Category
programs:	Software catalog — what exists	tool, frontend, daemon
services:	Long-running daemons — how they run	service
jobs:	Scheduled tasks — when they run	job

Services and jobs can reference a program via component: for description fallthrough and source code linking. They can also exist independently (e.g., castle-gateway runs Caddy — not our software).

Program blocks

Programs define what software exists — identity, source, behavior, builds.

behavior — What role this program plays

behavior: daemon    # or: tool, frontend

Explicit declaration of how the program is used:

• daemon — long-running service (python-fastapi stack)
• tool — CLI utility (python-cli stack)
• frontend — web UI (react-vite stack)

source — Where the source lives

source: code/my-tool        # your programs, under ~/.castle/code/
source: repo:castle-api      # castle's own programs, inside the git repo

The source path is resolved one of three ways (core/src/castle_core/config.py):

source: value	Resolves to	Used for
code/my-tool (relative)	$CASTLE_HOME/code/my-tool	Your own programs
repo:castle-api	<repo>/castle-api (via the top-level repo: field)	Castle's built-in programs
/abs/path	as-is	Anything explicitly absolute

Relative sources resolve against the castle home ($CASTLE_HOME, default ~/.castle — see Infrastructure paths). Most programs you create live under $CASTLE_HOME/code/ and are recorded as source: code/<name>. Castle's own programs (CLI, core, castle-api, app) live in the git repo and use the repo: prefix. When castle deploy writes castle.yaml back out, it rewrites absolute paths into these relative forms.

stack — Development toolchain

stack: python-fastapi   # or: python-cli, react-vite

Stacks define how programs get built, checked, and installed.

system_dependencies — Required system packages

system_dependencies: [pandoc, poppler-utils]

System packages that must be installed for the program to work. Displayed in castle tool list and the dashboard.

version — Program version

version: "1.0.0"

Optional version metadata.

build — How to build it

build:
  commands:
    - ["pnpm", "build"]
  outputs:
    - dist/

Programs with build outputs are typically frontends.

Service blocks

Services define how long-running daemons are deployed.

run — How to start it (required)

Discriminated union on runner:

Runner	Sync	Deploy	Key fields
python	uv sync	which(program) → installed binary	program, args
command	(none)	which(argv[0]) → resolved path	argv
container	(none)	docker/podman run	image, command, ports, volumes
node	package_manager install	package_manager run script	script, package_manager
remote	(none)	(none — no local process)	base_url, health_url

run:
  runner: python
  program: my-service     # name in [project.scripts]

expose — What it exposes

expose:
  http:
    internal:
      port: 9001            # Required for HTTP services
    health_path: /health     # Used by health polling

proxy — How to proxy it

proxy:
  caddy:
    path_prefix: /my-service   # Proxied at gateway:9000/my-service/

Castle generates a Caddyfile from these entries. Only needed for services accessible through the gateway.

manage — How to manage it

manage:
  systemd: {}

Enables castle service enable/disable and castle logs. An empty {} uses defaults (enable=true, restart=on-failure, restart_sec=2).

Full options:

manage:
  systemd:
    description: Custom unit description
    restart: always          # on-failure | always | no
    restart_sec: 2
    no_new_privileges: true
    after: [network.target, castle-other.service]
    wanted_by: [default.target]
    exec_reload: "caddy reload ..."

defaults — Default environment

defaults:
  env:
    CENTRAL_CONTEXT_URL: http://localhost:9001
    API_KEY: ${secret:MY_API_KEY}

Castle resolves ${secret:NAME} by reading ~/.castle/secrets/NAME. Never store secrets in castle.yaml or project directories.

Job blocks

Jobs define how scheduled tasks run. Same blocks as services plus schedule and timezone.

schedule — Cron expression (required)

schedule: "*/5 * * * *"
timezone: America/Los_Angeles    # default

Castle generates a systemd .timer file alongside the .service unit.

Other blocks

Jobs also support run (required), manage, and defaults — same semantics as services.

How programs get into ~/.castle/code/

Every program's source lives in one place — ~/.castle/code/<name>/. It can arrive there a few ways:

1. Scaffold a new one with castle create — writes the project into ~/.castle/code/<name>/ and registers it in castle.yaml with source: code/<name>.
2. Clone an existing project — git clone <url> ~/.castle/code/<name>, then add a programs: entry pointing at source: code/<name>.
3. Drop files in directly — a code/<name>/ directory is just a working tree; it doesn't have to be under version control to be registered and run.

~/.castle/ and ~/.castle/code/ are not themselves git repos, and there are no submodules. Each program directory manages its own version control (or none) independently — some are standalone git clones, others are just loose files.

Castle's own programs (CLI, core, castle-api, app) are the exception: they live inside the castle git repo and are referenced with source: repo:<name>.

Registering a new program

Via castle create (recommended)

# Service — scaffolds into ~/.castle/code/, assigns port, registers in castle.yaml
castle create my-service --stack python-fastapi --description "Does something"

# Tool — scaffolds into ~/.castle/code/
castle create my-tool --stack python-cli --description "Does something"

Manually

Clone or create the project under ~/.castle/code/, then add entries to the appropriate sections of castle.yaml:

# Tool — only needs a program entry
programs:
  my-tool:
    description: Does something useful
    source: code/my-tool
    stack: python-cli
    behavior: tool

# Service — needs both program and service entries
programs:
  my-service:
    description: Does something useful
    source: code/my-service
    stack: python-fastapi
    behavior: daemon

services:
  my-service:
    component: my-service
    run:
      runner: python
      program: my-service
    expose:
      http:
        internal: { port: 9001 }
        health_path: /health
    proxy:
      caddy: { path_prefix: /my-service }
    manage:
      systemd: {}

Lifecycle

Service lifecycle

castle create my-service --stack python-fastapi   # 1. Scaffold + register
cd ~/.castle/code/my-service && uv sync   # 2. Install deps
# ... implement ...
castle test my-service                    # 3. Run tests
castle service enable my-service          # 4. Generate systemd unit, start
castle gateway reload                     # 5. Update Caddy routes

After service enable, the service starts automatically on boot and restarts on failure. Manage with:

castle logs my-service -f         # Tail logs
castle run my-service             # Run in foreground (for debugging)
castle service disable my-service # Stop and remove systemd unit

Tool lifecycle

castle create my-tool --stack python-cli        # 1. Scaffold + register
cd ~/.castle/code/my-tool && uv sync     # 2. Install deps
# ... implement ...
castle test my-tool                      # 3. Run tests
uv tool install --editable ~/.castle/code/my-tool/   # 4. Install to PATH

Job lifecycle

Jobs are defined in the jobs: section with a run spec and schedule:

jobs:
  my-job:
    description: Runs nightly
    run:
      runner: command
      argv: ["my-job"]
    schedule: "0 2 * * *"
    manage:
      systemd: {}

castle service enable my-job generates both a .service (Type=oneshot) and a .timer file.

Infrastructure paths

Castle uses two independent roots, each overridable by an environment variable (both expand ~ and resolve relative paths):

• CASTLE_HOME — config, code, artifacts, and secrets. Default ~/.castle.
• CASTLE_DATA_DIR — program/service data I/O (potentially large; lives on a dedicated volume). Default /data/castle. Decoupled from CASTLE_HOME on purpose so bulk data doesn't sit in the home directory.

What	Where
Castle home	$CASTLE_HOME (default ~/.castle)
Registry	$CASTLE_HOME/castle.yaml
Program source (yours)	$CASTLE_HOME/code/<name>/
Program source (castle's)	<repo>/<name> (via source: repo:<name>)
Secrets	$CASTLE_HOME/secrets/<NAME>
Generated Caddyfile	$CASTLE_HOME/artifacts/specs/Caddyfile
Built frontends	$CASTLE_HOME/artifacts/content/<name>/
Service data	$CASTLE_DATA_DIR/<name>/ (default /data/castle/<name>/)
Systemd units	~/.config/systemd/user/castle-*.service
Systemd timers	~/.config/systemd/user/castle-*.timer

Defined in core/src/castle_core/config.py: CASTLE_HOME (with derived CODE_DIR, SECRETS_DIR, SPECS_DIR, CONTENT_DIR) and the independent DATA_DIR (CASTLE_DATA_DIR). castle deploy passes each service its data path via the generated <PREFIX>_DATA_DIR env var. Systemd unit/timer paths are fixed by systemd's user-unit convention.

Manifest models

The Pydantic models live in core/src/castle_core/manifest.py. Key classes:

• ProgramSpec — software catalog entry (source, behavior, stack, build, system_dependencies)
• ServiceSpec — long-running daemon (run, expose, proxy, manage, defaults)
• JobSpec — scheduled task (run, schedule, manage, defaults)
• RunSpec — discriminated union (RunPython, RunCommand, RunContainer, RunNode, RunRemote)
• ExposeSpec, ProxySpec, ManageSpec, BuildSpec
• CaddySpec, SystemdSpec, HttpExposeSpec, HttpInternal

Config loading: core/src/castle_core/config.py — load_config() parses castle.yaml into CastleConfig with typed programs, services, and jobs dicts.

Infrastructure generators: core/src/castle_core/generators/ — systemd unit/timer generation (systemd.py) and Caddyfile generation (caddyfile.py).