iii-engine-config

Engine Config

iii has two engine configuration modes. Do not mix them.

Managed Compose engine

The presence of engine: means that Compose owns the engine process. Engine worker values are direct mappings; there is no nested config: field.

namespace: orders
engine:
  url: ws://127.0.0.1:49134
  registration_namespace_grace_ms: 5000

Start it with:

engine.url defaults to ws://127.0.0.1:49134 and uses Compose's ${VAR:-default} expansion. engine.workers stays opaque until the engine reads the generated YAML, so its values use ${VAR:default} and retain numeric types. Compose materializes an owner-only config under <project-dir>/.iii/compose/<daemon-namespace>/ and removes it after clean shutdown. With III_COMPOSE_STATE_DIR, it uses <state-root>/<project-slug>/<daemon-namespace>/. Changing engine: requires restarting Compose. Do not combine a managed file with explicit --engine.

Allowed engine worker base names are:

• configuration
• iii-worker-manager
• iii-http-functions
• iii-stream
• iii-sandbox

Use #instance for another instance of an allowed worker. iii-engine-functions, iii-telemetry, and iii-observability are injected automatically and must not be declared.

HTTP, cron, queue, state, pubsub, bridge, application, and custom workers belong under containers:. Add registry packages with:

Directly supervised engine

Keep list-shaped config.yaml only when systemd, Kubernetes, or another supervisor owns the engine:

Start the engine and external Compose daemon separately:

The external Compose file must omit engine:. III_URL may replace --engine. Direct config expansion uses ${VAR:default} and accepts only the same five engine-owned worker types. Any project worker stops startup/reload with UNSUPPORTED_CONFIG_WORKERS.

Security and operations

• Bind private worker-manager listeners to 127.0.0.1.
• Put public listeners behind middleware_function_id and RBAC registration hooks.
• Keep secrets in environment-backed configuration; do not commit literal credentials.
• Preserve configuration, stream, state, and queue storage paths during migrations.
• Use compose::status for process ownership and engine::workers::list for live connections.
• compose::add never edits engine: or restarts the engine.

When to Use

• Use this skill for managed engine: maps, direct config.yaml, engine-owned workers, ports, adapters, RBAC listeners, or engine lifecycle selection.
• Use it when migrating engine worker blocks into Compose.

Boundaries

• Project worker lifecycle belongs to Compose, not config.yaml or iii worker.
• For function and trigger code, use iii-core-primitives.
• For worker-specific HTTP, queue, cron, state, or pubsub behavior, use that worker's docs.