Move workers from config.yaml to Compose

Manual migration to the breaking worker-compose.yaml engine and project model.

iii 0.23 removes the legacy worker lifecycle. There is no compatibility period or automatic migrator: iii worker, the worker::* functions, engine fallback through iii.toml, and engine-managed project workers are gone.

A managed project now has one worker-compose.yaml. Its engine: section configures the engine; containers: declares project workers. If a direct config.yaml still declares a project worker, startup and reload stop with UNSUPPORTED_CONFIG_WORKERS and list every entry to migrate.

Hand the migration to a coding agent

The steps below are mechanical, so a coding agent with shell access to the project can carry them out. Copy this prompt into the agent, then review the resulting worker-compose.yaml before starting it.

Prompt

Migrate this iii project from config.yaml worker declarations to worker-compose.yaml (iii 0.23). Read https://iii.dev/docs/upgrading/workers-to-compose.md first and follow it exactly.

Before changing anything:
1. Locate every config.yaml (including any path passed with --config), any existing worker-compose.yaml, iii.lock, the configuration worker's storage directory (./config by default), and the state, queue, and stream data paths. Copy all of them into ./backup-pre-compose/, preserving each source's relative path so two files with the same name never collide, and stop if a destination already exists. Do not delete the originals.
2. Make sure this project is not already supervised separately (ex. systemd, Kubernetes). If the repository does not make this clear, ask me before writing the file.

Write worker-compose.yaml:
- Move configuration, iii-worker-manager, iii-http-functions, iii-stream, and iii-sandbox into the engine.workers map. The map value is the worker config itself; drop the old nested config: key. Multiple instances use a #instance suffix.
- Do not declare iii-engine-functions, iii-telemetry, or iii-observability. The engine injects them.
- Move every other worker under containers:. Rename it per the table on the page (iii-state or state becomes state, iii-http or http becomes http, and so on). Registry workers use package://api.workers.iii.dev/<name> with an explicit version; local workers use path://. Copy each old config: value to config_override and keep every storage path unchanged.
- Translate iii-exec commands into scripts.pre_run, scripts.run, and scripts.post_run.
- Pin versions from iii.lock or the registry. Never invent a version number.
- For a separately supervised engine, keep only the five engine-owned workers in the list-shaped config.yaml and omit engine: from the Compose file.

Stored configuration: for every worker whose configuration id changed (for example iii-state to state), read the old value with configuration::get and raw: true so ${VAR} templates are copied as templates rather than expanded values, put it under config_override or write it to the new id with configuration::set, and verify the new worker before removing the old entry. Do not rename YAML files as a shortcut.

Never edit engine-config.yaml in the Compose state directory. Compose generates it at <project-dir>/.iii/compose/<namespace>/engine-config.yaml by default, or $III_COMPOSE_STATE_DIR/<project-slug>/<namespace>/engine-config.yaml when III_COMPOSE_STATE_DIR is set.

Start the project. iii compose stays in the foreground, so run it in a second terminal or send it to the background with its output in a log file, then wait until it has started every container:
  iii compose --namespace dev --up --file worker-compose.yaml
  (for a separately supervised engine: start the engine with iii --config config.yaml under its own supervisor, then iii compose --namespace dev --engine <that engine's ws:// URL> --up --file worker-compose.yaml)

With the daemon running, show me the output of:
  iii trigger -n dev compose::status file=worker-compose.yaml
  iii trigger engine::workers::list
  iii trigger engine::triggers::list
If the engine is not on localhost port 49134, add --address <host> and --port <port> to each iii trigger command.

If startup reports UNSUPPORTED_CONFIG_WORKERS, UNSUPPORTED_ENGINE_WORKER, ENGINE_WORKER_IS_INJECTED, or any other error from the Common errors list on the page, fix the cause and rerun. Do not work around an error by deleting a worker.

Report back: the resolved path and diff of every configuration file you changed, including any passed with --config, the full new worker-compose.yaml, which stored configuration ids you migrated, and anything you could not migrate.

Back up the project

Keep a copy of:

• config.yaml and any path passed with --config
• an existing worker-compose.yaml
• the configuration worker’s storage directory, ./config/ by default
• state, queue, and stream data paths
• iii.lock, if the project used the removed installer

Rollback requires those files and the previous iii binary. The 0.23 engine does not accept the old project-worker declarations.

Build the new engine section

Move these five engine-owned worker configs from list entries in config.yaml to the direct engine.workers map:

Worker	Why it remains engine-owned
configuration	Owns schemas, values, and change notifications used by engine and project workers.
iii-worker-manager	Owns engine WebSocket and RBAC listeners.
iii-http-functions	Provides outbound HTTP functions inside the engine process.
iii-stream	Uses engine internals and engine-owned adapters. Deprecated.
iii-sandbox	Owns the builtin sandbox lifecycle.

iii-stream is deprecated (iii-stream) and will be removed in an upcoming release. Behavior is unchanged for now, so move its configuration as shown. Plan the migration with Migrate from iii-stream and pubsub.

The map value is the worker config itself; do not keep the old nested config: key. Multiple instances use a #instance suffix, such as iii-worker-manager#rbac.

worker-compose.yaml

# namespace: default
engine:
  url: ws://127.0.0.1:49134
  registration_namespace_grace_ms: 5000
  workers:
    configuration:
      adapter:
        name: fs
        config:
          directory: ./config
    iii-worker-manager:
      host: 127.0.0.1
      port: 49134
    iii-http-functions: {}
    iii-stream:
      host: 127.0.0.1
      port: 3112
    iii-sandbox:
      auto_install: true

engine.url defaults to ws://127.0.0.1:49134. Compose writes the engine-only representation to <project-dir>/.iii/compose/<daemon-namespace>/engine-config.yaml by default. When III_COMPOSE_STATE_DIR is set, the path is $III_COMPOSE_STATE_DIR/<project-slug>/<daemon-namespace>/engine-config.yaml. Compose writes the file with owner-only permissions and starts the engine from it. Do not edit that generated file.

Remove explicit iii-engine-functions, iii-telemetry, and iii-observability entries. The engine injects them automatically, and declaring one under engine.workers fails.

Move project workers to containers

Old name	Compose package/configuration id
iii-http or http	http
iii-cron or cron	cron
iii-queue or queue	queue
iii-state or state	state
iii-pubsub or pubsub	pubsub (deprecated)
iii-bridge	bridge
iii-exec	no package; use Compose scripts

pubsub is deprecated (pubsub) and will be removed in an upcoming release. Behavior is unchanged for now. See Migrate from iii-stream and pubsub.

Copy each old project worker’s config: value to config_override, preserve its storage paths, and pin the package version.

worker-compose.yaml

containers:
  state:
    worker: package://api.workers.iii.dev/state
    version: "0.22.2"
    config_name: state
    config_override:
      adapter:
        name: kv
        config:
          store_method: file_based
          file_path: ./data/state_store.db
  http:
    worker: package://api.workers.iii.dev/http
    version: "0.21.3"
    config_name: http
    config_override:
      host: 127.0.0.1
      port: 3111
  app:
    worker: path://.
    start_after: [state, http]
    scripts:
      pre_run: pnpm build
      run: pnpm start
      post_run: pnpm cleanup

Translate iii-exec commands into pre_run, run, and post_run. Custom local workers use path://; registry workers use package:// plus a version.

You can also add a registry worker after the managed daemon is running:

iii trigger -n dev compose::add worker=http
iii trigger -n dev compose::add worker=state

compose::add writes containers: and restarts affected containers. It never edits engine: or restarts the engine. A registry root of kind engine is rejected and points to engine.workers.<name> when the worker is configurable.

Preserve stored configuration

Standalone packages use unprefixed configuration ids. A value stored as iii-state is not copied to state automatically.

1. Before upgrading, read the old value with configuration::get.
2. Put it under config_override, or write it to the new id with configuration::set.
3. Verify the new worker before removing the old stored entry.

Do not rename only the YAML file: filesystem-backed entries also contain id and schema metadata.

Start the result

For a managed engine, the file owns both lifecycles:

iii compose --namespace dev --up --file worker-compose.yaml

The explicit namespace (dev) addresses compose::* and overrides the file’s namespace: for its containers. Changing engine: while the daemon runs returns ENGINE_RESTART_REQUIRED; stop and restart that Compose invocation. A second file with engine: returns ENGINE_ALREADY_OWNED.

For an engine supervised separately by systemd or Kubernetes, keep its five allowed workers in the list-shaped config.yaml, start it directly, omit engine: from the Compose file, and supply the existing URL:

iii --config config.yaml
iii compose --namespace dev --engine ws://127.0.0.1:49134 --up --file worker-compose.yaml

Run those commands under separate supervisors. Explicit --engine has highest priority and may override an engine.url in the Compose file. Without either value, Compose uses III_URL, then defaults to ws://127.0.0.1:49134.

Verify the migration:

iii trigger -n dev compose::status file=worker-compose.yaml
iii trigger engine::workers::list
iii trigger engine::triggers::list

Common errors

• UNSUPPORTED_CONFIG_WORKERS: direct config.yaml still contains project workers.
• UNSUPPORTED_ENGINE_WORKER: engine.workers contains a project or unknown worker.
• ENGINE_WORKER_IS_INJECTED: remove an automatically supplied internal worker.
• ENGINE_RESTART_REQUIRED: restart Compose to apply a changed engine section.
• ENGINE_ALREADY_OWNED: start the second managed file in a separate Compose invocation.
• ENGINE_SECTION_REQUIRES_MANAGED_START: an external daemon was asked to load a managed file.
• ENGINE_WORKER_IS_BUILTIN: compose::add was given an engine package as a root.
• CONTAINER_NAME_TAKEN: another live process owns the same (namespace, worker name).