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0.22.x drops the iii- prefix from the workers that ship with the engine, removes one engine CLI flag, and removes one Rust SDK constructor. The worker rename is a deprecation with a migration window: the old names still resolve but emit a warning. The other two are clean breaks. Apply the steps below that touch surfaces your project uses.

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Step 1: Rename the always-running workers

The following workers lost their iii- prefix. Rename them wherever you reference them: config.yaml entries, iii worker add commands, etc.
config.yaml
The old prefixed names still resolve, so a project keeps booting after the upgrade, but iii worker add prints a deprecation warning for them and a future release will remove the aliases. Rename now to clear the warning. All other workers with iii- prefix keep those prefixes for now. Most of them will be removed in a future version.

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Step 2: Remove duplicate worker entries from config.yaml

The engine now rejects a config.yaml that lists both a deprecated name and its replacement, failing to boot with a Duplicate worker configurations error that names the conflicting pair. Remove or rename those entries.
Keep exactly one entry per worker. Listing both iii-http and http (or any other old/new pair) is a hard startup error that stops the engine from booting. Remove the deprecated entry.

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Step 3: Drop the removed engine flag

The --use-default-config engine flag is removed. Running iii with no config.yaml now creates one with an empty workers: list: it prompts in an interactive terminal and writes the file without asking in a non-interactive session (CI, containers). Drop the flag from scripts, Dockerfiles, and CI. The recommended way to start a new iii project is with: iii project init.
See Engine for the current no-config behavior.

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Step 4: Update the Rust register-function API

The Rust SDK removed RegisterFunction::new_async_with_bad_request. Register async handlers with RegisterFunction::new_async; a deserialization failure on the input now surfaces as Error::Serde rather than through a caller-supplied mapper.
This step applies only to Rust workers that called the removed constructor. Node, Python, Browser, and Go workers need no change here. This handler was only in the Rust SDK a short time so it’s unlikely that code was using it.

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Migration checklist

  • Rename the always-running workers to their unprefixed names in config.yaml, iii worker add, and trigger types (Step 1)
  • Remove any duplicate old/new worker entry from config.yaml (Step 2)
  • Drop --use-default-config from scripts and CI (Step 3)
  • Replace Rust new_async_with_bad_request with new_async (Step 4)

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Result

The project boots on 0.22.x with no deprecation warnings: the always-running workers use their unprefixed names, config.yaml lists each worker once, the engine starts without the removed flag, and Rust workers build against the current register-function API.