Migrating a World from the v4 spec to v5

This skill is for a package that implements World from @workflow/world: a storage, queue and stream backend the Workflow runtime talks to. It is not for application code. If the task is bumping an app's workflow dependency, use the migrating-workflow-v4-to-v5 skill instead; if the app both uses Workflow and ships its own World, run that skill first and this one second.

An app on the Vercel, Local or Postgres World needs nothing from this skill. Those ship with the SDK and are already on the v5 spec.

One change dominates the work. Event ID allocation is required, is not visible from the type signatures, and a World that skips it type-checks, starts runs, and fails on the first replay. Do that part first, then the mechanical rewrites. Do not begin with the type errors: they are the small half, and finishing them produces a World that looks migrated and is not.

Intake

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