vercel__workflow/packages/world

@workflow/world

Core interfaces and types for Workflow SDK storage backends.

This package defines the World interface that abstracts workflow storage, queuing, authentication, and streaming operations. Implementation packages like @workflow/world-local and @workflow/world-vercel provide concrete implementations.

Used internally by @workflow/core and world implementations. Should not be used directly in application code.

Implementation constraint: no mutable module state

A World implementation must not keep mutable state at module scope. Hold it on the World instance, or, when it is genuinely process-wide (an ID generator whose sequence must not fork, a log-once latch), on globalThis via globalSingleton() from @workflow/utils.

@workflow/world-local and @workflow/world-vercel are bundled into the host application's server build, and a bundler keys module identity on (resource, layer): Next.js alone compiles instrument, app-route, ssr and edge as separate module graphs, so one process holds one copy of every module in these packages per layer. A top-level let, or a const holding a Map, is therefore per-copy state rather than the singleton it reads as.

A world loaded at runtime through WORKFLOW_TARGET_WORLD is deduped by Node's module cache and does not have this problem today, but that is a property of how it is loaded, not of how it is written, and it has changed before (vercel/workflow#3493). scripts/lint/module-scope-state.mjs enforces the rule across every published world package; see docs/content/worlds/*/building-a-world.mdx for the author-facing version.