RFC: Composed Async

[ubugeeei]

Summary

Unify Vue's asynchronous reads and optimistic writes around the reactive graph while preserving the broader Composed Async motivation.

• explain why the current <Suspense> model remains incomplete: dependencies are component-shaped, async setup is implicit and coarse, revalidation follows tree shape, pending causes are opaque, and mutations use a separate consistency model
• allow readonly computed() getters to return Promises and expose ComputedRef<Awaited<T>>
• propagate pending and rejected states through derived computed values
• let existing <Suspense> handle initial fallback and hold committed content during revalidation
• add optimistic(target, { update, run, commit }) with reconciliation, rollback, and deterministic rebasing for overlapping mutations
• avoid the previously proposed <script async setup>, v-defer, and <Suspense :with> APIs

The proposal remains transport- and cache-agnostic. It does not define server actions, form submission, automatic cancellation, or a source-level pending API.

Links

• Full rendered proposal
• Solid 2.0 RC: The Big Reveal
• Vue Suspense documentation

Validation

• pnpm dlx prettier@3.6.2 --single-quote false --check active-rfcs/0045-composed-async.md
• git diff --check
• verified all linked reference pages return HTTP 200

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Important: Do NOT comment on this PR. Please use a corresponding RFC discussion thread for feedback, as it provides branched discussions that are easier to follow.