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Roadmap

This roadmap is a living document representing projected timelines for WASI releases. Goals and projections are provisional and subject to revision.

WASI Releases​

WASI point releases occur every two months, on the first Thursday of that month, on a release train model: a regular cadence in which releases are published regardless of the enhancements and fixes that are "ready for the train." Point releases include smaller features and bug fixes, while major features and breaking changes are generally reserved for major versions.

WASI P3​

WASI 0.3.0 was released on June 11, 2026. WASI P3 support is available in Wasmtime 43+ and jco.

WASI P3 adds native async support to the Component Model and refactors WASI P2 interfaces to take advantage of native async primitives: async func, stream<T>, and future<T>. The wasi:io package is removed entirely, with its functionality absorbed into the Component Model's Canonical ABI. For a full overview of changes, see WASI P3.

Implementations may continue to support WASI P2 alongside P3, either by implementing both versions or by virtualizing (polyfilling) P2 in terms of P3.

Following WASI 0.3.0, a series of incremental and backwards-compatible 0.3.x releases will occur on the release train model. These point releases are expected to include:

  • Cancellation automatically integrated with language idioms
  • Specialization of tuple<stream<u8>, future<result<trailers, http-error>>> existing in 0.3.0
  • Stream optimization with Canonical ABI built-ins for forwarding/splicing, skipping/writing-zeroes, stream data segment, and lulls
  • Caller-supplied buffers with more zero-copy in more scenarios
  • Threads: first cooperative, then preemptive

You can find more information in the WebAssembly CG presentation from February 2025.

Project timeline​

The provisional timeline for WASI releases is as follows:

The WASI timeline projects a P3 release in summer 2026