Wasmtime 50.0.0 ڈاؤن لوڈ

## 50.0.0

Released 2026-10-20.

### Added

• Wasmtime now supports the WebAssembly compact imports proposal, disabled by
default, via `Config::wasm_compact_imports`.
[#14335](https://github.com/bytecodealliance/wasmtime/pull/14335)

• The Wasmtime CLI now has options to configure unsafe intrinsics and
compile-time builtins.
[#14279](https://github.com/bytecodealliance/wasmtime/pull/14279)

• The Wasmtime CLI and C API can now enable the component model's canonical
names and accessors features.
[#14344](https://github.com/bytecodealliance/wasmtime/pull/14344)
[#14497](https://github.com/bytecodealliance/wasmtime/pull/14497)

• A new `Store::gc_heap_grow` method can be used to manually grow the GC heap
of a store.
[#14341](https://github.com/bytecodealliance/wasmtime/pull/14341)

• A new `ResourceAny::resource_drop_concurrent` method can be used to drop a
guest resource with only an `Accessor`.
[#14362](https://github.com/bytecodealliance/wasmtime/pull/14362)

• A new `Engine::release_idle_pool_memory` method can be used to release memory
kept resident by the pooling allocator for idle slots.
[#14419](https://github.com/bytecodealliance/wasmtime/pull/14419)
[#14507](https://github.com/bytecodealliance/wasmtime/pull/14507)

• A new off-by-default `task-group-hook` feature enables embedders to associate
guest-to-host calls with their corresponding host-to-guest calls when using
component-model-async.
[#14416](https://github.com/bytecodealliance/wasmtime/pull/14416)

• The `wasmtime-wasi` and `wasmtime-wasi-http` crates now support "named
imports", the `implements` field of the component model.
[#14275](https://github.com/bytecodealliance/wasmtime/pull/14275)

• The `wasmtime explore` command now supports components and has resizable
panes.
[#14426](https://github.com/bytecodealliance/wasmtime/pull/14426)
[#14427](https://github.com/bytecodealliance/wasmtime/pull/14427)
[#14458](https://github.com/bytecodealliance/wasmtime/pull/14458)

• The debugger now exposes shared memories to gdbstub.
[#14087](https://github.com/bytecodealliance/wasmtime/pull/14087)

• Winch now supports tail calls on x86_64 and AArch64.
[#14349](https://github.com/bytecodealliance/wasmtime/pull/14349)

• Cranelift has initial support for some x86_64 APX instructions.
[#13916](https://github.com/bytecodealliance/wasmtime/pull/13916)

• The `wasmtime serve` command can now inherit listening sockets from a service
manager (e.g. systemd socket units) with a new `--systemd-listenfd` option,
can serve on Unix sockets, and can automatically exit when idle with a new
`--idle-process-timeout` option.
[#14294](https://github.com/bytecodealliance/wasmtime/pull/14294)
[#14320](https://github.com/bytecodealliance/wasmtime/pull/14320)
[#14392](https://github.com/bytecodealliance/wasmtime/pull/14392)

### Changed

• Epoch deadline and call-hook callbacks now receive a `StoreHookState`
instead of a `StoreContextMut`, which only allows access to the `T` in a
`Store<T>`.
[#14386](https://github.com/bytecodealliance/wasmtime/pull/14386)

• The `wasmtime` CLI no longer enables WASIp0 (`wasi_unstable`) by default. It
can be enabled with `-Spreview0`.
[#14479](https://github.com/bytecodealliance/wasmtime/pull/14479)

• Winch no longer enables the GC types, exceptions, or tail-call proposals by
default as support for these is not yet Tier 1.
[#14449](https://github.com/bytecodealliance/wasmtime/pull/14449)
[#14502](https://github.com/bytecodealliance/wasmtime/pull/14502)

• `Accessor::spawn` now takes an async closure instead of an `AccessorTask`.
[#14376](https://github.com/bytecodealliance/wasmtime/pull/14376)

• Component-model-async has been updated to the latest specification：the
`cancellable` immediate has been removed from intrinsics, `subtask.cancel`
semantics have been refined, `task.cancel` now traps before the cancel event
is delivered, and use of stream/future handles after the other end has been
dropped now traps.
[#14244](https://github.com/bytecodealliance/wasmtime/pull/14244)
[#14340](https://github.com/bytecodealliance/wasmtime/pull/14340)
[#14342](https://github.com/bytecodealliance/wasmtime/pull/14342)
[#14378](https://github.com/bytecodealliance/wasmtime/pull/14378)
[#14382](https://github.com/bytecodealliance/wasmtime/pull/14382)

• Component-model-async now periodically yields during concurrent work to avoid
starving other host tasks.
[#14460](https://github.com/bytecodealliance/wasmtime/pull/14460)

• The performance of async guest-to-host calls in component-model-async has
been improved by lazily creating host tasks, and sync-to-sync adapters no
longer need to call `{enter,exit}-sync-call` in many cases.
[#14350](https://github.com/bytecodealliance/wasmtime/pull/14350)
[#14270](https://github.com/bytecodealliance/wasmtime/pull/14270)

• Wasmtime now drops cached compiler contexts between compiling
modules/components, reducing sustained memory usage.
[#14314](https://github.com/bytecodealliance/wasmtime/pull/14314)

• Cranelift's alias analysis is faster and more precise, and GC struct fields,
array elements, and GC header fields now all have their own alias regions.
[#14290](https://github.com/bytecodealliance/wasmtime/pull/14290)
[#14425](https://github.com/bytecodealliance/wasmtime/pull/14425)
[#14351](https://github.com/bytecodealliance/wasmtime/pull/14351)
[#14353](https://github.com/bytecodealliance/wasmtime/pull/14353)

• Wasmtime now uses bulk libunwind section registration when available.
[#14304](https://github.com/bytecodealliance/wasmtime/pull/14304)

• Fuel is now charged for more host allocations made with `Val`.
[#14415](https://github.com/bytecodealliance/wasmtime/pull/14415)

• Default `wasi:http` hooks now classify connection and TLS errors in more
detail.
[#14501](https://github.com/bytecodealliance/wasmtime/pull/14501)

• `wasi:http` now always accepts an empty path-with-query.
[#14446](https://github.com/bytecodealliance/wasmtime/pull/14446)

• The CLI now rejects zero for the `--http-outgoing-body-*` options.
[#14448](https://github.com/bytecodealliance/wasmtime/pull/14448)

• Work continues on implementing the stack-switching proposal.
[#14140](https://github.com/bytecodealliance/wasmtime/pull/14140)
[#14369](https://github.com/bytecodealliance/wasmtime/pull/14369)
[#14398](https://github.com/bytecodealliance/wasmtime/pull/14398)
[#14441](https://github.com/bytecodealliance/wasmtime/pull/14441)

• Wasmtime now requires Rust 1.97.0 to compile.
[#14466](https://github.com/bytecodealliance/wasmtime/pull/14466)

• The pooling allocator now scans further than a fixed set of region and
additionally correctly resets pages that have been paged out.
[#14357](https://github.com/bytecodealliance/wasmtime/pull/14357)

### Fixed

• Converting a borrowed `Resource<T>` or `ResourceDynamic` created with
`new_borrow` into a `ResourceAny` outside of a component call no longer
panics. The borrow is now lowered into the guest when the call happens, and
`ResourceAny::resource_drop` is no longer required for such borrows.
[#14384](https://github.com/bytecodealliance/wasmtime/pull/14384)

• Recursive `run_concurrent` is now allowed for disparate stores.
[#14302](https://github.com/bytecodealliance/wasmtime/pull/14302)

• Fuel is now correctly saved and restored around `call_ref` and exception
catches in Cranelift, and buffered fuel charges in a module's start function
are no longer dropped.
[#14407](https://github.com/bytecodealliance/wasmtime/pull/14407)
[#14391](https://github.com/bytecodealliance/wasmtime/pull/14391)

• The `check-write` budget is now enforced in `wasi:http` outgoing bodies and
some `wasi:io` output streams.
[#14408](https://github.com/bytecodealliance/wasmtime/pull/14408)
[#14429](https://github.com/bytecodealliance/wasmtime/pull/14429)
[#14505](https://github.com/bytecodealliance/wasmtime/pull/14505)

• `Store::set_epoch_deadline` no longer overflows with very large deltas.
[#14513](https://github.com/bytecodealliance/wasmtime/pull/14513)

• JIT code is now made coherent with the instruction cache correctly on
AArch64.
[#14454](https://github.com/bytecodealliance/wasmtime/pull/14454)

• Native stack-walking on macOS arm64 has been fixed.
[#14303](https://github.com/bytecodealliance/wasmtime/pull/14303)

• A stack overflow translating a variant with a huge number of cases between
components has been fixed.
[#14355](https://github.com/bytecodealliance/wasmtime/pull/14355)

• Resource aliases are now preserved when stubbing unknown imports.
[#14396](https://github.com/bytecodealliance/wasmtime/pull/14396)

• `bindgen!` now uses fully-qualified paths for prelude types to avoid
collisions with WIT type names.
[#14543](https://github.com/bytecodealliance/wasmtime/pull/14543)

• Validation of `if` without `else` in the presence of subtyping has been fixed.
[#14334](https://github.com/bytecodealliance/wasmtime/pull/14334)

• A debug assertion in `ref.test` of internalized `externref`s has been fixed.
[#14315](https://github.com/bytecodealliance/wasmtime/pull/14315)

• Cranelift now allows returns via `xmm1` with `WindowsFastCall` for
`extern "Rust"`.
[#14361](https://github.com/bytecodealliance/wasmtime/pull/14361)

• `cranelift-object` now sets symbol flags correctly and returns an error,
instead of panicking, for data objects declared with different TLS values.
[#14519](https://github.com/bytecodealliance/wasmtime/pull/14519)
[#14469](https://github.com/bytecodealliance/wasmtime/pull/14469)

• Winch now handles unreachable `try_table`, emits fuel updates before throwing
exceptions, and preserves typed `select` result types for GC stack maps.
[#14379](https://github.com/bytecodealliance/wasmtime/pull/14379)
[#14297](https://github.com/bytecodealliance/wasmtime/pull/14297)
[#14455](https://github.com/bytecodeall