Sækja Wasmtime 48.0.0

## 48.0.0

Released 2026-08-20.

### Added

• Wasmtime has an initial implementation of the component model
fixed-length-lists feature.
[#12315](https://github.com/bytecodealliance/wasmtime/pull/12315)

• Wasmtime's reflection of component imports/exports now exposes `external-id`
information.
[#13874](https://github.com/bytecodealliance/wasmtime/pull/13874)

• Cranelift's alias analysis pass now eliminates dead stores.
[#13806](https://github.com/bytecodealliance/wasmtime/pull/13806)
[#13947](https://github.com/bytecodealliance/wasmtime/pull/13947)

• Winch now supports the wasm SIMD proposal on AArch64.
[#13911](https://github.com/bytecodealliance/wasmtime/pull/13911)
[#13921](https://github.com/bytecodealliance/wasmtime/pull/13921)
[#13928](https://github.com/bytecodealliance/wasmtime/pull/13928)
[#13937](https://github.com/bytecodealliance/wasmtime/pull/13937)
[#13945](https://github.com/bytecodealliance/wasmtime/pull/13945)
[#13938](https://github.com/bytecodealliance/wasmtime/pull/13938)
[#13946](https://github.com/bytecodealliance/wasmtime/pull/13946)
...

• Cranelift now supports an AVX512-VNNI lowering for the dot-product wasm
instruction and `usdot` on AArch64.
[#14006](https://github.com/bytecodealliance/wasmtime/pull/14006)
[#14054](https://github.com/bytecodealliance/wasmtime/pull/14054)

• Wasmtime's `bindgen!` macro now has an `include_component_type` option to
generate a `COMPONENT_TYPE` constant with the encoded type of the world being
bound.
[#14013](https://github.com/bytecodealliance/wasmtime/pull/14013)

• Wasmtime now supports configurable fuel costs for variable-length wasm
opcodes.
[#13931](https://github.com/bytecodealliance/wasmtime/pull/13931)

### Changed

• Host-implemented traits in `wasmtime-wasi-http` are now the same across
wasip2/wasip3 and no longer require separate implementations/structures.
[#13810](https://github.com/bytecodealliance/wasmtime/pull/13810)
[#13812](https://github.com/bytecodealliance/wasmtime/pull/13812)
[#13835](https://github.com/bytecodealliance/wasmtime/pull/13835)

• Wasmtime will now use the `process_madvise` syscall on Linux where available
which can improve the performance of the pooling allocator when the
deallocation batch size is configured to larger than 1.
[#13830](https://github.com/bytecodealliance/wasmtime/pull/13830)

• Synchronous cancellation of streams/futures/subtasks now traps if the waitable
was already in a waitable set.
[#13708](https://github.com/bytecodealliance/wasmtime/pull/13708)

• Winch is now flagged to be compatible with component-model-async.
[#13845](https://github.com/bytecodealliance/wasmtime/pull/13845)

• Wasmtime's pooling allocator now uses more sharding to reduce lock contention.
[#13840](https://github.com/bytecodealliance/wasmtime/pull/13840)

• Wasmtime now requires Rust 1.95.0 to build.
[#13853](https://github.com/bytecodealliance/wasmtime/pull/13853)

• Cranelift now has a uniform maximum size across all backends on the bounds of
a function's stack frame.
[#13783](https://github.com/bytecodealliance/wasmtime/pull/13783)

• Wasmtime's `LinkerInstance` for components now supports being reopened to
gradually add more items.
[#13908](https://github.com/bytecodealliance/wasmtime/pull/13908)

• The `wasmtime-wasi` crate's default configuration now denies creation of
TCP/UDP sockets by default.
[#13936](https://github.com/bytecodealliance/wasmtime/pull/13936)

• Wasmtime now configures async task context fields on `realloc` calls to zero.
[#13949](https://github.com/bytecodealliance/wasmtime/pull/13949)

• Work has continued on continuous verification of Cranelift's lowering rules
on AArch64.
[#13935](https://github.com/bytecodealliance/wasmtime/pull/13935)
[#13929](https://github.com/bytecodealliance/wasmtime/pull/13929)
[#13998](https://github.com/bytecodealliance/wasmtime/pull/13998)

• Codegen for loads on AArch64 has been optimized slightly to improve sharing
common sub-expressions.
[#13766](https://github.com/bytecodealliance/wasmtime/pull/13766)

• Work continues on implementing the stack-switching proposal.
[#11717](https://github.com/bytecodealliance/wasmtime/pull/11717)
[#13996](https://github.com/bytecodealliance/wasmtime/pull/13996)
[#14052](https://github.com/bytecodealliance/wasmtime/pull/14052)

• Permissions for `wasi-filesystem` in the implementation of the `wasmtime-wasi`
crate have been simplified to either read-write or read-only for a directory.
[#14010](https://github.com/bytecodealliance/wasmtime/pull/14010)

### Fixed

• A late-drop of host-defined stream producers/consumers has been fixed.
[#13891](https://github.com/bytecodealliance/wasmtime/pull/13891)

• Call hooks are now invoked around async yields when dealing with concurrent
execution.
[#13871](https://github.com/bytecodealliance/wasmtime/pull/13871)

• Extreme filesystem timestamps no longer cause panics.
[#13894](https://github.com/bytecodealliance/wasmtime/pull/13894)

• An erroneous trap was fixed where an async-delivered write-closed event was
sent to a future.
[#13914](https://github.com/bytecodealliance/wasmtime/pull/13914)

• An erroneous trap where Wasmtime internally used the wrong thread id has been
fixed.
[#13926](https://github.com/bytecodealliance/wasmtime/pull/13926)

• Cross-component instance streams are no longer erroneously flagged as being
intra-instance.
[#14018](https://github.com/bytecodealliance/wasmtime/pull/14018)

• A panic in the `wasmtime` CLI with non-utf8 environment variables has been
fixed.
[#14017](https://github.com/bytecodealliance/wasmtime/pull/14017)

• Atomic waits on big-endian hosts have been fixed.
[#14027](https://github.com/bytecodealliance/wasmtime/pull/14027)

• Enabling MPK with CoW images has been fixed.
[#14076](https://github.com/bytecodealliance/wasmtime/pull/14076)