RELEASES.md
Released 2026-08-20.
Wasmtime has an initial implementation of the component model fixed-length-lists feature. #12315
Wasmtime's reflection of component imports/exports now exposes external-id
information.
#13874
Cranelift's alias analysis pass now eliminates dead stores. #13806 #13947
Winch now supports the wasm SIMD proposal on AArch64. #13911 #13921 #13928 #13937 #13945 #13938 #13946 ...
Cranelift now supports an AVX512-VNNI lowering for the dot-product wasm
instruction and usdot on AArch64.
#14006
#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
Wasmtime now supports configurable fuel costs for variable-length wasm opcodes. #13931
Host-implemented traits in wasmtime-wasi-http are now the same across
wasip2/wasip3 and no longer require separate implementations/structures.
#13810
#13812
#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
Synchronous cancellation of streams/futures/subtasks now traps if the waitable was already in a waitable set. #13708
Winch is now flagged to be compatible with component-model-async. #13845
Wasmtime's pooling allocator now uses more sharding to reduce lock contention. #13840
Wasmtime now requires Rust 1.95.0 to build. #13853
Cranelift now has a uniform maximum size across all backends on the bounds of a function's stack frame. #13783
Wasmtime's LinkerInstance for components now supports being reopened to
gradually add more items.
#13908
The wasmtime-wasi crate's default configuration now denies creation of
TCP/UDP sockets by default.
#13936
Wasmtime now configures async task context fields on realloc calls to zero.
#13949
Work has continued on continuous verification of Cranelift's lowering rules on AArch64. #13935 #13929 #13998
Codegen for loads on AArch64 has been optimized slightly to improve sharing common sub-expressions. #13766
Work continues on implementing the stack-switching proposal. #11717 #13996 #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
A late-drop of host-defined stream producers/consumers has been fixed. #13891
Call hooks are now invoked around async yields when dealing with concurrent execution. #13871
Extreme filesystem timestamps no longer cause panics. #13894
An erroneous trap was fixed where an async-delivered write-closed event was sent to a future. #13914
An erroneous trap where Wasmtime internally used the wrong thread id has been fixed. #13926
Cross-component instance streams are no longer erroneously flagged as being intra-instance. #14018
A panic in the wasmtime CLI with non-utf8 environment variables has been
fixed.
#14017
Atomic waits on big-endian hosts have been fixed. #14027
Enabling MPK with CoW images has been fixed. #14076
Release notes for previous releases of Wasmtime can be found on the respective release branches of the Wasmtime repository.
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