bytecodealliance/wasmtime v48.0.0

on GitHub

48.0.0

Released 2026-08-20.

Added

• 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

Changed

• 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

Fixed

• 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