Download Wasmtime 43.0.0

43.0.0
Released 2026-03-20.
Added
- Wasmtime now supports the WASIp3 snapshot 0.3.0-rc-2026-03-15.
#12557
- The number of frames captured in backtrace collection can now be configured.
#12542
- Wasmtime now supports fine-grained operator cost configuration for when fuel
is enabled.
#12541
- Configuring the gc_support option is now possible through the C API.
#12630
- Configuring the concurrency_support option is now possible through the C
API.
#12703
- Debugging-related APIs have been added to access all modules and instances on
a store.
#12637
- All store entities now expose a "unique ID" for debugging purposes.
#12645
- Cranelift's x64 backend now supports the cls instruction for all integer
types.
#12644
Changed
- Internal refactoring and support necessary for handling OOM gracefully
throughout the runtime is proceeding apace. New APIs such as
FuncType::try_new are available in addition to many internal changes.
#12530
#12537
(... and many more ...)
- Wasmtime's representation of stack frames in the debugging API no longer
borrows the store itself and is instead represented as a handle.
#12566
- Wasmtime now unconditionally sets SO_REUSEADDR for guest-bound sockets.
#12597
- Cranelift now supports more VRegs which means effectively that larger
functions will be compilable by default rather than returning a "function too
large" error.
#12611
- WASIp3 implementations now limit returned memory by default for randomness and
HTTP headers.
#12745
#12761
Fixed
- Running wasmtime wizer over components with modules that contain an
_initialize function no longer removes the function to preserve the validity
of the component.
#12540
- Borrow state for host async tasks is now handled more correctly throughout
Wasmtime, especially in the face of cancellation.
#12550
- Bindings generation now accounts for the fact that future and stream are
not cloneable types.
#12155
- The impementation of UDP in WASIp2 has had some wakeup-related bugs fixed.
#12629
- Cancellation of host subtasks for component-model-async has been improved and
works more reliably.
#12640
- Subtask management for component-model-async now no longer reparents which
fixes a number spec-related divergences.
#12570
- Converting a wasmtime::Error into anyhow::Error and using downcast has
been fixed.
#12689
- Async stream/future read/write cancellation has had some corner cases fixed.
#12704
- Cranelift's timing infrastructure is now more robust in the face of buggy
system clocks.
#12709
- The currently running guest task has been corrected in a number of cases
related to component-model-async and cooperative threading.
#12718
#12735
#12736
#12737
- An issue of lost wakeups with the WASIp3 stdin implementation has been fixed.
#12745