cargo / uniffi

uniffi

What changed in uniffi 0.32, from its official release notes, upgrade guides and advisories. Sources checked 2026-11-12.

9 breaking1 deprecations13 new APIs and options1 behavior and defaults2 tooling5 fixes and other

See which of these apply to your code, ranked, in your agent:

npx @unstale/cli init

uniffi 0.3231 changes

Kotlin and Python now fail to generate bindings when a type has an async primary constructor; exclude the constructor to get similar behavior.
0.32.0release notes
The method was removed and replaced by the GlobalConfig struct.
0.32.0release notes
UDL arguments now map to &[u8] instead of &Vec<u8>; Rust implementations taking &Vec<u8> must change, and Kotlin callers must pass a direct ByteBuffer rather than ByteArray.
0.32.0release notes
The flag now expects a global config file; old-style flat uniffi.toml overrides produce a warning and are ignored.
0.32.0release notes
The method now takes a MetadataCommand instance and CargoMetadataOptions instead of a no_deps flag.
0.32.0release notes
Ruby enum constructors now require named parameters.
0.32.0release notes
The experimental pipeline bindgen code was reworked, requiring external binding generators that use it to be reworked.
0.32.0release notes
[ByRef] bytes now cross the FFI as a pointer-and-length ForeignBytes value instead of RustBuffer; external bindings must lower the foreign-language buffer for the call without copying.
0.32.0release notes
A new struct manages configuration and replaces BindgenPathsLayer::get_config().
0.32.0release notes

The with_foreign flag is deprecated in favor of rust, foreign.
0.32.0release notes

The tokio async_runtime option can now be applied to trait exports, wrapping each method's FFI scaffolding future in async_compat::Compat.
0.32.0release notes
Custom Types can have docstrings in some languages.
0.32.0release notes
HashSet can now be used with proc-macros.
0.32.0release notes
derive(uniffi::Enum) now allows literal number suffixes.
0.32.0release notes
This configuration option lets specific records remain mutable when generate_immutable_records is enabled in Kotlin and Swift.
0.32.0release notes
The proc-macro name attribute can rename record fields.
0.32.0release notes
Ruby now supports async.
0.32.0release notes
Standard Rust traits are exposed for generated Ruby code.
0.32.0release notes
Ruby now supports sync foreign traits.
0.32.0release notes
Foreign code can transfer &[u8] / [ByRef] bytes to Rust without copying through RustBuffer; support excludes Ruby and async functions.
0.32.0release notes
Traits can be exported for foreign-only implementations; #[uniffi::export(rust, foreign)] supports both Rust and foreign implementations.
0.32.0release notes
Items can be excluded from generated bindings using uniffi.toml.
0.32.0release notes
Kotlin objects expose a property that returns true if the Rust reference no longer exists.
0.32.0release notes

Box<T> automatically implements FFI traits when T does, allowing direct use in enum variants and function parameters without NewType wrappers.
0.32.0release notes

Recursive enum and record cycles are detected and bindings are generated with indirect in Swift and forward references in Python.
0.32.0release notes
UniFfiTag is exempt from clippy::exhaustive_structs so downstream projects may depend on it.
0.32.0release notes

Generated Kotlin code no longer triggers compiler warnings.
0.32.2release notes
Fixed checksum failure on aarch64 for Kotlin.
0.32.1release notes
Fixed compile errors when exporting ambiguous method names.
0.32.0release notes
Fixed a bug that sometimes prevented renaming items inside a submodule.
0.32.0release notes
Code generation now works correctly for all kinds of enums and custom types.
0.32.0release notes