# Merged threads on macOS and Windows

> Learn about threading changes on macOS and Windows in Flutter 3.35.




:::important
These breaking change docs are accurate, as of the release
under which they are published. Over time, the
workarounds described here might become inaccurate.
We don't, in general, keep these breaking change docs up
to date as of each release.

这些破坏性改动文档的准确性仅限于其发布时对应的版本。
随着时间的推移，文档中描述的方案可能会逐渐失效。
通常情况下，我们不会在每次发布新版本时都对这些文档进行同步更新。

The [breaking change index file](/release/breaking-changes)
lists the docs created for each release.

[破坏性改动列表](/release/breaking-changes) 
列出了每个版本的文档。

:::


## Summary

Flutter 3.35 merges the UI and platform threads by default on macOS and Windows.

## Context

Originally, Flutter had separate threads to produce UI frames and to
interact with the native platform.

The split-thread design prevented Flutter apps and plugins from using Dart FFI
to interoperate with native APIs that must be called on the platform thread.

## Description of change

Flutter 3.35 merges the UI and platform threads by default on macOS and Windows.

This mirrors iOS and Android, whose threads were merged by default in
Flutter 3.29.

## Migration guide

Merged threads should not affect your app.

If you suspect merged threads has regressed your app, please reach out on
[Issue 150525][].

## Timeline

Landed in version: 3.33.0-0.0.pre<br>
In stable release: 3.35

## References

Relevant issue:

* [Issue 150525][]

Relevant PRs:

* [PR 166536][]
* [PR 167472][]

[Issue 150525]: https://github.com/flutter/flutter/issues/150525
[PR 166536]: https://github.com/flutter/flutter/pull/166536
[PR 167472]: https://github.com/flutter/flutter/pull/167472