--- title: "anyio Breaking Changes on PyPI | Since.dev" description: "What each anyio release removed, renamed or changed: 221 breaking changes in 7 versions on PyPI, each with its source." canonical_url: https://since.dev/packages/pypi/anyio last_updated: 2026-07-12 --- # anyio breaking changes Every breaking API change we have recorded in anyio on PyPI: 221 breaking changes in 7 versions. Below are its newest 6 versions, removals and renames first, each with its source. Newest change July 12, 2026 ## 4.14.2 3 breaking changes, first published July 12, 2026. - **Behavior changed** `ByteReceiveStream.receive` Calls passing a max_bytes that is not a positive integer now raise ValueError. Pass a positive integer for max_bytes. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.2) - **Behavior changed** `CapacityLimiter.acquire_nowait` On the trio backend, a failed non-blocking acquire now raises anyio.WouldBlock. Code that catches trio.WouldBlock must catch anyio.WouldBlock instead. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.2) - **Behavior changed** `CapacityLimiter.acquire_nowait_on_behalf_of` On the trio backend, a failed non-blocking acquire now raises anyio.WouldBlock. Code that catches trio.WouldBlock must catch anyio.WouldBlock instead. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.2) ## 4.14.0 47 breaking changes, first published June 15, 2026. - **Behavior changed** `anyio.CancelScope` Instances of these classes no longer accept arbitrary new attributes, so code or subclasses that set extra attributes on them will break. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.0) - **Behavior changed** `anyio.CapacityLimiter` Instances of these classes no longer accept arbitrary new attributes, so code or subclasses that set extra attributes on them will break. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.0) - **Behavior changed** `anyio.Condition` Instances of these classes no longer accept arbitrary new attributes, so code or subclasses that set extra attributes on them will break. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.0) - **Behavior changed** `anyio.Event` Instances of these classes no longer accept arbitrary new attributes, so code or subclasses that set extra attributes on them will break. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.0) - **Behavior changed** `anyio.Lock` Instances of these classes no longer accept arbitrary new attributes, so code or subclasses that set extra attributes on them will break. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.0) - **Behavior changed** `anyio.ResourceGuard` Instances of these classes no longer accept arbitrary new attributes, so code or subclasses that set extra attributes on them will break. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.0) - **Behavior changed** `anyio.Semaphore` Instances of these classes no longer accept arbitrary new attributes, so code or subclasses that set extra attributes on them will break. [github.com](https://github.com/agronholm/anyio/releases/tag/4.14.0) - **Signature changed** `anyio.abc.AsyncBackend.run_async_from_thread` Was @classmethod def run_async_from_thread(cls, func: Callable\[\[Unpack\[PosArgsT\]\], Awaitable\[T_Retval\]\], args: tuple\[Unpack\[PosArgsT\]\], token: object) -> T_Retval; now @classmethod def run_async_from_thread(cls, func... [pypi.org](https://pypi.org/project/anyio/4.14.0/) - **Signature changed** `anyio.abc.TaskGroup.start` The annotation now accepts only callables returning coroutine-like objects, not arbitrary awaitables. Type-checked code passing other awaitables will fail type checking. [pypi.org](https://pypi.org/project/anyio/4.14.0/) - **Signature changed** `anyio.abc.TaskGroup.start_soon` start_soon() returns a TaskHandle instead of its previous return value. Code that relies on the old return value must be updated. [pypi.org](https://pypi.org/project/anyio/4.14.0/) And 37 more in this version. ## 4.13.0 6 breaking changes, first published March 24, 2026. - **Removed** Python 3.9 is no longer supported by this release; users on Python 3.9 must upgrade their interpreter or stay on an older anyio version. [github.com](https://github.com/agronholm/anyio/releases/tag/4.13.0) - **Signature changed** `anyio.functools.AsyncLRUCacheWrapper.__init__` Was def \_\_init\_\_(self, func: Callable\[P, Awaitable\[T\]\], maxsize: int | None, typed: bool, always_checkpoint: bool); now def \_\_init\_\_(self, func: Callable\[P, Awaitable\[T\]\], maxsize: int | None, typed: bool, always_checkpoint: bool, ttl: int... [pypi.org](https://pypi.org/project/anyio/4.13.0/) - **Signature changed** `anyio.functools.lru_cache` Was def lru_cache(func: Callable\[P, Coroutine\[Any, Any, T\]\] | Callable\[..., T\] | None = None, /, \*, maxsize: int | None = 128, typed: bool = False, always_checkpoint: bool = False) -> AsyncLRUCacheWrapper\[P, T\] |... [pypi.org](https://pypi.org/project/anyio/4.13.0/) - **Signature changed** `anyio.streams.file.FileReadStream.__init__` Was def \_\_init\_\_(self, file: BinaryIO); now def \_\_init\_\_(self, file: IO\[bytes\]). [pypi.org](https://pypi.org/project/anyio/4.13.0/) - **Signature changed** `anyio.streams.file.FileStreamAttribute.file` Was file: BinaryIO; now file: IO\[bytes\]. [pypi.org](https://pypi.org/project/anyio/4.13.0/) - **Signature changed** `anyio.streams.file.FileWriteStream.__init__` Was def \_\_init\_\_(self, file: BinaryIO); now def \_\_init\_\_(self, file: IO\[bytes\]). [pypi.org](https://pypi.org/project/anyio/4.13.0/) ## 4.12.1 4 breaking changes, first published January 6, 2026. - **Removed** `anyio.abc.AsyncBackend.create_blocking_portal` AsyncBackend.create_blocking_portal was removed in anyio 4.12.1 [pypi.org](https://pypi.org/project/anyio/4.12.1/) - **Removed** `anyio.abc.BlockingPortal.__new__` BlockingPortal.\_\_new\_\_ was removed in anyio 4.12.1 [pypi.org](https://pypi.org/project/anyio/4.12.1/) - **Behavior changed** Functions that previously raised the private NoCurrentAsyncBackend exception now raise the public NoEventLoopError. Code that catches NoCurrentAsyncBackend must catch NoEventLoopError instead. [github.com](https://github.com/agronholm/anyio/releases/tag/4.12.1) - **Signature changed** `anyio.functools.AsyncLRUCacheWrapper.__init__` Was def \_\_init\_\_(self, func: Callable\[..., Awaitable\[T\]\], maxsize: int | None, typed: bool, always_checkpoint: bool); now def \_\_init\_\_(self, func: Callable\[P, Awaitable\[T\]\], maxsize: int | None, typed: bool, always_checkpoint: bool). [pypi.org](https://pypi.org/project/anyio/4.12.1/) ## 4.12.0 125 breaking changes, first published November 28, 2025. - **Removed** `anyio.from_thread.CancelScope` anyio.from_thread.CancelScope was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) - **Removed** `anyio.from_thread.create_task_group` anyio.from_thread.create_task_group was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) - **Removed** `anyio.from_thread.Event` anyio.from_thread.Event was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) - **Removed** `anyio.from_thread.EventLoopToken` anyio.from_thread.EventLoopToken was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) - **Removed** `anyio.from_thread.get_async_backend` anyio.from_thread.get_async_backend was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) - **Removed** `anyio.from_thread.get_cancelled_exc_class` anyio.from_thread.get_cancelled_exc_class was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) - **Removed** `anyio.from_thread.NoEventLoopError` anyio.from_thread.NoEventLoopError was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) - **Removed** `anyio.from_thread.PosArgsT` anyio.from_thread.PosArgsT was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) - **Removed** `anyio.from_thread.run_eventloop` anyio.from_thread.run_eventloop was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) - **Removed** `anyio.from_thread.T_co` anyio.from_thread.T_co was removed in anyio 4.12.0 [pypi.org](https://pypi.org/project/anyio/4.12.0/) And 115 more in this version. ## 4.11.0 10 breaking changes, first published September 23, 2025. - **Renamed** `anyio.from_thread.AsyncBackend` Use anyio.lowlevel.AsyncBackend instead. [pypi.org](https://pypi.org/project/anyio/4.11.0/) - **Behavior changed** After a TCP stream is closed, send() on asyncio now raises ClosedResourceError instead of BrokenResourceError, so code catching BrokenResourceError in this case must catch ClosedResourceError instead. [github.com](https://github.com/agronholm/anyio/releases/tag/4.11.0) - **Default changed** `anyio.abc.TaskStatus` Code relying on the previous Any default type argument may see different type checking results and should specify the type argument explicitly. [github.com](https://github.com/agronholm/anyio/releases/tag/4.11.0) - **Configuration changed** Users of Trio older than 0.31.0 must upgrade Trio to install or run this release. [github.com](https://github.com/agronholm/anyio/releases/tag/4.11.0) - **Signature changed** `anyio.CancelScope.cancel` Was def cancel(self) -> None; now def cancel(self, reason: str | None = None) -> None. [pypi.org](https://pypi.org/project/anyio/4.11.0/) - **Signature changed** `anyio.from_thread.run` Was def run(func: Callable\[\[Unpack\[PosArgsT\]\], Awaitable\[T_Retval\]\], \*args: Unpack\[PosArgsT\]) -> T_Retval; now def run(func: Callable\[\[Unpack\[PosArgsT\]\], Awaitable\[T_Retval\]\], \*args: Unpack\[PosArgsT\], token: EventLoopToken | None = None)... [pypi.org](https://pypi.org/project/anyio/4.11.0/) - **Signature changed** `anyio.from_thread.run_sync` Was def run_sync(func: Callable\[\[Unpack\[PosArgsT\]\], T_Retval\], \*args: Unpack\[PosArgsT\]) -> T_Retval; now def run_sync(func: Callable\[\[Unpack\[PosArgsT\]\], T_Retval\], \*args: Unpack\[PosArgsT\], token: EventLoopToken | None = None) -> T_Retval. [pypi.org](https://pypi.org/project/anyio/4.11.0/) - **Signature changed** `anyio.lowlevel.current_token` Was def current_token() -> object; now def current_token() -> EventLoopToken. [pypi.org](https://pypi.org/project/anyio/4.11.0/) - **Signature changed** `anyio.pytest_plugin.pytest_configure` Was def pytest_configure(config: Any) -> None; now def pytest_configure(config: pytest.Config) -> None. [pypi.org](https://pypi.org/project/anyio/4.11.0/) - **Signature changed** `anyio.pytest_plugin.pytest_pycollect_makeitem` Was def pytest_pycollect_makeitem(collector: Any, name: Any, obj: Any) -> None; now def pytest_pycollect_makeitem(collector: pytest.Module | pytest.Class, name: str, obj: object) -> None. [pypi.org](https://pypi.org/project/anyio/4.11.0/) ## Check your code These are the changes. To see which of them reach your code, [scan a public repository](https://since.dev/scan.md), or have your coding agent call `check_code` with your manifest or lockfile over [MCP](https://since.dev/docs.md#mcp). [The API](https://since.dev/docs.md#api) reads every change in every version, not only the newest. 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