> ## Documentation Index > Fetch the complete documentation index at: https://usefused.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # harnest.extensions > Public Python signatures, fields, and methods. [All Python modules](https://usefused.com/docs/harnest/reference/api/overview.md) · [Import and compatibility guidance](https://usefused.com/docs/harnest/build/python-imports.md) ## Exports | Name | Kind | | - | - | | [`ActivatedExtension`](#activatedextension) | Class | | [`Extension`](#extension) | Class | | [`ExtensionContext`](#extensioncontext) | Class | | [`ExtensionContextUnavailableError`](#extensioncontextunavailableerror) | Class | | [`ExtensionImportError`](#extensionimporterror) | Class | | [`ExtensionNamespaceError`](#extensionnamespaceerror) | Class | | [`ExtensionStartContext`](#extensionstartcontext) | Class | | [`activate_extensions`](#activate_extensions) | Function | | [`extension_mutation`](#extension_mutation) | Function | | [`extension_namespaces`](#extension_namespaces) | Function | | [`release_extensions`](#release_extensions) | Function | ## ActivatedExtension One validated namespace module and its authored singleton. ```python theme={null} ActivatedExtension( descriptor: ExtensionDescriptor, module: ModuleType, extension: Extension[ExtensionContext], ) -> None ``` Fields (`—` means no declared default): | Field | Type | Default | | - | - | - | | `descriptor` | `ExtensionDescriptor` | `—` | | `module` | `ModuleType` | `—` | | `extension` | `Extension[ExtensionContext]` | `—` | > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `descriptor` | `ExtensionDescriptor` | Required | > | `module` | `ModuleType` | Required | > | `extension` | `Extension[ExtensionContext]` | Required | > > ```python theme={null} > from harnest.extensions import ActivatedExtension > > extension = ActivatedExtension(descriptor=..., module=..., extension=...) > ``` ## Extension Application-owned extension with task-local invocation context. ```python theme={null} Extension(*args: object, **kwargs: object) -> 'Extension[ContextT]' ``` > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `*args` | `object` | Optional | > | `**kwargs` | `object` | Optional | > > ```python theme={null} > from harnest.extensions import Extension > > extension = Extension() > ``` ### Extension.start ```python theme={null} async Extension.start(context: 'ExtensionStartContext') -> None ``` Initialize application-scoped resources after dependencies start. > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `context` | `'ExtensionStartContext'` | Required | > > ```python theme={null} > from harnest.extensions import Extension > > extension: Extension > await extension.start(context=...) > ``` ### Extension.stop ```python theme={null} async Extension.stop() -> None ``` Release application-scoped resources before dependencies stop. > [accordion] Example > > ```python theme={null} > from harnest.extensions import Extension > > extension: Extension > await extension.stop() > ``` ### Extension.create\_context ```python theme={null} Extension.create_context(context: ExtensionContext) -> ContextT ``` Adapt the managed invocation base to an extension-specific context. > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `context` | `ExtensionContext` | Required | > > ```python theme={null} > from harnest.extensions import Extension > > extension: Extension > result = extension.create_context(context=...) > ``` ### Extension.context Return the task-local extension context for the active invocation. > [accordion] Example > > ```python theme={null} > from harnest.extensions import Extension > > extension: Extension > value = extension.context > ``` ## ExtensionContext Revocable invocation base that extension-specific contexts may extend. ```python theme={null} ExtensionContext(extension_name: str) -> None ``` > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `extension_name` | `str` | Required | > > ```python theme={null} > from harnest.extensions import ExtensionContext > > context = ExtensionContext(extension_name=...) > ``` ### ExtensionContext.extension\_name Return the extension whose invocation authority this context carries. > [accordion] Example > > ```python theme={null} > from harnest.extensions import ExtensionContext > > context: ExtensionContext > value = context.extension_name > ``` ### ExtensionContext.active Report whether the owning managed invocation is still active. > [accordion] Example > > ```python theme={null} > from harnest.extensions import ExtensionContext > > context: ExtensionContext > value = context.active > ``` ### ExtensionContext.continuations Return provider-bound suspension authority for this invocation. > [accordion] Example > > ```python theme={null} > from harnest.extensions import ExtensionContext > > context: ExtensionContext > value = context.continuations > ``` ## ExtensionContextUnavailableError An extension context was used outside its managed invocation. > [accordion] Example > > ```python theme={null} > from harnest.extensions import ExtensionContextUnavailableError > > try: > ... > except ExtensionContextUnavailableError as error: > ... > ``` ## ExtensionImportError An authored extension module violates its export contract. > [accordion] Example > > ```python theme={null} > from harnest.extensions import ExtensionImportError > > try: > ... > except ExtensionImportError as error: > ... > ``` ## ExtensionNamespaceError An extension namespace cannot be activated or safely released. > [accordion] Example > > ```python theme={null} > from harnest.extensions import ExtensionNamespaceError > > try: > ... > except ExtensionNamespaceError as error: > ... > ``` ## ExtensionStartContext Application facts available while one same-process extension starts. The context deliberately excludes invocation credentials and framework storage authorities. Extensions may reuse only explicitly named application storage whose lifecycle Harnest has already started. Obtain this object from the owning Harnest API; its constructor includes runtime bindings. Fields (`—` means no declared default): | Field | Type | Default | | - | - | - | | `extension_name` | `str` | `—` | | `framework` | `str` | `—` | | `root_agent_name` | `str` | `—` | > [accordion] Example > > ```python theme={null} > from harnest.extensions import ExtensionStartContext > > context: ExtensionStartContext # returned by Harnest, not constructed directly > ``` ### ExtensionStartContext.storage ```python theme={null} ExtensionStartContext.storage(name: str, expected_type: type[Any] | None = None) -> Any ``` Return one named custom store without exposing the registry. > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `name` | `str` | Required | > | `expected_type` | `type[Any] \| None` | `None` | > > ```python theme={null} > from harnest.extensions import ExtensionStartContext > > context: ExtensionStartContext > result = context.storage(name=...) > ``` ### ExtensionStartContext.continuations Return provider-bound completion authority when explicitly declared. > [accordion] Example > > ```python theme={null} > from harnest.extensions import ExtensionStartContext > > context: ExtensionStartContext > value = context.continuations > ``` ## activate\_extensions Activate a dependency-ordered extension set as one namespace transaction. ```python theme={null} activate_extensions(descriptors: Sequence[ExtensionDescriptor]) -> tuple[ActivatedExtension, ...] ``` > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `descriptors` | `Sequence[ExtensionDescriptor]` | Required | > > ```python theme={null} > from harnest.extensions import activate_extensions > > result = activate_extensions(descriptors=...) > ``` ## extension\_mutation Audit one exact durable operation after commit or on correlated failure. ```python theme={null} extension_mutation(extension_name: str, operation: str, *, trigger: Literal['agent', 'user']) -> AsyncIterator[None] ``` > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `extension_name` | `str` | Required | > | `operation` | `str` | Required | > | `trigger` | `Literal['agent', 'user']` | Required | > > ```python theme={null} > from harnest.extensions import extension_mutation > > async with extension_mutation(extension_name=..., operation=..., trigger=...): > ... > ``` ## extension\_namespaces Activate extensions for one bounded compiler or test operation. ```python theme={null} extension_namespaces(descriptors: Sequence[ExtensionDescriptor]) -> Iterator[tuple[ActivatedExtension, ...]] ``` > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `descriptors` | `Sequence[ExtensionDescriptor]` | Required | > > ```python theme={null} > from harnest.extensions import extension_namespaces > > with extension_namespaces(descriptors=...): > ... > ``` ## release\_extensions Release one acquisition without disturbing a competing extension set. ```python theme={null} release_extensions(descriptors: Sequence[ExtensionDescriptor]) -> None ``` > [accordion] Parameters and example > > | Parameter | Type | Default | > | - | - | - | > | `descriptors` | `Sequence[ExtensionDescriptor]` | Required | > > ```python theme={null} > from harnest.extensions import release_extensions > > release_extensions(descriptors=...) > ``` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.