> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fapost.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Foundation contracts

> The interfaces and DTOs extensions are built against.

`fapost/foundation` is the public surface. Everything here is what an extension may
depend on; nothing under `App\…` is. See
[Stability policy](/extending/stability-policy).

## Extension registration

| Contract                                    | Role                                                                                                     |
| ------------------------------------------- | -------------------------------------------------------------------------------------------------------- |
| `Contracts\CoreRegistrarInterface`          | The single registration entry point for handlers, accessors, adapters, routes, schedules, and migrations |
| `Contracts\ActivatableInterface`            | `onActivate()` / `onDeactivate()` hooks                                                                  |
| `Lifecycle\AbstractPluginServiceProvider`   | Base provider for a Plugin                                                                               |
| `Lifecycle\AbstractSolutionServiceProvider` | Base provider for a Solution                                                                             |
| `Manifest\SolutionManifest`                 | Declares id, version, platform constraint, and required capabilities                                     |

## Flow engine

| Contract                                                                  | Role                                                      |
| ------------------------------------------------------------------------- | --------------------------------------------------------- |
| `Contracts\NodeHandlerInterface`                                          | A node's runtime behaviour                                |
| `Flow\Handlers\AbstractVersionedHandler`                                  | Base class deriving type and label from a `TYPE` constant |
| `Contracts\DataAccessorInterface`                                         | Reading module data under `module.*`                      |
| `Flow\Enums\StateNamespace`                                               | The canonical state namespaces                            |
| `Flow\Contracts\ContactWriterInterface`                                   | Mutating the contact from a handler                       |
| `Flow\Contracts\ScopedStateReaderInterface`                               | Reading state within a scope                              |
| `Flow\Contracts\ExpressionEngineInterface`                                | Evaluating expressions                                    |
| `Flow\Contracts\TriggerResolverInterface`, `TriggerTypeResolverInterface` | Resolving what starts a flow                              |
| `Flow\Call\CallTransportInterface`                                        | The transport behind the `call` node                      |

DTOs: `NodeExecutionContext`, `NodeExecutionResult`, `NodeExecutionStatus`,
`ExpressionContext`, `ResolvedTrigger`, `TriggerContext`, `CallContext`,
`CallRequest`, `CallResult`. Enums: `KeyboardMode`, `HistoryEventType`.

## Channels and ingress

| Contract                                                                                 | Role                                                   |
| ---------------------------------------------------------------------------------------- | ------------------------------------------------------ |
| `Channel\ChannelInterface`                                                               | Minimal channel identity across the extension boundary |
| `Channel\Ingress\ProvidesIngressSpecInterface`                                           | Declaring a provider's webhook contract                |
| `Channel\Ingress\IngressSpec`, `SignatureScheme`, `SignedRequest`, `IngressSpecExecutor` | Verifying and deduplicating inbound requests           |
| `Channel\WebhookRegistrarInterface`, `WebhookRegistrationPayload`                        | Registering the webhook with the provider              |

DTOs: `InboundWebhookPayload`, `IncomingMessage`, `IncomingMessageType`,
`IncomingMedia`.

## Messaging

| Contract                                   | Role                                                       |
| ------------------------------------------ | ---------------------------------------------------------- |
| `Messaging\MessageSenderInterface`         | Sending a message                                          |
| `Messaging\ProviderSenderInterface`        | Delivering through one concrete provider                   |
| `Messaging\TypingCapableProviderInterface` | Optional typing indicator, via `ProcessingIndicatorHandle` |

DTOs: `OutboundMessage`, `MessagePayload`, `DeliveryResult`, `OutgoingMessage`,
`OutgoingMessageType`, `SendResult`.

## Media

| Contract                                | Role                           |
| --------------------------------------- | ------------------------------ |
| `Media\ChannelMediaUploaderInterface`   | Uploading media to a provider  |
| `Media\ChannelMediaDownloaderInterface` | Fetching media from a provider |
| `Media\MediaBlobReadInterface`          | Reading a stored blob          |

DTOs: `UploadContext`, `UploadResult`, `DownloadResult`. Enum: `MediaKind`.

## Retrieval

`Contracts\RagAdapterInterface` with `RagQueryContext`, `StructuredRagResult`, and
`RagConfidence`.

## Analytics

`Analytics\Contracts\AnalyticsWriterInterface`, with `AnalyticsEvent` and
`AnalyticsEventType`.

## Other

`Contracts\ModelAttributeResolverInterface`, `Contracts\ModelUtilityInterface`,
`Action\ActionHandlerInterface`, `Support\Version`.

<Note>
  Generated PHP API documentation is produced separately with
  `composer run docs:build`, which writes Doctum output to `public/core`. That
  covers every class in the repository; this page covers the ones you are allowed
  to depend on.
</Note>