> For the complete documentation index, see [llms.txt](https://threadforge.gitbook.io/threadlink-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://threadforge.gitbook.io/threadlink-documentation/engineer-reference/procedures.md).

# Engineering Procedures

## Introducing a subsystem

* [ ] Declare `class X : ThreadlinkSubsystem<X>` with the required lifecycle interfaces.
* [ ] Provide a public parameterless constructor or a `WeavingFactory<X>.OnCreate` delegate.
* [ ] Register the factory in `UserWeavingFactory.Register()`.
* [ ] Weave the subsystem in `UserSubsystemsConfig.WeaveSubsystems()`, after the subsystems it depends on.
* [ ] Subscribe in `Initialize()`; unsubscribe in `Discard()`, then call `base.Discard()`.
* [ ] Override `Report` to show its state in the Runtime Monitor (see [Monitoring](/threadlink-documentation/engineer-reference/monitoring.md)).

See [Implementing a Subsystem](/threadlink-documentation/engineer-reference/implementing-a-subsystem.md). Check it in the [Runtime Monitor](/threadlink-documentation/engineer-reference/editor-tooling.md#runtime-monitor): it should appear in the graph, linked to the core.

## Introducing an Iris event

* [ ] Declare it in `Iris.Events.User.txt` and save.
* [ ] Document its delegate signature and use it everywhere. A mismatched subscription logs an error; a mismatched publication does nothing.

## Introducing a scene

* [ ] Map the scene through the Addressables Mapping Window, and keep it out of Build Settings: only the bootstrap scene belongs there (see [Configuration](/threadlink-documentation/engineer-reference/configuration.md#bootstrap-scene)).
* [ ] Implement `Nexus.ISceneEntry` with its music and ambience; override `OnFinishedLoadingAsync` for setup.
* [ ] Choose its `PhysicsMode`: a scene resident alongside others needs its own physics scene.
* [ ] Provide a listener for the four fader and loading-screen `Func` events.
* [ ] Load it only through Nexus: `TransitionAsync` or `PresentAsync` to show it, `HoldAsync` to keep it resident. Nexus discards its objects whenever it unloads (see [Nexus](/threadlink-documentation/engineer-reference/nexus.md#residency-holds)). Release every hold.

## Introducing a stacked interface

* [ ] Build the prefab with a `CanvasGroup` and a component derived from `UserInterface` or `UserInterface<S>`.
* [ ] Map it through the Addressables Mapping Window.
* [ ] Add its prefab identifier to `DextraConfig.interfacePointers`.

## Using a custom update loop

* [ ] Set the User Config update-loop mode to `Custom`.
* [ ] Do not install `ThreadlinkPlayerLoop` yourself; it is internal, and Native mode owns it.
* [ ] Publish `OnUpdate`, `OnFixedUpdate` and `OnLateUpdate` from your driver at the right points in the frame.
* [ ] Keep the event contract Chronos, Aura, Dextra and project listeners expect.

## Introducing a Sentinel runtime module

* [ ] Implement an `ISentinelPlatform` / `SentinelPlatform` for one exact `SentinelPlatformMarker` + `SentinelDistribution` pair.
* [ ] Register a `SentinelModuleDescriptor` through `SentinelModuleRegistry.Register` at `AfterAssembliesLoaded`.
* [ ] Advertise only the capabilities it implements.
* [ ] Register platform-level services on the platform and account-scoped services on `ISentinelAccount` implementations.
* [ ] Provide an `ISentinelBuildModule` for the same pair; without it, builds for that pair fail.

See [Sentinel Modules](/threadlink-documentation/engineer-reference/sentinel/modules.md).