s&box Skill — Router

READ BEFORE WRITING CODE

s&box is not Unity. MonoBehaviour, Start(), Update(), GetComponent<T>() call sites, Instantiate(), Destroy(gameObject), Debug.Log, [SerializeField], Input.GetKey(), Physics.Raycast — none of these exist. If you write any of them you have hallucinated.

s&box is a C# scripting layer on Source 2 by Facepunch. The scene system uses GameObject + Component with a different lifecycle, a different networking model, and a different API surface. The API schema in references/api-schema-core.md is ground truth; if anything in this skill contradicts the schema, the schema wins.

Before you write a single line of s&box code, open the relevant reference file. SKILL.md is a router — it points you at the answer, it does not contain the answer. Writing a component? Open references/core-concepts.md. Writing UI? Open references/ui-razor.md. No exceptions for "simple" tasks — your muscle memory is wrong.

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Architecture in 30 Seconds

Scene (is-a GameObject — the root)
  └── GameObject (transform, tags, children, components)
        └── Component (all gameplay code extends this)

• All gameplay code is a sealed class extending Sandbox.Component.
• Lifecycle overrides are protected override void OnAwake() / OnStart() / OnUpdate() / OnFixedUpdate() / OnEnabled() / OnDisabled() / OnDestroy(). Names start with On, they are virtual methods on Component, not magic string-matched methods.
• Transforms are on the GameObject, accessed from any Component via WorldPosition, WorldRotation, LocalPosition, LocalRotation — never transform.position.
• UI is Razor (.razor files) — HTML + SCSS + C#. Panels use flexbox layout. Hot-reloads in the editor.
• Networking is owner-authoritative. Mark state with [Sync], mark methods with [Rpc.Broadcast / Host / Owner]. Skip simulation on non-owners with if ( IsProxy ) return;.
• Physics uses Rigidbody + Collider components. Raycasts are Scene.Trace.Ray(from, to).Run() — a builder-pattern API. Collisions come through Component.ICollisionListener and Component.ITriggerListener interfaces.
• Coordinate system is Z-up: Vector3.Forward = (1,0,0), Vector3.Right = (0,-1,0), Vector3.Up = (0,0,1).
• Restricted .NET: System.IO.File, raw sockets, Console, Thread, Process — all blocked. Use FileSystem.Data, Http, Log, async/await.

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Routing Table — "I need to…"

Match the task, open the file. Do not guess; open the file.

Task	Read
Understand the scene/GameObject/Component model	references/core-concepts.md
Write a Component (lifecycle, [Property], Tags, async)	references/core-concepts.md
Spawn / clone / destroy a prefab	references/core-concepts.md → Prefabs
Fire a scene event (ISceneEvent<T>)	references/core-concepts.md → Scene Events
Write a GameObjectSystem	references/core-concepts.md → GameObjectSystem
Use ModelRenderer / SkinnedModelRenderer / bones / animgraph	references/components-builtin.md → Rendering
Use Rigidbody, any Collider, joints	references/components-builtin.md → Physics
Use CharacterController for movement	references/components-builtin.md → CharacterController
Use the full PlayerController (built-in FPS/TPS)	references/components-builtin.md → Gameplay
Set up a camera, HUD painter, post-processing	references/components-builtin.md → Camera, Post-Processing
Use lights, fog, envmap probes, skybox	references/components-builtin.md → Lighting, Environment
Add audio (SoundPointComponent, Sound.Play)	references/components-builtin.md → Audio
Use NavMeshAgent, NavMeshLink, query NavMesh	references/components-builtin.md → Navigation
Create particles, decals, trails, beams	references/components-builtin.md → Effects, Rendering
Write a Razor UI panel (.razor, PanelComponent, BuildHash)	references/ui-razor.md
Style with SCSS — flexbox, transitions, :intro / :outro, :bind	references/ui-razor.md → Styling, Layout System, Transitions
Use built-in controls (Button, TextEntry, DropDown, VirtualList)	references/ui-razor.md → Built-in Controls
Build a world-space panel or a NavigationHost app	references/ui-razor.md → WorldPanel, Navigation
Set up a lobby, connect/disconnect, query Connection	references/networking.md → Lobby & Connection
Network an object (NetworkMode, NetworkSpawn, ownership)	references/networking.md → Networked Objects, Ownership
Use [Sync] / [Sync(SyncFlags.X)] / [Change] / NetList / NetDictionary	references/networking.md → [Sync] Properties
Write RPCs ([Rpc.Broadcast/Host/Owner], NetFlags, caller info, filtering)	references/networking.md → RPC Messages
React to connections (INetworkListener, INetworkSpawn, snapshot data)	references/networking.md → Network Events
Use ISceneStartup for host vs client initialization	references/networking.md → Scene Startup
Dedicated server / #if SERVER / user permissions	references/networking.md → Dedicated Servers
Poll keyboard/mouse/controller input, haptics, glyphs	references/input-and-physics.md → Input
Raycast / sphere / box / capsule trace with tag filters	references/input-and-physics.md → SceneTrace
Access PhysicsWorld, gravity, physics events	references/input-and-physics.md → Physics World
Implement collision/trigger listeners	references/input-and-physics.md → Collision System
Use Vector3 / Rotation / Angles / Transform / BBox / Ray / Capsule	references/input-and-physics.md → Math Types
Use Time.Now, Time.Delta, TimeSince, TimeUntil	references/input-and-physics.md → Time
Draw debug gizmos (DrawGizmos, Gizmo.Draw)	references/input-and-physics.md → Gizmo
Need the full signature of GameObject, Component, Scene, Input, etc.	references/api-schema-core.md
Look up whether a given type exists & what it does	references/api-schema-extended.md
See a complete worked example of a pattern before writing your own	references/patterns-and-examples.md

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Unity → s&box Translation Table

Any time you write one of the left column, you are hallucinating. Use the right column.

Unity / Wrong	s&box / Correct
class Foo : MonoBehaviour	public sealed class Foo : Component
void Awake()	protected override void OnAwake()
void Start()	protected override void OnStart()
void Update()	protected override void OnUpdate()
void FixedUpdate()	protected override void OnFixedUpdate()
void OnEnable() / OnDisable()	protected override void OnEnabled() / OnDisabled()
void OnDestroy()	protected override void OnDestroy()
[SerializeField] float speed	[Property] public float Speed { get; set; }
[HideInInspector]	[Hide]
transform.position	WorldPosition (or GameObject.WorldPosition)
transform.localPosition	LocalPosition
transform.rotation	WorldRotation
transform.forward	WorldRotation.Forward
gameObject.SetActive(false)	GameObject.Enabled = false
Destroy(gameObject) / Destroy(this)	GameObject.Destroy() / Component.Destroy() / DestroyGameObject()
Instantiate(prefab, pos, rot)	prefab.Clone( pos, rot )
Instantiate(prefab); NetworkServer.Spawn(...)	prefab.Clone(pos).NetworkSpawn( owner )
GetComponent<T>() in Start/Update	GetComponent<T>() is fine; also Components.Get<T>( FindMode ) for ancestor/descendant searches
FindObjectOfType<T>() / FindObjectsOfType<T>()	Scene.Get<T>() / Scene.GetAll<T>() / Scene.GetAllComponents<T>()
GameObject.Find("Name")	Scene.Directory.FindByName("Name")
OnCollisionEnter(Collision c)	Implement Component.ICollisionListener.OnCollisionStart(Collision c)
OnTriggerEnter(Collider c)	Implement Component.ITriggerListener.OnTriggerEnter(Collider c)
Physics.Raycast(...)	Scene.Trace.Ray( from, to ).Run() (builder; returns SceneTraceResult)
Physics.OverlapSphere(pos, r)	Scene.Trace.Sphere( r, pos, pos ).RunAll()
Rigidbody.AddForce(f, ForceMode.Impulse)	Rigidbody.ApplyImpulse( f )
Rigidbody.AddForce(f)	Rigidbody.ApplyForce( f )
Rigidbody.velocity	Rigidbody.Velocity (capital V)
Input.GetKey(KeyCode.W)	Input.Down( "forward" ) — actions are strings configured in Project Settings
Input.GetKeyDown(...)	Input.Pressed( "action" )
Input.GetAxis("Horizontal") / Vertical	Input.AnalogMove (Vector3)
Input.mousePosition	Mouse.Position (Vector2)
Camera.main	Scene.Camera
Camera.main.ScreenPointToRay(Input.mousePosition)	Scene.Camera.ScreenPixelToRay( Mouse.Position )
StartCoroutine(Foo()) with IEnumerator	async Task Foo() with await Task.DelaySeconds(...); call as _ = Foo();
yield return new WaitForSeconds(1f)	await Task.DelaySeconds( 1f )
yield return null	await Task.Frame()
Debug.Log(x) / .LogWarning / .LogError	Log.Info(x) / Log.Warning(x) / Log.Error(x)
Time.time	Time.Now
Time.deltaTime	Time.Delta
Time.fixedDeltaTime	Scene.FixedDelta
Mathf.Lerp / Clamp / Approach	MathX.Lerp / Clamp / Approach
Random.Range(a, b)	Game.Random.Next(a, b) / Game.Random.NextSingle()
Vector3.forward = (0,0,1)	Vector3.Forward = (1,0,0) — s&box is Z-up; re-check every literal direction
SceneManager.LoadScene("name")	Scene.LoadFromFile("path/to/scene.scene") or Scene.Load( sceneResource )
DontDestroyOnLoad(go)	go.Flags = GameObjectFlags.DontDestroyOnLoad
Application.isPlaying	Game.IsPlaying (or !Game.IsEditor)
System.IO.File.ReadAllText(...)	FileSystem.Data.ReadAllText(...) / FileSystem.Mounted.ReadAllText(...)
UnityEngine.Networking.UnityWebRequest	Http.RequestStringAsync(...) / Http.RequestJsonAsync<T>(...)
Update() reads Input.* AND moves rigidbody	Read input in OnUpdate, move in OnFixedUpdate

If a Unity pattern isn't in the table, assume it doesn't exist in s&box and look it up in references/api-schema-core.md before writing it.

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The Ten Rules You Must Not Break

1. Every gameplay class extends Component. Not MonoBehaviour, not object, not ScriptableObject — just Component. Mark it sealed unless inheritance is required.
2. Lifecycle methods are protected override void On*(). If you wrote void Update() instead of protected override void OnUpdate(), your code does nothing.
3. Serialize fields with [Property]. Not [SerializeField], not public alone. [Property] both shows in the inspector and saves to prefab/scene.
4. Networked state uses [Sync]. Only the object owner may assign. Everyone else sees replicated values. Combine with [Change(nameof(Method))] for change callbacks.
5. Guard networked logic with if ( IsProxy ) return;. Every component that reads input or drives movement starts with this line — otherwise every client tries to move every player.
6. Ray/box/sphere traces go through Scene.Trace. It's a builder: Scene.Trace.Ray(from, to).UseHitboxes(true).WithoutTags(new[]{"player"}).Run() returns a SceneTraceResult. Never Physics.Raycast.
7. UI is Razor + flexbox. display: flex is the default and effectively the only layout. display: block does not exist. Properties :intro / :outro animate creation and deletion. Every root panel overrides BuildHash() to control re-render.
8. Coroutines don't exist — use async Task. await Task.DelaySeconds( n ), await Task.Frame(). Fire-and-forget with _ = MyTask();. The Component.Task property scopes cancellation to the GameObject lifetime.
9. Never touch blocked .NET APIs. System.IO.File, Console, Thread, raw sockets, System.Net.Http.HttpClient — use FileSystem.Data, Log, async/await, Http instead. Code that references these won't compile in the sandbox.
10. Look up every API before you use it. The schema is ground truth. If you can't find a method in api-schema-core.md or api-schema-extended.md, either you're guessing (stop) or it's nested on a specific type (search the topical reference).

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Project Structure (s&box Game)

An s&box game project (.sbproj) typically looks like:

MyGame/
├── MyGame.sbproj                 # project manifest
├── code/                         # C# source (gameplay code)
│   ├── GameManager.cs
│   ├── Player.cs
│   ├── weapons/
│   │   └── Rifle.cs
│   └── ui/
│       ├── Hud.razor             # Razor panel
│       ├── Hud.razor.scss        # auto-loaded stylesheet
│       └── InventoryPanel.razor
├── prefabs/                      # .prefab files
├── scenes/                       # .scene files
├── models/                       # .vmdl, .vmdl_c
├── materials/                    # .vmat, .vmat_c
├── sounds/                       # .sound, .wav, .mp3
├── ui/                           # UI images, textures
└── localization/
    └── en/
        └── mygame.json

Notable:

• .razor and .razor.scss files pair by name — the stylesheet auto-loads when the panel is built.
• .cs files are hot-reloaded in the editor; saving a file rebuilds and re-injects within seconds.
• Asset paths in code are forward-slash strings rooted at the project: Model.Load( "models/dev/box.vmdl" ).
• There is no Assets/ folder; paths are flat under the project root.

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A Reference Component (Shape Only — Not the Content)

This is the shape of a component. The content depends on what you're building — read the referenced file, then write it.

using Sandbox;

public sealed class MyComponent : Component
{
    [Property] public float Speed { get; set; } = 200f;
    [Property] public GameObject Target { get; set; }

    [Sync] public int Score { get; set; }

    TimeSince _lastAction;

    protected override void OnStart()
    {
        // runs once before first update
    }

    protected override void OnUpdate()
    {
        if ( IsProxy ) return;        // networking guard
        if ( !Target.IsValid() ) return;

        // per-frame logic (input, visuals, camera)
    }

    protected override void OnFixedUpdate()
    {
        if ( IsProxy ) return;
        // physics / movement — deterministic timestep
    }

    [Rpc.Broadcast]
    public void PlayEffect( Vector3 position )
    {
        // runs on all clients — cosmetic / non-authoritative
    }
}

For complete runnable examples — a full FPS controller, a networked player, a Razor HUD, a hitscan weapon, a NavMeshAgent AI, a physics grenade, a prefab spawner, a trigger pickup — see references/patterns-and-examples.md.

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Gotchas Captured From Real Builds

These are things that will bite you. They're documented deeper in the reference files; this is the quick-lookup list.

• ICollisionListener parameter names are collision, not other (the raw docs are wrong about this).
• Color, Capsule, Vector3, Rotation, Angles, Transform, BBox, Ray are global types, not Sandbox.*.
• LobbyConfig and LobbyPrivacy live in Sandbox.Network — you need using Sandbox.Network;.
• Scene is-a GameObject — it is the root GameObject. Scene.GetAllObjects(true) walks the tree.
• Most Component.ISomething interfaces are nested on Component: Component.IDamageable, Component.ICollisionListener, Component.ITriggerListener, Component.INetworkListener, Component.INetworkSpawn. But IGameObjectNetworkEvents is top-level Sandbox.IGameObjectNetworkEvents.
• ComponentList.GetOrCreate<T>( FindMode ) requires the FindMode arg. For the common "on this GameObject" case, use GetOrAddComponent<T>() on GameObject or Component instead.
• SceneTrace.WithoutTags / WithAnyTags / WithAllTags take string[] — not params. Pass new[] { "tag" }, or use WithTag(string) for the single-tag case.
• Game.Random is System.Random — NextSingle(), Next(n) work directly. The FromList extension exists but requires a defVal; list[Game.Random.Next(list.Count)] is simpler.
• FileSystem is a static facade. Actual methods are on BaseFileSystem, accessed via FileSystem.Data (game user data) or FileSystem.Mounted (mounted content).
• There is no standalone Log class — it's Sandbox.Diagnostics.Logger, but the global Log instance works fine everywhere.
• PlayerController.TraceBody has 4 parameters (the 4th is heightScale), not 3.
• Operators (Rotation * Rotation, Vector3 * Rotation) aren't listed in the API schema because they're systematically excluded — they do exist, use them normally.
• NavigationHost is in Sandbox.UI.Navigation, needs @using Sandbox.UI.Navigation in your Razor file.

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Verification Loop (When In Doubt)

If you're about to write an API call and you're not sure it exists:

1. Check the topical file for the area first (networking.md, ui-razor.md, etc.). Topical files include inline signatures for the APIs they cover.
2. If not there, check api-schema-core.md. It has full signatures for the ~50 most-used types.
3. If not there, check api-schema-extended.md. It's a namespace-organized index of 738 more types — find the type, then look up full signatures elsewhere if needed.
4. If a method or property is in NONE of the above, it does not exist. Do not write it. Revisit your design — there is almost certainly an s&box-idiomatic way to do what you want.

The schema under raw/api-schema.json is not shipped with the skill and is not for you to read directly; the reference files are the curated, searchable view of it.

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This file is a router. Reference files teach. Do not answer s&box questions from SKILL.md alone — open the relevant reference and read it.