# Component (asset type) A component is a reusable behavior + data unit attached to an entity. The component file declares public fields, methods, and lifecycle callbacks; the engine instantiates one per attachment and drives its hooks every frame. Components are the primary unit of gameplay code — movement, AI, animations, UI panels, network sync, and per-entity state all live here. ## When to use one - You need per-entity state that survives across frames. - You need per-entity behavior driven by engine lifecycle hooks (`start`, `update`, `onDestroy`). - You want to expose configurable fields to designers / `entity.spawn` callers / scenes without code changes. If you need a stateless pure-function library, use a `.module`. If you need to generate content declaratively, use a `.service`; compute work belongs in a `.computeShader`. ## Where it lives - Source: `/zero/source/.../<Name>.component/` - Identity: `<Name>` (the `.component` suffix strips from the identity, but the folder retains the suffix on disk). - Folder shape: - `init.luau` (or `init.lua`) — declares the component. **Required.** - `README.md` — instance-level documentation. **Required.** - `.metadata` — agent-editable tags + free-form fields. **Required.** The structural contract is enforced by `asset.validate` against this type's `type.yaml`. ## How to create one Always start with the scaffold — it guarantees the folder shape matches `type.yaml` from the moment it's on disk: ```luau asset.create("component", "<Name>") -- Creates: /zero/source/<Name>.component/ -- init.luau (canonical declare + public block + hooks stubbed) -- README.md (instance README template) ``` After scaffolding, edit `init.luau` to fill in the actual fields and behaviour. The component registers as soon as the file is written — hot-reload is automatic; no engine restart required. ## How it operates 1. **Registration.** Writing `init.luau` into a `.component/` folder indexes the asset, mints a guid (in the `.meta` sidecar), and surfaces the type to the engine's component registry. Same-frame visible to `entity.component.add`. 2. **Attachment.** `entity(id).component.add(name, data)` (or the batch form `tools.use("entityOps", "addComponents", targets, { [name] = data })`) attaches an instance. The `data` table's fields override the component's declared defaults; omitted fields take the declared default. The `data` values are copied into `public.*` BEFORE `awake()` runs. 3. **Lifecycle.** The hooks run in this order: - `awake()` — same frame as attach, immediately after the data copy. Initialise state, set up native bridges, register with other systems. Other components on the same entity may not have awoken yet. - `start()` — the next frame. Every component on the entity has completed `awake()` by then, so cross-component setup is safe here. - `update(dt)` — same frame as `start()`, then every frame after, for as long as the gameplay clock is running. `fixedUpdate(dt)` runs once per physics step, straight after it, with the step's `dt`, so a frame can run it several times or not at all; `editorUpdate(dt)` runs while the clock is held. Which of them ticks is decided by `engine.mode` AND `engine.paused` together — see **Per-frame hooks and the two axes** below, and `man modes`. - `onDestroy()` — when the component is removed via `component.remove` or when the owning entity is despawned. Release resources, drop native ECS components. For the full list (`onEnable`, `onDisable`, `fixedUpdate`, `editorUpdate`, `onPropertyChanged`, `onAssetReload`, `onModuleReload`, `onBeforeSave`, …) and the timing details, **read `man components` — that is the canonical lifecycle reference. Generic component patterns (declare blocks, public fields, sync, ECS bindings, typed methods) all live there.** 4. **Public surface.** Fields declared in `public` are inspectable, editable in the inspector, and persist with the entity. Methods are declared on that same table with a colon — `typed function public:method(args)` — and every one of them takes the component ref as `self`, so a caller invokes it with a colon too: `entity(id).component.get(name):method(args)`. That is the one calling convention a component ref answers to: the reflection methods `ref:fields()` / `ref:getField(name)` / `ref:setField(name, value)` take the same spelling. A function the chunk declares at file scope (`function helper()`) is the component's own, reachable from its hooks under its bare name; `public` is what the ref carries. 5. **Settings and the Inspector card.** `type.yaml` names the component's settings schema as `settings: { schema: { instance: "init.luau", export: "public" } }`: the `public` table IS the schema, and its values live on each entity the component is on, so `asset.schema(componentRef)` answers the Field descriptors and no values file exists. On an entity the Inspector shows the component as a card whose generic `settings` section edits those fields as typed controls, each edit checked against the schema and written to the live component as one undoable operation. `type.yaml` also names `inspector: { instance: "inspector.luau" }`: a component that ships an `inspector.luau` beside its `init.luau` shapes its card — the file returns `{ sections, replace, order }` (see `assetTypes/README.md`, "`inspector:`"), each section's `build(ctx)` reading `ctx.component` (the live component) and `ctx.selection.id` (the entity). `SceneModule.component/inspector.luau` replaces `settings` with the bound module's declared inputs. 6. **Events.** An `events` block declares typed moments the component fires from inside — `events = { onHit = Event({ dmg = Field.number(0, NoSync) }) }`. The owner fires with `events.onHit:fire({ dmg = 10 })`; outside code subscribes through the proxy's subscribe-only facade, `entity(id).component.get(name).events.onHit:connect(fn)` (`:once` / `:wait` too). Pass `Sync` as the event's second argument to replicate a fire to other peers. Events let one component react to another's moments without polling. Full reference: **`man components`**, Events section. 7. **Hot reload.** Editing `init.luau` reloads the component definition; live instances are reconciled with the new declaration in-place, and each crosses one lifecycle boundary: `onDestroy()` ends the running life, then `awake()` and `start()` construct the one that replaces it, and `update()` resumes on the next frame. `public` and `private` values carry across; module-level `local`s belong to the chunk, so the new life starts with them at their initial values and its `awake`/`start` are what fill them in. Whatever the old life handed elsewhere — a subscription, a shared registration, a spawned entity — is released in `onDestroy`, the call that pairs with the construction about to run. An edit that leaves the source byte-identical crosses no boundary at all. A field carries its value across when something stated it: a key of the `data` table the instance was attached with (a scene record's data is that table), or a write made since. Every other field takes the edited source's declared default, so changing a default reaches every instance that left the field to it. An instance that states its own value for a field whose default the edit changed keeps that value, and the reload logs a `[HotReload]` warning naming the field, the entity, the value kept and both defaults. ## Discovery - `asset.list("component")` — every registered component (engine + world + libraries). - `asset.inspect("<name>")` — identity, scope, public fields, lifecycle methods, source path, and this type README. `detail` carries the component's declared `fields`, `methods`, and `events`, parsed from its source — `tools.use("assets","describe", "<name>")` renders it as markdown, so a component's events are visible without opening its source. - `ls /zero/source/<Name>.component` lists the files the folder holds. - `entity(id).component.list()` — components attached to an entity. ## Per-frame hooks and the two axes `engine.mode` (`"edit"` / `"play"`) and `engine.paused` (the gameplay clock) are independent, and the per-frame hooks read them separately: - `update(dt)` / `fixedUpdate(dt)` tick while **the gameplay clock is running** — whichever mode the engine is in. - `editorUpdate(dt)` ticks while **the clock is held** — because the mode is `edit`, or because play is paused — and also alongside `update` whenever edit is running. Which gives four states, and this table is the contract: | `engine.mode` | `engine.paused` | hooks that tick | |---|---|---| | `edit` | `true` | `editorUpdate` | | `edit` | `false` | `update`, `fixedUpdate`, `editorUpdate` | | `play` | `false` | `update`, `fixedUpdate` | | `play` | `true` | `editorUpdate` | Entering edit sets `paused = true` and entering play sets it back to `false`, so a session that never writes `engine.paused` only ever sees rows 1 and 3 — which is where the shorthand "`update` is the play tick, `editorUpdate` is the edit tick" comes from. It is the two default rows of a four-row table, not the rule. **Row 2 is the one that surprises.** With `engine.paused = false` in edit — set by hand, or by a tool that advances the gameplay clock to sample it, such as a `capture.collage` given a `duration` — `update` and `editorUpdate` both fire, once each, every frame. A component that declares both and routes them to one body therefore runs that body **twice per frame**: ```luau local function drive(dt) ... end function update(dt) drive(dt) end function editorUpdate(dt) drive(dt) end -- twice per frame in row 2 ``` Nothing reports the doubling; it reads as an animation running at twice its intended speed. To get exactly one tick per frame in every row, ask which axis you meant and answer it in the body: ```luau function update(dt) drive(dt) end function editorUpdate(dt) if engine.paused then drive(dt) end end ``` A scene `entrypoint.luau` declaring the same two hook names is dispatched by the scene loader, not by this table: there `update` needs play AND running, `editorUpdate` needs edit, and play-paused ticks neither. Read `man scenes` before carrying a component's rule to an entrypoint. ## Authoring conventions - Annotate public fields with `--!desc` so the inspector + LSP show documentation alongside the field name. - Declare lifecycle hooks (`start`, `update`, `onDestroy`) explicitly rather than relying on engine defaults — readers can see at a glance what runs when. - Keep `update(dt)` cheap — it runs every frame per instance. Move heavy work to `start`, to a `.computeShader`, or behind a job (`man jobs`). - For multi-entity batching, prefer `tools.use("entityOps", "addComponents", targets, components)` over a loop of `entity(id).component.add` — it takes many targets and many components in one call. ## Common pitfalls - **Naming.** The component identity is the folder stem with `.component` stripped (e.g. `<Spinner>.component/` → identity `Spinner`). Don't repeat the suffix in the identity passed to `component.add`. - **`init.lua` vs `init.luau`.** Either is accepted (it's a `one_of_group: "entrypoint"`), but `.luau` is canonical. Mixing both in one folder is invalid. - **`update` in edit mode.** It runs whenever the gameplay clock is running, and entering edit stops that clock — so `update` is idle in a freshly-entered edit session and ticks again the moment anything sets `engine.paused = false`. Use `tools.use("wld", "play")` to test update logic under the mode it ships in; `tools.use("wld", "edit")` to return. See **Per-frame hooks and the two axes** above. - **Renaming.** Renaming the folder changes the identity. References to the component are recorded against the component itself, so renaming or moving it does not break them. ## Related types - `.module` — pure-function library, no per-entity state. - `.service`: a declarative content generator, no per-entity state. - `.preset` — a captured component configuration, replayable into `component.add` without re-typing fields. - `.bundle` — entity hierarchies that may carry component attachments as part of the bundle. ## In the Inspector Fields: its execution order, hooks, and how many methods and events it declares, then the fields its `public` table declares as read-only typed controls holding their defaults, with **Check** and **Open** for its entry file. Instances: a link to every entity carrying it. What its card shows on an entity comes from the component's own `inspector.luau`.

# slots The rules of the slot family, shared by the `Slot`, `Assembly` and `Part` components: which entities are slots and the path each answers to, which part fills a slot under a configuration, whether a part fits a slot and why not, and building or removing the part that fills a slot. Content reaches it through the three components; tools that need the rules without a component require it. ## API | Call | Returns | |---|---| | `Slots.holderOf(entityId)` | The `Assembly` holding the slots at the entity: the nearest one on it or above it, climbing past each one that stands on a part built into a slot. Nil when none does. | | `Slots.holdsOwnSlots(e)` | Whether an entity carries an `Assembly` that holds its own slots (one on an entity that is no part built into a slot). | | `Slots.pathOf(slot)` | A `Slot` component's path. | | `Slots.nameOf(slot)` | A `Slot` component's name. | | `Slots.discover(rootId)` | Every slot at and under an entity, `Slot` components and `Humanoid` role sockets, each `{ path, name, kind, tags, default, joint, entity, slot?, humanoid?, from }`. A descendant whose own `Assembly` holds its slots is left out, with its subtree. | | `Slots.partRef(part)` | The AssetRef an AssetRef, identity, guid or path names, or nil and why. | | `Slots.declaredFits(ref)` | The slot kinds a part fits and where that is declared (`Part`, `.metadata`). | | `Slots.fits(entry, part)` | `(fits, why, ref)`. | | `Slots.decide(config, entry)` | The guid filling a slot under a configuration, and its source. | | `Slots.currentFill(entry)` | The entity filling a slot and its `{ path, part }` record. | | `Slots.apply(entry, guid)` | Make a slot hold a part, rebuilding it only when it differs. | ```luau local Slots = require("@builtin::modules.slots") for _, s in ipairs(Slots.discover(car.id)) do print(s.path, s.kind) end ``` A fill entity carries the `slotFill` attribute: the path of the slot it fills and the guid of the part.

# Error Text A 3D "ERROR" text model used as the visible fallback when an asset fails to load — spawned in place of missing geometry so a broken reference is obvious in-scene instead of silently invisible. Decomposed from `ERRORText.fbx` into this bundle (mesh + material + texture + entity template). ## Composition - Root `error_text` → `Sketchfab_model` → the `ERRORText.fbx` node hierarchy. - Carries the extruded "ERROR" letter mesh, its material, and texture as private subassets. ## Usage Spawned automatically by the engine as the placeholder for an unresolved asset; can also be spawned directly to test the fallback path.

# lamp_post (bundle) A lamp post: a slim post, a lit head sitting on top of it, and the point light it casts. Four entities under one root — `post`, `head` and `glow` — built from builtin meshes and materials, so the bundle carries no geometry of its own. Its foot sits at `y = 0` and it stands 2.53 units tall, so placing it at a position on the ground puts it on the ground. ```lua asset.resolve("@builtin::bundles.lamp_post", "bundle"):instantiate(nil, { position = { 4, 0, 2 }, rotation = { 0, 30, 0 }, scale = 1.2, }) ``` ## What it is for It is the prop a starting scene places to show what placing an asset does: one call brings a whole hierarchy in as the scene's own entities, and the `Light` riding along shows that a bundle carries behaviour and not only shape. Reach for it whenever a scene needs a light source that reads as an object rather than as a floating value.

# assetType (asset type) An asset type says what a kind of asset is: the files an asset of the kind is made of, the code that gives it behaviour, the interface a person uses to work with it, and how it is found, pictured and checked. A `<typename>.assetType/` folder declares a type called `<typename>`, and every `<name>.<typename>/` folder is an asset of it. `assetType` is itself a type, so a type is an asset like any other: it is created, versioned, installed and contributed the same way. ## Making a type `asset.create("assetType", "<typename>")` scaffolds a type. The type registers the moment its folder is written, anywhere under `/zero/source/`, and from then on `<name>.<typename>/` folders are its assets. An asset of a type that is not registered yet is not an asset, so make the type first. A type folder is a root: `~.x` in any file inside it names the type's own `x`, wherever the type is installed. Keep the type's whole implementation inside its folder and reach it that way. What a type folder must hold is set by this type's own `type.yaml`, the same way every type's `type.yaml` sets what its assets hold. `asset.validate` on a type reports anything missing, and the scaffold produces a folder that passes. ## What sets your type's schema (`type.yaml`) `type.yaml` is the structural contract every asset of the type is checked against. The keys below are the ones the engine reads; a key not listed here is ignored. | Key | What it controls | |---|---| | `suffix` | The folder suffix of the type's assets. Defaults to `.<typename>`. | | `primary` | The file or files that are the asset's content: what the asset resolves to when it is used. | | `entry_files`, `primary_aliases` | Further files that load as the asset or share its identity. | | `is_container` | Whether the suffix stays in the identities of what the asset holds. | | `is_opaque_walker` | Whether a walk of the tree stops at the asset and registers only its primary. | | `plural_dir`, `classify_exts` | Loose files in a folder of this name, or with these extensions, are assets of the type. | | `is_text_default` | Whether the asset's files are text unless stated otherwise. | | `broadcasts_subassets` | Whether assets nested inside an asset of the type are found by their own short name. | | `root` | `true` makes every asset of the type a root, so `~.x` inside one names that asset's own `x`. | | `contract_ref: { field, category }` | A key of the primary file that names another asset the asset is built on. | | `files: { required, optional }` | The files an asset holds (below). | | `allow_unlisted` | `false` reports every file the type does not declare. | | `aliases_from: [{ file, key }]` | Further names an asset answers to, read from its own files. | | `settings:` | Typed per-asset settings (below). | | `inspector:` | The interface people use for the type and its assets (below). | | `preview:` | How an asset is pictured (below). | | `references:` | Names of other assets the type's files carry (below). | | `indexing:` | What search reads for each asset (below). | | `describe:` | How a missing description is generated (below). | ### The files an asset holds Each entry under `files.required` or `files.optional` is `{ path, kind: file | folder, one_of_group?, content? }`. `*` in a path matches within one segment. Entries that share a `one_of_group` are satisfied by any one of them. `content` lists checks on the file's bytes: | Check | Passes when | |---|---| | `non_empty` | the file has content | | `json_field { key, type?, non_empty?, accept? }` | the JSON holds the key (a dotted path) with that shape | | `yaml_field { key, type?, non_empty?, accept? }` | the same for YAML | | `described { keys?, headings?, message? }` | the file says what the asset is (see "Ask your assets to say what they are") | Each check takes a `message`, which is what the author is told when it fails. ### Settings `settings: { values, schema: { type | instance, export? } }` gives every asset typed settings. `values` names the file an asset's values live in; `schema.type` declares one schema for the whole type, and `schema.instance` names a file each asset declares its own in. `asset.create` writes the resolved values, and a write to the values file reaches `onChange` with what changed. ## The human side (`inspector.luau`) A type is used by people through its Inspector, and without one the type is usable only from code. The Inspector is the type's interface for a person: for a procedural graph it is the graph editor, for a kit it is the tracking view of what the kit holds and what is still missing. Writing it is part of writing the type. `inspector: { type, instance? }` in `type.yaml` names the files. `type` is the interface for the type itself and for its assets; `instance` names a file an asset may ship to add its own. Each returns: ```luau return { sections = { { id = "graph", title = "Graph", build = function(ctx) ... end } }, replace = { contents = { ... } }, -- replace a default section by id order = { "graph", "contents" }, -- section order } ``` `build(ctx)` receives the asset and builds the section. A section's `title`, and the text its rows carry, is a string or an `i18n.text` value read from a catalog (`i18n.text("inspectors.mesh.title")`), which follows the editor's language. `asset.create("assetType", ...)` scaffolds a working `inspector.luau` to start from. `asset.validate` on a type that names no inspector, or names one that does not load, reports it. ## Say what your type is for (`about.yaml`) Every type carries an `about.yaml` that says what the type is for, in three plain-language texts: ```yaml intent: "Sets the typeface of the text in your game: UI, labels, signs and 3D lettering." function: "A font, from a TTF, OTF or WOFF file, made available to all of Zero's text, including 3D text." usage: "You choose it by name for your UI or your text, and the text appears in that typeface." ``` - **`intent`** is what the type is for in someone's game, in the words a game maker uses. Up to 800 bytes. - **`function`** is how it works today: what an asset of it is made of and what the engine does with it. Up to 1500 bytes. - **`usage`** is what a person or an agent does with one. Up to 1200 bytes. Write about the type as a whole, not one asset of it, and say what it does now. Agents read these texts to learn when to reach for the type and how; people searching find the type by them. The scaffold starts each text with `[[describe]]` and a note on what to write; a text that still starts that way counts as not written. `services describe` can write them. They show up in `asset.inspect` as `detail.about`, in `assetTypeRef:getAbout()`, at the end of the type's `types/<typename>` guide, and at the top of the type's Inspector. ## Ask your assets to say what they are A type can require each asset to carry a description: a file, written by the author or generated, saying what the asset is and what it is for. Declare it with a `described` check: ```yaml files: required: - path: "README.md" kind: "file" content: - { check: "described", message: "Say what this widget is for and where it goes." } ``` A file that is missing, empty or still has a line starting with `[[describe]]` fails the check, and so does a YAML file whose named `keys` are missing or over their `max_bytes`, or a Markdown file missing a named heading. `asset.validate` names the asset, and a push that carries it is refused with `message`. `services describe` finds such assets and writes their descriptions. `describe:` steers what is generated: ```yaml describe: guidance: "Say what the widget shows, what input it reacts to, and where it fits in a UI." examples: - "<identity of an asset of this type whose description reads well>" ``` An example is an asset of your type whose description is a true, written one, never a placeholder and never the asset being described; with none, leave `examples` empty. A type whose assets the model cannot perceive (a sound, a motion) says so in `guidance`, and the description is drawn only from what the asset's own files state. Start the file unwritten in your `template/`: a heading and one line starting with `[[describe]]`, never example content, which every new asset would carry verbatim. A type whose assets say what they are through their own content (a mesh, a texture) declares no check. ## The type's code (`behavior.luau`) `behavior.luau` returns one table. These are the keys the engine reads from it; anything else on the table is the type's own. ### What the type's assets can do | Key | Shape | What the engine does with it | |---|---|---| | `ref` | `{ [name] = function(self, ...) }` | Every function becomes a method on every asset of the type: `ref:name(...)`. | | `modules` | `{ [name] = require(".x") }` | Code the type's assets reach with `asset.containing(__FILE__).modules.<name>`. | | `events` | an events schema | Events an asset fires. Readers subscribe through `ref.events.<name>:connect(...)`; the type fires them. | | `refShapes` | `{ [method] = function(self) -> (typeExpr, source?) }` | The result type of a `ref` method for one particular asset (below). | | `namePattern` | a Lua pattern | The names `asset.create` accepts for the type's assets. Default `^[A-Za-z][A-Za-z0-9_]*$`. | | `derive` | `{ output, module, compute, fingerprint, matches?, required?, timeout? }` | A file computed from the asset when it is committed; a `required` one holds the commit until it lands. | Some `ref` names mean the same for every type, and the engine calls them: - **`instantiate(self, target?, opts?) -> (root, idMap)`**: puts the asset in a scene. Defining it is what makes the type scene-instantiable. Its return is a contract (below). - **`inspect(self) -> detail`**: what `asset.inspect` reports for the asset beyond the common record (below). - **`preview(self, opts)`**: renders the asset's picture; it wins over the type's `preview:` recipe. - **`previewMaterial(self) -> { material }`**: the material a `surface` preview paints. - **`saveDefinition(self)`**: writes the asset's in-memory edits back to its files in edit mode. Some names are answered for every asset before the type is asked, so a `ref` entry of the same name is never reached: `getSource`, `getBytes`, `getText`, `exists`, `deps`, `canInstantiate`, `canPreview`, `preview` (which calls yours when you define one), `meta`, `runtime`, `events`, `typeRef`, `modules`, and the residency flags `has_backing_asset`, `has_runtime_changes`, `cpu_resident`, `gpu_resident`. ### When the engine calls the type | Hook | Signature | When it runs | |---|---|---| | `onCreate` | `(name, opts) -> { [path] = contents }` | On `asset.create`. Returns the files of the new asset, laid over the type's `template/`. Annotate `opts`: its type is the schema `asset.create` checks the caller's arguments against. A `""` key writes a single loose file. | | `onReplace` | `(dest, files) -> files` | On an `asset.create` over an asset already at `dest`, after `onCreate`, so what the author added can be carried into the replacement. | | `onRegister` | `(self)` | Once per asset, when it first registers: when the world loads, on a live `asset.create`, and when an asset arrives later (installed, pulled, synced). This is what makes an asset take effect the moment it is written. | | `onChange` | `(ref, change)` | On every write to a file inside an asset of the type. `change` is `{ path, asset, type, kind, origin }`, plus `settings` and `settingsChanged` for a write to the settings values file; `kind` is `edited` or `seeded`, `origin` is `local` or `remote`. Filter on `change.path`. Writes to one asset arrive in order, each after the hook for the one before has finished, and the hook may wait on what it reads. A write the hook makes inside its own asset arrives later like any other, so keep the hook convergent. | | `onDependencyChange` | `(ref, change)` | When a module the asset's code requires is re-run, or a name the asset carries starts resolving. `change.kind` is `dependency`. | | `onDelete` | `(ref)` | When an asset of the type leaves the world: deleted, or the world it is in is swapped away. | | `validate` | `(ref) -> { { code, message, severity?, path? } }` | On `asset.validate`, after the `type.yaml` checks, for the type's own rules. `severity` defaults to `error`. Runs on every push, so a type's rules hold at publish. A hook that fails reports `validate.hook_failed`. | ### Settings hooks | Hook | When it runs | |---|---| | `settingsDefaults(name, opts, asked) -> table` | Once per `asset.create`, for values the schema's defaults do not give. | | `settingsCorrections(values, name, opts) -> (corrections?, reasons?)` | On every settings write. A correction to a field the writer named refuses the write, giving the reason. | | `settingsDerivedDefaults(values, explicit, changed)` | On a settings write, for fields derived from others. | | `normalizeSettings(values, stored?)` | On every read and write, to map an earlier spelling of a field to the current one. | | `settingsHealed(values, stored)` | On a read, to repair stored values. | | `settingsSchemaProblem(schema, ref) -> string?` | When an asset's own schema is read; a returned string refuses the schema. | `creationInputs` (`{ [opt] = true | selectorOpt }`) names `asset.create` options that are inputs to the type rather than settings. ### Reloading An edit to `behavior.luau` reaches existing assets with no restart. ## How an asset is pictured (`preview:`) | `kind` | The picture is | The type provides | |---|---|---| | `instantiate` | the asset placed in the preview studio through its `instantiate` | `ref.instantiate` | | `image` | a file the asset holds, fitted to the frame | `source: { files }`, the candidate files in order | | `surface` | the asset painted on a mesh | `mesh`, and `ref.previewMaterial` | | `custom` | whatever `ref.preview` returns | `ref.preview` | ```yaml preview: kind: surface mesh: sphere ``` `angle: [yaw, pitch]` turns the camera. The studio owns the light, the backdrop and the framing, so an asset pictures the same in every world. A type with no `preview:` that defines `instantiate` still answers `ref:preview()`. A picture is rendered when something asks to view it (the editor showing the asset, `ref:preview()`), when previews are generated on request (`assets.generatePreviews`), and when the asset is staged. An edit alone renders nothing. The picture records what it was made from, so a stale one is told from a current one. ## The names your type's assets hold (`references:`) Where your type's own format or API carries the name of another asset, declare it here: ```yaml references: keys: # a top-level key of the type's files that holds a name, or a table of them - { key: "shader", type: "shader" } args: # an argument of a call, counting from 1 - { call: "g:node", position: 2, type: "procNode" } fields: # a field of the options table a call takes - { call: "fx.beam", field: "material", type: "material" } ``` `type` is the category the name resolves in. `asset.declareReferenceKey`, `asset.declareReferenceArg` and `asset.declareReferenceField` declare the same from a script. ## What search reads (`indexing:`) `indexing:` is how assets are found. Search reaches an asset only through what its type's `indexing:` names, and adds nothing of its own. That includes you: an asset indexed badly is one you cannot find later, when you are making something else and need it. A type whose assets are never looked for says `indexing: none`. ```yaml indexing: data: # text, read from the asset's files - role: identity extractor: verbatim source: { file: "README.md" } - role: interface extractor: symbols source: { files: ["init.luau"] } - role: implementation extractor: verbatim source: { files: ["init.luau"] } content: # the picture - role: identity modality: image source: { file: "preview.png" } facets: # what a query filters and re-ranks by file: ".metadata" rigged: { type: bool, from: { components: { contains: SkinnedModel } } } roughness: { type: number, filter: range, from: { file: "mat.yaml", field: "floats.roughness" } } ``` **Roles.** Each `data` and `content` entry has a `role`, and a query matches in two slots: - **`identity`**: what an asset is. For anything you look at, the picture; for anything else, the text that says what it is. - **`capability`**: what it does and how it is made. `interface` (the signatures or shape a caller uses) and `implementation` (the body) both count as capability, and a type with code usually declares both. Ask what a person would recognise an asset of the type by, and what it does, and point each role at the file that says it. For text, that is the asset's description: the file your template starts with a `[[describe]]` block, which the author writes or `services describe` fills in (see "Ask your assets to say what they are"). **`data`.** `extractor: verbatim` embeds a file's text as it is; `symbols` embeds the declared signatures of code. `source` is `{ file }` or `{ files: [...] }`. Never index a file name (`source: { field: name }`): one or two words carry nothing to match. **`content`.** `modality: image` embeds the picture itself, so a text query matches what the asset looks like. A type whose assets are looked at makes the picture its identity. **`facets`.** What a query narrows and re-ranks the matches by. `file` is embedded whole, so keys nobody declared in it are still found. Each further key is computed for every asset and states a value for every one, including `false`: a file can imply "not rigged" but never say it, and a query separates rigged from unrigged only because the unrigged ones say `rigged: false`. A key is `{ type: bool | number | enum, filter?: range, from }`, where `from` is `{ file, field }` (a field of one of the asset's files, dotted for nesting), `{ metadata: key }`, or `{ components: { contains | any_outside } }` (what the asset's entities carry). ## What blocks a push A push checks every asset it carries against its type. These refuse it: - a required file that is missing, a `content` check that fails, a `described` file not written yet; - an error from the type's `validate`. Unlisted files and warnings do not. A `described` file blocks only a push that changes the asset. When a push is refused, the message names each asset and what it lacks. `world.publishBlockers()` and `zm status` read the same list without pushing. ## Typing a result from the asset (`refShapes`) A `ref` method whose result depends on the asset (one entry per child folder, per row of a config, per control a map declares) can only be annotated as `{ [string]: Thing }`, which accepts any key. `refShapes` states the result for each asset instead: a function returning a Luau type expression for that asset, and the module whose types the expression uses. Read the asset; never run it. ```lua -- inputMap.assetType/behavior.luau M.refShapes = { activate = function(self): (string, string) local names = {} for _, control in ipairs(M.ref.controls(self)) do table.insert(names, control.name .. ": Handle") end if #names == 0 then return "", "" end return "{ " .. table.concat(names, ", ") .. " }", "@builtin::modules.zinput.scheme" end, } ``` With it, `map.jump:onPressed(fn)` is checked and `map.noexisting` is reported. A per-asset type applies where the call site names which asset: a component field whose default names it, or an annotation `AssetRef<"inputMap", "<identity>">`. `asset.resolve(name, category)` carries only the category, and a name computed at runtime carries nothing, so calls on those keep the declared return. The type belongs to the call's result: index it there, or bind what you need from it there, and the names stay checked. `require("@builtin::assetTypes.assetType.shared.refShapes").published()` shows what was published: `categories` (each type's method surface) and `returns` (per-asset results by identity, then method). An identity missing from `returns` was never published. Results are recomputed when an asset is written; at most 64 assets of one type are read. ## Putting an asset in a scene (`ref.instantiate`) A caller writes one piece of code against every instantiable type, so what `instantiate` returns is fixed: ```lua local Instantiable = require("@builtin::assetTypes.assetType.shared.instantiable") M.ref = { instantiate = function(self, target, opts) local root = Instantiable.root(self, target, opts) -- compose the asset under `root`, now return Instantiable.result(self, root, idMap) end, } ``` **In.** `target` is the entity the asset lands under, or onto for a hierarchy type; with none, the type spawns a new root. `position`, `rotation` (three numbers in degrees, or a quaternion), `scale`, `name` and `temporary` mean the same for every type: `Instantiable.root` applies them to a root you make, `Instantiable.place` to one you adopt. Document any options of your own in the hook's `--!arg` docs. **Out.** `(root, idMap)`. `root` is the composed root, live when you return: build synchronously, never defer to a component's `awake`. `idMap` maps each original id to the spawned one, so a component that composes the asset again on every load can pass it back in and keep references into the composition. Every call goes through `Instantiable.result`, which refuses a root that is not live and turns a missing `idMap` into `{}`. ## Inspecting an asset (`ref.inspect`) `asset.inspect(ref)` builds a record every asset shares (`identity`, `name`, `guid`, `source`, `typeName`, `typeDefinitionPath`, `scope`, `origin`, `description`, `tags`), then calls `ref.inspect(self)` for the type's own `detail`: ```lua M.ref = { inspect = function(self) -- read the asset's own files, never runtime state: inspect works on an asset -- that has not been compiled, uploaded or registered return { --[[ what makes this asset what it is ]] } end, } ``` Without it, the record is the shared part alone, and an agent inspecting the asset learns nothing of what it is. A hook that raises leaves `detail` empty and sets `record.warning`. ## Discovery - `asset.list("assetType")`: every registered type. - `asset.inspect("<typename>")`: the type, its README and its `about.yaml` texts. - `asset.resolve("<typename>", "assetType")`: the type itself.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Bundle (asset type) A bundle is a composable, spawnable entity assembly— a saved entity hierarchy plus its components, sub-assets (meshes, textures, animations, materials, sub-bundles), and any nested data, packaged into a single addressable identity. Bundles are the engine's "prefab" primitive. There are **two ways** to bring a bundle into a scene — and the difference matters enormously for scene saving and live editing. See "How to spawn" below before you write anything. If you want one snapshot of a whole world / level, use a `.scene`. ## Where it lives - Source: `/zero/source/.../<Name>.bundle/` - Identity: `<Name>` (the `.bundle` suffix strips for use in identities, but the on-disk folder keeps the suffix). - Folder shape (container type — open child set): - `entity_template` — JSON of the entity hierarchy + components. **Required.** - `.metadata`: optional. - Anything else: meshes / textures / materials / animations / sub-bundles. Validator allows arbitrary additional files (`allow_unlisted: true`). ## How to create one Two paths, depending on whether you have an in-scene hierarchy or are authoring from scratch: ```luau -- From an existing in-scene entity: composes the given entity tree into a bundle. local bundle = asset.create("bundle", "<Name>", { entity = entityRef }) -- Or scaffold an empty bundle, then update it from an entity: local bundleRef = asset.create("bundle", "<Name>") bundleRef:update(entityId) ``` ## How to spawn ### 1. `Asset` component — live-linked (the canonical way) **This is the primary way to put a bundle into a scene that survives saving as an asset reference.** Spawn an empty entity, attach the `Asset` component, point it at the bundle: ```luau local car = entity.spawn("car_1") car.component.add("Asset", { source = "<bundleIdentity>" }) ``` What you get: - The bundle's hierarchy spawns as **temporary** children under the owning entity. They're real, addressable runtime entities, but they are NOT serialized into `scene.json` on save, only the Asset component and its entity is saved. - **Live editing of the bundle is supported.** When you edit anything inside the `.bundle/` (entity_template, meshes, materials, sub-bundles, components), every entity in the world carrying that `Asset` component automatically tears down its spawned children and rebuilds them from the new template — same frame, no restart, no manual reload. The `onAssetReload` hook in `Asset.component/init.luau` drives this. - **Per-instance overrides survive across reloads.** Move a spawned child, rename it, add/remove components on it, edit a component's public state — the changes land in the Asset's `public.diff` (a sparse delta keyed by the child's `original_id`) at save time and are replayed by `bundleRef:instantiate()` on next load. The bundle stays a single source of truth; per-spot tweaks ride on top. - **Stable child ids across reloads.** `public.idMap` records the `original_id → runtimeId` assignment on first spawn; on every subsequent spawn the same mapping is reused so cross-entity references (e.g. `SkinnedModel.skeletonRoot = "ent_xxx"`) stay valid. ### 2. `bundleRef:instantiate` — baked, no live link Resolve the bundle and instantiate it onto an entity — this spawns the children **without** the live-link plumbing the `Asset` component provides: ```luau local car = entity.spawn("car_1") asset.resolve("<Name>", "bundle"):instantiate(car) ``` What you get — and the trade-offs: - The children spawn as **regular** (non-temporary) entities. On the next `layers.active:save()`, the entire spawned hierarchy is serialized into `scene.json` verbatim. - **No live link to the bundle.** Editing the `.bundle/` after the fact has no effect on already-spawned hierarchies. The bundle was effectively consumed at spawn time. - Scene-save / restore round-trip works the same as for any other hand-authored entity tree. Use this path when you want a one-shot expansion of the bundle into permanent scene state (e.g. you're populating a scene's static layout from a parametric bundle and don't want a live link). You can convert a live-linked instance into a baked one explicitly via `Asset:bakeIntoScene()` — this drops the `Asset` component and promotes the temporary children to permanent scene entities. ## How it operates 1. **Registration.** Writing into a `.bundle/` folder indexes the asset with the container-category restore plumbing. 2. **Inner refs.** Component fields that reference assets inside the bundle use the `__ref` shape (`{ "__ref": "<guid>", "name": "...", "type": "..." }`). The asset registry resolves them at spawn time. 3. **Identity.** The `.bundle` suffix is stripped, so a bundle resolves as `<Name>` (`asset.resolve("<Name>", "bundle")`); the type argument tells it apart from any `<Name>` of another type. 4. **Hot reload.** Saving `entity_template` (or any file in the bundle directory) fires the engine's per-asset content-changed hook, which calls `onAssetReload("source")` on every entity whose `Asset` component points at the bundle. Each carrier despawns its children and re-instantiates against the new template — typically next frame. ## Discovery - `asset.list("bundle")` — every registered bundle. - `asset.inspect("<name>")` — sub-asset catalog, source, this type README. - `ls /zero/source/<Name>.bundle` lists the files the folder holds. ## Parts and slots A bundle can be an object assembled from parts, and a part that fills one. A child carrying a `Slot` component is a named place another part fills (its `kind`, the `tags` a part must carry, a `default` part, and where the part attaches: that child's transform). A bundle whose root carries a `Part` component is a part, and its `fits` names the slot kinds it fits. An `Assembly` on the root holds what fills each slot by path (`wheel_fl`, `engine/turbo`, a part's own slots nesting under the slot it fills), and resolves, swaps and explains them at runtime: ```luau local car = entity.spawn("car") car.component.add("Asset", { source = "Buggy" }) -- a bundle with slots and an Assembly at its root local asm = car.component.get("Assembly") asm:configure({ wheel_fl = "SportWheel", engine = { part = "V8", turbo = "Turbo" } }) asm:fill("wheel_fl", "OffroadWheel") -- rebuilds that wheel alone print(asm:fits("wheel_fl", "V8")) -- false, and why ``` The configuration is saved with the scene and synced; the parts are runtime children rebuilt from it. `guides { path: "topics/assemblies" }` covers the whole family. ## Authoring conventions - Prefer `bundle:update()` or `asset.create("bundle", "<name>", { entity = ref })` over hand-authoring `entity_template`. The in-scene composer wires `__ref` shapes correctly and pulls in every transitively-needed asset. - Keep bundles focused — one prefab per bundle. If you have a "vehicle + driver + sound" assembly, split into three bundles and reference them from a scene rather than packing all three into one bundle. - Name child entities meaningfully — bundle interiors are inspectable, and stable IDs let other tooling (`entity_template` edits, animation hooks) find them. - Sub-bundles compose: a bundle's `entity_template` can `__ref` a child `.bundle/`. The asset registry resolves them transitively. ## Common pitfalls - **Confusing the two spawn paths.** `Asset` component = live link, reference-only scene save. `bundleRef:instantiate()` directly = baked, full hierarchy in `scene.json`. - **Copying JSON between bundles.** A copied `entity_template` does not bring the assets it references along with it; re-compose from a live scene rather than copy-pasting JSON. - **Live editing only fires for live-linked carriers.** Already-baked entities don't update when you edit the source bundle. ## Related types - `Asset.component` — the canonical mount point for a live-linked bundle. See its README for the `idMap` / `diff` machinery in detail. - `.scene` — owns a whole world's worth of entities; spawns bundles into itself via `Asset` components on per-spot entities. ## In the Inspector Selecting a bundle opens its **Contents** section, from the bundle's inspect detail: the template's node count, its root, the component types attached across it, a table of each renderable node's mesh and material, and a link to each of those meshes and materials.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Module (asset type) A module is a reusable, stateless (or globally-stateful) Luau library that other code pulls in with `require()`. Modules are the unit of factored-out logic in a world: helpers, math libraries, format parsers, registries, shared algorithms. ## When to use one - You have logic you want to share across multiple components, services, scenes, or tools. - You have a registry, lookup table, or shared cache that callers all read from / write to. - You want a stable API surface (`M.fn`) other code can depend on. If the logic is bound to one entity, use a `.component`. If you want a named UI of fields rather than functions, use a `.preset`. ## Where it lives - Source: `/zero/source/.../<name>.module/` - Identity: the source path with `/` written as `.` and each segment's type suffix dropped — `/zero/source/demo/beats.module` is `demo.beats`, and `/zero/source/kit.package/beats.module` is `kit.beats`, the container's name kept and its `.package` suffix gone. `asset.create` returns this string, `asset.resolve(...).identity` reads it back, and the `require` forms below write it as `<identity>`. - Folder shape: - `init.luau` (or `init.lua`) — module body. **Required.** Returns a table (conventionally named `M`). - `README.md` — instance-level documentation. **Required.** - `.metadata` — agent-editable tags + free-form fields. **Required.** ## How to create one ```luau asset.create("module", "<name>") -- Creates: /zero/source/<name>.module/ -- init.luau (canonical `local M = {} … return M`) -- README.md (instance README template) -- `folder` places it in a subfolder of /source, and that subfolder -- leads the identity: `{ folder = "lib" }` produces `lib.<name>`. -- `into` authors it inside a resolved container (a package, a toolbox), -- whose own identity leads the same way: asset.create("module", "<name>", { folder = "lib" }) asset.create("module", "<name>", { into = asset.resolve("myPkg.package") }) ``` ## How it operates 1. **Registration.** Writing `init.luau` into a `.module/` folder indexes the asset and registers the module path with the resolver. 2. **Loading.** The first `require("<identity>")` runs the file's body and caches the returned table. Subsequent requires from anywhere return the **same table** — this is the shared-state lever for "module-local" registries. The body runs in an environment of the module's own: a name it declares without `local` is readable by the module's own functions and by no other script, so an export reaches its callers through the returned table and nothing else. Requiring a component's folder runs its chunk the same way, once, and its `update`, `start` and `public` stay in that environment; a component runs on an entity through `entity(id).component.add(name)`. 3. **Hot reload.** Editing the file re-runs the module body and folds what it returns into the table already loaded, so that table keeps its identity: a caller that captured it with `require` reads the new source's functions and values through the reference it already holds, and a later `require` returns that same table. A key the new source drops goes away; a key something set at runtime stays. The body's own `local`s start again from their initial values, so state that must outlive an edit lives in `modules.state()` (`guides { path: "core/scripting-and-tasks" }`). 4. **Identity resolution.** A module is reached by its `<identity>`, and where the caller lives decides which spelling of it resolves. For a module in a **world**, from a caller in that same world — another module, a component, a scene entrypoint, or an `execute` chunk: - `require("<identity>")` — the identity on its own, resolved against the caller's own root. It carries every folder segment, so a module created with `{ folder = "demo" }` is `require("demo.beats")`. - `require("@root::<identity>")` — the same root-relative resolution, written out. - `require(".sibling")` — a module in the same folder, by its bare name; `..name` steps up one folder, `...name` two. Logs, stack traces and hot-reload notices name that same module `@local.source.<identity>` — its key under the world source root. The `<identity>` tail of that key is the form above, so a trace reading `@local.source.demo.beats` is `require("demo.beats")`. For a module in a **library** — content under `/zero/source/libs/@<lib>/` — `@<lib>::` addresses that library's root from anywhere: `require("@builtin::modules.transform")`. Mounting a world as a library moves its files under such a root and flips the caller root to `@<lib>::`, which is what keeps the root-relative forms above resolving across the move. ## Discovery - `asset.list("module")` — every registered module. - `asset.inspect("<name>")` — public functions, source path, this type README. - `ls /zero/source/<name>.module` lists the files the folder holds. ## Authoring conventions - Return a single `M` table from `init.luau`. Top-level statements with side effects run on first require — useful for one-time initialization, dangerous if they touch the engine before it's ready. - Write exported functions as `typed function`, not `function`: the argument types are enforced at the call and the checker knows the signature, so a caller's mistake is reported where they made it. - Annotate exported functions with `--!desc` / `--!arg` / `--!return` / `--!example` so the LSP, `tools.list`, and `asset.inspect` surface them. A function with no `--!desc` is reachable only by someone already reading this file. - Declare a VALUE with `Field.<kind>(default, mode, description)`, and a table whose members are reached through a metatable with `--!members <TypeName>` — the latter gives the surface its accepted member set, its type, and its documentation from one table. See `guides { path: "core/authoring" }` for all four rules and `modules/api/engine/entity.module/members.module` for a worked member table. - Keep module state in module-local upvalues or in `modules.state()`. A name the body declares without `local` lives in the module's environment, which every run of the module shares: a function the previous run left in place reads what the reload assigned. Module-locals start again from their initial values with each hot reload; the table `modules.state()` returns is the same table on both sides of every reload. - Prefer focused modules over kitchen-sink modules. If two halves of a module have no shared state, split them. ## Common pitfalls - **Cyclic requires.** A `require` chain that loops will return the partial table (the half built before the cycle was detected). Design for one-way dependencies. - **Engine-time side effects.** Don't `entity.spawn` at module top-level — the engine may not be ready. Expose an `M.init` and call it from a scene entrypoint. - **Hot-reload + module-local cache.** A module that caches expensive computation in upvalues loses that cache on reload — fine for dev, but be aware in performance work. - **`init.lua` vs `init.luau`.** Either works, `.luau` is canonical. - **Writing one while play runs.** A `/source` write made while play is running lands on the play shadow, and a guarded play-exit discards it unless it is kept. One `.module` write shadows `init.luau`, the `README.md` and the `.metadata` together. `vfs.write(path, bytes, { durable = true })` skips the shadow, and `vfs.promotePlayShadow` keeps what is already on it — the `core/vfs` guide has the model and what each route costs. ## Related types - `.component` — for entity-bound state + lifecycle hooks. - `.service` — generates content you don't have yet (a mesh, sound, texture, …) via a metered provider. - `.tool` — for a single agent-callable function with a YAML schema. - `.package` — to group several modules + components + scenes into one shippable folder. ## In the Inspector Exports: what the module exports (name, kind, signature), parsed from its source without running it, with **Check** (the LSP's diagnostics for its entry file) and **Open**.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Mesh Mesh asset. `data.zmsh` is the engine-native geometry payload (`renderer.mesh.encode`); consumers reference the asset's guid.

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).

# Texture Managed texture asset. `data.ztex` is the encoded payload the renderer uploads; compression settings live in `settings.yaml` (`texRef:setSettings({ ... })` to change one).