# entityRef members One table describing every member of the entityRef — the value `entity(id)` returns. ```luau --!members entityRef entity/proxy local M: { [string]: Member } = { id = { kind = "property", type = "string", doc = "This entity's id string." }, despawn = { kind = "method", type = "(self) -> ()", doc = "Remove this entity from the scene." }, component = { kind = "namespace", type = "{ [string]: any }", doc = "Script components attached to this entity." }, } ``` ## Why one table Three things need to agree about what an entityRef has, and they used to be written separately: | Consumer | What it takes from here | |----------|------------------------| | `ref.module` | The accepted-member set — a member not named here is refused, and the refusal lists these names. | | The LSP | The `entityRef` type, generated from every entry's `type`. | | `man` / `lsp.describe` | Each member's description and rendered signature. | The `--!members entityRef` directive publishes the last two. Because all three read this table, a member cannot be documented but unimplemented, or accepted but undescribed. ## Declaring a member `kind` says what the member IS, which is what a reader needs and what decides how it renders: - `property` — read as a value. Renders `entityRef.id -> string`. - `method` — called. `type` is the whole signature, `self` first. Renders `entityRef.rename(self, newName: string) -> ()`. - `namespace` — carries its own members (`component`, `attribute`). `type` is a Luau type expression. A type that does not parse degrades to `any`, which answers every member access and quietly reverses the checking this exists for — so prefer a shape that is true over one that is precise. Several transform members are `{ [string]: any }` because the value really is a live proxy answering `.x`, `[1]`, and `set`/`get`/`add`. `doc` is one sentence, and `deprecated` names the path that supersedes it. `example` is the line a reader copies, published on the member's page under `Examples:`. A signature says what the call answers with; an example says what to write with the answer, which is what a member answering a shape (an array of identity strings, an array of records) needs beside its type. ## Where the members publish The directive's second token is the doc path the surface is reached at, and every member publishes there as well as under the subject's own name: | Directive | A member lands at | |-----------|-------------------| | `--!members entityRef entity/proxy` | `entityRef/<member>` and `entity/proxy/<member>` | | `--!members entityComponents entity/proxy/component` | `entityComponents/<member>` and `entity/proxy/component/<member>` | | `--!members entityHierarchy globals/entity/hierarchy` | `entityHierarchy/<member>` and `globals/entity/hierarchy/<member>` | The subject is a TYPE name, which is the spelling the checker and `lsp.methods` use. The root is the spelling a reader who knows the CALL writes. `entity(id).component.list()` reads at `entity/proxy/component/list`, which is the page `man component.list` answers with and the entry `/zero/docs/api/entity/` lists. A subject that declares no root publishes under its own name alone. ## Adding one Declare it here and implement it in `ref.module`. The member is then accepted at runtime, typed by the checker, and documented — from this one edit.

# ref Entity proxy metatable layer. Replaces the per-call closure-pushing entity proxy (`push_entity_proxy` in `crates/zero_scripting/src/ffi_callbacks.rs`) with a thin Luau metatable that calls into the `__native_transform.*` / `__native_entity.*` flat FFI bindings. The user-facing API is unchanged: `entity(id).localPosition = { x, y, z }`, `entity(id).despawn()`, `entity(id).name`, etc. all still work. After warm-up, steady-state allocation is **zero**: same `id` returns the same proxy (weak-valued cache), sub-proxies are lazily allocated once and cached on the proxy, and each method binding is a closure created on first access and cached as `__m_<name>`. ## Exports - `M.build(id: string) -> any` — entity proxy factory. Returns a cached proxy when one exists; otherwise allocates and caches a fresh one. Also bound as `_G.__build_entity_proxy` for the Rust-side `push_entity_proxy` call. - `M.EntityProxyMT`, `M.PositionProxyMT`, `M.RotationProxyMT`, `M.LocalPositionProxyMT`, `M.LocalRotationProxyMT`, `M.LocalScaleProxyMT`, `M.LossyScaleProxyMT`, `M.TransformProxyMT`, `M.AttributeProxyMT` — exported metatables; consumers that want to extend the proxies can read them, but the proxies are sealed externally (every `__newindex` errors). ## Usage ```luau local EntityProxy = require("@builtin::modules.api.engine.entity.ref") local proxy = EntityProxy.build("some-entity-id") proxy.localPosition = { 0, 1, 2 } proxy.localRotation.eulerAngles = { 0, 90, 0 } print(proxy.name) proxy.despawn() ``` ## Notes - **World vs local space** (post Bevy hierarchy migration): - `.position` / `.rotation` are world-space — engine back-computes `Transform.{translation, rotation}` on set, decomposes the world matrix on get. - `.localPosition` / `.localRotation` / `.localScale` are parent-relative direct reads/writes on `Transform.*`. - `.lossyScale` is read-only world-space scale (approximate under non-uniform parent scale + rotation; mirrors Unity). - `.worldMatrix()` answers the whole composed object-to-world matrix as 16 column-major numbers, translation in elements 13, 14, 15 — the placement the renderer draws the entity's geometry at, carrying the skew a decomposition into position / rotation / scale folds away. Also readable as `.transform.worldMatrix()`. - Bare `.scale` was removed — accessing it raises an error pointing callers at `localScale` / `lossyScale`. - **Sealed proxies**: every proxy errors on `__newindex` (sealing). Mutations go through `position.set` / `attribute.set` / etc., not direct field writes. - **Caching**: the entity-proxy cache is keyed by `id` with weak values (`__mode = "v"`), so dropped proxies are GC'd. Within one proxy, the `M_PREFIX`-keyed cache survives until the proxy itself is collected. - The `.component` sub-proxy is built by `__native_entity.component_subproxy` — Rust-side helper that constructs the ~15-closure component-proxy table once per entity. Subsequent `.component` accesses hit the cached entry.

# 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. 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()`. Globals leak across reloads. 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**.

# entity_coerce Coerce entity-shaped values into one uniform list. Installed by the prelude as `entity.ids` and `entity.proxies`, so nothing needs to require this module. An entity travels through the API as one of two values: - an **id string** — `"ent_5d305b4377f8d505"` - an **entity proxy** — the table carrying `.position`, `.component`, `.name` The engine calls answer with proxies — the lookups (`find`, `findAll`, `spawn`, `batchProxy`) and the hierarchy reads (`getChildren`, `getDescendants`, `getParent`) alike; `duplicate` answers with an id. Ids also arrive from stored data and serialized scenes. These two functions turn either shape — a lone value, a list, or a mix — into the shape the calling code wants. ## Surface ``` entity.ids(value) -> { string } -- id strings entity.proxies(value) -> { proxy } -- entity proxies ``` `value` is an entity, a list of entities, or `nil`. Both accept id strings and proxies in any combination. ## Examples Iterate a stored list of ids as proxies, so the per-entity surface is available without a per-element `entity(...)` call: ```lua for _, e in entity.proxies(savedIds) do e.position = { 0, 1, 0 } end ``` Take the id form of a proxy-answering call: ```lua local ids = entity.ids(entity.findAll("Prop")) entity.batchWrite(ids, "Transform", "translation", values) ``` Accept "one or many entities" as a single argument, with no branch: ```lua local function paint(targets, material) for _, e in entity.proxies(targets) do e.component.set("Model", { material = material }) end end paint(root, red) -- one proxy paint(root.id, red) -- one id paint(savedIds, red) -- a list of ids paint(root.getChildren(), red) -- a list of proxies ``` ## Behaviour - A single entity coerces to a one-element list. - `nil` coerces to an empty list — the hierarchy reads answer `nil` for an entity with no children, and an empty loop is the right reading of that. - Order is preserved and duplicates are kept. - A value that is not an entity raises, naming the element's position. A silently dropped element would come back as a shorter list with no indication of which one went missing. - `entity.proxies` raises on an id whose entity has despawned since the collection was read, since it has no proxy to answer with.

# defaults The Preset Manager: the world's ordered `[[presets]]` rows in `/zero/source/.world_settings`. A row names one declarer (`target`), one preset for that declarer (`preset`) and a path glob (`filter`). When something a declarer governs is created — an asset of an assetType, an import an importer runs, a component added to an entity — the first row naming that declarer whose filter matches the new thing's path gives a layer of its settings. Rows are read only at creation. A component row's filter reads the entity's hierarchy path (names from the root down, joined with `/`). What a scene build's capture scope adds takes the rows in any mode, whoever runs the build; outside a build, a component takes a row when it is added in edit mode. A component put back from existing content takes none: one added inside `materializing` (a saved scene, a peer's record, a template clone, a bundle's hierarchy, a build's records), and one a component's own code adds outside a build, on any coroutine that code runs. A scene build records which fields the rows gave each component, and a rebuild restates a component only when the code states it differently, so a row edit alone changes nothing a build already placed. Rows are written as guid envelopes and checked as a whole. A row is refused when its target does not resolve, is consulted at no creation, or declares no settings; when its preset does not resolve, is not a preset, or targets another declarer; or when its filter is not a string. A write replaces the `[[presets]]` block and keeps the rest of the file byte for byte. ## The row format ```toml [[presets]] target = { __ref = "8cc28fc8-ed63-48ee-83a6-15f4192e27e1", type = "importer", name = "texture" } preset = { __ref = "0b6c1f0e-5d0c-4d5e-9d64-3c1b7f2a9e11", type = "preset", name = "pixel_art" } filter = "sprites/**" ``` `target` and `preset` are guid envelopes: `__ref` is the guid, and `type` and `name` tell a person reading the file what it names. A row written by hand may name either by identity or guid; the next write rewrites it as envelopes. `.world_settings`'s `.refs` pins each row's target and preset by guid. ## Matching For a new thing a declarer governs, the rows are read in order and the first naming that declarer whose filter matches the thing's path applies; the rest are not consulted. A filter is a glob (`preset.glob`) over the path relative to `/source` with forward slashes, or an entity's hierarchy path for a component row; the empty filter matches everything, and a filter that is not a string matches nothing. A matching row whose preset does not resolve, or targets another declarer, is the match and contributes nothing, with one warning. A preset value the declarer's schema rejects is left out and the rest apply. ## Sync The rows are part of `.world_settings`, so they sync with the world like any other file and every peer reads the same rows. A row applies where the creation happens, when it happens: a peer's edit reaches only what is created after it arrives, and what was created before keeps the settings it was stamped with. A runtime asset lives for the engine process; a peer that started before a row edit keeps its old settings on a re-created runtime identity until it restarts. ## Exports - `Defaults.PATH`, `Defaults.BLOCK` — the file and the array-of-tables name. - `Defaults.SCHEMA` — the block's Field schema, `{ presets = Field.list(row) }`. - `Defaults.rows() -> { Row }` — every row, resolved, with its problems. - `Defaults.write(rows)` — normalise, check, and replace the rows. - `Defaults.normalize(input) -> StoredRow` - `Defaults.rowProblems(row) -> (problems, targetRef, presetRef)` - `Defaults.consultedAt(declarer) -> "asset.create" | "import" | "component.add" | nil` - `Defaults.relativePathOf(path) -> string?` — the path a filter reads. - `Defaults.match(declarerGuid, relPath) -> (Row?, index?)` - `Defaults.layerFor(declarerGuid, relPath) -> (values?, Match?)` - `Defaults.check(value, constraint) -> (ok, reason)` — the `presetDefaultRow` constraint. - `Defaults.removeAt(index)` — remove one row, writing every other row back as the file holds it. - `Defaults.importerSettings(importerRef, sourcePath) -> (settings, Match?)` - `Defaults.materializing(fn, ...) -> ...` — run `fn` with no row reaching a component add. - `Defaults.entityPath(id) -> string` — the hierarchy path a component row's filter reads. - `Defaults.forComponent(entityId, typeName, data?) -> data?` — the data a component add takes. - `Defaults.batchLayers(targets, typeName, data?) -> { { targets, data } }` — a batch add split into runs. - `Defaults.resolveValue(v) -> AssetRef?` — a row value as the asset it names. - `Defaults.recordingStamps(fn, ...) -> (stamps, ...)` — run `fn` and return what the rows gave the components a capture scope added meanwhile, per `stampKey`. - `Defaults.stampKey(entityId, componentGuid, instanceName?) -> string` The `preset` global exposes the rows as `preset.defaults`, `preset.setDefaults`, `preset.addDefault`, `preset.removeDefault` and `preset.defaultFor`.

# entity_hierarchy Hierarchy helpers built on top of the entity bounds API. Implements issue #876 (entity hierarchy swap) on top of issue #874 (entity bounds API). Pure Luau — uses `entity(id).hierarchyBounds()`, `entity.spawn`, and the transform primitives. Used to replace blockout geometry with a generated/imported asset, fitting the asset to the source's bounds and inheriting transform + (optionally) name. ## Exports - `M.swap(entityId: string, assetPath: string, opts: SwapOpts?) -> (string?, string?)` — replace `entityId` with `assetPath`. On success returns `(newEntityId, nil)`; on failure `(nil, errmsg)`. Types: - `SwapOpts = { fit?: string, source_origin?: string, asset_origin?: string, keep?: { string }, timeout?: number }` Options: - `fit` — `"bounds"` (default, uniform scale to fit inside the source's AABB), `"bounds_xy"` (uniform XZ, identity Y), `"none"` (no scaling). - `source_origin` / `asset_origin` — `"bottom"` (default), `"center"`, `"top"`. XZ always anchors on centre; only Y is picked. - `keep` — list of attributes to preserve onto the new entity. Currently only `"name"` is honoured. - `timeout` — seconds to wait for the asset's bounds to become queryable (default 5). ## Usage ```luau local EntityHierarchy = require("@builtin::modules.entity_hierarchy") local newId, err = EntityHierarchy.swap( "blockout_tree", "@builtin::meshes.cube", { fit = "bounds", source_origin = "center", asset_origin = "bottom", keep = { "name" }, } ) ``` ## Notes - The replacement is spawned far below the scene (Y = -1000000) before bounds become queryable, then moved to the final anchored position once the asset loader populates its bounds. Avoids a one-frame visual pop at the origin. - `awaitBounds` polls `entity(id).hierarchyBounds()` at 20 Hz via `await(delay(0.05))` — `task.wait(0)` cooperative yields don't always give the asset-load systems enough slack to make progress. - When the source has no geometry, `fit` is force-set to `"none"` (there's nothing to measure against) and the new entity is anchored on the source's `localPosition`. - The source entity is despawned at the end of `swap` — caller must not reference `entityId` afterward. - `keep` only supports `"name"` today; preserving component instances would require re-attaching every script-component and is out of scope.

# substrate_batch Unifies `entity.batchWrite` / `entity.batchRead` so they dispatch over the typed substrate FFI primitives (ids/binding × values/buffer) by argument shape. Pure Luau — a thin polymorphic wrapper around the substrate bridge. The prelude grafts this onto the engine's `entity` table at boot via `M.installInto(entity)`. After install, callers use the grafted methods on the `entity` global — they shouldn't `require` this module directly. ## Exports - `M.installInto(entity: EntityNamespace)` — graft the polymorphic `batchWrite` / `batchRead` onto the supplied namespace. Errors if any of the five required FFI primitives is missing. Types: - `EntityNamespace = { batchWrite, batchWriteBound, batchWriteFromBuffer, batchRead, batchReadToBuffer, [string]: any }` — the target namespace shape. The engine's `entity` global satisfies it once the FFI bindings are installed. ## Usage ```luau -- The prelude installs the wrappers at boot: require("@builtin::modules.substrate_batch").installInto(entity) -- After install: -- ids array + values table (per-call resolve): entity.batchWrite(ids, "Transform", "x", { 1, 2, 3 }) -- binding + values table (bound fast path): local b = world.bindEntities(ids) entity.batchWrite(b, "Transform", "x", { 1, 2, 3 }) -- binding + typed buffer (memcpy fast path): local buf = substrate.createBuffer({ type = "f32", len = #ids }) entity.batchWrite(b, "Transform", "x", buf) -- read side mirrors the same dispatch shape. local snapshot = entity.batchRead(ids, "Transform", "x") entity.batchRead(b, "Transform", "x", buf) ``` ## Notes - The five raw FFI primitives stay reachable under their original names AND under double-underscore aliases (`entity.__batchWriteIds`, `entity.__batchWriteBound`, etc.) for power users / debug code that wants to skip dispatch overhead. The aliases are registered Rust-side, not by this module. - Buffer-source writes and buffer-sink reads require a binding handle — passing a buffer against a raw ids array errors loudly with the migration hint. - The module owns no state. Reinstalling is idempotent: it just overwrites the two functions on the namespace.

# assetType (asset type) The `assetType` is the **type of types** — the meta-type that every `<typename>.assetType/` folder is an instance of, including itself. A `<typename>.assetType/` folder declares a new asset type called `<typename>`: its on-disk shape, its identity rule, and the structural contract instances of the type must satisfy. This type is self-hosting. `assetType.assetType/` conforms to its own schema — a `type.yaml` plus a `README.md` — so the type system is defined in terms of itself rather than a hidden engine special-case (the same way a C compiler is written in C). Every asset in the engine, including each `.assetType` definition, now resolves to a registered assetType: a `.material` resolves to `material.assetType`, and `material.assetType` resolves to `assetType.assetType`, which resolves to itself. ## Why it exists Assets used to be mapped to their type *implicitly*, by matching the folder suffix against a name-keyed registry. That match carried no stored link: nothing on a `Foo.material` recorded *which* `material.assetType` it was written against, so two worlds shipping a same-named type could silently disagree. Making `assetType` a real, resolvable asset closes that gap — the link from an asset to its type is now an explicit reference pinned in the asset's `.refs` sidecar (`via: "asset_type"`), exactly like every other dependency. ## Where it lives - Source: `/zero/source/.../<typename>.assetType/` - Identity: `<typename>` (the `.assetType` suffix strips from the identity; the folder retains the suffix on disk). - Folder shape: - `type.yaml` — the structural spec the validator reads. **Required.** - `README.md` — type-level documentation. **Required.** - `about.yaml` — three short plain-language texts saying what the type is for (see "Say what your type is for" below). Every built-in type ships one. - `behavior.luau` — optional behavior/scaffolding module. - `template/` — optional canonical placeholder body the templater copies into a new asset of the type. - `<name>.module/` — optional shared code the type ships to **every instance** of it, conventionally `shared.module/` (see below). ## Shared code its instances reach (`asset.containing` + `.modules`) A type ships code every instance of it uses by declaring the modules in its own `behavior.luau`, as a map of tracked `require`s: ```luau -- inside <typename>.assetType/behavior.luau M.modules = { shared = require(".shared") } -- the sibling shared.module/ ``` An instance reaches it with one location-independent line: ```luau -- inside any foo.<typename>/init.luau local api = asset.containing(__FILE__).modules.shared ``` `__FILE__` is the chunk's own VFS path; `asset.containing` resolves the calling asset, and `.modules.<name>` follows the instance's pinned `typeRef` (the type's **guid**, recorded in the instance's `.refs` as `via = "asset_type"`) to the module its type declares. Because resolution follows that link rather than a category name, the same line in an instance of a different type resolves to that type's module, and identically-named modules in two types never collide. `asset.typeRef(target)` reads that guid for any target; `asset.resolve(asset.typeRef(target))` gives the full `AssetRef<assetType>`. See `assetTypes/README.md` § "Shared code: type-owned modules" for the full mechanism. ## How to create one Authoring a new asset type is just creating a `<typename>.assetType/` folder under `/zero/source/`. The engine registers `<typename>` as a category **the moment the folder is written** — no engine restart, no Rust change, and it works for built-in (`@builtin/assetTypes/`) and user-defined types identically. Once `<typename>` is registered, `<name>.<typename>/` folders are recognised as assets of that type and resolve their `asset_type` link back to this definition. Creating a `<name>.<typename>/` folder *before* its `<typename>.assetType/` exists fails fast: the suffix has no registered type, so the folder can't be a valid asset. Author the type first. ## Say what your type is for (`about.yaml`) Every type carries a small `about.yaml` beside its `type.yaml`, and the README you write for the type documents how to author an asset of it. Both are required, and both are meant to be written as you make the type, while you know what it is for. `about.yaml` answers three questions in plain words, one key each: ```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. Name the whole range of things it covers, in the words a game maker would use for them. - **`function`** is how it works today: what an asset of the type is made of and what the engine does with it. - **`usage`** is what a person or an agent does with one: how they pick it, place it, call it, or hand it to something else. A few habits keep it useful. Write about the type as a whole, so the text holds for every asset of it, and leave out any one asset's name. Say what the type does right now. Stay with words a game maker would say, and mention a file name or a call only where a game maker would know it. The limits are in bytes: `intent` 800, `function` 1500, `usage` 1200. Each is generous, and a few sentences usually say it. Why bother: agents working in a world read these three texts to learn what your type is for, so they reach for it when it fits and use it the way you meant. People searching find the type by what they want to make, and the three texts let them tell at a glance whether it is the one they need. `asset.create("assetType", name)` scaffolds the file with all three keys, and a README whose first paragraph is a `[[describe]]` note. Each value starts with `[[describe]]` followed by a note on what to write; replace the whole value with your own words. A value or a README line that still starts with `[[describe]]` counts as not written yet, which the push's check of each asset it carries against its type reports, naming the file. A type you leave as it was is not asked, so older types stand. Many types at once, or one you would rather not write by hand: `services describe` lists the types that lack these texts and what filling them costs, and `{ mode = "all" }` writes them into the same files, where you edit them like anything else you wrote. Where the texts show up: `asset.inspect("<typename>", "assetType")` returns them as `detail.about`, `assetTypeRef:getAbout()` returns them as a table with the keys `intent`, `function` and `usage`, the type's `types/<typename>` guide page ends with an "About this type" section holding them, and the Inspector's Type section lists them at the top. The guide page is this README plus that section, so a README that explains the type well and an `about.yaml` that says what it is for read well together. ## Ask your assets to say what they are A type can ask each of its assets to carry a description: a file, written by the author or generated, that says what that asset is and what it is for. The people and agents who find an asset read it to decide whether it fits, and the author knows what it is for at the moment of making it. **1. Declare the file with a `described` check.** This is the whole requirement: ```yaml files: required: - path: "README.md" # any file name works kind: "file" content: - { check: "described", message: "Say what this widget is for and where it goes." } ``` With that in place: - An asset whose file is missing, empty, or still has a line starting with `[[describe]]` does not meet the type's requirements. `asset.validate` names it, `zm status` and `world.publishBlockers()` list it, and a push that carries it is refused with `message`. - `services describe` finds it (`mode = "find"` lists it and the price) and can write the description for it (`mode = "all"`). It writes only this file. For a YAML file that holds several texts, name the keys and their limits in bytes, the way this type does for `about.yaml`: ```yaml content: - check: "described" keys: - { key: "intent", max_bytes: 800 } - { key: "usage", max_bytes: 1200 } message: "Write intent and usage." ``` `headings` names sections a Markdown file must have. `assetTypes/README.md` has the full check. **2. Optionally, steer what gets generated with a `describe:` block:** ```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>" ``` `guidance` says what a description of your type covers, and `examples` names assets whose descriptions show the shape you want. Without the block, generation still works from the general describing guide and the check's `message`. An example is an asset of your type in the library whose description is a true, written one, never a scaffold's placeholder, and never the asset being described. When the library has none, leave `examples` empty rather than name one that is not. A type whose assets the model cannot perceive (a sound it cannot hear, a motion it cannot see) says so in `guidance`: the description comes only from what the asset's own files state, such as its name and the `.metadata` where a generation service records the prompt that made it, and when they state nothing the model answers `cannot` with that reason. `services describe` then fails that one asset with the reason and leaves its file as it was. **3. Start the file unwritten in your template.** Put a heading and one line that starts with `[[describe]]` and a short note on what to write, in `template/<file>`, so a new asset starts unwritten rather than with text that only looks written. Do not put example content in it: every new asset carries the template verbatim, and the same text on many assets makes them impossible to tell apart in search. Types whose assets say what they are through their own content (a mesh, a texture, a sound) leave this out: declare nothing and nothing is asked. ## The `behavior.luau` contract `behavior.luau` is the type's code. It returns ONE table, and the keys below are the ones the framework reads off it for EVERY type — the surface you get by declaring them. Anything else on the table is your own: reachable by name through `require("@builtin::assetTypes.assetType.shared.ref").loadTypeModule("<typename>")` for a system that knows your type (`computeShader` publishes `dispatchKey` that way), and never called by the framework. ```luau local M = {} M.ref = { ... } -- methods on every AssetRef of this type M.modules = { ... } -- shared code the instances reach M.global = {} -- reserved key; ship the empty table function M.onCreate(name, opts) ... end return M ``` ### The tables | Key | Shape | What the engine does with it | |-----|-------|------------------------------| | `M.ref` | `{ [name] = function(self, ...) }` | Every function becomes a method on every `AssetRef` of this type: `ref:name(...)`, with `self` the ref. This is how a type gives its instances an API. Two names in here are contracted — see below. | | `M.modules` | `{ [name] = require(".sibling") }` | Shared code the type's instances reach through `asset.containing(__FILE__).modules.<name>`, resolved by the instance's pinned `typeRef` guid. See the section above. | | `M.refShapes` | `{ [method] = "TypeName" }` | Declares the result type of a `M.ref` method so the LSP can check what a call site does with it. See the `M.refShapes` section below. | | `M.events` | an events schema | The events an ASSET of this type fires, declared the way a component declares its own. Readers subscribe through `ref.events.<name>:connect(...)`; firing authority stays with the type. Keyed by the asset's guid, so every resolver of the same asset shares the signals and a re-resolved ref re-attaches to subscriptions already there. | | `M.namePattern` | a Lua pattern string | The name shape `asset.create` enforces for instances of this type, replacing the default `^[A-Za-z][A-Za-z0-9_]*$`. | | `M.global` | `{}` | Reserved. Ship the empty table. | ### The lifecycle hooks Each is optional; a type that omits one costs nothing. The engine calls them: | Hook | Signature | When it fires | |------|-----------|---------------| | `M.onCreate` | `(name, opts) -> { [filename] = contents }` | On `asset.create("<type>", name, opts)`. Returns the files that scaffold the new instance, as a map of relative path to contents; the framework writes them. The `opts` type annotation is the schema `asset.create` validates the caller's arguments against, so annotate it. | | `M.onReplace` | `(dest, files) -> { [filename] = contents }` | On an `asset.create` that writes over an asset already at `dest`, after `onCreate`. Receives the files `onCreate` produced and returns the files to write, so a type that re-derives its content (a rig re-imported from its source file) can carry what an author added to the asset it replaces. Optional. | | `M.onRegister` | `(self)` | Once per instance, the first time it registers: on `engine.onWorldLoaded` for instances already in the world, immediately on a live `asset.create`, and when an instance arrives after that sweep (installed, pulled, or synced from a peer). Guarded by the instance's path, so a double trigger never double-registers. An instance that leaves the runtime releases the guard, so one arriving at the same path again registers. This is what makes "write an asset into the world and it takes effect live" work for content that registers into a runtime registry. The `@builtin` library is excluded from the sweep. | | `M.onChange` | `(ref, change)` | On every VFS write to a file INSIDE one of this type's instances. `change` is `{ path, asset, type, kind, origin }`: `kind` is `"edited"` or `"seeded"`, `origin` is `"local"` or `"remote"` (an importer runs on the originator only). **Filter on `change.path`**: the hook fires for any file under the folder, so act on the one you care about. It runs as its own task and may wait on what it reads: a `vfs.read` of bytes only the blob store holds (a binary file on the web build) fetches them. The writes to one asset reach the hook in the order they were made, each once the hook before it has finished. A re-entrancy guard suppresses writes back into the same asset routed inline from the hook, and a write the hook makes is routed on a later frame like any other, so the hook must be convergent on its own: diff the meaningful state and short-circuit while your own regeneration is in flight. | | `M.onDelete` | `(ref)` | When an instance of this type leaves the runtime: it is deleted, or the engine swaps away from the world binding that held it. Its files are gone from `/zero/source` by then. A removal routed while the instance's `onChange` is waiting reaches `onDelete` once that hook, and every write queued behind it, has finished. On a swap the instance still exists in the world it belongs to, and a VFS write the hook makes reaches the world now bound. | | `M.validate` | `(assetRef) -> { { code, message, severity? } }` | On `asset.validate`, after the structural `type.yaml` check, for the type's own SEMANTIC validation. `severity` defaults to `"error"`; error-severity problems flip `ok` to false, warnings do not. A hook that raises or returns a non-table is itself reported as a `validate.hook_failed` error. `world.push` runs this per user asset, so declaring it enforces your type's rules at publish time with no further wiring. | ### The two contracted `M.ref` names Most `M.ref` methods are your type's own surface: name them what you like, return what you like. Two are read by the engine and mean the same thing for every type, so their shape is fixed: - **`instantiate(self, target?, opts?) -> (root, idMap)`** — makes an instance part of the scene. Defining it is the whole opt-in: `ref:canInstantiate()` is true exactly when it exists. Its **return is a contract** — see the next section. - **`inspect(self) -> detail`** — the type-specific half of `asset.inspect`. See its section below. ### Names a type cannot shadow Some keys resolve on every `AssetRef` before per-type dispatch, so an `M.ref` entry of the same name is never reached: `canInstantiate`, `getSource` / `getBytes` / `getText`, `exists`, `deps`, `meta`, `runtime`, `events`, `modules`, `typeRef`, and the residency flags `has_backing_asset`, `has_runtime_changes`, `cpu_resident`, `gpu_resident`. These are the behaviours every asset must expose identically, which is why they win. ### Reloading A `behavior.luau` edit ripples to existing refs with no restart: dispatch reads `mod.ref` fresh each time and `require`'s cache is re-run in place. A type whose folder appears at runtime is picked up on the next dispatch — negative results are not cached either. ## The names your type's assets hold (`references:`) An asset that names another asset by a string depends on it: the named asset travels with it into a pack or a pull, and a name nothing answers to is an unresolved dependency `worldValidation` reports and the push gate refuses. The engine reads `require(...)` and the asset lookups on its own; a name your type's format or API carries anywhere else is one you declare, in `type.yaml`: ```yaml references: # A top-level key of this type's own files that holds a name (or a table of them). keys: - { key: "shader", type: "shader" } # A call's argument, counting from 1, wherever the call is written. args: - { call: "g:node", position: 2, type: "procNode" } # A field of the options table a call takes. fields: - { call: "fx.beam", field: "material", type: "material" } ``` `type` is the category the name resolves in, one of `asset.categories()`. An argument declared once per category, at the same `call` and `position`, takes the name from whichever category answers. A key or a field holds one category: declared again with another `type`, it takes the later one. The block is declared as the type registers, when the library or the world holding it is laid into the VFS, so every reference table reads it whatever script has or has not run. `asset.declareReferenceKey`, `asset.declareReferenceArg` and `asset.declareReferenceField` declare the same things from a script, for a surface that is no type's. ## What search does with your type (`indexing:`) A type declares what search embeds for its instances. **This is not optional and there is no useful default**: ZeroMind runs your declaration and adds nothing of its own, so anything you do not point at is absent from the index — silently, and for every instance of the type forever. Twenty types once shipped with no `indexing:` block and every instance of them was unfindable. A type whose instances are never searchable (a run record, a log) says so with `indexing: none`; every other type declares a recipe. A type without an `about.yaml` beside its `type.yaml` refuses every push that carries it, whether or not the push edited the type. Texts in it that are not written yet follow the rule every `described` file follows: they refuse the push that edits, stages or commits the type. Two words carry the whole thing, and they are the same two the search tool exposes: - **`identity`** — what an instance IS. For anything you can look at, that is the picture (`content:` + `modality: image`, matched directly by a text query). For everything else it is the authored text that says what it is. - **`capability`** — what it DOES and how it is made. Code, settings, the model-written summary of them. A type with no behaviour has no `capability` entry. A type with nothing to look at has no image. Leaving a slot empty is a statement; filling it with whatever happens to be lying around is not. The one you have to decide when authoring a type is: *for an instance of this, what is the thing a person would recognise it by, and what is the thing it does?* A texture answers "the image" and "its compression settings". A module answers "its README" and "its code". Write those two answers into `indexing:` and the rest follows. Three specifics worth knowing before you write one: - **`derive` is instructed by this type's own `README.md`.** A model reads an instance's source and writes a description; what it embeds is the description, not the source. It follows your README to know what it is looking at, so a type whose README says what its instances are gets good derivations for free. There is no prompt to name. - **`derive` loses detail.** It keeps the main technique and drops secondary ones. If the source is code you want searchable by its own vocabulary, declare the same files a second time as `capability` with `extractor: verbatim`. Two entries, same role, different failure modes. - **Never `source: { field: name }`.** A filename is one or two words with no usable embedding, and a corpus indexed that way answers "language runtime" with `say_runtime_2.soundClip`. `facets:` is the second stage: a `file:` embedded whole (`.metadata`, so keys nobody declared still get indexed) plus computed keys that state a value for every instance including `false` — the raw file can imply "not rigged" and can never say it. The full schema, every extractor and the facet sources are in [`assetTypes/README.md`](../README.md); the scaffolded block with inline guidance is in [`template/type.yaml`](template/type.yaml). ## A container whose contents work together (`system: true`) A type that is a container can say its contents are one working whole by declaring `system: true` at the top level of its `type.yaml`. `package` declares it: the components, modules, scenes and tools a package ships are parts of one system. The declaration is plain data, read from the decoded `type.yaml` (`require("@builtin::assetTypes.assetType.shared.declaration").of("package").system`), and a type that leaves it out is an ordinary type. ## What your type looks like (`preview:`) A type declares how its instances are pictured, and the engine makes the picture when something needs it: staging an instance whose `preview.png` is missing or pictures content it no longer holds queues a render, a view that shows the instance asks for one, and `ref:preview()` renders one on demand. An edit renders nothing on its own. Each `preview.png` records the content it pictured, which is how a stale one is told from a current one. The preview studio owns the light, the backdrop, the framing and the camera, and nothing in the world reaches it, so an instance pictures the same in every world. Declare one of four recipes: | `kind` | The picture is | Your type provides | |---|---|---| | `instantiate` | the asset stood in the studio through its own `instantiate` | `ref.instantiate` | | `image` | a file the instance holds, fitted to the frame, nothing rendered | `source.files`, the candidate files in order | | `surface` | the asset painted on a builtin mesh | `mesh`, and `ref.previewMaterial(self) -> { material }` | | `custom` | whatever `ref.preview(self, opts)` returns | `ref.preview` | ```yaml preview: kind: surface mesh: sphere ``` A scene-instantiable type that declares nothing still answers `ref:preview()` through its `instantiate`, but persists no picture: the declaration is what makes the engine keep one. List `preview.png` among the type's files so an instance may hold it. The picture is findable only when `indexing.content` names it. The two are separate statements, and neither is derived from the other: ```yaml indexing: content: - role: identity modality: image source: { file: "preview.png" } ``` `@builtin::assetTypes.assetType.shared.previewRecipe` reads the declaration; the scaffolded block with inline guidance is in [`template/type.yaml`](template/type.yaml). ## Typing a result from the instance (`M.refShapes`) Every method on `M.ref` is checked against the type its `--!return` names, and every asset of the type gets the same one. That is right for most methods and wrong for the ones whose result is shaped by the ASSET: a method answering one entry per child folder, per row of a config, per binding an input map declares. The widest true annotation for those is `{ [string]: Thing }`, and an indexer accepts every key — so a caller's typo reads as valid and nothing reports. `M.refShapes` lets the type state the result per instance. Each entry is `function(self) -> (typeExpression, source?)`: a Luau type expression for THIS asset, and the module whose type vocabulary the expression uses. Read the asset; never run it — stating a type must not take effect. ```lua -- inputMap.assetType/behavior.luau — the shipped example. -- `activate()` hands back one handle per control the map declares. 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)` resolves and `map.noexisting` is reported with the map's real controls. Without it, both pass silently. ### What the call site has to say A per-instance type is matched by the asset's IDENTITY, so it applies only where the reference the method is called on says WHICH asset. Two spellings do: ```lua -- a component field, whose declared default names the asset public = { map = Field.assetRef("inputMap", "@builtin::inputMaps.default", Sync) } local controls = public.map:activate() -- typed for THAT map -- an annotation, naming category and identity local m: AssetRef<"inputMap", "@builtin::inputMaps.default"> ``` `asset.resolve("<identity>", "<category>")` carries the CATEGORY, so the methods the category defines are checked on the result — but not which asset it found, so a per-instance result keeps the category's declared return. A reference that names no asset (`asset.resolve(someVariable)`, a value passed in as a parameter) carries neither, and calls on it are unchecked. That is the same rule everywhere: the checker states what the code states, and a name computed at runtime states nothing. ### The result is a value, not a binding The type belongs to the expression, so it travels the way any inferred type travels. Indexing the call's result is checked; stashing it in a module local and indexing it from another function is not, because the local's declared type is what carries across — and `any` (or no annotation) carries nothing: ```lua -- checked: `d.greting` is reported function awake() local d = public.dialogue:lines() d.greeting:say() end -- NOT checked: `lines` is a module local typed `any` local lines: any = nil function awake() lines = public.dialogue:lines() end function start() lines.greting:say() end ``` Bind what you need at the call site and the names stay checked in both places — the asset-derived type at the boundary, ordinary scoping after it: ```lua local lineGreeting = nil function awake() local d = public.dialogue:lines() lineGreeting = d.greeting -- `d.greting` is reported here end function start() lineGreeting:say() end ``` ### When nothing is reported and you expected something From a call site, a type that is correct and a type that was never published look the same: no diagnostic either way. `require("@builtin::assetTypes.assetType.shared.refShapes").published()` answers which it is. It returns two maps — the category surfaces, and the per-asset results keyed by identity and then by method: ```lua local shapes = require("@builtin::assetTypes.assetType.shared.refShapes").published() shapes.categories.dialogue --> "{ lines: () -> any, lineNames: () -> { string } }" shapes.returns.Shopkeeper.lines --> "{ browsing: Line, farewell: Line, greeting: Line, wares: Line }" ``` An identity absent from `returns` was never published for, which is a different thing from published-and-correct — and the reason to look here rather than at the call site. The answers are recomputed when an instance is written, so a control added to a map reaches the checker with no restart. Only types that declare `refShapes` are read per instance, and at most 64 assets of one type are — past that the type keeps its declared return and the engine log names what was dropped. ## The instantiate hook (`M.ref.instantiate`) — a contracted return A type opts into becoming part of the scene by defining `instantiate` on its `ref` table. That is the whole opt-in: `ref:canInstantiate()` is true exactly when the hook exists, so consumers offer a scene path — an `Asset.source` field, a viewport drop, a tool argument — by CAPABILITY rather than by a list of type names. Unlike `inspect`, this hook's **return is a contract**. A caller writes one piece of code against every instantiable type, so what comes back cannot vary by type: ```lua -- behavior.luau local Instantiable = require("@builtin::assetTypes.assetType.shared.instantiable") local M = {} M.ref = { instantiate = function(self, target, opts) local root = Instantiable.root(self, target, opts) -- IN: the base opts -- ... compose whatever this type is, under `root`, NOW ... return Instantiable.result(self, root, idMap) -- OUT: the contract end, } return M ``` **IN.** `target` is an owning entity ref: the instance lands under (or, for a hierarchy type, onto) that owner. With no target the type spawns a fresh root. `position`, `rotation`, `scale`, `name` and `temporary` mean the same for every type — `Instantiable.root` applies them to a root you mint, `Instantiable.place` to one you adopt, so you never re-read the spec. Honour more opts of your own if your type needs them, and document them in the hook's `--!arg` docs. **OUT.** Return `(root, idMap)` through `Instantiable.result`: - **`root`** — the composed root, as an `EntityRef`. Composition is **synchronous**: everything your type builds is live when you return, so the caller can parent to it and read its components in the same statement. Do not defer the work to a component's `awake` and return an empty shell — a root that is not live is refused. - **`idMap`** — the `originalId -> runtimeId` map naming what you spawned, or nil for a type with no addressable children (`result` normalises it to `{}`). **A caller never receives nil.** A component that re-composes your asset on every load keeps this map and passes it back in, which is how a cross-entity reference into the composition survives a reload. `AssetRef` runs every `instantiate` through `result` on the way out whether or not your type called it, so returning something else fails at your own call rather than handing a caller a nil root. Calling it yourself is still how you say what you return, and running it twice changes nothing. `@builtin::assetTypes.assetType.shared.instantiable`'s README is the full reference for both halves. ## The inspect hook (`M.ref.inspect`) `asset.inspect(ref)` resolves `ref`, builds a common envelope shared by every asset (`identity`, `name`, `guid`, `source`, `typeName`, `typeDefinitionPath`, `scope`, `origin`, `description`, `tags`), then calls the resolved type's own inspect hook — `M.ref.inspect(self)` on `behavior.luau` — for the type-specific `detail`. The hook returns *only* `detail`; the framework fills in everything else: ```lua -- behavior.luau local M = {} M.ref = { inspect = function(self) -- self.path is the asset's own folder. Parse the asset's OWN -- files — source text, a native payload header, its `.metadata` -- — never runtime state (a live component instance, a GPU -- upload, a compiled schema): inspect must work on an asset that -- hasn't been compiled, uploaded, or registered yet. return { -- type-specific fields, whatever this type wants to surface } end, } return M ``` A type that omits `M.ref.inspect` yields the generic record: the envelope alone, `detail = nil`. That's a valid, working state — not an error — but it means agents calling `asset.inspect` / `tools.use("assets","describe", ...)` on an instance of the type see only identity and scope, none of what makes an instance of it meaningful. Declaring the hook is what makes a type's instances inspectable for what they actually are. A hook that raises leaves `detail = nil` and sets `record.warning` to the error text — `asset.inspect` itself never raises for a resolved ref. ## Discovery - `asset.list("assetType")` — every registered asset type. - `asset.inspect("<typename>")` — the type's identity, source path, and this README, plus its `about.yaml` texts as `detail.about`. - `asset.resolve("<typename>", "assetType")` — the `<typename>.assetType` asset itself (used by the validator to find the type's `type.yaml`). ## Related - `assetTypes/README.md` — the full `type.yaml` schema and validator rules. - `@builtin::assetTypes.assetType.shared.instantiable` — the instantiation contract's shared implementation, both halves. - Every other `*.assetType/` here — the concrete types built on this meta-type. ## The Inspector a type ships Every type names the file its Inspector sections come from with `inspector: { type: "inspector.luau" }` in its type.yaml. `asset.create("assetType", name)` scaffolds the block and an `inspector.luau` whose Contents section lists an asset's files, built from `ctx.parts`. `asset.validate` on a type that names none reports `assetType.inspector_required` (an error for a `@builtin` type the engine's library authors; a warning for a world's own, and for one the library carries by reference, which the world that published it answers for), and one whose file does not load `assetType.inspector_invalid`. ## In the Inspector Type: what the type.yaml declares (suffix, container, primary files, the settings and inspector blocks), whether the type ships a behavior, how many instances it has, and **Open** for its files. Schema: the settings every instance carries, as read-only typed controls at their defaults (a type whose schema is per instance says where it is declared). Instances: a link to each of the first 20 assets of the type, and how many there are when there are more.

# preset A preset holds typed values for one declarer's settings schema: an assetType's, an importer's, a component's, or any asset that declares its own settings. `preset.capture` saves the settings something has now, `preset.apply` writes a preset's values into something its target governs, `preset.values` reads them checked against the target's current schema, and `preset.setValues` replaces them, checked first. Exposed as the `preset` global via `--!global preset`. A preset's `preset.yaml` names its target as a guid envelope, `target: { __ref: <guid>, type: <type>, name: <name> }`, which the preset's `.refs` pins by guid with the target's checksum. A target written as an identity string is accepted on read, resolves by identity, reads as unpinned, and is rewritten as the envelope on the preset's next local edit. ## Exports - `preset.values(source: AssetRef<preset>) -> ({ [string]: any }, Report)` — the values that pass the target's current schema, and a report naming every one that does not. - `preset.apply(source: AssetRef<preset>, into: AssetRef | ComponentTarget) -> ApplyResult` — write the valid values into an asset the target governs, or into a component on an entity whose component is the target. Struct groups merge field by field. Raises when another declarer governs `into`. - `preset.capture(from: AssetRef | ComponentTarget, name: string, opts?: CaptureOpts) -> AssetRef<preset>` — save an asset's settings, or a component's live values on an entity, as a new preset targeting the declarer that governs them. A bare name lands in `/source/presets/`; an absolute `.preset` path lands where it says. - `preset.setValues(source: AssetRef<preset>, values: { [string]: any })` — replace the whole values table; any violation refuses the write, naming every one. - `preset.defaults() -> { DefaultRow }` — the world's Preset Manager rows, in order, each resolved with its problems. - `preset.setDefaults(rows: { DefaultRowInput })` — replace every row; every row is checked first and any problem refuses the write, naming every one. - `preset.addDefault(source: AssetRef<preset>, opts?: { filter: string?, at: number? }) -> number` — add a row for the declarer the preset targets; returns its index. - `preset.removeDefault(index: number)` — remove one row, keeping every other row as written. - `preset.defaultFor(declarer: AssetRef | string, path: string) -> ({ [string]: any }?, Match?)` — the values a new thing at `path` would take from the rows, and the row that gives them. Types: - `ComponentTarget = { entity: string, component: string }` — a component on an entity. - `Report = { format: string, target: string, targetGuid: string?, pinned: boolean, targetChanged: boolean, rejected: { Violation } }` — `target` is the target's identity; `pinned` is true when `.refs` pins the target's guid; `targetChanged` is true while the pinned checksum differs from the target's current one. - `Violation = { path: string, message: string }` - `ApplyResult = { applied: { string }, rejected: { Violation }, targetChanged: boolean }` - `CaptureOpts = { overwrite: boolean? }` — `overwrite = true` re-authors an existing preset, keeping its guid. - `DefaultRowInput = { preset: any, target: any?, filter: string? }` — a preset, its declarer (the preset's own target when omitted) and a filter (empty matches everything). - `DefaultRow = { index, target, preset, filter, targetGuid, presetGuid, targetName, presetName, problems }` - `Match = { index, target, preset, path, rejected, problem? }` — the row a creation took and the path it read. ## Usage ```luau -- Capture a texture's settings, then apply them to another texture local p = preset.capture("hero_sprite", "pixel_art") preset.apply(p, "enemy_sprite") -- Apply a component preset to a component on an entity preset.apply("synty", { entity = id, component = "Locomotion" }) -- Capture a component's live values local tint = preset.capture({ entity = id, component = "Model" }, "red_tint") -- Read the values and what the target rejects local values, report = preset.values("pixel_art") for _, v in ipairs(report.rejected) do print(v.path, v.message) end -- Replace the values preset.setValues("pixel_art", { filter = "nearest", generateMipmaps = false }) ``` ## Notes - Every read re-checks the values against the target's current schema, so a value a later schema drops or retypes is reported by path rather than applied. - `asset.create("preset", name, { target = <identity or guid>, values = { ... } })` authors a preset directly, with the same checks as `preset.capture`. - The Preset Manager rows are documented in `preset.defaults`; the filter grammar in `preset.glob`. - Submodules: `preset.document` (the `preset.yaml` format), `preset.target` (target resolution and checking), `preset.heal` (rewriting an older preset document in the current form on a local edit).

# entity_signals Per-entity destroy signals, surfaced on the entity proxy as `entity(id).onDestroying` and `entity(id).onDestroyed`, plus the dispatch the despawn pipeline calls to fire them. ```lua local boss = entity.find("Boss") boss.onDestroying:Connect(function() -- runs BEFORE teardown — final state is still readable saveBossStats(boss.component.get("Combatant").public) end) boss.onDestroyed:Connect(function() log.info("boss fully cleaned up") end) entity.despawn(boss.id) -- onDestroying fires, then teardown, then onDestroyed ``` ## Order `onDestroying` and `onDestroyed` are `Signal`s (see `signal.module`), created on first access. The despawn pipeline drives the order. For a cascade rooted at one `entity.despawn(root)` call: 1. `onDestroying` fires across the whole subtree, root first — before any component teardown, so handlers read final state. 2. components tear down (`onDestroy(self)` per component), leaves first. 3. `onDestroyed` fires per entity as it is removed, leaves first. `onDestroying` handlers must not yield, and the entity is frozen against reparenting / re-mutation during the destroying window. An entity nobody observes costs nothing and fires nothing. ## Entity-keyed tables A module that keeps per-entity state for something to read every frame (a registry a render feature walks, a set of marked entities) declares its table with `entityKeyed`. When an entity is despawned, by `entity.despawn`, a parent's cascade, a scene rebuild or reload, or a mode flip, its id leaves every such table, so the reader only ever meets entities in the world and its cost follows them. ```lua local EntitySignals = require("@builtin::modules.entity_signals") local marked = EntitySignals.entityKeyed({}) function M.mark(id: string) marked[id] = true end ``` The table is one of the engine's own records: a module-state restore leaves it as it stands, so an id that left it stays out.

# transform Math helpers for positions, rotations, and directions on transforms. Exposed as the global `Transform` table via `--!global Transform` — no explicit require needed in user code. Functions that take an entity accept either an entity ID string or an entity proxy table from `entity("id")`. ## Exports Look-at and entity-aware helpers: - `Transform.lookAtQuat(fx, fy, fz, tx, ty, tz) -> (qx?, qy?, qz?, qw?)` — quaternion from origin toward target. Nil when degenerate. - `Transform.lookAt(entity, txOrTarget, ty?, tz?) -> (boolean, string?)` — make an entity face a world position or another entity. Both slots read world space: the subject and an entity target are read as `entity(id).position` and the aim is written as `entity(id).rotation`, so a parent under either one still leaves the aim on the point named. Returns whether the rotation was written, and the reason when it was not. - `Transform.distance(x1, y1, z1, x2, y2, z2) -> number` — Euclidean distance between two points. - `Transform.distanceBetween(entityA, entityB) -> number?` — distance between two entities' world positions. Nil when either is unresolvable. - `Transform.direction(fromX, fromY, fromZ, toX, toY, toZ) -> (dx, dy, dz)` — unit direction vector. - `Transform.directionBetween(entityA, entityB) -> (dx, dy, dz)` — unit world-space direction between two entities' world positions. Rotation shapes: A quaternion **constructor** here returns the four components as four separate values, so a caller either names them or braces the call to make one table: ```lua local qx, qy, qz, qw = Transform.quatFromAxisAngle(0, 1, 0, math.rad(90)) entity("cam").localRotation = { Transform.quatFromAxisAngle(0, 1, 0, math.rad(90)) } ``` A rotation-taking **surface** reads that table through `Transform.toQuaternion`, which also takes euler DEGREES — so `{ qx, qy, qz, qw }`, `{ x =, y =, z =, w = }`, `{ pitch, yaw, roll }` and `{ pitch =, yaw =, roll = }` all mean the same thing wherever a rotation is assigned: `entity(id).rotation` / `.localRotation`, `entityOps.spawn`, `entityOps.transform`, and the capture viewpoints. - `Transform.toQuaternion(rotation, label?) -> { qx, qy, qz, qw }` — the shared reading of a rotation a caller wrote. Raises when the value matches no form, naming what arrived; a value that is one of the shapes a quaternion helper returns is named as such along with the packing it goes in as. - `Transform.tryQuaternion(rotation, label?) -> ({ qx, qy, qz, qw } | nil, message?)` — the same reading without raising, for a surface that wants to raise the message at its own caller's line. - `Transform.readVec3(value, label?) -> { x, y, z }` — the same for a vector. - `Transform.snapVec3(v, step) -> { x, y, z }` — quantize a vector to a step grid. Quaternion construction / conversion: - `Transform.quatFromYaw(yaw)`, `Transform.quatFromYawPitch(yaw, pitch)`, `Transform.quatFromAxisAngle(ax, ay, az, angle)` — quaternion constructors. - `Transform.quatIdentity()` — identity quaternion. - `Transform.euler(qx, qy, qz, qw) -> (yaw, pitch, roll)` and the named alias `Transform.quatToEuler`. - `Transform.eulerToQuat(yaw, pitch?, roll?)` — euler-to-quaternion in YXZ order. Lerps and interpolation: - `Transform.lerp(ax, ay, az, bx, by, bz, t) -> (x, y, z)` — vec3 lerp. - `Transform.lerp1(a, b, t) -> number` — scalar lerp. - `Transform.normalizeAngle(a) -> number` — wrap angle into `[-pi, pi]`. - `Transform.lerpAngle(a, b, t) -> number` — shortest-arc angle lerp. - `Transform.slerp(ax, ay, az, aw, bx, by, bz, bw, t) -> (qx, qy, qz, qw)` — quaternion slerp with shortest-path and near-parallel fallback. Quaternion operations: - `Transform.quatMul(...) -> (qx, qy, qz, qw)` — `qa * qb` composition. - `Transform.quatInverse(qx, qy, qz, qw) -> (qx, qy, qz, qw)` — inverse (= conjugate for unit quats). - `Transform.quatRotateVec(qx, qy, qz, qw, vx, vy, vz) -> (x, y, z)` — rotate a vec3 by a quaternion. Pose helpers: - `Transform.orbit(centerX, centerY, centerZ, radius, height, angle) -> (x, y, z, qx, qy, qz, qw)` — orbital pose facing the center. - `Transform.worldToLocal(...)` / `Transform.localToWorld(...)` — pose-space conversions. Nested `Transform.vec.*` namespace (component-wise vec3): - `Transform.vec.add`, `sub`, `scale`, `dot`, `cross`, `length`, `normalize`. Types: - `Vec3 = { x: number, y: number, z: number }` - `EntityRef = string | { entityId: string }` ## Usage ```luau -- Look-at by coordinates or by target entity: Transform.lookAt("cam", 0, 1, 0) -- an entity target resolves to that entity's world position local aimed, why = Transform.lookAt("cam", "box") -- Orbit pose around a point: local x, y, z, qx, qy, qz, qw = Transform.orbit(0, 1, 0, 5, 2, t) entity.find("cam").localPosition = { x, y, z } entity.find("cam").localRotation = { qx, qy, qz, qw } -- Quaternion math: local qx, qy, qz, qw = Transform.quatFromYawPitch(math.pi / 4, 0) local sx, sy, sz, sw = Transform.slerp(0, 0, 0, 1, qx, qy, qz, qw, 0.5) -- Component-wise vec3 helpers: local nx, ny, nz = Transform.vec.normalize(1, 1, 0) ``` ## Notes - The `--!global Transform` directive promotes the module's typed functions onto the runtime universe's globals bucket, so `Transform.*` is available without any per-source `require`. - Entity-aware functions (`lookAt`, `distanceBetween`, `directionBetween`) report a missing entity or a missing transform in their return value rather than raising: `lookAt` answers `false, "unresolved"` / `"no-transform"` / `"incomplete-target"` / `"degenerate"`, `distanceBetween` answers `nil`, and `directionBetween` answers zeros. - Quaternion APIs operate on raw `(qx, qy, qz, qw)` tuples for parity with the entity proxy's `localRotation.get`/`set`. Use `Transform.quatIdentity()` rather than hand-rolling `(0, 0, 0, 1)`. - `Transform.slerp` flips the second quaternion if `dot < 0` to take the shortest path, and falls back to lerp+normalize when the inputs are within `dot > 0.9995` to avoid `1/0` near-parallel issues.

# runtime_participation Reads and writes the RuntimeParticipation lifecycle axis for an entity, and answers the save / edit-liveness / play-liveness questions that follow from a mode. It is the one source of truth for the four modes — WorldEntity, PrototypeOnly, EditorOnly, RuntimeOnly — so save and play-mode code agree on what each mode means (which entities persist to the world, which are live in edit, and which are live in play). Location: `src/lua/lib/modules/api/engine/runtime_participation.module`

# luau_introspect (module) Parses Luau/asset source TEXT into structured declarations. Pure string/pattern parsing (`string.find` / `string.match` / `string.gmatch`) over the literal source — no compiling, no VM spawn, no runtime state, no engine FFI. Given source text, it extracts what is written in the file. This is the shared parser every per-assetType `M.ref.inspect` hook uses to turn a component/module/tool's own source into the structured record `asset.inspect` returns. ## Exports - `docstrings(src) -> DocMap` — scans `--!desc` / `--!arg` / `--!return` / `--!example` comment runs and binds each run to the name of the declaration on the next non-comment line (the identifier after `function`, `public:`, `local function`, or `M.`). - `publicFields(src) -> { FieldEntry }` — parses `public = { name = Field.<kind>(default, mode), ... }` table-literal entries and module-scope `public.<name> = Field.<kind>(...)` assignments. - `events(src) -> { EventEntry }` — parses `events = { name = Event(payloadSchema?, syncMode?), ... }` table-literal entries. - `methods(src) -> { MethodEntry }` — parses `function public:<name>(...)` / `typed function public:<name>(...)` declarations (params + optional return type). - `lifecycleHooks(src, catalog) -> { string }` — top-level `function <name>(` declarations whose name is in the caller-supplied `catalog` array. - `moduleExports(src) -> { ExportEntry }` — parses `M.<name> = function` assignments, `function M.<name>(...)` declarations, and a trailing `return { foo = foo, ... }` export table. - `forSource(src, computeFn) -> any` — memoises `computeFn(src)` keyed on `src` itself in a module-local table. The same source text returns the cached result without re-running `computeFn`; different source text recomputes. Keyed on the source content (not an asset checksum) because composite/container assets (component folders, scene folders, etc.) all hash to the empty-string checksum — a checksum-keyed cache collapses every such asset's detail onto whichever one was inspected first. ## Usage ```luau local Introspect = require("modules.luau_introspect") local src = self:getInitScript() local detail = Introspect.forSource(src, function(s) return { fields = Introspect.publicFields(s), events = Introspect.events(s), methods = Introspect.methods(s), hooks = Introspect.lifecycleHooks(s, lifecycleCatalog), } end) ``` ## Notes - Every function is a pure string→table transform: same source text in, same structured table out, every time. No reads of live component state, no entity/world queries. - Structural scanning runs over a comment- and string-aware **mask** of the source (a same-length copy where comment bodies and string-literal contents are blanked to spaces, delimiters and newlines preserved). Pattern matches and brace/paren balancing run on the mask — so a brace, `Field.`, `Event(`, or a whole entry that appears inside a comment or a string literal never registers — while captured values are sliced from the original source at the same (aligned) indices. This makes the parser robust to apostrophes in comments, commented-out entries, string defaults containing `}` / `Field.` / `Event(`, and `[[ ]]` long strings. - `default` / `category` are raw trimmed source-text slices (with any trailing comment stripped), not evaluated values. - For a **ref constructor** (`Field.assetRef` / `dataRef` / `resource` / `componentRef`) the FIRST positional argument is the category / contract / componentType selector, captured under `category`; the SECOND argument is captured under `default`. - For every **other** Field kind the first argument is the `default` and `category` is nil. - A trailing `Sync` / `NoSync` identifier is captured as `sync`, tolerating a trailing comma or a trailing comment after the last argument. - Field/Event entries whose key is a computed or indirect expression (`[expr] = Field.number(...)`) are omitted — only literal identifier keys are recognised. - `methods` captures a `...` variadic parameter (as `name = "..."`), with its `: <type>` annotation when present. - A `--!desc` written above a field/event declaration (`<name> = Field.<kind>(...)` / `<name> = Event(...)`) or a `public.<name> =` assignment binds to that name in `docstrings`, and is folded into the corresponding `publicFields` / `events` entry's `desc`. - `lifecycleHooks` never hardcodes the lifecycle-callback catalog; the caller passes the list of names to match against. - `forSource`'s memo is bounded (oldest-key eviction) so a long session touching many distinct asset versions can't grow it without limit.

# assetType.shared.ref Builds the metatable every `AssetRef` (the `{ __ref, type, name, guid, identity, path }` envelope returned by `asset.resolve` / `asset.ref`) carries. Replaces the per-call C metatable that used to live in `crates/zero_scripting/src/ffi/bindings/asset.rs::attach_asset_ref_metatable`. ## Public API ```lua local assetRef = require("@builtin::assetTypes.assetType.shared.ref") -- Called by the Rust factory (push_asset_ref_handle) via -- _G.__build_asset_ref_proxy after the envelope fields are set. assetRef.build(envelope) -- attaches AssetRefMT, returns the table ``` The module exposes no invalidation surface — discovery is registry-driven and hot-reload is transparent (see "Discovery and hot-reload" below). ## Method dispatch order `ref.foo` is resolved in this order: 1. **Default methods** — `getSource` / `getBytes` / `getText` / `exists` / `inspect` and the lazy `meta` property. Per-type definitions cannot override these (engine contract from gh#1889). 2. **Per-type `ref` table** — discovered through `asset.resolve(<typename>, "assetType")` + `require(<identity>.behavior)`. The lookup resolves to whichever `<typename>.assetType/` folder is currently registered for the typename (built-in, user, or library-vendored) and pulls its `ref` methods. 3. **Nil** — unknown key, same shape as the original C metatable. ## Adding methods for a new asset type Drop a `behavior.luau` into the type folder: ``` src/lua/lib/assetTypes/<typename>.assetType/ ├── type.yaml -- structural spec (existing) ├── behavior.luau -- ref + global behaviour (new) └── template/ -- placeholder body (existing) ``` `behavior.luau` returns: ```lua return { ref = { --!desc Per-instance method on every `<typename>` AssetRef. myMethod = function(self, ...) ... end, }, global = { -- Reserved for the asset.<typename>.* surface — not consumed -- yet; included so the contract from gh#1889 lands cleanly. }, } ``` Within `ref` methods, `self` is the AssetRef envelope: `self.path`, `self.identity`, `self.guid`, `self.type`, `self.name` are available. Engine-required fields (`guid`, `path`, `identity`, `type`) must not be redefined. ## Discovery and hot-reload Type discovery uses the asset registry, so it doesn't matter where a `<typename>.assetType/` folder lives — engine built-ins under `@builtin::assetTypes.<X>`, user types dropped under `/zero/source/<X>.assetType/`, or types vendored inside an imported library all resolve identically. The dispatcher walks `asset.resolve(<typename>, "assetType")` → canonical identity → `require <identity>.behavior` on every miss; the asset registry is the cache for the resolve half and Luau's `_LOADED` is the cache for the require half. Hot-reload is transparent. When a `<typename>.assetType/behavior.luau` is rewritten through VFS, the engine's `invalidate_require_cache_for_state` re-runs the module and mutates the cached `_LOADED[<identity>.behavior]` table in place. Dispatch reads `mod.ref` on every access (rather than caching a sub-pointer), so existing AssetRefs see the new methods on the very next access — no Rust-side hook into this module is needed, and no invalidation API is exposed for callers to call. The same registry-driven path also handles type **registration** correctness: dropping a new `<typename>.assetType/behavior.luau` updates the asset registry, the next `asset.resolve(<typename>, "assetType")` returns the new ref, and AssetRefs of that type immediately gain the new methods. ## Why Luau, not Rust The asset surface needed per-category behaviour (`material:getProperties()`, `bundle:instantiate(entityId)`, `tool:run(args)`) and the old shape couldn't grow without an FFI change per method. Owning the proxy in Luau means: - Type-specific methods ship as content (the `<typename>.assetType/` folder), not engine code. - Adding a new asset type drops in a new folder; no Rust rebuild. - Methods can call any other Luau global (`vfs`, `asset`, `Material`, `entity`, etc.) directly, instead of going through narrow FFI primitives. ## Consumers - `crates/zero_scripting/src/ffi/bindings/asset.rs::attach_asset_ref_metatable` — the Rust factory that pushes envelopes invokes `_G.__build_asset_ref_proxy` once per push. - Every Luau call site of `asset.resolve` / `asset.ref` / `entity(id).component.X.material` / any binding declared `AssetRef<...>` — they all receive envelopes built through this module.

# yaml.module YAML decode + encode for authored engine content. Pure Luau, no engine dependencies — a general parsing library, not data-system plumbing. ```luau local Yaml = require("@builtin::modules.yaml") local doc = Yaml.decode(vfs.read(path)) vfs.write(path, Yaml.encode(doc)) ``` ## Supported subset - Block mappings (`key: value`) and block sequences (`- item`), nested to any depth. - Compact sequence-of-mapping entries (`- path: x` / ` kind: y`). - Flow collections — `{ a: 1, b: 2 }` and `[1, 2, 3]` — single line. - Plain scalars with type inference: `~` / `null` → nil, `true` / `false` → boolean, numeric literals → number, everything else → string. - Single- and double-quoted strings (`''` escapes a literal quote inside a single-quoted string; `\n` `\t` `\r` `\\` `\"` inside a double-quoted one). A quote opens a quoted scalar where a scalar begins — after `key:`, after a `- ` entry marker, or inside a flow collection — so a plain scalar carries an apostrophe as data (`note: the world's rules`). Quoted keys are read in flow mappings. - `#` comments — honored outside quotes, so a `#` inside a quoted string is kept as data. - Literal (`|`) and folded (`>`) block scalars — the bare indicators only. A block scalar's content is literal text: quotes (balanced or not), `#`, `key: value` and `---` inside it are data. - An optional leading `---` document marker. ## Loud-error contract Constructs outside the subset above raise instead of misparsing: anchors/aliases (`&`, `*`), tags (`!`), directives (`%`), multi-document streams (a second `---`), block-scalar chomping/indentation indicators (`|-`, `|+`, `>-`, `|2`, ...), tab indentation, and inconsistent indentation (both block structure and block-scalar bodies). Every error carries the offending line number (`yaml: line N: ...`), so a bad config points straight at the line to fix. Tab indentation is rejected everywhere — including block-scalar body lines whose leading whitespace contains a tab. A tab after the first non-space character of a line is content and passes through. ## API - `Yaml.decode(text: string): any` — decode a YAML document into a Luau value (table, scalar, or nil for an empty document). Raises on malformed input or an unsupported construct. - `Yaml.decodeWithComments(text: string): (any, boolean)` — decode as `decode` does, and report whether the text carries a comment by the decoder's own rule: a `#` at a line's start or after whitespace, outside a quoted scalar and outside a block scalar. Re-encoding the value drops such comments, so an editor that writes a document back reads this first. - `Yaml.encode(value: table): string` — encode a Luau table as YAML (block style, two-space indent, alphabetically sorted keys). Raises on values YAML can't represent (functions, userdata, non-string mapping keys). A top-level empty table encodes to an empty document, which decodes back to `nil` (the YAML empty-document ambiguity).

# json JSON encode/decode library for Luau. Encodes Lua values to JSON strings and decodes JSON strings back to Lua values. Used for communication with the Rust side of the engine, the VFS read/write bridge, and any wire-format that needs JSON. Pure Luau, no engine dependencies. Compact and pretty-printed encoders, plus a hand-rolled decoder that streams the input by position so it works under WASM as well as native. ## Exports - `Json.encode(value: any, indent?: string, currentIndent?: string) -> string` — compact encode. Functions / unknown types and NaN/Inf encode as `null`. - `Json.encodePretty(value: any, indentStr?: string) -> string` — pretty-printed encode with sorted object keys (diff-friendly). - `Json.encodeArgs(...: any) -> string` — encode varargs as a JSON array. - `Json.decode(str: string) -> any` — decode a JSON string. Returns the decoded value, or `nil` + error message on failure. ## Usage ```luau local Json = require("@builtin::modules.json") local widget = { type = "button", text = "Click Me" } local compact = Json.encode(widget) -- '{"text":"Click Me","type":"button"}' local pretty = Json.encodePretty(widget, " ") local decoded = Json.decode(compact) local v, err = Json.decode("oops") -- v = nil, err = error message ``` ## Notes - Object keys are sorted alphabetically in both encoders for consistent output across runs. - Numeric keys on objects are stringified at encode time (JSON has no numeric keys). Pure-integer key sets get detected as arrays via `isArray` and encoded with brackets. - NaN, +Inf, -Inf encode as `null` — JSON has no representation. Round trips through `decode` recover `null` (Lua `nil`), so they don't preserve. - Unicode `\uXXXX` escapes decode to UTF-8 by hand to stay WASM-safe. Only the BMP is covered; supplementary planes via surrogate pairs are not. - Functions encode as `null`. - Decode is character-streamed — no regex, no `string.match` patterns on the whole input — so the line-and-column information needs to be reconstructed from the position offset.

# assetType runtime The machinery that reads a `<typename>.assetType/behavior.luau` and turns its declarations into live behaviour. A `behavior.luau` is a table of declarations — `ref` methods, `modules` shared code, an `events` schema, a `namePattern`, `refShapes`, and the `onCreate` / `onRegister` / `onChange` / `onDelete` / `validate` / `settingsDefaults` / `settingsCorrections` hooks. None of it runs itself. This is the code that runs it, and it lives here because reading a type's declarations is the **assetType type's own behaviour** — the same way `material.assetType` owns what a `.material` does. ## Sub-modules | Module | Reads | Responsibility | |---|---|---| | `ref.module` | `ref`, `modules` | Builds every `AssetRef` envelope, attaches the shared metatable, and dispatches per-type methods and shared modules onto it. Also owns edit-mode write-behind persistence. | | `create.module` | `onCreate`, `namePattern`, `validate` | Backs `asset.create`: resolves the type, checks the name against its pattern, runs `onCreate` (or clones `template/`), and writes the instance. `validate.module` beside it checks a creation `opts` table against the type's `createSchema`. Before running `onCreate`, resolves the type's settings chain (below) and hands the result to the hook as `opts.settings`. | | `settings.module` | `settings`, `settingsDefaults`, `settingsCorrections` | A type's declared settings schema and where its values live (`type.yaml`'s `settings:` block). `Settings.resolveForCreate` layers the schema's own defaults, the type's own `settingsDefaults(name, opts, asked)` hook (a DEFAULT the schema can't express — a name-derived convention, a fact read off a payload the caller handed it, a value following a field `asked` shows a higher layer naming; any later layer overrides it), the Preset Manager, an importer's settings, the caller's `settings` table, then the type's own `settingsCorrections(values, name, opts)` hook (a CROSS-FIELD CONSTRAINT the schema can't express, applied last over the fully merged values). A correction over a default/preset/importer value lands silently; a correction that would override what the caller's own `settings` table explicitly asked for refuses the creation instead, naming the field and why. Neither hook is ever handed a table to mutate; each returns what it wants changed (`settingsCorrections` may also return a `{ [field]: reason }` table for that refusal message). `Settings.cloneValues` deep-copies a values table — `create.module` hands `onCreate` a copy, never the table it stamps. `Settings.valuesOf` / `writeValues` read and write an asset's own values file. | | `typeYaml.module` | `type.yaml` | The folder a type lives in and its parsed `type.yaml`, decoded once per content version of the file. `settings.module` and `inspector.module` read their blocks through it. `about` / `aboutAt` read a type's `about.yaml` (`intent`, `function`, `usage`), leaving out any key that is empty or still starts with `[[describe]]`; `aboutRows` and `aboutMarkdown` lay the texts out for the Inspector and the `types/<name>` guide. | | `inspector.module` | `type.yaml`'s `inspector:` block | Which inspector a type declares for its assets (`inspector: { type: ... }` or `{ instance: ... }`), and the declaration that file returns — the sections it adds, the generic ones it replaces, and their order — or the problem that kept it from loading. | | `onRegister.module` | `onRegister` | Fires an instance's once-only registration hook — on arrival, on world load, and for `@builtin` library instances. | | `changeDispatch.module` | `onChange`, `onDelete`, `refShapes` | Routes a VFS source write or a folder delete to the enclosing typed asset's type hooks. | | `refShapes.module` | `refShapes`, `ref` | Publishes what every `AssetRef<category>` answers to, so a member read on an asset-typed value is checked against that category's real surface. | | `events.module` | `events` | The per-asset event runtime behind `ref.events`. | | `instantiable.module` | `ref.instantiate` | The instantiation contract an asset type opts into: `root` stands the root entity, `place` applies the base placement opts to one the type adopted, and `result` shapes the `(root, idMap)` every `instantiate` returns. Also registers the `sceneInstantiable` field-constraint validator. | | `declaration.module` | `type.yaml` | The type's decoded declaration, read once and held until a write inside an `.assetType` folder; what every question about a type as a whole reads. | | `previewRecipe.module` | `type.yaml` `preview:` | How an instance's `preview.png` is produced: which of the four recipes (`instantiate`, `image`, `surface`, `custom`) the type declares, and what that recipe needs. | ## Reaching it ```luau local rt = require("@builtin::assetTypes.assetType.shared") rt.ref.loadTypeBehavior("material") ``` Fields resolve lazily. The prelude requires the sub-modules directly, in dependency order (`ref`, then `changeDispatch`, `onRegister.install()`, `refShapes.install()`) — a table that required all six on load would take that ordering away from it.