# services.shared.describe The work behind `services describe`: which assets lack the description their type asks for, what each needs, the request for each, and writing the answer. ```luau local Describe = require("@builtin::tools.services.shared.describe") local report = Describe.describe({ mode = "find" }) print(report.calls, report.totalCost) for _, row in ipairs(report.assets) do print(row.asset, row.call) end ``` `Describe.describe(options)` takes `{ mode, scope, assets, instructions, examples }` and answers a report (see the tool's README). What it reads: each type's `described` checks and `describe:` block through `assetType.shared.typeYaml`, the `describing-assets` guide and the `answer-format.md` beside this module (the reply format) that the model follows, and the asset's files. The service that makes the text is `describe`: one operation, one price per call. The assets are packed whole into calls of at most `CALL_BUDGET_BYTES` of request text (and `CALL_MAX_ASSETS` assets), each asset sits in a block carrying an id the tool assigns, and the model answers one JSON object per line keyed by those ids, which the tool reads line by line so that one bad answer fails one asset.

# 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**.

# image_gen (service) Text-to-image generation via [OpenAI's GPT Image 2](https://platform.openai.com/docs/guides/images). A `.service` asset — a plain Luau module, resolvable as `@builtin::services.image_gen`, exposing a generator that runs through the credit-metered service path. ## Operations - `generate({ prompt, size?, quality?, quiet? })`: text-to-image. `size` is a `WIDTHxHEIGHT` in pixels (`'1024x1024'`, `'1536x1024'`, `'1024x1536'`, `'2560x1440'`, ...) with both edges multiples of 16, neither edge over 3840, the long edge at most 3 times the short one and 655360 to 8294400 pixels in all, or `'auto'` (what an unset size does) to let the model choose from the prompt; `quality` is `'low'`, `'medium'`, `'high'` or `'auto'` (what an unset quality does). Any other value is refused at the call, naming what the input takes. The image comes back inline as base64 and is written under `/zero/source/generated/images/`. By default the raw PNG is imported into a spawnable `.texture` asset; pass `quiet = true` to write the raw PNG only, without the import. ## Using it ```luau local image = asset.resolve("image_gen", "service") print(image:cost(), image:balance()) -- budget before spending local g = image:invoke({ prompt = "a mossy stone idol" }) -- Watch the run until it settles; a completed row's `asset` is the finished, -- spawnable `.texture`. local row = tools.use("services", "status", { id = g.id }) while row ~= nil and row.status ~= "completed" and row.status ~= "failed" do task.wait(1) row = tools.use("services", "status", { id = g.id }) end print(row.status, row.asset) ``` The handle's `asset_path` is where the run directs the raw generated file; the asset it becomes is the completed status row's `asset`, which is what to spawn. ## Cost `generate` costs credits (see `:cost()`); the exact amount charged is returned on the generation handle. Check `:balance()` first.

# serviceCall The user-scope entry point for credit-metered service calls. A `.service` handler calls `Service.invoke(offering, endpoint, opts)` instead of touching the `service` primitive directly, getting one `(response, err)` contract with the HTTP status already classified. ```lua local Service = require("modules.serviceCall") local resp, err = Service.invoke("origozero/mesh_gen", "create_preview", { body = { prompt = "a wooden chest" }, }) if not resp then handle:fail(err) -- "out of credits …", "not signed in …", "unknown service …" return end if resp.status >= 300 then -- upstream relayed a non-2xx (charged 0) handle:fail("upstream " .. resp.status) return end local task = resp.body -- the upstream payload ``` `Service.invoke` returns the InvokeResponse `{ status, headers, body, charged, balance }` on a successful round-trip, or `(nil, errMsg)` when the call could not be charged or forwarded. `Service.balance()` returns the caller's integer credit balance. ZeroMind injects the provider secret and meters credits server-side; the platform JWT and the real upstream URL are never visible to this script.

# mesh_gen Generate a 3D mesh (a textured `.glb`) from a text prompt or a reference image. Reach for this when you need a 3D model — a prop, a piece of furniture, a creature — and you only have a description or a picture of it. ## Operations - `generate({ prompt, … })` — text-to-3D. Runs a preview pass then a refine pass, downloads the resulting GLB, and writes it under `/zero/source/generated/meshes/`. Returns a generation handle; the mesh is ready when the handle completes. - `from_image({ image_url? | image?, … })` — image-to-3D. A textured GLB from a reference image: a public `image_url`, or a local `image` VFS path sent as a data URI. - `rig({ asset? | task_id? | model_url?, height_meters? })`: auto-rig a mesh into an animatable, skinned character. Name the mesh in one of three ways, and the result is a rigged GLB ready to drive with any clip. Height defaults to 1.7 m. - `asset`: a mesh this service generated, by the `asset` its completed `generate` / `from_image` row names (the `.bundle`) or by the `asset_path` that run was directed to write (`/zero/source/game/art/x.glb`). The run stamped the provider's id for the mesh on that asset, and `rig` sends it. A mesh this service did not generate carries no such id, and `rig` refuses it before anything is charged, naming the other two forms. - `task_id`: the provider's id for the mesh, the `outputs.task_id` of the job that generated it. - `model_url`: a public URL of a mesh file, for a mesh from anywhere else. - `generate_rigged({ prompt, … })` — text-to-character: generate and rig in one run. The mesh it generates is retopologised to about 50000 polygons before the rigging pass reads it; that pass takes a mesh of at most 320,000 faces. ## Quality Results arrive **game-ready**: PBR-textured at **2k** and retopologised to about **30000 polygons** (**50000** for `generate_rigged`). A scene can hold many of them. The provider's raw output is several hundred thousand to a few million triangles with 4k maps, and one 4k map is 85 MB once the engine holds it, so the denser and sharper results are what you ask for when an asset is seen up close. `:operations()` lists every control with the values it accepts and the default it carries. | Input | What it decides | Default | |---|---|---| | `enable_pbr` | Metallic / roughness / normal maps beside the base colour, so the surface answers the world's lighting instead of rendering as flat painted colour. | `true` | | `texture_resolution` | `2k`, `4k`, `8k`. `4k` costs the same credits as `2k`; each map is four times the size. | `2k` | | `ai_model` | Which generation model runs: `meshy-7.1`, `meshy-7`, `meshy-6`, `meshy-6-lite`, or `latest` to track the newest. | the provider's | | `ultra_mode` | The provider's high-fidelity path: more geometry detail, cleaner silhouette. | off | | `target_polycount` | Retopologise to about this many polygons (100–300000). | `30000`, `50000` on `generate_rigged` | | `topology` | `triangle` or `quad`, chosen during retopology. | the provider's | | `should_remesh` | Retopology on or off. `false` keeps the provider's raw density. | on | | `should_texture` | `from_image` only — `false` returns bare geometry for a material of your own. | `true` | **`target_polycount` is the budget knob.** A lower figure buys a lighter mesh and pays for it in softer detail; a higher one keeps more of the form, up to 300000. `should_remesh = false` skips retopology and returns the provider's raw density, the most detail the run produced, at several hundred thousand triangles or more. **`generate_rigged` defaults to 50000 polygons.** It ends in a rigging pass that takes a mesh of at most 320,000 faces, so every figure in the span can be rigged; `should_remesh = false` on it sends the raw density to that pass, which often exceeds the limit. A value outside what an input accepts is refused before anything is charged, so a mistyped `4K` costs a message rather than a preview pass. A `target_polycount` outside 100–300000 is refused the same way, and `:operations()` publishes the span as `min` / `max` on the input. ```luau local mesh = asset.resolve("mesh_gen", "service") -- Nothing to ask for: a game-ready prop, PBR at 2k, about 30000 polygons. local chest = mesh:invoke({ prompt = "a wooden treasure chest, iron banding, weathered oak" }) -- Spend more only where it is seen close up. local hero = mesh:invoke({ prompt = "a hero's greatsword", texture_resolution = "4k", target_polycount = 120000, ultra_mode = true, }) print(chest.id, hero.id) ``` ## Using it ```luau local mesh = asset.resolve("mesh_gen", "service") print(mesh:cost(), mesh:balance()) -- budget before spending local g = mesh:invoke({ prompt = "a wooden treasure chest" }) -- Generation takes a couple of minutes. Watch the run until it settles; a -- completed row's `asset` is the finished, spawnable `.bundle`. local row = tools.use("services", "status", { id = g.id }) while row ~= nil and row.status ~= "completed" and row.status ~= "failed" do task.wait(5) row = tools.use("services", "status", { id = g.id }) end print(row.status, row.asset) ``` The handle's `asset_path` is where the run directs the raw generated file; the asset it becomes is the completed status row's `asset`, which is what to spawn. ## Cost `:cost()` is what a run spends when it names none of the options that cost extra — 10 credits for `generate` (a preview call and a refine call), 5 for `from_image` and `rig`, 15 for `generate_rigged`. Only `texture_resolution = "8k"` and `ultra_mode = true` cost above that; `enable_pbr` and `4k` are free, and `should_texture = false` on `from_image` costs less. Check `:balance()` first.

# pbr_gen (service) Text-to-PBR material generation via the [GenPBR API](https://genpbr.com/). A `.service` asset — a plain Luau module, resolvable as `@builtin::services.pbr_gen`, exposing generation functions with service-specific inputs/outputs. ## Tools | Function | Input | Output | |----------|-------|--------| | `generate_pbr(args)` | `{ prompt, resolution?, seamless?, maps?, asset_path? }` | ZIP of PBR maps written to `asset_path` (default `/source/generated/materials/<name>.zip`) | `maps` is a comma-separated list of map types (`albedo,normal,roughness,metallic,ao,height`); default is all. Each tool returns `(id, taskId)` immediately and runs in the background; poll with `tools.use("services", "status", { id = id })`. ## Usage ```luau local pbr = require("@builtin::services.pbr_gen") local id = pbr.generate_pbr({ prompt = "weathered oak planks", resolution = 2048 }) -- later / in a poll loop local s = tools.use("services", "status", { id = id }) print(s.status, s.progress) -- "polling", 0.4 … if s.status == "completed" then print("material ZIP at " .. s.asset) end ``` ## Metering (no secret in this code) API calls go through `Service.invoke("origozero/pbr_gen", endpoint, …)` (the `serviceCall` module) → ZeroMind, which resolves the logical endpoint to the real GenPBR target, injects the provider's secret server-side, debits the caller's credits, and forwards. The real upstream URL and the secret never appear in this module. Check credits with `require("@builtin::modules.serviceCall").balance()`. The final ZIP is downloaded from a returned public CDN URL with plain `http.get_bytes` (no credential needed).

# anim_gen (service) Text-to-motion generation via the [Uthana API](https://uthana.com/docs/api/capabilities/text-to-motion) (the async `text-to-motion-3.0` model). A `.service` asset — a plain Luau module, resolvable as `@builtin::services.anim_gen`, exposing a generator that runs through the credit-metered service path. ## Operations - `generate({ prompt, format?, fps? })` — text-to-motion. `format` is `'glb'` (default) or `'fbx'`; `fps` is `24 / 30 / 60` (optional). Submits the job, polls it to completion, downloads the retargetable humanoid clip, and writes it under `/zero/source/generated/animations/`. ## Using it ```luau local anim = asset.resolve("anim_gen", "service") print(anim:cost(), anim:balance()) -- budget before spending local g = anim:invoke({ prompt = "walk forward then wave hello" }) -- Generation is async. Watch the run until it settles; a completed row's -- `asset` is the finished, spawnable clip. local row = tools.use("services", "status", { id = g.id }) while row ~= nil and row.status ~= "completed" and row.status ~= "failed" do task.wait(5) row = tools.use("services", "status", { id = g.id }) end print(row.status, row.asset) ``` The handle's `asset_path` is where the run directs the raw generated file; the asset it becomes is the completed status row's `asset`, which is what to spawn. The clip is a standard humanoid animation, retargetable onto any avatar rig. ## Cost `generate` costs credits (see `:cost()`); the exact amount charged is returned on the generation handle. Check `:balance()` first.

# audio_gen (service) Text-to-audio generation via the [ElevenLabs API](https://elevenlabs.io/docs/api-reference) — speech, sound effects, and music. A `.service` asset — a plain Luau module, resolvable as `@builtin::services.audio_gen`, exposing three generators that run through the credit-metered service path. ## Operations - `speech({ text })` — text-to-speech. Returns spoken audio, read in the offering's reading voice. - `sfx({ prompt, duration? })` — text-to-sound-effect. `duration` is the target length in seconds (optional). Returns a short sound effect. - `music({ prompt, duration?, instrumental? })` — text-to-music. `duration` is the target length in seconds (optional); `instrumental` forces a track with no vocals (optional). Returns a musical track. Those field names are the whole surface: an operation refuses a field it does not declare, by name, before any credit is spent. `:operations()` is the machine-readable form of the list above. ## Speech reads in one voice `speech` renders every line in the same reading voice, and the offering takes no voice selection — so a cast of several characters is separated by what they say and by how their clips are played back, not by picking a speaker per line. Both of those are yours to set: - **Writing and delivery** — vocabulary, sentence length and punctuation move a read further than a voice swap does. - **Playback treatment** — the `Audio` component's `pitch` shifts a speaker up or down; `audio.decode` plus `asset.create("soundClip", …, { pcm, sampleRate, channels })` re-renders a clip, so resampling, band-limiting and a reverb tail are all authorable per character. ## Using it A generation runs in the background: the call hands back a handle straight away, and the audio arrives on the run's status row a few seconds later. ```luau local audio = asset.resolve("audio_gen", "service") print(audio:cost("sfx"), audio:balance()) -- budget before spending local g = audio:invoke({ operation = "sfx", prompt = "a heavy wooden door slamming", duration = 2 }) -- Watch the run until it settles. `status` moves through the run's own stages -- (`submitted`, `writing`, `importing`) to `completed` or `failed`; a completed -- row's `asset` is the finished, spawnable `.soundClip`. local row = tools.use("services", "status", { id = g.id }) while row ~= nil and row.status ~= "completed" and row.status ~= "failed" do task.wait(1) row = tools.use("services", "status", { id = g.id }) end print(row.status, row.asset) ``` `audio_gen` declares no `primary` operation (there are three siblings, not one default) — always pass `operation`. The handle's `asset_path` is where the run directs the raw generated file, not the asset it becomes: the importer turns those bytes into a `.soundClip` container, and that container is what the completed status row names as `asset`. Read the produced asset from the row. The same holds for an `asset_path` you pass: `asset_path = "/zero/source/game/audio/door.mp3"` lands the clip `/zero/source/game/audio/door.soundClip`, and so does `asset_path = "/zero/source/game/audio/door.soundClip"`, which names the clip itself. ## Cost Each operation costs credits (see `:cost(operation)`); the exact amount charged is returned on the generation handle. Check `:balance()` first. A call refused for an input the operation does not declare is refused before the charge, so a wrong field name costs a message rather than a generation.

# describe (service) Writes the descriptions assets are missing: the text a type asks its assets to carry (a README, or the `about.yaml` texts, for the built-in types that ask). One call takes many assets. It reads the instruction and the assets' files it is handed and answers for each asset, in a reply that is written to the path the caller directs. The `services describe` tool is how it is used: it works out what each asset needs, packs the assets into as few calls as fit, and writes each answer into its asset's description file. ## Operation One operation, `complete`, calling the `complete` endpoint of the `origozero/describe` offering. A call costs 1 credit, whatever it carries. It takes two inputs, `instructions` and `content`, and runs a model on the OpenRouter account the offering meters. `content` holds the assets, each in a block that carries an id, and the model answers one JSON object per line, keyed by those ids. The `answer-format.md` file in the tool's module states the format. How many assets a call carries is the caller's to set, and `services describe` keeps each request inside 384 KiB. ## Using it ```luau local describe = asset.resolve("describe", "service") local g = describe:invoke({ instructions = guideText, content = blocksText, asset_path = "/zero/source/tmp/describe/1.txt", }) ``` The reply is the file at `asset_path` once the run reads `completed`. Splitting the assets into calls, reading each answer and writing the text where it belongs is what `services describe` does.

# 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 (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.

# assetType.shared.typeYaml A type's `type.yaml`, parsed. Every block a type declares in its `type.yaml` (`settings:`, `inspector:`) is read through this module, so one file read and one YAML decode serve all of them. ```lua local TypeYaml = require("@builtin::assetTypes.assetType.shared.typeYaml") local folder, identity = TypeYaml.folder("material") -- "/zero/source/libs/@builtin/assetTypes/material.assetType", "@builtin::assetTypes.material" local doc = TypeYaml.of("material") print(doc.suffix) -- ".material" print(doc.inspector.type) -- "inspector.luau" ``` - `TypeYaml.folder(typeName)` resolves the assetType and answers its folder path and identity, or `(nil, nil)` when no such type resolves. - `TypeYaml.of(typeName)` answers the decoded document, or nil when the type does not resolve or its `type.yaml` does not decode to a table. The decode is cached per type and read again whenever the file's content version moves, or the type resolves to a different folder. - `TypeYaml.described(typeName)` lists the files a type's assets must describe: each file its `type.yaml` declares with a `described` content check, with the keys and headings the check names and each key's byte limit. `TypeYaml.PLACEHOLDER` is the marker a template puts where a description is yet to be written. - `TypeYaml.describeBlock(typeName)` answers the `describe:` block of the `type.yaml`: the type's own `guidance` on what a description covers and the identities of `examples` whose descriptions show the shape.

# 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).

# Service (asset type) A **service** generates content you don't have yet — a 3D mesh, an image, a PBR material, a sound effect, a humanoid animation, a navigable splat world — from the inputs each operation declares, landing it as an asset in your world. When nothing in `asset.list` fits what you're building, a service is where new content comes from. A `<name>.service/` is a **declaration**, not code. The asset type ships the whole runtime — the metered invoke, the submit → poll → download → write pipeline, the async generation handle, error handling — in its `shared.module/`. An instance only declares its surface: which provider **offering** it meters, and the **operations** it offers. There is no HTTP, polling, credit, or secret code in a service. ## Using a service Every service is used the same way, whatever it generates: ```luau local mesh = asset.resolve("mesh_gen", "service") mesh:operations() -- callable operations, each with its inputs + credit cost mesh:cost() -- credits the next run costs (estimate) mesh:balance() -- credits you have local g = mesh:invoke({ prompt = "a wooden treasure chest" }) --> { id, task, asset_path, operation } -- async: the run is still going local row = tools.use("services", "status", { id = g.id }) -- poll until it settles -- once row.status == "completed", row.asset is the spawnable asset ``` `:invoke` returns immediately with a handle; the run finishes in the background. The `services` toolbox (`status`, `jobs`) is the agent-facing way to track a run to completion, and a completed row's `asset` is the asset to spawn — see the generating-assets-and-content guide. The handle's `asset_path` is where the run directs the raw generated file, which the importer turns into the asset that row names. A run outlives the engine that started it. The gateway keeps the job and its result for hours after the charge, and the run keeps its own record in the world — what it was asked for, the job doing the work, and the step it had reached — so when the world next loads, every run that did not finish is picked up where it left off and lands its asset the way an uninterrupted run does. Nothing is submitted, or paid for, a second time, and nothing is asked of the caller. A service with several operations selects via `input.operation` (`mesh:invoke({ operation = "from_image", image = "/zero/source/.../ref.png" })`); a single-operation service just takes its input. ## Authoring one ```luau -- <name>.service/init.luau local Service = asset.containing(__FILE__).modules.shared return Service.define({ name = "<name>", description = "Generate <thing> from a text prompt.", offering = "<provider>/<name>", -- the offering ZeroMind meters output = { kind = "mesh", ext = "glb", dir = "/zero/source/generated/meshes" }, operations = { generate = { description = "What this makes, agent-facing.", input = { prompt = { type = "string", required = true } }, cost = 5, steps = { … }, -- the pipeline (see below) result = { url = "$url" }, -- the framework downloads + writes it }, }, }) ``` An operation takes exactly the fields it declares in `input`, plus the `operation`, `asset_path` and `durable` the framework itself reads. A call carrying any other field is refused by name — ahead of the credit pre-flight and ahead of any endpoint — with the fields the operation does take named in the message, so a field the steps have no `$ref` for costs a message rather than a run. An operation that declares no `input` states nothing about its surface and takes any field. An input declaring `enum = { "2k", "4k", "8k" }` accepts those values and no others, and the set is published on the input so a reader learns it from the listing rather than from a refusal. A value outside it is refused with the same timing as an undeclared field — before the credit pre-flight, before any endpoint. That timing is the point where a pipeline spends per step: a value the last step's upstream rejects is one the earlier steps were already charged for. An input declaring `dimensions` takes an image size as a `WIDTHxHEIGHT` string in pixels, inside every bound the declaration states: `multipleOf` (each edge), `maxEdge`, `minPixels` / `maxPixels` (width times height) and `maxAspect` (the long edge over the short one). The words `also` lists (`also = { "auto" }`) are accepted beside a size. It is refused with the same timing for any other value, and the refusal names every bound, so a size the provider would refuse costs a message: ```luau size = { type = "string", dimensions = { multipleOf = 16, maxEdge = 3840, minPixels = 655360, also = { "auto" } }, } ``` A set may hold strings or numbers (`enum = { 24, 30, 60 }`), and a value matches only a member equal to it: the number `30` and the string `'30'` are different values, and the refusal quotes strings and leaves numbers bare so it reads that way. Whenever the provider honours a fixed set of values for an input, the set is its `enum` and the input's `desc` says what the choice does to the result, so the values a reader learns and the values the call accepts are one list. An input declaring `min` / `max` accepts numbers inside that span and is refused with the same timing for a figure outside it. Either bound stands on its own: `min` alone is a floor, `max` alone a ceiling. Both are published on the input beside `enum` and `default`. A span an upstream honours belongs here for the same reason a value set does: a figure the pass that reads it refuses is one every earlier pass has already been paid for. ### Declaring the pipeline `steps` is an ordered list of metered calls. Each step: - `call` — the offering's logical endpoint name. - `body` / `params` / `headers` — templated. `"$name"` injects an input or a prior step's bound value; `"${name}"` interpolates inside a string (a missing value drops the key); `"$name?"` is optional. `{ fromFile = "$path", dataUri = "image/png" }` sends a local asset; `{ firstOf = { a, b } }` uses the first present value; `{ scale = "$n", by = 1000 }` multiplies a number; `{ truncate = "$text", to = 64 }` clamps a string to at most that many characters, for an upstream that caps a field's length; `{ whenSet = "$n", use = true }` sends `use` when `$n` was named and drops the key when it wasn't, for an upstream that reads one field only while a companion flag is on — naming such a field alone is otherwise accepted, charged for, and ignored. - `poll` — when the call submits a job: `{ endpoint, param }` plus optional `idFrom` / `statusFrom` / `done` / `fail` / `doneWhen` / `failWhen` / `progressFrom` overrides (sensible defaults cover the common providers). - `bind` / `bindFrom` — name the value later steps reference; `bindFrom` extracts it (a dotted path, a fallback list `{ "a", "b" }`, or an array-find `{ find = "assets", where = { type = "x" }, get = "url" }`). For a polled step the default bind is the submitted job id. `result` is either `{ url = "$bound" }` (download the URL and write it) or `{ bytes = "$bound" }` (write bytes a step returned directly). `output` sets where the asset lands (`<dir>/<safe(prompt)>.<ext>`); a caller's `asset_path` overrides it. The run writes the file at that path and imports it like any other, so the completed row names the asset the importer produced. A path ending in an asset type's extension (`clips/door.soundClip`) names that asset: the file is written beside it under `output.ext` (`clips/door.mp3`) and imported into it. Two destinations keep the written file as the result: one inside another asset's folder, which is that asset's own content (a `.package` holds assets of their own, so a file inside one imports as usual), and a file no importer claims. The derived name is a truncation of the request, so several runs can derive one name — the same line under two voices, two prompts that open on a shared phrase. The framework hands each run a name no other run holds and no file in `<dir>` already spends, appending `_2`, `_3`, … when it must, and the handle's `asset_path` is the name that run will write. So a set of related generations can run at once and each result is readable at its own path. The written file is then imported, and the name is derived by the rule the importer names an asset with, so the name a run reserves is the name its finished asset carries. Read `mesh_gen` as the worked template: `asset.resolve("mesh_gen","service"):getDefinition()`. ## Discovery - `asset.list("service")` — every registered service. - `asset.resolve("<name>","service"):info()` — offering, output, operations. - `asset.resolve("<name>","service"):operations()` — each operation's inputs + cost. ## Related types - `.module` — reusable library code you `require` and call. - `.tool` — an agent-callable function that composes multiple engine steps. - `.component` — per-entity behaviour. ## In the Inspector Service: what the service does and each operation it offers, with its credit cost and inputs, parsed from its declaration without running it. Invoking an operation spends credits, so it is not offered here.

# 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.

# 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.