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npx skills add vercel-labs/json-render --skill svelte
Svelte 5 renderer for json-render that turns JSON specs into Svelte component trees. Use when working with @json-render/svelte, building Svelte UIs from JSON, creating component catalogs, or rendering AI-generated specs.
npx skills add vercel-labs/json-render --skill svelte
Svelte 5 renderer that converts json-render specs into Svelte component trees.
Components should accept BaseComponentProps<TProps>:
The Svelte schema uses the element tree format:
Use visible on elements to show/hide based on state:
{ "$state": "/path" } - truthy check{ "$state": "/path", "eq": value } - equality check{ "$state": "/path", "not": true } - falsy check{ "$and": [cond1, cond2] } - AND conditions{ "$or": [cond1, cond2] } - OR conditionsJsonUIProvider composes all contexts. Individual contexts:
| Context | Purpose |
|---|---|
StateContext | Share state across components (JSON Pointer paths) |
ActionContext | Handle actions dispatched via the event system |
VisibilityContext | Enable conditional rendering based on state |
ValidationContext | Form field validation |
Components use emit to fire named events. The element's on field maps events to action bindings:
The setState action is handled automatically and updates the state model:
Other built-in actions: pushState, removeState, push, pop.
Nested lists can set repeat.statePath to { "$item": "field" } inside an enclosing repeat.
Expression forms resolved before your component receives props:
{"$state": "/state/key"} - read from state{"$bindState": "/form/email"} - read + write-back to state{"$bindItem": "field"} - read + write-back for repeat items{"$cond": <condition>, "$then": <value>, "$else": <value>} - conditional valueFor writable bindings inside components, use getBoundProp:
Preferred helpers:
getStateValue(path) - returns { current } (read/write)getBoundProp(() => value, () => bindingPath) - returns { current } (read/write when bound)isVisible(condition) - returns { current } (boolean)getAction(name) - returns { current } (registered handler)Advanced context access:
getStateContext()getActionContext()getVisibilityContext()getValidationContext()getOptionalValidationContext()getFieldValidation(ctx, path, config?)Use createUIStream for spec streaming:
Use createChatUI for chat + UI responses:
import { defineCatalog } from "@json-render/core";
import { schema } from "@json-render/svelte";
import { z } from "zod";
export const catalog = defineCatalog(schema, {
components: {
Button: {
props: z.object({
label: z.string(),
variant: z.enum(["primary", "secondary"]).nullable(),
}),
description: "Clickable button",
},
Card: {
props: z.object({ title: z.string() }),
description: "Card container with title",
},
},
});interface BaseComponentProps<TProps> {
props: TProps; // Resolved props for this component
children?: Snippet; // Child elements (use {@render children()})
emit: (event: string) => void; // Fire a named event
bindings?: Record<string, string>; // Map of prop names to state paths (for $bindState)
loading?: boolean; // True while spec is streaming
}<!-- Button.svelte -->
<script lang="ts">
import type { BaseComponentProps } from "@json-render/svelte";
interface Props extends BaseComponentProps<{ label: string; variant?: string }> {}
let { props, emit }: Props = $props();
</script>
<button class={props.variant} onclick={() => emit("press")}>
{props.label}
</button><!-- Card.svelte -->
<script lang="ts">
import type { Snippet } from "svelte";
import type { BaseComponentProps } from "@json-render/svelte";
interface Props extends BaseComponentProps<{ title: string }> {
children?: Snippet;
}
let { props, children }: Props = $props();
</script>
<div class="card">
<h2>{props.title}</h2>
{#if children}
{@render children()}
{/if}
</div>import { defineRegistry } from "@json-render/svelte";
import { catalog } from "./catalog";
import Card from "./components/Card.svelte";
import Button from "./components/Button.svelte";
const { registry, handlers, executeAction } = defineRegistry(catalog, {
components: {
Card,
Button,
},
actions: {
submit: async (params, setState, state) => {
// handle action
},
},
});{
"root": "card1",
"elements": {
"card1": {
"type": "Card",
"props": { "title": "Hello" },
"children": ["btn1"]
},
"btn1": {
"type": "Button",
"props": { "label": "Click me" }
}
}
}<!-- Button.svelte -->
<script lang="ts">
import type { BaseComponentProps } from "@json-render/svelte";
interface Props extends BaseComponentProps<{ label: string }> {}
let { props, emit }: Props = $props();
</script>
<button onclick={() => emit("press")}>{props.label}</button>{
"type": "Button",
"props": { "label": "Submit" },
"on": { "press": { "action": "submit" } }
}{
"action": "setState",
"actionParams": { "statePath": "/activeTab", "value": "home" }
}<script lang="ts">
import { getBoundProp } from "@json-render/svelte";
import type { BaseComponentProps } from "@json-render/svelte";
interface Props extends BaseComponentProps<{ value?: string }> {}
let { props, bindings }: Props = $props();
let value = getBoundProp<string>(
() => props.value,
() => bindings?.value,
);
</script>
<input bind:value={value.current} /><script lang="ts">
import { createUIStream, Renderer } from "@json-render/svelte";
const stream = createUIStream({
api: "/api/generate-ui",
onComplete: (spec) => console.log("Done", spec),
});
async function generate() {
await stream.send("Create a login form");
}
</script>
<button onclick={generate} disabled={stream.isStreaming}>
{stream.isStreaming ? "Generating..." : "Generate UI"}
</button>
{#if stream.spec}
<Renderer spec={stream.spec} {registry} loading={stream.isStreaming} />
{/if}const chat = createChatUI({ api: "/api/chat-ui" });
await chat.send("Build a settings panel");