fixes

* add dynamic forms support: computed values, watchers, cross-field validation

- `$computed` and `$template` prop expressions for derived values and string interpolation
- Element-level `watch` field for cascading state dependencies
- Cross-field validators (`lessThan`, `greaterThan`, `equalTo`, `requiredIf`) with deep arg resolution
- `validateForm` built-in action for form-level validation

* fixes

* fixes

* fixes

* fixes

* fixes

* fixes

* fixes

* tests

* fixes

* update turbo

* tests

* fixes

* fixes

* fixes

.gitignore

@@ -23,6 +23,8 @@ coverage
 
 # Build Outputs
 .next/
+.nuxt/
+.output/
 out/
 build
 dist

README.md

@@ -117,6 +117,7 @@ function Dashboard({ spec }) {
 | `@json-render/redux` | Redux / Redux Toolkit adapter for `StateStore` |
 | `@json-render/zustand` | Zustand adapter for `StateStore` |
 | `@json-render/jotai` | Jotai adapter for `StateStore` |
+| `@json-render/xstate-store` | XState Store (atom) adapter for `StateStore` |
 
 ## Renderers
 

apps/web/CHANGELOG.md

@@ -1,5 +1,14 @@
 # web
 
+## 0.1.2
+
+### Patch Changes
+
+- Updated dependencies [b103676]
+  - @json-render/react@0.9.1
+  - @json-render/core@0.9.1
+  - @json-render/codegen@0.9.1
+
 ## 0.1.1
 
 ### Patch Changes

apps/web/app/(main)/docs/changelog/page.mdx

@@ -5,6 +5,16 @@ export const metadata = pageMetadata("docs/changelog")
 
 Notable changes and updates to json-render.
 
+## v0.9.1
+
+February 2026
+
+### Fixed: Install failure due to private dependency
+
+`@json-render/react`, `@json-render/react-pdf`, and `@json-render/react-native` v0.9.0 failed to install because `@internal/react-state` (a private workspace package) was published as a dependency. The internal package is now bundled into each renderer at build time, so it no longer needs to be resolved from npm.
+
+---
+
 ## v0.9.0
 
 February 2026

apps/web/app/(main)/docs/computed-values/page.mdx

@@ -0,0 +1,119 @@
+import { pageMetadata } from "@/lib/page-metadata"
+export const metadata = pageMetadata("docs/computed-values")
+
+# Computed Values
+
+Derive dynamic prop values using registered functions or string templates.
+
+## `$template` — String Interpolation
+
+Use `{ "$template": "..." }` to embed state values into a string. References use `${/path}` syntax where the path is a JSON Pointer:
+
+```json
+{
+  "type": "Text",
+  "props": {
+    "text": { "$template": "Hello, ${/user/name}! You have ${/inbox/count} messages." }
+  },
+  "children": []
+}
+```
+
+If state is `{ "user": { "name": "Alice" }, "inbox": { "count": 3 } }`, the text renders as "Hello, Alice! You have 3 messages."
+
+Missing paths resolve to an empty string.
+
+## `$computed` — Registered Functions
+
+Use `{ "$computed": "<name>", "args": { ... } }` to call a named function registered in your catalog. Each arg can be a literal value or any prop expression (`$state`, `$item`, `$cond`, etc.):
+
+```json
+{
+  "type": "Text",
+  "props": {
+    "text": {
+      "$computed": "fullName",
+      "args": {
+        "first": { "$state": "/form/firstName" },
+        "last": { "$state": "/form/lastName" }
+      }
+    }
+  },
+  "children": []
+}
+```
+
+### Registering Functions
+
+Functions are registered in the catalog and provided at runtime.
+
+**Catalog definition (for AI prompt generation):**
+
+```typescript
+import { defineCatalog } from '@json-render/core';
+import { schema } from '@json-render/react/schema';
+
+const catalog = defineCatalog(schema, {
+  components: { /* ... */ },
+  functions: {
+    fullName: {
+      description: 'Combines first and last name into a full name',
+    },
+    formatCurrency: {
+      description: 'Formats a number as currency',
+    },
+  },
+});
+```
+
+**Runtime implementation:**
+
+```tsx
+import { JSONUIProvider } from '@json-render/react';
+
+const functions = {
+  fullName: (args) => `${args.first ?? ''} ${args.last ?? ''}`.trim(),
+  formatCurrency: (args) => {
+    const value = Number(args.value ?? 0);
+    return new Intl.NumberFormat('en-US', {
+      style: 'currency',
+      currency: (args.currency as string) ?? 'USD',
+    }).format(value);
+  },
+};
+
+<JSONUIProvider registry={registry} functions={functions}>
+  <Renderer spec={spec} registry={registry} />
+</JSONUIProvider>
+```
+
+### Using with `createRenderer`
+
+```tsx
+const MyRenderer = createRenderer(catalog, components);
+
+<MyRenderer
+  spec={spec}
+  functions={functions}
+/>
+```
+
+## Combining Expressions
+
+`$computed` args can use any expression type. This example computes a total from repeat item fields:
+
+```json
+{
+  "$computed": "lineTotal",
+  "args": {
+    "price": { "$item": "price" },
+    "quantity": { "$item": "quantity" }
+  }
+}
+```
+
+## Next
+
+- [Watchers](/docs/watchers) — react to state changes with cascading actions
+- [Data Binding](/docs/data-binding) — all expression types
+- [Validation](/docs/validation) — validate form inputs

apps/web/app/(main)/docs/data-binding/page.mdx

@@ -213,6 +213,22 @@ Use `$cond` / `$then` / `$else` to pick a prop value based on a condition:
 
 The condition uses the same [visibility](/docs/visibility) expression format.
 
+## Template Strings
+
+Use `{ "$template": "..." }` to interpolate state values into a string using `${/path}` syntax:
+
+```json
+{
+  "type": "Text",
+  "props": {
+    "text": { "$template": "Welcome back, ${/user/name}!" }
+  },
+  "children": []
+}
+```
+
+See [Computed Values](/docs/computed-values) for details on `$template` and `$computed` expressions.
+
 ## Quick Reference
 
 <div className="my-6 overflow-x-auto">
@@ -255,6 +271,16 @@ The condition uses the same [visibility](/docs/visibility) expression format.
         <td><code>{'{ "$bindItem": "field" }'}</code></td>
         <td>Form components inside repeat</td>
       </tr>
+      <tr>
+        <td><code>{"$template"}</code></td>
+        <td><code>{'{ "$template": "Hello, ${/name}!" }'}</code></td>
+        <td>Anywhere (string props)</td>
+      </tr>
+      <tr>
+        <td><code>{"$computed"}</code></td>
+        <td><code>{'{ "$computed": "fn", "args": { ... } }'}</code></td>
+        <td>Anywhere (requires registered function)</td>
+      </tr>
     </tbody>
   </table>
 </div>

apps/web/app/(main)/docs/validation/page.mdx

@@ -11,11 +11,18 @@ json-render includes common validation functions:
 
 - `required` — Value must be non-empty
 - `email` — Valid email format
-- `minLength` — Minimum string length
-- `maxLength` — Maximum string length
-- `pattern` — Match a regex pattern
-- `min` — Minimum numeric value
-- `max` — Maximum numeric value
+- `minLength` — Minimum string length (args: `{ "min": N }`)
+- `maxLength` — Maximum string length (args: `{ "max": N }`)
+- `pattern` — Match a regex pattern (args: `{ "pattern": "regex" }`)
+- `min` — Minimum numeric value (args: `{ "min": N }`)
+- `max` — Maximum numeric value (args: `{ "max": N }`)
+- `numeric` — Value must be a number
+- `url` — Valid URL format
+- `matches` — Must equal another field (args: `{ "other": { "$state": "/path" } }`)
+- `equalTo` — Alias for matches (args: `{ "other": { "$state": "/path" } }`)
+- `lessThan` — Value must be less than another field (args: `{ "other": { "$state": "/path" } }`)
+- `greaterThan` — Value must be greater than another field (args: `{ "other": { "$state": "/path" } }`)
+- `requiredIf` — Required only when another field is truthy (args: `{ "field": { "$state": "/path" } }`)
 
 ## Using Validation in JSON
 
@@ -143,14 +150,114 @@ function TextField({ props, bindings }) {
 
 See the [@json-render/react API reference](/docs/api/react) for full `ValidationProvider` and `useFieldValidation` documentation.
 
+## Cross-Field Validation
+
+Validation args support `{ "$state": "/path" }` references to compare against other fields. This enables cross-field rules like "confirm password must match password":
+
+```json
+{
+  "type": "Input",
+  "props": {
+    "label": "Confirm Password",
+    "value": { "$bindState": "/form/confirmPassword" },
+    "checks": [
+      { "type": "required", "message": "Please confirm your password" },
+      {
+        "type": "matches",
+        "args": { "other": { "$state": "/form/password" } },
+        "message": "Passwords must match"
+      }
+    ]
+  }
+}
+```
+
+Other cross-field examples:
+
+```json
+{
+  "checks": [
+    {
+      "type": "greaterThan",
+      "args": { "other": { "$state": "/form/startDate" } },
+      "message": "End date must be after start date"
+    }
+  ]
+}
+```
+
+```json
+{
+  "checks": [
+    {
+      "type": "requiredIf",
+      "args": { "field": { "$state": "/form/enableNotifications" } },
+      "message": "Email is required when notifications are enabled"
+    }
+  ]
+}
+```
+
+## Conditional Validation
+
+Use the `enabled` field in the validation config to only run checks when a condition is met:
+
+```json
+{
+  "type": "Input",
+  "props": {
+    "label": "Company Name",
+    "value": { "$bindState": "/form/company" },
+    "checks": [
+      { "type": "required", "message": "Company name is required" }
+    ]
+  }
+}
+```
+
+In the component implementation, you can pass `enabled` to `useFieldValidation`:
+
+```typescript
+useFieldValidation(bindings?.value ?? "", {
+  checks: props.checks ?? [],
+  enabled: { "$state": "/form/accountType", eq: "business" },
+});
+```
+
+This only validates the company name when the account type is "business".
+
 ## Validation Timing
 
 Control when validation runs with `validateOn`:
 
 - `change` — Validate on every input change
-- `blur` — Validate when field loses focus
+- `blur` — Validate when field loses focus (default for Input, Textarea)
 - `submit` — Validate only on form submission
 
+## Form-Level Validation
+
+Use the built-in `validateForm` action to validate all registered fields at once. This is useful for a "Submit" button that should validate the entire form before proceeding:
+
+```json
+{
+  "type": "Button",
+  "props": { "label": "Submit" },
+  "on": {
+    "press": [
+      { "action": "validateForm", "params": { "statePath": "/formResult" } },
+      { "action": "submitForm" }
+    ]
+  },
+  "children": []
+}
+```
+
+The `validateForm` action runs `validateAll()` and writes `{ valid: boolean }` to the specified state path (defaults to `/formValidation`). Your submit handler can then check `{ "$state": "/formResult/valid" }` to decide whether to proceed.
+
+> **Note:** Actions in a list execute sequentially, but `submitForm` does not automatically gate on validation. Guard submission with a `$cond` visibility condition on the button or check `{ "$state": "/formResult/valid" }` inside your action handler to skip submission when the form is invalid.
+
 ## Next
 
-Learn about [generation modes](/docs/generation-modes).
+- [Computed Values](/docs/computed-values) — derive dynamic prop values
+- [Watchers](/docs/watchers) — react to state changes
+- [Generation Modes](/docs/generation-modes) — how AI generates specs

apps/web/app/(main)/docs/watchers/page.mdx

@@ -0,0 +1,150 @@
+import { pageMetadata } from "@/lib/page-metadata"
+export const metadata = pageMetadata("docs/watchers")
+
+# Watchers
+
+React to state changes by triggering actions when watched paths update.
+
+## The `watch` Field
+
+Elements can have an optional `watch` field that maps state paths to action bindings. When the value at a watched path changes, the bound actions fire automatically.
+
+`watch` is a **top-level field** on the element (sibling of `type`, `props`, `children`) — not inside `props`.
+
+```json
+{
+  "type": "Select",
+  "props": {
+    "label": "Country",
+    "value": { "$bindState": "/form/country" },
+    "options": ["US", "Canada", "UK"]
+  },
+  "watch": {
+    "/form/country": {
+      "action": "loadCities",
+      "params": { "country": { "$state": "/form/country" } }
+    }
+  },
+  "children": []
+}
+```
+
+When the user selects a different country, the `loadCities` action fires with the new country value. The action handler can fetch city data and update state, causing a dependent city Select to re-render with new options.
+
+## Cascading Selects
+
+A common pattern is cascading dropdowns where selecting a value in one field loads options for another:
+
+```json
+{
+  "root": "form",
+  "elements": {
+    "form": {
+      "type": "Stack",
+      "props": { "direction": "vertical", "gap": "md" },
+      "children": ["country-select", "city-select"]
+    },
+    "country-select": {
+      "type": "Select",
+      "props": {
+        "label": "Country",
+        "value": { "$bindState": "/form/country" },
+        "options": ["US", "Canada", "UK"]
+      },
+      "watch": {
+        "/form/country": [
+          { "action": "loadCities", "params": { "country": { "$state": "/form/country" } } },
+          { "action": "setState", "params": { "statePath": "/form/city", "value": "" } }
+        ]
+      },
+      "children": []
+    },
+    "city-select": {
+      "type": "Select",
+      "props": {
+        "label": "City",
+        "value": { "$bindState": "/form/city" },
+        "options": { "$state": "/availableCities" },
+        "placeholder": "Select a city"
+      },
+      "children": []
+    }
+  },
+  "state": {
+    "form": { "country": "", "city": "" },
+    "availableCities": []
+  }
+}
+```
+
+The watcher on `country-select` fires two actions when the country changes:
+1. `loadCities` — fetches and writes city options to `/availableCities`
+2. `setState` — resets the city selection
+
+The city Select reads its options from `{ "$state": "/availableCities" }`, so it automatically updates when the data is loaded.
+
+### Action Handler
+
+```typescript
+const handlers = {
+  loadCities: async (params) => {
+    const cities = await fetchCities(params.country);
+    // setState is called by the runtime to write the result
+    return cities;
+  },
+};
+```
+
+Or with `defineRegistry`:
+
+```typescript
+const { registry, handlers } = defineRegistry(catalog, {
+  components: { /* ... */ },
+  actions: {
+    loadCities: async (params, setState) => {
+      const response = await fetch(`/api/cities?country=${params.country}`);
+      const cities = await response.json();
+      setState('/availableCities', cities);
+    },
+  },
+});
+```
+
+## Multiple Watchers
+
+An element can watch multiple state paths. Each path maps to one or more action bindings:
+
+```json
+{
+  "watch": {
+    "/form/startDate": { "action": "validateDateRange" },
+    "/form/endDate": { "action": "validateDateRange" },
+    "/form/quantity": [
+      { "action": "recalculateTotal" },
+      { "action": "checkInventory", "params": { "qty": { "$state": "/form/quantity" } } }
+    ]
+  }
+}
+```
+
+## Behavior
+
+- Watchers only fire on **value changes**, not on the initial render
+- Comparison is by reference (`===`), not deep equality
+- Action params support the same expressions as event bindings (`$state`, `$item`, `$index`)
+- Multiple action bindings on the same path execute sequentially
+
+## When to Use `watch` vs `on`
+
+| Mechanism | Trigger | Use Case |
+|-----------|---------|----------|
+| `on` | User interaction (press, change, blur) | Button clicks, input changes, form submissions |
+| `watch` | State value change (any source) | Cascading data, derived state, cross-field sync |
+
+Use `on` when reacting to direct user actions. Use `watch` when a state change (from any source — user input, action handler, or external store update) should trigger side effects.
+
+## Next
+
+- [Data Binding](/docs/data-binding) — connect elements to state
+- [Computed Values](/docs/computed-values) — derive prop values
+- [Visibility](/docs/visibility) — conditionally show or hide elements

apps/web/lib/docs-navigation.ts

@@ -27,7 +27,9 @@ export const docsNavigation: NavSection[] = [
       { title: "Schemas", href: "/docs/schemas" },
       { title: "Catalog", href: "/docs/catalog" },
       { title: "Data Binding", href: "/docs/data-binding" },
+      { title: "Computed Values", href: "/docs/computed-values" },
       { title: "Visibility", href: "/docs/visibility" },
+      { title: "Watchers", href: "/docs/watchers" },
       { title: "Validation", href: "/docs/validation" },
     ],
   },

apps/web/package.json

@@ -1,6 +1,6 @@
 {
   "name": "web",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "type": "module",
   "private": true,
   "license": "Apache-2.0",

examples/chat/CHANGELOG.md

@@ -1,5 +1,14 @@
 # example-chat
 
+## 0.1.2
+
+### Patch Changes
+
+- Updated dependencies [b103676]
+  - @json-render/react@0.9.1
+  - @json-render/shadcn@0.9.1
+  - @json-render/core@0.9.1
+
 ## 0.1.1
 
 ### Patch Changes

examples/chat/package.json

@@ -1,6 +1,6 @@
 {
   "name": "example-chat",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "type": "module",
   "private": true,
   "scripts": {

examples/dashboard/CHANGELOG.md

@@ -1,5 +1,14 @@
 # example-dashboard
 
+## 0.1.2
+
+### Patch Changes
+
+- Updated dependencies [b103676]
+  - @json-render/react@0.9.1
+  - @json-render/core@0.9.1
+  - @json-render/codegen@0.9.1
+
 ## 0.1.1
 
 ### Patch Changes

examples/dashboard/package.json

@@ -1,6 +1,6 @@
 {
   "name": "example-dashboard",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "type": "module",
   "private": true,
   "scripts": {

examples/no-ai/CHANGELOG.md

@@ -1,5 +1,14 @@
 # example-no-ai
 
+## 0.1.2
+
+### Patch Changes
+
+- Updated dependencies [b103676]
+  - @json-render/react@0.9.1
+  - @json-render/shadcn@0.9.1
+  - @json-render/core@0.9.1
+
 ## 0.1.1
 
 ### Patch Changes

examples/no-ai/app/page.tsx

@@ -2,33 +2,31 @@
 
 import { useState, useEffect, useCallback, type ReactNode } from "react";
 import ConfettiExplosion from "react-confetti-explosion";
-import {
-  Renderer,
-  StateProvider,
-  VisibilityProvider,
-  ActionProvider,
-  ValidationProvider,
-} from "@json-render/react";
+import { JSONUIProvider, Renderer } from "@json-render/react";
 import type { Spec } from "@json-render/core";
-import { registry, actionHandlers, onConfetti } from "@/lib/render/registry";
+import {
+  registry,
+  actionHandlers,
+  computedFunctions,
+  onConfetti,
+} from "@/lib/render/registry";
 import { examples } from "@/lib/examples";
 
 function SpecRenderer({ spec }: { spec: Spec }): ReactNode {
   return (
-    <StateProvider initialState={spec.state ?? {}}>
-      <VisibilityProvider>
-        <ActionProvider handlers={actionHandlers}>
-          <ValidationProvider>
-            <Renderer spec={spec} registry={registry} />
-          </ValidationProvider>
-        </ActionProvider>
-      </VisibilityProvider>
-    </StateProvider>
+    <JSONUIProvider
+      registry={registry}
+      initialState={spec.state ?? {}}
+      handlers={actionHandlers}
+      functions={computedFunctions}
+    >
+      <Renderer spec={spec} registry={registry} />
+    </JSONUIProvider>
   );
 }
 
 export default function Page() {
-  const [selectedIndex] = useState(0);
+  const [selectedIndex, setSelectedIndex] = useState(0);
   const selected = examples[selectedIndex]!;
   const [confettiKey, setConfettiKey] = useState(0);
   const [confettiActive, setConfettiActive] = useState(false);
@@ -41,30 +39,50 @@ export default function Page() {
   useEffect(() => onConfetti(fireConfetti), [fireConfetti]);
 
   return (
-    <div className="h-screen flex items-center justify-center bg-muted/30">
-      <div
-        className="relative bg-background border rounded-lg shadow-sm"
-        style={{ width: 960, height: 1080 }}
-      >
-        {confettiActive && (
-          <div className="absolute inset-0 flex items-center justify-center pointer-events-none">
-            <ConfettiExplosion
-              key={confettiKey}
-              portal={false}
-              force={0.8}
-              duration={3500}
-              particleCount={400}
-              particleSize={8}
-              colors={["#00F0FF", "#7B61FF", "#FF3DFF", "#00FF94", "#FFE14D"]}
-              width={1600}
-              height="200vh"
-              zIndex={1}
-              onComplete={() => setConfettiActive(false)}
-            />
+    <div className="h-screen flex flex-col bg-muted/30">
+      {/* Example selector */}
+      <nav className="flex gap-1 p-3 overflow-x-auto border-b bg-background shrink-0">
+        {examples.map((ex, i) => (
+          <button
+            key={ex.name}
+            onClick={() => setSelectedIndex(i)}
+            className={`px-3 py-1.5 text-sm rounded-md whitespace-nowrap transition-colors ${
+              i === selectedIndex
+                ? "bg-primary text-primary-foreground"
+                : "hover:bg-muted"
+            }`}
+          >
+            {ex.name}
+          </button>
+        ))}
+      </nav>
+
+      {/* Render area */}
+      <div className="flex-1 flex items-start justify-center overflow-auto p-6">
+        <div className="relative bg-background border rounded-lg shadow-sm w-full max-w-[960px]">
+          {confettiActive && (
+            <div className="absolute inset-0 flex items-center justify-center pointer-events-none">
+              <ConfettiExplosion
+                key={confettiKey}
+                portal={false}
+                force={0.8}
+                duration={3500}
+                particleCount={400}
+                particleSize={8}
+                colors={["#00F0FF", "#7B61FF", "#FF3DFF", "#00FF94", "#FFE14D"]}
+                width={1600}
+                height="200vh"
+                zIndex={1}
+                onComplete={() => setConfettiActive(false)}
+              />
+            </div>
+          )}
+          <div className="p-6 relative z-10">
+            <p className="text-xs text-muted-foreground mb-4">
+              {selected.description}
+            </p>
+            <SpecRenderer key={selectedIndex} spec={selected.spec} />
           </div>
-        )}
-        <div className="h-full overflow-auto p-6 flex items-center justify-center relative z-10">
-          <SpecRenderer key={selectedIndex} spec={selected.spec} />
         </div>
       </div>
     </div>

examples/no-ai/lib/examples.ts

@@ -508,4 +508,353 @@ export const examples: Example[] = [
       },
     },
   },
+
+  // =========================================================================
+  // Advanced: Registration form with cross-field validation & $template
+  // =========================================================================
+  {
+    name: "Registration Form",
+    description:
+      "Cross-field validation, $template preview, and validateForm action",
+    spec: {
+      root: "card",
+      state: {
+        form: {
+          name: "",
+          email: "",
+          password: "",
+          confirmPassword: "",
+          accountType: "personal",
+          company: "",
+        },
+        result: null,
+      },
+      elements: {
+        card: {
+          type: "Card",
+          props: {
+            title: "Create Account",
+            description: "Fill out the form below to register",
+            maxWidth: "md",
+            centered: null,
+          },
+          children: ["formStack"],
+        },
+        formStack: {
+          type: "Stack",
+          props: {
+            direction: "vertical",
+            gap: "md",
+            align: null,
+            justify: null,
+          },
+          children: [
+            "preview",
+            "sep0",
+            "nameInput",
+            "emailInput",
+            "passwordInput",
+            "confirmInput",
+            "sep1",
+            "accountTypeRadio",
+            "companyInput",
+            "sep2",
+            "actions",
+            "statusText",
+          ],
+        },
+
+        // $template live preview
+        preview: {
+          type: "Text",
+          props: {
+            text: {
+              $template: "Welcome, ${/form/name}! Your email: ${/form/email}",
+            },
+            variant: "muted",
+          },
+          visible: { $state: "/form/name", neq: "" },
+          children: [],
+        },
+        sep0: { type: "Separator", props: { orientation: null }, children: [] },
+
+        nameInput: {
+          type: "Input",
+          props: {
+            label: "Full Name",
+            name: "name",
+            type: "text",
+            placeholder: "Jane Doe",
+            value: { $bindState: "/form/name" },
+            checks: [
+              { type: "required", message: "Name is required" },
+              {
+                type: "minLength",
+                args: { min: 2 },
+                message: "Name must be at least 2 characters",
+              },
+            ],
+            validateOn: "blur",
+          },
+          children: [],
+        },
+        emailInput: {
+          type: "Input",
+          props: {
+            label: "Email",
+            name: "email",
+            type: "email",
+            placeholder: "jane@example.com",
+            value: { $bindState: "/form/email" },
+            checks: [
+              { type: "required", message: "Email is required" },
+              { type: "email", message: "Enter a valid email address" },
+            ],
+            validateOn: "blur",
+          },
+          children: [],
+        },
+        passwordInput: {
+          type: "Input",
+          props: {
+            label: "Password",
+            name: "password",
+            type: "password",
+            placeholder: "At least 8 characters",
+            value: { $bindState: "/form/password" },
+            checks: [
+              { type: "required", message: "Password is required" },
+              {
+                type: "minLength",
+                args: { min: 8 },
+                message: "Password must be at least 8 characters",
+              },
+            ],
+            validateOn: "blur",
+          },
+          children: [],
+        },
+        confirmInput: {
+          type: "Input",
+          props: {
+            label: "Confirm Password",
+            name: "confirmPassword",
+            type: "password",
+            placeholder: "Re-enter your password",
+            value: { $bindState: "/form/confirmPassword" },
+            checks: [
+              { type: "required", message: "Please confirm your password" },
+              {
+                type: "matches",
+                args: { other: { $state: "/form/password" } },
+                message: "Passwords must match",
+              },
+            ],
+            validateOn: "blur",
+          },
+          children: [],
+        },
+        sep1: { type: "Separator", props: { orientation: null }, children: [] },
+
+        accountTypeRadio: {
+          type: "Radio",
+          props: {
+            label: "Account Type",
+            name: "accountType",
+            options: ["personal", "business"],
+            value: { $bindState: "/form/accountType" },
+            checks: null,
+            validateOn: null,
+          },
+          children: [],
+        },
+        companyInput: {
+          type: "Input",
+          props: {
+            label: "Company Name",
+            name: "company",
+            type: "text",
+            placeholder: "Acme Inc.",
+            value: { $bindState: "/form/company" },
+            checks: [
+              {
+                type: "requiredIf",
+                args: { field: { $state: "/form/accountType" } },
+                message: "Company name is required for business accounts",
+              },
+            ],
+            validateOn: "blur",
+          },
+          visible: { $state: "/form/accountType", eq: "business" },
+          children: [],
+        },
+        sep2: { type: "Separator", props: { orientation: null }, children: [] },
+
+        actions: {
+          type: "Stack",
+          props: {
+            direction: "horizontal",
+            gap: "sm",
+            align: null,
+            justify: "end",
+          },
+          children: ["submitBtn"],
+        },
+        submitBtn: {
+          type: "Button",
+          props: { label: "Register", variant: "primary", disabled: null },
+          on: {
+            press: [
+              {
+                action: "validateForm",
+                params: { statePath: "/result" },
+              },
+            ],
+          },
+          children: [],
+        },
+
+        // Validation result
+        statusText: {
+          type: "Alert",
+          props: {
+            title: "Validation Result",
+            message: {
+              $cond: { $state: "/result/valid", eq: true },
+              $then: "All fields are valid -- ready to submit!",
+              $else: "Please fix the errors above before submitting.",
+            },
+            type: {
+              $cond: { $state: "/result/valid", eq: true },
+              $then: "success",
+              $else: "error",
+            },
+          },
+          visible: { $state: "/result", neq: null },
+          children: [],
+        },
+      },
+    },
+  },
+
+  // =========================================================================
+  // Advanced: Cascading selects with watchers & $computed
+  // =========================================================================
+  {
+    name: "Cascading Selects",
+    description:
+      "Watchers reset dependent fields, $computed derives display values",
+    spec: {
+      root: "card",
+      state: {
+        form: { country: "", city: "" },
+        availableCities: [],
+      },
+      elements: {
+        card: {
+          type: "Card",
+          props: {
+            title: "Shipping Address",
+            description: "Select your country to load available cities",
+            maxWidth: "md",
+            centered: null,
+          },
+          children: ["formStack"],
+        },
+        formStack: {
+          type: "Stack",
+          props: {
+            direction: "vertical",
+            gap: "md",
+            align: null,
+            justify: null,
+          },
+          children: [
+            "countrySelect",
+            "citySelect",
+            "sep",
+            "addressPreview",
+            "templatePreview",
+          ],
+        },
+
+        countrySelect: {
+          type: "Select",
+          props: {
+            label: "Country",
+            name: "country",
+            options: ["US", "Canada", "UK", "Germany", "Japan"],
+            placeholder: "Choose a country",
+            value: { $bindState: "/form/country" },
+            checks: [{ type: "required", message: "Country is required" }],
+            validateOn: "change",
+          },
+          watch: {
+            "/form/country": [
+              {
+                action: "setState",
+                params: {
+                  statePath: "/availableCities",
+                  value: {
+                    $computed: "citiesForCountry",
+                    args: { country: { $state: "/form/country" } },
+                  },
+                },
+              },
+              {
+                action: "setState",
+                params: { statePath: "/form/city", value: "" },
+              },
+            ],
+          },
+          children: [],
+        },
+
+        citySelect: {
+          type: "Select",
+          props: {
+            label: "City",
+            name: "city",
+            options: { $state: "/availableCities" },
+            placeholder: "Select a city",
+            value: { $bindState: "/form/city" },
+            checks: [{ type: "required", message: "City is required" }],
+            validateOn: "change",
+          },
+          children: [],
+        },
+        sep: { type: "Separator", props: { orientation: null }, children: [] },
+
+        // $computed formatted address
+        addressPreview: {
+          type: "Heading",
+          props: {
+            text: {
+              $computed: "formatAddress",
+              args: {
+                city: { $state: "/form/city" },
+                country: { $state: "/form/country" },
+              },
+            },
+            level: "h3",
+          },
+          children: [],
+        },
+
+        // $template string interpolation
+        templatePreview: {
+          type: "Text",
+          props: {
+            text: {
+              $template:
+                "Shipping to: ${/form/city} in ${/form/country}. Cities available: ${/availableCities}",
+            },
+            variant: "muted",
+          },
+          visible: { $state: "/form/country", neq: "" },
+          children: [],
+        },
+      },
+    },
+  },
 ];

examples/no-ai/lib/render/catalog.ts

@@ -13,4 +13,13 @@ export const catalog = defineCatalog(schema, {
       description: "Fire confetti",
     },
   },
+  functions: {
+    formatAddress: {
+      description:
+        "Formats country and city into a single address string like 'City, Country'",
+    },
+    citiesForCountry: {
+      description: "Returns an array of city names for the given country code",
+    },
+  },
 });

examples/no-ai/lib/render/registry.tsx

@@ -1,6 +1,7 @@
 "use client";
 
 import { defineRegistry } from "@json-render/react";
+import type { ComputedFunction } from "@json-render/core";
 import { shadcnComponents } from "@json-render/shadcn";
 import { catalog } from "./catalog";
 
@@ -13,6 +14,14 @@ export function onConfetti(cb: () => void) {
   };
 }
 
+const cityData: Record<string, string[]> = {
+  US: ["New York", "Los Angeles", "Chicago", "Houston", "Phoenix"],
+  Canada: ["Toronto", "Vancouver", "Montreal", "Calgary", "Ottawa"],
+  UK: ["London", "Manchester", "Birmingham", "Edinburgh", "Bristol"],
+  Germany: ["Berlin", "Munich", "Hamburg", "Frankfurt", "Cologne"],
+  Japan: ["Tokyo", "Osaka", "Kyoto", "Yokohama", "Sapporo"],
+};
+
 export const { registry } = defineRegistry(catalog, {
   components: {
     ...shadcnComponents,
@@ -24,6 +33,23 @@ export const { registry } = defineRegistry(catalog, {
   },
 });
 
-export const actionHandlers: Record<string, () => void> = {
+export const actionHandlers: Record<
+  string,
+  (params: Record<string, unknown>) => void
+> = {
   confetti: () => confettiListener?.(),
 };
+
+export const computedFunctions: Record<string, ComputedFunction> = {
+  formatAddress: (args) => {
+    const city = (args.city as string) ?? "";
+    const country = (args.country as string) ?? "";
+    if (!city && !country) return "No location selected";
+    if (!city) return country;
+    return `${city}, ${country}`;
+  },
+  citiesForCountry: (args) => {
+    const country = (args.country as string) ?? "";
+    return cityData[country] ?? [];
+  },
+};

examples/no-ai/package.json

@@ -1,6 +1,6 @@
 {
   "name": "example-no-ai",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "type": "module",
   "private": true,
   "scripts": {

examples/nuxt/app.vue

@@ -0,0 +1,5 @@
+<template>
+  <div id="app">
+    <NuxtPage />
+  </div>
+</template>

examples/nuxt/assets/css/main.css

@@ -0,0 +1 @@
+@import "tailwindcss";

examples/nuxt/lib/examples.ts

@@ -0,0 +1,399 @@
+import type { Spec } from "@json-render/core";
+
+export interface Example {
+  name: string;
+  description: string;
+  spec: Spec;
+}
+
+export const examples: Example[] = [
+  {
+    name: "User Profile Card",
+    description: "A card with user info, badges, and a progress bar",
+    spec: {
+      root: "card",
+      elements: {
+        card: {
+          type: "Card",
+          props: {
+            title: "User Profile",
+            description: null,
+            maxWidth: "md",
+            centered: null,
+          },
+          children: ["stack"],
+        },
+        stack: {
+          type: "Stack",
+          props: {
+            direction: "vertical",
+            gap: "md",
+            align: null,
+            justify: null,
+          },
+          children: ["heading", "text", "badges", "sep", "progress"],
+        },
+        heading: {
+          type: "Heading",
+          props: { text: "Jane Cooper", level: "h2" },
+        },
+        text: {
+          type: "Text",
+          props: {
+            text: "Senior software engineer based in San Francisco. Passionate about building accessible, high-performance web applications.",
+            variant: "muted",
+          },
+        },
+        badges: {
+          type: "Stack",
+          props: {
+            direction: "horizontal",
+            gap: "sm",
+            align: null,
+            justify: null,
+          },
+          children: ["b1", "b2", "b3"],
+        },
+        b1: {
+          type: "Badge",
+          props: { text: "TypeScript", variant: "default" },
+        },
+        b2: { type: "Badge", props: { text: "Vue", variant: "secondary" } },
+        b3: { type: "Badge", props: { text: "Node.js", variant: "outline" } },
+        sep: { type: "Separator", props: { orientation: null } },
+        progress: {
+          type: "Progress",
+          props: { value: 72, max: 100, label: "Profile completion" },
+        },
+      },
+    },
+  },
+
+  {
+    name: "Settings Form",
+    description: "A form with inputs, selects, and switches",
+    spec: {
+      root: "card",
+      state: {
+        name: "Ada Lovelace",
+        email: "ada@example.com",
+        role: "Engineer",
+        notifications: true,
+        darkMode: false,
+      },
+      elements: {
+        card: {
+          type: "Card",
+          props: {
+            title: "Account Settings",
+            description: "Manage your preferences",
+            maxWidth: "md",
+            centered: null,
+          },
+          children: ["form"],
+        },
+        form: {
+          type: "Stack",
+          props: {
+            direction: "vertical",
+            gap: "md",
+            align: null,
+            justify: null,
+          },
+          children: [
+            "nameInput",
+            "emailInput",
+            "roleSelect",
+            "sep",
+            "notifSwitch",
+            "darkSwitch",
+            "sep2",
+            "actions",
+          ],
+        },
+        nameInput: {
+          type: "Input",
+          props: {
+            label: "Full Name",
+            name: "name",
+            type: "text",
+            placeholder: "Your name",
+            value: { $bindState: "/name" },
+            checks: null,
+          },
+        },
+        emailInput: {
+          type: "Input",
+          props: {
+            label: "Email",
+            name: "email",
+            type: "email",
+            placeholder: "you@example.com",
+            value: { $bindState: "/email" },
+            checks: null,
+          },
+        },
+        roleSelect: {
+          type: "Select",
+          props: {
+            label: "Role",
+            name: "role",
+            options: [
+              "Engineer",
+              "Designer",
+              "Product Manager",
+              "Data Scientist",
+            ],
+            placeholder: "Choose a role",
+            value: { $bindState: "/role" },
+            checks: null,
+          },
+        },
+        sep: { type: "Separator", props: { orientation: null } },
+        notifSwitch: {
+          type: "Switch",
+          props: {
+            label: "Email notifications",
+            name: "notifications",
+            checked: { $bindState: "/notifications" },
+          },
+        },
+        darkSwitch: {
+          type: "Switch",
+          props: {
+            label: "Dark mode",
+            name: "darkMode",
+            checked: { $bindState: "/darkMode" },
+          },
+        },
+        sep2: { type: "Separator", props: { orientation: null } },
+        actions: {
+          type: "Stack",
+          props: {
+            direction: "horizontal",
+            gap: "sm",
+            align: null,
+            justify: "end",
+          },
+          children: ["cancelBtn", "saveBtn"],
+        },
+        cancelBtn: {
+          type: "Button",
+          props: { label: "Cancel", variant: "secondary", disabled: null },
+        },
+        saveBtn: {
+          type: "Button",
+          props: { label: "Save Changes", variant: "primary", disabled: null },
+        },
+      },
+    },
+  },
+
+  {
+    name: "Pricing Table",
+    description: "A grid of pricing cards with feature lists",
+    spec: {
+      root: "outer",
+      elements: {
+        outer: {
+          type: "Stack",
+          props: {
+            direction: "vertical",
+            gap: "lg",
+            align: null,
+            justify: null,
+          },
+          children: ["header", "grid"],
+        },
+        header: {
+          type: "Stack",
+          props: {
+            direction: "vertical",
+            gap: "sm",
+            align: "center",
+            justify: null,
+          },
+          children: ["title", "subtitle"],
+        },
+        title: {
+          type: "Heading",
+          props: { text: "Simple, transparent pricing", level: "h1" },
+        },
+        subtitle: {
+          type: "Text",
+          props: {
+            text: "Choose the plan that fits your needs. Upgrade or downgrade at any time.",
+            variant: "muted",
+          },
+        },
+        grid: {
+          type: "Grid",
+          props: { columns: 3, gap: "md" },
+          children: ["free", "pro", "enterprise"],
+        },
+        free: {
+          type: "Card",
+          props: { title: "Free", description: "$0/month" },
+          children: ["freeContent"],
+        },
+        freeContent: {
+          type: "Stack",
+          props: { direction: "vertical", gap: "sm" },
+          children: ["f1", "f2", "f3", "freeBtn"],
+        },
+        f1: {
+          type: "Text",
+          props: { text: "Up to 3 projects", variant: "body" },
+        },
+        f2: { type: "Text", props: { text: "1 GB storage", variant: "body" } },
+        f3: {
+          type: "Text",
+          props: { text: "Community support", variant: "body" },
+        },
+        freeBtn: {
+          type: "Button",
+          props: { label: "Get Started", variant: "secondary" },
+        },
+        pro: {
+          type: "Card",
+          props: { title: "Pro", description: "$19/month" },
+          children: ["proContent"],
+        },
+        proContent: {
+          type: "Stack",
+          props: { direction: "vertical", gap: "sm" },
+          children: ["p1", "p2", "p3", "p4", "proBtn"],
+        },
+        p1: {
+          type: "Text",
+          props: { text: "Unlimited projects", variant: "body" },
+        },
+        p2: { type: "Text", props: { text: "50 GB storage", variant: "body" } },
+        p3: {
+          type: "Text",
+          props: { text: "Priority support", variant: "body" },
+        },
+        p4: {
+          type: "Text",
+          props: { text: "Custom domains", variant: "body" },
+        },
+        proBtn: {
+          type: "Button",
+          props: { label: "Upgrade to Pro", variant: "primary" },
+        },
+        enterprise: {
+          type: "Card",
+          props: { title: "Enterprise", description: "Custom pricing" },
+          children: ["entContent"],
+        },
+        entContent: {
+          type: "Stack",
+          props: { direction: "vertical", gap: "sm" },
+          children: ["e1", "e2", "e3", "e4", "entBtn"],
+        },
+        e1: {
+          type: "Text",
+          props: { text: "Everything in Pro", variant: "body" },
+        },
+        e2: {
+          type: "Text",
+          props: { text: "Unlimited storage", variant: "body" },
+        },
+        e3: {
+          type: "Text",
+          props: { text: "Dedicated support", variant: "body" },
+        },
+        e4: {
+          type: "Text",
+          props: { text: "SLA guarantees", variant: "body" },
+        },
+        entBtn: {
+          type: "Button",
+          props: { label: "Contact Sales", variant: "secondary" },
+        },
+      },
+    },
+  },
+
+  {
+    name: "Status Dashboard",
+    description: "System status with alerts, a table, and an accordion",
+    spec: {
+      root: "root",
+      elements: {
+        root: {
+          type: "Stack",
+          props: { direction: "vertical", gap: "lg" },
+          children: [
+            "heading",
+            "alertOk",
+            "alertWarn",
+            "sep",
+            "table",
+            "sep2",
+            "accordion",
+          ],
+        },
+        heading: {
+          type: "Heading",
+          props: { text: "System Status", level: "h1" },
+        },
+        alertOk: {
+          type: "Alert",
+          props: {
+            title: "API",
+            message: "All systems operational -- 99.98% uptime this month",
+            type: "success",
+          },
+        },
+        alertWarn: {
+          type: "Alert",
+          props: {
+            title: "Database",
+            message: "Elevated latency detected in us-east-1 region",
+            type: "warning",
+          },
+        },
+        sep: { type: "Separator", props: { orientation: null } },
+        table: {
+          type: "Table",
+          props: {
+            columns: ["Service", "Status", "Latency", "Uptime"],
+            rows: [
+              ["API Gateway", "Operational", "12ms", "99.99%"],
+              ["Auth Service", "Operational", "8ms", "99.98%"],
+              ["Database", "Degraded", "145ms", "99.85%"],
+              ["CDN", "Operational", "3ms", "100%"],
+              ["Workers", "Operational", "22ms", "99.97%"],
+            ],
+            caption: "Last updated 2 minutes ago",
+          },
+        },
+        sep2: { type: "Separator", props: { orientation: null } },
+        accordion: {
+          type: "Accordion",
+          props: {
+            items: [
+              {
+                title: "What does 'Degraded' mean?",
+                content:
+                  "The service is still operational but experiencing slower response times than normal. We are actively investigating.",
+              },
+              {
+                title: "How is uptime calculated?",
+                content:
+                  "Uptime is measured over the current calendar month based on successful health-check pings every 30 seconds.",
+              },
+              {
+                title: "How do I subscribe to updates?",
+                content:
+                  "You can subscribe to incident notifications via email or webhook on the Settings page.",
+              },
+            ],
+            type: "single",
+          },
+        },
+      },
+    },
+  },
+];

examples/nuxt/lib/render/catalog.ts

@@ -0,0 +1,173 @@
+import { defineCatalog } from "@json-render/core";
+import { schema } from "@json-render/vue/schema";
+import { z } from "zod";
+
+export const catalog = defineCatalog(schema, {
+  components: {
+    Card: {
+      props: z.object({
+        title: z.string().optional(),
+        description: z.string().nullable().optional(),
+        maxWidth: z.enum(["sm", "md", "lg", "xl"]).nullable().optional(),
+        centered: z.boolean().nullable().optional(),
+      }),
+      slots: ["default"],
+      description: "A card container with optional title and description",
+    },
+    Stack: {
+      props: z.object({
+        direction: z.enum(["horizontal", "vertical"]).optional(),
+        gap: z.enum(["sm", "md", "lg"]).optional(),
+        align: z
+          .enum(["start", "center", "end", "stretch"])
+          .nullable()
+          .optional(),
+        justify: z
+          .enum(["start", "center", "end", "between", "around"])
+          .nullable()
+          .optional(),
+      }),
+      slots: ["default"],
+      description:
+        "Flex container for laying out children horizontally or vertically",
+    },
+    Grid: {
+      props: z.object({
+        columns: z.number().optional(),
+        gap: z.enum(["sm", "md", "lg"]).optional(),
+      }),
+      slots: ["default"],
+      description: "Grid layout container",
+    },
+    Heading: {
+      props: z.object({
+        text: z.string(),
+        level: z.enum(["h1", "h2", "h3", "h4"]).optional(),
+      }),
+      slots: [],
+      description: "Heading text element",
+    },
+    Text: {
+      props: z.object({
+        text: z.string(),
+        variant: z.enum(["body", "muted", "bold"]).optional(),
+      }),
+      slots: [],
+      description: "Text paragraph element",
+    },
+    Button: {
+      props: z.object({
+        label: z.string(),
+        variant: z
+          .enum(["primary", "secondary", "outline", "danger"])
+          .optional(),
+        disabled: z.boolean().nullable().optional(),
+      }),
+      slots: [],
+      description: "Clickable button. Emits 'press' event.",
+    },
+    Input: {
+      props: z.object({
+        label: z.string().optional(),
+        name: z.string(),
+        type: z.enum(["text", "email", "password", "number"]).optional(),
+        placeholder: z.string().optional(),
+        value: z.string().optional(),
+        checks: z.any().nullable().optional(),
+        validateOn: z.string().nullable().optional(),
+      }),
+      slots: [],
+      description:
+        "Text input field with optional label. Emits 'change' event.",
+    },
+    Select: {
+      props: z.object({
+        label: z.string().optional(),
+        name: z.string(),
+        options: z.array(z.string()),
+        placeholder: z.string().optional(),
+        value: z.string().optional(),
+        checks: z.any().nullable().optional(),
+        validateOn: z.string().nullable().optional(),
+      }),
+      slots: [],
+      description: "Dropdown select field. Emits 'change' event.",
+    },
+    Switch: {
+      props: z.object({
+        label: z.string(),
+        name: z.string(),
+        checked: z.boolean().optional(),
+      }),
+      slots: [],
+      description: "Toggle switch. Emits 'change' event.",
+    },
+    Badge: {
+      props: z.object({
+        text: z.string(),
+        variant: z
+          .enum(["default", "secondary", "outline", "destructive"])
+          .optional(),
+      }),
+      slots: [],
+      description: "Small status badge label",
+    },
+    Separator: {
+      props: z.object({
+        orientation: z.enum(["horizontal", "vertical"]).nullable().optional(),
+      }),
+      slots: [],
+      description: "Visual separator line",
+    },
+    Progress: {
+      props: z.object({
+        value: z.number(),
+        max: z.number().optional(),
+        label: z.string().optional(),
+      }),
+      slots: [],
+      description: "Progress bar",
+    },
+    Alert: {
+      props: z.object({
+        title: z.string(),
+        message: z.string(),
+        type: z.enum(["info", "success", "warning", "error"]).optional(),
+      }),
+      slots: [],
+      description: "Alert / notification banner",
+    },
+    Table: {
+      props: z.object({
+        columns: z.array(z.string()),
+        rows: z.array(z.array(z.string())),
+        caption: z.string().optional(),
+      }),
+      slots: [],
+      description: "Data table with columns and rows",
+    },
+    Accordion: {
+      props: z.object({
+        items: z.array(z.object({ title: z.string(), content: z.string() })),
+        type: z.enum(["single", "multiple"]).optional(),
+      }),
+      slots: [],
+      description: "Collapsible accordion sections",
+    },
+    Radio: {
+      props: z.object({
+        label: z.string().optional(),
+        name: z.string(),
+        options: z.array(z.string()),
+        value: z.string().optional(),
+        checks: z.any().nullable().optional(),
+        validateOn: z.string().nullable().optional(),
+      }),
+      slots: [],
+      description: "Radio button group. Emits 'change' event.",
+    },
+  },
+  actions: {},
+  // Cast needed: zod schema types don't align with the inferred catalog input
+  // type from defineCatalog's generics when no actions are defined.
+} as any);

examples/nuxt/lib/render/registry.ts

@@ -0,0 +1,593 @@
+import { h, ref, defineComponent, type VNode, type PropType } from "vue";
+import {
+  defineRegistry,
+  useBoundProp,
+  useFieldValidation,
+  type BaseComponentProps,
+} from "@json-render/vue";
+import { catalog } from "./catalog";
+
+type Ctx<P = Record<string, unknown>> = BaseComponentProps<P>;
+
+export const { registry } = defineRegistry(catalog, {
+  components: {
+    Card: ({
+      props,
+      children,
+    }: Ctx<{
+      title?: string;
+      description?: string | null;
+      maxWidth?: "sm" | "md" | "lg" | "xl" | null;
+      centered?: boolean | null;
+    }>) => {
+      const maxWidthClass =
+        props.maxWidth === "sm"
+          ? "max-w-sm"
+          : props.maxWidth === "md"
+            ? "max-w-md"
+            : props.maxWidth === "lg"
+              ? "max-w-lg"
+              : props.maxWidth === "xl"
+                ? "max-w-xl"
+                : "";
+      return h(
+        "div",
+        {
+          class: [
+            "rounded-lg border bg-white shadow-sm p-6",
+            maxWidthClass,
+            props.centered ? "mx-auto" : "",
+          ]
+            .filter(Boolean)
+            .join(" "),
+        },
+        [
+          props.title &&
+            h("h3", { class: "text-lg font-semibold" }, props.title),
+          props.description &&
+            h("p", { class: "text-sm text-gray-500 mt-1" }, props.description),
+          (props.title || props.description) &&
+            h("div", { class: "mt-4" }, children),
+          !(props.title || props.description) && children,
+        ].filter(Boolean) as VNode[],
+      );
+    },
+
+    Stack: ({
+      props,
+      children,
+    }: Ctx<{
+      direction?: "horizontal" | "vertical";
+      gap?: "sm" | "md" | "lg";
+      align?: "start" | "center" | "end" | "stretch" | null;
+      justify?: "start" | "center" | "end" | "between" | "around" | null;
+    }>) => {
+      const gapClass =
+        props.gap === "sm" ? "gap-2" : props.gap === "lg" ? "gap-6" : "gap-4";
+      const dirClass =
+        props.direction === "horizontal" ? "flex-row" : "flex-col";
+      const alignMap: Record<string, string> = {
+        start: "items-start",
+        center: "items-center",
+        end: "items-end",
+        stretch: "items-stretch",
+      };
+      const justifyMap: Record<string, string> = {
+        start: "justify-start",
+        center: "justify-center",
+        end: "justify-end",
+        between: "justify-between",
+        around: "justify-around",
+      };
+      const alignClass = props.align ? (alignMap[props.align] ?? "") : "";
+      const justifyClass = props.justify
+        ? (justifyMap[props.justify] ?? "")
+        : "";
+      return h(
+        "div",
+        {
+          class: ["flex", dirClass, gapClass, alignClass, justifyClass]
+            .filter(Boolean)
+            .join(" "),
+        },
+        children,
+      );
+    },
+
+    Grid: ({
+      props,
+      children,
+    }: Ctx<{ columns?: number; gap?: "sm" | "md" | "lg" }>) => {
+      const cols = props.columns ?? 3;
+      const gapClass =
+        props.gap === "sm" ? "gap-2" : props.gap === "lg" ? "gap-6" : "gap-4";
+      const colClass =
+        cols === 1
+          ? "grid-cols-1"
+          : cols === 2
+            ? "grid-cols-2"
+            : cols === 3
+              ? "grid-cols-3"
+              : cols === 4
+                ? "grid-cols-4"
+                : `grid-cols-${cols}`;
+      return h("div", { class: `grid ${colClass} ${gapClass}` }, children);
+    },
+
+    Heading: ({
+      props,
+    }: Ctx<{ text: string; level?: "h1" | "h2" | "h3" | "h4" }>) => {
+      const tag = props.level ?? "h2";
+      const sizeClass =
+        tag === "h1"
+          ? "text-3xl font-bold"
+          : tag === "h2"
+            ? "text-2xl font-semibold"
+            : tag === "h3"
+              ? "text-xl font-semibold"
+              : "text-lg font-medium";
+      return h(tag, { class: sizeClass }, props.text);
+    },
+
+    Text: ({
+      props,
+    }: Ctx<{ text: string; variant?: "body" | "muted" | "bold" }>) => {
+      const variantClass =
+        props.variant === "muted"
+          ? "text-gray-500"
+          : props.variant === "bold"
+            ? "font-semibold"
+            : "";
+      return h("p", { class: variantClass }, props.text);
+    },
+
+    Button: ({
+      props,
+      emit,
+    }: Ctx<{
+      label: string;
+      variant?: "primary" | "secondary" | "outline" | "danger";
+      disabled?: boolean | null;
+    }>) => {
+      const baseClass =
+        "inline-flex items-center justify-center rounded-md px-4 py-2 text-sm font-medium transition-colors focus:outline-none focus:ring-2 focus:ring-offset-2 disabled:opacity-50 disabled:pointer-events-none";
+      const variantClass =
+        props.variant === "primary"
+          ? "bg-blue-600 text-white hover:bg-blue-700 focus:ring-blue-500"
+          : props.variant === "danger"
+            ? "bg-red-600 text-white hover:bg-red-700 focus:ring-red-500"
+            : props.variant === "outline"
+              ? "border border-gray-300 bg-white text-gray-700 hover:bg-gray-50"
+              : "bg-gray-100 text-gray-900 hover:bg-gray-200 focus:ring-gray-500";
+      return h(
+        "button",
+        {
+          class: `${baseClass} ${variantClass}`,
+          disabled: props.disabled ?? false,
+          onClick: () => emit("press"),
+        },
+        props.label,
+      );
+    },
+
+    Input: ({
+      props,
+      bindings,
+      emit,
+    }: Ctx<{
+      label?: string;
+      name: string;
+      type?: string;
+      placeholder?: string;
+      value?: string;
+      checks?: unknown;
+      validateOn?: string | null;
+    }>) => {
+      const [value, setValue] = useBoundProp<string>(
+        props.value,
+        bindings?.value,
+      );
+      const validation = props.checks
+        ? useFieldValidation(`/${props.name}`, {
+            checks: props.checks as any[],
+            validateOn: (props.validateOn as "blur" | "change") ?? undefined,
+          })
+        : null;
+
+      return h(
+        "div",
+        { class: "flex flex-col gap-1.5" },
+        [
+          props.label &&
+            h(
+              "label",
+              { class: "text-sm font-medium text-gray-700" },
+              props.label,
+            ),
+          h("input", {
+            type: props.type ?? "text",
+            placeholder: props.placeholder,
+            value: value ?? "",
+            class:
+              "rounded-md border border-gray-300 px-3 py-2 text-sm shadow-sm focus:border-blue-500 focus:outline-none focus:ring-1 focus:ring-blue-500",
+            onInput: (e: Event) => {
+              const val = (e.target as HTMLInputElement).value;
+              setValue(val);
+              emit("change");
+              if (validation && props.validateOn === "change") {
+                validation.validate();
+              }
+            },
+            onBlur: () => {
+              if (validation && props.validateOn === "blur") {
+                validation.touch();
+                validation.validate();
+              }
+            },
+          }),
+          validation &&
+            validation.errors.value.length > 0 &&
+            h(
+              "p",
+              { class: "text-xs text-red-500" },
+              validation.errors.value[0],
+            ),
+        ].filter(Boolean) as VNode[],
+      );
+    },
+
+    Select: ({
+      props,
+      bindings,
+      emit,
+    }: Ctx<{
+      label?: string;
+      name: string;
+      options: string[];
+      placeholder?: string;
+      value?: string;
+      checks?: unknown;
+      validateOn?: string | null;
+    }>) => {
+      const [value, setValue] = useBoundProp<string>(
+        props.value,
+        bindings?.value,
+      );
+      const options = props.options ?? [];
+      const validation = props.checks
+        ? useFieldValidation(`/${props.name}`, {
+            checks: props.checks as any[],
+            validateOn: (props.validateOn as "blur" | "change") ?? undefined,
+          })
+        : null;
+
+      return h(
+        "div",
+        { class: "flex flex-col gap-1.5" },
+        [
+          props.label &&
+            h(
+              "label",
+              { class: "text-sm font-medium text-gray-700" },
+              props.label,
+            ),
+          h(
+            "select",
+            {
+              value: value ?? "",
+              class:
+                "rounded-md border border-gray-300 px-3 py-2 text-sm shadow-sm focus:border-blue-500 focus:outline-none focus:ring-1 focus:ring-blue-500",
+              onChange: (e: Event) => {
+                const val = (e.target as HTMLSelectElement).value;
+                setValue(val);
+                emit("change");
+                if (validation && props.validateOn === "change") {
+                  validation.validate();
+                }
+              },
+            },
+            [
+              props.placeholder &&
+                h("option", { value: "", disabled: true }, props.placeholder),
+              ...options.map((opt: string) =>
+                h("option", { value: opt, key: opt }, opt),
+              ),
+            ].filter(Boolean) as VNode[],
+          ),
+          validation &&
+            validation.errors.value.length > 0 &&
+            h(
+              "p",
+              { class: "text-xs text-red-500" },
+              validation.errors.value[0],
+            ),
+        ].filter(Boolean) as VNode[],
+      );
+    },
+
+    Switch: ({
+      props,
+      bindings,
+      emit,
+    }: Ctx<{ label: string; name: string; checked?: boolean }>) => {
+      const [checked, setChecked] = useBoundProp<boolean>(
+        props.checked,
+        bindings?.checked,
+      );
+      const isOn = checked ?? false;
+      return h("label", { class: "flex items-center gap-3 cursor-pointer" }, [
+        h(
+          "button",
+          {
+            role: "switch",
+            "aria-checked": isOn,
+            class: [
+              "relative inline-flex h-6 w-11 items-center rounded-full transition-colors",
+              isOn ? "bg-blue-600" : "bg-gray-200",
+            ].join(" "),
+            onClick: () => {
+              setChecked(!isOn);
+              emit("change");
+            },
+          },
+          h("span", {
+            class: [
+              "inline-block h-4 w-4 transform rounded-full bg-white transition-transform",
+              isOn ? "translate-x-6" : "translate-x-1",
+            ].join(" "),
+          }),
+        ),
+        h("span", { class: "text-sm" }, props.label),
+      ]);
+    },
+
+    Badge: ({
+      props,
+    }: Ctx<{
+      text: string;
+      variant?: "default" | "secondary" | "outline" | "destructive";
+    }>) => {
+      const variantClass =
+        props.variant === "secondary"
+          ? "bg-gray-100 text-gray-800"
+          : props.variant === "outline"
+            ? "border border-gray-300 text-gray-700"
+            : props.variant === "destructive"
+              ? "bg-red-100 text-red-800"
+              : "bg-blue-100 text-blue-800";
+      return h(
+        "span",
+        {
+          class: `inline-flex items-center rounded-full px-2.5 py-0.5 text-xs font-medium ${variantClass}`,
+        },
+        props.text,
+      );
+    },
+
+    Separator: () => {
+      return h("hr", { class: "border-gray-200" });
+    },
+
+    Progress: ({
+      props,
+    }: Ctx<{ value: number; max?: number; label?: string }>) => {
+      const pct = Math.min(
+        100,
+        Math.round((props.value / (props.max ?? 100)) * 100),
+      );
+      return h(
+        "div",
+        { class: "flex flex-col gap-1.5" },
+        [
+          props.label &&
+            h("div", { class: "flex justify-between text-sm" }, [
+              h("span", { class: "text-gray-600" }, props.label),
+              h("span", { class: "font-medium" }, `${pct}%`),
+            ]),
+          h(
+            "div",
+            {
+              class: "h-2 w-full rounded-full bg-gray-200 overflow-hidden",
+            },
+            h("div", {
+              class: "h-full rounded-full bg-blue-600 transition-all",
+              style: { width: `${pct}%` },
+            }),
+          ),
+        ].filter(Boolean) as VNode[],
+      );
+    },
+
+    Alert: ({
+      props,
+    }: Ctx<{
+      title: string;
+      message: string;
+      type?: "info" | "success" | "warning" | "error";
+    }>) => {
+      const typeClasses: Record<string, string> = {
+        success: "bg-green-50 border-green-200 text-green-800",
+        warning: "bg-yellow-50 border-yellow-200 text-yellow-800",
+        error: "bg-red-50 border-red-200 text-red-800",
+        info: "bg-blue-50 border-blue-200 text-blue-800",
+      };
+      const cls = typeClasses[props.type ?? "info"] ?? typeClasses.info;
+      return h("div", { class: `rounded-md border p-4 ${cls}` }, [
+        h("p", { class: "text-sm font-medium" }, props.title),
+        h("p", { class: "text-sm mt-1 opacity-80" }, props.message),
+      ]);
+    },
+
+    Table: ({
+      props,
+    }: Ctx<{
+      columns: string[];
+      rows: string[][];
+      caption?: string;
+    }>) => {
+      return h(
+        "div",
+        { class: "overflow-x-auto" },
+        [
+          h("table", { class: "min-w-full text-sm" }, [
+            h(
+              "thead",
+              null,
+              h(
+                "tr",
+                { class: "border-b" },
+                props.columns.map((col: string) =>
+                  h(
+                    "th",
+                    {
+                      key: col,
+                      class: "px-4 py-2 text-left font-medium text-gray-500",
+                    },
+                    col,
+                  ),
+                ),
+              ),
+            ),
+            h(
+              "tbody",
+              null,
+              props.rows.map((row: string[], i: number) =>
+                h(
+                  "tr",
+                  { key: i, class: "border-b last:border-0" },
+                  row.map((cell: string, j: number) =>
+                    h("td", { key: j, class: "px-4 py-2 text-gray-700" }, cell),
+                  ),
+                ),
+              ),
+            ),
+          ]),
+          props.caption &&
+            h("p", { class: "text-xs text-gray-400 mt-2 px-4" }, props.caption),
+        ].filter(Boolean) as VNode[],
+      );
+    },
+
+    // Uses defineComponent instead of a plain render function because it
+    // needs local reactive state (openItems ref) to track expanded items.
+    Accordion: defineComponent({
+      props: {
+        props: {
+          type: Object as PropType<{
+            items: Array<{ title: string; content: string }>;
+            type?: "single" | "multiple";
+          }>,
+          required: true,
+        },
+      },
+      setup(compProps) {
+        const openItems = ref<Set<number>>(new Set());
+
+        const toggle = (idx: number) => {
+          const next = new Set(openItems.value);
+          if (next.has(idx)) {
+            next.delete(idx);
+          } else {
+            if (compProps.props.type === "single") next.clear();
+            next.add(idx);
+          }
+          openItems.value = next;
+        };
+
+        return () =>
+          h(
+            "div",
+            { class: "divide-y border rounded-md" },
+            compProps.props.items.map(
+              (item: { title: string; content: string }, i: number) =>
+                h("div", { key: i }, [
+                  h(
+                    "button",
+                    {
+                      class:
+                        "flex w-full items-center justify-between px-4 py-3 text-sm font-medium text-left hover:bg-gray-50 transition-colors",
+                      onClick: () => toggle(i),
+                    },
+                    [
+                      h("span", null, item.title),
+                      h(
+                        "span",
+                        {
+                          class: [
+                            "transform transition-transform text-gray-400",
+                            openItems.value.has(i) ? "rotate-180" : "",
+                          ].join(" "),
+                        },
+                        "\u25BE",
+                      ),
+                    ],
+                  ),
+                  openItems.value.has(i) &&
+                    h(
+                      "div",
+                      { class: "px-4 pb-3 text-sm text-gray-600" },
+                      item.content,
+                    ),
+                ]),
+            ),
+          );
+      },
+    }) as any,
+
+    Radio: ({
+      props,
+      bindings,
+      emit,
+    }: Ctx<{
+      label?: string;
+      name: string;
+      options: string[];
+      value?: string;
+    }>) => {
+      const [value, setValue] = useBoundProp<string>(
+        props.value,
+        bindings?.value,
+      );
+
+      return h(
+        "div",
+        { class: "flex flex-col gap-1.5" },
+        [
+          props.label &&
+            h(
+              "label",
+              { class: "text-sm font-medium text-gray-700" },
+              props.label,
+            ),
+          h(
+            "div",
+            { class: "flex gap-4" },
+            (props.options ?? []).map((opt: string) =>
+              h(
+                "label",
+                {
+                  key: opt,
+                  class: "flex items-center gap-2 cursor-pointer",
+                },
+                [
+                  h("input", {
+                    type: "radio",
+                    name: props.name,
+                    value: opt,
+                    checked: value === opt,
+                    class: "accent-blue-600",
+                    onChange: () => {
+                      setValue(opt);
+                      emit("change");
+                    },
+                  }),
+                  h("span", { class: "text-sm" }, opt),
+                ],
+              ),
+            ),
+          ),
+        ].filter(Boolean) as VNode[],
+      );
+    },
+  },
+});

examples/nuxt/nuxt.config.ts

@@ -0,0 +1,10 @@
+import tailwindcss from "@tailwindcss/vite";
+
+export default defineNuxtConfig({
+  compatibilityDate: "2025-11-01",
+  css: ["~/assets/css/main.css"],
+  vite: {
+    // Tailwind's Vite plugin types don't align with Nuxt's plugin types
+    plugins: [tailwindcss() as any],
+  },
+});

examples/nuxt/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "example-nuxt",
+  "version": "0.1.0",
+  "type": "module",
+  "private": true,
+  "scripts": {
+    "dev": "portless nuxt-demo.json-render nuxt dev",
+    "build": "nuxt build",
+    "generate": "nuxt generate",
+    "preview": "nuxt preview",
+    "check-types": "nuxt typecheck"
+  },
+  "dependencies": {
+    "@json-render/core": "workspace:*",
+    "@json-render/vue": "workspace:*",
+    "nuxt": "^4.3.1",
+    "vue": "^3.5.29",
+    "zod": "^4.3.6"
+  },
+  "devDependencies": {
+    "@tailwindcss/vite": "^4.2.1",
+    "tailwindcss": "^4.2.1",
+    "typescript": "^5.7.2"
+  }
+}

examples/nuxt/pages/index.vue

@@ -0,0 +1,47 @@
+<script setup lang="ts">
+import { JSONUIProvider, Renderer } from "@json-render/vue";
+import { registry } from "~/lib/render/registry";
+import { examples } from "~/lib/examples";
+
+const selectedIndex = ref(0);
+const selected = computed(() => examples[selectedIndex.value]!);
+</script>
+
+<template>
+  <div class="min-h-screen flex flex-col bg-gray-50">
+    <!-- Example selector -->
+    <nav class="flex gap-1 p-3 overflow-x-auto border-b bg-white shrink-0">
+      <button
+        v-for="(ex, i) in examples"
+        :key="ex.name"
+        class="px-3 py-1.5 text-sm rounded-md whitespace-nowrap transition-colors"
+        :class="
+          i === selectedIndex
+            ? 'bg-blue-600 text-white'
+            : 'hover:bg-gray-100 text-gray-700'
+        "
+        @click="selectedIndex = i"
+      >
+        {{ ex.name }}
+      </button>
+    </nav>
+
+    <!-- Render area -->
+    <div class="flex-1 flex items-start justify-center overflow-auto p-6">
+      <div
+        class="bg-white border rounded-lg shadow-sm w-full max-w-[960px] p-6"
+      >
+        <p class="text-xs text-gray-400 mb-4">
+          {{ selected.description }}
+        </p>
+        <JSONUIProvider
+          :key="selectedIndex"
+          :registry="registry"
+          :initial-state="selected.spec.state ?? {}"
+        >
+          <Renderer :spec="selected.spec" :registry="registry" />
+        </JSONUIProvider>
+      </div>
+    </div>
+  </div>
+</template>

examples/nuxt/tsconfig.json

@@ -0,0 +1,3 @@
+{
+  "extends": "./.nuxt/tsconfig.json"
+}

examples/react-native/CHANGELOG.md

@@ -1,5 +1,13 @@
 # example-react-native
 
+## 0.1.2
+
+### Patch Changes
+
+- Updated dependencies [b103676]
+  - @json-render/react-native@0.9.1
+  - @json-render/core@0.9.1
+
 ## 0.1.1
 
 ### Patch Changes

examples/react-native/package.json

@@ -1,6 +1,6 @@
 {
   "name": "example-react-native",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "private": true,
   "main": "expo-router/entry",
   "scripts": {

examples/react-pdf/CHANGELOG.md

@@ -1,5 +1,13 @@
 # example-react-pdf
 
+## 0.1.2
+
+### Patch Changes
+
+- Updated dependencies [b103676]
+  - @json-render/react-pdf@0.9.1
+  - @json-render/core@0.9.1
+
 ## 0.1.1
 
 ### Patch Changes

examples/react-pdf/package.json

@@ -1,6 +1,6 @@
 {
   "name": "example-react-pdf",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "type": "module",
   "private": true,
   "scripts": {

examples/remotion/CHANGELOG.md

@@ -1,5 +1,12 @@
 # example-remotion
 
+## 0.1.2
+
+### Patch Changes
+
+- @json-render/core@0.9.1
+- @json-render/remotion@0.9.1
+
 ## 0.1.1
 
 ### Patch Changes

examples/remotion/package.json

@@ -1,6 +1,6 @@
 {
   "name": "example-remotion",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "type": "module",
   "private": true,
   "scripts": {

examples/stripe-app/drawer-app/CHANGELOG.md

@@ -1,5 +1,13 @@
 # com.example.json-render-demo
 
+## 0.0.3
+
+### Patch Changes
+
+- Updated dependencies [b103676]
+  - @json-render/react@0.9.1
+  - @json-render/core@0.9.1
+
 ## 0.0.2
 
 ### Patch Changes

examples/stripe-app/drawer-app/package.json

@@ -1,6 +1,6 @@
 {
   "name": "com.example.json-render-demo",
-  "version": "0.0.2",
+  "version": "0.0.3",
   "description": "Test",
   "private": true,
   "license": "~~proprietary~~",

examples/stripe-app/fullpage-app/CHANGELOG.md

@@ -1,5 +1,13 @@
 # com.example.json-render-fullpage-demo
 
+## 0.0.3
+
+### Patch Changes
+
+- Updated dependencies [b103676]
+  - @json-render/react@0.9.1
+  - @json-render/core@0.9.1
+
 ## 0.0.2
 
 ### Patch Changes

examples/stripe-app/fullpage-app/package.json

@@ -1,6 +1,6 @@
 {
   "name": "com.example.json-render-fullpage-demo",
-  "version": "0.0.2",
+  "version": "0.0.3",
   "description": "Full-page Stripe App example (alpha)",
   "private": true,
   "license": "~~proprietary~~",

package.json

@@ -12,7 +12,7 @@
   },
   "scripts": {
     "build": "turbo run build",
-    "dev": "turbo run dev --concurrency 15",
+    "dev": "turbo run dev --concurrency 20",
     "lint": "turbo run lint",
     "format": "prettier --write \"**/*.{ts,tsx}\"",
     "type-check": "turbo run check-types",
@@ -30,6 +30,7 @@
     "@changesets/cli": "2.29.8",
     "@testing-library/dom": "^10.4.1",
     "@testing-library/react": "^16.3.1",
+    "@testing-library/vue": "^8.1.0",
     "@types/react": "^19.2.3",
     "husky": "^9.1.7",
     "jsdom": "^27.4.0",
@@ -39,6 +40,7 @@
     "react-dom": "^19.2.4",
     "turbo": "^2.7.4",
     "typescript": "5.9.2",
+    "vue": "^3.5.29",
     "vitest": "^4.0.17"
   },
   "packageManager": "pnpm@10.29.3",

packages/codegen/CHANGELOG.md

@@ -1,5 +1,11 @@
 # @json-render/codegen
 
+## 0.9.1
+
+### Patch Changes
+
+- @json-render/core@0.9.1
+
 ## 0.9.0
 
 ### Minor Changes

packages/codegen/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@json-render/codegen",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "license": "Apache-2.0",
   "description": "Utilities for generating code from json-render UI trees",
   "keywords": [

packages/core/CHANGELOG.md

@@ -1,5 +1,7 @@
 # @json-render/core
 
+## 0.9.1
+
 ## 0.9.0
 
 ### Minor Changes

packages/core/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@json-render/core",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "license": "Apache-2.0",
   "description": "JSON becomes real things. Define your catalog, register your components, let AI generate.",
   "keywords": [

packages/core/src/index.ts

@@ -72,7 +72,11 @@ export {
 } from "./visibility";
 
 // Prop Expressions
-export type { PropExpression, PropResolutionContext } from "./props";
+export type {
+  PropExpression,
+  PropResolutionContext,
+  ComputedFunction,
+} from "./props";
 
 export {
   resolvePropValue,

packages/core/src/props.test.ts

@@ -1,9 +1,11 @@
-import { describe, it, expect } from "vitest";
+import { describe, it, expect, vi } from "vitest";
 import {
   resolvePropValue,
   resolveElementProps,
   resolveBindings,
   resolveActionParam,
+  _resetWarnedComputedFns,
+  _resetWarnedTemplatePaths,
 } from "./props";
 import type { PropResolutionContext } from "./props";
 
@@ -498,3 +500,165 @@ describe("resolveActionParam", () => {
     expect(resolveActionParam(null, ctx)).toBeNull();
   });
 });
+
+// =============================================================================
+// $computed expressions
+// =============================================================================
+
+describe("$computed expressions", () => {
+  it("calls a registered function with resolved args", () => {
+    const ctx: PropResolutionContext = {
+      stateModel: { form: { firstName: "Jane", lastName: "Doe" } },
+      functions: {
+        fullName: (args) => `${args.first} ${args.last}`,
+      },
+    };
+    expect(
+      resolvePropValue(
+        {
+          $computed: "fullName",
+          args: {
+            first: { $state: "/form/firstName" },
+            last: { $state: "/form/lastName" },
+          },
+        },
+        ctx,
+      ),
+    ).toBe("Jane Doe");
+  });
+
+  it("calls function with no args", () => {
+    const ctx: PropResolutionContext = {
+      stateModel: {},
+      functions: {
+        timestamp: () => 1234567890,
+      },
+    };
+    expect(resolvePropValue({ $computed: "timestamp" }, ctx)).toBe(1234567890);
+  });
+
+  it("returns undefined for unknown function", () => {
+    const ctx: PropResolutionContext = {
+      stateModel: {},
+      functions: {},
+    };
+    expect(resolvePropValue({ $computed: "unknown" }, ctx)).toBeUndefined();
+  });
+
+  it("returns undefined when no functions in context", () => {
+    const ctx: PropResolutionContext = { stateModel: {} };
+    expect(resolvePropValue({ $computed: "any" }, ctx)).toBeUndefined();
+  });
+
+  it("deduplicates warnings for the same unknown function", () => {
+    const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+    const ctx: PropResolutionContext = { stateModel: {}, functions: {} };
+    resolvePropValue({ $computed: "dedupTest" }, ctx);
+    resolvePropValue({ $computed: "dedupTest" }, ctx);
+    const calls = warnSpy.mock.calls.filter((c) =>
+      String(c[0]).includes("dedupTest"),
+    );
+    expect(calls).toHaveLength(1);
+    warnSpy.mockRestore();
+  });
+
+  it("resolves nested expressions in args", () => {
+    const ctx: PropResolutionContext = {
+      stateModel: { active: true, values: { a: 10, b: 20 } },
+      functions: {
+        conditionalSum: (args) => {
+          if (args.enabled) return (args.x as number) + (args.y as number);
+          return 0;
+        },
+      },
+    };
+    expect(
+      resolvePropValue(
+        {
+          $computed: "conditionalSum",
+          args: {
+            enabled: { $state: "/active" },
+            x: { $state: "/values/a" },
+            y: { $state: "/values/b" },
+          },
+        },
+        ctx,
+      ),
+    ).toBe(30);
+  });
+});
+
+// =============================================================================
+// $template expressions
+// =============================================================================
+
+describe("$template expressions", () => {
+  it("interpolates state values into a string", () => {
+    const ctx: PropResolutionContext = {
+      stateModel: { user: { name: "Alice" }, count: 3 },
+    };
+    expect(
+      resolvePropValue(
+        { $template: "Hello, ${/user/name}! You have ${/count} messages." },
+        ctx,
+      ),
+    ).toBe("Hello, Alice! You have 3 messages.");
+  });
+
+  it("replaces missing paths with empty string", () => {
+    const ctx: PropResolutionContext = { stateModel: {} };
+    expect(resolvePropValue({ $template: "Hi ${/name}!" }, ctx)).toBe("Hi !");
+  });
+
+  it("handles template with no interpolations", () => {
+    const ctx: PropResolutionContext = { stateModel: {} };
+    expect(resolvePropValue({ $template: "No variables here" }, ctx)).toBe(
+      "No variables here",
+    );
+  });
+
+  it("handles multiple references to the same path", () => {
+    const ctx: PropResolutionContext = {
+      stateModel: { x: "A" },
+    };
+    expect(resolvePropValue({ $template: "${/x} and ${/x}" }, ctx)).toBe(
+      "A and A",
+    );
+  });
+
+  it("converts non-string values to strings", () => {
+    const ctx: PropResolutionContext = {
+      stateModel: { num: 42, bool: true },
+    };
+    expect(resolvePropValue({ $template: "${/num} is ${/bool}" }, ctx)).toBe(
+      "42 is true",
+    );
+  });
+
+  it("warns when path does not start with /", () => {
+    _resetWarnedTemplatePaths();
+    const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+    const ctx: PropResolutionContext = { stateModel: { name: "Bob" } };
+    const result = resolvePropValue({ $template: "Hi ${name}!" }, ctx);
+    expect(result).toBe("Hi Bob!");
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('$template path "name"'),
+    );
+    warnSpy.mockRestore();
+    _resetWarnedTemplatePaths();
+  });
+
+  it("deduplicates warnings for the same $template path", () => {
+    _resetWarnedTemplatePaths();
+    const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+    const ctx: PropResolutionContext = { stateModel: { name: "Bob" } };
+    resolvePropValue({ $template: "Hi ${name}!" }, ctx);
+    resolvePropValue({ $template: "Hi ${name}!" }, ctx);
+    const calls = warnSpy.mock.calls.filter((c) =>
+      String(c[0]).includes('$template path "name"'),
+    );
+    expect(calls).toHaveLength(1);
+    warnSpy.mockRestore();
+    _resetWarnedTemplatePaths();
+  });
+});

packages/core/src/props.ts

@@ -22,6 +22,10 @@ import { evaluateVisibility, type VisibilityContext } from "./visibility";
  *    repeat item — resolves via `repeatBasePath + path` and exposes the
  *    absolute state path for write-back.
  * - `{ $cond, $then, $else }` conditionally picks a value
+ * - `{ $computed: string, args?: Record<string, PropExpression> }` calls a
+ *    registered function with resolved args and returns the result
+ * - `{ $template: string }` interpolates `${/path}` references in the
+ *    string with values from the state model
  * - Any other value is a literal (passthrough)
  */
 export type PropExpression<T = unknown> =
@@ -35,7 +39,15 @@ export type PropExpression<T = unknown> =
       $cond: VisibilityCondition;
       $then: PropExpression<T>;
       $else: PropExpression<T>;
-    };
+    }
+  | { $computed: string; args?: Record<string, unknown> }
+  | { $template: string };
+
+/**
+ * Function signature for `$computed` expressions.
+ * Receives a record of resolved argument values and returns a computed result.
+ */
+export type ComputedFunction = (args: Record<string, unknown>) => unknown;
 
 /**
  * Context for resolving prop expressions.
@@ -45,6 +57,8 @@ export type PropExpression<T = unknown> =
 export interface PropResolutionContext extends VisibilityContext {
   /** Absolute state path to the current repeat item (e.g. "/todos/0"). Set inside repeat scopes. */
   repeatBasePath?: string;
+  /** Named functions available for `$computed` expressions. */
+  functions?: Record<string, ComputedFunction>;
 }
 
 // =============================================================================
@@ -110,6 +124,47 @@ function isCondExpression(
   );
 }
 
+function isComputedExpression(
+  value: unknown,
+): value is { $computed: string; args?: Record<string, unknown> } {
+  return (
+    typeof value === "object" &&
+    value !== null &&
+    "$computed" in value &&
+    typeof (value as Record<string, unknown>).$computed === "string"
+  );
+}
+
+function isTemplateExpression(value: unknown): value is { $template: string } {
+  return (
+    typeof value === "object" &&
+    value !== null &&
+    "$template" in value &&
+    typeof (value as Record<string, unknown>).$template === "string"
+  );
+}
+
+// Module-level set to avoid spamming console.warn on every render for the same
+// unknown $computed function name. Once the set reaches WARNED_COMPUTED_MAX,
+// new names are no longer deduplicated (warnings still fire) but the set stops
+// growing, preventing unbounded memory use in long-lived processes (e.g. SSR).
+const WARNED_COMPUTED_MAX = 100;
+const warnedComputedFns = new Set<string>();
+
+/** @internal Test-only: clear the deduplication set for $computed warnings. */
+export function _resetWarnedComputedFns(): void {
+  warnedComputedFns.clear();
+}
+
+// Same deduplication pattern for $template paths that don't start with "/".
+const WARNED_TEMPLATE_MAX = 100;
+const warnedTemplatePaths = new Set<string>();
+
+/** @internal Test-only: clear the deduplication set for $template warnings. */
+export function _resetWarnedTemplatePaths(): void {
+  warnedTemplatePaths.clear();
+}
+
 // =============================================================================
 // Prop Expression Resolution
 // =============================================================================
@@ -193,6 +248,50 @@ export function resolvePropValue(
     return resolvePropValue(result ? value.$then : value.$else, ctx);
   }
 
+  // $computed: call a registered function with resolved args
+  if (isComputedExpression(value)) {
+    const fn = ctx.functions?.[value.$computed];
+    if (!fn) {
+      if (!warnedComputedFns.has(value.$computed)) {
+        if (warnedComputedFns.size < WARNED_COMPUTED_MAX) {
+          warnedComputedFns.add(value.$computed);
+        }
+        console.warn(`Unknown $computed function: "${value.$computed}"`);
+      }
+      return undefined;
+    }
+    const resolvedArgs: Record<string, unknown> = {};
+    if (value.args) {
+      for (const [key, arg] of Object.entries(value.args)) {
+        resolvedArgs[key] = resolvePropValue(arg, ctx);
+      }
+    }
+    return fn(resolvedArgs);
+  }
+
+  // $template: interpolate ${/path} references with state values
+  if (isTemplateExpression(value)) {
+    return value.$template.replace(
+      /\$\{([^}]+)\}/g,
+      (_match, rawPath: string) => {
+        let path = rawPath;
+        if (!path.startsWith("/")) {
+          if (!warnedTemplatePaths.has(path)) {
+            if (warnedTemplatePaths.size < WARNED_TEMPLATE_MAX) {
+              warnedTemplatePaths.add(path);
+            }
+            console.warn(
+              `$template path "${path}" should be a JSON Pointer starting with "/". Automatically resolving as "/${path}".`,
+            );
+          }
+          path = "/" + path;
+        }
+        const resolved = getByPath(ctx.stateModel, path);
+        return resolved != null ? String(resolved) : "";
+      },
+    );
+  }
+
   // Arrays: resolve each element
   if (Array.isArray(value)) {
     return value.map((item) => resolvePropValue(item, ctx));

packages/core/src/schema.ts

@@ -900,6 +900,31 @@ Note: state patches appear right after the elements that use them, so the UI fil
     "Use $bindState for form inputs (text fields, checkboxes, selects, sliders, etc.) and $state for read-only data display. Inside repeat scopes, use $bindItem for form inputs bound to the current item. Use dynamic props instead of duplicating elements with opposing visible conditions when only prop values differ.",
   );
   lines.push("");
+  lines.push(
+    '4. Template: `{ "$template": "Hello, ${/name}!" }` - interpolates `${/path}` references in the string with values from the state model.',
+  );
+  lines.push(
+    '   Example: `"label": { "$template": "Items: ${/cart/count} | Total: ${/cart/total}" }` renders "Items: 3 | Total: 42.00" when /cart/count is 3 and /cart/total is 42.00.',
+  );
+  lines.push("");
+
+  // $computed section — only emit when catalog defines functions
+  const catalogFunctions = (catalog.data as Record<string, unknown>).functions;
+  if (catalogFunctions && Object.keys(catalogFunctions).length > 0) {
+    lines.push(
+      '5. Computed: `{ "$computed": "<functionName>", "args": { "key": <expression> } }` - calls a registered function with resolved args and returns the result.',
+    );
+    lines.push(
+      '   Example: `"value": { "$computed": "fullName", "args": { "first": { "$state": "/form/firstName" }, "last": { "$state": "/form/lastName" } } }`',
+    );
+    lines.push("   Available functions:");
+    for (const name of Object.keys(
+      catalogFunctions as Record<string, unknown>,
+    )) {
+      lines.push(`   - ${name}`);
+    }
+    lines.push("");
+  }
 
   // Validation section — only emit when at least one component has a `checks` prop
   const hasChecksComponents = allComponents
@@ -930,7 +955,19 @@ Note: state patches appear right after the elements that use them, so the UI fil
     lines.push("  - numeric — value must be a number");
     lines.push("  - url — valid URL format");
     lines.push(
-      '  - matches — must equal another field (args: { "other": "value" })',
+      '  - matches — must equal another field (args: { "other": { "$state": "/path" } })',
+    );
+    lines.push(
+      '  - equalTo — alias for matches (args: { "other": { "$state": "/path" } })',
+    );
+    lines.push(
+      '  - lessThan — value must be less than another field (args: { "other": { "$state": "/path" } })',
+    );
+    lines.push(
+      '  - greaterThan — value must be greater than another field (args: { "other": { "$state": "/path" } })',
+    );
+    lines.push(
+      '  - requiredIf — required only when another field is truthy (args: { "field": { "$state": "/path" } })',
     );
     lines.push("");
     lines.push("Example:");
@@ -947,6 +984,33 @@ Note: state patches appear right after the elements that use them, so the UI fil
     lines.push("");
   }
 
+  // State watchers section — only emit when actions are available (watchers
+  // trigger actions, so the section is irrelevant without them).
+  if (hasCustomActions || hasBuiltInActions) {
+    lines.push("STATE WATCHERS:");
+    lines.push(
+      "Elements can have an optional `watch` field to react to state changes and trigger actions. The `watch` field is a top-level field on the element (sibling of type/props/children), NOT inside props.",
+    );
+    lines.push(
+      "Maps state paths (JSON Pointers) to action bindings. When the value at a watched path changes, the bound actions fire automatically.",
+    );
+    lines.push("");
+    lines.push(
+      "Example (cascading select — country changes trigger city loading):",
+    );
+    lines.push(
+      `  ${JSON.stringify({ type: "Select", props: { value: { $bindState: "/form/country" }, options: ["US", "Canada", "UK"] }, watch: { "/form/country": { action: "loadCities", params: { country: { $state: "/form/country" } } } }, children: [] })}`,
+    );
+    lines.push("");
+    lines.push(
+      "Use `watch` for cascading dependencies where changing one field should trigger side effects (loading data, resetting dependent fields, computing derived values).",
+    );
+    lines.push(
+      "IMPORTANT: `watch` is a top-level field on the element (sibling of type/props/children), NOT inside props. Watchers only fire when the value changes, not on initial render.",
+    );
+    lines.push("");
+  }
+
   // Rules
   lines.push("RULES:");
   const baseRules =

packages/core/src/spec-validator.test.ts

@@ -0,0 +1,250 @@
+import { describe, it, expect } from "vitest";
+import type { Spec } from "./types";
+import { validateSpec, autoFixSpec } from "./spec-validator";
+
+// =============================================================================
+// validateSpec
+// =============================================================================
+
+describe("validateSpec", () => {
+  it("returns valid for a correct spec", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: { type: "Stack", props: {}, children: ["child1"] },
+        child1: { type: "Text", props: { text: "hello" }, children: [] },
+      },
+    };
+    const result = validateSpec(spec);
+    expect(result.valid).toBe(true);
+    expect(result.issues).toHaveLength(0);
+  });
+
+  it("detects missing root", () => {
+    const spec = {
+      root: "",
+      elements: { a: { type: "T", props: {}, children: [] } },
+    } as Spec;
+    const result = validateSpec(spec);
+    expect(result.valid).toBe(false);
+    expect(result.issues.some((i) => i.code === "missing_root")).toBe(true);
+  });
+
+  it("detects root_not_found", () => {
+    const spec: Spec = {
+      root: "missing",
+      elements: { a: { type: "T", props: {}, children: [] } },
+    };
+    const result = validateSpec(spec);
+    expect(result.valid).toBe(false);
+    expect(result.issues.some((i) => i.code === "root_not_found")).toBe(true);
+  });
+
+  it("detects empty spec", () => {
+    const spec: Spec = { root: "r", elements: {} };
+    const result = validateSpec(spec);
+    expect(result.valid).toBe(false);
+    expect(result.issues.some((i) => i.code === "empty_spec")).toBe(true);
+  });
+
+  it("detects missing_child", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: { type: "Stack", props: {}, children: ["nonexistent"] },
+      },
+    };
+    const result = validateSpec(spec);
+    expect(result.valid).toBe(false);
+    expect(result.issues.some((i) => i.code === "missing_child")).toBe(true);
+  });
+
+  it("detects visible_in_props", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: {
+          type: "Text",
+          props: { visible: { $state: "/show" } },
+          children: [],
+        },
+      },
+    };
+    const result = validateSpec(spec);
+    expect(result.valid).toBe(false);
+    expect(result.issues.some((i) => i.code === "visible_in_props")).toBe(true);
+  });
+
+  it("detects on_in_props", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: {
+          type: "Button",
+          props: { on: { press: { action: "doSomething" } } },
+          children: [],
+        },
+      },
+    };
+    const result = validateSpec(spec);
+    expect(result.valid).toBe(false);
+    expect(result.issues.some((i) => i.code === "on_in_props")).toBe(true);
+  });
+
+  it("detects repeat_in_props", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: {
+          type: "Stack",
+          props: { repeat: { statePath: "/items" } },
+          children: [],
+        },
+      },
+    };
+    const result = validateSpec(spec);
+    expect(result.valid).toBe(false);
+    expect(result.issues.some((i) => i.code === "repeat_in_props")).toBe(true);
+  });
+
+  it("detects watch_in_props", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: {
+          type: "Select",
+          props: {
+            watch: {
+              "/form/country": { action: "loadCities" },
+            },
+          },
+          children: [],
+        },
+      },
+    };
+    const result = validateSpec(spec);
+    expect(result.valid).toBe(false);
+    const watchIssue = result.issues.find((i) => i.code === "watch_in_props");
+    expect(watchIssue).toBeDefined();
+    expect(watchIssue!.elementKey).toBe("root");
+  });
+
+  it("detects orphaned elements when checkOrphans is true", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: { type: "Stack", props: {}, children: [] },
+        orphan: { type: "Text", props: {}, children: [] },
+      },
+    };
+    const result = validateSpec(spec, { checkOrphans: true });
+    expect(result.valid).toBe(true);
+    expect(result.issues.some((i) => i.code === "orphaned_element")).toBe(true);
+  });
+});
+
+// =============================================================================
+// autoFixSpec
+// =============================================================================
+
+describe("autoFixSpec", () => {
+  it("moves visible from props to element level", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: {
+          type: "Text",
+          props: { text: "hi", visible: { $state: "/show" } },
+          children: [],
+        },
+      },
+    };
+    const { spec: fixed, fixes } = autoFixSpec(spec);
+    expect(
+      (fixed.elements.root.props as Record<string, unknown>).visible,
+    ).toBeUndefined();
+    expect(fixed.elements.root.visible).toEqual({ $state: "/show" });
+    expect(fixes.some((f) => f.includes("visible"))).toBe(true);
+  });
+
+  it("moves on from props to element level", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: {
+          type: "Button",
+          props: { label: "OK", on: { press: { action: "submit" } } },
+          children: [],
+        },
+      },
+    };
+    const { spec: fixed, fixes } = autoFixSpec(spec);
+    expect(
+      (fixed.elements.root.props as Record<string, unknown>).on,
+    ).toBeUndefined();
+    expect(fixed.elements.root.on).toEqual({ press: { action: "submit" } });
+    expect(fixes.some((f) => f.includes('"on"'))).toBe(true);
+  });
+
+  it("moves repeat from props to element level", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: {
+          type: "Stack",
+          props: { repeat: { statePath: "/items" } },
+          children: ["child"],
+        },
+        child: { type: "Text", props: {}, children: [] },
+      },
+    };
+    const { spec: fixed, fixes } = autoFixSpec(spec);
+    expect(
+      (fixed.elements.root.props as Record<string, unknown>).repeat,
+    ).toBeUndefined();
+    expect(fixed.elements.root.repeat).toEqual({ statePath: "/items" });
+    expect(fixes.some((f) => f.includes('"repeat"'))).toBe(true);
+  });
+
+  it("moves watch from props to element level", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: {
+          type: "Select",
+          props: {
+            label: "Country",
+            watch: {
+              "/form/country": { action: "loadCities" },
+            },
+          },
+          children: [],
+        },
+      },
+    };
+    const { spec: fixed, fixes } = autoFixSpec(spec);
+    expect(
+      (fixed.elements.root.props as Record<string, unknown>).watch,
+    ).toBeUndefined();
+    expect(fixed.elements.root.watch).toEqual({
+      "/form/country": { action: "loadCities" },
+    });
+    expect(fixes.some((f) => f.includes('"watch"'))).toBe(true);
+  });
+
+  it("returns no fixes for a correct spec", () => {
+    const spec: Spec = {
+      root: "root",
+      elements: {
+        root: {
+          type: "Stack",
+          props: { direction: "vertical" },
+          children: [],
+          watch: { "/x": { action: "y" } },
+        },
+      },
+    };
+    const { fixes } = autoFixSpec(spec);
+    expect(fixes).toHaveLength(0);
+  });
+});

packages/core/src/spec-validator.ts

@@ -28,7 +28,8 @@ export interface SpecIssue {
     | "orphaned_element"
     | "empty_spec"
     | "on_in_props"
-    | "repeat_in_props";
+    | "repeat_in_props"
+    | "watch_in_props";
 }
 
 /**
@@ -151,6 +152,16 @@ export function validateSpec(
         code: "repeat_in_props",
       });
     }
+
+    // 3e. `watch` inside props (should be a top-level field)
+    if (props && "watch" in props && props.watch !== undefined) {
+      issues.push({
+        severity: "error",
+        message: `Element "${key}" has "watch" inside "props". It should be a top-level field on the element (sibling of type/props/children).`,
+        elementKey: key,
+        code: "watch_in_props",
+      });
+    }
   }
 
   // 4. Orphaned elements (optional)
@@ -248,6 +259,21 @@ export function autoFixSpec(spec: Spec): {
       fixes.push(`Moved "repeat" from props to element level on "${key}".`);
     }
 
+    currentProps = fixed.props as Record<string, unknown> | undefined;
+    if (
+      currentProps &&
+      "watch" in currentProps &&
+      currentProps.watch !== undefined
+    ) {
+      const { watch, ...restProps } = currentProps;
+      fixed = {
+        ...fixed,
+        props: restProps,
+        watch: watch as UIElement["watch"],
+      };
+      fixes.push(`Moved "watch" from props to element level on "${key}".`);
+    }
+
     fixedElements[key] = fixed;
   }
 

packages/core/src/types.ts

@@ -69,6 +69,12 @@ export interface UIElement<
   on?: Record<string, ActionBinding | ActionBinding[]>;
   /** Repeat children once per item in a state array */
   repeat?: { statePath: string; key?: string };
+  /**
+   * State watchers — maps JSON Pointer state paths to action bindings.
+   * When the value at a watched path changes, the bound actions fire.
+   * Useful for cascading dependencies (e.g. country → city option loading).
+   */
+  watch?: Record<string, ActionBinding | ActionBinding[]>;
 }
 
 /**

packages/core/src/validation.test.ts

@@ -187,6 +187,226 @@ describe("builtInValidationFunctions", () => {
       ).toBe(false);
     });
   });
+
+  describe("equalTo", () => {
+    it("passes when values are equal", () => {
+      expect(builtInValidationFunctions.equalTo("abc", { other: "abc" })).toBe(
+        true,
+      );
+    });
+
+    it("fails when values differ", () => {
+      expect(builtInValidationFunctions.equalTo("abc", { other: "xyz" })).toBe(
+        false,
+      );
+    });
+  });
+
+  describe("lessThan", () => {
+    it("passes when value is less than other", () => {
+      expect(builtInValidationFunctions.lessThan(3, { other: 5 })).toBe(true);
+    });
+
+    it("fails when value equals other", () => {
+      expect(builtInValidationFunctions.lessThan(5, { other: 5 })).toBe(false);
+    });
+
+    it("fails when value is greater than other", () => {
+      expect(builtInValidationFunctions.lessThan(7, { other: 5 })).toBe(false);
+    });
+
+    it("coerces numeric string vs number", () => {
+      expect(builtInValidationFunctions.lessThan("3", { other: 5 })).toBe(true);
+    });
+
+    it("fails coercion when non-numeric string", () => {
+      expect(builtInValidationFunctions.lessThan("abc", { other: 5 })).toBe(
+        false,
+      );
+    });
+
+    it("passes for string comparison (ISO dates)", () => {
+      expect(
+        builtInValidationFunctions.lessThan("2026-01-01", {
+          other: "2026-06-15",
+        }),
+      ).toBe(true);
+    });
+
+    it("fails for equal strings", () => {
+      expect(
+        builtInValidationFunctions.lessThan("2026-01-01", {
+          other: "2026-01-01",
+        }),
+      ).toBe(false);
+    });
+
+    it("returns false when value is empty string", () => {
+      expect(builtInValidationFunctions.lessThan("", { other: 5 })).toBe(false);
+    });
+
+    it("returns false when other is empty string", () => {
+      expect(builtInValidationFunctions.lessThan(3, { other: "" })).toBe(false);
+    });
+
+    it("returns false when value is empty string vs non-empty string", () => {
+      expect(builtInValidationFunctions.lessThan("", { other: "abc" })).toBe(
+        false,
+      );
+    });
+
+    it("returns false when other is empty string vs non-empty string", () => {
+      expect(builtInValidationFunctions.lessThan("abc", { other: "" })).toBe(
+        false,
+      );
+    });
+
+    it("returns false when other is null", () => {
+      expect(builtInValidationFunctions.lessThan(3, { other: null })).toBe(
+        false,
+      );
+    });
+
+    it("returns false when value is null", () => {
+      expect(builtInValidationFunctions.lessThan(null, { other: 5 })).toBe(
+        false,
+      );
+    });
+
+    it("returns false when other is undefined", () => {
+      expect(builtInValidationFunctions.lessThan(3, { other: undefined })).toBe(
+        false,
+      );
+    });
+  });
+
+  describe("greaterThan", () => {
+    it("passes when value is greater than other", () => {
+      expect(builtInValidationFunctions.greaterThan(7, { other: 5 })).toBe(
+        true,
+      );
+    });
+
+    it("fails when value equals other", () => {
+      expect(builtInValidationFunctions.greaterThan(5, { other: 5 })).toBe(
+        false,
+      );
+    });
+
+    it("fails when value is less than other", () => {
+      expect(builtInValidationFunctions.greaterThan(3, { other: 5 })).toBe(
+        false,
+      );
+    });
+
+    it("coerces numeric string vs number", () => {
+      expect(builtInValidationFunctions.greaterThan("7", { other: 5 })).toBe(
+        true,
+      );
+    });
+
+    it("fails coercion when non-numeric string", () => {
+      expect(builtInValidationFunctions.greaterThan("abc", { other: 5 })).toBe(
+        false,
+      );
+    });
+
+    it("passes for string comparison (ISO dates)", () => {
+      expect(
+        builtInValidationFunctions.greaterThan("2026-06-15", {
+          other: "2026-01-01",
+        }),
+      ).toBe(true);
+    });
+
+    it("fails for lesser strings", () => {
+      expect(
+        builtInValidationFunctions.greaterThan("2026-01-01", {
+          other: "2026-06-15",
+        }),
+      ).toBe(false);
+    });
+
+    it("returns false when value is empty string", () => {
+      expect(builtInValidationFunctions.greaterThan("", { other: 5 })).toBe(
+        false,
+      );
+    });
+
+    it("returns false when other is empty string", () => {
+      expect(builtInValidationFunctions.greaterThan(3, { other: "" })).toBe(
+        false,
+      );
+    });
+
+    it("returns false when value is empty string vs non-empty string", () => {
+      expect(builtInValidationFunctions.greaterThan("", { other: "abc" })).toBe(
+        false,
+      );
+    });
+
+    it("returns false when other is empty string vs non-empty string", () => {
+      expect(builtInValidationFunctions.greaterThan("abc", { other: "" })).toBe(
+        false,
+      );
+    });
+
+    it("returns false when other is null", () => {
+      expect(builtInValidationFunctions.greaterThan(3, { other: null })).toBe(
+        false,
+      );
+    });
+
+    it("returns false when value is undefined", () => {
+      expect(
+        builtInValidationFunctions.greaterThan(undefined, { other: 5 }),
+      ).toBe(false);
+    });
+
+    it("returns false when value is null", () => {
+      expect(builtInValidationFunctions.greaterThan(null, { other: 5 })).toBe(
+        false,
+      );
+    });
+  });
+
+  describe("requiredIf", () => {
+    it("passes when condition is falsy (field not required)", () => {
+      expect(builtInValidationFunctions.requiredIf("", { field: false })).toBe(
+        true,
+      );
+      expect(builtInValidationFunctions.requiredIf("", { field: "" })).toBe(
+        true,
+      );
+      expect(builtInValidationFunctions.requiredIf("", { field: null })).toBe(
+        true,
+      );
+      expect(
+        builtInValidationFunctions.requiredIf("", { field: undefined }),
+      ).toBe(true);
+    });
+
+    it("fails when condition is truthy and value is empty", () => {
+      expect(builtInValidationFunctions.requiredIf("", { field: true })).toBe(
+        false,
+      );
+      expect(
+        builtInValidationFunctions.requiredIf(null, { field: "yes" }),
+      ).toBe(false);
+      expect(
+        builtInValidationFunctions.requiredIf(undefined, { field: 1 }),
+      ).toBe(false);
+    });
+
+    it("passes when condition is truthy and value is present", () => {
+      expect(
+        builtInValidationFunctions.requiredIf("hello", { field: true }),
+      ).toBe(true);
+      expect(builtInValidationFunctions.requiredIf(42, { field: true })).toBe(
+        true,
+      );
+    });
+  });
 });
 
 describe("runValidationCheck", () => {
@@ -391,6 +611,22 @@ describe("check helper", () => {
     });
   });
 
+  describe("numeric", () => {
+    it("creates numeric check with default message", () => {
+      const c = check.numeric();
+
+      expect(c.type).toBe("numeric");
+      expect(c.message).toBe("Must be a number");
+    });
+
+    it("creates numeric check with custom message", () => {
+      const c = check.numeric("Numbers only");
+
+      expect(c.type).toBe("numeric");
+      expect(c.message).toBe("Numbers only");
+    });
+  });
+
   describe("matches", () => {
     it("creates matches check with path reference", () => {
       const c = check.matches("/password", "Passwords must match");
@@ -400,4 +636,109 @@ describe("check helper", () => {
       expect(c.message).toBe("Passwords must match");
     });
   });
+
+  describe("equalTo", () => {
+    it("creates equalTo check with path reference", () => {
+      const c = check.equalTo("/email", "Emails must match");
+
+      expect(c.type).toBe("equalTo");
+      expect(c.args).toEqual({ other: { $state: "/email" } });
+      expect(c.message).toBe("Emails must match");
+    });
+  });
+
+  describe("lessThan", () => {
+    it("creates lessThan check with path reference", () => {
+      const c = check.lessThan("/maxValue", "Must be less");
+
+      expect(c.type).toBe("lessThan");
+      expect(c.args).toEqual({ other: { $state: "/maxValue" } });
+      expect(c.message).toBe("Must be less");
+    });
+  });
+
+  describe("greaterThan", () => {
+    it("creates greaterThan check with path reference", () => {
+      const c = check.greaterThan("/minValue");
+
+      expect(c.type).toBe("greaterThan");
+      expect(c.args).toEqual({ other: { $state: "/minValue" } });
+    });
+  });
+
+  describe("requiredIf", () => {
+    it("creates requiredIf check with path reference", () => {
+      const c = check.requiredIf("/toggle", "Required when toggle is on");
+
+      expect(c.type).toBe("requiredIf");
+      expect(c.args).toEqual({ field: { $state: "/toggle" } });
+      expect(c.message).toBe("Required when toggle is on");
+    });
+  });
+});
+
+// =============================================================================
+// Deep arg resolution in runValidationCheck
+// =============================================================================
+
+describe("deep arg resolution", () => {
+  it("resolves nested $state refs in validation args", () => {
+    const result = runValidationCheck(
+      {
+        type: "matches",
+        args: { other: { $state: "/form/password" } },
+        message: "Passwords must match",
+      },
+      {
+        value: "secret123",
+        stateModel: { form: { password: "secret123" } },
+      },
+    );
+    expect(result.valid).toBe(true);
+  });
+
+  it("resolves $state in cross-field lessThan check", () => {
+    const result = runValidationCheck(
+      {
+        type: "lessThan",
+        args: { other: { $state: "/form/maxPrice" } },
+        message: "Must be less than max price",
+      },
+      {
+        value: 50,
+        stateModel: { form: { maxPrice: 100 } },
+      },
+    );
+    expect(result.valid).toBe(true);
+  });
+
+  it("resolves $state in requiredIf check", () => {
+    const result = runValidationCheck(
+      {
+        type: "requiredIf",
+        args: { field: { $state: "/form/enableEmail" } },
+        message: "Email is required",
+      },
+      {
+        value: "",
+        stateModel: { form: { enableEmail: true } },
+      },
+    );
+    expect(result.valid).toBe(false);
+  });
+
+  it("passes requiredIf when condition is false", () => {
+    const result = runValidationCheck(
+      {
+        type: "requiredIf",
+        args: { field: { $state: "/form/enableEmail" } },
+        message: "Email is required",
+      },
+      {
+        value: "",
+        stateModel: { form: { enableEmail: false } },
+      },
+    );
+    expect(result.valid).toBe(true);
+  });
 });

packages/core/src/validation.ts

@@ -2,6 +2,7 @@ import { z } from "zod";
 import type { DynamicValue, StateModel, VisibilityCondition } from "./types";
 import { DynamicValueSchema, resolveDynamicValue } from "./types";
 import { VisibilityConditionSchema, evaluateVisibility } from "./visibility";
+import { resolvePropValue } from "./props";
 
 /**
  * Validation check definition
@@ -63,6 +64,14 @@ export interface ValidationFunctionDefinition {
   description?: string;
 }
 
+const matchesImpl: ValidationFunction = (
+  value: unknown,
+  args?: Record<string, unknown>,
+) => {
+  const other = args?.other;
+  return value === other;
+};
+
 /**
  * Built-in validation functions
  */
@@ -164,9 +173,64 @@ export const builtInValidationFunctions: Record<string, ValidationFunction> = {
   /**
    * Check if value matches another field
    */
-  matches: (value: unknown, args?: Record<string, unknown>) => {
+  matches: matchesImpl,
+
+  /**
+   * Alias for matches with a more descriptive name for cross-field equality
+   */
+  equalTo: matchesImpl,
+
+  /**
+   * Check if value is less than another field's value.
+   * Supports numbers, strings (useful for ISO date comparison), and
+   * cross-type numeric coercion (e.g. string "3" vs number 5).
+   */
+  lessThan: (value: unknown, args?: Record<string, unknown>) => {
     const other = args?.other;
-    return value === other;
+    if (value == null || other == null || value === "" || other === "")
+      return false;
+    if (typeof value === "number" && typeof other === "number")
+      return value < other;
+    if (typeof value === "string" && typeof other === "string")
+      return value < other;
+    const numVal = Number(value);
+    const numOther = Number(other);
+    if (!isNaN(numVal) && !isNaN(numOther)) return numVal < numOther;
+    return false;
+  },
+
+  /**
+   * Check if value is greater than another field's value.
+   * Supports numbers, strings (useful for ISO date comparison), and
+   * cross-type numeric coercion (e.g. string "7" vs number 5).
+   */
+  greaterThan: (value: unknown, args?: Record<string, unknown>) => {
+    const other = args?.other;
+    if (value == null || other == null || value === "" || other === "")
+      return false;
+    if (typeof value === "number" && typeof other === "number")
+      return value > other;
+    if (typeof value === "string" && typeof other === "string")
+      return value > other;
+    const numVal = Number(value);
+    const numOther = Number(other);
+    if (!isNaN(numVal) && !isNaN(numOther)) return numVal > numOther;
+    return false;
+  },
+
+  /**
+   * Required only when a condition is met.
+   * Uses JS truthiness: 0, false, "", null, and undefined are all
+   * treated as "condition not met" (field not required), matching
+   * the visibility system's bare-condition semantics.
+   */
+  requiredIf: (value: unknown, args?: Record<string, unknown>) => {
+    const condition = args?.field;
+    if (!condition) return true;
+    if (value === null || value === undefined) return false;
+    if (typeof value === "string") return value.trim().length > 0;
+    if (Array.isArray(value)) return value.length > 0;
+    return true;
   },
 };
 
@@ -209,11 +273,12 @@ export function runValidationCheck(
 ): ValidationCheckResult {
   const { value, stateModel, customFunctions } = ctx;
 
-  // Resolve args
+  // Resolve args using resolvePropValue so nested $state refs (and any other
+  // prop expressions) are handled consistently with the rest of the system.
   const resolvedArgs: Record<string, unknown> = {};
   if (check.args) {
     for (const [key, argValue] of Object.entries(check.args)) {
-      resolvedArgs[key] = resolveDynamicValue(argValue, stateModel);
+      resolvedArgs[key] = resolvePropValue(argValue, { stateModel });
     }
   }
 
@@ -326,6 +391,11 @@ export const check = {
     message,
   }),
 
+  numeric: (message = "Must be a number"): ValidationCheck => ({
+    type: "numeric",
+    message,
+  }),
+
   matches: (
     otherPath: string,
     message = "Fields must match",
@@ -334,4 +404,34 @@ export const check = {
     args: { other: { $state: otherPath } },
     message,
   }),
+
+  equalTo: (
+    otherPath: string,
+    message = "Fields must match",
+  ): ValidationCheck => ({
+    type: "equalTo",
+    args: { other: { $state: otherPath } },
+    message,
+  }),
+
+  lessThan: (otherPath: string, message?: string): ValidationCheck => ({
+    type: "lessThan",
+    args: { other: { $state: otherPath } },
+    message: message ?? "Must be less than the compared field",
+  }),
+
+  greaterThan: (otherPath: string, message?: string): ValidationCheck => ({
+    type: "greaterThan",
+    args: { other: { $state: otherPath } },
+    message: message ?? "Must be greater than the compared field",
+  }),
+
+  requiredIf: (
+    fieldPath: string,
+    message = "This field is required",
+  ): ValidationCheck => ({
+    type: "requiredIf",
+    args: { field: { $state: fieldPath } },
+    message,
+  }),
 };

packages/jotai/CHANGELOG.md

@@ -1,5 +1,11 @@
 # @json-render/jotai
 
+## 0.9.1
+
+### Patch Changes
+
+- @json-render/core@0.9.1
+
 ## 0.9.0
 
 ### Minor Changes

packages/jotai/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@json-render/jotai",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "license": "Apache-2.0",
   "description": "Jotai adapter for json-render StateStore",
   "keywords": [

packages/react-native/CHANGELOG.md

@@ -1,5 +1,12 @@
 # @json-render/react-native
 
+## 0.9.1
+
+### Patch Changes
+
+- b103676: Fix install failure caused by `@internal/react-state` (a private workspace package) being listed as a published dependency. The internal package is now bundled into each renderer's output at build time, so consumers no longer need to resolve it from npm.
+  - @json-render/core@0.9.1
+
 ## 0.9.0
 
 ### Minor Changes

packages/react-native/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@json-render/react-native",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "license": "Apache-2.0",
   "description": "React Native renderer for @json-render/core. JSON becomes React Native components.",
   "keywords": [
@@ -56,10 +56,10 @@
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
-    "@json-render/core": "workspace:*",
-    "@internal/react-state": "workspace:*"
+    "@json-render/core": "workspace:*"
   },
   "devDependencies": {
+    "@internal/react-state": "workspace:*",
     "@internal/typescript-config": "workspace:*",
     "@types/react": "19.2.3",
     "react-native": "0.83.1",

packages/react-native/tsup.config.ts

@@ -3,8 +3,9 @@ import { defineConfig } from "tsup";
 export default defineConfig({
   entry: ["src/index.ts", "src/schema.ts", "src/catalog.ts"],
   format: ["cjs", "esm"],
-  dts: true,
+  dts: { resolve: ["@internal/react-state"] },
   sourcemap: true,
   clean: true,
+  noExternal: ["@internal/react-state"],
   external: ["react", "react-native", "@json-render/core", "zod"],
 });

packages/react-pdf/CHANGELOG.md

@@ -1,5 +1,12 @@
 # @json-render/react-pdf
 
+## 0.9.1
+
+### Patch Changes
+
+- b103676: Fix install failure caused by `@internal/react-state` (a private workspace package) being listed as a published dependency. The internal package is now bundled into each renderer's output at build time, so consumers no longer need to resolve it from npm.
+  - @json-render/core@0.9.1
+
 ## 0.9.0
 
 ### Minor Changes

packages/react-pdf/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@json-render/react-pdf",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "license": "Apache-2.0",
   "description": "React PDF renderer for @json-render/core. JSON becomes PDF documents.",
   "keywords": [
@@ -61,10 +61,10 @@
   },
   "dependencies": {
     "@json-render/core": "workspace:*",
-    "@internal/react-state": "workspace:*",
     "@react-pdf/renderer": "^4.3.2"
   },
   "devDependencies": {
+    "@internal/react-state": "workspace:*",
     "@internal/typescript-config": "workspace:*",
     "@types/react": "19.2.3",
     "tsup": "^8.0.2",

packages/react-pdf/tsup.config.ts

@@ -3,8 +3,9 @@ import { defineConfig } from "tsup";
 export default defineConfig({
   entry: ["src/index.ts", "src/server.ts", "src/catalog.ts", "src/render.tsx"],
   format: ["cjs", "esm"],
-  dts: true,
+  dts: { resolve: ["@internal/react-state"] },
   sourcemap: true,
   clean: true,
+  noExternal: ["@internal/react-state"],
   external: ["react", "@json-render/core", "@react-pdf/renderer", "zod"],
 });

packages/react-state/CHANGELOG.md

@@ -1,5 +1,11 @@
 # @internal/react-state
 
+## 0.8.2
+
+### Patch Changes
+
+- @json-render/core@0.9.1
+
 ## 0.8.1
 
 ### Patch Changes

packages/react-state/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@internal/react-state",
-  "version": "0.8.1",
+  "version": "0.8.2",
   "private": true,
   "license": "Apache-2.0",
   "description": "Shared React state context for json-render renderer packages",

packages/react/CHANGELOG.md

@@ -1,5 +1,12 @@
 # @json-render/react
 
+## 0.9.1
+
+### Patch Changes
+
+- b103676: Fix install failure caused by `@internal/react-state` (a private workspace package) being listed as a published dependency. The internal package is now bundled into each renderer's output at build time, so consumers no longer need to resolve it from npm.
+  - @json-render/core@0.9.1
+
 ## 0.9.0
 
 ### Minor Changes

packages/react/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@json-render/react",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "license": "Apache-2.0",
   "description": "React renderer for @json-render/core. JSON becomes React components.",
   "keywords": [
@@ -50,10 +50,10 @@
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
-    "@json-render/core": "workspace:*",
-    "@internal/react-state": "workspace:*"
+    "@json-render/core": "workspace:*"
   },
   "devDependencies": {
+    "@internal/react-state": "workspace:*",
     "@internal/typescript-config": "workspace:*",
     "@types/react": "19.2.3",
     "tsup": "^8.0.2",

packages/react/src/contexts/actions.tsx

@@ -17,6 +17,7 @@ import {
   type ResolvedAction,
 } from "@json-render/core";
 import { useStateStore } from "./state";
+import { useOptionalValidation } from "./validation";
 
 /**
  * Generate a unique ID for use with the "$id" token.
@@ -137,6 +138,7 @@ export function ActionProvider({
   children,
 }: ActionProviderProps) {
   const { get, set, getSnapshot } = useStateStore();
+  const validation = useOptionalValidation();
 
   const [handlers, setHandlers] =
     useState<Record<string, ActionHandler>>(initialHandlers);
@@ -227,13 +229,34 @@ export function ActionProvider({
           if (previousScreen) {
             set("/currentScreen", previousScreen);
           } else {
-            // Sentinel empty string = clear currentScreen (return to default)
             set("/currentScreen", undefined);
           }
         }
         return;
       }
 
+      // Built-in: validateForm triggers validateAll from the ValidationProvider
+      // and writes the result to a state path (default: /formValidation).
+      // IMPORTANT: validateAll() is synchronous — it runs all registered field
+      // validations and returns immediately. This guarantees that the next action
+      // in a sequential list (e.g. [validateForm, submitForm]) can read the
+      // validation result from state without awaiting an extra tick.
+      if (resolved.action === "validateForm") {
+        const validateAll = validation?.validateAll;
+        if (!validateAll) {
+          console.warn(
+            "validateForm action was dispatched but no ValidationProvider is connected. " +
+              "Ensure ValidationProvider is rendered inside the provider tree.",
+          );
+          return;
+        }
+        const valid = validateAll();
+        const statePath =
+          (resolved.params?.statePath as string) || "/formValidation";
+        set(statePath, { valid });
+        return;
+      }
+
       const handler = handlers[resolved.action];
 
       if (!handler) {
@@ -300,7 +323,7 @@ export function ActionProvider({
         });
       }
     },
-    [handlers, get, set, getSnapshot, navigate],
+    [handlers, get, set, getSnapshot, navigate, validation],
   );
 
   const confirm = useCallback(() => {

packages/react/src/contexts/validation.tsx

@@ -6,7 +6,6 @@ import React, {
   useState,
   useCallback,
   useMemo,
-  useRef,
   type ReactNode,
 } from "react";
 import {
@@ -130,11 +129,7 @@ export function ValidationProvider({
   customFunctions = {},
   children,
 }: ValidationProviderProps) {
-  const { state } = useStateStore();
-  // Keep a ref to the latest state so `validate` doesn't change on every
-  // state update — preventing the entire validation context from churning.
-  const stateRef = useRef(state);
-  stateRef.current = state;
+  const { state, getSnapshot } = useStateStore();
 
   const [fieldStates, setFieldStates] = useState<
     Record<string, FieldValidationState>
@@ -160,8 +155,10 @@ export function ValidationProvider({
 
   const validate = useCallback(
     (path: string, config: ValidationConfig): ValidationResult => {
-      // Walk the nested state object using JSON Pointer segments
-      const currentState = stateRef.current;
+      // Read from the store directly so validation sees values written in the
+      // same synchronous handler (e.g. setValue then validate in onChange).
+      // Using React state would return the stale pre-render snapshot.
+      const currentState = getSnapshot();
       const segments = path.split("/").filter(Boolean);
       let value: unknown = currentState;
       for (const seg of segments) {
@@ -189,7 +186,7 @@ export function ValidationProvider({
 
       return result;
     },
-    [customFunctions],
+    [customFunctions, getSnapshot],
   );
 
   const touch = useCallback((path: string) => {
@@ -263,6 +260,14 @@ export function useValidation(): ValidationContextValue {
   return ctx;
 }
 
+/**
+ * Non-throwing variant of useValidation.
+ * Returns null when no ValidationProvider is present.
+ */
+export function useOptionalValidation(): ValidationContextValue | null {
+  return useContext(ValidationContext);
+}
+
 /**
  * Hook to get validation state for a field
  */

packages/react/src/dynamic-forms.test.tsx

@@ -0,0 +1,770 @@
+import { describe, it, expect, vi } from "vitest";
+import React, { useState, useCallback, useMemo } from "react";
+import { render, act, fireEvent, screen } from "@testing-library/react";
+import type { Spec } from "@json-render/core";
+import {
+  JSONUIProvider,
+  Renderer,
+  type ComponentRenderProps,
+} from "./renderer";
+import { useStateStore } from "./contexts/state";
+import { useFieldValidation } from "./contexts/validation";
+import { useBoundProp } from "./hooks";
+
+// =============================================================================
+// Stub components
+// =============================================================================
+
+function Button({ element, emit }: ComponentRenderProps<{ label: string }>) {
+  return (
+    <button data-testid="btn" onClick={() => emit("press")}>
+      {element.props.label}
+    </button>
+  );
+}
+
+function Text({ element }: ComponentRenderProps<{ text: unknown }>) {
+  const value = element.props.text;
+  return (
+    <span data-testid="text">
+      {value == null
+        ? ""
+        : typeof value === "string"
+          ? value
+          : JSON.stringify(value)}
+    </span>
+  );
+}
+
+function InputField({
+  element,
+  bindings,
+}: ComponentRenderProps<{
+  label?: string;
+  value?: string;
+  checks?: Array<{
+    type: string;
+    message: string;
+    args?: Record<string, unknown>;
+  }>;
+}>) {
+  const props = element.props;
+  const [boundValue, setBoundValue] = useBoundProp<string>(
+    props.value as string | undefined,
+    bindings?.value,
+  );
+  const [localValue, setLocalValue] = useState("");
+  const isBound = !!bindings?.value;
+  const value = isBound ? (boundValue ?? "") : localValue;
+  const setValue = isBound ? setBoundValue : setLocalValue;
+
+  const hasValidation = !!(bindings?.value && props.checks?.length);
+  const config = useMemo(
+    () => (hasValidation ? { checks: props.checks ?? [] } : undefined),
+    [hasValidation, props.checks],
+  );
+  const { errors } = useFieldValidation(bindings?.value ?? "", config);
+
+  return (
+    <div>
+      {props.label && <label>{props.label}</label>}
+      <input
+        data-testid="input"
+        value={value}
+        onChange={(e) => setValue(e.target.value)}
+      />
+      {errors.length > 0 && <span data-testid="input-error">{errors[0]}</span>}
+    </div>
+  );
+}
+
+function SelectField({
+  element,
+  bindings,
+}: ComponentRenderProps<{ label?: string; value?: string }>) {
+  const props = element.props;
+  const [boundValue] = useBoundProp<string>(
+    props.value as string | undefined,
+    bindings?.value,
+  );
+  return <span data-testid="select-value">{boundValue ?? ""}</span>;
+}
+
+/**
+ * Select stub that mirrors the real shadcn Select validation behavior:
+ * calls setValue then validate() synchronously in onValueChange.
+ */
+function ValidatedSelect({
+  element,
+  bindings,
+  emit,
+}: ComponentRenderProps<{
+  label?: string;
+  name?: string;
+  options?: string[];
+  placeholder?: string;
+  value?: string;
+  checks?: Array<{
+    type: string;
+    message: string;
+    args?: Record<string, unknown>;
+  }>;
+  validateOn?: "change" | "blur" | "submit";
+}>) {
+  const props = element.props;
+  const [boundValue, setBoundValue] = useBoundProp<string>(
+    props.value as string | undefined,
+    bindings?.value,
+  );
+  const [localValue, setLocalValue] = useState("");
+  const isBound = !!bindings?.value;
+  const value = isBound ? (boundValue ?? "") : localValue;
+  const setValue = isBound ? setBoundValue : setLocalValue;
+  const validateOn = props.validateOn ?? "change";
+
+  const hasValidation = !!(bindings?.value && props.checks?.length);
+  const config = useMemo(
+    () =>
+      hasValidation ? { checks: props.checks ?? [], validateOn } : undefined,
+    [hasValidation, props.checks, validateOn],
+  );
+  const { errors, validate } = useFieldValidation(
+    bindings?.value ?? "",
+    config,
+  );
+
+  const options = props.options ?? [];
+
+  return (
+    <div>
+      {props.label && <label>{props.label}</label>}
+      <select
+        data-testid={`select-${props.name ?? "default"}`}
+        value={value}
+        onChange={(e) => {
+          setValue(e.target.value);
+          if (hasValidation && validateOn === "change") validate();
+          emit("change");
+        }}
+      >
+        <option value="">{props.placeholder ?? "Select..."}</option>
+        {options.map((opt) => (
+          <option key={opt} value={opt}>
+            {opt}
+          </option>
+        ))}
+      </select>
+      {errors.length > 0 && (
+        <span data-testid={`select-error-${props.name ?? "default"}`}>
+          {errors[0]}
+        </span>
+      )}
+    </div>
+  );
+}
+
+function StateProbe() {
+  const { state } = useStateStore();
+  return <pre data-testid="state-probe">{JSON.stringify(state)}</pre>;
+}
+
+const registry = { Button, Text, Input: InputField, Select: SelectField };
+
+function getState(): Record<string, unknown> {
+  return JSON.parse(screen.getByTestId("state-probe").textContent!);
+}
+
+// =============================================================================
+// $computed expressions in rendering
+// =============================================================================
+
+describe("$computed expressions in rendering", () => {
+  it("resolves a $computed prop using provided functions", async () => {
+    const spec: Spec = {
+      state: { first: "Jane", last: "Doe" },
+      root: "main",
+      elements: {
+        main: {
+          type: "Text",
+          props: {
+            text: {
+              $computed: "fullName",
+              args: {
+                first: { $state: "/first" },
+                last: { $state: "/last" },
+              },
+            },
+          },
+          children: [],
+        },
+      },
+    };
+
+    const functions = {
+      fullName: (args: Record<string, unknown>) => `${args.first} ${args.last}`,
+    };
+
+    render(
+      <JSONUIProvider
+        registry={registry}
+        initialState={spec.state}
+        functions={functions}
+      >
+        <Renderer spec={spec} registry={registry} />
+      </JSONUIProvider>,
+    );
+
+    expect(screen.getByTestId("text").textContent).toBe("Jane Doe");
+  });
+
+  it("renders gracefully when functions prop is omitted", async () => {
+    const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+    const spec: Spec = {
+      state: {},
+      root: "main",
+      elements: {
+        main: {
+          type: "Text",
+          props: {
+            text: { $computed: "missing" },
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider registry={registry} initialState={spec.state}>
+        <Renderer spec={spec} registry={registry} />
+      </JSONUIProvider>,
+    );
+
+    expect(screen.getByTestId("text").textContent).toBe("");
+    warnSpy.mockRestore();
+  });
+});
+
+// =============================================================================
+// $template expressions in rendering
+// =============================================================================
+
+describe("$template expressions in rendering", () => {
+  it("interpolates state values into a template string", () => {
+    const spec: Spec = {
+      state: { user: { name: "Alice" }, count: 3 },
+      root: "main",
+      elements: {
+        main: {
+          type: "Text",
+          props: {
+            text: {
+              $template: "Hello, ${/user/name}! You have ${/count} messages.",
+            },
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider registry={registry} initialState={spec.state}>
+        <Renderer spec={spec} registry={registry} />
+      </JSONUIProvider>,
+    );
+
+    expect(screen.getByTestId("text").textContent).toBe(
+      "Hello, Alice! You have 3 messages.",
+    );
+  });
+
+  it("resolves missing paths to empty string", () => {
+    const spec: Spec = {
+      state: {},
+      root: "main",
+      elements: {
+        main: {
+          type: "Text",
+          props: {
+            text: { $template: "Hi ${/name}!" },
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider registry={registry} initialState={spec.state}>
+        <Renderer spec={spec} registry={registry} />
+      </JSONUIProvider>,
+    );
+
+    expect(screen.getByTestId("text").textContent).toBe("Hi !");
+  });
+});
+
+// =============================================================================
+// Watchers
+// =============================================================================
+
+describe("watchers (watch field)", () => {
+  it("does not fire on initial render, fires when watched state changes", async () => {
+    const loadCities = vi.fn(async (params: Record<string, unknown>) => {
+      // no-op, just tracking the call
+    });
+
+    const spec: Spec = {
+      state: { form: { country: "" }, citiesLoaded: false },
+      root: "main",
+      elements: {
+        main: {
+          type: "Button",
+          props: { label: "Set Country" },
+          on: {
+            press: [
+              {
+                action: "setState",
+                params: { statePath: "/form/country", value: "US" },
+              },
+            ],
+          },
+          children: [],
+        },
+        watcher: {
+          type: "Select",
+          props: { value: { $state: "/form/country" } },
+          watch: {
+            "/form/country": {
+              action: "loadCities",
+              params: { country: { $state: "/form/country" } },
+            },
+          },
+          children: [],
+        },
+      },
+    };
+
+    // Add watcher as a child of a wrapper so both render
+    const wrapperSpec: Spec = {
+      ...spec,
+      root: "wrapper",
+      elements: {
+        ...spec.elements,
+        wrapper: {
+          type: "Button",
+          props: { label: "wrapper" },
+          children: ["main", "watcher"],
+        },
+      },
+    };
+
+    // Use a Stack-like wrapper -- but since we only have Button/Text/Select
+    // stubs, we need a container. Let's add a simple Stack stub.
+    const Stack = ({
+      children,
+    }: ComponentRenderProps<Record<string, unknown>>) => {
+      return <div data-testid="stack">{children}</div>;
+    };
+    const reg = { ...registry, Stack };
+
+    const stackSpec: Spec = {
+      state: { form: { country: "" }, citiesLoaded: false },
+      root: "wrapper",
+      elements: {
+        wrapper: {
+          type: "Stack",
+          props: {},
+          children: ["btn", "watcher"],
+        },
+        btn: {
+          type: "Button",
+          props: { label: "Set Country" },
+          on: {
+            press: [
+              {
+                action: "setState",
+                params: { statePath: "/form/country", value: "US" },
+              },
+            ],
+          },
+          children: [],
+        },
+        watcher: {
+          type: "Select",
+          props: { value: { $state: "/form/country" } },
+          watch: {
+            "/form/country": {
+              action: "loadCities",
+              params: { country: { $state: "/form/country" } },
+            },
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider
+        registry={reg}
+        initialState={stackSpec.state}
+        handlers={{ loadCities }}
+      >
+        <Renderer spec={stackSpec} registry={reg} />
+        <StateProbe />
+      </JSONUIProvider>,
+    );
+
+    // Not called on initial render
+    expect(loadCities).not.toHaveBeenCalled();
+
+    // Change the watched state path
+    await act(async () => {
+      fireEvent.click(screen.getByTestId("btn"));
+    });
+
+    expect(loadCities).toHaveBeenCalledTimes(1);
+    expect(loadCities).toHaveBeenCalledWith(
+      expect.objectContaining({ country: "US" }),
+    );
+  });
+
+  it("fires multiple action bindings on the same watch path", async () => {
+    const action1 = vi.fn();
+    const action2 = vi.fn();
+
+    const Stack = ({
+      children,
+    }: ComponentRenderProps<Record<string, unknown>>) => <div>{children}</div>;
+    const reg = { ...registry, Stack };
+
+    const spec: Spec = {
+      state: { value: "a" },
+      root: "wrapper",
+      elements: {
+        wrapper: {
+          type: "Stack",
+          props: {},
+          children: ["btn", "watcher"],
+        },
+        btn: {
+          type: "Button",
+          props: { label: "Change" },
+          on: {
+            press: [
+              {
+                action: "setState",
+                params: { statePath: "/value", value: "b" },
+              },
+            ],
+          },
+          children: [],
+        },
+        watcher: {
+          type: "Text",
+          props: { text: { $state: "/value" } },
+          watch: {
+            "/value": [{ action: "action1" }, { action: "action2" }],
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider
+        registry={reg}
+        initialState={spec.state}
+        handlers={{ action1, action2 }}
+      >
+        <Renderer spec={spec} registry={reg} />
+      </JSONUIProvider>,
+    );
+
+    await act(async () => {
+      fireEvent.click(screen.getByTestId("btn"));
+    });
+
+    expect(action1).toHaveBeenCalledTimes(1);
+    expect(action2).toHaveBeenCalledTimes(1);
+  });
+});
+
+// =============================================================================
+// validateForm action
+// =============================================================================
+
+describe("validateForm action", () => {
+  it("writes { valid: false } when a required field is empty", async () => {
+    const Stack = ({
+      children,
+    }: ComponentRenderProps<Record<string, unknown>>) => <div>{children}</div>;
+    const reg = { ...registry, Stack };
+
+    const spec: Spec = {
+      state: { form: { email: "" }, result: null },
+      root: "wrapper",
+      elements: {
+        wrapper: {
+          type: "Stack",
+          props: {},
+          children: ["emailInput", "submitBtn"],
+        },
+        emailInput: {
+          type: "Input",
+          props: {
+            label: "Email",
+            value: { $bindState: "/form/email" },
+            checks: [{ type: "required", message: "Email is required" }],
+          },
+          children: [],
+        },
+        submitBtn: {
+          type: "Button",
+          props: { label: "Submit" },
+          on: {
+            press: [
+              {
+                action: "validateForm",
+                params: { statePath: "/result" },
+              },
+            ],
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider registry={reg} initialState={spec.state}>
+        <Renderer spec={spec} registry={reg} />
+        <StateProbe />
+      </JSONUIProvider>,
+    );
+
+    // Click submit with empty email
+    await act(async () => {
+      fireEvent.click(screen.getByTestId("btn"));
+    });
+
+    const state = getState();
+    expect(state.result).toEqual({ valid: false });
+  });
+
+  it("writes { valid: true } when all fields pass validation", async () => {
+    const Stack = ({
+      children,
+    }: ComponentRenderProps<Record<string, unknown>>) => <div>{children}</div>;
+    const reg = { ...registry, Stack };
+
+    const spec: Spec = {
+      state: { form: { email: "test@example.com" }, result: null },
+      root: "wrapper",
+      elements: {
+        wrapper: {
+          type: "Stack",
+          props: {},
+          children: ["emailInput", "submitBtn"],
+        },
+        emailInput: {
+          type: "Input",
+          props: {
+            label: "Email",
+            value: { $bindState: "/form/email" },
+            checks: [{ type: "required", message: "Email is required" }],
+          },
+          children: [],
+        },
+        submitBtn: {
+          type: "Button",
+          props: { label: "Submit" },
+          on: {
+            press: [
+              {
+                action: "validateForm",
+                params: { statePath: "/result" },
+              },
+            ],
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider registry={reg} initialState={spec.state}>
+        <Renderer spec={spec} registry={reg} />
+        <StateProbe />
+      </JSONUIProvider>,
+    );
+
+    await act(async () => {
+      fireEvent.click(screen.getByTestId("btn"));
+    });
+
+    const state = getState();
+    expect(state.result).toEqual({ valid: true });
+  });
+
+  it("defaults to /formValidation when no statePath is provided", async () => {
+    const Stack = ({
+      children,
+    }: ComponentRenderProps<Record<string, unknown>>) => <div>{children}</div>;
+    const reg = { ...registry, Stack };
+
+    const spec: Spec = {
+      state: { form: { name: "filled" } },
+      root: "wrapper",
+      elements: {
+        wrapper: {
+          type: "Stack",
+          props: {},
+          children: ["nameInput", "submitBtn"],
+        },
+        nameInput: {
+          type: "Input",
+          props: {
+            label: "Name",
+            value: { $bindState: "/form/name" },
+            checks: [{ type: "required", message: "Required" }],
+          },
+          children: [],
+        },
+        submitBtn: {
+          type: "Button",
+          props: { label: "Submit" },
+          on: {
+            press: [{ action: "validateForm" }],
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider registry={reg} initialState={spec.state}>
+        <Renderer spec={spec} registry={reg} />
+        <StateProbe />
+      </JSONUIProvider>,
+    );
+
+    await act(async () => {
+      fireEvent.click(screen.getByTestId("btn"));
+    });
+
+    const state = getState();
+    expect(state.formValidation).toEqual({ valid: true });
+  });
+});
+
+// =============================================================================
+// Select validate-on-change timing (#151)
+// =============================================================================
+
+describe("Select validate-on-change sees the new value, not the stale value", () => {
+  const Stack = ({
+    children,
+  }: ComponentRenderProps<Record<string, unknown>>) => <div>{children}</div>;
+
+  const regWithSelect = {
+    ...registry,
+    Stack,
+    Select: ValidatedSelect,
+  };
+
+  it("does not show 'required' error when selecting the first value", async () => {
+    const spec: Spec = {
+      state: { form: { country: "" } },
+      root: "wrapper",
+      elements: {
+        wrapper: {
+          type: "Stack",
+          props: {},
+          children: ["countrySelect"],
+        },
+        countrySelect: {
+          type: "Select",
+          props: {
+            label: "Country",
+            name: "country",
+            options: ["US", "Canada", "UK"],
+            placeholder: "Choose a country",
+            value: { $bindState: "/form/country" },
+            checks: [{ type: "required", message: "Country is required" }],
+            validateOn: "change",
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider registry={regWithSelect} initialState={spec.state}>
+        <Renderer spec={spec} registry={regWithSelect} />
+        <StateProbe />
+      </JSONUIProvider>,
+    );
+
+    // Select "US" for the first time (from empty)
+    await act(async () => {
+      fireEvent.change(screen.getByTestId("select-country"), {
+        target: { value: "US" },
+      });
+    });
+
+    // The value should be set in state
+    const state = getState();
+    expect((state.form as Record<string, unknown>).country).toBe("US");
+
+    // No validation error should appear -- "US" is non-empty
+    expect(screen.queryByTestId("select-error-country")).toBeNull();
+  });
+
+  it("does not show 'required' error when selecting the first city after country change resets it", async () => {
+    const spec: Spec = {
+      state: {
+        form: { country: "US", city: "" },
+        availableCities: ["New York", "Chicago"],
+      },
+      root: "wrapper",
+      elements: {
+        wrapper: {
+          type: "Stack",
+          props: {},
+          children: ["citySelect"],
+        },
+        citySelect: {
+          type: "Select",
+          props: {
+            label: "City",
+            name: "city",
+            options: ["New York", "Chicago"],
+            placeholder: "Select a city",
+            value: { $bindState: "/form/city" },
+            checks: [{ type: "required", message: "City is required" }],
+            validateOn: "change",
+          },
+          children: [],
+        },
+      },
+    };
+
+    render(
+      <JSONUIProvider registry={regWithSelect} initialState={spec.state}>
+        <Renderer spec={spec} registry={regWithSelect} />
+        <StateProbe />
+      </JSONUIProvider>,
+    );
+
+    // Select "New York" for the first time (from empty)
+    await act(async () => {
+      fireEvent.change(screen.getByTestId("select-city"), {
+        target: { value: "New York" },
+      });
+    });
+
+    const state = getState();
+    expect((state.form as Record<string, unknown>).city).toBe("New York");
+
+    // No validation error should appear
+    expect(screen.queryByTestId("select-error-city")).toBeNull();
+  });
+});

packages/react/src/index.ts

@@ -30,6 +30,7 @@ export {
 export {
   ValidationProvider,
   useValidation,
+  useOptionalValidation,
   useFieldValidation,
   type ValidationContextValue,
   type ValidationProviderProps,

packages/react/src/renderer.tsx

@@ -5,7 +5,9 @@ import React, {
   type ErrorInfo,
   type ReactNode,
   useCallback,
+  useEffect,
   useMemo,
+  useRef,
 } from "react";
 import type {
   UIElement,
@@ -14,6 +16,7 @@ import type {
   Catalog,
   SchemaDefinition,
   StateStore,
+  ComputedFunction,
 } from "@json-render/core";
 import {
   resolveElementProps,
@@ -136,6 +139,19 @@ class ElementErrorBoundary extends React.Component<
   }
 }
 
+// ---------------------------------------------------------------------------
+// FunctionsContext – provides $computed functions to the element tree
+// ---------------------------------------------------------------------------
+
+const EMPTY_FUNCTIONS: Record<string, ComputedFunction> = {};
+
+const FunctionsContext =
+  React.createContext<Record<string, ComputedFunction>>(EMPTY_FUNCTIONS);
+
+function useFunctions(): Record<string, ComputedFunction> {
+  return React.useContext(FunctionsContext);
+}
+
 interface ElementRendererProps {
   element: UIElement;
   spec: Spec;
@@ -158,21 +174,22 @@ const ElementRenderer = React.memo(function ElementRenderer({
   const repeatScope = useRepeatScope();
   const { ctx } = useVisibility();
   const { execute } = useActions();
-  const { getSnapshot } = useStateStore();
+  const { getSnapshot, state: watchState } = useStateStore();
+  const functions = useFunctions();
 
-  // Build context with repeat scope (used for both visibility and props)
-  const fullCtx: PropResolutionContext = useMemo(
-    () =>
-      repeatScope
-        ? {
-            ...ctx,
-            repeatItem: repeatScope.item,
-            repeatIndex: repeatScope.index,
-            repeatBasePath: repeatScope.basePath,
-          }
-        : ctx,
-    [ctx, repeatScope],
-  );
+  // Build context with repeat scope and $computed functions
+  const fullCtx: PropResolutionContext = useMemo(() => {
+    const base: PropResolutionContext = repeatScope
+      ? {
+          ...ctx,
+          repeatItem: repeatScope.item,
+          repeatIndex: repeatScope.index,
+          repeatBasePath: repeatScope.basePath,
+        }
+      : { ...ctx };
+    base.functions = functions;
+    return base;
+  }, [ctx, repeatScope, functions]);
 
   // Evaluate visibility (now supports $item/$index inside repeat scopes)
   const isVisible =
@@ -227,6 +244,85 @@ const ElementRenderer = React.memo(function ElementRenderer({
     [onBindings, emit],
   );
 
+  // Watch effect: fire actions when watched state paths change.
+  // Must be called before any early return to satisfy Rules of Hooks.
+  //
+  // Two refs serve distinct roles:
+  // - `stableWatchRef` (useMemo): holds the last emitted values object so we
+  //   can return the same reference when watched values haven't changed,
+  //   preventing the downstream useEffect from firing on unrelated state updates.
+  // - `prevWatchValues` (useEffect): tracks the previous watched-values snapshot
+  //   for change detection. Starts as `null` to skip the initial mount.
+  const watchConfig = element.watch;
+  const prevWatchValues = useRef<Record<string, unknown> | null>(null);
+  const stableWatchRef = useRef<Record<string, unknown> | undefined>(undefined);
+
+  const watchedValues = useMemo(() => {
+    if (!watchConfig) return undefined;
+    const values: Record<string, unknown> = {};
+    for (const path of Object.keys(watchConfig)) {
+      values[path] = getByPath(watchState, path);
+    }
+    const prev = stableWatchRef.current;
+    if (prev) {
+      const keys = Object.keys(values);
+      if (
+        keys.length === Object.keys(prev).length &&
+        keys.every((k) => values[k] === prev[k])
+      ) {
+        return prev;
+      }
+    }
+    stableWatchRef.current = values;
+    return values;
+  }, [watchConfig, watchState]);
+
+  useEffect(() => {
+    if (!watchConfig || !watchedValues) return;
+    const paths = Object.keys(watchConfig);
+    if (paths.length === 0) return;
+
+    const prev = prevWatchValues.current;
+    prevWatchValues.current = watchedValues;
+
+    // Skip the initial mount — only fire on changes
+    if (prev === null) return;
+
+    let cancelled = false;
+    void (async () => {
+      for (const path of paths) {
+        if (cancelled) break;
+        if (watchedValues[path] !== prev[path]) {
+          const binding = watchConfig[path];
+          if (!binding) continue;
+          const bindings = Array.isArray(binding) ? binding : [binding];
+          for (const b of bindings) {
+            if (cancelled) break;
+            if (!b.params) {
+              await execute(b);
+              if (cancelled) break;
+              continue;
+            }
+            const liveCtx: PropResolutionContext = {
+              ...fullCtx,
+              stateModel: getSnapshot(),
+            };
+            const resolved: Record<string, unknown> = {};
+            for (const [key, val] of Object.entries(b.params)) {
+              resolved[key] = resolveActionParam(val, liveCtx);
+            }
+            await execute({ ...b, params: resolved });
+            if (cancelled) break;
+          }
+        }
+      }
+    })().catch(console.error);
+
+    return () => {
+      cancelled = true;
+    };
+  }, [watchConfig, watchedValues, execute, fullCtx, getSnapshot]);
+
   // Don't render if not visible
   if (!isVisible) {
     return null;
@@ -419,6 +515,8 @@ export interface JSONUIProviderProps {
     string,
     (value: unknown, args?: Record<string, unknown>) => boolean
   >;
+  /** Named functions for `$computed` expressions in props */
+  functions?: Record<string, ComputedFunction>;
   /** Callback when state changes (uncontrolled mode) */
   onStateChange?: (changes: Array<{ path: string; value: unknown }>) => void;
   children: ReactNode;
@@ -434,6 +532,7 @@ export function JSONUIProvider({
   handlers,
   navigate,
   validationFunctions,
+  functions,
   onStateChange,
   children,
 }: JSONUIProviderProps) {
@@ -444,12 +543,14 @@ export function JSONUIProvider({
       onStateChange={onStateChange}
     >
       <VisibilityProvider>
-        <ActionProvider handlers={handlers} navigate={navigate}>
-          <ValidationProvider customFunctions={validationFunctions}>
-            {children}
-            <ConfirmationDialogManager />
-          </ValidationProvider>
-        </ActionProvider>
+        <ValidationProvider customFunctions={validationFunctions}>
+          <ActionProvider handlers={handlers} navigate={navigate}>
+            <FunctionsContext.Provider value={functions ?? EMPTY_FUNCTIONS}>
+              {children}
+              <ConfirmationDialogManager />
+            </FunctionsContext.Provider>
+          </ActionProvider>
+        </ValidationProvider>
       </VisibilityProvider>
     </StateProvider>
   );
@@ -650,6 +751,8 @@ export interface CreateRendererProps {
   onAction?: (actionName: string, params?: Record<string, unknown>) => void;
   /** Callback when state changes (uncontrolled mode) */
   onStateChange?: (changes: Array<{ path: string; value: unknown }>) => void;
+  /** Named functions for `$computed` expressions in props */
+  functions?: Record<string, ComputedFunction>;
   /** Whether the spec is currently loading/streaming */
   loading?: boolean;
   /** Fallback component for unknown types */
@@ -703,6 +806,7 @@ export function createRenderer<
     state,
     onAction,
     onStateChange,
+    functions,
     loading,
     fallback,
   }: CreateRendererProps) {
@@ -730,17 +834,19 @@ export function createRenderer<
         onStateChange={onStateChange}
       >
         <VisibilityProvider>
-          <ActionProvider handlers={actionHandlers}>
-            <ValidationProvider>
-              <Renderer
-                spec={spec}
-                registry={registry}
-                loading={loading}
-                fallback={fallback}
-              />
-              <ConfirmationDialogManager />
-            </ValidationProvider>
-          </ActionProvider>
+          <ValidationProvider>
+            <ActionProvider handlers={actionHandlers}>
+              <FunctionsContext.Provider value={functions ?? EMPTY_FUNCTIONS}>
+                <Renderer
+                  spec={spec}
+                  registry={registry}
+                  loading={loading}
+                  fallback={fallback}
+                />
+                <ConfirmationDialogManager />
+              </FunctionsContext.Provider>
+            </ActionProvider>
+          </ValidationProvider>
         </VisibilityProvider>
       </StateProvider>
     );

packages/react/src/schema.ts

@@ -67,6 +67,11 @@ export const schema = defineSchema(
         description:
           "Remove an item from an array in state by index. Params: { statePath: string, index: number }",
       },
+      {
+        name: "validateForm",
+        description:
+          "Validate all registered form fields and write the result to state. Params: { statePath?: string }. Defaults to /formValidation. Result: { valid: boolean }.",
+      },
     ],
     defaultRules: [
       // Element integrity

packages/react/tsup.config.ts

@@ -3,8 +3,9 @@ import { defineConfig } from "tsup";
 export default defineConfig({
   entry: ["src/index.ts", "src/schema.ts"],
   format: ["cjs", "esm"],
-  dts: true,
+  dts: { resolve: ["@internal/react-state"] },
   sourcemap: true,
   clean: true,
+  noExternal: ["@internal/react-state"],
   external: ["react", "react-dom", "@json-render/core"],
 });

packages/redux/CHANGELOG.md

@@ -1,5 +1,11 @@
 # @json-render/redux
 
+## 0.9.1
+
+### Patch Changes
+
+- @json-render/core@0.9.1
+
 ## 0.9.0
 
 ### Minor Changes

packages/redux/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@json-render/redux",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "license": "Apache-2.0",
   "description": "Redux adapter for json-render StateStore",
   "keywords": [

packages/remotion/CHANGELOG.md

@@ -1,5 +1,11 @@
 # @json-render/remotion
 
+## 0.9.1
+
+### Patch Changes
+
+- @json-render/core@0.9.1
+
 ## 0.9.0
 
 ### Minor Changes

packages/remotion/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@json-render/remotion",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "license": "Apache-2.0",
   "description": "Remotion renderer for @json-render/core. JSON becomes video compositions.",
   "keywords": [

packages/shadcn/CHANGELOG.md

@@ -1,5 +1,13 @@
 # @json-render/shadcn
 
+## 0.9.1
+
+### Patch Changes
+
+- Updated dependencies [b103676]
+  - @json-render/react@0.9.1
+  - @json-render/core@0.9.1
+
 ## 0.9.0
 
 ### Minor Changes

packages/shadcn/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@json-render/shadcn",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "license": "Apache-2.0",
   "description": "shadcn/ui component library for @json-render/core. JSON becomes beautiful Tailwind-styled React components.",
   "keywords": [

packages/shadcn/src/catalog.ts

@@ -1,5 +1,21 @@
 import { z } from "zod";
 
+// =============================================================================
+// Shared validation schemas used across form components
+// =============================================================================
+
+const validationCheckSchema = z
+  .array(
+    z.object({
+      type: z.string(),
+      message: z.string(),
+      args: z.record(z.string(), z.unknown()).optional(),
+    }),
+  )
+  .nullable();
+
+const validateOnSchema = z.enum(["change", "blur", "submit"]).nullable();
+
 // =============================================================================
 // shadcn/ui Component Definitions
 // =============================================================================
@@ -272,19 +288,12 @@ export const shadcnComponentDefinitions = {
       type: z.enum(["text", "email", "password", "number"]).nullable(),
       placeholder: z.string().nullable(),
       value: z.string().nullable(),
-      checks: z
-        .array(
-          z.object({
-            type: z.string(),
-            message: z.string(),
-            args: z.record(z.string(), z.unknown()).optional(),
-          }),
-        )
-        .nullable(),
+      checks: validationCheckSchema,
+      validateOn: validateOnSchema,
     }),
     events: ["submit", "focus", "blur"],
     description:
-      "Text input field. Use { $bindState } on value for two-way binding. Use checks for validation (e.g. required, email, minLength).",
+      "Text input field. Use { $bindState } on value for two-way binding. Use checks for validation (e.g. required, email, minLength). validateOn controls timing (default: blur).",
     example: {
       label: "Email",
       name: "email",
@@ -300,18 +309,11 @@ export const shadcnComponentDefinitions = {
       placeholder: z.string().nullable(),
       rows: z.number().nullable(),
       value: z.string().nullable(),
-      checks: z
-        .array(
-          z.object({
-            type: z.string(),
-            message: z.string(),
-            args: z.record(z.string(), z.unknown()).optional(),
-          }),
-        )
-        .nullable(),
+      checks: validationCheckSchema,
+      validateOn: validateOnSchema,
     }),
     description:
-      "Multi-line text input. Use { $bindState } on value for binding. Use checks for validation.",
+      "Multi-line text input. Use { $bindState } on value for binding. Use checks for validation. validateOn controls timing (default: blur).",
   },
 
   Select: {
@@ -321,19 +323,12 @@ export const shadcnComponentDefinitions = {
       options: z.array(z.string()),
       placeholder: z.string().nullable(),
       value: z.string().nullable(),
-      checks: z
-        .array(
-          z.object({
-            type: z.string(),
-            message: z.string(),
-            args: z.record(z.string(), z.unknown()).optional(),
-          }),
-        )
-        .nullable(),
+      checks: validationCheckSchema,
+      validateOn: validateOnSchema,
     }),
     events: ["change"],
     description:
-      "Dropdown select input. Use { $bindState } on value for binding. Use checks for validation.",
+      "Dropdown select input. Use { $bindState } on value for binding. Use checks for validation. validateOn controls timing (default: change).",
   },
 
   Checkbox: {
@@ -341,9 +336,12 @@ export const shadcnComponentDefinitions = {
       label: z.string(),
       name: z.string(),
       checked: z.boolean().nullable(),
+      checks: validationCheckSchema,
+      validateOn: validateOnSchema,
     }),
     events: ["change"],
-    description: "Checkbox input. Use { $bindState } on checked for binding.",
+    description:
+      "Checkbox input. Use { $bindState } on checked for binding. Use checks for validation. validateOn controls timing (default: change).",
   },
 
   Radio: {
@@ -352,9 +350,12 @@ export const shadcnComponentDefinitions = {
       name: z.string(),
       options: z.array(z.string()),
       value: z.string().nullable(),
+      checks: validationCheckSchema,
+      validateOn: validateOnSchema,
     }),
     events: ["change"],
-    description: "Radio button group. Use { $bindState } on value for binding.",
+    description:
+      "Radio button group. Use { $bindState } on value for binding. Use checks for validation. validateOn controls timing (default: change).",
   },
 
   Switch: {
@@ -362,9 +363,12 @@ export const shadcnComponentDefinitions = {
       label: z.string(),
       name: z.string(),
       checked: z.boolean().nullable(),
+      checks: validationCheckSchema,
+      validateOn: validateOnSchema,
     }),
     events: ["change"],
-    description: "Toggle switch. Use { $bindState } on checked for binding.",
+    description:
+      "Toggle switch. Use { $bindState } on checked for binding. Use checks for validation. validateOn controls timing (default: change).",
   },
 
   Slider: {

packages/shadcn/src/components.tsx

@@ -664,11 +664,12 @@ export const shadcnComponents = {
     const isBound = !!bindings?.value;
     const value = isBound ? (boundValue ?? "") : localValue;
     const setValue = isBound ? setBoundValue : setLocalValue;
+    const validateOn = props.validateOn ?? "blur";
 
     const hasValidation = !!(bindings?.value && props.checks?.length);
     const { errors, validate } = useFieldValidation(
       bindings?.value ?? "",
-      hasValidation ? { checks: props.checks ?? [] } : undefined,
+      hasValidation ? { checks: props.checks ?? [], validateOn } : undefined,
     );
 
     return (
@@ -682,13 +683,16 @@ export const shadcnComponents = {
           type={props.type ?? "text"}
           placeholder={props.placeholder ?? ""}
           value={value}
-          onChange={(e) => setValue(e.target.value)}
+          onChange={(e) => {
+            setValue(e.target.value);
+            if (hasValidation && validateOn === "change") validate();
+          }}
           onKeyDown={(e) => {
             if (e.key === "Enter") emit("submit");
           }}
           onFocus={() => emit("focus")}
           onBlur={() => {
-            if (hasValidation) validate();
+            if (hasValidation && validateOn === "blur") validate();
             emit("blur");
           }}
         />
@@ -711,11 +715,12 @@ export const shadcnComponents = {
     const isBound = !!bindings?.value;
     const value = isBound ? (boundValue ?? "") : localValue;
     const setValue = isBound ? setBoundValue : setLocalValue;
+    const validateOn = props.validateOn ?? "blur";
 
     const hasValidation = !!(bindings?.value && props.checks?.length);
     const { errors, validate } = useFieldValidation(
       bindings?.value ?? "",
-      hasValidation ? { checks: props.checks ?? [] } : undefined,
+      hasValidation ? { checks: props.checks ?? [], validateOn } : undefined,
     );
 
     return (
@@ -729,9 +734,12 @@ export const shadcnComponents = {
           placeholder={props.placeholder ?? ""}
           rows={props.rows ?? 3}
           value={value}
-          onChange={(e) => setValue(e.target.value)}
+          onChange={(e) => {
+            setValue(e.target.value);
+            if (hasValidation && validateOn === "change") validate();
+          }}
           onBlur={() => {
-            if (hasValidation) validate();
+            if (hasValidation && validateOn === "blur") validate();
           }}
         />
         {errors.length > 0 && (
@@ -758,11 +766,12 @@ export const shadcnComponents = {
     const options = rawOptions.map((opt) =>
       typeof opt === "string" ? opt : String(opt ?? ""),
     );
+    const validateOn = props.validateOn ?? "change";
 
     const hasValidation = !!(bindings?.value && props.checks?.length);
     const { errors, validate } = useFieldValidation(
       bindings?.value ?? "",
-      hasValidation ? { checks: props.checks ?? [] } : undefined,
+      hasValidation ? { checks: props.checks ?? [], validateOn } : undefined,
     );
 
     return (
@@ -772,7 +781,8 @@ export const shadcnComponents = {
           value={value}
           onValueChange={(v) => {
             setValue(v);
-            if (hasValidation) validate();
+            // Select has no native blur event, so only validate on "change"
+            if (hasValidation && validateOn === "change") validate();
             emit("change");
           }}
         >
@@ -808,19 +818,32 @@ export const shadcnComponents = {
     const checked = isBound ? (boundChecked ?? false) : localChecked;
     const setChecked = isBound ? setBoundChecked : setLocalChecked;
 
+    const validateOn = props.validateOn ?? "change";
+    const hasValidation = !!(bindings?.checked && props.checks?.length);
+    const { errors, validate } = useFieldValidation(
+      bindings?.checked ?? "",
+      hasValidation ? { checks: props.checks ?? [], validateOn } : undefined,
+    );
+
     return (
-      <div className="flex items-center space-x-2">
-        <Checkbox
-          id={props.name ?? undefined}
-          checked={checked}
-          onCheckedChange={(c) => {
-            setChecked(c === true);
-            emit("change");
-          }}
-        />
-        <Label htmlFor={props.name ?? undefined} className="cursor-pointer">
-          {props.label}
-        </Label>
+      <div className="space-y-1">
+        <div className="flex items-center space-x-2">
+          <Checkbox
+            id={props.name ?? undefined}
+            checked={checked}
+            onCheckedChange={(c) => {
+              setChecked(c === true);
+              if (hasValidation && validateOn === "change") validate();
+              emit("change");
+            }}
+          />
+          <Label htmlFor={props.name ?? undefined} className="cursor-pointer">
+            {props.label}
+          </Label>
+        </div>
+        {errors.length > 0 && (
+          <p className="text-sm text-destructive">{errors[0]}</p>
+        )}
       </div>
     );
   },
@@ -843,6 +866,13 @@ export const shadcnComponents = {
     const value = isBound ? (boundValue ?? "") : localValue;
     const setValue = isBound ? setBoundValue : setLocalValue;
 
+    const validateOn = props.validateOn ?? "change";
+    const hasValidation = !!(bindings?.value && props.checks?.length);
+    const { errors, validate } = useFieldValidation(
+      bindings?.value ?? "",
+      hasValidation ? { checks: props.checks ?? [], validateOn } : undefined,
+    );
+
     return (
       <div className="space-y-2">
         {props.label && <Label>{props.label}</Label>}
@@ -850,6 +880,7 @@ export const shadcnComponents = {
           value={value}
           onValueChange={(v) => {
             setValue(v);
+            if (hasValidation && validateOn === "change") validate();
             emit("change");
           }}
         >
@@ -868,6 +899,9 @@ export const shadcnComponents = {
             </div>
           ))}
         </RadioGroup>
+        {errors.length > 0 && (
+          <p className="text-sm text-destructive">{errors[0]}</p>
+        )}
       </div>
     );
   },
@@ -886,19 +920,32 @@ export const shadcnComponents = {
     const checked = isBound ? (boundChecked ?? false) : localChecked;
     const setChecked = isBound ? setBoundChecked : setLocalChecked;
 
+    const validateOn = props.validateOn ?? "change";
+    const hasValidation = !!(bindings?.checked && props.checks?.length);
+    const { errors, validate } = useFieldValidation(
+      bindings?.checked ?? "",
+      hasValidation ? { checks: props.checks ?? [], validateOn } : undefined,
+    );
+
     return (
-      <div className="flex items-center justify-between space-x-2">
-        <Label htmlFor={props.name ?? undefined} className="cursor-pointer">
-          {props.label}
-        </Label>
-        <Switch
-          id={props.name ?? undefined}
-          checked={checked}
-          onCheckedChange={(c) => {
-            setChecked(c);
-            emit("change");
-          }}
-        />
+      <div className="space-y-1">
+        <div className="flex items-center justify-between space-x-2">
+          <Label htmlFor={props.name ?? undefined} className="cursor-pointer">
+            {props.label}
+          </Label>
+          <Switch
+            id={props.name ?? undefined}
+            checked={checked}
+            onCheckedChange={(c) => {
+              setChecked(c);
+              if (hasValidation && validateOn === "change") validate();
+              emit("change");
+            }}
+          />
+        </div>
+        {errors.length > 0 && (
+          <p className="text-sm text-destructive">{errors[0]}</p>
+        )}
       </div>
     );
   },

packages/typescript-config/vue-library.json

@@ -0,0 +1,8 @@
+{
+  "$schema": "https://json.schemastore.org/tsconfig",
+  "extends": "./base.json",
+  "compilerOptions": {
+    "jsx": "preserve",
+    "jsxImportSource": "vue"
+  }
+}

packages/vue/README.md

@@ -0,0 +1,275 @@
+# @json-render/vue
+
+Vue 3 renderer for json-render. Turn JSON specs into Vue components with data binding, visibility, and actions.
+
+## Installation
+
+```bash
+npm install @json-render/vue @json-render/core zod
+```
+
+## Quick Start
+
+### 1. Create a Catalog
+
+```typescript
+import { defineCatalog } from "@json-render/core";
+import { schema } from "@json-render/vue/schema";
+import { z } from "zod";
+
+export const catalog = defineCatalog(schema, {
+  components: {
+    Card: {
+      props: z.object({
+        title: z.string(),
+        description: z.string().nullable(),
+      }),
+      description: "A card container",
+    },
+    Button: {
+      props: z.object({
+        label: z.string(),
+      }),
+      description: "A clickable button",
+    },
+    Input: {
+      props: z.object({
+        value: z.union([z.string(), z.record(z.unknown())]).nullable(),
+        label: z.string(),
+        placeholder: z.string().nullable(),
+      }),
+      description: "Text input field with optional value binding",
+    },
+  },
+  actions: {
+    submit: { description: "Submit the form" },
+  },
+});
+```
+
+### 2. Define Component Implementations
+
+```typescript
+import { h } from "vue";
+import { defineRegistry, useBoundProp } from "@json-render/vue";
+import { catalog } from "./catalog";
+
+export const { registry } = defineRegistry(catalog, {
+  components: {
+    Card: ({ props, children }) =>
+      h("div", { class: "card" }, [
+        h("h3", null, props.title),
+        props.description && h("p", null, props.description),
+        children,
+      ]),
+    Button: ({ props, emit }) =>
+      h("button", { onClick: () => emit("press") }, props.label),
+    Input: ({ props, bindings }) => {
+      const [value, setValue] = useBoundProp(props.value, bindings?.value);
+      return h("label", null, [
+        props.label,
+        h("input", {
+          placeholder: props.placeholder ?? "",
+          value: value ?? "",
+          onInput: (e: Event) =>
+            setValue((e.target as HTMLInputElement).value),
+        }),
+      ]);
+    },
+  },
+  actions: {
+    submit: async (_params, _setState) => {
+      console.log("Form submitted");
+    },
+  },
+});
+```
+
+### 3. Render a Spec
+
+```vue
+<script setup lang="ts">
+import { JSONUIProvider, Renderer } from "@json-render/vue";
+import { registry } from "./registry";
+
+const spec = {
+  root: "card",
+  state: { name: "" },
+  elements: {
+    card: {
+      type: "Card",
+      props: { title: "Hello", description: null },
+      children: ["input", "btn"],
+    },
+    input: {
+      type: "Input",
+      props: {
+        label: "Name",
+        placeholder: "Enter your name",
+        value: { $bindState: "/name" },
+      },
+    },
+    btn: {
+      type: "Button",
+      props: { label: "Submit" },
+      on: { press: { action: "submit" } },
+    },
+  },
+};
+</script>
+
+<template>
+  <JSONUIProvider :registry="registry" :initial-state="spec.state ?? {}">
+    <Renderer :spec="spec" :registry="registry" />
+  </JSONUIProvider>
+</template>
+```
+
+## Spec Format
+
+The spec is a flat map of elements. Each element references its children by key:
+
+```json
+{
+  "root": "card",
+  "state": { "count": 0 },
+  "elements": {
+    "card": {
+      "type": "Card",
+      "props": { "title": "Counter" },
+      "children": ["display", "increment"]
+    },
+    "display": {
+      "type": "Text",
+      "props": { "text": { "$state": "/count" } }
+    },
+    "increment": {
+      "type": "Button",
+      "props": { "label": "+1" },
+      "on": {
+        "press": {
+          "action": "setState",
+          "params": { "statePath": "/count", "value": 1 }
+        }
+      }
+    }
+  }
+}
+```
+
+## Composables
+
+### `useStateStore()`
+
+Access the state context inside any component rendered within a `JSONUIProvider`.
+
+```typescript
+import { useStateStore } from "@json-render/vue";
+
+const { state, get, set, getSnapshot } = useStateStore();
+```
+
+### `useBoundProp(propValue, bindingPath)`
+
+Two-way binding helper for `$bindState` / `$bindItem` expressions.
+
+```typescript
+import { useBoundProp } from "@json-render/vue";
+
+const [value, setValue] = useBoundProp<string>(props.value, bindings?.value);
+```
+
+### `useVisibility()`
+
+Evaluate visibility conditions.
+
+```typescript
+import { useVisibility } from "@json-render/vue";
+
+const { isVisible, ctx } = useVisibility();
+```
+
+### `useActions()`
+
+Access action execution.
+
+```typescript
+import { useActions } from "@json-render/vue";
+
+const { execute, loadingActions } = useActions();
+```
+
+### `useFieldValidation(path, config)`
+
+Field-level validation.
+
+```typescript
+import { useFieldValidation } from "@json-render/vue";
+
+const { errors, isValid, validate, touch } = useFieldValidation("/email", {
+  checks: [{ type: "required", message: "Email is required" }],
+});
+```
+
+## Provider Components
+
+All providers are renderless components that use Vue's `provide`/`inject`:
+
+- **`StateProvider`** -- Manages state model with `createStateStore` from core
+- **`VisibilityProvider`** -- Evaluates visibility conditions against state
+- **`ValidationProvider`** -- Handles form validation
+- **`ActionProvider`** -- Executes action bindings (setState, pushState, custom actions)
+- **`JSONUIProvider`** -- Composes all of the above into a single provider
+
+## Dynamic Prop Expressions
+
+Props support dynamic expressions that resolve against state:
+
+| Expression | Description |
+|---|---|
+| `{ "$state": "/path" }` | Read a value from state |
+| `{ "$bindState": "/path" }` | Two-way binding to state |
+| `{ "$item": "field" }` | Read from current repeat item |
+| `{ "$bindItem": "field" }` | Two-way bind to repeat item field |
+| `{ "$index": true }` | Current repeat index |
+| `{ "$cond": ..., "$then": ..., "$else": ... }` | Conditional value |
+| `{ "$computed": "fnName", "args": {...} }` | Computed function |
+| `{ "$template": "Hello ${/name}" }` | String interpolation |
+
+## Built-in Actions
+
+| Action | Description |
+|---|---|
+| `setState` | Set a value at a state path |
+| `pushState` | Append to an array in state |
+| `removeState` | Remove an item from an array by index |
+| `validateForm` | Validate all registered fields |
+
+## Key Exports
+
+```typescript
+// Renderer
+export { Renderer, JSONUIProvider, defineRegistry, createRenderer, useBoundProp };
+
+// Composables
+export { useStateStore, useStateValue };
+export { useVisibility, useIsVisible };
+export { useActions, useAction };
+export { useValidation, useFieldValidation };
+export { useRepeatScope };
+
+// Provider components
+export { StateProvider, VisibilityProvider, ActionProvider, ValidationProvider };
+export { RepeatScopeProvider };
+
+// Schema
+export { schema };
+
+// Types
+export type {
+  ComponentRenderProps, ComponentRenderer, ComponentRegistry,
+  RendererProps, JSONUIProviderProps, CreateRendererProps,
+  BaseComponentProps, ComponentContext, ComponentFn,
+  EventHandle, SetState, StateModel,
+};
+```

packages/vue/package.json

@@ -0,0 +1,42 @@
+{
+  "name": "@json-render/vue",
+  "version": "0.1.0",
+  "license": "Apache-2.0",
+  "description": "Vue renderer for @json-render/core. JSON becomes Vue components.",
+  "type": "module",
+  "main": "./dist/index.cjs",
+  "module": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js",
+      "require": "./dist/index.cjs"
+    },
+    "./schema": {
+      "types": "./dist/schema.d.ts",
+      "import": "./dist/schema.js",
+      "require": "./dist/schema.cjs"
+    }
+  },
+  "files": [
+    "dist"
+  ],
+  "scripts": {
+    "build": "tsup",
+    "dev": "tsup --watch",
+    "check-types": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@json-render/core": "workspace:*"
+  },
+  "devDependencies": {
+    "@internal/typescript-config": "workspace:*",
+    "tsup": "^8.5.1",
+    "typescript": "^5.7.2",
+    "vue": "^3.5.29"
+  },
+  "peerDependencies": {
+    "vue": "^3.5.0"
+  }
+}

packages/vue/src/catalog-types.ts

@@ -0,0 +1,65 @@
+import type { VNode } from "vue";
+import type {
+  Catalog,
+  InferCatalogComponents,
+  InferCatalogActions,
+  InferComponentProps,
+  InferActionParams,
+  StateModel,
+} from "@json-render/core";
+
+export type { StateModel };
+
+export type SetState = (
+  updater: (prev: Record<string, unknown>) => Record<string, unknown>,
+) => void;
+
+export interface EventHandle {
+  emit: () => void;
+  shouldPreventDefault: boolean;
+  bound: boolean;
+}
+
+export interface BaseComponentProps<P = Record<string, unknown>> {
+  props: P;
+  children?: VNode[];
+  emit: (event: string) => void;
+  on: (event: string) => EventHandle;
+  bindings?: Record<string, string>;
+  loading?: boolean;
+}
+
+export interface ComponentContext<
+  C extends Catalog,
+  K extends keyof InferCatalogComponents<C>,
+> extends BaseComponentProps<InferComponentProps<C, K>> {}
+
+export type ComponentFn<
+  C extends Catalog,
+  K extends keyof InferCatalogComponents<C>,
+> = (ctx: ComponentContext<C, K>) => VNode | VNode[] | null;
+
+export type Components<C extends Catalog> = {
+  [K in keyof InferCatalogComponents<C>]: ComponentFn<C, K>;
+};
+
+export type ActionFn<
+  C extends Catalog,
+  K extends keyof InferCatalogActions<C>,
+> = (
+  params: InferActionParams<C, K> | undefined,
+  setState: SetState,
+  state: StateModel,
+) => Promise<void>;
+
+export type Actions<C extends Catalog> = {
+  [K in keyof InferCatalogActions<C>]: ActionFn<C, K>;
+};
+
+export type CatalogHasActions<C extends Catalog> = [
+  InferCatalogActions<C>,
+] extends [never]
+  ? false
+  : [keyof InferCatalogActions<C>] extends [never]
+    ? false
+    : true;

packages/vue/src/composables/actions.test.ts

@@ -0,0 +1,216 @@
+import { describe, it, expect, vi } from "vitest";
+import { defineComponent, h, createApp, nextTick } from "vue";
+import { ActionProvider, useActions } from "./actions.js";
+import { StateProvider, useStateStore } from "./state.js";
+import { VisibilityProvider } from "./visibility.js";
+import { ValidationProvider } from "./validation.js";
+
+function runInProviders<T>(
+  initialState: Record<string, unknown>,
+  fn: () => T,
+  handlers?: Record<string, (...args: unknown[]) => void>,
+): T {
+  let result: T | undefined;
+
+  const Inner = defineComponent({
+    setup() {
+      result = fn();
+      return () => null;
+    },
+  });
+
+  const App = defineComponent({
+    setup() {
+      return () =>
+        h(StateProvider, { initialState }, () =>
+          h(VisibilityProvider, null, () =>
+            h(ValidationProvider, null, () =>
+              h(ActionProvider, { handlers: handlers ?? {} }, () => h(Inner)),
+            ),
+          ),
+        );
+    },
+  });
+
+  const container = document.createElement("div");
+  const app = createApp(App);
+  app.mount(container);
+  app.unmount();
+
+  return result!;
+}
+
+describe("useActions", () => {
+  it("provides execute function", () => {
+    const ctx = runInProviders({}, () => useActions());
+    expect(typeof ctx.execute).toBe("function");
+  });
+
+  it("provides confirm and cancel functions", () => {
+    const ctx = runInProviders({}, () => useActions());
+    expect(typeof ctx.confirm).toBe("function");
+    expect(typeof ctx.cancel).toBe("function");
+  });
+});
+
+describe("action execution", () => {
+  it("executes setState action", async () => {
+    let storeCtx: ReturnType<typeof useStateStore> | undefined;
+    let actionsCtx: ReturnType<typeof useActions> | undefined;
+
+    const Inner = defineComponent({
+      setup() {
+        storeCtx = useStateStore();
+        actionsCtx = useActions();
+        return () => null;
+      },
+    });
+
+    const App = defineComponent({
+      setup() {
+        return () =>
+          h(StateProvider, { initialState: { count: 0 } }, () =>
+            h(VisibilityProvider, null, () =>
+              h(ValidationProvider, null, () =>
+                h(ActionProvider, { handlers: {} }, () => h(Inner)),
+              ),
+            ),
+          );
+      },
+    });
+
+    const container = document.createElement("div");
+    const app = createApp(App);
+    app.mount(container);
+
+    await actionsCtx!.execute({
+      action: "setState",
+      params: { statePath: "/count", value: 42 },
+    });
+
+    expect(storeCtx!.get("/count")).toBe(42);
+
+    app.unmount();
+  });
+
+  it("executes pushState action", async () => {
+    let storeCtx: ReturnType<typeof useStateStore> | undefined;
+    let actionsCtx: ReturnType<typeof useActions> | undefined;
+
+    const Inner = defineComponent({
+      setup() {
+        storeCtx = useStateStore();
+        actionsCtx = useActions();
+        return () => null;
+      },
+    });
+
+    const App = defineComponent({
+      setup() {
+        return () =>
+          h(StateProvider, { initialState: { items: ["a"] } }, () =>
+            h(VisibilityProvider, null, () =>
+              h(ValidationProvider, null, () =>
+                h(ActionProvider, { handlers: {} }, () => h(Inner)),
+              ),
+            ),
+          );
+      },
+    });
+
+    const container = document.createElement("div");
+    const app = createApp(App);
+    app.mount(container);
+
+    await actionsCtx!.execute({
+      action: "pushState",
+      params: { statePath: "/items", value: "b" },
+    });
+
+    expect(storeCtx!.get("/items")).toEqual(["a", "b"]);
+
+    app.unmount();
+  });
+
+  it("executes removeState action", async () => {
+    let storeCtx: ReturnType<typeof useStateStore> | undefined;
+    let actionsCtx: ReturnType<typeof useActions> | undefined;
+
+    const Inner = defineComponent({
+      setup() {
+        storeCtx = useStateStore();
+        actionsCtx = useActions();
+        return () => null;
+      },
+    });
+
+    const App = defineComponent({
+      setup() {
+        return () =>
+          h(StateProvider, { initialState: { items: ["a", "b", "c"] } }, () =>
+            h(VisibilityProvider, null, () =>
+              h(ValidationProvider, null, () =>
+                h(ActionProvider, { handlers: {} }, () => h(Inner)),
+              ),
+            ),
+          );
+      },
+    });
+
+    const container = document.createElement("div");
+    const app = createApp(App);
+    app.mount(container);
+
+    await actionsCtx!.execute({
+      action: "removeState",
+      params: { statePath: "/items", index: 1 },
+    });
+
+    expect(storeCtx!.get("/items")).toEqual(["a", "c"]);
+
+    app.unmount();
+  });
+
+  it("warns when no handler is registered for custom action", async () => {
+    const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+
+    const actionsCtx = runInProviders({}, () => useActions());
+
+    // The provider is unmounted, but execute still runs synchronously for the warn path
+    // We need a mounted tree for this test
+    let actions: ReturnType<typeof useActions> | undefined;
+
+    const Inner = defineComponent({
+      setup() {
+        actions = useActions();
+        return () => null;
+      },
+    });
+
+    const App = defineComponent({
+      setup() {
+        return () =>
+          h(StateProvider, { initialState: {} }, () =>
+            h(VisibilityProvider, null, () =>
+              h(ValidationProvider, null, () =>
+                h(ActionProvider, { handlers: {} }, () => h(Inner)),
+              ),
+            ),
+          );
+      },
+    });
+
+    const container = document.createElement("div");
+    const app = createApp(App);
+    app.mount(container);
+
+    await actions!.execute({ action: "unknownAction" });
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      "No handler registered for action: unknownAction",
+    );
+
+    warnSpy.mockRestore();
+    app.unmount();
+  });
+});

packages/vue/src/composables/actions.ts

@@ -0,0 +1,456 @@
+import {
+  defineComponent,
+  h,
+  provide,
+  inject,
+  ref,
+  type InjectionKey,
+  type PropType,
+} from "vue";
+import {
+  resolveAction,
+  executeAction,
+  type ActionBinding,
+  type ActionHandler,
+  type ActionConfirm,
+  type ResolvedAction,
+} from "@json-render/core";
+import { useStateStore } from "./state.js";
+import { useOptionalValidation } from "./validation.js";
+
+function generateUniqueId(): string {
+  if (
+    typeof crypto !== "undefined" &&
+    typeof crypto.randomUUID === "function"
+  ) {
+    return crypto.randomUUID();
+  }
+  return `${Date.now()}-${Math.random().toString(36).slice(2, 9)}`;
+}
+
+const MAX_RESOLVE_DEPTH = 20;
+
+function deepResolveValue(
+  value: unknown,
+  get: (path: string) => unknown,
+  depth: number = 0,
+): unknown {
+  if (depth > MAX_RESOLVE_DEPTH) return value;
+  if (value === null || value === undefined) return value;
+
+  if (value === "$id") {
+    return generateUniqueId();
+  }
+
+  if (typeof value === "object" && !Array.isArray(value)) {
+    const obj = value as Record<string, unknown>;
+    const keys = Object.keys(obj);
+
+    if (keys.length === 1 && typeof obj.$state === "string") {
+      return get(obj.$state as string);
+    }
+
+    if (keys.length === 1 && "$id" in obj) {
+      return generateUniqueId();
+    }
+  }
+
+  if (Array.isArray(value)) {
+    return value.map((item) => deepResolveValue(item, get, depth + 1));
+  }
+
+  if (typeof value === "object") {
+    const resolved: Record<string, unknown> = {};
+    for (const [key, val] of Object.entries(value as Record<string, unknown>)) {
+      resolved[key] = deepResolveValue(val, get, depth + 1);
+    }
+    return resolved;
+  }
+
+  return value;
+}
+
+export interface PendingConfirmation {
+  action: ResolvedAction;
+  handler: ActionHandler;
+  resolve: () => void;
+  reject: () => void;
+}
+
+export interface ActionContextValue {
+  handlers: Record<string, ActionHandler>;
+  loadingActions: Set<string>;
+  pendingConfirmation: PendingConfirmation | null;
+  execute: (binding: ActionBinding) => Promise<void>;
+  confirm: () => void;
+  cancel: () => void;
+  registerHandler: (name: string, handler: ActionHandler) => void;
+}
+
+export const ActionKey: InjectionKey<ActionContextValue> = Symbol(
+  "json-render-actions",
+);
+
+export interface ActionProviderProps {
+  handlers?: Record<string, ActionHandler>;
+  navigate?: (path: string) => void;
+}
+
+export const ActionProvider = defineComponent({
+  name: "ActionProvider",
+  props: {
+    handlers: {
+      type: Object as PropType<Record<string, ActionHandler>>,
+      default: () => ({}),
+    },
+    navigate: {
+      type: Function as PropType<(path: string) => void>,
+      default: undefined,
+    },
+  },
+  setup(props, { slots }) {
+    const storeCtx = useStateStore();
+    const validation = useOptionalValidation();
+
+    const handlersRef = ref<Record<string, ActionHandler>>({
+      ...props.handlers,
+    });
+    const loadingActionsRef = ref<Set<string>>(new Set());
+    const pendingConfirmationRef = ref<PendingConfirmation | null>(null);
+
+    const registerHandler = (name: string, handler: ActionHandler) => {
+      handlersRef.value = { ...handlersRef.value, [name]: handler };
+    };
+
+    const execute = async (binding: ActionBinding) => {
+      const resolved = resolveAction(binding, storeCtx.getSnapshot());
+
+      if (resolved.action === "setState" && resolved.params) {
+        const statePath = resolved.params.statePath as string;
+        const value = resolved.params.value;
+        if (statePath) {
+          storeCtx.set(statePath, value);
+        }
+        return;
+      }
+
+      if (resolved.action === "pushState" && resolved.params) {
+        const statePath = resolved.params.statePath as string;
+        const rawValue = resolved.params.value;
+        if (statePath) {
+          const resolvedValue = deepResolveValue(rawValue, storeCtx.get);
+          const arr = (storeCtx.get(statePath) as unknown[] | undefined) ?? [];
+          storeCtx.set(statePath, [...arr, resolvedValue]);
+          const clearStatePath = resolved.params.clearStatePath as
+            | string
+            | undefined;
+          if (clearStatePath) {
+            storeCtx.set(clearStatePath, "");
+          }
+        }
+        return;
+      }
+
+      if (resolved.action === "removeState" && resolved.params) {
+        const statePath = resolved.params.statePath as string;
+        const index = resolved.params.index as number;
+        if (statePath !== undefined && index !== undefined) {
+          const arr = (storeCtx.get(statePath) as unknown[] | undefined) ?? [];
+          storeCtx.set(
+            statePath,
+            arr.filter((_, i) => i !== index),
+          );
+        }
+        return;
+      }
+
+      if (resolved.action === "push" && resolved.params) {
+        const screen = resolved.params.screen as string;
+        if (screen) {
+          const currentScreen = storeCtx.get("/currentScreen") as
+            | string
+            | undefined;
+          const navStack =
+            (storeCtx.get("/navStack") as string[] | undefined) ?? [];
+          if (currentScreen) {
+            storeCtx.set("/navStack", [...navStack, currentScreen]);
+          } else {
+            storeCtx.set("/navStack", [...navStack, ""]);
+          }
+          storeCtx.set("/currentScreen", screen);
+        }
+        return;
+      }
+
+      if (resolved.action === "pop") {
+        const navStack =
+          (storeCtx.get("/navStack") as string[] | undefined) ?? [];
+        if (navStack.length > 0) {
+          const previousScreen = navStack[navStack.length - 1];
+          storeCtx.set("/navStack", navStack.slice(0, -1));
+          if (previousScreen) {
+            storeCtx.set("/currentScreen", previousScreen);
+          } else {
+            storeCtx.set("/currentScreen", undefined);
+          }
+        }
+        return;
+      }
+
+      if (resolved.action === "validateForm") {
+        const validateAll = validation?.validateAll;
+        if (!validateAll) {
+          console.warn(
+            "validateForm action was dispatched but no ValidationProvider is connected.",
+          );
+          return;
+        }
+        const valid = validateAll();
+        const statePath =
+          (resolved.params?.statePath as string) || "/formValidation";
+        storeCtx.set(statePath, { valid });
+        return;
+      }
+
+      const handler = handlersRef.value[resolved.action];
+
+      if (!handler) {
+        console.warn(`No handler registered for action: ${resolved.action}`);
+        return;
+      }
+
+      if (resolved.confirm) {
+        return new Promise<void>((resolve, reject) => {
+          pendingConfirmationRef.value = {
+            action: resolved,
+            handler,
+            resolve: () => {
+              pendingConfirmationRef.value = null;
+              resolve();
+            },
+            reject: () => {
+              pendingConfirmationRef.value = null;
+              reject(new Error("Action cancelled"));
+            },
+          };
+        }).then(async () => {
+          const next = new Set(loadingActionsRef.value);
+          next.add(resolved.action);
+          loadingActionsRef.value = next;
+          try {
+            await executeAction({
+              action: resolved,
+              handler,
+              setState: storeCtx.set,
+              navigate: props.navigate,
+              executeAction: async (name) => {
+                const subBinding: ActionBinding = { action: name };
+                await execute(subBinding);
+              },
+            });
+          } finally {
+            const fin = new Set(loadingActionsRef.value);
+            fin.delete(resolved.action);
+            loadingActionsRef.value = fin;
+          }
+        });
+      } else {
+        const next = new Set(loadingActionsRef.value);
+        next.add(resolved.action);
+        loadingActionsRef.value = next;
+        try {
+          await executeAction({
+            action: resolved,
+            handler,
+            setState: storeCtx.set,
+            navigate: props.navigate,
+            executeAction: async (name) => {
+              const subBinding: ActionBinding = { action: name };
+              await execute(subBinding);
+            },
+          });
+        } finally {
+          const fin = new Set(loadingActionsRef.value);
+          fin.delete(resolved.action);
+          loadingActionsRef.value = fin;
+        }
+      }
+    };
+
+    const confirm = () => {
+      pendingConfirmationRef.value?.resolve();
+    };
+
+    const cancel = () => {
+      pendingConfirmationRef.value?.reject();
+    };
+
+    const ctx: ActionContextValue = {
+      get handlers() {
+        return handlersRef.value;
+      },
+      get loadingActions() {
+        return loadingActionsRef.value;
+      },
+      get pendingConfirmation() {
+        return pendingConfirmationRef.value;
+      },
+      execute,
+      confirm,
+      cancel,
+      registerHandler,
+    };
+
+    provide(ActionKey, ctx);
+
+    return () => slots.default?.();
+  },
+});
+
+export function useActions(): ActionContextValue {
+  const ctx = inject(ActionKey);
+  if (!ctx) {
+    throw new Error("useActions must be used within an ActionProvider");
+  }
+  return ctx;
+}
+
+export function useAction(binding: ActionBinding): {
+  execute: () => Promise<void>;
+  isLoading: boolean;
+} {
+  const { execute, loadingActions } = useActions();
+
+  return {
+    execute: () => execute(binding),
+    get isLoading() {
+      return loadingActions.has(binding.action);
+    },
+  };
+}
+
+// ---------------------------------------------------------------------------
+// ConfirmDialog
+// ---------------------------------------------------------------------------
+
+export interface ConfirmDialogProps {
+  confirm: {
+    title: string;
+    message: string;
+    confirmLabel?: string;
+    cancelLabel?: string;
+    variant?: string;
+  };
+  onConfirm: () => void;
+  onCancel: () => void;
+}
+
+export const ConfirmDialog = defineComponent({
+  name: "ConfirmDialog",
+  props: {
+    confirm: {
+      type: Object as PropType<ConfirmDialogProps["confirm"]>,
+      required: true,
+    },
+    onConfirm: { type: Function as PropType<() => void>, required: true },
+    onCancel: { type: Function as PropType<() => void>, required: true },
+  },
+  setup(props) {
+    return () => {
+      const isDanger = props.confirm.variant === "danger";
+
+      return h(
+        "div",
+        {
+          style: {
+            position: "fixed",
+            inset: "0",
+            backgroundColor: "rgba(0, 0, 0, 0.5)",
+            display: "flex",
+            alignItems: "center",
+            justifyContent: "center",
+            zIndex: 50,
+          },
+          onClick: props.onCancel,
+        },
+        [
+          h(
+            "div",
+            {
+              style: {
+                backgroundColor: "white",
+                borderRadius: "8px",
+                padding: "24px",
+                maxWidth: "400px",
+                width: "100%",
+                boxShadow: "0 20px 25px -5px rgba(0, 0, 0, 0.1)",
+              },
+              onClick: (e: Event) => e.stopPropagation(),
+            },
+            [
+              h(
+                "h3",
+                {
+                  style: {
+                    margin: "0 0 8px 0",
+                    fontSize: "18px",
+                    fontWeight: "600",
+                  },
+                },
+                props.confirm.title,
+              ),
+              h(
+                "p",
+                {
+                  style: { margin: "0 0 24px 0", color: "#6b7280" },
+                },
+                props.confirm.message,
+              ),
+              h(
+                "div",
+                {
+                  style: {
+                    display: "flex",
+                    gap: "12px",
+                    justifyContent: "flex-end",
+                  },
+                },
+                [
+                  h(
+                    "button",
+                    {
+                      onClick: props.onCancel,
+                      style: {
+                        padding: "8px 16px",
+                        borderRadius: "6px",
+                        border: "1px solid #d1d5db",
+                        backgroundColor: "white",
+                        cursor: "pointer",
+                      },
+                    },
+                    props.confirm.cancelLabel ?? "Cancel",
+                  ),
+                  h(
+                    "button",
+                    {
+                      onClick: props.onConfirm,
+                      style: {
+                        padding: "8px 16px",
+                        borderRadius: "6px",
+                        border: "none",
+                        backgroundColor: isDanger ? "#dc2626" : "#3b82f6",
+                        color: "white",
+                        cursor: "pointer",
+                      },
+                    },
+                    props.confirm.confirmLabel ?? "Confirm",
+                  ),
+                ],
+              ),
+            ],
+          ),
+        ],
+      );
+    };
+  },
+});

packages/vue/src/composables/repeat-scope.ts

@@ -0,0 +1,56 @@
+import {
+  defineComponent,
+  provide,
+  inject,
+  type InjectionKey,
+  type PropType,
+} from "vue";
+
+export interface RepeatScopeValue {
+  item: unknown;
+  index: number;
+  basePath: string;
+}
+
+export const RepeatScopeKey: InjectionKey<RepeatScopeValue | null> = Symbol(
+  "json-render-repeat-scope",
+);
+
+export const RepeatScopeProvider = defineComponent({
+  name: "RepeatScopeProvider",
+  props: {
+    item: {
+      type: null as unknown as PropType<unknown>,
+      required: true,
+    },
+    index: {
+      type: Number,
+      required: true,
+    },
+    basePath: {
+      type: String,
+      required: true,
+    },
+  },
+  setup(props, { slots }) {
+    const value: RepeatScopeValue = {
+      get item() {
+        return props.item;
+      },
+      get index() {
+        return props.index;
+      },
+      get basePath() {
+        return props.basePath;
+      },
+    };
+
+    provide(RepeatScopeKey, value);
+
+    return () => slots.default?.();
+  },
+});
+
+export function useRepeatScope(): RepeatScopeValue | null {
+  return inject(RepeatScopeKey, null);
+}

packages/vue/src/composables/state.test.ts

@@ -0,0 +1,99 @@
+import { describe, it, expect } from "vitest";
+import { defineComponent, h, createApp, nextTick } from "vue";
+import {
+  StateProvider,
+  useStateStore,
+  useStateValue,
+  useStateBinding,
+} from "./state.js";
+
+function runInStateProvider<T>(
+  initialState: Record<string, unknown>,
+  fn: () => T,
+): T {
+  let result: T | undefined;
+
+  const Inner = defineComponent({
+    setup() {
+      result = fn();
+      return () => null;
+    },
+  });
+
+  const App = defineComponent({
+    setup() {
+      return () => h(StateProvider, { initialState }, () => h(Inner));
+    },
+  });
+
+  const container = document.createElement("div");
+  const app = createApp(App);
+  app.mount(container);
+  app.unmount();
+
+  return result!;
+}
+
+describe("StateProvider + useStateStore", () => {
+  it("provides initial state and get/set round-trip", () => {
+    const ctx = runInStateProvider({ count: 0 }, () => useStateStore());
+
+    expect(ctx.get("/count")).toBe(0);
+    ctx.set("/count", 42);
+    expect(ctx.get("/count")).toBe(42);
+  });
+
+  it("state reflects initial values", () => {
+    const ctx = runInStateProvider({ name: "Alice" }, () => useStateStore());
+    expect(ctx.state.name).toBe("Alice");
+  });
+
+  it("getSnapshot returns current state", () => {
+    const ctx = runInStateProvider({ x: 1 }, () => useStateStore());
+    expect(ctx.getSnapshot().x).toBe(1);
+
+    ctx.set("/x", 99);
+    expect(ctx.getSnapshot().x).toBe(99);
+  });
+
+  it("update applies multiple changes", () => {
+    const ctx = runInStateProvider({ a: 1, b: 2 }, () => useStateStore());
+
+    ctx.update({ "/a": 10, "/b": 20 });
+    expect(ctx.get("/a")).toBe(10);
+    expect(ctx.get("/b")).toBe(20);
+  });
+});
+
+describe("useStateValue", () => {
+  it("reads a value from state", () => {
+    const value = runInStateProvider({ name: "Alice" }, () =>
+      useStateValue<string>("/name"),
+    );
+    expect(value).toBe("Alice");
+  });
+
+  it("returns undefined for missing path", () => {
+    const value = runInStateProvider({}, () =>
+      useStateValue<string>("/missing"),
+    );
+    expect(value).toBeUndefined();
+  });
+});
+
+describe("useStateBinding", () => {
+  it("returns value from state and a setter", () => {
+    const [value, setValue] = runInStateProvider({ x: 42 }, () =>
+      useStateBinding<number>("/x"),
+    );
+    expect(value).toBe(42);
+    expect(typeof setValue).toBe("function");
+  });
+
+  it("returns undefined for missing path", () => {
+    const [value] = runInStateProvider({}, () =>
+      useStateBinding<string>("/missing"),
+    );
+    expect(value).toBeUndefined();
+  });
+});

packages/vue/src/composables/state.ts

@@ -0,0 +1,166 @@
+import {
+  defineComponent,
+  provide,
+  inject,
+  shallowRef,
+  onBeforeUnmount,
+  watch,
+  type InjectionKey,
+  type PropType,
+} from "vue";
+import {
+  getByPath,
+  createStateStore,
+  type StateModel,
+  type StateStore,
+} from "@json-render/core";
+import { flattenToPointers } from "@json-render/core/store-utils";
+
+export interface StateContextValue {
+  state: StateModel;
+  get: (path: string) => unknown;
+  set: (path: string, value: unknown) => void;
+  update: (updates: Record<string, unknown>) => void;
+  getSnapshot: () => StateModel;
+}
+
+export const StateKey: InjectionKey<StateContextValue> =
+  Symbol("json-render-state");
+
+export interface StateProviderProps {
+  store?: StateStore;
+  initialState?: StateModel;
+  onStateChange?: (changes: Array<{ path: string; value: unknown }>) => void;
+}
+
+export const StateProvider = defineComponent({
+  name: "StateProvider",
+  props: {
+    store: {
+      type: Object as PropType<StateStore>,
+      default: undefined,
+    },
+    initialState: {
+      type: Object as PropType<StateModel>,
+      default: () => ({}),
+    },
+    onStateChange: {
+      type: Function as PropType<
+        (changes: Array<{ path: string; value: unknown }>) => void
+      >,
+      default: undefined,
+    },
+  },
+  setup(props, { slots }) {
+    const isControlled = !!props.store;
+    let internalStore: StateStore | undefined;
+    if (!isControlled) {
+      internalStore = createStateStore(props.initialState);
+    }
+
+    const activeStore = props.store ?? internalStore!;
+
+    const stateRef = shallowRef<StateModel>(activeStore.getSnapshot());
+
+    const unsub = activeStore.subscribe(() => {
+      stateRef.value = activeStore.getSnapshot();
+    });
+    onBeforeUnmount(unsub);
+
+    // Sync initialState changes for uncontrolled mode
+    if (!isControlled) {
+      let prevFlat: Record<string, unknown> =
+        props.initialState && Object.keys(props.initialState).length > 0
+          ? flattenToPointers(props.initialState)
+          : {};
+
+      watch(
+        () => props.initialState,
+        (newState) => {
+          if (isControlled || !newState) return;
+          const nextFlat =
+            Object.keys(newState).length > 0 ? flattenToPointers(newState) : {};
+          const allKeys = new Set([
+            ...Object.keys(prevFlat),
+            ...Object.keys(nextFlat),
+          ]);
+          const updates: Record<string, unknown> = {};
+          for (const key of allKeys) {
+            if (prevFlat[key] !== nextFlat[key]) {
+              updates[key] = key in nextFlat ? nextFlat[key] : undefined;
+            }
+          }
+          prevFlat = nextFlat;
+          if (Object.keys(updates).length > 0) {
+            activeStore.update(updates);
+          }
+        },
+        { deep: true },
+      );
+    }
+
+    const get = (path: string) => activeStore.get(path);
+
+    const set = (path: string, value: unknown) => {
+      const prev = activeStore.getSnapshot();
+      activeStore.set(path, value);
+      if (!isControlled && activeStore.getSnapshot() !== prev) {
+        props.onStateChange?.([{ path, value }]);
+      }
+    };
+
+    const update = (updates: Record<string, unknown>) => {
+      const prev = activeStore.getSnapshot();
+      activeStore.update(updates);
+      if (!isControlled && activeStore.getSnapshot() !== prev) {
+        const changes: Array<{ path: string; value: unknown }> = [];
+        for (const [path, value] of Object.entries(updates)) {
+          if (getByPath(prev, path) !== value) {
+            changes.push({ path, value });
+          }
+        }
+        if (changes.length > 0) {
+          props.onStateChange?.(changes);
+        }
+      }
+    };
+
+    const getSnapshot = () => activeStore.getSnapshot();
+
+    const ctx: StateContextValue = {
+      get state() {
+        return stateRef.value;
+      },
+      get,
+      set,
+      update,
+      getSnapshot,
+    };
+
+    provide(StateKey, ctx);
+
+    return () => slots.default?.();
+  },
+});
+
+export function useStateStore(): StateContextValue {
+  const ctx = inject(StateKey);
+  if (!ctx) {
+    throw new Error("useStateStore must be used within a StateProvider");
+  }
+  return ctx;
+}
+
+export function useStateValue<T>(path: string): T | undefined {
+  const { state } = useStateStore();
+  return getByPath(state, path) as T | undefined;
+}
+
+export function useStateBinding<T>(
+  path: string,
+): [T | undefined, (value: T) => void] {
+  const { state, set } = useStateStore();
+  const value = getByPath(state, path) as T | undefined;
+  const setValue = (newValue: T) => set(path, newValue);
+  return [value, setValue];
+}

packages/vue/src/composables/validation.ts

@@ -0,0 +1,191 @@
+import {
+  defineComponent,
+  provide,
+  inject,
+  ref,
+  computed,
+  watchEffect,
+  type InjectionKey,
+  type PropType,
+  type ComputedRef,
+} from "vue";
+import {
+  runValidation,
+  type ValidationConfig,
+  type ValidationFunction,
+  type ValidationResult,
+} from "@json-render/core";
+import { useStateStore } from "./state.js";
+
+export interface FieldValidationState {
+  touched: boolean;
+  validated: boolean;
+  result: ValidationResult | null;
+}
+
+export interface ValidationContextValue {
+  customFunctions: Record<string, ValidationFunction>;
+  fieldStates: Record<string, FieldValidationState>;
+  validate: (path: string, config: ValidationConfig) => ValidationResult;
+  touch: (path: string) => void;
+  clear: (path: string) => void;
+  validateAll: () => boolean;
+  registerField: (path: string, config: ValidationConfig) => void;
+}
+
+export const ValidationKey: InjectionKey<ValidationContextValue> = Symbol(
+  "json-render-validation",
+);
+
+export interface ValidationProviderProps {
+  customFunctions?: Record<string, ValidationFunction>;
+}
+
+export const ValidationProvider = defineComponent({
+  name: "ValidationProvider",
+  props: {
+    customFunctions: {
+      type: Object as PropType<Record<string, ValidationFunction>>,
+      default: () => ({}),
+    },
+  },
+  setup(props, { slots }) {
+    const storeCtx = useStateStore();
+    const fieldStates = ref<Record<string, FieldValidationState>>({});
+    const fieldConfigs = ref<Record<string, ValidationConfig>>({});
+
+    const registerField = (path: string, config: ValidationConfig) => {
+      fieldConfigs.value = { ...fieldConfigs.value, [path]: config };
+    };
+
+    const validate = (
+      path: string,
+      config: ValidationConfig,
+    ): ValidationResult => {
+      const currentState = storeCtx.getSnapshot();
+      const segments = path.split("/").filter(Boolean);
+      let value: unknown = currentState;
+      for (const seg of segments) {
+        if (value != null && typeof value === "object") {
+          value = (value as Record<string, unknown>)[seg];
+        } else {
+          value = undefined;
+          break;
+        }
+      }
+      const result = runValidation(config, {
+        value,
+        stateModel: currentState,
+        customFunctions: props.customFunctions,
+      });
+
+      fieldStates.value = {
+        ...fieldStates.value,
+        [path]: {
+          touched: fieldStates.value[path]?.touched ?? true,
+          validated: true,
+          result,
+        },
+      };
+
+      return result;
+    };
+
+    const touch = (path: string) => {
+      const existing = fieldStates.value[path];
+      fieldStates.value = {
+        ...fieldStates.value,
+        [path]: {
+          touched: true,
+          validated: existing?.validated ?? false,
+          result: existing?.result ?? null,
+        },
+      };
+    };
+
+    const clear = (path: string) => {
+      const { [path]: _, ...rest } = fieldStates.value;
+      fieldStates.value = rest;
+    };
+
+    const validateAll = (): boolean => {
+      let allValid = true;
+      for (const [path, config] of Object.entries(fieldConfigs.value)) {
+        const result = validate(path, config);
+        if (!result.valid) {
+          allValid = false;
+        }
+      }
+      return allValid;
+    };
+
+    const ctx: ValidationContextValue = {
+      get customFunctions() {
+        return props.customFunctions;
+      },
+      get fieldStates() {
+        return fieldStates.value;
+      },
+      validate,
+      touch,
+      clear,
+      validateAll,
+      registerField,
+    };
+
+    provide(ValidationKey, ctx);
+
+    return () => slots.default?.();
+  },
+});
+
+export function useValidation(): ValidationContextValue {
+  const ctx = inject(ValidationKey);
+  if (!ctx) {
+    throw new Error("useValidation must be used within a ValidationProvider");
+  }
+  return ctx;
+}
+
+export function useOptionalValidation(): ValidationContextValue | null {
+  return inject(ValidationKey, null);
+}
+
+export function useFieldValidation(
+  path: string,
+  config?: ValidationConfig,
+): {
+  state: ComputedRef<FieldValidationState>;
+  validate: () => ValidationResult;
+  touch: () => void;
+  clear: () => void;
+  errors: ComputedRef<string[]>;
+  isValid: ComputedRef<boolean>;
+} {
+  const ctx = useValidation();
+
+  if (path && config) {
+    watchEffect(() => {
+      ctx.registerField(path, config);
+    });
+  }
+
+  const defaultState: FieldValidationState = {
+    touched: false,
+    validated: false,
+    result: null,
+  };
+
+  const state = computed(() => ctx.fieldStates[path] ?? defaultState);
+  const errors = computed(() => state.value.result?.errors ?? []);
+  const isValid = computed(() => state.value.result?.valid ?? true);
+
+  return {
+    state,
+    validate: () => ctx.validate(path, config ?? { checks: [] }),
+    touch: () => ctx.touch(path),
+    clear: () => ctx.clear(path),
+    errors,
+    isValid,
+  };
+}

packages/vue/src/composables/visibility.test.ts

@@ -0,0 +1,93 @@
+import { describe, it, expect } from "vitest";
+import { defineComponent, h, createApp } from "vue";
+import {
+  VisibilityProvider,
+  useVisibility,
+  useIsVisible,
+} from "./visibility.js";
+import { StateProvider } from "./state.js";
+
+function runInProviders<T>(
+  initialState: Record<string, unknown>,
+  fn: () => T,
+): T {
+  let result: T | undefined;
+
+  const Inner = defineComponent({
+    setup() {
+      result = fn();
+      return () => null;
+    },
+  });
+
+  const App = defineComponent({
+    setup() {
+      return () =>
+        h(StateProvider, { initialState }, () =>
+          h(VisibilityProvider, null, () => h(Inner)),
+        );
+    },
+  });
+
+  const container = document.createElement("div");
+  const app = createApp(App);
+  app.mount(container);
+  app.unmount();
+
+  return result!;
+}
+
+describe("useVisibility", () => {
+  it("provides isVisible function", () => {
+    const ctx = runInProviders({}, () => useVisibility());
+    expect(typeof ctx.isVisible).toBe("function");
+  });
+
+  it("provides visibility context with stateModel", () => {
+    const ctx = runInProviders({ test: true }, () => useVisibility());
+    expect(ctx.ctx.stateModel).toEqual({ test: true });
+  });
+});
+
+describe("useIsVisible", () => {
+  it("returns true for undefined condition", () => {
+    const result = runInProviders({}, () => useIsVisible(undefined));
+    expect(result).toBe(true);
+  });
+
+  it("returns true for true condition", () => {
+    const result = runInProviders({}, () => useIsVisible(true));
+    expect(result).toBe(true);
+  });
+
+  it("returns false for false condition", () => {
+    const result = runInProviders({}, () => useIsVisible(false));
+    expect(result).toBe(false);
+  });
+
+  it("evaluates $state conditions against state", () => {
+    const trueResult = runInProviders({ isVisible: true }, () =>
+      useIsVisible({ $state: "/isVisible" }),
+    );
+    expect(trueResult).toBe(true);
+
+    const falseResult = runInProviders({ isVisible: false }, () =>
+      useIsVisible({ $state: "/isVisible" }),
+    );
+    expect(falseResult).toBe(false);
+  });
+
+  it("evaluates equality conditions", () => {
+    const result = runInProviders({ count: 1 }, () =>
+      useIsVisible({ $state: "/count", eq: 1 }),
+    );
+    expect(result).toBe(true);
+  });
+
+  it("evaluates array conditions (implicit AND)", () => {
+    const result = runInProviders({ user: { isAdmin: true }, count: 5 }, () =>
+      useIsVisible([{ $state: "/user/isAdmin" }, { $state: "/count", eq: 5 }]),
+    );
+    expect(result).toBe(true);
+  });
+});

packages/vue/src/composables/visibility.ts

@@ -0,0 +1,60 @@
+import {
+  defineComponent,
+  provide,
+  inject,
+  computed,
+  type InjectionKey,
+} from "vue";
+import {
+  evaluateVisibility,
+  type VisibilityCondition,
+  type VisibilityContext as CoreVisibilityContext,
+} from "@json-render/core";
+import { useStateStore } from "./state.js";
+
+export interface VisibilityContextValue {
+  isVisible: (condition: VisibilityCondition | undefined) => boolean;
+  ctx: CoreVisibilityContext;
+}
+
+export const VisibilityKey: InjectionKey<VisibilityContextValue> = Symbol(
+  "json-render-visibility",
+);
+
+export const VisibilityProvider = defineComponent({
+  name: "VisibilityProvider",
+  setup(_, { slots }) {
+    const storeCtx = useStateStore();
+
+    const ctxRef = computed<CoreVisibilityContext>(() => ({
+      stateModel: storeCtx.state,
+    }));
+
+    const value: VisibilityContextValue = {
+      isVisible: (condition: VisibilityCondition | undefined) =>
+        evaluateVisibility(condition, ctxRef.value),
+      get ctx() {
+        return ctxRef.value;
+      },
+    };
+
+    provide(VisibilityKey, value);
+
+    return () => slots.default?.();
+  },
+});
+
+export function useVisibility(): VisibilityContextValue {
+  const ctx = inject(VisibilityKey);
+  if (!ctx) {
+    throw new Error("useVisibility must be used within a VisibilityProvider");
+  }
+  return ctx;
+}
+
+export function useIsVisible(
+  condition: VisibilityCondition | undefined,
+): boolean {
+  const { isVisible } = useVisibility();
+  return isVisible(condition);
+}

packages/vue/src/hooks.test.ts

@@ -0,0 +1,394 @@
+import { describe, it, expect } from "vitest";
+import { defineComponent, h, createApp } from "vue";
+import {
+  flatToTree,
+  buildSpecFromParts,
+  getTextFromParts,
+  useBoundProp,
+} from "./hooks.js";
+import { StateProvider, useStateBinding } from "./composables/state.js";
+
+describe("flatToTree", () => {
+  it("converts array of elements to tree structure", () => {
+    const elements = [
+      { key: "container", type: "stack", props: {}, parentKey: null },
+      {
+        key: "text1",
+        type: "text",
+        props: { content: "Hello" },
+        parentKey: "container",
+      },
+      {
+        key: "text2",
+        type: "text",
+        props: { content: "World" },
+        parentKey: "container",
+      },
+    ];
+
+    const tree = flatToTree(elements);
+
+    expect(tree.root).toBe("container");
+    expect(Object.keys(tree.elements)).toHaveLength(3);
+    expect(tree.elements["container"]).toBeDefined();
+    expect(tree.elements["text1"]).toBeDefined();
+    expect(tree.elements["text2"]).toBeDefined();
+  });
+
+  it("builds parent-child relationships", () => {
+    const elements = [
+      { key: "root", type: "stack", props: {}, parentKey: null },
+      { key: "child1", type: "text", props: {}, parentKey: "root" },
+      { key: "child2", type: "text", props: {}, parentKey: "root" },
+    ];
+
+    const tree = flatToTree(elements);
+
+    expect(tree.elements["root"]!.children).toHaveLength(2);
+    expect(tree.elements["root"]!.children).toContain("child1");
+    expect(tree.elements["root"]!.children).toContain("child2");
+  });
+
+  it("handles single root element", () => {
+    const elements = [
+      {
+        key: "only",
+        type: "text",
+        props: { content: "Single" },
+        parentKey: null,
+      },
+    ];
+
+    const tree = flatToTree(elements);
+
+    expect(tree.root).toBe("only");
+    expect(Object.keys(tree.elements)).toHaveLength(1);
+  });
+
+  it("handles deeply nested elements", () => {
+    const elements = [
+      { key: "level0", type: "stack", props: {}, parentKey: null },
+      { key: "level1", type: "stack", props: {}, parentKey: "level0" },
+      { key: "level2", type: "stack", props: {}, parentKey: "level1" },
+      { key: "level3", type: "text", props: {}, parentKey: "level2" },
+    ];
+
+    const tree = flatToTree(elements);
+
+    expect(tree.root).toBe("level0");
+    expect(tree.elements["level0"]!.children).toContain("level1");
+    expect(tree.elements["level1"]!.children).toContain("level2");
+    expect(tree.elements["level2"]!.children).toContain("level3");
+  });
+
+  it("preserves element props", () => {
+    const elements = [
+      {
+        key: "btn",
+        type: "button",
+        props: { label: "Click me", variant: "primary" },
+        parentKey: null,
+      },
+    ];
+
+    const tree = flatToTree(elements);
+
+    expect(tree.elements["btn"]!.props).toEqual({
+      label: "Click me",
+      variant: "primary",
+    });
+  });
+
+  it("preserves visibility conditions", () => {
+    const elements = [
+      {
+        key: "conditional",
+        type: "text",
+        props: {},
+        parentKey: null,
+        visible: { $state: "/isVisible" },
+      },
+    ];
+
+    const tree = flatToTree(elements);
+
+    expect(tree.elements["conditional"]!.visible).toEqual({
+      $state: "/isVisible",
+    });
+  });
+
+  it("handles empty elements array", () => {
+    const tree = flatToTree([]);
+
+    expect(tree.root).toBe("");
+    expect(Object.keys(tree.elements)).toHaveLength(0);
+  });
+
+  it("handles multiple children correctly", () => {
+    const elements = [
+      { key: "parent", type: "grid", props: {}, parentKey: null },
+      { key: "a", type: "card", props: {}, parentKey: "parent" },
+      { key: "b", type: "card", props: {}, parentKey: "parent" },
+      { key: "c", type: "card", props: {}, parentKey: "parent" },
+      { key: "d", type: "card", props: {}, parentKey: "parent" },
+    ];
+
+    const tree = flatToTree(elements);
+
+    expect(tree.elements["parent"]!.children).toHaveLength(4);
+    expect(tree.elements["parent"]!.children).toEqual(["a", "b", "c", "d"]);
+  });
+});
+
+describe("buildSpecFromParts", () => {
+  it("returns null when no data-spec parts are present", () => {
+    const parts = [
+      { type: "text", text: "Hello there" },
+      { type: "text", text: "How can I help?" },
+    ];
+    expect(buildSpecFromParts(parts)).toBeNull();
+  });
+
+  it("builds a spec from patch parts", () => {
+    const parts = [
+      {
+        type: "data-spec",
+        data: {
+          type: "patch",
+          patch: { op: "add", path: "/root", value: "main" },
+        },
+      },
+      {
+        type: "data-spec",
+        data: {
+          type: "patch",
+          patch: {
+            op: "add",
+            path: "/elements/main",
+            value: { type: "Card", props: { title: "Hello" }, children: [] },
+          },
+        },
+      },
+    ];
+
+    const spec = buildSpecFromParts(parts);
+    expect(spec).not.toBeNull();
+    expect(spec!.root).toBe("main");
+    expect(spec!.elements["main"]).toEqual({
+      type: "Card",
+      props: { title: "Hello" },
+      children: [],
+    });
+  });
+
+  it("handles flat spec parts", () => {
+    const parts = [
+      {
+        type: "data-spec",
+        data: {
+          type: "flat",
+          spec: {
+            root: "card-1",
+            elements: {
+              "card-1": { type: "Card", props: {}, children: [] },
+            },
+          },
+        },
+      },
+    ];
+
+    const spec = buildSpecFromParts(parts);
+    expect(spec).not.toBeNull();
+    expect(spec!.root).toBe("card-1");
+    expect(spec!.elements["card-1"]).toBeDefined();
+  });
+
+  it("ignores non-spec parts", () => {
+    const parts = [
+      { type: "text", text: "Some text" },
+      {
+        type: "data-spec",
+        data: {
+          type: "patch",
+          patch: { op: "add", path: "/root", value: "main" },
+        },
+      },
+      { type: "tool-invocation", data: { toolName: "search" } },
+    ];
+
+    const spec = buildSpecFromParts(parts);
+    expect(spec).not.toBeNull();
+    expect(spec!.root).toBe("main");
+  });
+
+  it("applies patches incrementally", () => {
+    const parts = [
+      {
+        type: "data-spec",
+        data: {
+          type: "patch",
+          patch: { op: "add", path: "/root", value: "main" },
+        },
+      },
+      {
+        type: "data-spec",
+        data: {
+          type: "patch",
+          patch: {
+            op: "add",
+            path: "/elements/main",
+            value: { type: "Stack", props: {}, children: ["child"] },
+          },
+        },
+      },
+      {
+        type: "data-spec",
+        data: {
+          type: "patch",
+          patch: {
+            op: "add",
+            path: "/elements/child",
+            value: { type: "Text", props: { content: "Hi" }, children: [] },
+          },
+        },
+      },
+    ];
+
+    const spec = buildSpecFromParts(parts);
+    expect(spec).not.toBeNull();
+    expect(Object.keys(spec!.elements)).toHaveLength(2);
+    expect(spec!.elements["child"]!.props.content).toBe("Hi");
+  });
+
+  it("returns null from empty parts list", () => {
+    const spec = buildSpecFromParts([]);
+    expect(spec).toBeNull();
+  });
+});
+
+describe("getTextFromParts", () => {
+  it("extracts text from text parts", () => {
+    const parts = [
+      { type: "text", text: "Hello" },
+      { type: "text", text: "World" },
+    ];
+    expect(getTextFromParts(parts)).toBe("Hello\n\nWorld");
+  });
+
+  it("returns empty string when no text parts", () => {
+    const parts = [
+      {
+        type: "data-spec",
+        data: {
+          type: "patch",
+          patch: { op: "add", path: "/root", value: "x" },
+        },
+      },
+    ];
+    expect(getTextFromParts(parts)).toBe("");
+  });
+
+  it("ignores non-text parts", () => {
+    const parts = [
+      { type: "text", text: "Before" },
+      { type: "data-spec", data: {} },
+      { type: "tool-invocation", data: {} },
+      { type: "text", text: "After" },
+    ];
+    expect(getTextFromParts(parts)).toBe("Before\n\nAfter");
+  });
+
+  it("trims whitespace from text parts", () => {
+    const parts = [
+      { type: "text", text: "  Hello  " },
+      { type: "text", text: "  World  " },
+    ];
+    expect(getTextFromParts(parts)).toBe("Hello\n\nWorld");
+  });
+
+  it("skips empty text parts", () => {
+    const parts = [
+      { type: "text", text: "Hello" },
+      { type: "text", text: "   " },
+      { type: "text", text: "World" },
+    ];
+    expect(getTextFromParts(parts)).toBe("Hello\n\nWorld");
+  });
+
+  it("ignores text parts with non-string text field", () => {
+    const parts = [
+      { type: "text", text: "Valid" },
+      { type: "text", text: undefined as unknown as string },
+      { type: "text", text: 42 as unknown as string },
+      { type: "text", text: "Also valid" },
+    ];
+    expect(getTextFromParts(parts)).toBe("Valid\n\nAlso valid");
+  });
+});
+
+function runInStateProvider<T>(
+  initialState: Record<string, unknown>,
+  fn: () => T,
+): T {
+  let result: T | undefined;
+
+  const Inner = defineComponent({
+    setup() {
+      result = fn();
+      return () => null;
+    },
+  });
+
+  const App = defineComponent({
+    setup() {
+      return () => h(StateProvider, { initialState }, () => h(Inner));
+    },
+  });
+
+  const container = document.createElement("div");
+  const app = createApp(App);
+  app.mount(container);
+  app.unmount();
+
+  return result!;
+}
+
+describe("useBoundProp", () => {
+  it("returns the prop value as-is", () => {
+    const [value] = runInStateProvider({ name: "test" }, () =>
+      useBoundProp<string>("hello", undefined),
+    );
+    expect(value).toBe("hello");
+  });
+
+  it("returns undefined when prop value is undefined", () => {
+    const [value] = runInStateProvider({}, () =>
+      useBoundProp<string>(undefined, undefined),
+    );
+    expect(value).toBeUndefined();
+  });
+
+  it("provides a setter function", () => {
+    const [, setValue] = runInStateProvider({ name: "test" }, () =>
+      useBoundProp<string>("hello", "/name"),
+    );
+    expect(typeof setValue).toBe("function");
+  });
+});
+
+describe("useStateBinding", () => {
+  it("returns value from state and a setter", () => {
+    const [value, setValue] = runInStateProvider({ x: 42 }, () =>
+      useStateBinding<number>("/x"),
+    );
+    expect(value).toBe(42);
+    expect(typeof setValue).toBe("function");
+  });
+
+  it("returns undefined for missing path", () => {
+    const [value] = runInStateProvider({}, () =>
+      useStateBinding<string>("/missing"),
+    );
+    expect(value).toBeUndefined();
+  });
+});

packages/vue/src/hooks.ts

@@ -0,0 +1,688 @@
+import {
+  ref,
+  computed,
+  watch,
+  onBeforeUnmount,
+  type ComputedRef,
+  type Ref,
+} from "vue";
+import type {
+  Spec,
+  UIElement,
+  FlatElement,
+  JsonPatch,
+  SpecDataPart,
+} from "@json-render/core";
+import {
+  setByPath,
+  getByPath,
+  addByPath,
+  removeByPath,
+  createMixedStreamParser,
+  applySpecPatch,
+  nestedToFlat,
+  SPEC_DATA_PART_TYPE,
+} from "@json-render/core";
+import { useStateStore } from "./composables/state.js";
+
+/**
+ * Token usage metadata from AI generation
+ */
+export interface TokenUsage {
+  promptTokens: number;
+  completionTokens: number;
+  totalTokens: number;
+}
+
+type ParsedLine =
+  | { type: "patch"; patch: JsonPatch }
+  | { type: "usage"; usage: TokenUsage }
+  | null;
+
+function parseLine(line: string): ParsedLine {
+  try {
+    const trimmed = line.trim();
+    if (!trimmed || trimmed.startsWith("//")) {
+      return null;
+    }
+    const parsed = JSON.parse(trimmed);
+
+    if (parsed.__meta === "usage") {
+      return {
+        type: "usage",
+        usage: {
+          promptTokens: parsed.promptTokens ?? 0,
+          completionTokens: parsed.completionTokens ?? 0,
+          totalTokens: parsed.totalTokens ?? 0,
+        },
+      };
+    }
+
+    return { type: "patch", patch: parsed as JsonPatch };
+  } catch {
+    return null;
+  }
+}
+
+function setSpecValue(newSpec: Spec, path: string, value: unknown): void {
+  if (path === "/root") {
+    newSpec.root = value as string;
+    return;
+  }
+
+  if (path === "/state") {
+    newSpec.state = value as Record<string, unknown>;
+    return;
+  }
+
+  if (path.startsWith("/state/")) {
+    if (!newSpec.state) newSpec.state = {};
+    const statePath = path.slice("/state".length);
+    setByPath(newSpec.state as Record<string, unknown>, statePath, value);
+    return;
+  }
+
+  if (path.startsWith("/elements/")) {
+    const pathParts = path.slice("/elements/".length).split("/");
+    const elementKey = pathParts[0];
+    if (!elementKey) return;
+
+    if (pathParts.length === 1) {
+      newSpec.elements[elementKey] = value as UIElement;
+    } else {
+      const element = newSpec.elements[elementKey];
+      if (element) {
+        const propPath = "/" + pathParts.slice(1).join("/");
+        const newElement = { ...element };
+        setByPath(
+          newElement as unknown as Record<string, unknown>,
+          propPath,
+          value,
+        );
+        newSpec.elements[elementKey] = newElement;
+      }
+    }
+  }
+}
+
+function removeSpecValue(newSpec: Spec, path: string): void {
+  if (path === "/state") {
+    delete newSpec.state;
+    return;
+  }
+
+  if (path.startsWith("/state/") && newSpec.state) {
+    const statePath = path.slice("/state".length);
+    removeByPath(newSpec.state as Record<string, unknown>, statePath);
+    return;
+  }
+
+  if (path.startsWith("/elements/")) {
+    const pathParts = path.slice("/elements/".length).split("/");
+    const elementKey = pathParts[0];
+    if (!elementKey) return;
+
+    if (pathParts.length === 1) {
+      const { [elementKey]: _, ...rest } = newSpec.elements;
+      newSpec.elements = rest;
+    } else {
+      const element = newSpec.elements[elementKey];
+      if (element) {
+        const propPath = "/" + pathParts.slice(1).join("/");
+        const newElement = { ...element };
+        removeByPath(
+          newElement as unknown as Record<string, unknown>,
+          propPath,
+        );
+        newSpec.elements[elementKey] = newElement;
+      }
+    }
+  }
+}
+
+function getSpecValue(spec: Spec, path: string): unknown {
+  if (path === "/root") return spec.root;
+  if (path === "/state") return spec.state;
+  if (path.startsWith("/state/") && spec.state) {
+    const statePath = path.slice("/state".length);
+    return getByPath(spec.state as Record<string, unknown>, statePath);
+  }
+  return getByPath(spec as unknown as Record<string, unknown>, path);
+}
+
+function applyPatch(spec: Spec, patch: JsonPatch): Spec {
+  const newSpec = {
+    ...spec,
+    elements: { ...spec.elements },
+    ...(spec.state ? { state: { ...spec.state } } : {}),
+  };
+
+  switch (patch.op) {
+    case "add":
+    case "replace": {
+      setSpecValue(newSpec, patch.path, patch.value);
+      break;
+    }
+    case "remove": {
+      removeSpecValue(newSpec, patch.path);
+      break;
+    }
+    case "move": {
+      if (!patch.from) break;
+      const moveValue = getSpecValue(newSpec, patch.from);
+      removeSpecValue(newSpec, patch.from);
+      setSpecValue(newSpec, patch.path, moveValue);
+      break;
+    }
+    case "copy": {
+      if (!patch.from) break;
+      const copyValue = getSpecValue(newSpec, patch.from);
+      setSpecValue(newSpec, patch.path, copyValue);
+      break;
+    }
+    case "test": {
+      break;
+    }
+  }
+
+  return newSpec;
+}
+
+// =============================================================================
+// useUIStream
+// =============================================================================
+
+export interface UseUIStreamOptions {
+  api: string;
+  onComplete?: (spec: Spec) => void;
+  onError?: (error: Error) => void;
+}
+
+export interface UseUIStreamReturn {
+  spec: Ref<Spec | null>;
+  isStreaming: Ref<boolean>;
+  error: Ref<Error | null>;
+  usage: Ref<TokenUsage | null>;
+  rawLines: Ref<string[]>;
+  send: (prompt: string, context?: Record<string, unknown>) => Promise<void>;
+  clear: () => void;
+}
+
+export function useUIStream({
+  api,
+  onComplete,
+  onError,
+}: UseUIStreamOptions): UseUIStreamReturn {
+  const spec = ref<Spec | null>(null);
+  const isStreaming = ref(false);
+  const error = ref<Error | null>(null);
+  const usage = ref<TokenUsage | null>(null);
+  const rawLines = ref<string[]>([]);
+  let abortController: AbortController | null = null;
+
+  const clear = () => {
+    spec.value = null;
+    error.value = null;
+  };
+
+  const send = async (
+    prompt: string,
+    context?: Record<string, unknown>,
+  ): Promise<void> => {
+    abortController?.abort();
+    abortController = new AbortController();
+
+    isStreaming.value = true;
+    error.value = null;
+    usage.value = null;
+    rawLines.value = [];
+
+    const previousSpec = context?.previousSpec as Spec | undefined;
+    let currentSpec: Spec =
+      previousSpec && previousSpec.root
+        ? { ...previousSpec, elements: { ...previousSpec.elements } }
+        : { root: "", elements: {} };
+    spec.value = currentSpec;
+
+    try {
+      const response = await fetch(api, {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ prompt, context, currentSpec }),
+        signal: abortController.signal,
+      });
+
+      if (!response.ok) {
+        let errorMessage = `HTTP error: ${response.status}`;
+        try {
+          const errorData = await response.json();
+          if (errorData.message) {
+            errorMessage = errorData.message;
+          } else if (errorData.error) {
+            errorMessage = errorData.error;
+          }
+        } catch {
+          // Ignore JSON parsing errors
+        }
+        throw new Error(errorMessage);
+      }
+
+      const reader = response.body?.getReader();
+      if (!reader) {
+        throw new Error("No response body");
+      }
+
+      const decoder = new TextDecoder();
+      let buffer = "";
+
+      while (true) {
+        const { done, value } = await reader.read();
+        if (done) break;
+
+        buffer += decoder.decode(value, { stream: true });
+
+        const lines = buffer.split("\n");
+        buffer = lines.pop() ?? "";
+
+        for (const line of lines) {
+          const trimmed = line.trim();
+          if (!trimmed) continue;
+          const result = parseLine(trimmed);
+          if (!result) continue;
+          if (result.type === "usage") {
+            usage.value = result.usage;
+          } else {
+            rawLines.value = [...rawLines.value, trimmed];
+            currentSpec = applyPatch(currentSpec, result.patch);
+            spec.value = { ...currentSpec };
+          }
+        }
+      }
+
+      if (buffer.trim()) {
+        const trimmed = buffer.trim();
+        const result = parseLine(trimmed);
+        if (result) {
+          if (result.type === "usage") {
+            usage.value = result.usage;
+          } else {
+            rawLines.value = [...rawLines.value, trimmed];
+            currentSpec = applyPatch(currentSpec, result.patch);
+            spec.value = { ...currentSpec };
+          }
+        }
+      }
+
+      onComplete?.(currentSpec);
+    } catch (err) {
+      if ((err as Error).name === "AbortError") {
+        return;
+      }
+      const resolvedError = err instanceof Error ? err : new Error(String(err));
+      error.value = resolvedError;
+      onError?.(resolvedError);
+    } finally {
+      isStreaming.value = false;
+    }
+  };
+
+  onBeforeUnmount(() => {
+    abortController?.abort();
+  });
+
+  return {
+    spec,
+    isStreaming,
+    error,
+    usage,
+    rawLines,
+    send,
+    clear,
+  };
+}
+
+// =============================================================================
+// flatToTree
+// =============================================================================
+
+export function flatToTree(elements: FlatElement[]): Spec {
+  const elementMap: Record<string, UIElement> = {};
+  let root = "";
+
+  for (const element of elements) {
+    elementMap[element.key] = {
+      type: element.type,
+      props: element.props,
+      children: [],
+      visible: element.visible,
+    };
+  }
+
+  for (const element of elements) {
+    if (element.parentKey) {
+      const parent = elementMap[element.parentKey];
+      if (parent) {
+        if (!parent.children) {
+          parent.children = [];
+        }
+        parent.children.push(element.key);
+      }
+    } else {
+      root = element.key;
+    }
+  }
+
+  return { root, elements: elementMap };
+}
+
+// =============================================================================
+// buildSpecFromParts / getTextFromParts
+// =============================================================================
+
+export interface DataPart {
+  type: string;
+  text?: string;
+  data?: unknown;
+}
+
+function isSpecDataPart(data: unknown): data is SpecDataPart {
+  if (typeof data !== "object" || data === null) return false;
+  const obj = data as Record<string, unknown>;
+  switch (obj.type) {
+    case "patch":
+      return typeof obj.patch === "object" && obj.patch !== null;
+    case "flat":
+    case "nested":
+      return typeof obj.spec === "object" && obj.spec !== null;
+    default:
+      return false;
+  }
+}
+
+export function buildSpecFromParts(parts: DataPart[]): Spec | null {
+  const spec: Spec = { root: "", elements: {} };
+  let hasSpec = false;
+
+  for (const part of parts) {
+    if (part.type === SPEC_DATA_PART_TYPE) {
+      if (!isSpecDataPart(part.data)) continue;
+      const payload = part.data;
+      if (payload.type === "patch") {
+        hasSpec = true;
+        applySpecPatch(spec, payload.patch);
+      } else if (payload.type === "flat") {
+        hasSpec = true;
+        Object.assign(spec, payload.spec);
+      } else if (payload.type === "nested") {
+        hasSpec = true;
+        const flat = nestedToFlat(payload.spec);
+        Object.assign(spec, flat);
+      }
+    }
+  }
+
+  return hasSpec ? spec : null;
+}
+
+export function getTextFromParts(parts: DataPart[]): string {
+  return parts
+    .filter(
+      (p): p is DataPart & { text: string } =>
+        p.type === "text" && typeof p.text === "string",
+    )
+    .map((p) => p.text.trim())
+    .filter(Boolean)
+    .join("\n\n");
+}
+
+// =============================================================================
+// useJsonRenderMessage
+// =============================================================================
+
+export function useJsonRenderMessage(parts: Ref<DataPart[]>) {
+  const result = ref<{ spec: Spec | null; text: string }>({
+    spec: null,
+    text: "",
+  });
+
+  let prevParts: DataPart[] = [];
+
+  watch(
+    parts,
+    (newParts) => {
+      const partsChanged =
+        newParts !== prevParts &&
+        (newParts.length !== prevParts.length ||
+          newParts[newParts.length - 1] !== prevParts[prevParts.length - 1]);
+
+      if (partsChanged || prevParts.length === 0) {
+        prevParts = newParts;
+        result.value = {
+          spec: buildSpecFromParts(newParts),
+          text: getTextFromParts(newParts),
+        };
+      }
+    },
+    { immediate: true, deep: true },
+  );
+
+  return {
+    spec: computed(() => result.value.spec),
+    text: computed(() => result.value.text),
+    hasSpec: computed(() => {
+      const s = result.value.spec;
+      return s !== null && Object.keys(s.elements || {}).length > 0;
+    }),
+    result,
+  };
+}
+
+// =============================================================================
+// useChatUI
+// =============================================================================
+
+export interface ChatMessage {
+  id: string;
+  role: "user" | "assistant";
+  text: string;
+  spec: Spec | null;
+}
+
+export interface UseChatUIOptions {
+  api: string;
+  onComplete?: (message: ChatMessage) => void;
+  onError?: (error: Error) => void;
+}
+
+export interface UseChatUIReturn {
+  messages: Ref<ChatMessage[]>;
+  isStreaming: Ref<boolean>;
+  error: Ref<Error | null>;
+  send: (text: string) => Promise<void>;
+  clear: () => void;
+}
+
+let chatMessageIdCounter = 0;
+function generateChatId(): string {
+  if (
+    typeof crypto !== "undefined" &&
+    typeof crypto.randomUUID === "function"
+  ) {
+    return crypto.randomUUID();
+  }
+  chatMessageIdCounter += 1;
+  return `msg-${Date.now()}-${chatMessageIdCounter}`;
+}
+
+export function useChatUI({
+  api,
+  onComplete,
+  onError,
+}: UseChatUIOptions): UseChatUIReturn {
+  const messages = ref<ChatMessage[]>([]);
+  const isStreaming = ref(false);
+  const error = ref<Error | null>(null);
+  let abortController: AbortController | null = null;
+
+  const clear = () => {
+    messages.value = [];
+    error.value = null;
+  };
+
+  const send = async (text: string): Promise<void> => {
+    if (!text.trim()) return;
+
+    abortController?.abort();
+    abortController = new AbortController();
+
+    const userMessage: ChatMessage = {
+      id: generateChatId(),
+      role: "user",
+      text: text.trim(),
+      spec: null,
+    };
+
+    const assistantId = generateChatId();
+    const assistantMessage: ChatMessage = {
+      id: assistantId,
+      role: "assistant",
+      text: "",
+      spec: null,
+    };
+
+    messages.value = [...messages.value, userMessage, assistantMessage];
+    isStreaming.value = true;
+    error.value = null;
+
+    const historyForApi = [
+      ...messages.value
+        .filter((m) => m.id !== assistantId)
+        .map((m) => ({
+          role: m.role,
+          content: m.text,
+        })),
+    ];
+
+    let accumulatedText = "";
+    let currentSpec: Spec = { root: "", elements: {} };
+    let hasSpec = false;
+
+    try {
+      const response = await fetch(api, {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ messages: historyForApi }),
+        signal: abortController.signal,
+      });
+
+      if (!response.ok) {
+        let errorMessage = `HTTP error: ${response.status}`;
+        try {
+          const errorData = await response.json();
+          if (errorData.message) {
+            errorMessage = errorData.message;
+          } else if (errorData.error) {
+            errorMessage = errorData.error;
+          }
+        } catch {
+          // Ignore JSON parsing errors
+        }
+        throw new Error(errorMessage);
+      }
+
+      const reader = response.body?.getReader();
+      if (!reader) {
+        throw new Error("No response body");
+      }
+
+      const decoder = new TextDecoder();
+
+      const parser = createMixedStreamParser({
+        onPatch(patch) {
+          hasSpec = true;
+          applySpecPatch(currentSpec, patch);
+          messages.value = messages.value.map((m) =>
+            m.id === assistantId
+              ? {
+                  ...m,
+                  spec: {
+                    root: currentSpec.root,
+                    elements: { ...currentSpec.elements },
+                    ...(currentSpec.state
+                      ? { state: { ...currentSpec.state } }
+                      : {}),
+                  },
+                }
+              : m,
+          );
+        },
+        onText(line) {
+          accumulatedText += (accumulatedText ? "\n" : "") + line;
+          messages.value = messages.value.map((m) =>
+            m.id === assistantId ? { ...m, text: accumulatedText } : m,
+          );
+        },
+      });
+
+      while (true) {
+        const { done, value } = await reader.read();
+        if (done) break;
+        parser.push(decoder.decode(value, { stream: true }));
+      }
+      parser.flush();
+
+      const finalMessage: ChatMessage = {
+        id: assistantId,
+        role: "assistant",
+        text: accumulatedText,
+        spec: hasSpec
+          ? {
+              root: currentSpec.root,
+              elements: { ...currentSpec.elements },
+              ...(currentSpec.state ? { state: { ...currentSpec.state } } : {}),
+            }
+          : null,
+      };
+      onComplete?.(finalMessage);
+    } catch (err) {
+      if ((err as Error).name === "AbortError") {
+        return;
+      }
+      const resolvedError = err instanceof Error ? err : new Error(String(err));
+      error.value = resolvedError;
+      messages.value = messages.value.filter(
+        (m) => m.id !== assistantId || m.text.length > 0,
+      );
+      onError?.(resolvedError);
+    } finally {
+      isStreaming.value = false;
+    }
+  };
+
+  onBeforeUnmount(() => {
+    abortController?.abort();
+  });
+
+  return {
+    messages,
+    isStreaming,
+    error,
+    send,
+    clear,
+  };
+}
+
+// =============================================================================
+// useBoundProp
+// =============================================================================
+
+export function useBoundProp<T>(
+  propValue: T | undefined,
+  bindingPath: string | undefined,
+): [T | undefined, (value: T) => void] {
+  const { set } = useStateStore();
+  const setValue = (value: T) => {
+    if (bindingPath) set(bindingPath, value);
+  };
+  return [propValue, setValue];
+}

packages/vue/src/index.ts

@@ -0,0 +1,106 @@
+// Composables – State
+export {
+  StateProvider,
+  useStateStore,
+  useStateValue,
+  useStateBinding,
+  StateKey,
+  type StateContextValue,
+  type StateProviderProps,
+} from "./composables/state.js";
+
+// Composables – Visibility
+export {
+  VisibilityProvider,
+  useVisibility,
+  useIsVisible,
+  VisibilityKey,
+  type VisibilityContextValue,
+} from "./composables/visibility.js";
+
+// Composables – Actions
+export {
+  ActionProvider,
+  useActions,
+  useAction,
+  ActionKey,
+  ConfirmDialog,
+  type ActionContextValue,
+  type ActionProviderProps,
+  type PendingConfirmation,
+  type ConfirmDialogProps,
+} from "./composables/actions.js";
+
+// Composables – Validation
+export {
+  ValidationProvider,
+  useValidation,
+  useOptionalValidation,
+  useFieldValidation,
+  ValidationKey,
+  type ValidationContextValue,
+  type ValidationProviderProps,
+  type FieldValidationState,
+} from "./composables/validation.js";
+
+// Composables – Repeat Scope
+export {
+  RepeatScopeProvider,
+  useRepeatScope,
+  RepeatScopeKey,
+  type RepeatScopeValue,
+} from "./composables/repeat-scope.js";
+
+// Schema (Vue's spec format)
+export { schema, type VueSchema, type VueSpec } from "./schema.js";
+
+// Core types (re-exported for convenience)
+export type { Spec, StateStore } from "@json-render/core";
+export { createStateStore } from "@json-render/core";
+
+// Catalog-aware types for Vue
+export type {
+  EventHandle,
+  BaseComponentProps,
+  SetState,
+  StateModel,
+  ComponentContext,
+  ComponentFn,
+  Components,
+  ActionFn,
+  Actions,
+} from "./catalog-types.js";
+
+// Renderer
+export {
+  defineRegistry,
+  type DefineRegistryResult,
+  createRenderer,
+  type CreateRendererProps,
+  type ComponentMap,
+  Renderer,
+  JSONUIProvider,
+  type ComponentRenderProps,
+  type ComponentRenderer,
+  type ComponentRegistry,
+  type RendererProps,
+  type JSONUIProviderProps,
+} from "./renderer.js";
+
+// Hooks / composables (streaming, chat, spec utilities)
+export {
+  useUIStream,
+  useChatUI,
+  useJsonRenderMessage,
+  useBoundProp,
+  flatToTree,
+  buildSpecFromParts,
+  getTextFromParts,
+  type TokenUsage,
+  type UseUIStreamOptions,
+  type UseUIStreamReturn,
+  type UseChatUIOptions,
+  type UseChatUIReturn,
+  type ChatMessage,
+  type DataPart,
+} from "./hooks.js";

packages/vue/src/integration.test.ts

@@ -0,0 +1,384 @@
+import { describe, it, expect } from "vitest";
+import { defineComponent, h, createApp, nextTick, type VNode } from "vue";
+import type { Spec } from "@json-render/core";
+import {
+  JSONUIProvider,
+  Renderer,
+  type ComponentRenderProps,
+} from "./renderer.js";
+import { useStateStore } from "./composables/state.js";
+import { useActions } from "./composables/actions.js";
+import { useBoundProp } from "./hooks.js";
+import type { EventHandle } from "./catalog-types.js";
+
+// =============================================================================
+// Stub components
+// =============================================================================
+
+const Button = defineComponent({
+  name: "Button",
+  props: {
+    element: { type: Object, required: true },
+    emit: { type: Function, required: true },
+    on: { type: Function, required: true },
+    bindings: { type: Object, default: undefined },
+    loading: { type: Boolean, default: false },
+  },
+  setup(props) {
+    return () =>
+      h(
+        "button",
+        {
+          "data-testid": "btn",
+          onClick: () => (props.emit as (e: string) => void)("press"),
+        },
+        (props.element as any).props.label,
+      );
+  },
+});
+
+const Text = defineComponent({
+  name: "Text",
+  props: {
+    element: { type: Object, required: true },
+    emit: { type: Function, required: true },
+    on: { type: Function, required: true },
+    bindings: { type: Object, default: undefined },
+    loading: { type: Boolean, default: false },
+  },
+  setup(props) {
+    return () => {
+      const value = (props.element as any).props.text;
+      return h(
+        "span",
+        { "data-testid": "text" },
+        value == null
+          ? ""
+          : typeof value === "string"
+            ? value
+            : JSON.stringify(value),
+      );
+    };
+  },
+});
+
+const Stack = defineComponent({
+  name: "Stack",
+  props: {
+    element: { type: Object, required: true },
+    emit: { type: Function, required: true },
+    on: { type: Function, required: true },
+    bindings: { type: Object, default: undefined },
+    loading: { type: Boolean, default: false },
+  },
+  setup(_, { slots }) {
+    return () => h("div", { "data-testid": "stack" }, slots.default?.());
+  },
+});
+
+const Input = defineComponent({
+  name: "Input",
+  props: {
+    element: { type: Object, required: true },
+    emit: { type: Function, required: true },
+    on: { type: Function, required: true },
+    bindings: { type: Object, default: undefined },
+    loading: { type: Boolean, default: false },
+  },
+  setup(props) {
+    return () => {
+      const elProps = (props.element as any).props;
+      const [value, setValue] = useBoundProp<string>(
+        elProps.value as string | undefined,
+        (props.bindings as Record<string, string> | undefined)?.value,
+      );
+      return h("input", {
+        "data-testid": "input",
+        value: value ?? "",
+        onInput: (e: Event) => setValue((e.target as HTMLInputElement).value),
+      });
+    };
+  },
+});
+
+const StateProbe = defineComponent({
+  name: "StateProbe",
+  setup() {
+    const { state } = useStateStore();
+    return () =>
+      h("pre", { "data-testid": "state-probe" }, JSON.stringify(state));
+  },
+});
+
+import type { ComponentRegistry } from "./renderer.js";
+
+const registry: ComponentRegistry = { Button, Text, Stack, Input } as any;
+
+// =============================================================================
+// Helpers
+// =============================================================================
+
+function mountApp(spec: Spec, initialState?: Record<string, unknown>) {
+  const container = document.createElement("div");
+
+  const App = defineComponent({
+    setup() {
+      return () =>
+        h(
+          JSONUIProvider,
+          { registry, initialState: initialState ?? spec.state ?? {} },
+          () => [h(Renderer, { spec, registry }), h(StateProbe)],
+        );
+    },
+  });
+
+  const app = createApp(App);
+  app.mount(container);
+
+  const getState = () => {
+    const probe = container.querySelector("[data-testid='state-probe']");
+    return JSON.parse(probe!.textContent!);
+  };
+
+  return { container, app, getState };
+}
+
+// =============================================================================
+// Tests
+// =============================================================================
+
+describe("integration: basic rendering", () => {
+  it("renders a simple spec with text", async () => {
+    const spec: Spec = {
+      root: "main",
+      elements: {
+        main: { type: "Text", props: { text: "Hello World" } },
+      },
+    };
+
+    const { container, app } = mountApp(spec);
+    await nextTick();
+
+    const text = container.querySelector("[data-testid='text']");
+    expect(text?.textContent).toBe("Hello World");
+
+    app.unmount();
+  });
+
+  it("renders nested elements", async () => {
+    const spec: Spec = {
+      root: "stack",
+      elements: {
+        stack: { type: "Stack", props: {}, children: ["t1", "t2"] },
+        t1: { type: "Text", props: { text: "First" } },
+        t2: { type: "Text", props: { text: "Second" } },
+      },
+    };
+
+    const { container, app } = mountApp(spec);
+    await nextTick();
+
+    const texts = container.querySelectorAll("[data-testid='text']");
+    expect(texts.length).toBe(2);
+    expect(texts[0]?.textContent).toBe("First");
+    expect(texts[1]?.textContent).toBe("Second");
+
+    app.unmount();
+  });
+});
+
+describe("integration: state binding", () => {
+  it("resolves $state expressions in props", async () => {
+    const spec: Spec = {
+      root: "main",
+      state: { greeting: "Hello from state" },
+      elements: {
+        main: { type: "Text", props: { text: { $state: "/greeting" } } },
+      },
+    };
+
+    const { container, app } = mountApp(spec);
+    await nextTick();
+
+    const text = container.querySelector("[data-testid='text']");
+    expect(text?.textContent).toBe("Hello from state");
+
+    app.unmount();
+  });
+});
+
+describe("integration: actions", () => {
+  it("executes setState via action context", async () => {
+    let storeRef: ReturnType<typeof useStateStore> | undefined;
+    let actionsRef: { execute: (b: any) => Promise<void> } | undefined;
+
+    const Probe = defineComponent({
+      name: "ActionProbe",
+      setup() {
+        storeRef = useStateStore();
+        const { execute } = useActions();
+        actionsRef = { execute };
+        return () => null;
+      },
+    });
+
+    const container = document.createElement("div");
+    const App = defineComponent({
+      setup() {
+        return () =>
+          h(
+            JSONUIProvider,
+            { registry, initialState: { clicked: false } },
+            () => h(Probe),
+          );
+      },
+    });
+
+    const app = createApp(App);
+    app.mount(container);
+    await nextTick();
+
+    expect(storeRef!.get("/clicked")).toBe(false);
+
+    await actionsRef!.execute({
+      action: "setState",
+      params: { statePath: "/clicked", value: true },
+    });
+
+    expect(storeRef!.get("/clicked")).toBe(true);
+
+    app.unmount();
+  });
+
+  it("chains pushState and setState with $state resolution", async () => {
+    let storeRef: ReturnType<typeof useStateStore> | undefined;
+    let actionsRef: { execute: (b: any) => Promise<void> } | undefined;
+
+    const Probe = defineComponent({
+      name: "ActionProbe",
+      setup() {
+        storeRef = useStateStore();
+        const { execute } = useActions();
+        actionsRef = { execute };
+        return () => null;
+      },
+    });
+
+    const container = document.createElement("div");
+    const App = defineComponent({
+      setup() {
+        return () =>
+          h(
+            JSONUIProvider,
+            {
+              registry,
+              initialState: { items: ["initial"], observed: "not yet set" },
+            },
+            () => h(Probe),
+          );
+      },
+    });
+
+    const app = createApp(App);
+    app.mount(container);
+    await nextTick();
+
+    await actionsRef!.execute({
+      action: "pushState",
+      params: { statePath: "/items", value: "new-item" },
+    });
+
+    await actionsRef!.execute({
+      action: "setState",
+      params: {
+        statePath: "/observed",
+        value: { $state: "/items" },
+      },
+    });
+
+    expect(storeRef!.get("/items")).toEqual(["initial", "new-item"]);
+    expect(storeRef!.get("/observed")).toEqual(["initial", "new-item"]);
+
+    app.unmount();
+  });
+});
+
+describe("integration: visibility", () => {
+  it("hides elements when visible is false", async () => {
+    const spec: Spec = {
+      root: "stack",
+      state: { show: false },
+      elements: {
+        stack: { type: "Stack", props: {}, children: ["hidden", "visible"] },
+        hidden: {
+          type: "Text",
+          props: { text: "Hidden" },
+          visible: { $state: "/show" },
+        },
+        visible: { type: "Text", props: { text: "Visible" } },
+      },
+    };
+
+    const { container, app } = mountApp(spec);
+    await nextTick();
+
+    const texts = container.querySelectorAll("[data-testid='text']");
+    expect(texts.length).toBe(1);
+    expect(texts[0]?.textContent).toBe("Visible");
+
+    app.unmount();
+  });
+
+  it("shows elements when visible condition is true", async () => {
+    const spec: Spec = {
+      root: "stack",
+      state: { show: true },
+      elements: {
+        stack: { type: "Stack", props: {}, children: ["conditional"] },
+        conditional: {
+          type: "Text",
+          props: { text: "Shown" },
+          visible: { $state: "/show" },
+        },
+      },
+    };
+
+    const { container, app } = mountApp(spec);
+    await nextTick();
+
+    const texts = container.querySelectorAll("[data-testid='text']");
+    expect(texts.length).toBe(1);
+    expect(texts[0]?.textContent).toBe("Shown");
+
+    app.unmount();
+  });
+});
+
+describe("integration: repeat", () => {
+  it("renders repeated elements from state array", async () => {
+    const spec: Spec = {
+      root: "list",
+      state: { items: ["apple", "banana", "cherry"] },
+      elements: {
+        list: {
+          type: "Stack",
+          props: {},
+          repeat: { statePath: "/items" },
+          children: ["item"],
+        },
+        item: {
+          type: "Text",
+          props: { text: { $item: "." } },
+        },
+      },
+    };
+
+    const { container, app } = mountApp(spec);
+    await nextTick();
+
+    const texts = container.querySelectorAll("[data-testid='text']");
+    expect(texts.length).toBe(3);
+
+    app.unmount();
+  });
+});

packages/vue/src/renderer.test.ts

@@ -0,0 +1,76 @@
+import { describe, it, expect } from "vitest";
+import { h, createApp, defineComponent } from "vue";
+import { Renderer, type ComponentRenderer } from "./renderer.js";
+
+describe("Renderer", () => {
+  it("renders nothing for null spec", () => {
+    let rendered = false;
+    const App = defineComponent({
+      setup() {
+        return () => {
+          rendered = true;
+          return h(Renderer, { spec: null, registry: {} });
+        };
+      },
+    });
+
+    const container = document.createElement("div");
+    const app = createApp(App);
+    app.mount(container);
+    expect(rendered).toBe(true);
+    expect(container.innerHTML).toBe("<!---->"); // Vue comment node for null
+    app.unmount();
+  });
+
+  it("renders nothing for spec without root", () => {
+    const App = defineComponent({
+      setup() {
+        return () =>
+          h(Renderer, { spec: { root: "", elements: {} }, registry: {} });
+      },
+    });
+
+    const container = document.createElement("div");
+    const app = createApp(App);
+    app.mount(container);
+    expect(container.innerHTML).toBe("<!---->");
+    app.unmount();
+  });
+
+  it("accepts loading prop", () => {
+    const App = defineComponent({
+      setup() {
+        return () => h(Renderer, { spec: null, registry: {}, loading: true });
+      },
+    });
+
+    const container = document.createElement("div");
+    const app = createApp(App);
+    app.mount(container);
+    app.unmount();
+  });
+
+  it("accepts fallback prop", () => {
+    const Fallback = defineComponent({
+      setup() {
+        return () => h("div", null, "Unknown component");
+      },
+    });
+
+    const App = defineComponent({
+      setup() {
+        return () =>
+          h(Renderer, {
+            spec: null,
+            registry: {},
+            fallback: Fallback as unknown as ComponentRenderer,
+          });
+      },
+    });
+
+    const container = document.createElement("div");
+    const app = createApp(App);
+    app.mount(container);
+    app.unmount();
+  });
+});

packages/vue/src/renderer.ts

@@ -0,0 +1,844 @@
+import {
+  defineComponent,
+  h,
+  provide,
+  inject,
+  computed,
+  unref,
+  watch,
+  onErrorCaptured,
+  type Component,
+  type ComputedRef,
+  type DefineComponent,
+  type PropType,
+  type Ref,
+  type VNode,
+  type InjectionKey,
+} from "vue";
+import type {
+  UIElement,
+  Spec,
+  ActionBinding,
+  Catalog,
+  SchemaDefinition,
+  StateStore,
+  ComputedFunction,
+} from "@json-render/core";
+import {
+  resolveElementProps,
+  resolveBindings,
+  resolveActionParam,
+  evaluateVisibility,
+  getByPath,
+  type PropResolutionContext,
+} from "@json-render/core";
+import type {
+  Components,
+  Actions,
+  ActionFn,
+  SetState,
+  StateModel,
+  CatalogHasActions,
+  EventHandle,
+} from "./catalog-types.js";
+import { useVisibility } from "./composables/visibility.js";
+import { useActions, ConfirmDialog } from "./composables/actions.js";
+import { useStateStore, StateProvider } from "./composables/state.js";
+import { VisibilityProvider } from "./composables/visibility.js";
+import { ActionProvider } from "./composables/actions.js";
+import { ValidationProvider } from "./composables/validation.js";
+import {
+  RepeatScopeProvider,
+  useRepeatScope,
+} from "./composables/repeat-scope.js";
+
+// ---------------------------------------------------------------------------
+// ComponentRenderProps
+// ---------------------------------------------------------------------------
+
+export interface ComponentRenderProps<P = Record<string, unknown>> {
+  element: UIElement<string, P>;
+  children?: VNode[];
+  emit: (event: string) => void;
+  on: (event: string) => EventHandle;
+  bindings?: Record<string, string>;
+  loading?: boolean;
+}
+
+export type ComponentRenderer<P = Record<string, unknown>> = Component<
+  ComponentRenderProps<P>
+>;
+
+export type ComponentRegistry = Record<string, ComponentRenderer<any>>;
+
+// ---------------------------------------------------------------------------
+// FunctionsContext
+// ---------------------------------------------------------------------------
+
+const EMPTY_FUNCTIONS: Record<string, ComputedFunction> = {};
+
+const FunctionsKey: InjectionKey<
+  | Ref<Record<string, ComputedFunction>>
+  | ComputedRef<Record<string, ComputedFunction>>
+> = Symbol("json-render-functions");
+
+function useFunctions():
+  | Ref<Record<string, ComputedFunction>>
+  | ComputedRef<Record<string, ComputedFunction>> {
+  return inject(
+    FunctionsKey,
+    computed(() => EMPTY_FUNCTIONS),
+  );
+}
+
+// ---------------------------------------------------------------------------
+// ElementErrorBoundary
+// ---------------------------------------------------------------------------
+
+const ElementErrorBoundary = defineComponent({
+  name: "ElementErrorBoundary",
+  props: {
+    elementType: { type: String, required: true },
+  },
+  setup(props, { slots }) {
+    onErrorCaptured((error, _instance, info) => {
+      console.error(
+        `[json-render] Rendering error in <${props.elementType}>:`,
+        error,
+        info,
+      );
+      return false;
+    });
+    return () => slots.default?.();
+  },
+});
+
+// ---------------------------------------------------------------------------
+// ElementRenderer & RepeatChildren
+// ---------------------------------------------------------------------------
+// These two components reference each other recursively, so we declare them
+// with explicit type annotations to satisfy DTS generation.
+
+interface ElementRendererExposed {}
+interface RepeatChildrenExposed {}
+
+const ElementRenderer: DefineComponent<
+  {
+    element: { type: PropType<UIElement>; required: true };
+    spec: { type: PropType<Spec>; required: true };
+    registry: { type: PropType<ComponentRegistry>; required: true };
+    loading: { type: BooleanConstructor; default: false };
+    fallback: { type: PropType<ComponentRenderer>; default: undefined };
+  },
+  ElementRendererExposed
+> = defineComponent({
+  name: "ElementRenderer",
+  props: {
+    element: { type: Object as PropType<UIElement>, required: true },
+    spec: { type: Object as PropType<Spec>, required: true },
+    registry: {
+      type: Object as PropType<ComponentRegistry>,
+      required: true,
+    },
+    loading: { type: Boolean, default: false },
+    fallback: {
+      type: [Object, Function] as PropType<ComponentRenderer>,
+      default: undefined,
+    },
+  },
+  setup(props): () => VNode | null {
+    const repeatScope = useRepeatScope();
+    const { ctx } = useVisibility();
+    const { execute } = useActions();
+    const storeCtx = useStateStore();
+    const functionsRef = useFunctions();
+
+    const fullCtx = computed<PropResolutionContext>(() => {
+      const base: PropResolutionContext = repeatScope
+        ? {
+            ...ctx,
+            repeatItem: repeatScope.item,
+            repeatIndex: repeatScope.index,
+            repeatBasePath: repeatScope.basePath,
+          }
+        : { ...ctx };
+      base.functions = unref(functionsRef);
+      return base;
+    });
+
+    // Watch effect for element.watch
+    let prevWatchValues: Record<string, unknown> | null = null;
+
+    watch(
+      () => {
+        const watchConfig = props.element.watch;
+        if (!watchConfig) return undefined;
+        const values: Record<string, unknown> = {};
+        for (const path of Object.keys(watchConfig)) {
+          values[path] = getByPath(storeCtx.state, path);
+        }
+        return values;
+      },
+      (watchedValues, _old, onCleanup) => {
+        const watchConfig = props.element.watch;
+        if (!watchConfig || !watchedValues) return;
+
+        const prev = prevWatchValues;
+        prevWatchValues = watchedValues;
+
+        // Skip initial
+        if (prev === null) return;
+
+        let cancelled = false;
+        onCleanup(() => {
+          cancelled = true;
+        });
+
+        const paths = Object.keys(watchConfig);
+        void (async () => {
+          for (const path of paths) {
+            if (cancelled) break;
+            if (watchedValues[path] !== prev[path]) {
+              const binding = watchConfig[path];
+              if (!binding) continue;
+              const bindings = Array.isArray(binding) ? binding : [binding];
+              for (const b of bindings) {
+                if (cancelled) break;
+                if (!b.params) {
+                  await execute(b);
+                  continue;
+                }
+                const liveCtx: PropResolutionContext = {
+                  ...fullCtx.value,
+                  stateModel: storeCtx.getSnapshot(),
+                };
+                const resolved: Record<string, unknown> = {};
+                for (const [key, val] of Object.entries(b.params)) {
+                  resolved[key] = resolveActionParam(val, liveCtx);
+                }
+                await execute({ ...b, params: resolved });
+              }
+            }
+          }
+        })().catch(console.error);
+      },
+      { deep: true },
+    );
+
+    return (): VNode | null => {
+      const element = props.element;
+      const currentCtx = fullCtx.value;
+
+      // Visibility
+      const isVisible =
+        element.visible === undefined
+          ? true
+          : evaluateVisibility(element.visible, currentCtx);
+
+      if (!isVisible) return null;
+
+      // Bindings & props
+      const rawProps = element.props as Record<string, unknown>;
+      const elementBindings = resolveBindings(rawProps, currentCtx);
+      const resolvedProps = resolveElementProps(rawProps, currentCtx);
+
+      const resolvedElement =
+        resolvedProps !== element.props
+          ? { ...element, props: resolvedProps }
+          : element;
+
+      // Lookup component
+      const Comp = props.registry[resolvedElement.type] ?? props.fallback;
+      if (!Comp) {
+        console.warn(`No renderer for component type: ${resolvedElement.type}`);
+        return null;
+      }
+
+      // Build emit / on
+      const onBindings = element.on;
+
+      const emit = async (eventName: string): Promise<void> => {
+        const binding = onBindings?.[eventName];
+        if (!binding) return;
+        const actionBindings = Array.isArray(binding) ? binding : [binding];
+        for (const b of actionBindings) {
+          if (!b.params) {
+            await execute(b);
+            continue;
+          }
+          const liveCtx: PropResolutionContext = {
+            ...currentCtx,
+            stateModel: storeCtx.getSnapshot(),
+          };
+          const resolved: Record<string, unknown> = {};
+          for (const [key, val] of Object.entries(b.params)) {
+            resolved[key] = resolveActionParam(val, liveCtx);
+          }
+          await execute({ ...b, params: resolved });
+        }
+      };
+
+      const on = (eventName: string): EventHandle => {
+        const binding = onBindings?.[eventName];
+        if (!binding) {
+          return { emit: () => {}, shouldPreventDefault: false, bound: false };
+        }
+        const actionBindings = Array.isArray(binding) ? binding : [binding];
+        const shouldPreventDefault = actionBindings.some(
+          (b) => b.preventDefault,
+        );
+        return {
+          emit: () => emit(eventName),
+          shouldPreventDefault,
+          bound: true,
+        };
+      };
+
+      // Render children
+      let children: VNode[] | undefined;
+
+      if (resolvedElement.repeat) {
+        children = [
+          h(RepeatChildren, {
+            element: resolvedElement,
+            spec: props.spec,
+            registry: props.registry,
+            loading: props.loading,
+            fallback: props.fallback,
+          }),
+        ];
+      } else if (resolvedElement.children) {
+        children = resolvedElement.children
+          .map((childKey): VNode | null => {
+            const childElement = props.spec.elements[childKey];
+            if (!childElement) {
+              if (!props.loading) {
+                console.warn(
+                  `[json-render] Missing element "${childKey}" referenced as child of "${resolvedElement.type}". This element will not render.`,
+                );
+              }
+              return null;
+            }
+            return h(ElementRenderer, {
+              key: childKey,
+              element: childElement,
+              spec: props.spec,
+              registry: props.registry,
+              loading: props.loading,
+              fallback: props.fallback,
+            });
+          })
+          .filter((v): v is VNode => v !== null);
+      }
+
+      return h(
+        ElementErrorBoundary,
+        { elementType: resolvedElement.type },
+        () =>
+          h(
+            Comp as Component,
+            {
+              element: resolvedElement,
+              emit,
+              on,
+              bindings: elementBindings,
+              loading: props.loading,
+            },
+            children ? () => children : undefined,
+          ),
+      );
+    };
+  },
+  // Cast required: ElementRenderer and RepeatChildren reference each other
+  // recursively, which prevents TypeScript from inferring the component type.
+  // The explicit DefineComponent annotation above provides the correct type.
+}) as any;
+
+const RepeatChildren: DefineComponent<
+  {
+    element: { type: PropType<UIElement>; required: true };
+    spec: { type: PropType<Spec>; required: true };
+    registry: { type: PropType<ComponentRegistry>; required: true };
+    loading: { type: BooleanConstructor; default: false };
+    fallback: { type: PropType<ComponentRenderer>; default: undefined };
+  },
+  RepeatChildrenExposed
+> = defineComponent({
+  name: "RepeatChildren",
+  props: {
+    element: { type: Object as PropType<UIElement>, required: true },
+    spec: { type: Object as PropType<Spec>, required: true },
+    registry: {
+      type: Object as PropType<ComponentRegistry>,
+      required: true,
+    },
+    loading: { type: Boolean, default: false },
+    fallback: {
+      type: [Object, Function] as PropType<ComponentRenderer>,
+      default: undefined,
+    },
+  },
+  setup(props): () => VNode[] {
+    const storeCtx = useStateStore();
+
+    return (): VNode[] => {
+      const repeat = props.element.repeat!;
+      const statePath = repeat.statePath;
+      const items =
+        (getByPath(storeCtx.state, statePath) as unknown[] | undefined) ?? [];
+
+      return items.map((itemValue, index): VNode => {
+        const key =
+          repeat.key && typeof itemValue === "object" && itemValue !== null
+            ? String(
+                (itemValue as Record<string, unknown>)[repeat.key] ?? index,
+              )
+            : String(index);
+
+        const childNodes: VNode[] = (props.element.children ?? [])
+          .map((childKey): VNode | null => {
+            const childElement = props.spec.elements[childKey];
+            if (!childElement) {
+              if (!props.loading) {
+                console.warn(
+                  `[json-render] Missing element "${childKey}" referenced as child of "${props.element.type}" (repeat). This element will not render.`,
+                );
+              }
+              return null;
+            }
+            return h(ElementRenderer, {
+              key: childKey,
+              element: childElement,
+              spec: props.spec,
+              registry: props.registry,
+              loading: props.loading,
+              fallback: props.fallback,
+            });
+          })
+          .filter((v): v is VNode => v !== null);
+
+        return h(
+          RepeatScopeProvider,
+          {
+            key,
+            item: itemValue,
+            index,
+            basePath: `${statePath}/${index}`,
+          },
+          () => childNodes,
+        );
+      });
+    };
+  },
+  // Cast required: see ElementRenderer comment above (mutual recursion).
+}) as any;
+
+// ---------------------------------------------------------------------------
+// Renderer
+// ---------------------------------------------------------------------------
+
+export interface RendererProps {
+  spec: Spec | null;
+  registry: ComponentRegistry;
+  loading?: boolean;
+  fallback?: ComponentRenderer;
+}
+
+export const Renderer = defineComponent({
+  name: "Renderer",
+  props: {
+    spec: {
+      type: Object as PropType<Spec | null>,
+      default: null,
+    },
+    registry: {
+      type: Object as PropType<ComponentRegistry>,
+      required: true,
+    },
+    loading: { type: Boolean, default: false },
+    fallback: {
+      type: [Object, Function] as PropType<ComponentRenderer>,
+      default: undefined,
+    },
+  },
+  setup(props) {
+    return () => {
+      if (!props.spec || !props.spec.root) return null;
+
+      const rootElement = props.spec.elements[props.spec.root];
+      if (!rootElement) return null;
+
+      return h(ElementRenderer, {
+        element: rootElement,
+        spec: props.spec,
+        registry: props.registry,
+        loading: props.loading,
+        fallback: props.fallback,
+      });
+    };
+  },
+});
+
+// ---------------------------------------------------------------------------
+// ConfirmationDialogManager
+// ---------------------------------------------------------------------------
+
+const ConfirmationDialogManager = defineComponent({
+  name: "ConfirmationDialogManager",
+  setup() {
+    const actions = useActions();
+
+    return () => {
+      const pending = actions.pendingConfirmation;
+      if (!pending?.action.confirm) return null;
+
+      return h(ConfirmDialog, {
+        confirm: pending.action.confirm,
+        onConfirm: actions.confirm,
+        onCancel: actions.cancel,
+      });
+    };
+  },
+});
+
+// ---------------------------------------------------------------------------
+// JSONUIProvider
+// ---------------------------------------------------------------------------
+
+export interface JSONUIProviderProps {
+  registry: ComponentRegistry;
+  store?: StateStore;
+  initialState?: Record<string, unknown>;
+  handlers?: Record<
+    string,
+    (params: Record<string, unknown>) => Promise<unknown> | unknown
+  >;
+  navigate?: (path: string) => void;
+  validationFunctions?: Record<
+    string,
+    (value: unknown, args?: Record<string, unknown>) => boolean
+  >;
+  functions?: Record<string, ComputedFunction>;
+  onStateChange?: (changes: Array<{ path: string; value: unknown }>) => void;
+}
+
+export const JSONUIProvider = defineComponent({
+  name: "JSONUIProvider",
+  props: {
+    registry: {
+      type: Object as PropType<ComponentRegistry>,
+      required: true,
+    },
+    store: {
+      type: Object as PropType<StateStore>,
+      default: undefined,
+    },
+    initialState: {
+      type: Object as PropType<Record<string, unknown>>,
+      default: () => ({}),
+    },
+    handlers: {
+      type: Object as PropType<
+        Record<
+          string,
+          (params: Record<string, unknown>) => Promise<unknown> | unknown
+        >
+      >,
+      default: undefined,
+    },
+    navigate: {
+      type: Function as PropType<(path: string) => void>,
+      default: undefined,
+    },
+    validationFunctions: {
+      type: Object as PropType<
+        Record<
+          string,
+          (value: unknown, args?: Record<string, unknown>) => boolean
+        >
+      >,
+      default: undefined,
+    },
+    functions: {
+      type: Object as PropType<Record<string, ComputedFunction>>,
+      default: undefined,
+    },
+    onStateChange: {
+      type: Function as PropType<
+        (changes: Array<{ path: string; value: unknown }>) => void
+      >,
+      default: undefined,
+    },
+  },
+  setup(props, { slots }) {
+    provide(
+      FunctionsKey,
+      computed(() => props.functions ?? EMPTY_FUNCTIONS),
+    );
+
+    return () =>
+      h(
+        StateProvider,
+        {
+          store: props.store,
+          initialState: props.initialState,
+          onStateChange: props.onStateChange,
+        },
+        () =>
+          h(VisibilityProvider, null, () =>
+            h(
+              ValidationProvider,
+              { customFunctions: props.validationFunctions },
+              () =>
+                h(
+                  ActionProvider,
+                  { handlers: props.handlers, navigate: props.navigate },
+                  () => [slots.default?.(), h(ConfirmationDialogManager)],
+                ),
+            ),
+          ),
+      );
+  },
+});
+
+// ============================================================================
+// defineRegistry
+// ============================================================================
+
+export interface DefineRegistryResult {
+  registry: ComponentRegistry;
+  handlers: (
+    getSetState: () => SetState | undefined,
+    getState: () => StateModel,
+  ) => Record<string, (params: Record<string, unknown>) => Promise<void>>;
+  executeAction: (
+    actionName: string,
+    params: Record<string, unknown> | undefined,
+    setState: SetState,
+    state?: StateModel,
+  ) => Promise<void>;
+}
+
+type DefineRegistryOptions<C extends Catalog> = {
+  components?: Components<C>;
+} & (CatalogHasActions<C> extends true
+  ? { actions: Actions<C> }
+  : { actions?: Actions<C> });
+
+type DefineRegistryComponentFn = (ctx: {
+  props: unknown;
+  children?: VNode[];
+  emit: (event: string) => void;
+  on: (event: string) => EventHandle;
+  bindings?: Record<string, string>;
+  loading?: boolean;
+}) => VNode | VNode[] | null;
+
+type DefineRegistryActionFn = (
+  params: Record<string, unknown> | undefined,
+  setState: SetState,
+  state: StateModel,
+) => Promise<void>;
+
+export function defineRegistry<C extends Catalog>(
+  _catalog: C,
+  options: DefineRegistryOptions<C>,
+): DefineRegistryResult {
+  const registry: ComponentRegistry = {};
+  if (options.components) {
+    for (const [name, componentFn] of Object.entries(options.components)) {
+      registry[name] = defineComponent({
+        name: `JR_${name}`,
+        props: {
+          element: { type: Object as PropType<UIElement>, required: true },
+          emit: {
+            type: Function as PropType<(event: string) => void>,
+            required: true,
+          },
+          on: {
+            type: Function as PropType<(event: string) => EventHandle>,
+            required: true,
+          },
+          bindings: {
+            type: Object as PropType<Record<string, string>>,
+            default: undefined,
+          },
+          loading: { type: Boolean, default: false },
+        },
+        setup(compProps, { slots }) {
+          return () => {
+            const children = slots.default?.();
+            return (componentFn as DefineRegistryComponentFn)({
+              props: compProps.element.props,
+              children,
+              emit: compProps.emit as (event: string) => void,
+              on: compProps.on as (event: string) => EventHandle,
+              bindings: compProps.bindings,
+              loading: compProps.loading,
+            });
+          };
+        },
+      });
+    }
+  }
+
+  const actionMap = options.actions
+    ? (Object.entries(options.actions) as Array<
+        [string, DefineRegistryActionFn]
+      >)
+    : [];
+
+  const handlers = (
+    getSetState: () => SetState | undefined,
+    getState: () => StateModel,
+  ): Record<string, (params: Record<string, unknown>) => Promise<void>> => {
+    const result: Record<
+      string,
+      (params: Record<string, unknown>) => Promise<void>
+    > = {};
+    for (const [name, actionFn] of actionMap) {
+      result[name] = async (params) => {
+        const setState = getSetState();
+        const state = getState();
+        if (setState) {
+          await actionFn(params, setState, state);
+        }
+      };
+    }
+    return result;
+  };
+
+  const executeActionFn = async (
+    actionName: string,
+    params: Record<string, unknown> | undefined,
+    setState: SetState,
+    state: StateModel = {},
+  ): Promise<void> => {
+    const entry = actionMap.find(([name]) => name === actionName);
+    if (entry) {
+      await entry[1](params, setState, state);
+    } else {
+      console.warn(`Unknown action: ${actionName}`);
+    }
+  };
+
+  return { registry, handlers, executeAction: executeActionFn };
+}
+
+// ============================================================================
+// createRenderer
+// ============================================================================
+
+export interface CreateRendererProps {
+  spec: Spec | null;
+  store?: StateStore;
+  state?: Record<string, unknown>;
+  onAction?: (actionName: string, params?: Record<string, unknown>) => void;
+  onStateChange?: (changes: Array<{ path: string; value: unknown }>) => void;
+  functions?: Record<string, ComputedFunction>;
+  loading?: boolean;
+  fallback?: ComponentRenderer;
+}
+
+export type ComponentMap<
+  TComponents extends Record<string, { props: unknown }>,
+> = {
+  [K in keyof TComponents]: Component<
+    ComponentRenderProps<
+      TComponents[K]["props"] extends { _output: infer O }
+        ? O
+        : Record<string, unknown>
+    >
+  >;
+};
+
+export function createRenderer<
+  TDef extends SchemaDefinition,
+  TCatalog extends { components: Record<string, { props: unknown }> },
+>(
+  _catalog: Catalog<TDef, TCatalog>,
+  components: ComponentMap<TCatalog["components"]>,
+): Component<CreateRendererProps> {
+  const registry: ComponentRegistry =
+    components as unknown as ComponentRegistry;
+
+  return defineComponent({
+    name: "CatalogRenderer",
+    props: {
+      spec: { type: Object as PropType<Spec | null>, default: null },
+      store: { type: Object as PropType<StateStore>, default: undefined },
+      state: {
+        type: Object as PropType<Record<string, unknown>>,
+        default: undefined,
+      },
+      onAction: {
+        type: Function as PropType<
+          (actionName: string, params?: Record<string, unknown>) => void
+        >,
+        default: undefined,
+      },
+      onStateChange: {
+        type: Function as PropType<
+          (changes: Array<{ path: string; value: unknown }>) => void
+        >,
+        default: undefined,
+      },
+      functions: {
+        type: Object as PropType<Record<string, ComputedFunction>>,
+        default: undefined,
+      },
+      loading: { type: Boolean, default: false },
+      fallback: {
+        type: [Object, Function] as PropType<ComponentRenderer>,
+        default: undefined,
+      },
+    },
+    setup(props) {
+      provide(
+        FunctionsKey,
+        computed(() => props.functions ?? EMPTY_FUNCTIONS),
+      );
+
+      return () => {
+        const actionHandlers = props.onAction
+          ? new Proxy(
+              {} as Record<
+                string,
+                (params: Record<string, unknown>) => void | Promise<void>
+              >,
+              {
+                get: (_target, prop: string) => {
+                  return (params: Record<string, unknown>) =>
+                    props.onAction!(prop, params);
+                },
+                has: () => true,
+              },
+            )
+          : undefined;
+
+        return h(
+          StateProvider,
+          {
+            store: props.store,
+            initialState: props.state,
+            onStateChange: props.onStateChange,
+          },
+          () =>
+            h(VisibilityProvider, null, () =>
+              h(ValidationProvider, null, () =>
+                h(ActionProvider, { handlers: actionHandlers }, () => [
+                  h(Renderer, {
+                    spec: props.spec,
+                    registry,
+                    loading: props.loading,
+                    fallback: props.fallback,
+                  }),
+                  h(ConfirmationDialogManager),
+                ]),
+              ),
+            ),
+        );
+      };
+    },
+  });
+}

packages/vue/src/schema.ts

@@ -0,0 +1,80 @@
+import { defineSchema } from "@json-render/core";
+
+/**
+ * The schema for @json-render/vue
+ *
+ * Defines:
+ * - Spec: A flat tree of elements with keys, types, props, and children references
+ * - Catalog: Components with props schemas, and optional actions
+ */
+export const schema = defineSchema(
+  (s) => ({
+    spec: s.object({
+      root: s.string(),
+      elements: s.record(
+        s.object({
+          type: s.ref("catalog.components"),
+          props: s.propsOf("catalog.components"),
+          children: s.array(s.string()),
+          visible: s.any(),
+        }),
+      ),
+    }),
+
+    catalog: s.object({
+      components: s.map({
+        props: s.zod(),
+        slots: s.array(s.string()),
+        description: s.string(),
+        example: s.any(),
+      }),
+      actions: s.map({
+        params: s.zod(),
+        description: s.string(),
+      }),
+    }),
+  }),
+  {
+    builtInActions: [
+      {
+        name: "setState",
+        description:
+          "Update a value in the state model at the given statePath. Params: { statePath: string, value: any }",
+      },
+      {
+        name: "pushState",
+        description:
+          'Append an item to an array in state. Params: { statePath: string, value: any, clearStatePath?: string }. Value can contain {"$state":"/path"} refs and "$id" for auto IDs.',
+      },
+      {
+        name: "removeState",
+        description:
+          "Remove an item from an array in state by index. Params: { statePath: string, index: number }",
+      },
+      {
+        name: "validateForm",
+        description:
+          "Validate all registered form fields and write the result to state. Params: { statePath?: string }. Defaults to /formValidation. Result: { valid: boolean }.",
+      },
+    ],
+    defaultRules: [
+      "CRITICAL INTEGRITY CHECK: Before outputting ANY element that references children, you MUST have already output (or will output) each child as its own element. If an element has children: ['a', 'b'], then elements 'a' and 'b' MUST exist. A missing child element causes that entire branch of the UI to be invisible.",
+      "SELF-CHECK: After generating all elements, mentally walk the tree from root. Every key in every children array must resolve to a defined element. If you find a gap, output the missing element immediately.",
+      'CRITICAL: The "visible" field goes on the ELEMENT object, NOT inside "props". Correct: {"type":"<ComponentName>","props":{},"visible":{"$state":"/tab","eq":"home"},"children":[...]}.',
+      'CRITICAL: The "on" field goes on the ELEMENT object, NOT inside "props". Use on.press, on.change, on.submit etc. NEVER put action/actionParams inside props.',
+      "When the user asks for a UI that displays data (e.g. blog posts, products, users), ALWAYS include a state field with realistic sample data. The state field is a top-level field on the spec (sibling of root/elements).",
+      'When building repeating content backed by a state array (e.g. posts, products, items), use the "repeat" field on a container element. Example: { "type": "<ContainerComponent>", "props": {}, "repeat": { "statePath": "/posts", "key": "id" }, "children": ["post-card"] }. Replace <ContainerComponent> with an appropriate component from the AVAILABLE COMPONENTS list. Inside repeated children, use { "$item": "field" } to read a field from the current item, and { "$index": true } for the current array index. For two-way binding to an item field use { "$bindItem": "completed" }. Do NOT hardcode individual elements for each array item.',
+      "Design with visual hierarchy: use container components to group content, heading components for section titles, proper spacing, and status indicators. ONLY use components from the AVAILABLE COMPONENTS list.",
+      "For data-rich UIs, use multi-column layout components if available. For forms and single-column content, use vertical layout components. ONLY use components from the AVAILABLE COMPONENTS list.",
+      "Always include realistic, professional-looking sample data. For blogs include 3-4 posts with varied titles, authors, dates, categories. For products include names, prices, images. Never leave data empty.",
+    ],
+  },
+);
+
+export type VueSchema = typeof schema;
+
+export type VueSpec<TCatalog> = typeof schema extends {
+  createCatalog: (catalog: TCatalog) => { _specType: infer S };
+}
+  ? S
+  : never;

packages/vue/tsconfig.json

@@ -0,0 +1,9 @@
+{
+  "extends": "@internal/typescript-config/vue-library.json",
+  "compilerOptions": {
+    "outDir": "dist",
+    "rootDir": "src"
+  },
+  "include": ["src"],
+  "exclude": ["node_modules", "dist"]
+}