Vtex Io Render Runtime And Blocks

Render Runtime & Block Registration

When this skill applies

Use this skill when a VTEX IO storefront component needs to be exposed to Store Framework as a block.

• Registering components in store/interfaces.json
• Mapping block names to React components
• Defining block composition and allowed children
• Reviewing whether a component is correctly wired into theme JSON

Do not use this skill for:

• shopper-facing component internals
• admin interfaces
• backend service or route design
• policy modeling

Decision rules

• Every block visible to Store Framework must be registered in store/interfaces.json.
• Keep block names, component mapping, and composition explicit.
• The block ID used as the key in store/interfaces.json, for example product-reviews, is the same ID that storefront themes reference under blocks in store/*.json.
• The component field should map to the React entry name under react/, such as ProductReviews, or a nested path such as product/ProductReviews when the app structure is hierarchical.
• Use composition intentionally when the block needs an explicit child model. children means the component renders nested blocks through props.children, while blocks means the block exposes named block slots controlled by Store Framework.
• composition is optional. For many simple blocks, declaring component and, when needed, allowed is enough.
• Block IDs are scoped by the declaring app's MAJOR version. vtex.pages-graphql resolves a block reference such as acme-related-products against acme.product-widgets@MAJOR.x:acme-related-products for the major actually installed in the workspace. A block declared in 0.x is not the same block as one declared in 5.x, even if the ID is identical.
• A consumer theme that references a block ID through store/blocks.json only sees the block if the declaring app is installed at a major matching the dependency range. Mismatches surface as Missing block vendor.app@MAJOR.x:block-id errors at the resolver and break the page.
• Use this skill for the render/runtime contract, and use storefront/admin skills for the component implementation itself.

Hard constraints

Constraint: Storefront blocks must be declared in interfaces.json

Every React component intended for Store Framework use MUST have a corresponding interfaces.json entry.

Why this matters

Without the interface declaration, the component cannot be referenced from theme JSON.

Detection

If a storefront React component is intended to be used as a block but has no matching interface entry, STOP and add it first.

Correct

{
  "product-reviews": {
    "component": "ProductReviews"
  }
}

Wrong

// react/ProductReviews.tsx exists with no interfaces.json mapping

Constraint: Component mapping must resolve to real React entry files

The component field in interfaces.json MUST map to a real exported React entry file.

Why this matters

Broken mapping silently disconnects block contracts from implementation.

Detection

If an interface points to a component name with no corresponding React entry file, STOP and fix the mapping.

Correct

{
  "product-reviews": {
    "component": "ProductReviews"
  }
}

Wrong

{
  "product-reviews": {
    "component": "MissingComponent"
  }
}

Constraint: Block IDs must resolve under the installed major of the declaring app

Block IDs referenced from a theme app's store/blocks.json MUST resolve to an interfaces.json entry in an installed app whose MAJOR version matches the consumer's dependency range. The render-time resolver is keyed by vendor.app@MAJOR.x:block-id, not by the bare block ID.

Why this matters

vtex.pages-graphql uses the declaring app's major version as part of the block lookup. A block that exists in acme.product-widgets@0.x is not visible to a consumer that resolves acme.product-widgets@5.x, even if the block ID is identical. Mismatches return Missing block errors at the GraphQL layer and the page falls back to default content or fails outright.

Detection

If a consumer theme references a block ID and the declaring app's installed major does not match the consumer's dependency range, STOP and align the dependency range or move the block declaration to the correct major.

Correct

// consumer theme manifest.json
{ "dependencies": { "acme.product-widgets": "0.x" } }

// acme.product-widgets@0.x ships store/interfaces.json with:
{ "acme-related-products": { "component": "RelatedProducts" } }

// consumer theme store/blocks.json
{ "store.product": { "children": ["acme-related-products"] } }

Wrong

// consumer theme depends on acme.product-widgets@0.x
// but the block "acme-related-products" was added in @5.x and never backported
{ "store.product": { "children": ["acme-related-products"] } }

The resolver returns Missing block acme.product-widgets@0.x:acme-related-products.

Constraint: Block composition must be intentional

Composition and allowed child blocks MUST match the component's actual layout and runtime expectations.

Why this matters

Incorrect composition contracts make theme usage brittle and confusing.

Detection

If allowed or composition do not reflect how the component is supposed to receive children, STOP and correct the block contract.

Correct

{
  "product-reviews": {
    "component": "ProductReviews",
    "composition": "children",
    "allowed": ["product-review-item"]
  }
}

Wrong

{
  "product-reviews": {
    "component": "ProductReviews",
    "composition": "blocks",
    "allowed": []
  }
}

Preferred pattern

Keep block contracts explicit in interfaces.json and keep block implementation concerns separate from render-runtime registration.

Minimal block lifecycle:

// store/interfaces.json
{
  "product-reviews": {
    "component": "ProductReviews",
    "composition": "children",
    "allowed": ["product-review-item"]
  },
  "product-review-item": {
    "component": "ProductReviewItem"
  }
}

// store/home.json
{
  "store.home": {
    "blocks": ["product-reviews"]
  }
}

// react/ProductReviews.tsx
export default function ProductReviews() {
  return <div>...</div>
}

This wiring makes the block name visible in the theme, maps it to a real React entry, and keeps composition rules explicit at the render-runtime boundary.

Common failure modes

• Forgetting to register a storefront component as a block.
• Mapping block names to missing React entry files.
• Using the wrong composition model.
• Adding a new block to a 5.x line and assuming consumers depending on 0.x will see it. Block visibility is scoped by the declaring app's installed major.
• Renaming a block ID without coordinating with consumer themes that already reference it; the rename is effectively a breaking change for stored content.

Review checklist

• Is the block declared in interfaces.json?
• Does the component mapping resolve correctly?
• Are composition and allowed children intentional?
• Is runtime registration clearly separated from component internals?
• Is the declaring app installed at a major that matches every consumer's dependency range?

Related skills

• vtex-io-storefront-theme-app — Use when the question is how a consumer theme composes these blocks into pages and routes.
• vtex-io-storefront-theme-versioning — Use when the question is how a major version change in a block-declaring app affects merchants who already reference those blocks in stored content.

Reference

• Store Framework - Block and theme context
• Interfaces — How interfaces.json maps block IDs to React components and how block IDs are namespaced by app major.