Imported from BuilderIO/builder-agent-skills (fusion-to-publish-v2/SKILL.md). Install upstream with npx skills add BuilderIO/builder-agent-skills --skill fusion-to-publish-v2. Copyright stays with the author.

Fusion to Publish (v2)

Bridge Builder.io Fusion (code generation) and Publish (visual CMS) by registering React components for the visual editor.

What You'll Do

1. Set up Publish integration — scaffold the catch-all route, registry, SDK config, and .builderrules
2. Register a component — read TypeScript props, map to Builder input types, add to registry
3. Bulk-register components — scan a directory and register all components at once

Quick Start: Detect Project State

Before starting any workflow, run this to understand the project's current state:

bash .builder/skills/fusion-to-publish-v2/scripts/detect-project.sh

This outputs the SDK version, Next.js version, app root, registry status, API key status, and catch-all route status. Use this to decide which scaffolding steps to skip.

If the script is not available, detect manually:

1. Check package.json for @builder.io/react (Gen1) or @builder.io/sdk-react (Gen2)
2. Check for src/app/ or app/ directory
3. Check if builder-registry.ts exists at the project root
4. Check .env.local for NEXT_PUBLIC_BUILDER_API_KEY

Workflow 1: Set Up Publish Integration

Run this once per project. Each step is idempotent — skip what already exists.

Prerequisites

• A Next.js App Router project (with app/ or src/app/)
• A Builder.io Publish space with a public API key

Steps

Run the detect script first (see Quick Start above). Then create only what is missing. If a file exists but differs from the expected pattern, show the user and ask how to proceed.

1. Ensure SDK is installed. Check package.json for @builder.io/react. If missing, install it along with @builder.io/dev-tools:

   npm install @builder.io/react @builder.io/dev-tools

2. Configure the API key. Check .env.local for NEXT_PUBLIC_BUILDER_API_KEY. If not found, check .env. If in .env but not .env.local, warn the user: "Your API key is in .env, which may be committed to version control. Consider moving it to .env.local." If not found anywhere, ask the user for their Builder.io public API key. Write it to .env.local. Ensure .gitignore includes .env*.local. Create .env.example with NEXT_PUBLIC_BUILDER_API_KEY=your-builder-public-api-key.

3. Create builder-registry.ts at the project root. See references/scaffolding-templates.md for the exact template. Key points:

   • Must have "use client" directive
   • Initializes the client-side SDK via @builder.io/react
   • Uses a runtime guard for the API key (no ! assertion)

4. Create the catch-all route at app/[...page]/page.tsx (or src/app/[...page]/page.tsx). This is a server component that fetches Builder content. See references/scaffolding-templates.md. Key points:

   • Uses @builder.io/sdk (NOT @builder.io/react) for server-side fetching
   • Has its own builder.init() — this is separate from the client-side init in the registry
   • Uses [...page] (required catch-all), NOT [[...page]] (optional), to preserve the user's homepage
   • Detect the Next.js version from package.json for the correct params pattern (Promise in 15+, direct in 14)

   Before creating, check for existing catch-all or dynamic routes ([...page], [[...page]], [...slug]). If found, show the user and ask how to proceed.

5. Create components/builder.tsx (the RenderBuilderContent wrapper). See references/scaffolding-templates.md. Key points:

   • Must have "use client" directive
   • Imports @/builder-registry as a side-effect (triggers all component registrations)
   • Accepts an optional model prop (defaults to "page")

6. Wrap next.config with @builder.io/dev-tools. Check if already wrapped by searching for @builder.io/dev-tools or BuilderDevTools. If found, skip. If the file has BuilderDevTools()(BuilderDevTools()( (double wrapping), fix it. Handle .ts, .js, and .mjs variants.

7. Create or update .builderrules with component creation conventions. Adapt the template to match existing project conventions (e.g., Tailwind vs CSS Modules, src/ vs root). See references/scaffolding-templates.md for the default template.

After Scaffolding

Tell the user: "Publish integration is set up. Deploy your app to a public URL (Vercel, Netlify, etc.) — Builder's visual editor cannot work with localhost. Then use this skill to register components."

Workflow 2: Register a Component

When the user wants to register a component for Publish's visual editor.

Prerequisites

Verify scaffolding is complete: builder-registry.ts exists, the catch-all route exists, SDK is installed. If anything is missing, offer to run Workflow 1 first.

Steps

1. Read the component file. Find the exported props interface or type. If the type is imported from another file, follow the import to resolve it. Skip React-internal types (ReactNode, CSSProperties, MouseEventHandler, HTMLAttributes, etc.).

2. Map props to Builder inputs. Use the type mapping in references/sdk-reference.md. Key rules:

   • Evaluate TypeScript type first, then apply name heuristics only for plain string props
   • String literal unions ('a' | 'b') → type: "text" with enum array (NOT type: "enum")
   • list inputs MUST have defaultValue: []
   • object inputs MUST have defaultValue: {}
   • children: ReactNode → skip the prop, add canHaveChildren: true to the registration
   • Generate friendlyName from PascalCase props (backgroundColor → "Background Color")
   • Generate helperText for non-obvious inputs
   • Use advanced: true for typically-defaulted props (className, id)

3. Generate the registration. Add a Builder.registerComponent() call to builder-registry.ts using dynamic(() => import(...)) with the correct relative path from the registry file (or use the @/ alias). See references/examples.md for complete examples.

4. Optionally update the showcase page. If app/page.tsx has a "Component Showcase" pattern, add the component with sample data. If the homepage is not a showcase page, skip this step.

5. Log the registration. Append an entry to registration-log.json in this skill's directory (see Registration History below).

6. Guide verification. Tell the user:

   • Deploy the updated app
   • Open Builder.io → Publish space → Visual Editor
   • Check the Insert tab → Custom Components → look for the registered component
   • Drag it onto the canvas and verify inputs appear correctly
   • If the component doesn't appear: check that builder-registry.ts is imported in components/builder.tsx, the dynamic import path is correct, and the app is deployed

Workflow 3: Bulk Register Components

Scan a directory and register all unregistered components. Use parallel sub-agents to analyze multiple components simultaneously.

Step 1: Scan

Run the scan script to identify what needs registration:

bash .builder/skills/fusion-to-publish-v2/scripts/scan-components.sh components builder-registry.ts

If the script is not available, scan manually: find .tsx/.jsx files, skip *.test.*, *.spec.*, *.stories.*, *.story.*, *.mock.*, *.d.ts, and barrel files.

Step 2: Analyze in parallel (sub-agents)

For each UNREGISTERED component from the scan, spawn a sub-agent to analyze it independently. All sub-agents run in parallel.

Each sub-agent receives:

• The component file path
• The type mapping rules from references/sdk-reference.md
• The examples from references/examples.md

Each sub-agent does:

1. Read the component file
2. Parse the exported props interface (follow imports if needed)
3. Map each prop to a Builder input using the type mapping rules
4. Generate the complete Builder.registerComponent() code block
5. Return the registration code and a summary (component name, input count, any warnings)

Example sub-agent dispatch:

For each unregistered component, spawn a sub-agent:

Sub-agent 1: "Read components/HeroSection/HeroSection.tsx.
  Parse its props interface.
  Map props to Builder inputs using the type mapping in references/sdk-reference.md.
  Generate a Builder.registerComponent() call.
  Return the complete registration code block."

Sub-agent 2: "Read components/PricingCard/PricingCard.tsx. [same instructions]"

Sub-agent 3: "Read components/TestimonialGrid/TestimonialGrid.tsx. [same instructions]"

All sub-agents run in parallel.

Step 3: Assemble registrations (serial)

After all sub-agents complete, collect their registration code blocks and:

1. Review each registration for correctness (check for warnings from sub-agents)
2. Add all registrations to builder-registry.ts — append them sequentially. Add the import dynamic from "next/dynamic" at the top if not already present.
3. Log each registration to registration-log.json

This step must be serial because all registrations write to the same file.

Step 4: Report results

Summarize: how many registered, skipped (already registered), and failed (with reasons from sub-agents).

If a sub-agent fails to analyze a component (e.g., complex types that can't be resolved), report the failure but don't block other registrations.

Registration History

After each successful registration, append an entry to registration-log.json in this skill's directory:

{
  "registrations": [
    {
      "component": "HeroSection",
      "file": "components/HeroSection/HeroSection.tsx",
      "registeredAt": "2026-03-19T20:30:00Z",
      "inputCount": 5,
      "notes": "Container with canHaveChildren"
    }
  ]
}

Before registering a component, check this log. If a component was previously registered but is no longer in builder-registry.ts, note this for the user — it may have been intentionally removed.

Gotchas

These are the most common failure modes. Check here first when debugging.

1. list and object inputs require defaultValue. Without defaultValue: [] (list) or defaultValue: {} (object), Builder errors when adding the component to a page. Non-obvious and causes "component won't load" debugging.

2. enum requires type: "text" with an enum array. There is no type: "enum" in Builder. Using it causes the input to silently not render.

3. Two separate builder.init() calls are correct. The catch-all route uses @builder.io/sdk (server-side), and builder-registry.ts uses @builder.io/react (client-side). These are different packages. Both need initialization. Do NOT "fix" this by removing one.

4. API key must be in the deployment environment. .env.local works locally but is not deployed. Users must add NEXT_PUBLIC_BUILDER_API_KEY in their hosting platform's environment settings. This is the #1 "it doesn't work in production" cause.

5. Side-effect import path must be correct. import "@/builder-registry" in components/builder.tsx is what triggers component registrations. If this path is wrong, the build succeeds but no custom components appear in the editor. Verify this import first when debugging missing components.

6. Dynamic import path is relative to builder-registry.ts. If the registry is at the project root and the component is at components/Hero/Hero.tsx, the import must be ./components/Hero/Hero. Wrong paths cause the component to register but render blank.

7. Double BuilderDevTools wrapping. The f2p template has a bug: BuilderDevTools()(BuilderDevTools()(nextConfig)). Always check for existing wrapping before adding it.

8. Next.js 15+ params is a Promise. Must be awaited. Next.js 14 uses params directly. Check the version in package.json.

9. [...page] does not handle the root path /. If the user needs Builder to manage the homepage, they need to add Builder content fetching to app/page.tsx separately, or switch to [[...page]] and remove app/page.tsx.

10. CSP headers may block the visual editor. Builder's editor loads the deployed site in an iframe. If the app sets X-Frame-Options or CSP frame-ancestors, it must allow https://*.builder.io.

When to Use What

Anti-Patterns

• Never use type: "enum". Use type: "text" with an enum array.
• Never skip defaultValue on list/object inputs. Builder will error.
• Never use [[...page]] if the user has a homepage. It conflicts with app/page.tsx.
• Never write API keys to .env (only .env.local).
• Never wrap BuilderDevTools() twice.
• Never register event handlers, CSSProperties, or HTML attributes as Builder inputs.
• Never remove either builder.init() call. Server and client inits serve different purposes.

Audit Checklist

After registering a component, verify:

• builder-registry.ts has "use client" directive
• Dynamic import path resolves to the correct component file
• All list inputs have defaultValue: []
• All object inputs have defaultValue: {}
• Enum props use type: "text" with enum array
• No event handlers, CSSProperties, or HTML attributes in inputs
• children prop is handled via canHaveChildren: true, not as an input
• Required props have required: true
• API key is set in both .env.local and deployment environment

Scripts

This skill includes helper scripts in scripts/:

• detect-project.sh — Detects project structure, SDK version, scaffolding status. Run at the start of any workflow.
• scan-components.sh — Scans a directory for React components and checks registration status. Used in Workflow 3.

Reference Files

For complete SDK API reference and type mapping table, see references/sdk-reference.md.

For exact scaffolding file templates, see references/scaffolding-templates.md.

For end-to-end component registration examples, see references/examples.md.