Frontmatter Core

Zero-runtime CMS bridge for Astro → CMS adapters

What is this

Frontmatter Core is a developer tool that turns your Astro project into a CMS-ready data model.

It scans your Astro files, Markdown pages and YAML datasets, and produces a clean, structured representation of:

• Pages
• Editable fields
• Components
• Data collections

This representation is written into a .frontmatter/ folder and can then be consumed by adapters (for example: flat-file CMS or headless CMS implementations) to generate CMS themes, blueprints, and content structures.

Frontmatter does not run in production. It is a build-time tool.

Your Astro site remains fast, static and framework-free.
The CMS only edits data.
Your design stays untouched.

---

Scope

This repository contains the core engine only.

It builds a stable, versioned Intermediate Representation (IR).
Adapters, reference implementations, and examples live outside the core.

---

Stability

Frontmatter Core exposes a versioned Intermediate Representation (IR).

IR v1 is stable (schemaVersion: 2).

• Backward-compatible additions only.
• Breaking changes will only happen in a future IR v2 and will be documented.

What it does

Frontmatter Core reads:

• .astro files (components and pages)
• .md, .mdoc, .markdown pages
• .yml and .yaml datasets (in src/data)

From those files it extracts:

From Astro

• Exported props from export interface Props
• Props destructured from Astro.props
• Component usage (for example: <Hero />, <Gallery />)

From Markdown

• YAML frontmatter fields

From YAML datasets

• Structured collections (lists and objects)

It builds a unified Internal Representation (IR) describing your site.

Field rules

Each extracted field includes:

• key: the field name
• type: string | number | boolean | unknown (best-effort)
• required: when true, missing values should be treated as validation errors by consumers
• default (optional): a fallback value when provided
• rawType (optional): best-effort original type information (e.g. TypeScript annotation)
• source (optional): where the field was extracted from (astro, markdown, yaml)

Frontmatter Core itself does not enforce content presence at runtime; required is part of the data contract.

Type extraction is best-effort. Complex TypeScript types may be reduced to unknown.

Component usage

For each page, components[] lists the components directly referenced in that page file (non-transitive).
It does not include components used inside other components or layouts.
componentsIndex is an index of parsed .astro files (components and pages).

What you get

After running:

frontmatter scan

You get:

.frontmatter/
  build.json     → the full site model
  manifest.json  → file hashes for sync
  errors.json    → validation errors if any

This is the source of truth for adapters.

Why this exists

Most CMS workflows destroy frontend quality.

You design in Figma, then re-build badly in WordPress.

Frontmatter flips the workflow:

You design and build in Astro first.
Then you expose only the data to a CMS.

Developers own structure and layout.
Editors only touch content.

This is not a site builder.
This is not a WYSIWYG.
This is a data layer.

Install (npm)

Frontmatter Core can be used directly via npm.

Install as a dependency:

pnpm add @withfrontmatter/core

Or run it without installation:

npx @withfrontmatter/core scan

This will generate the .frontmatter/ directory in your Astro project.

Install (development)

From the repository root:

pnpm install
pnpm build
pnpm link --global

This exposes the CLI:

frontmatter

or

fm

Usage

In any Astro project:

frontmatter scan

This creates .frontmatter/ in the project.

You can validate the output:

frontmatter validate

Supported inputs

Pages

• src/pages/*.astro
• src/pages/*.md
• src/pages/*.mdoc
• src/pages/*.markdown

Components

src/components/*.astro

Datasets

• src/data/*.yml
• src/data/*.yaml

Core philosophy

Astro controls:

• Layout
• Markup
• SEO
• Components

CMS controls:

• Text
• Images
• Lists
• Metadata

They never fight.

What this repo is

This is the core engine only.

It does not:

• Generate CMS themes
• Talk to Grav
• Render anything

Adapters do that.

Non-goals

Frontmatter Core does not:

• Act as a CMS
• Provide a user interface
• Manage content, users or permissions
• Guarantee compatibility with any CMS
• Provide hosting, syncing or deployment

Frontmatter Core produces a data contract. What you build on top of it is your responsibility.

Commercial editions

This repository contains the core engine only.

Commercial editions may exist that package:

• Reference adapters
• Templates
• Scripts and tooling around the core

These editions do not change the core behavior. They provide convenience and packaging, not managed services.

No compatibility, support or upgrade guarantees are implied.

Support

This project is provided as-is.

There is no guaranteed support, SLA, or compatibility promise. Issues and discussions are community-driven.

License

MIT

Status

This is an early developer release.
The internal schema is versioned and designed to be stable.
Breaking changes, if any, will be explicit and documented.