An accessibility-first, metadata-driven static site generator. Markdown in, an accessible website out — WCAG-aware output by default, plus a metadata layer (Gnosis) that renders pages from typed project data. The Haskell member of poly-ssg.

Note

Status: alpha. The build / clean pipeline works and generates real sites. Items marked Planned below are not yet implemented. The engine’s direction — demote Pandoc, adopt a Djot prose core + a2ml typed content on the boj substrate — is recorded in ADR-0001. Architecture & invariants: EXPLAINME.

Example

A minimal site is a tree of Markdown with front-matter:

content/
├── index.md
└── posts/
    └── 2026-06-23-hello.md

---
title: Hello, world
date: 2026-06-23
tags: [intro]
description: A first page built with casket.
---
# Hello

Markdown with **rich** formatting, tables, footnotes and highlighted code.

Build it:

casket-ssg build ./content ./_site

You get an accessible _site/ with no configuration:

• index.html and posts/2026-06-23-hello/index.html rendered through an accessible default theme (skip link, labelled landmarks, light/dark color-scheme), with table headers auto-scoped for WCAG 1.3.1;

• a date-sorted collection index for posts/, and per-tag pages under /tags/;

• sitemap.xml and an Atom feed.xml.

No Node, no npm, no required config file.

Installation

casket is not yet on Hackage — build from source (GHC 9.4+, Cabal 3 or Stack 2):

git clone https://github.com/hyperpolymath/casket-ssg
cd casket-ssg
stack build                         # or: cabal build
stack run casket-ssg -- --version   # or put the built binary on PATH

CLI:

casket-ssg build <input-dir> [output-dir]   # default output: _site
casket-ssg build --drafts <input-dir>       # include draft: true pages (or CASKET_DRAFTS=1)
casket-ssg build --no-clean-urls <input-dir> # emit foo.html, not foo/index.html
casket-ssg clean [output-dir]
casket-ssg --version

What makes it different

Accessibility by construction
The default theme is accessible by default, casket rewrites Pandoc table headers to add scope="col", and the Gnosis FlexiText type makes empty alt-text a constructor error — generated badges cannot ship without alt text. Accessibility is a property of the engine, not a checklist for the author.

Metadata-driven (Gnosis)
An optional layer renders pages from a typed metadata context: (:placeholder) substitution, {{#if}} / {{#for}} conditionals and loops (DAX), and Shields.io badges generated from typed values — sourced from the repo’s .machine_readable/descriptiles/ data.

Verified & agent-native — the trajectory
casket is heading toward typed a2ml content (build fails on malformed data), a formally-verifiable Djot core, and a verified agent surface as a boj cartridge rather than an embedded MCP server. See ADR-0001.

Permissively licensed
MPL-2.0 — build proprietary or differently-licensed sites on top, unlike copyleft alternatives.

Features

Implemented

• Recursive multi-page build mirroring the source tree

• Front-matter: title, date, description, layout, draft, tags, slug, plus arbitrary keys as {{key}} template vars

• Rich Markdown via Pandoc — anchors, pipe tables, fenced/highlighted code, footnotes, task lists, strikethrough, smart punctuation

• File templates with per-page layout, partials ({{> name}}), {{nav}}, {macro}, {{site.*}} (from site.conf)

• Collections (date-sorted directory index) and per-tag pages (/tags/<tag>/)

• sitemap.xml + Atom feed.xml

• Accessible default theme + automatic scope="col" on table headers

• Gnosis layer — (:placeholder), {{#if}}/{{#for}} (DAX), FlexiText badges

• Clean URLs, toggleable

Planned (do not assume these work today — see ADR-0001)

• init scaffolding and a serve / live-reload dev server

• Incremental rebuilds; asset fingerprinting

• a2ml-native typed content + the Djot core; Pandoc relegated to an importer

• boj cartridge registration; llms.txt / per-page machine views

Documentation

• EXPLAINME — architecture & invariants (developer deep-dive)

• ADR-0001 — content-engine direction

• Contributing · Governance

Where it fits

• poly-ssg — the family of language-native SSGs casket belongs to, unified via MCP.

• ddraig — the dependently-typed (Idris2) sibling; casket’s "proven twin" (casket validates, ddraig proves).

• boj-server — the estate’s verified MCP/capability server casket plugs into as a cartridge.

Requirements

• GHC 9.4+ (CI builds with 9.4.8), Cabal 3.0+ or Stack 2.0+

• Pandoc (current library dependency; see ADR-0001 for the planned move off it)

License

Code: MPL-2.0 (LICENSE). Prose documentation: CC-BY-SA-4.0.