Plain CSS, plain JSX transpiled in the page, plain HTML. No bundler, no package install, no build. Drop the folder into a project and the tokens, components, specimen cards and eight working prototypes are already there.
They are not the same thing. The archive is a copy that will never change under you. The repository is the living project. The markdown is the reasoning on its own, for reading or for handing to an agent.
01Getting started →Every document and nothing else: no CSS, no components, no bundle. What a person reads, and what a model is given.
readme.md — the design guide itselfAGENTS.md and SKILL.md.prompt.md pairs, one per familyLICENSE, NOTICE and the changelogThe project as it actually stands. Clone it for the history, or to change something and keep your changes separate from mine.
NOTICEA dated snapshot with everything in it, including the generated bundle — so it renders the moment it lands.
AGENTS-notes data models inside themThe first needs no configuration at all. The rest are one line, one paste, or one path.
02Provenance and limits →Create a design-system project, drop the unzipped contents at its root, and open it. The compiler finds styles.css, the 54 components, the 78 cards and the 8 templates on its own. There is nothing to configure and nothing to run first.
SKILL.md already carries its front matter and AGENTS.md explains how to assemble a screen. Drop the folder into a skills directory and it loads as a skill — the rules arrive before the first component does.
The markdown package is the whole system without the machinery, so it travels anywhere a model reads context. Paste the design guide and the .prompt.md pairs into v0, Lovable, Bolt, Cursor or your own harness. No install, no runtime, no assumption about the stack it will produce.
Every templates/<slug>/ is self-contained but for one line: ds-base.js holds the path back to the system root. Repoint that string and the prototype renders anywhere. Read the matching notes file first — it documents the fixtures and the data model.
None of this is buried, because none of it should be. Read it before you ship something built on it.
03Back to the top →Reckon’s component set recreates the visual language behind coss.com and its component library, built from the open-source cosscom/coss monorepo. The upstream project is open source and its assets travel with this package, credited in NOTICE.
Worth naming in full: cosscom/coss, coss.com/ui, Base UI, Lucide and Tailwind v4.
The recreation work — tokens, component CSS, specimen cards, templates and the design guide — is AGPL-3.0-or-later, matching the upstream default it derives from. The token layer comes from a source with no MIT-licensed equivalent, so anything narrower would be a claim the provenance does not support.
Designing an interface with it is use, not derivation, and a product built with Reckon is not automatically AGPL. Copying the token files, the component implementations or the rules into your own distributed project is derivation, and §13 means network use counts. LICENSE and NOTICE travel with the source.
styles.css from a different depth, and both faces fail to the system stack.Reckon
Components are the easy part. What you are missing is the layer that decides what gets computed, what gets shown, and what gets refused.