Getting Started

Install the CLI, write one file, and watch it run in a browser. Nothing else is required — no clone, no bundler config, no project scaffold.

Install

npm i -g kumiki
# or, without installing
npx kumiki --help

Node.js 24 or newer, which is what the packages declare.

No install at all

The Playground runs the compiler and the runtime inside your browser. Pick an example, edit on the left, watch it render on the right.

Write an app

Save this as app.kumiki:

slot count : Int = 0

reducer inc on=ui.click(IncBtn) do= count := count + 1

tile IncBtn = button(text="+1", onClick=inc)
tile App    = column(heading("Count: " + count.show), IncBtn)

app Counter
    caps   = []
    routes = {"/" -> App, "/404" -> App}
    init   = []

Four declarations: slot is the state, reducer turns an event into a state change, tile projects state to UI, and app names the entry point. Your First App builds the same file line by line, and Thinking in Kumiki covers the remaining three layers.

Run it

kumiki dev app.kumiki
# → kumiki dev — http://localhost:5173/

Open that URL and click +1. The dev server rebuilds on save and shows compile errors in an overlay.

When you want a static bundle instead:

kumiki build app.kumiki ./out
# → Wrote out/index.html, app.js, runtime/ (core, stdlib, tiles-layout, tiles-text, tiles-input)

out/index.html opens straight from disk. runtime/ carries only the modules this app touches, so the counter ships about 9KB gzipped; an app that never routes or renders a table ships no router and no table code.

Verify it

check reads the file without running it:

kumiki check app.kumiki
# → ok

smoke mounts the app in a headless DOM and clicks through it, which catches the app that compiles and then renders nothing:

kumiki smoke app.kumiki
# → ok — mounted, rendered, 1 interaction(s), no runtime errors

Both are worth running before you ship. kumiki with no arguments lists the rest of the commands.

When check fails

Every diagnostic carries a code and a position:

E0103 undef-ref at 3:39: Reference to undefined name "total"

The code names the category. Look it up in the error catalog — E0103 there tells you the name resolves to nothing, which is a typo or a missing definition nine times out of ten. kumiki fix app.kumiki E0103 proposes a patch for the codes that have one.

Next

• Your First App — the counter, one layer at a time
• Recipes — reverse lookup from "I want to do X" to a working example
• Examples — one file per feature, plus complete apps

Working from a clone

Clone the repository when you want the examples, the benchmarks, or the compiler source. The workspace exposes the same CLI as pnpm kumiki, run from the repository root:

git clone https://github.com/kumikijs/Kumiki.git
cd Kumiki
pnpm install
pnpm kumiki check packages/examples/apps/01-counter/app.kumiki

Driving Kumiki from an AI agent

@kumikijs/mcp exposes check, build, per-definition editing, and spec search as MCP tools. See its README for a client configuration.