Two TypeScript libraries: subkit for subscriptions and invoices, shopkit for your online shop. They run inside your app, with QR-bill, VAT and four languages. Payments go through zahls.ch with TWINT and card, and the data stays in your database.
No per-transaction fee · data in your database
import { createSubscriptions } from '@agentkit.ch/subkit'; const billing = createSubscriptions({ database: drizzleAdapter(db), provider: zahlsProvider({ instance: 'acme', }), plans: [basic, pro], tax: { rateBps: 810 }, });
POST /api/billing/webhook
waiting_
Basic
activeCHF 9.00 / month
Pro
CHF 19.00 / month
Invoices
2026-0142
15.10.2026 · TWINT
2026-0141
15.09.2026 · QR
billing_subscriptions
billing_invoices
select * from billing_invoices join teams on …
In use at
The kits
Each kit works on its own, and both share one adapter, one customer and one payment provider.
Subscriptions & invoices
For SaaS, memberships and club fees
Your customers pick a plan and pay by TWINT, card or QR-bill. subkit renews, prorates, sends reminders and matches payments with your bank.
Pro
CHF 19.00
/ month
Commerce
For club shops, SMEs, merch and gift cards
Products with variants, cart and checkout with TWINT or on invoice. shopkit reserves stock, works out shipping and VAT per product and sends the order confirmation.
Cart
New in shopkit 0.2 · Ordering through AI agents
Your shop becomes an MCP server. Your customers’ agent – Claude, ChatGPT or Cursor – finds products, prices the order with VAT and shipping, and places it. Payment goes through a zahls.ch link or straight to the saved TWINT. For every shopkit shop, no extra service.
import { createShopCustomerMcpHandler } from '@agentkit.ch/shopkit/mcp'Guide in the READMETwo bags of the house blend and a descaler, by post please.
search_productshouse blend, descaler
quote_order
2 × House blend 500 g37.00
Descaler12.90
PostPac Priority9.00
TotalCHF 58.90
Pay CHF 58.90 with your saved TWINT?
Yes, please.
place_orderexpectedAmount: 5890
New in shopkit 0.2 · For bakeries
For bakeries and confectioners on WaWiAssist: products come from WaWiAssist, and every order lands there as a WaWiAssist order – with the pickup day as the order date. Whether placed in the web shop or through an agent.
import { createHsSoftSync } from '@agentkit.ch/shopkit/hssoft'Guide in the READMEArticles → products
WaWiAssist
shopkit
Order → WaWiAssist
shopkit
#2187 · CHF 18.80
Pickup 31.10.2026
WaWiAssist
—
New in shopkit 0.4 · Swiss Post
One click in the order and the label with barcode is ready – with the order’s shipping method, billed to your franking licence. At checkout Swiss Post suggests postcode, locality, street and house number and checks the address before the order is placed.
import { createSwissPost } from '@agentkit.ch/shopkit/swisspost'Guide in the README<Checkout />
Street and number
Postcode and city
Address confirmed by Swiss Post
#1044
A6 · PRI
1.2 kg
Rösterei Aare
Aarstrasse 12
3011 Bern
Anna Muster
Bahnhofstrasse 12
8001 Zürich
99.60.123456.00000001
Don’t vibe-code it
A coding agent writes you a QR-bill and a TWINT checkout in an hour. The bugs only show up in production: payments booked twice, rounding differences, invoices the bank rejects. Let your agent wire in code that has already proven itself instead.
Vibe-coded billing6 ✗
Typical bugs that only show up in production.
With agentkit
Proven code.
Your coding agent doesn’t reinvent billing, it wires in a kit. The code comes from Membear, where it runs in production, and covers exactly these cases.
Add subscriptions with QR-bill and TWINT using @agentkit.ch/subkit. Read https://agentkit.ch/llms.txt first.
Features
What both kits bring: a coding agent that wires them in, webhooks that count only once, emails in four languages and ready-made screens.
llms.txt, typed options and errors with fixed codes. One prompt to a working checkout.
Idempotent webhooks and compare-and-set updates: if the same payment arrives twice, it is still booked only once.
When
A TWINT payment arrives
CHF 19.00 · 2026-0143
Then
Drop-in React components for the boring screens, plus a typed client. Headless hooks when you want your own.
The kits write to your database through adapters. JOIN them with your own tables – no sync, no silo.
Receipts, reminders and order confirmations as HTML and text, with your mailer.
Deine Quittung für Pro
Acme AG
Votre commande #1042 est confirmée
Boutique Léman
Promemoria: fattura 2026-0142
FC Lugano Nord
Swiss by default
Generic billing libraries think in Stripe, cents and one language. Swiss customers pay by QR-bill and TWINT, expect VAT on every invoice and read it in German, French or Italian. agentkit starts there.
Receipt
Account / Payable to
Reference
Payable by
Currency
Amount
Payment part
Currency
Amount
Account / Payable to
Reference
Additional information
Payable by
For developers
Mounted as a route in Next.js, Hono, SvelteKit, Remix or Express – on Node.js, Bun, Deno or at the edge. TypeScript, usable from JavaScript too.
Your coding agent reads llms.txt, detects your framework and database, writes the schema and sets up the route.
> Add subscriptions with subkit▍
Plans, payment provider and VAT in one file. No dashboard to keep in sync.
import { createSubscriptions } from '@agentkit.ch/subkit';
import { drizzleAdapter } from '@agentkit.ch/subkit/drizzle';
import { zahlsProvider } from '@agentkit.ch/subkit/zahls';
import { db, env } from './db';
export const billing = createSubscriptions({
// your Postgres, your tables
database: drizzleAdapter(db),
provider: zahlsProvider({ instance: 'acme', apiKey: env.ZAHLS_KEY }),
plans: [
{ id: 'free', name: 'Free', features: [], limits: {}, prices: {} },
{
id: 'pro',
name: 'Pro',
features: ['export'],
limits: {},
prices: { month: { amount: 1900, currency: 'CHF' } },
},
],
defaultPlanId: 'free',
tax: { rateBps: 810 }, // Swiss VAT 8.1 %
});MIT
Read it, change it, run it yourself.
Your database
Postgres through Drizzle – or your own adapter.
No backend of ours
Nothing phones home.
Whole Rappen
Money is never a floating-point number.
Why agentkit
For Membear, our club management software, we built QR-bills, TWINT via zahls.ch, VAT, bank reconciliation and invoices in four languages. The pitfalls were rarely in the code but in the details: reference numbers, rounding, deadlines, translations.
Then we noticed that every Swiss product rebuilds exactly that. Generic billing tools think in Stripe, cents and English – Switzerland comes, if at all, as a plugin.
So we are extracting the code from production and turning it into kits any TypeScript app can use. Free, and open source under MIT.
The siebenberge team
Open source
subkit and shopkit are on GitHub under the MIT licence, the packages are on npm. Read the code, change it and run it yourself – no per-transaction fee and no dependency on us.
MIT licence
Free for commercial use, including closed-source software.
No lock-in
The code runs in your app, the data lives in your database. A fork is all it takes to carry on without us.
Built in the open
Roadmap, issues and pull requests are public – contributions welcome.
Roadmap
Every kit comes from code that already runs in production and is pulled out once it has proven itself.
subkit + shopkit
on npm
subkit 0.2 and shopkit 0.4 as @agentkit.ch/subkit and @agentkit.ch/shopkit, the code under MIT on GitHub: QR-bill, bank reconciliation (camt.053 / camt.054), VAT, zahls.ch with TWINT, Drizzle adapter for Postgres. New in shopkit: ordering through AI agents (MCP), the HS-Soft (WaWiAssist) connection, the back office to embed and Swiss Post labels with address check.
core + CLI
next
A shared core with an adapter test suite, a CLI for schema and route, the docs in German too. In shopkit: Swiss Post live tariffs and refunds through zahls.ch.
Dunning & adapters
2027
1st, 2nd and 3rd reminder with fees and a reminder PDF with a new QR-bill. Prisma and Kysely adapters.
Questions
Still unsure? The demos show the kits with their real options.
subkit bills recurring payments: plans, subscriptions, trials and invoices – for SaaS, memberships or club fees. shopkit sells products: catalogue, cart, checkout, orders and gift cards. Both share customer data, the payment provider and the QR-bill.
No. Each kit works on its own. A club with membership fees and a fan shop takes both, a SaaS usually just subkit.
Yes, since shopkit 0.2. createShopCustomerMcpHandler turns your shop into an MCP server: the customer’s agent – Claude, ChatGPT or Cursor – finds products, prices the order with VAT and shipping, and places it. Payment goes through a zahls.ch link or the saved payment method, and only the confirmed amount is charged. Your sign-in decides who orders (OAuth or API key).
Yes. @agentkit.ch/shopkit/hssoft imports the articles from WaWiAssist as products and sends every order back as a WaWiAssist order, with the pickup day as the order date. All you need is the API key of your WaWiAssist from HS-Soft.
Yes, since shopkit 0.4. @agentkit.ch/shopkit/swisspost creates the label with barcode from the order – in the back office, through the API or MCP – and sends the customer the tracking number with Track & Trace. At checkout it suggests Swiss Post addresses and checks them. You need a franking licence and access to the Digital Commerce API of Swiss Post. Labels for items abroad and live tariffs are planned.
Yes. subkit and shopkit are on github.com/siebenberge/agentkit under the MIT licence, the packages are on npm. Issues and pull requests are welcome.
In your database. The kits run as a library inside your app and write to your tables through adapters. There is no agentkit backend and no additional data processor.
TWINT and credit cards through zahls.ch, plus invoices with the Swiss QR-bill. Other providers plug in through the PaymentProvider interface.
The kits are free. We take no per-transaction fee – you only pay your payment provider.
TypeScript, usable from JavaScript too. The kits mount as a route in Next.js, Hono, SvelteKit, Remix or Express and run on Node.js, Bun, Deno or at the edge. They write the data to Postgres through the Drizzle adapter; adapters for Prisma and Kysely are planned.
Yes: npm i @agentkit.ch/subkit or npm i @agentkit.ch/shopkit. subkit comes from code that runs in production; shopkit is in preview. Try them without installing: sub.agentkit.ch and shop.agentkit.ch.
Copy the setup prompt into your coding agent – or try the kits in the browser first.
Add subscriptions with QR-bill and TWINT using @agentkit.ch/subkit. Read https://agentkit.ch/llms.txt first.