run402: the full stack where the customer is the agent
When we launched kysigned, we said the backend it runs on deserved a post of its own. Here it is.
An agent can build a working app faster than you can read this post. Then it hits a wall. It needs a backend, a database, auth, storage, somewhere to host the thing, and it can't set any of that up itself. So it stops and turns to the human: go sign up, configure it, paste me the keys. The building was the easy part. The plumbing is where a human gets pulled back in, every time.
We hit that wall on every app we built, kysigned included. And autonomy was only half of it. We needed a specific set of features, and the freedom to add whatever the next app turns out to need. We wanted it open source, so anyone could run the whole stack, not just us. Good backends exist, but we couldn't find one we liked, so we built one: run402.
The customer is the agent, not a person
The whole thing turns on how run402 gets paid. There is no signup. When an agent needs a backend, it pays for it directly, per call, over the same HTTP request. The agent can hold its own wallet on the open payment rails from Coinbase and Stripe, x402 and MPP, or spend credits a person loads with a regular credit card, as an allowance. Either way the agent covers its own infrastructure and hands back a live URL. Nobody pastes a key.
What's underneath
A real full stack: the Postgres, auth, and storage you would expect, plus static hosting and serverless functions. The agent surfaces ship as a TypeScript SDK, a JSON-first CLI, and an MCP server. The entire app, database and functions and frontend and secrets, ships in one atomic deploy, live all at once. Every lease is prepaid and hard-capped, so an agent can never run up a surprise bill. Errors come back as structured data an agent can act on, not English it has to guess at.
A few things we needed and couldn't find anywhere else are built in. Storage for the agent's own wallet and keys, so it can hold and spend money safely. Scheduled jobs. Raw inbound email with the headers left intact, which is the entire reason kysigned can verify a DKIM signature.
Open source, with a hosted version
The whole platform is open source, with a hosted version for less hassle. Same code, same features, no lock-in. The agent surfaces (SDK, CLI, MCP server) are MIT at github.com/kychee-com/run402; the full backend is Apache-2.0 at github.com/kychee-com/run402-core. Run it yourself, or let us run it for you.
Try it
Open a coding agent and paste: "Please build me a demo app using run402.com/llms-cli.txt". It provisions a backend, pays for it, and hands back a working link. The prototype tier is free. That is the factory, live at run402.com, open on GitHub. More apps soon.
Kychee builds AI-native voice products and Open SaaS. Write to info@kychee.com.