What is Flowbun?

Flowbun is a flow-based home automation runtime: a small flow-based programming-style engine where blocks are pure(-ish) async TypeScript functions, wiring is plain JSON on disk, effects live strictly at the boundary, and the visual editor is optional sugar over the same plaintext files a human or an IDE can edit directly.

Why it exists

Node-RED gets a lot right: flows are mostly pure(-ish) data transformations wired together, and its Home Assistant integration is good. But it has real problems:

Effects and pure functions aren’t segregated.
The palette is full of programming primitives (“switch”, “change”) that are better expressed as code.
Flows live in an opaque JSON blob that fights version control and IDEs.
Reusing logic across flows is awkward.

Digital Alchemy proves the alternative — typed TypeScript against your actual Home Assistant instance — is a genuinely nice experience, but it has no visual layer.

Flowbun is the synthesis:

Blocks are just TypeScript. Named, typed inputs and outputs on a plain async function. If you need a switch statement, you write a switch statement.
Wires are type-checked before anything runs. Every flow compiles through a generated assertion file with real tsc. A wire carrying the wrong shape fails the reload, and the old flow keeps running.
Effects live at the boundary. Only @hass/* blocks can touch Home Assistant, and each flow runs in its own process.
Plaintext is the source of truth. Wiring is diffable JSON; blocks are ordinary .ts files; every write from any tool is auto-committed to a dedicated git history.

Status

Flowbun is a working proof-of-concept, running real automations against a real Home Assistant instance — including a live grid-zero battery export controller and a sun-tracking blind controller. See the GitHub repository for the full architecture writeup and phase-by-phase history.