Open source · AGPL-3.0 · no account, no backend, no telemetry
Lionsville Architect is an open-source modelling tool for the whole picture: the application landscape in Layer-7 bands, the C4 container diagrams under it, the business architecture beside it, and the decisions and observations written where the architecture is. Everything is saved as text files in a folder you choose — nothing hides inside the app.
What it does
Two levels of diagram, the business and technology views around them, and the record of why — in one place, with one undo stack over all of it.
Five bands — actors, input channels, external systems, the application landscape, the management layer — with elements placed in them and domain groups boxing the ones that belong together. Bands and groups resize; a group has its own colour and can be tidied on its own.
Double-click an application to open the container view under it, or to create one. The application becomes the boundary of that view and its components sit inside; every landscape keeps the list of container views beneath it, and you step back up from any of them.
Stakeholders down the side, the journey your work takes as a band of phases over lanes, the responsibility areas with their capabilities and how each one is covered — and the band of what nobody has claimed yet.
Platforms, the services they realise, and which applications are hosted on them or use them, drawn as a landscape of their own. What hosting implies is derived, never written a second time, so one fact is written once.
Lines are routed orthogonally by a real router — libavoid on WebAssembly, off the main thread — around elements rather than through them. When automatic is not what you want, drag a segment, pin a route, choose the side each end attaches to; it all survives a re-layout and a reload.
Every landscape, application and group keeps its own architecture decision records: MADR markdown with a title, a status, a date and the people it was put to. Proposed, reviewing, accepted, rejected, superseded — and the end states lock the record.
A register of what the team saw — where, how often, how much it matters — analysed into causes and causes of causes until a root cause stands at the end. The analysis is drawn, with the weight of each line saying how firmly one explains the other.
Connect Claude Desktop, Claude Code or any MCP client and it reads the landscape, draws, decides and navigates through the same commands you use — with a banner on screen saying who is working, and a Stop button that is yours.
⌘K searches element names, the prose written about them and the decisions taken around them, and opens the thing each hit is about. Every change — a drag, a rename, an accepted decision — comes back in the order you made it.
Seen from more than one side
Where your work is kept
On the desktop, in a folder you choose, as text files you can read. A moved element rewrites one small file, a rewritten paragraph one markdown file, and git diff says what changed in words you recognise. The folder syncs, backs up and commits like anything else you own.
With git on the machine, Snapshot… records the folder under a message drafted from what you actually did, and History… shows what has changed since any snapshot — as architecture, not as lines.
.lvarch) — the same folder in one zip, for handing to someone who will edit it.<your folder>/<group>/<project>/
project.json · model.json
diagrams/<id>.json · <id>.placements.json
docs/<element>.md
decisions/NNNN-<slug>.md
observations/NNNN-<slug>.md
observations/causes/NNNN-<slug>.md
logos/<key>.svgRun it
app.architecture.lionsville.nl runs the newest stable release. In Chrome and Edge it opens a folder on your own disk; in other browsers your projects live in the browser’s storage and the working file is what you keep. Nothing is sent anywhere.
Signed installers for macOS, Windows and Linux on the release page. The desktop app tells you when a newer version exists and hands you the installer; it never installs anything behind your back.
Node 20 or newer, an internet connection once for the install, and everything after that is local.
git clone https://github.com/Lionsville/Lionsville-Architecture-Management-Tool.git
cd Lionsville-Architecture-Management-Tool
npm run setup && npm run devOpen the app, copy Acme Logistics in, and take it apart. The manual — in English, Dutch, Frisian and German — is the place to start reading.