Personal · 2026
A local-first, open-source visual editor for social graphics, carousels and video scenes, built so people and AI agents can edit the same structured design. Extracted from the editor I built inside Sociona.
read how it was built ↓Design editors people know are hosted, account-based and closed, with AI added on the side. I wanted a capable canvas that works without an account or a backend, and whose document is something an agent can understand and safely change. It started as a feature of Sociona and I pulled the reusable core out so others could use it, embed it and extend it.
Pages and elements live in a typed, versioned document validated with Zod. Fabric.js draws and manipulates it, but it is a replaceable renderer, never the source of truth.
Moving, styling, grouping and deleting are validated commands with undo. A person and an agent use the same door, so agent edits land in the same history.
Storage, assets, the assistant, version history and publishing come in through a StudioHost boundary. The canvas does not know if it runs locally, in a hosted product or in a desktop shell.
Projects and fonts live in IndexedDB, video is encoded locally and background removal runs in a worker, so the standard editor needs no server and no key.
Agentic features extend direct manipulation instead of replacing it. The editor has to be good with no agent attached.
Most design editors are hosted products: you sign in, your work lives on their servers, and any AI feature is bolted on to a format built for people. They are not made to be embedded or to be driven safely by someone else's agent.
Stencil starts from different assumptions:
Everything outside the canvas moved behind StudioHost interfaces, and the packages were made to build and bundle standalone, so the editor runs with nothing but a browser.
The product owns a versioned document. Fabric objects are built from it, and Fabric's interaction events are turned back into commands.
They run in Web Workers and with the browser's media APIs, and the decoder is released when a slide goes inactive.
Slides are parked when they are off screen and mounted progressively, so only the visible ones cost anything.
I kept a written list of what had not been seen in a browser, and clicking through it came first. Rendering parity tests are the next piece of work.
Stencil is released as an early open-source project with a free hosted demo. These numbers describe what was built. There are no usage figures yet.
Started as the editor inside Sociona, then extracted and open-sourced as its own product.
No sign-up for the free demo. The source is on GitHub under the MIT licence.
Event networking with games instead of icebreakers. Attendees join with a code or QR, then play bingo, scratch cards, social deck and pair matching that get them talking, while organizers run check-in, announcements, surveys and analytics. A web dashboard and an Expo guest app on a Convex backend.
Want something like Stencil?
Tell me what you're making and I'll tell you how I'd build it.