Design systems are infrastructure, not artifacts.
A design system isn't a deck. It isn't a Figma library. It isn't a Notion page nobody reads. Those are artifacts — snapshots of a moment that drift the second the next sprint ships.
Infrastructure is different. Infrastructure runs. It carries load. When something downstream breaks, you fix the infrastructure, not the downstream symptom. The right design system is infrastructure too — the layer between intent and shipped product that every page, every component, and every contributor passes through.
Tostada starts from that premise. The system you shape here doesn't sit next to the codebase; it is the input to the codebase. Edit a token, every component restyles. Update a rule, every export reflects it. There is no “design system” file rotting in a folder somewhere — the design system is whatever the export currently says.
The system you shape should be the system that ships.
Most teams have a design system. Or three. The Figma library says one thing. The CSS variables file says another. The Notion doc says a third. Six months in, they agree on almost nothing, and the question “what does the brand say about this button?” has no clean answer.
The single-source-of-truth thesis is simple: there should be exactly one place to define what the system is, and everything downstream should derive from it. Not a sync. Not a mirror. The same artifact.
Tostada's bundle — tokens.css, design-system.md, design-system.json — is that artifact. The Markdown your AI consumes is the same Markdown your engineers read on Monday morning is the same Markdown the Figma plugin imports tokens from. One file. One truth. Update it, replace it, ship the diff.
Read by humans. Read by code. Read by AI.
A design system used to have one reader: the front-end developer who'd implement it. The grammar was set by what they needed — color names, spacing scales, component anatomy.
That grammar still serves humans. It now has to serve two other audiences with very different reading habits. Compiled code reads CSS variables — every consumer needs tokens.css it can import without translation. AI coding agents read prose — they want imperative voice, Do / Don't tables, per-variant guidance, and explicit relationships between tokens, components, and rules.
Tostada writes for all three. The Markdown is structured so an agent can pattern-match it as easily as a developer can skim it. The CSS is the canonical token format every framework already speaks. The JSON is for tooling that wants to introspect. One source of truth, three voices, no copy-paste between them.
Built in the open, or it doesn't count.
A design system tool you can't see inside is a tool that gets abandoned. If you can't read the code, can't fork the repo, can't see what the export looks like before you commit to it, then you're just betting on a vendor's roadmap matching yours.
Tostada is Apache 2.0-licensed and built in the open. The codebase is on GitHub. Issues, pull requests, and design discussions all happen in public. The roadmap gets shaped in the Slack — by the people using the product today, not a closed customer council two quarters from now.
This isn't a marketing claim. It's a constraint we set on ourselves: every interesting decision happens where the community can see it, push back on it, or propose something better. We're not the design system. You are. We just built the tools to write yours down.
Free for everyone, sustainable for the long run.
Open source and sustainable aren't in tension — they're the same bet. The core of Tostada is, and stays, open source: free to read, fork, run, and ship with, by anyone. That's the tool everyone gets, and the part that has to outlive any company building it.
For now, all our energy goes into the core. Down the road, a paid license key will unlock advanced features for organizations that need to scale beyond one library on one machine: spreading a design system across a whole directory or monorepo, history and rollback, role-based access control, and managing many libraries at once. A free core for everyone, a paid tier for the teams that need the scale — the second funds the first, so the open tool never has to be abandoned.
