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onsystem
Keep coding agents on your design system
onsystem checks agent-written React against your real components and tokens: palette colors, native elements and APIs your design system lacks, at every edit and pull request, with the fix. MCP server, Claude Code plugin, ESLint plugin and GitHub Action. MIT.
Hi Product Hunt, I'm Diogo. I built onsystem because coding agents write UI from their training data, not from your design system: palette colors instead of your tokens, native elements instead of your components, and APIs your design system doesn't have.
onsystem reads your design system from source (components, props, variants, tokens) and gives it to the agent. In Claude Code, the plugin checks each file right after the agent edits it; Cursor, VS Code and Codex get it as an MCP server, and an ESLint plugin and a GitHub Action run the same check on every pull request.
Try it on your app, nothing installed: npx -y onsystem check .
I tested it in a 1,200-run benchmark across 6 models from 3 providers. Counted by onsystem 0.5.0's own check, design-system errors per run went from 0.85 without it to 0.00 with its skill, MCP server and hook, with no measurable change in tsc pass rate or cost. Scored by @shadcn/lint, a linter that is not part of onsystem, findings per run went from 4.97 to 2.64. Every run, the method and the caveats: https://onsystem.vercel.app/benc...
It's MIT licensed and the roadmap is public. If you try it on a real project, tell me where it breaks.
About onsystem on Product Hunt
“Keep coding agents on your design system”
onsystem was submitted on Product Hunt and earned 3 upvotes and 1 comments, placing #83 on the daily leaderboard. onsystem checks agent-written React against your real components and tokens: palette colors, native elements and APIs your design system lacks, at every edit and pull request, with the fix. MCP server, Claude Code plugin, ESLint plugin and GitHub Action. MIT.
On the analytics side, onsystem competes within Open Source, Developer Tools, Artificial Intelligence and GitHub — topics that collectively have 1.1M followers on Product Hunt. The dashboard above tracks how onsystem performed against the three products that launched closest to it on the same day.
Who hunted onsystem?
onsystem was hunted by Diogo Esteves. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
For a complete overview of onsystem including community comment highlights and product details, visit the product overview.
Diogo Esteves