Saync — The contract layer for software

Modern React shops have three layers of tests — unit, snapshot, end-to-end — and none of them catch the bugs that actually ship. Unit tests assert function correctness, not user behavior. Snapshots catch DOM diffs, not behavioral drift. End-to-end tests live in a separate folder, drift from the code they verify, and become flaky enough that teams skip them. The thing every developer knows about a component — which API it should call, how fast, what the response should look like — usually lives only in their head. Saync's wager: make that knowledge a declaration on the component itself, then verify it for free. Wrap a component with the Saync SDK — <SayncButton>, <SayncForm>, <SayncInput> and 35 other wrapped primitives. Add an expects={...} prop saying what should happen. One install, one command. A Playwright-driven agent boots your dev server, clicks every button, fills every form, listens to the actual network calls, and reports any drift in a local Sentry-style dashboard at localhost:3777. Everything — the SQLite database, the agent, the dashboard — lives inside your repo. No SaaS. No signup. No telemetry. Saync also supports multi-step flows declared in saync.flows.ts (login, checkout, onboarding), and a production reporter that surfaces real-user contract violations alongside your dev runs. The product ships as four packages on npm: saync-web (the dashboard, CLI, and standalone server), @saync/core (types, registry, defineFlow), @saync/react (the wrapped components), and @saync/agent (the Playwright runner).