sunpeak

sunpeak's strongest idea is that MCP Apps have a runtime problem: your UI only exists inside ChatGPT's and Claude's iframes with host-specific themes, display modes, and CSS variables, so a normal browser test proves very little. sunpeak solves that by replicating both host runtimes locally in an inspector, which is what makes the rest of the framework useful — Playwright fixtures handle inspector startup, MCP connection, iframe traversal, and host switching, so assertions look like `inspector.renderTool('show-albums', {}, { theme: 'dark' })` followed by a locator check on a rendered button. Layered above that are visual regression screenshots across hosts and themes, live tests against real ChatGPT sessions, and multi-model evals for tool-calling quality. Four levels of testing, all runnable in GitHub Actions without paid host accounts or AI credits, is the actual differentiator — nobody wants to pay for a ChatGPT account just to run CI. The framework half is deliberately Next.js-shaped: tools, resources, and simulations auto-discovered from the filesystem, one resource reusable by several tools (`review-diff.ts`, `review-post.ts`), backend-only tools with no UI, and a `server.ts` for auth and server config. The 20+ typed hooks (useToolData, useAppState, useTheme, useDisplayMode) are the practical payoff: you write the app logic once and let sunpeak adapt to whichever host is rendering it, rather than branching on platform in every component. What it is not: a hosted product. There is no SLA, no managed runtime, no dashboard — you run `sunpeak dev`, `sunpeak build`, `sunpeak start` yourself, and the docs walk through deployment and hosting rather than doing it for you. It is also React-only; if your frontend is Vue or Svelte, the UI-component and hooks half of sunpeak is unavailable and only the standalone testing framework applies. The documentation set leans heavily on Claude Connectors right now — OAuth, CIMD, DCR, token refresh, debugging failed connections and tool selection — which is a fair signal that connector auth is where the real build friction sits. If you are a solo developer prototyping a tool with no UI, a plain MCP server library is less machinery. If you are shipping an interactive app to both hosts and want regression coverage, sunpeak replaces a surprising amount of manual host-switching, tunneling, and refreshing.