Frontend Builder

Use Vite+'s vp CLI with React and TypeScript as the standard frontend stack. Use TanStack Router for routing.

Core Rules

• For new projects, create a React + TypeScript project with Vite+ (vp).
• When migrating an existing Vite project to Vite+, use vp migrate.
• Use pnpm as the package manager.
• Use playwright-cli when browser verification is useful.
• After every code change, run vp check --fix.
• Prefer Vite+ lifecycle commands whenever possible: vp dev, vp build, vp test, vp lint, vp fmt, and vp check.
• Respect existing Vite+ configuration in vite.config.ts, including lint/fmt/test/run/pack/staged blocks.
• When using Vite+, do not create separate config files for Oxlint, Oxfmt, Vitest, or tsdown. Consolidate tool configuration in vite.config.ts.
• Make the first viewport show the actual usable app. Do not start with an explanatory landing page unless the user explicitly asks for one.
• Always write dev server stdout/stderr to web.log in the project root.

New Project

1. Create the project with vp.

vp create vite -- --template react-ts

1. Install dependencies.

pnpm install @tanstack/react-router @tanstack/router-devtools lucide-react

1. If the project has no existing CSS convention, keep styling in src/index.css and component CSS. Do not add extra UI frameworks unless they materially help the task.

Vite+ Configuration

In Vite+, consolidate all tool configuration in vite.config.ts.

import { defineConfig } from "vite-plus";

export default defineConfig({
  server: {},
  build: {},
  preview: {},
  test: {},
  lint: {},
  fmt: {},
  run: {},
  pack: {},
  staged: {},
});

Enable lint.options.typeAware and lint.options.typeCheck because type-aware linting is desired.

export default defineConfig({
  lint: {
    ignorePatterns: ["dist/**"],
    options: {
      typeAware: true,
      typeCheck: true,
    },
  },
  fmt: {
    singleQuote: true,
  },
});

Existing Vite Migration

For an existing Vite project, inspect the current state first, then migrate to Vite+.

vp migrate

After migration, review changes to vite.config.ts, package scripts, and the lockfile. If the project already has tests, linting, formatting, or build workflows, run vp check or the individual vp build, vp test, and vp lint commands.

Vite+ Commands

• vp dev: Start the Vite dev server with HMR.
• vp build: Run the production build through Rolldown. This runs the Vite build, not a custom package.json build script.
• vp preview: Serve the production build locally.
• vp test: Run Vitest once. Unlike standalone Vitest, this is not watch mode.
• vp test watch: Run tests in watch mode.
• vp test run --coverage: Run tests with coverage.
• vp lint: Run Oxlint.
• vp fmt: Run Oxfmt.
• vp check: Run format, lint, and typecheck in one pass.
• vp check --fix: Auto-fix formatting and lint issues.
• vp run build: Run the package.json build script.
• vp run build -r: Run the script across all workspace packages in dependency order.
• vp pack: Build a library through the tsdown integration.

TanStack Router Priority Rules

Implement these rules by priority.

• Critical: register the router type, use the from parameter for type narrowing, type the root context, and use queryOptions for loader type inference.
• Critical: organize the route tree around hierarchy, layouts, index routes, and pathless layouts.
• High: configure router defaults, loaders, loaderDeps, TanStack Query integration, search param validation, and not-found/error handling.
• Medium: use Link, active states, useNavigate, relative paths, code splitting, and preloading when they fit the task.
• Low: use root context, beforeLoad, and dependency injection when shared dependencies such as auth, API clients, or feature flags are needed.

Router Implementation

Create src/router.tsx and define a path-based route tree with createRootRouteWithContext, createRoute, and createRouter.

import {
  Link,
  Outlet,
  createRootRouteWithContext,
  createRoute,
  createRouter,
} from "@tanstack/react-router";
import { TanStackRouterDevtools } from "@tanstack/router-devtools";

type RouterContext = {
  queryClient?: unknown;
};

function RootLayout() {
  return (
    <>
      <nav>
        <Link to="/" activeOptions={{ exact: true }}>
          Home
        </Link>
        <Link to="/settings">Settings</Link>
      </nav>
      <Outlet />
      <TanStackRouterDevtools />
    </>
  );
}

const rootRoute = createRootRouteWithContext<RouterContext>()({
  component: RootLayout,
  notFoundComponent: NotFoundPage,
  errorComponent: ErrorPage,
});

const indexRoute = createRoute({
  getParentRoute: () => rootRoute,
  path: "/",
  component: HomePage,
});

const settingsRoute = createRoute({
  getParentRoute: () => rootRoute,
  path: "/settings",
  validateSearch: (search) => ({
    tab: typeof search.tab === "string" ? search.tab : "profile",
  }),
  component: SettingsPage,
});

const routeTree = rootRoute.addChildren([indexRoute, settingsRoute]);

export const router = createRouter({
  routeTree,
  defaultPreload: "intent",
  defaultPreloadStaleTime: 30_000,
  scrollRestoration: true,
  context: {},
});

declare module "@tanstack/react-router" {
  interface Register {
    router: typeof router;
  }
}

Use RouterProvider in src/main.tsx.

import { StrictMode } from "react";
import { createRoot } from "react-dom/client";
import { RouterProvider } from "@tanstack/react-router";
import { router } from "./router";
import "./index.css";

createRoot(document.getElementById("root")!).render(
  <StrictMode>
    <RouterProvider router={router} />
  </StrictMode>,
);

Data Loading

• Prefer route loader functions for route data instead of component-level useEffect.
• Define loaderDeps when search params or route params affect the loader cache.
• When using TanStack Query, combine queryOptions with queryClient.ensureQueryData.
• Wait for critical data in the loader, and split non-critical data into deferred loading or component-side fetching.
• Handle loader errors with errorComponent and not-found states with notFoundComponent.
• Route loaders for parent and child routes run in parallel, so avoid unnecessary sequential dependencies.

Search Params

• Always validate search params with validateSearch and treat them as typed URL state.
• Provide defaults so the page does not break when the URL omits a search param.
• Design parent routes so child routes can inherit parent search param types when useful.
• Put only shared, restorable, or bookmarkable state in the URL.
• Configure a custom serializer only when complex search param values require one.

Navigation

• Use Link for normal page navigation.
• Configure active states for current-location UI.
• Use useNavigate for programmatic navigation after form submits or command actions.
• When using relative paths, make the source route explicit.
• Consider route masks only when modal URLs or preserved background pages are required.

Code Splitting And Preloading

• Split large routes, settings pages, admin screens, game screens, and other non-critical initial routes into lazy routes.
• Keep critical route definitions, loaders, validateSearch, and error boundaries in the main route file.
• Enable auto code splitting when the environment supports it.
• Use defaultPreload: "intent" for primary navigation.
• Use manual preloading only for screens that are highly likely to be opened next.

UI Implementation

• Split page components by route. Even for small apps, avoid putting everything in src/App.tsx; create src/pages/ and src/components/.
• Implement primary, empty, error, and loading states when they are relevant.
• Use lucide-react for icon buttons when an icon is needed.
• Prevent text from overflowing buttons or cards by using stable dimensions, wrapping, and responsive constraints.
• For apps that need visual content, such as games or image-heavy experiences, use real assets, searched images, generated images, Canvas, Three.js, or another appropriate visual approach. Do not rely on empty decoration.

Logs And Dev Server

Start the dev server from the project root and write logs to root-level web.log.

vp dev --host 0.0.0.0 > web.log 2>&1

After startup, inspect web.log for the served URL, compile errors, and runtime errors. Fix issues and restart when needed.

Common Errors

• vp build does not run the expected script: vp build is for the Vite build. Use vp run build to run the package.json script.
• Imports are broken after vp migrate: run vp install, then vp check to find remaining issues.

Verification

• Run vp build and fix type errors and build errors.
• Depending on the change, run vp test, vp lint, vp fmt, and vp check.
• Start the dev server and confirm Vite+ startup logs are written to web.log.
• Directly visit each TanStack Router path and verify initial render, search params, not-found behavior, and navigation.
• In the final response, briefly report changed files, the dev server URL, verification performed, and anything not verified.