@lovable.dev/vite-tanstack-config

Vite config wrapper for Lovable TanStack Start projects.

What It Does

• Gives TanStack Start projects a single defineConfig helper for local preview and production builds.
• Keeps Lovable sandbox previews predictable by setting the server shape, watched paths, HMR coordination, and asset routing expected by the platform.
• Adds diagnostics that help the preview tell build, Vite, SSR, and app errors apart.
• Produces deployable build output for Lovable while still letting self-hosted projects choose their own target.

Customization

Apps can pass through Vite options and adjust the React, TanStack Start, Nitro, HMR gate, and error-logging behavior when they need to.

Build exit watchdog

Inside a Lovable build with prerender enabled, the build process is forced to exit if it is still alive 60 seconds after the last build hook has returned, and a [lovable-build-exit-report] block naming the open handle types is written to stderr. Adjust it with defineConfig({ buildExitWatchdog: { graceMs, enabled } }); the grace is clamped to 5 s–10 min. The LOVABLE_PRERENDER_EXIT_GRACE_MS and LOVABLE_PRERENDER_EXIT_WATCHDOG=off environment variables override the config.

Route manifest

Inside a Lovable build, the route surface of the app is written to dist/.lovable/routes.json after the build: { version, generator, basepath?, serverEntry, requestMiddleware?, urlInspection, routes }, where routes is the generated route tree's fullPaths union in TanStack path syntax (/posts/$postId, /files/$, /docs/{-$version}). Lovable's serving layer uses it to answer requests no route can match without starting the app. The file is enumerated with @tanstack/router-generator through an in-memory overlay, so the build never rewrites routeTree.gen.ts, and it is skipped — with a warning naming the reason — whenever the app can answer paths outside its route tree: tanstackStart.spa, router.virtualRouteConfig, nitro.routeRules/handlers, a project nitro.config.* / .config/nitro.* / .nitrorc file (Nitro loads it on its own, so the wrapper cannot see what it adds), a rewrite in the router file, a basepath there that tanstackStart.router.basepath does not declare (a computed or shorthand one included), or a router file (router.entry, resolved the way TanStack Start resolves it) that cannot be read to check either.

urlInspection tells the serving layer whether the code that runs ahead of route matching could answer a request from its URL; only none lets it enforce the manifest, every other value keeps it advisory. The wrapper reads the server entry (server.entry, or src/server.ts by convention — the same rule sets serverEntry) and the start entry (start.entry or src/start.ts, whose requestMiddleware runs before the router) together with every module they import through relative or @/ paths, with comments and string contents removed, and reports server_entry, request_middleware or both when any of it names the URL, one of its parts (pathname, searchParams, path), a redirect (redirect, Location, a 30x status) or a not-found answer (404, notFound). It reports unknown instead of guessing when a module cannot be resolved or read, when a module is loaded by a computed specifier or import.meta.glob, when the closure imports a package other than node:*/@tanstack/* (a mounted framework can route without naming the URL), or when it outgrows 32 files / 256 KiB. The template's server.ts and start.ts read as none; keep them free of those names, or new projects stop asserting it.