client-urls

Use clientUrls() inside a "use client" module and default-export the result. Define routes with path(), layout(), and loader() helpers using named function components, then mount the module in the server tree with include().

A revalidate() predicate inside a loader() use callback runs in the browser with client-computable args like currentParams, nextParams, and isAction. Only its decision crosses the wire, so make predicates param-sensitive to avoid serving stale data on param navigations.

clientUrls() defines client-component routes with no handlers, where all data reads use useLoader at consumption sites. urls() defines server routes with handlers that can await ctx.use() in the pipeline. Use clientUrls() for fast-transition UIs and urls() for full-feature server routing.

No. include, parallel, cache, middleware, errorBoundary, and notFoundBoundary throw inside clientUrls() by design. Place middleware and boundaries at or around the include() mount in the server urls() tree instead.

Flag a loader with ssr:false when its output must exist in the SSR'd document, such as head meta via handle pushes or a deterministic 404 status. Document renders then await that loader before first flush, while sibling loaders keep streaming.

Common causes are anonymous or inline components instead of named function values, duplicate route patterns or names, a layout() with no path() inside, or a "use server" directive in a loader body. Everything in the definition must be JSON-projectable.