[uhyo]

Summary

Follow-up to #270: step 2 of its refactoring plan (deduplication), plus shared prop types. No change in behavior or public exports.

Step 1 of the plan (moving interception out of NavigationAPIAdapter) was tried and dropped. The interceptor still had to share the adapter's state, so the coupling stayed: an instanceof check plus six internal methods on the adapter. All of that saved about 1.3 KB in a RouteDisplay-only bundle.

Shared rendering core (Router/RouteTree.tsx)

The new internal RouteTree component holds what was duplicated between Router and RouteDisplay:

• resolving feature flags and the browser() check
• the SSR URL from ssr.path
• deciding whether loaders run
• loader cache keying (the entry key, or a per-instance cache when there is no entry)
• route matching and running loaders
• the RouterContext value and the providers around RouteRenderer

After this:

• Router = createAdapter(fallback) + useLocationEntry + adapter.setupInterception + RouteTree
• RouteDisplay = createDisplayAdapter() + useLocationEntry + RouteTree

Shared prop types (Router/props.ts)

• RouteTreeSharedProps defines routes, ssr, trailingSlash and features once, each with a single doc comment. SSRConfig and RouterFeatures moved to the same file; Router/index.tsx re-exports them, so the public exports are unchanged.
• RouterProps, RouteDisplayProps and RouteTreeProps are interfaces that extend it, with no intersection types.
• Router passes the shared props it doesn't use itself straight to RouteTree (...sharedProps), and RouteDisplay passes all its props. A new shared prop can't be forgotten in one of them.

Changes users can see in types and docs:

• Doc comments: routes gets a doc comment. The ssr comment now says "the real URL of the page takes over" so it fits both components.
• Interfaces instead of type aliases: RouterProps and RouteDisplayProps are now interfaces. Unlike the old aliases, they can't be assigned to an index-signature type such as Record<string, unknown>.
• Internal name in .d.ts: the published types show RouterProps extends RouteTreeSharedProps. The base interface is emitted but not exported.

Docs

• The <RouteDisplay> section of the Components API page now says it assumes nothing else on the page intercepts navigations. If something else does, entry changes still render, but loaders don't re-run on an intercepted reload and the navigation info isn't exposed.
• The Component Rendering section of CLAUDE.md now describes RouteTree.

Bundle size

Minified with esbuild against dist/, React excluded: about 12.4 KB for an entry importing only RouteDisplay and 13.0 KB for one importing only Router. Both are about 200 B larger than on master because of the extra component.

Test plan

• pnpm test:run: 371 tests pass, with no test changes
• pnpm typecheck, pnpm lint, pnpm format:check, pnpm --filter @funstack/router build
• Docs site build: not run locally, because the container has Node 22, which has no global URLPattern. CI uses Node 24.

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