typegen generates invalid TypeScript (empty `page` type) for pathless layout routes using remix-flat-routes

[iulspop]

Reproduction

Minimal reproduction repo: https://github.com/iulspop/react-router-typegen-bug-repro

Steps to reproduce:

git clone https://github.com/iulspop/react-router-typegen-bug-repro
cd react-router-typegen-bug-repro
pnpm install
pnpm typecheck

The typecheck fails with:

.react-router/types/+routes.ts(36,11): error TS1110: Type expected.

Route structure:

app/routes/
  _index.tsx
  _parent+/
    _parent-layout.tsx       # pathless layout — only has nested layout children
    _child-layout.tsx        # nested pathless layout
    _child-layout+/
      page-a.tsx             # /page-a
      page-b.tsx             # /page-b

routes.ts:

import { remixRoutesOptionAdapter } from "@react-router/remix-routes-option-adapter";
import { flatRoutes } from "remix-flat-routes";

export default remixRoutesOptionAdapter((defineRoutes) => {
  return flatRoutes("routes", defineRoutes);
});

Running react-router typegen produces invalid TypeScript for _parent-layout:

"routes/_parent+/_parent-layout.tsx": {
    id: "routes/_parent+/_parent-layout";
    page: ;  // <-- TS1110: Type expected
};

The bug occurs when a pathless layout route's children are all nested layouts (no direct leaf routes). Other pathless layouts with at least one direct leaf child generate correctly.

System Info

System:
  OS: macOS 26.2
  CPU: (14) arm64 Apple M4 Pro
  Memory: 5.09 GB / 48.00 GB
  Shell: 5.9 - /bin/zsh
Binaries:
  Node: 22.17.0 - /Users/iulspop/.nvm/versions/node/v22.17.0/bin/node
  npm: 10.9.2 - /Users/iulspop/.nvm/versions/node/v22.17.0/bin/npm
  pnpm: 10.28.2 - /Users/iulspop/.nvm/versions/node/v22.17.0/bin/pnpm
Browsers:
  Chrome: 144.0.7559.133
  Firefox: 147.0.2
  Safari: 26.2
npmPackages:
  @react-router/dev: 7.13.0 => 7.13.0
  @react-router/node: 7.13.0 => 7.13.0
  @react-router/remix-routes-option-adapter: 7.13.0 => 7.13.0
  @react-router/serve: 7.13.0 => 7.13.0
  react-router: 7.13.0 => 7.13.0
  vite: 7.3.1 => 7.3.1

Used Package Manager

pnpm

Expected Behavior

The page type for the pathless layout should be a union of all descendant pages:

page: "/page-a" | "/page-b";

Or never if no pages are directly reachable.

Actual Behavior

The typegen emits invalid TypeScript with an empty page type:

page: ;

This causes TS1110: Type expected and breaks tsc.

Workaround: Patch the output after typegen:

{
  "scripts": {
    "typegen:router": "react-router typegen && sed -i '' 's/page: ;/page: never;/g' .react-router/types/+routes.ts"
  }
}