virtualRouteConfig regression: pathless layout() with a dotted filename splits the dot into a new path segment

[paulgaspardo]

Which project does this relate to?

Router

Describe the bug

Starting in @tanstack/router-plugin (@tanstack/router-generator) 1.145.1, if you have a pathless layout() route defined in a virtualRouteConfig whose filename contains a dot (e.g. pathless.layout.tsx) the generator now interprets the dot in the filename as a path separator, so child routes are mounted under an unexpected path.

Given this config:

// src/routes.ts
export const routes = rootRoute('root.route.tsx', [
  index('index.route.tsx'),
  layout('pathless.layout.tsx', [
    route('subpath', 'subpath.route.tsx'),
  ]),
])

• 1.144.0 (working): subpath is reachable at /subpath.
• 1.145.1 and later (broken):subpath now resolves to /layout/subpath instead of /subpath.

Complete minimal reproducer

https://github.com/paulgaspardo/tsr-virtual-layout-dot-bug

Steps to Reproduce the Bug

1. git clone, npm install, npm run dev
2. Open http://localhost:5173/subpath
3. Open http://localhost:5173/layout/subpath

There are 3 commits/tags on the repository with working and non-working versions

1. First commit, working-1.144.0 - with the last version of @tanstack/router-plugin having the expected behavior in package.json
2. first-broken-1.145.1 - with the first version where broken behavior is observed
3. Last commit, still-broken-1.168.19 - with the current version of @tanstack/router-plugin, where it's still broken

Expected behavior

• When opening http://localhost:5173/subpath I expect to see the text "subpath.route.tsx"
• When opening http://localhost:5173/layout/subpath I expect to see a Not Found error

Screenshots or Videos

No response

Platform

• Router Version: 1.170.17
• OS: macOS
• Browser: Firefox
• Browser Version: 152.0.5
• Bundler: vite
• Bundler Version: 8.1.3

Additional context

Claude points to src/filesystem/virtual/getRouteNodes.ts, the case "layout": branch of
getRouteNodesRecursive as the source of the bug:

Between 1.144.0 and 1.145.1 the layout branch was rewritten to run the layout id through determineInitialRoutePath():

// 1.144.0 (correct)
const lastSegment = node.id;                         // e.g. "_pathless.layout"
const routePath = `${parentRoutePath}/${removeLeadingSlash(lastSegment)}`;
// => "/_pathless.layout"  (one segment, dot kept literal)

// 1.145.1+ (buggy)
const lastSegment = node.id;                         // "_pathless.layout"
const { routePath: escapedSegment, originalRoutePath: originalSegment } =
  determineInitialRoutePath(removeLeadingSlash(lastSegment));
const routePath = `${parentRoutePath}${escapedSegment}`;
// => "/_pathless/layout"  (two segments!)

determineInitialRoutePath (in src/utils.ts) splits on SPLIT_REGEX = /(?<!\[)\.(?!\])/g and re-joins parts with /. That regex exists to turn the physical file-based convention posts.index.tsx into nested path segments posts/index. But a virtual layout() id legitimately contains a dot as part of the name.layout naming convention, so the same split corrupts it.