I have encountered the same problem. The issue is you missing routeTree.gen.ts file under src/. Although it should be auto generated, according to the docs it does not happen in some instances. The steps to solving this issue are:

• Download the tanstack router cli:
  npm install --save-dev @tanstack/router-cli

• Create tsr.config.json in your project root, example:

  { "$schema": "https://cdn.jsdelivr.net/npm/@tanstack/router-cli/schema.json", "routesDirectory": "./src/routes", "generatedRouteTree": "./src/routeTree.gen.ts", "routeFileIgnorePattern": "\.(test|spec)\.[jt]sx?$" }

• Create a script in package.json and run it: "scripts": { "generate:routes": "tsr generate" }

This will create the required file according to your routes directory.