Infinite redirect loop ("ERR_TOO_MANY_REDIRECTS") caused by encoded unsafe character ^ (%5e) in URL pathname

[markafox]

Which project does this relate to?

Router

Describe the bug

This is the same issue as bug #7587 but happens with the ^ character. I have tried every other special character available on a standard US QWERTY keyboard and after the bug fix for 7587 this only still happens with the ^ character.

When a URL pathname contains encoded the unsafe character ^ (%5e) an infinite redirect loop is started and the browser crashes with an ERR_TOO_MANY_REDIRECTS error.

This happens in both basic paths and paths with parameters.

Unfortunately we use the ^ as a delimiter in a single route parameter.

Complete minimal reproducer

Any blank project initialized with @tanstack/cli is sufficient for reproducing the issue—no additional code is needed

Steps to Reproduce the Bug

1. Create a TanStack Start project from scratch. You don't need to add anything; just start the dev server and proceed to step 2
2. Open http://localhost:3000/^

Expected behavior

Should throw a 404 error if it is not part of a valid path or be passed as part of the path parameter if it is in a path parameter.

Screenshots or Videos

Platform

• Router / Start Version: Router v1.170.25 / React-Start v1.168.42
• OS: Windows 11 - Ubuntu WSL2
• Browser: Edge (chrominium)
• Browser Version: v151.0.4129.72
• Bundler: Vite
• Bundler Version: v8.2.1

Additional context

No response