Breaking change caused by "fix: fullpath handling" PR

[supermacro]

Which project does this relate to?

Router

Describe the bug

#6404 led to a large amount of type errors in our codebase since a trailing / was added to our routes.

Further, we now have a weird UX where the keys of FileRoutesByFullPath are different than the keys of FileRoutesByTo:

Given this distinction, we end up with weird calls to navigate and related apis like the one below

Your Example Website or App

https://not-allowed-to-share.com

Steps to Reproduce the Bug or Issue

Generate the route tree prior to b42f84a, ensuring you have one or more index.tsx route files.

Note that they won't have a trailing /

Now generate again but with b42f84a

Note that now those routes have a trailing /

Expected behavior

No breaking change

Screenshots or Videos

No response

Platform

• Router / Start Version: 1.159.5
• OS: macos
• Bundler: vite
• Bundler Version: 7.3.1

Additional context

No response

[schiller-manuel]

please provide a complete minimal reproducer project.

[supermacro]

@schiller-manuel https://github.com/supermacro/tanstack-fullpath-breaking-change-repro

[schiller-manuel]

the types are correct. the route id of an index route must have the trailing slash to differentiate it against layout routes

[supermacro]

the types are correct

Doesn't that prove my point?

The types are correct relative to b42f84a, but userland code prior to b42f84a breaks after adding this update

[schiller-manuel]

type fixes are not considered breaking changes.

[supermacro]

lol, feels like you're not really trying to help here. Did you look at the repro repo or run the commands in that repo?

[supermacro]

Am I misunderstanding something here? How is it ok to update to a new version of tanstack router and suddenly have our project not compile?

cc @tannerlinsley

[tannerlinsley]

I’m sorry this isn’t optimal, but this how we run type versioning at TanStack. We always recommend locking to specific patch versions if you can’t afford CI failures due to type fixes/enhancements.

For posterity:

• Bug fixes can be “breaking” for apps that utilize the buggy interface
• layout routes and index route IDs must be different to distinguish them. What you’re experiencing is the fix for things to be more strict and correct so they are not conflated
• If we treated type fixes as breaking changes, we’d be at 300.x.x by now

[supermacro]

I appreciate the context!