router-plugin: split chunk and shared module miss shared bindings when compiled before the route file #8754

Which project does this relate to?

Router

Describe the bug

The code splitter moves a module-level binding that a split option and a kept option both read into the ?tsr-shared=1 module. The split chunk (?tsr-split=…) and the shared module look those bindings up in sharedBindingsMap, and only compiling the route file fills that map. When a chunk or the shared module compiles before the route file in a process, the map is empty:

• the chunk declares the binding again, so the chunk and the route file each hold their own copy of the state;
• the shared-module transform returns null, so ?tsr-shared=1 is the untouched route file: it calls createFileRoute a second time and does not export the binding, while the compiled route file imports the binding from it.

This happens when the route file's output comes from a cache. A dev server that keeps transform results across restarts serves the route file without running the plugin on it, then compiles a chunk it has not cached yet, such as an errorComponent chunk nobody asked for before. It also happens in any tool that compiles modules one at a time.

Complete minimal reproducer

https://gist.github.com/shkumbinhasani/1787ba7900314a3384e3d8dbc4334674

Steps to Reproduce the Bug

1. Clone the gist, run npm install, then npm start.

2. The script starts a Vite dev server with tanstackRouter({ target: 'react', autoCodeSplitting: true }) and calls server.transformRequest on this route's three modules in two orders, each on a fresh server:

   const visits = { count: 0 }
   
   export const Route = createFileRoute('/')({
     loader: () => ++visits.count,
     component: () => 'visits: ' + visits.count,
   })

3. Order A (route file, chunk, shared module) is right. Order B (chunk, shared module, route file) prints a chunk with its own const visits = { count: 0 } and a shared module that still calls createFileRoute and exports Route instead of visits.

Expected behavior

The order does not matter. In both orders the ?tsr-split=component chunk imports visits from ?tsr-shared=1, and the shared module declares and exports only visits.

Screenshots or Videos

No response

Platform

• Router / Start Version: @tanstack/router-plugin 1.168.47; also on main (b1b1117)
• OS: macOS
• Browser: n/a (build time)
• Browser Version: n/a
• Bundler: vite
• Bundler Version: 8.3.4

Additional context

#8504 computes the shared bindings from the source in the split and shared handlers (resolveSharedBindings), which fixes this as part of the Yuku migration. I'll open a small fix for the current plugin.

AI disclosure: Claude Code wrote this report and the reproducer, and ran the reproducer against 1.168.47.