Race condition: client side navigation vs SSR

Describe the bug

Quick navigation renders wrong page.

When browser navigating routes A -> B -> C, where A is a separate app, we render B, while address bar showsC.

Critical effect is this: User is served a page with broken interactive elements, if these elements are using [slug] params

Initial investigation

When quickly navigating back from a different site, the second navigation doesn't even trigger an http request, even before the scripts.

I was able to correct this effect locally by adding a location.href check into the rendered html

https://github.com/JakeBeaver/kit/blob/c1477090331570414d4104788347470fee18a2a4/packages/kit/src/runtime/server/page/render.js#L359

    blocks.push(`if (${event.url.href} !== location.href) location.refresh();`);

While this is most definitelly not the fix, it proves that browser navigation during first hydration(?) is ignored completely, but I do not know what interferes with the browser back button before client/start.js runs?

Reproduction

Project:

Create a skeleton project with the following, or clone this repo: https://github.com/JakeBeaver/sveltekit-quick-navigation-reproduction

Content:

1. /+page.svelte: empty
2. /load/+page.svelte: empty
3. /load/+page.server.js: load() that returns a promise
4. /layout.svelte: navbar, {$page.route.id}, slot
5. /slug/[slug]/+page.svelte: {$page.params.slug}

Steps:

Start on root route /

1. Use navbar to open /slug/1
2. Use address bar to navigate outside of the sveltekit app, like https://github.com/sveltejs/kit
3. Click the browser back button twice quickly

Result

/slug/[slug] gets rendered but $page.params.slug is missing

Logs

C:\repos\my-app> npm run dev                                                                         

> my-app@0.0.1 dev
> vite dev



  VITE v4.4.9  ready in 1311 ms

  ➜  Local:   http://localhost:5173/
  ➜  Network: use --host to expose
  ➜  press h to show help

System Info

System:
    OS: Windows 10 10.0.22000
    CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
    Memory: 12.55 GB / 31.74 GB
  Binaries:
    Node: 18.17.0 - C:\Program Files\nodejs\node.EXE
    npm: 9.6.7 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Spartan (44.22000.120.0), Chromium (115.0.1901.200)
    Internet Explorer: 11.0.22000.120
  npmPackages:
    @sveltejs/adapter-auto: ^2.0.0 => 2.1.0 
    @sveltejs/kit: ^1.20.4 => 1.22.4 
    svelte: ^4.0.5 => 4.1.2 
    vite: ^4.4.2 => 4.4.9

Severity

blocking an upgrade

Additional Information

No response

Reproduce the quick back-button navigation with the linked skeleton project, then inspect packages/kit/src/runtime/server/page/render.js and the client/start.js entry point. Verify how navigation from an external site is handled before hydration. Done means the rendered route matches the address bar and [slug] params remain available for interactive elements.