Reference Error: Cannot access 'component' before initialization

[bigmac44]

Describe the bug

Been getting this error when traversing to a new page with the latest (2.50.2) release. Does not happen on 2.50.1 or earlier.

These may be red herrings: but I've only seen it happen (although pretty reliably) with Safari 26 (after a cache clear) and when navigating to a larger / more complex page. Only happens the first time visiting the page and doesn't seem to happen when you hover long enough over the link to preload everything. Since this looks to be some kind of race condition, it may be effecting other browsers but the race is just more difficult to produce.

Reproduction

I'll try to produce a smaller example.

Logs

From the safari console:
Unhandled Promise Rejection: ReferenceError: Cannot access 'component' before initialization. client.is:663

Stacktrace:
[Error]
ReferenceError: Cannot access 'component' before initialization.
(anonymous function) — client.js:663
map
get_navigation_result_from_branch — client.js:663


Unhandled Promise Rejection: ReferenceError: Cannot access 'component' before initialization. client.js:2572

Stacktrace:
[Error] Unhandled Promise Rejection: ReferenceError: Cannot access 'component' before initialization.
	(anonymous function) (client.js:2572)

System Info

System:
    OS: macOS 15.7.3
    CPU: (10) arm64 Apple M4
    Memory: 192.55 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.12.0 - /Users/eriktribou/.nvm/versions/node/v22.12.0/bin/node
    npm: 10.9.0 - /Users/eriktribou/.nvm/versions/node/v22.12.0/bin/npm
  Browsers:
    Chrome: 144.0.7559.133
    Firefox: 120.0.1
    Safari: 26.2
  npmPackages:
    @sveltejs/adapter-cloudflare: ^7.0.0 => 7.2.6 
    @sveltejs/kit: 2.50.2 => 2.50.2 
    @sveltejs/vite-plugin-svelte: ^6.0.0 => 6.2.4 
    svelte: ^5.45.0 => 5.50.0 
    vite: ^7.0.4 => 7.3.1

Severity

blocking an upgrade

Additional Information

Offending line of the stack trace appears to be:
constructors: compact(branch).map((branch_node) => branch_node.node.component),

[elliott-with-the-longest-name-on-github]

Really tough to do anything with this one without a repro, hoping you can find one so we can dig in!