Render `+error.svelte` whenever possible

[theetrain]

Describe the bug

From the docs: https://svelte.dev/docs/kit/routing#error

+error.svelte is not used when an error occurs inside handle or a +server.js request handler.

Not sure if this is a bug or feature request, but I'm thinking +error.svelte should be rendered whenever possible, and not only when performing client-side navigation. The current behaviour is inconsistent (see reproduction below).

Reproduction

https://www.sveltelab.dev/g4cglz64hfgy3vm

1. Load REPL, observe 500 error rendered by error.html
2. Navigate to /test manually in the preview pane
3. Click on 'home' link
4. Observer /src/routes/+error.svelte being rendered instead of error.html

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (4) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.20.3 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @sveltejs/adapter-auto: ^3.0.0 => 3.3.1 
    @sveltejs/kit: ^2.5.27 => 2.20.2 
    @sveltejs/vite-plugin-svelte: ^5.0.0 => 5.0.3 
    svelte: ^5 => 5.25.3 
    vite: ^6.0.0 => 6.2.3

Severity

annoyance

Additional Information

I could not find duplicate issues, and I'm not sure if this is a bug or feature request. If implemented, it would certainly be a breaking change and a potential candidate for SvelteKit 3.

Here's a somewhat related problem presented on Discord: Documentation/help for custom error page for top-level hooks.server.ts error in which someone is attempting to use reroute to maintain the URL while capturing and throwing errors in handle.