[bug?] Shadow Endpoints fails to hydrate big data sent to their matching page because it is truncated. causing SyntaxError: Unexpected end of JSON input

Describe the bug

i originally came to this issue when trying to use shadow endpoints for the first time:

EDIT: there are more discovery points in subsequent comments below.

Reproduction

https://stackblitz.com/edit/sveltejs-kit-template-default-ahljwi?file=src/routes/about.svelte

npm run dev

and go to the /about endpoint

Logs

9:03:33 PM [vite] hmr update /src/routes/about.svelte

System Info

this is my mac envinfo since stackblitz doesnt seem to be able to run envinfo

  System:
    OS: macOS 11.4
    CPU: (8) x64 Apple M1
    Memory: 51.47 MB / 16.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.4.1 - /usr/local/bin/node
    Yarn: 1.22.10 - /usr/local/bin/yarn
    npm: 7.18.1 - /usr/local/bin/npm
  Browsers:
    Chrome: 98.0.4758.80
    Safari: 14.1.1
  npmPackages:
    @sveltejs/adapter-netlify: ^1.0.0-next.44 => 1.0.0-next.44 
    @sveltejs/kit: ^1.0.0-next.260 => 1.0.0-next.260 
    svelte: ^3.44.3 => 3.46.4 

Severity

blocking an upgrade

Additional Information

No response

[sw-yx]

WOW, amazing, thank you so much @PH4NTOMiki !

[PH4NTOMiki]

JSON.stringify makes a string but then JSON.parse fails to parse it, because because of those html elements in the string, the HTML becomes malformed and it breaks.