Svelte 5.27.1 - Cannot access <snippet> before initialization on page refresh

[catalin-l]

Describe the bug

I've been using Svelte for the past few months, so I'm not sure if this is caused by bad practice, or an actual issue. It was not present in 5.27.0, so it looks like an issue.

I'm basically using context to store Snippets so I can hot swap parts of the layout based on the page. This worked fine until today when I updated from 5.27.0 to 5.27.1.

It looks to be working fine if the content is static (just regular HTML, text) , but it breaks once a $state variable is used in the Snippet.

Reproduction

1. Load app
2. Click "Test" anchor
3. Refresh page

Repo: https://github.com/catalin-l/svelte-slot-test

Logs

ReferenceError: Cannot access 'sidebar' before initialization
    at _page (/home/catalin/Development/bugs/svelte-slot-test-main/src/routes/test/+page.svelte:4:13)
    at eval (/home/catalin/Development/bugs/svelte-slot-test-main/.svelte-kit/generated/root.svelte:66:5)
    at _layout (/home/catalin/Development/bugs/svelte-slot-test-main/src/routes/+layout.svelte:14:11)
    at Root (/home/catalin/Development/bugs/svelte-slot-test-main/.svelte-kit/generated/root.svelte:61:3)
    at render (/home/catalin/Development/bugs/svelte-slot-test-main/node_modules/.pnpm/[email protected]/node_modules/svelte/src/internal/server/index.js:88:2)
    at Function._render [as render] (/home/catalin/Development/bugs/svelte-slot-test-main/node_modules/.pnpm/[email protected]/node_modules/svelte/src/legacy/legacy-server.js:27:24)
    at render_response (/home/catalin/Development/bugs/svelte-slot-test-main/node_modules/.pnpm/@[email protected]_@[email protected][email protected][email protected][email protected]_l_uydtfn24dfo5ird66jvbjiwfrm/node_modules/@sveltejs/kit/src/runtime/server/page/render.js:192:29)
    at async render_page (/home/catalin/Development/bugs/svelte-slot-test-main/node_modules/.pnpm/@[email protected]_@[email protected][email protected][email protected][email protected]_l_uydtfn24dfo5ird66jvbjiwfrm/node_modules/@sveltejs/kit/src/runtime/server/page/index.js:299:10)
    at async resolve (/home/catalin/Development/bugs/svelte-slot-test-main/node_modules/.pnpm/@[email protected]_@[email protected][email protected][email protected][email protected]_l_uydtfn24dfo5ird66jvbjiwfrm/node_modules/@sveltejs/kit/src/runtime/server/respond.js:499:18)
    at async respond (/home/catalin/Development/bugs/svelte-slot-test-main/node_modules/.pnpm/@[email protected]_@[email protected][email protected][email protected][email protected]_l_uydtfn24dfo5ird66jvbjiwfrm/node_modules/@sveltejs/kit/src/runtime/server/respond.js:363:20)

System Info

System:
  OS: Linux 6.14 Fedora Linux 42 (Workstation Edition)
  CPU: (16) x64 AMD Ryzen 7 7745HX with Radeon Graphics
  Memory: 4.46 GB / 14.80 GB
  Container: Yes
  Shell: 5.2.37 - /bin/bash
Binaries:
  Node: 22.12.0 - ~/.volta/tools/image/node/22.12.0/bin/node
  npm: 10.9.0 - ~/.volta/tools/image/node/22.12.0/bin/npm
  pnpm: 9.15.0 - ~/.volta/bin/pnpm
Browsers:
  Brave Browser: 135.1.77.97
npmPackages:
  svelte: ^5.27.1 => 5.27.1 

This also has been tested on my work Macbook Pro M4 and the behaviour is the same.

Severity

blocking an upgrade