Code highlighting no longer works

[theogravity]

Describe the bug

I'm using vitepress@1.6.4 and haven't updated it in a few months and noticed recently that the code highlighting no longer works. It seems to work on initial render but then loses the highlighting immediately after.

The documentation site for 2.x for this also has broken behavior as well. I wonder if there's some issue with Shiki itself:

https://vitepress.dev/guide/markdown#syntax-highlighting-in-code-blocks

Reproduction

Visit https://vitepress.dev/guide/markdown#syntax-highlighting-in-code-blocks as an example.

I've replicated this in Edge, Chrome, Mobile Safari on both MacOS / iOS / Windows.

Expected behavior

Code should have highlighting.

System Info

System:
    OS: macOS 15.5
    CPU: (12) arm64 Apple M2 Max
    Memory: 88.16 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.16.0 - /Users/theo/.nvm/versions/node/v22.16.0/bin/node
    Yarn: 1.22.22 - /Users/theo/.nvm/versions/node/v22.16.0/bin/yarn
    npm: 10.9.2 - /Users/theo/.nvm/versions/node/v22.16.0/bin/npm
    pnpm: 10.20.0 - /Users/theo/Library/pnpm/pnpm
    bun: 1.1.27 - /Users/theo/.bun/bin/bun
    Deno: 2.2.8 - /Users/theo/.deno/bin/deno
    Watchman: 2025.04.28.00 - /opt/homebrew/bin/watchman
  Browsers:
    Brave Browser: 140.1.82.172
    Chrome: 143.0.7499.110
    Firefox: 137.0.1
    Safari: 18.5
  npmPackages:
    vitepress: 1.6.4 => 1.6.4

Additional context

No response

Validations

• Check if you're on the latest VitePress version.
• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.

[brc-dd]

I've replicated this in Edge, Chrome, Mobile Safari on both MacOS / iOS / Windows.

Hmm, I'm not able to reproduce this in any of the browsers on macOS/iOS. Can you share details like specific browsers + OS versions where this occurs? And also check with extensions/theme disabled. The generated code is basically color + css variables, I don't see why that will break across browsers.

[theogravity]

Thanks for the comment regarding extensions. It's the 1Password extension that was causing this.

I use it on mobile and across platforms. Guess something about it is intercepting or injecting something that causes highlights to not work.