DT-3507-fix-code-block-scrolling

[andrewzamojc]

Description & motivation 💭

When our code block component has a lot of content and a max-height, it gets a vertical scroll bar. This scroll area doesn't allow scrolling to pass through, which ends up feeling weird in a lot of cases. Furthermore, since some of our pages have little extra scroll heights, sometimes users feel they can't scroll at all.

This PR removes the scrollBehavior: contain from the code block CSS, to allow scrolling to pass through when at the top or bottom of the code block.

Screenshots (if applicable) 📸

Design Considerations 🎨

Testing 🧪

How was this tested 👻

• Manual testing
• E2E tests added
• Unit tests added

Steps for others to test: 🚶🏽‍♂️🚶🏽‍♀️

Go to holocene preview, code block component, scrolling story. Notice the scroll passes through once you're at the top or bottom of the code.

Checklists

Draft Checklist

Merge Checklist

Issue(s) closed

Docs

Any docs updates needed?

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Project	Deployment	Actions	Updated (UTC)
holocene	Ready	Preview, Comment	Feb 2, 2026 8:32pm

[temporal-cicd]

Warnings

⚠️

📊 Strict Mode: 14 errors in 2 files (1.2% of 1121 total) src/lib/vendor/codemirror/custom-extensions.ts (4) L61:48: Parameter 'header' implicitly has an 'any' type. L65:6: Type '{ borderWidth?: undefined; borderColor?: undefined; color: string; backgroundColor: string; height: string; } | { borderWidth: string; borderColor: string; color: string; backgroundColor: string; height: string; }' is not assignable to type 'StyleSpec'. L84:6: Type '{ borderWidth?: undefined; borderColor?: undefined; color: string; backgroundColor: string; height: string; } | { borderWidth: string; borderColor: string; color: string; backgroundColor: string; height: string; }' is not assignable to type 'StyleSpec'. L150:2: Property 'text' does not exist on type '{ json: LanguageSupport; java: LanguageSupport; go: LanguageSupport; php: LanguageSupport; python: StreamLanguage; shell: StreamLanguage<...>; dotnet: StreamLanguage<...>; ruby: StreamLanguage<...>; typescript: StreamLanguage<...>; }'. src/lib/holocene/code-block.stories.svelte (10) L84:44: Argument of type 'null' is not assignable to parameter of type '((key: string, value: { hello: string; }) => { hello: string; }) | undefined'. L112:36: Argument of type 'null' is not assignable to parameter of type '((key: string, value: Record<string, unknown>) => Record<string, unknown>) | undefined'. L133:53: Argument of type 'null' is not assignable to parameter of type '((key: string, value: { hello: string; }) => { hello: string; }) | undefined'. L149:53: Argument of type 'null' is not assignable to parameter of type '((key: string, value: { hello: string; }) => { hello: string; }) | undefined'. L157:53: Argument of type 'null' is not assignable to parameter of type '((key: string, value: { hello: string; }) => { hello: string; }) | undefined'. L167:53: Argument of type 'null' is not assignable to parameter of type '((key: string, value: { hello: string; }) => { hello: string; }) | undefined'. L177:6: Argument of type 'null' is not assignable to parameter of type '((key: string, value: TypedPropertyDescriptor[] & { [x: string]: PropertyDescriptor; }) => TypedPropertyDescriptor[] & { ...; }) | undefined'. L189:6: Argument of type 'null' is not assignable to parameter of type '((key: string, value: TypedPropertyDescriptor[] & { [x: string]: PropertyDescriptor; }) => TypedPropertyDescriptor[] & { ...; }) | undefined'. L344:8: Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{ 'File A': string; 'File B': string; }'. L345:8: Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{ 'File A': string; 'File B': string; }'.

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