Container Query Migration Guide

Migrate viewport-based responsive logic (@media + useMedia) to container queries so components respond to their own available space instead of the raw viewport.

> Always do a visual check. After every migration, resize the _element_ (not just the window) and confirm the layout is identical and flips at the intended width. A good way to narrow an element without touching the window is to open a resizable panel next to it — e.g. drag out the Seer explorer sidebar, which squeezes the middle content. The token scales differ, so a mechanical swap that compiles can still render wrong.

Approach: refactor first, swap second

Stop at the first rung that fits. Prefer replacing hand-rolled CSS with primitives over a mechanical token swap.

| Rung | When | Do | | ---------------------- | ------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------- | | 1. Primitive props | The @media only flips layout (flex-direction, display, grid-template, gap, visibility, width) | Delete the styled component; use Container/Flex/Grid/Stack responsive props (direction={{xs: 'column', md: 'row'}}) | | 2. @container swap | CSS can't be a prop (descendant selectors, pseudo-elements, font-size, complex grid-template-areas) | Keep the styled component; swap @media → @container, theme.breakpoints.* → theme.container.* | | 3. Container-scoped JS | Width is read in JS to branch rendering | Replace useMedia(...) with useResponsivePropValue({...}) for a threshold boolean, or useContainerBreakpoint() to branch on the active key | | 4. Leave as useMedia | Genuine media feature, not width | Do nothing — these do not migrate |

⚠️ Convert to the nearest container scale

Breakpoint and container scales have different keys and different pixel values — this is not a rename. MAP BY PIXEL VALUE, NOT BY KEY: breakpoints.sm does NOT become container.sm. Reusing the same key is the #1 migration bug.

theme.breakpoints (viewport / @media), base 2xs:

| 2xs | xs | sm | md | lg | xl | 2xl | | ----- | ----- | ----- | ----- | ------ | ------ | ------ | | 0px | 500px | 800px | 992px | 1200px | 1440px | 2560px |

theme.container (container / @container), base zero:

| zero | 3xs | 2xs | xs | sm | md | lg | xl | 2xl | 3xl | 4xl | 5xl | | ------ | ----- | ----- | ----- | ----- | ----- | ----- | ----- | ----- | ------ | ------ | ------ | | 0px | 320px | 384px | 448px | 512px | 576px | 640px | 768px | 896px | 1024px | 1152px | 1280px |

Rule: take the old breakpoint's pixel value and pick the container token whose pixel value is _nearest_ to it — not the token with the same name. breakpoints.sm is 800px, so it maps to container.xl (768px), not container.sm (512px). Then confirm with a visual check: the container is often narrower than the viewport, so the nearest-px token is a starting point, not a guarantee.

Genuine viewport width → screen: keys, not useMedia

When layout truly must follow the _window_ (not the component's room), don't keep useMedia — use a screen:-prefixed responsive prop, which resolves against the viewport on the theme.breakpoints scale: direction={{zero: 'column', 'screen:lg': 'row'}}. Bare keys and screen: keys can mix on one prop. Prefer bare (container) keys; reach for screen: only when the viewport genuinely drives the layout.

Keep useMedia only for non-width media features

Width — container or viewport — has a prop/hook path above. Leave useMedia in place only for: prefers-color-scheme, prefers-reduced-motion, hover, pointer, max-height / height-based, resolution, print.

container-type: only when no query container is in scope

Default: don't add one. Bare keys and @container already resolve against the nearest ancestor container, and product views have one: ContentStack (#main, views/organizationLayout/index.tsx) wraps the routed <Outlet /> with containerType="inline-size"; topBar and #modal-portal cover their own subtrees. Add container-type only when a subtree must respond to _its own_ width rather than the page's — then:

• Use inline-size (width only). size also queries height, which collapses content unless height is set elsewhere.
• In a reusable component that may already sit inside a container, make it conditional to avoid a redundant one — containerType={hasParentQueryContainer ? 'normal' : 'inline-size'} via useHasContainerQuery() (see components/core/breadcrumbList/breadcrumbList.tsx).

Examples

Rung 1 — styled @media → primitive props (preferred)

tsx
// Old — delete the styled component
const Row = styled('div')`
  display: flex;
  flex-direction: row;
  gap: ${p => p.theme.space.md};
  @media (max-width: ${p => p.theme.breakpoints.sm}) {
    flex-direction: column;
  }
`;

// New
import {Flex} from '@sentry/scraps/layout';
<Flex direction={{xs: 'column', sm: 'row'}} gap="md">

Rung 2 — @media → @container (when it can't be a prop)

tsx
// Old
@media (max-width: ${p => p.theme.breakpoints.md}) { ... }

// New — swap at-rule AND scale; md breakpoint (992px) → nearest container token by px
// is 3xl (1024px), NOT theme.container.md by matching key
@container (max-width: ${p => p.theme.container['3xl']}) { ... }

Rung 3 — useMedia (width) → container-scoped JS

Both helpers below read the nearest query container (call from a descendant of one) and re-render as it crosses a breakpoint. A single max-width boolean is cleanest as a responsive value; reach for the active key only when you branch on the key itself.

tsx
// Old
const isNarrow = useMedia(`(max-width: ${theme.breakpoints.sm})`);

// New — resolve a responsive boolean against the container, same mobile-first
// cascade as CSS. A max-width query is "on by default, off past the threshold",
// so name only the threshold key. Map by pixel value: breakpoints.sm (800px) →
// nearest container token is xl (768px).
import {useResponsivePropValue} from '@sentry/scraps/layout';

const isNarrow = useResponsivePropValue({zero: true, xl: false});
// below xl → true, at/above xl → false — one key on each side, nothing to enumerate.

Reach for useContainerBreakpoint() instead only when you branch on the key itself (e.g. picking one of several layouts), not a single threshold. It returns the container's active key ('zero' … '5xl') — don't compare it with === 'zero' for a max-width case: that fires only below 320px and drops the 320–768px range the original query treated as narrow.

Migration Checklist

Took the lowest rung that fits (above). Then verify the gotchas:

• ] Mapped to the container token with the nearest pixel value, not the same name — e.g. breakpoints.sm → container.xl, not container.sm
• ] For width read in JS, used useResponsivePropValue({...}) for a threshold boolean; reserved useContainerBreakpoint() for branching on the key — never === 'zero' to mean "narrow" (that's only <320px)
• ] Routed genuine viewport-width cases to screen: keys; kept useMedia only for non-width media features
• ] Added container-type only when a subtree needs its own; used inline-size
• ] Confirmed a query-container ancestor exists (@container silently no-ops without one)
• ] Visual check: resized the element and confirmed identical output flipping at the intended width