accounted/.agents/skills/vercel-react-view-transitions/references/implementation.md

Implementation Workflow

Follow these steps in order when adding view transitions to an app. Each step builds on the previous one.

Step 1: Audit the App

Before writing any code, scan the codebase thoroughly. Search for:

• Every <Link> and router.push — these are your navigation triggers. Open every file that contains one.
• Every <Suspense> boundary — each one is a candidate for a reveal animation. Check what its fallback renders.
• Every page/route component — list them all. Each page needs a VT placement decision.
• Persistent elements — headers, navbars, sidebars, sticky controls that stay on screen across navigations. These need viewTransitionName isolation.
• Shared visual elements — images, cards, or avatars that appear on both a source and target view (e.g., a thumbnail in a list and the same image on a detail page).
• Skeleton-to-content control pairs — if a Suspense fallback renders a control (search input, tab bar) that also exists in the real content, both need a matching viewTransitionName.

Then classify every navigation and produce a navigation map:

| Route           | Navigates to         | Direction    | VT pattern            |
|-----------------|----------------------|--------------|-----------------------|
| /               | /detail/[id]         | forward      | directional slide     |
| /detail/[id]    | /                    | back         | directional slide     |
| /detail/[id]    | /detail/[other]      | sequential   | directional slide (ordered prev/next) or key+share crossfade |
| /tab/[a]        | /tab/[b]             | lateral      | key+share crossfade   |
| (Suspense)      | (content loads)      | —            | slide-up reveal       |

For each shared element (name prop), note every navigation where a pair forms and where it doesn't — this determines whether you need enter/exit as a fallback alongside share.

Step 2: Add CSS Recipes

Copy the complete CSS recipe set from css-recipes.md into your global stylesheet. This includes timing variables, shared keyframes, fade, slide (vertical), directional navigation (forward/back), shared element morph, persistent element isolation, and reduced motion.

Do not write your own animation CSS — the recipes handle staggered timing, motion blur on morphs, and reduced motion that are easy to get wrong. You can customize timing variables (--duration-exit, --duration-enter, --duration-move) after the initial setup.

Step 3: Isolate Persistent Elements

For every persistent element identified in Step 1, add a viewTransitionName style to pull it out of the page content's transition snapshot:

<header style={{ viewTransitionName: "site-header" }}>...</header>

Then add the persistent element isolation CSS from css-recipes.md (prevents the element from animating during page transitions). If the element uses backdrop-blur or backdrop-filter, use the backdrop-blur workaround from css-recipes.md instead.

If a Suspense fallback mirrors a persistent control (e.g., a skeleton search input), give both the real control and the skeleton the same viewTransitionName so they morph in place.

Step 4: Add Directional Page Transitions

For hierarchical navigations identified in Step 1, tag the navigation direction using addTransitionType inside startTransition:

startTransition(() => {
  addTransitionType('nav-forward');
  router.push('/detail/1');
});

Then wrap each page component (not layout) in a type-keyed <ViewTransition>:

<ViewTransition
  enter={{
    "nav-forward": "nav-forward",
    "nav-back": "nav-back",
    default: "none",
  }}
  exit={{
    "nav-forward": "nav-forward",
    "nav-back": "nav-back",
    default: "none",
  }}
  default="none"
>
  <div>...page content...</div>
</ViewTransition>

The nav-forward and nav-back CSS classes from css-recipes.md produce horizontal slides. For simpler apps where directional motion isn't needed, a bare <ViewTransition default="none"> wrapper with enter="fade-in" / exit="fade-out" works too.

Extract this into a reusable component so every page doesn't repeat the verbose type map:

export function DirectionalTransition({ children }: { children: React.ReactNode }) {
  return (
    <ViewTransition
      enter={{ 'nav-forward': 'nav-forward', 'nav-back': 'nav-back', default: 'none' }}
      exit={{ 'nav-forward': 'nav-forward', 'nav-back': 'nav-back', default: 'none' }}
      default="none"
    >
      {children}
    </ViewTransition>
  );
}

This also becomes the single place to adjust if you add new transition types later.

Rules:

• Always pair enter with exit — without an exit animation, the old page disappears instantly while the new one animates in.
• Always include default: "none" in type map objects and default="none" on the component — otherwise it fires on every transition.
• Place the directional <ViewTransition> in each page component, not in a layout. Layouts persist across navigations and never trigger enter/exit.
• Only use directional slides for hierarchical navigation or ordered sequences (prev/next). Lateral/sibling navigation (tab-to-tab) should use a bare <ViewTransition> (cross-fade) or default="none".

Step 5: Add Suspense Reveals

For every <Suspense> boundary identified in Step 1, wrap the fallback and content in separate <ViewTransition>s:

<Suspense
  fallback={
    <ViewTransition exit="slide-down">
      <Skeleton />
    </ViewTransition>
  }
>
  <ViewTransition enter="slide-up" default="none">
    <AsyncContent />
  </ViewTransition>
</Suspense>

This example uses slide-down / slide-up for directional vertical motion. For a simpler reveal, a bare <ViewTransition> around the <Suspense> gives a cross-fade with zero configuration. Choose based on the spatial meaning — consult the "Choosing the Right Animation Style" table in the main skill file.

Rules:

• Always use default="none" on the content <ViewTransition> to prevent re-animation on revalidation or unrelated transitions.
• Use simple string props (not type maps) on Suspense <ViewTransition>s — Suspense resolves fire as separate transitions with no type, so type-keyed props won't match.

Step 6: Add Shared Element Transitions

For every shared visual element identified in Step 1, add matching named <ViewTransition> wrappers on both the source and target views:

// On the source view (e.g., list/grid page)
<ViewTransition name={`photo-${photo.id}`} share="morph" default="none">
  <Image src={photo.src} ... />
</ViewTransition>

// On the target view (e.g., detail page) — same name
<ViewTransition name={`photo-${photo.id}`} share="morph">
  <Image src={photo.src} ... />
</ViewTransition>

The share="morph" class uses the morph recipe from css-recipes.md (controlled duration + motion blur). For a simpler cross-fade, use share="auto" (browser default).

When list items contain shared elements, compose both patterns with two nested <ViewTransition> layers — see "Composing Shared Elements with List Identity" in SKILL.md.

Rules:

• Names must be globally unique — use prefixes like photo-${id}.
• Add default="none" on list-side shared elements to prevent per-item cross-fades on filter/search updates.

Step 7: Verify Each Navigation Path

Walk through every row in the navigation map from Step 1 and confirm:

• Does the VT mount/unmount on this navigation, or does it stay mounted (same-route)?
• For named VTs: does a shared pair form? If not, does enter/exit provide a fallback?
• Does default="none" block an animation you actually want?
• Do persistent elements stay static (not sliding with page content)?
• Do Suspense reveals animate independently from directional navigations?

If any path produces no animation or competing animations, revisit the relevant step.

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Common Mistakes

• Bare <ViewTransition> without props — without default="none", it fires the browser's default cross-fade on every transition (every navigation, every Suspense resolve, every revalidation). Always set default="none" and explicitly enable only the triggers you want.
• Directional <ViewTransition> in a layout — layouts persist across navigations and never unmount/remount. enter/exit props won't fire on route changes. Place the outer type-keyed <ViewTransition> in each page component.
• Fade-out exit with shared element morphs — the page dissolving conflicts with the morph. Use a directional slide exit instead.
• Writing custom animation CSS — the recipes in css-recipes.md handle staggered timing, motion blur on morphs, and reduced motion. Copy them; don't reinvent them.
• Missing default: "none" in type-keyed objects — TypeScript requires a default key, and without it the fallback is "auto" which fires on every transition.
• Type maps on Suspense reveals — Suspense resolves fire as separate transitions with no type. Type-keyed props won't match — use simple string props instead.
• Raw viewTransitionName CSS to trigger animations — React only calls document.startViewTransition when <ViewTransition> components are in the tree. A bare viewTransitionName style is for isolating elements from a parent's snapshot, not for triggering animations.
• update trigger for same-route navigations — nested VTs inside the content steal the mutation from the parent, so update never fires on the outer VT. Use key + name + share instead.
• Named VT in a reusable component — if a component with a named VT is rendered in both a modal/popover and a page, both mount simultaneously and break the morph. Make the name conditional or move it to the specific consumer.
• router.back() for back navigation — router.back() triggers synchronous popstate, incompatible with view transitions. Use router.push() with an explicit URL.

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For Next.js-specific implementation steps (config flag, transitionTypes on <Link>, same-route dynamic segments), see nextjs.md.