Design handoff

Design Handoff

Translating a design into code is more than eyeballing the picture. Static frames hide states, breakpoints, semantics, and the token system underneath. Hardcoded hex values and one-off components look right on day one and drift off-brand by day thirty.

Extract the system behind the design, reuse what the product already has, implement every state the mockup doesn't show, and prove fidelity in the browser — not just in DevTools overlay.

Pairs with [[ui-craft]] for states and polish, [[accessibility]] for semantics, focus, and contrast the visual file won't specify, [[browser-checks]] to verify the running UI, [[incremental-delivery]] to ship slice by slice, and [[react-patterns]] when the handoff is React/Next.js. For gaps in the design, clarify before coding ([[spec-first]]) — don't guess missing behavior.

When to Use

• Implementing a mockup, Figma frame, Sketch file, or visual spec as components/pages
• Matching spacing, typography, color, and layout to an approved design
• Building a new component that should plug into an existing design system
• Reviewing whether an implementation faithfully reflects its design source
• Retrofitting an old screen to the current design system
• Designer delivered assets and you need a faithful, maintainable build

Skip as the primary skill for pure logic with no visual surface, or when intentionally diverging from design (experiments, internal tools with no spec) — still apply [[ui-craft]] and [[accessibility]] for user-facing output.

Process

Work in order. Don't write layout CSS until you've mapped tokens and components.

1. Inventory before you code

Gather what the handoff actually includes — and what's missing.

From the design file / spec:

• Frame(s) for each breakpoint — mobile, tablet, desktop (note which exist)
• Component instances vs one-off frames — what maps to the design system?
• Tokens — color styles, spacing scale, typography ramp, radii, shadows, grid
• Assets — icons (SVG preferred), illustrations, images, fonts, export settings
• Interaction notes — hover, focus, pressed, motion, transitions (if any)
• Copy — final strings, truncation rules, pluralization
• Annotations — spacing, behavior, edge cases the designer documented

In the codebase:

• Existing components that match (Button, Card, Input, Modal, …)
• Token source — CSS variables, Tailwind config, theme object, design-token package
• Layout primitives — grid, stack, container widths, breakpoint definitions
• Patterns for forms, tables, empty states, toasts

Gap list — write explicit questions for the designer or PM before implementation:

Missing: empty cart state, error on failed payment, focus ring style, behavior below 375px,
         loading skeleton vs spinner — need decision before build.

Unanswered gaps become expensive guesses in code.

2. Read the design for its system, not its surface

Designs are built from a system even when the file doesn't label it. Extract:

Layer	What to find	Map to code
Color	Primary, surface, border, text roles — not random hexes	--color-*, theme palette
Typography	Font family, sizes, weights, line heights	text-sm, heading-2, etc.
Spacing	4/8px grid or explicit scale	space-4, gap-6
Radii & borders	Corner radius, border width/color	token names
Elevation	Shadow levels	shadow-md, z-index scale
Breakpoints	Where layout changes	sm/md/lg definitions in code

If Figma variables or styles exist, use them as the source of truth — they name the system. If the design uses raw values everywhere, propose token mappings and confirm with design before locking in.

Do not copy hex/spacing from inspect panel into component CSS without checking if a token already exists for that role.

3. Reuse before you rebuild

If the design shows a button, card, or input you already ship — use the real component with the correct variant and size props.

// Prefer: system component + variant
<Button variant="primary" size="md">Save</Button>

// Not: new div styled to look like a button this week
<button className="bg-[#1a73e8] px-[18px] ...">Save</button>

When the design differs slightly from the existing component:

1. Check if it's intentional design evolution → update the system component (with design approval).
2. Check if it's a one-off → still prefer composition (Button + icon slot) over fork.
3. Only create a new component when the pattern is genuinely new and reusable.

Forked near-copies drift — spacing, focus rings, and hover states diverge within weeks.

4. Extract exact values for what's genuinely new

For elements that don't map to existing tokens, extract exact specs — don't approximate.

From Figma inspect / design spec:

• Width, height, padding, gap — note which axis
• Font: family, size, weight, line-height, letter-spacing
• Colors — hex + opacity; prefer mapping to a new token if repeated
• Border, radius, shadow — full stack
• Icon size and alignment relative to text

Approximation is how implementations diverge. "About 16px" becomes 14px on the next screen. Round only when the design system scale already rounds that way.

Document new tokens in the theme/token file — not scattered in the component — so the next handoff reuses them.

5. Structure first — semantics before cosmetics

Build the DOM structure and component hierarchy before pixel-perfect polish:

• Correct landmarks, headings, lists, forms ([[accessibility]])
• Component boundaries that match how the page will be maintained
• Data props and slots — where text, images, and actions plug in

A pixel-perfect div stack that needs restructuring for a11y or state logic is wasted work. Structure first, then tokens, then fine-tuning.

Slice vertically ([[incremental-delivery]]): one working section with real structure and one state before polishing the entire page.

6. Implement every state the mockup omits

The frame is one moment in time. The product has many ([[ui-craft]]). Plan and build:

State	Often missing from mockups	Decide explicitly
Default / populated	Usually shown	—
Hover / focus / active / disabled	Rarely all shown	Match system interaction tokens
Loading	Often omitted	Skeleton vs spinner; preserve layout
Empty	Often omitted	Message, illustration, CTA
Error	Often omitted	Inline vs banner; recovery action
Partial / truncated	Rarely shown	Long title, many tags, overflow
Success / confirmation	Sometimes	Toast, inline check, next step

If design didn't provide a state, implement from the design system pattern — don't ship blank or broken UI. Flag visual gaps to design for a follow-up polish pass.

7. Define responsive behavior — not just one width

A fixed-width mockup is a starting point. For each major breakpoint:

• What reflows — stack vs row, column count, nav pattern
• What hides or collapses — menus, sidebars, table → card
• Typography and spacing — do they step down on small screens?
• Touch targets — minimum ~44×44px on mobile; design may show desktop-only sizes

Implement and test at least:

• ~375px — small phone
• Design's primary width — often 1440 or 1280
• One middle breakpoint if layout shifts materially

Don't only pixel-match the artboard width and break everywhere else ([[browser-checks]]).

8. Accessibility the design file won't specify

Visual handoffs rarely include focus order, labels, or contrast math — code still must deliver ([[accessibility]]):

• Focus visible on every interactive control — use system focus ring tokens
• Labels on every form field — placeholder is not a label
• Contrast — text and icons on backgrounds meet WCAG AA (4.5:1 body, 3:1 large/UI)
• Keyboard — full flow without mouse; modals trap and restore focus
• Motion — respect prefers-reduced-motion for designed animations
• Alt text for meaningful images; decorative images empty alt

If design colors fail contrast, fix with design approval — don't ship illegible UI to match hex.

Semantic HTML and ARIA only where native semantics aren't enough — don't sacrifice structure for layout shortcuts.

9. Assets, icons, and motion

Icons — prefer SVG from the system icon set; match designed size via width/height or token. Don't rasterize icons as PNG unless the design requires it.

Images — export at appropriate resolution; use srcset/sizes for photos; explicit width/height or aspect-ratio to prevent layout shift.

Fonts — load only weights used; subset if large; fallbacks that don't change metrics badly.

Motion — if the design specifies duration/easing, implement with CSS/transitions; document values as tokens. If unspecified, use system defaults. Gate decorative motion behind reduced-motion.

Export from Figma with consistent naming; avoid duplicate assets that differ by 1px.

10. Compare and reconcile against the source

"Looks close" is not done. Verify fidelity:

1. Side-by-side — implementation next to design at the same viewport width.
2. Overlay — Figma overlay plugins, PixelParallel, or browser extensions for pixel diff.
3. Spot-check spacing — padding, gap, alignment between label and field, icon nudge.
4. States — each state compared to spec or system pattern, not only default.
5. Browser proof — console clean, responsive check, keyboard pass ([[browser-checks]]).

Reconcile differences deliberately:

Difference	Action
Bug — doesn't match approved design	Fix code
Design system token vs raw mockup value	Use token; confirm with design if visible
Design gap — state never designed	Use system pattern; ticket for design
Intentional engineering constraint	Note in PR; don't silent drift

Capture screenshot or recording for PR evidence.

11. Review handoff fidelity (PR / QA)

When reviewing someone else's implementation:

• Token usage vs hardcoded values
• System components vs re-created UI
• States beyond the happy path
• Responsive behavior at narrow and wide
• a11y — focus, labels, contrast
• Comparison evidence — screenshots at spec width

Approve when faithful and maintainable — not when "close enough" with silent drift.

12. Scenario playbooks

New page from full Figma frame

1. Inventory frames per breakpoint + gap list.
2. Map sections to components; identify reuse.
3. Structure + data wiring for one vertical slice.
4. Tokens and layout per section; states for each block.
5. Responsive + a11y pass; overlay compare; browser-checks.

New variant on existing component

1. Compare to current component API — extend variant vs new component.
2. Update design system with design approval if the pattern is global.
3. Storybook/docs for new variant; don't fork per page.

Design system drift — mockup uses raw values

1. Map raw values to nearest tokens; list deltas.
2. Ask design: intentional update or mockup sloppiness?
3. Update tokens if intentional; fix mockup reference if not.

No Figma — screenshot or PDF only

1. Extract what you can; list all ambiguities.
2. Don't invent spacing scale — align to codebase tokens.
3. Get sign-off on gaps before polish.

Retrofit old screen to new design

1. Diff old vs new design — what components can swap in place?
2. Migrate token-by-token; avoid half-old/half-new page.
3. Regression browser-check on critical flows.

Design review before build (early handoff)

1. Confirm breakpoints, states, and tokens exist in the file.
2. Confirm components in Figma match code component names.
3. Return incomplete handoff to design with specific gap list — cheaper than rework.

Common Rationalizations

• "It looks close enough." — Small drifts compound into an off-brand, inconsistent product.
• "I'll hardcode the values." — Hardcoding bypasses the system and rots when design updates.
• "The mockup only shows one state." — You must implement the rest from system patterns, not omit them.
• "Accessibility isn't in the design." — It's still required; build it in ([[accessibility]]).
• "I'll match pixels first, fix structure later." — Restructuring costs more than semantics-first.
• "This button is slightly different — I'll make a new one." — Forks multiply; extend the system.
• "Responsive is just scaling down." — Layout often must reflow, not shrink.
• "Overlay comparison is designer work." — Engineers own fidelity of what they ship.
• "Figma says 15px — we don't have that token." — Map to nearest token or add token; don't leave 15px in isolation.

Red Flags

• One-off hex/pixel values where design tokens exist
• Re-created component instead of existing system component
• Only the default mockup state implemented
• Pixel-perfect at design width but broken on mobile/tablet
• Missing focus, labels, or failing contrast
• No loading, empty, or error treatment
• Layout shift when images or data load
• Assets exported as wrong format or 3× duplicate PNGs
• Hardcoded copy that should be props or CMS content
• No comparison against source design before merge
• Gap list never sent — guessed behavior instead
• Animation with no reduced-motion path
• PR with no screenshot at spec viewport

Verification

• Handoff inventoried — breakpoints, tokens, assets, gaps documented
• Design system mapped — colors, type, spacing, radii use tokens not raw values
• Existing components reused; new components justified and added to system when global
• Exact specs extracted for genuinely new elements — no guessed "about" values
• Semantic structure built before pixel polish ([[accessibility]])
• All states implemented — hover/focus/disabled, loading, empty, error, overflow ([[ui-craft]])
• Responsive behavior defined and tested at small, middle, and design widths
• Focus, labels, contrast, keyboard, and reduced-motion handled
• Assets optimized — SVG icons, image dimensions, font weights only as needed
• Implementation compared to design — overlay/side-by-side; differences reconciled
• Browser verification — console, responsive, interaction ([[browser-checks]])
• PR includes comparison evidence; intentional deltas explained