# Focus Ring System

## Objective

Give every focusable control one clear focus indicator that belongs to the design.

A single focus treatment applied consistently across buttons, links, inputs, cards, rows, and custom controls.

## Before You Begin

This feature is being added to an application that already exists and already
works. Do not scaffold a new project, and do not assume a blank slate.

Inspect the codebase first and establish:

- The existing application structure and where code of this kind already lives.
- The framework and version in use.
- The existing design system — colours, spacing, typography, and component conventions.
- Existing UI components you can reuse instead of writing new ones.
- The existing database structure, if this feature needs to persist anything.
- The existing authentication and authorization system, if this feature is user-scoped.
- Dependencies already installed, so you don't add a library that duplicates one.
- The existing test setup and conventions.

Only start writing code once you understand the above. If the application
already implements part of this feature, extend it rather than replacing it.

## Implementation Instructions

1. Inventory every focusable element in the app, including the ones made focusable by hand — clickable rows, cards, canvas objects, custom selects — and confirm each shows the shared treatment.
2. Distinguish focus arriving from the keyboard from focus arriving from a click, and show the ring for keyboard and programmatic focus. A ring appearing on every mouse press reads as a rendering fault and invites someone to remove it entirely.
3. Compose the ring so it stays visible on every surface the control can sit on: page background, card, coloured button, dark toolbar, selected row. A single-colour ring will disappear against at least one of them.
4. Draw the ring in a way that does not change the element's box size, so focusing a control never nudges its neighbours.
5. Do not strip the browser's default focus outline until the replacement is in place and verified on every control. A partial rollout leaves keyboard users with a set of invisible controls and no way to tell where they are.

## UI and UX Requirements

Match the application's existing design system exactly. Reuse its components,
spacing, and typography. This feature should look like it was always there.

## Responsive Requirements

Works on mobile, tablet, and desktop. Touch targets are large enough to hit on a
phone, and nothing overflows horizontally at 320px.

## Accessibility Requirements

- Fully keyboard navigable.
- Correct semantic elements and ARIA roles.
- Visible focus states.
- Meets WCAG AA contrast.
- Dynamic changes are announced to screen readers.
- Respects prefers-reduced-motion.

## Edge Cases

- Applying the ring on every focus event rather than on keyboard focus makes it appear on mouse clicks, which is what leads teams to delete focus styling altogether.
- A ring that reads well on the page background can vanish on a card, a coloured button, or a selected row — the treatment needs a contrasting outer edge or a surface-aware colour.
- Rings drawn outside the element are clipped by any ancestor with hidden overflow, which is common in scrollable lists, tables, and toolbars; either inset the ring in those contexts or allow the overflow.
- Removing the native outline before the replacement covers every control leaves gaps that are invisible until a keyboard user hits them.
- The ring's colour per theme belongs to the theme tokens, including High-Contrast Theme; this feature owns the ring's geometry and its application rules, not its palette values.
- Composite widgets such as menus, tab sets, and grids move focus within a single tab stop, so the ring must follow the active item rather than the wrapper.
- Elements focused programmatically after a route change or a validation failure must show the ring, or the user is moved somewhere with no indication of where.

## Testing

Exercise the feature end to end in the running application. Cover every edge case
above, then run the existing test suite and confirm nothing regressed.

## Acceptance Criteria

- [ ] Every focusable element in the app shows the shared focus treatment.
- [ ] The ring appears for keyboard and programmatic focus and not on ordinary mouse activation.
- [ ] The ring is visible against every surface a focusable control sits on.
- [ ] No ring is clipped by a scrollable or overflow-hidden ancestor.
- [ ] Focusing an element does not change its size or move adjacent content.
- [ ] No control anywhere relies on the removed native outline.
- [ ] The feature matches the existing design system.
- [ ] No existing functionality is broken.

## Adaptation Rules

- Match the existing design system. Do not introduce a new colour palette,
  spacing scale, or component library.
- Reuse existing components and utilities wherever they fit.
- Follow the naming, file layout, and code style already present.
- Do not upgrade, replace, or remove existing dependencies to make this
  feature fit. Adapt the feature to the app, not the app to the feature.
- Do not break existing functionality. If a change is genuinely required in
  existing code, make the smallest one that works and say so.
- If something in these instructions conflicts with how the application is
  built, follow the application and explain the deviation.

## Final Verification

Before you report the work as done:

1. Re-read the acceptance criteria above and check each one against what you
   actually built.
2. Run the application and exercise the feature end to end.
3. Run the existing test suite and confirm you have broken nothing.
4. Check the feature on mobile, tablet, and desktop widths.
5. Check keyboard navigation and focus handling.
6. Summarize what changed: files added, files modified, and anything you
   deliberately did differently because of how this application is built.

If any acceptance criterion is unmet, fix it before reporting completion.