# OKLCH Theme Tokens

## Objective

Define colour perceptually so a theme can shift without contrast collapsing somewhere.

A colour foundation expressed as lightness, chroma, and hue values from which every theme in the app is derived.

## 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. Find every colour the app currently defines as an opaque hex or RGB literal and re-express it as lightness, chroma, and hue, so that darkening a theme becomes a predictable adjustment rather than a fresh guess at a new hex value.
2. Hold the semantic roles constant while the underlying values move — danger must mean danger in every theme even when its lightness and hue differ. The role vocabulary itself belongs to Semantic Color Tokens; extend that set rather than inventing a parallel one here.
3. Emit a compiled fallback value beside every perceptual definition for the renderers that will not parse the newer syntax: email templates, PDF and print output, older embedded webviews, and any build tool in the pipeline that rewrites colour.
4. Record in the token source which values a person may edit and which are derived from them, so nobody hand-tunes a step that the next regeneration will silently overwrite.
5. Do not convert the existing palette mechanically and call it finished. A faithful one-to-one conversion preserves every contrast mistake the old palette had; check each foreground and background pair after conversion and correct the lightness where it was already failing.

## 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

- Tooling that cannot parse the colour space will drop the declaration entirely and render the element unstyled or transparent, so every token needs a compiled fallback emitted alongside it rather than assumed.
- A chroma value that sits outside the display gamut will be clipped by the browser in ways that differ between devices — clamp it yourself to a defined in-gamut value so the same token does not render as two different colours on two screens.
- A semantic role must resolve to something in every theme. A token defined only for the light theme leaves a component with no colour at all in dark mode, which usually shows up as inherited black text on a near-black surface.
- Users and operators need to know which tokens are theirs to edit. An undocumented editable value gets changed, then reverted by a regeneration, and the report comes back as an intermittent bug.
- Interpolating between two perceptual colours in a gradient does not follow the same path as interpolating between their hex equivalents; check that existing gradients still pass through the intended midpoint.
- Rounding lightness to too few decimal places collapses adjacent steps of a ramp into the same rendered colour, which is only visible on large flat surfaces.
- A colour composited over another with alpha no longer has the lightness the token claims — measure the result, not the declaration.

## 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 colour in the shared token source is defined by lightness, chroma, and hue rather than by a literal hex value.
- [ ] Each perceptual definition ships with a compiled fallback that renders correctly in email, print, and older webviews.
- [ ] Out-of-gamut values are clamped to a defined in-gamut result rather than left to the browser to clip.
- [ ] Every semantic role resolves to a value in every theme, with no unresolved tokens.
- [ ] The token source states which values are user-editable and which are derived.
- [ ] Foreground and background pairs meet their contrast thresholds after conversion, including pairs that failed before it.
- [ ] 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.