# Design Token Inspector

## Objective

Show which design token produced any value on screen, instead of guessing at computed CSS.

A development-only inspector that reports, for a selected element, the tokens behind its colour, spacing, typography, radius, and shadow.

## 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 the app's existing token definitions and build the inspector on top of them, so the tool reports the same names the design system publishes rather than a second vocabulary invented for the tool.
2. Let a developer point at any element and see, per property, the token name, its resolved value, and where it came from — the element itself, an ancestor, or the theme default.
3. Resolve alias chains all the way down and display the whole path, so a surface colour that points at a semantic token that points at a palette primitive shows all three steps rather than only the last.
4. Report honestly when a value has no token behind it. An unmatched raw value is the most useful thing the inspector can surface, and it must be labelled as unmatched rather than approximated to the nearest token.
5. Do not ship the inspector to production users. Gate it behind a development build or an explicit internal flag, and confirm the code is absent from the production bundle rather than merely unreachable.

## 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

- Alias chains must be traced to their source token, and a circular or broken alias must be reported as broken rather than silently rendering the last value it happened to resolve to.
- Inherited values and locally declared values must be visually distinguished — a developer chasing a wrong colour needs to know whether to edit this element or its ancestor.
- The inspector must re-resolve when the active theme or breakpoint changes, because the same element can be driven by different tokens in light and dark, or at different widths.
- Leaving the tool in the production bundle leaks the internal token vocabulary and adds weight for every user; verify its absence in a built artefact, not just in configuration.
- Values produced by calculation or interpolation will not match any token exactly; show the expression and its inputs rather than claiming no token is involved.
- The inspector's own panel must not appear in its own readings, and hovering it must not change what is being inspected.
- Reporting which token is behind a value is this feature's job; deciding that an untokenised value is a defect and failing a check on it belongs to Design Token Linter — the inspector observes, the linter enforces.

## 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

- [ ] Selecting any element reports the token behind each of its colour, spacing, typography, radius, and shadow values.
- [ ] Alias chains are shown in full, from semantic name to source primitive.
- [ ] Inherited values are labelled differently from locally declared ones.
- [ ] Readings update correctly after a theme change and at every defined breakpoint.
- [ ] Values with no matching token are labelled as unmatched rather than rounded to the nearest one.
- [ ] The inspector is absent from production builds, verified against the built output.
- [ ] 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.