# Read and Unread State

## Objective

Show people which documents, threads, and records they have not looked at yet.

Per-user read state on content items — documents, records, comment threads, list rows — with unread markers and counts that stay correct across devices and bulk actions.

## 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. Apply this to content the user browses, not to notifications. If the app already has a notification inbox with unread handling, reuse that state machine for content rather than forking a second, subtly different one.
2. Decide and document the single rule for what marks an item read — opening it, dwelling on it for a moment, or an explicit action. Pick one and apply it everywhere.
3. Store read state per user, on the server. Client-only state means a phone and a laptop disagree about the same inbox.
4. Give the user manual control in both directions: mark as read, mark as unread, and mark all as read.
5. Derive unread counts from the same query that renders the list, so the badge and the list can never disagree.
6. Do NOT mark items read simply because they scrolled past. Passive scroll marking silently buries things people meant to come back to.

## 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

- Deleting or archiving an unread item must decrement the count immediately, not leave a badge pointing at nothing.
- Unread counts must respect the active filter or scope, and the UI must be clear about which scope the number describes.
- Bulk mark-as-read must be undoable, or at least confirmed, when it covers more than a screenful.
- Re-importing or reprocessing data must not resurrect items as unread. Key read state to the item, not to the row version.
- Two open tabs must converge. Marking read in one should not leave the other showing a stale badge indefinitely.
- Cap the displayed count at a sensible ceiling (99+) rather than rendering a four-digit badge that breaks the layout.
- In shared or team contexts, be explicit about whether read state is personal or shared. Guessing wrong here is a trust problem.

## 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

- [ ] Read state is stored per user on the server and matches across devices.
- [ ] One documented rule decides when an item becomes read.
- [ ] Users can mark items read and unread individually, and read in bulk.
- [ ] Unread counts stay correct after deletion, archiving, filtering, and bulk actions.
- [ ] Reimported data does not flip existing items back to unread.
- [ ] The badge count and the visible list never contradict each other.
- [ ] 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.