# Service Incident Banner

## Objective

Warn users about outages and maintenance inside the app, without a deploy.

An operator-controlled banner announcing degraded service, incidents, or planned maintenance to the right users.

## 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. Give operators a way to create, schedule, and end a banner from an admin screen. Requiring a deploy to announce an outage means it goes out late or not at all.
2. Support severity levels with different treatments: informational, degraded, and outage.
3. Let a banner target a subset of users by plan, region, workspace, or affected feature, and default to nobody rather than everybody.
4. Support a scheduled start and an automatic expiry, so a maintenance notice does not linger for a week after the work is done.
5. Serve the banner from a path that does not depend on the main application API. A banner that goes down with the thing it is announcing is useless.

## 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

- Informational banners may be dismissed; an active outage banner must stay until the incident ends.
- A dismissal must be remembered per user and per banner, and must reset if the message is edited.
- The banner must not cover fixed navigation or shift the layout when it appears.
- Two active incidents need a defined order; show the highest severity rather than stacking three bars.
- Copy must be written for customers, not for engineers. No internal service names, no ticket IDs.
- Link to a status page if one exists, and make sure that link works when the app does not.

## 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

- [ ] Operators can publish, schedule, and expire a banner without a deploy.
- [ ] Banners can target specific plans, regions, or workspaces.
- [ ] Severity is reflected in the treatment, and critical banners cannot be dismissed.
- [ ] Dismissals persist per user and reset when the message changes.
- [ ] The banner renders even when the primary API is degraded.
- [ ] Expired and scheduled banners appear and disappear on time.
- [ ] 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.