# Knowledge Base Chat

## Objective

Answer questions from the app's approved help articles and policies, with sources shown.

A retrieval-backed answering surface over the app's published knowledge sources, restricted to what the asker is allowed to read.

## 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. Define which collections count as knowledge sources and mark each with an audience — public, customer, or internal. Filter the retrievable set by the asker's audience before retrieval, not after the answer is written.
2. Restrict retrieval to currently published versions. Drafts, archived articles, and superseded revisions must be excluded from the corpus, not merely ranked lower.
3. Cite every source used, and when two retrieved sources contradict each other, present both with their dates rather than picking one and hiding the conflict.
4. Keep the answer inside the retrieved evidence. If retrieval returns nothing relevant, say the knowledge base does not cover it and offer the search results or a route to support.
5. Re-index a source when it is published, edited, unpublished, or has its audience changed, using the app's existing background-job system, and drop any cached answer that cited it.

## 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

- An internal policy retrieved for a customer question is a disclosure incident. Audience filtering must run inside the retrieval query so no restricted passage ever reaches the model.
- A draft rewrite of an article must never outrank the published version. If a source has no published revision, it is not in the corpus at all.
- Contradictory sources are common when an old article was never retired. Show both with publication dates and say which is more recent rather than silently averaging them.
- Answering beyond the retrieved evidence produces plausible policy that does not exist. Anything the retrieved passages do not support must be omitted, not softened with a hedge.
- Edits must invalidate cached answers immediately. Serving yesterday's answer with today's citation is worse than having no cache, because the citation looks like verification.
- Show the answer as assistance, not authority, and keep the underlying articles one click away so a user can check it.
- When the model is unavailable, fall back to the existing keyword search over the same articles rather than showing an empty page.
- Document Question Answering covers a single file uploaded by one user; this feature covers the app's shared published sources. Keep the two corpora and their permission models separate.

## 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

- [ ] Retrieval is filtered by the asker's audience before any passage reaches the model.
- [ ] Only currently published revisions are retrievable; drafts and archived material are excluded.
- [ ] Every answer lists its sources, and conflicting sources are shown together with dates.
- [ ] Questions unsupported by retrieved evidence return an explicit no-answer response.
- [ ] Publishing, editing, or unpublishing a source re-indexes it and invalidates answers that cited it.
- [ ] Keyword search over the same articles remains available when the model is unavailable.
- [ ] 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.