# Return-to-Origin Navigation

## Objective

Send people back to the exact list they came from, filters and all.

A shared mechanism for remembering where a workflow started and returning the user there when it finishes.

## 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. Add one reusable way to carry an origin through a workflow, and use it everywhere instead of hardcoded 'back to index' links.
2. Capture the full origin state — filters, page, sort, search query, and scroll position — not just the path.
3. Validate the return target before redirecting: it must be a path inside this app that the current user is allowed to see.
4. Scope the origin to the workflow that set it and clear it on completion, so a stale value cannot hijack an unrelated flow later.
5. Do NOT trust the Referer header or an unvalidated redirect parameter. Both are attacker-controlled and turn this into an open redirect.

## 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 origin pointing at a deleted or now-forbidden record must fall back to a sane default, not a 404.
- An external or protocol-relative URL must be rejected outright.
- Cancelling must return to the origin too, not just saving.
- Multi-step flows must survive a refresh mid-way without losing the origin.
- Restore scroll position only when the list still contains the item; otherwise return to the top.
- Do not append the origin to URLs the user might share — a bookmark should not carry someone else's return state.

## 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

- [ ] Finishing or cancelling a nested task returns to the originating list with filters, sort, and page intact.
- [ ] Return targets are validated as internal and permitted before use.
- [ ] An invalid or expired origin falls back to a documented default destination.
- [ ] Origin state does not leak into unrelated workflows.
- [ ] The mechanism is used consistently across the app rather than reimplemented per screen.
- [ ] 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.