# Password Reset

## Objective

Let people back in without opening a hole for everyone else.

A request-and-reset flow with expiring single-use tokens, identical public responses regardless of whether the account exists, and session cleanup afterwards.

## 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. Return the same message and the same rough response time whether or not the address has an account. The reset form is the most common account-enumeration oracle in any app.
2. Store tokens hashed, expire them within an hour or so, and consume them on use.
3. After a successful reset, revoke all other sessions and notify the account by email that the password changed.
4. Rate-limit both the request step and the token-submission step, per address and per IP.
5. Do not sign the user in automatically from the reset link alone unless the app has decided that link possession equals authentication. Say which you chose and be consistent.

## 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

- Requesting several resets must leave exactly one usable token — invalidate the earlier ones and say so in the email.
- A reset link opened after the password already changed must show a neutral expired state, not an error mentioning the account.
- Return-to URLs carried through the flow must be validated against an allowlist; an open redirect here hands over the session.
- Reset tokens must never appear in query strings that get logged, sent as referrers, or captured by analytics.
- If 2FA is enabled, resetting the password must not bypass it.
- The reset must reject the current password if the app forbids reuse, without confirming what the old one was.

## 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

- [ ] Request responses are identical for existing and non-existing addresses.
- [ ] Tokens are hashed, expiring, and single-use, with older tokens invalidated on reissue.
- [ ] A successful reset revokes other sessions and emails the account.
- [ ] Return destinations are validated against an allowlist.
- [ ] Both request and submission steps are rate-limited.
- [ ] Reset does not bypass two-factor authentication.
- [ ] 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.