---
type: guide
title: Per-User `solvedByMe` Across the Session Boundary
description: How the `ChallengesStore` signal cache guarantees that PlayerA's solved-by-me flags never leak into PlayerB's view across logout/login, including SSE-unauthorized and peer-logout invalidation.
tags: [guide, challenges, solvedByMe, session, logout, store, tester]
timestamp: 2026-07-23T03:45:00Z
---

# What this feature does

`ChallengesStore` is a `providedIn: 'root'` Angular singleton that survives
route navigation and SPA reloads. Its board cache holds a `BoardResponse`
whose cards carry a per-user `solvedByMe: boolean` flag (the `✓` glyph on
the card and the `You solved this challenge.` modal banner).

Because `solvedByMe` is **server-computed from the JWT-authenticated user**
(`backend/src/modules/challenges/challenges.service.ts:75-125`), the
backend has always returned the correct value per request. The risk was
purely on the frontend: if PlayerA loaded the board, then logged out, and
PlayerB logged in **before** the new board response arrived, PlayerB could
briefly see PlayerA's `solvedByMe` flags (or worse, `applySolveEvent`
from a third-party solve could overwrite PlayerB's `solvedByMe` because
the store still believed it was PlayerA).

This change closes that gap at three coordinated points:

1. `ChallengesStore.setMyUserId(id)` — now returns the previous id, and
   whenever the cached state belongs to a different or unknown user, the
   store calls `reset()` before recording the new id. This catches the
   "orphan board loaded before the first `setMyUserId`" path (SSR, hot
   reload, page mount before auth hydration).
2. `ChallengesStore.reset()` — new public method; stops the SSE source,
   clears the one-second tick interval, and wipes `_board`,
   `_selectedDetail`, `_myUserId`, `_error`, `_loading`, the countdown
   reload handler, and all `solveListeners`.
3. `HomeComponent.onLogout()` and `HomeComponent.handleSessionInvalidated()`
   — both now inject `ChallengesStore` and call `challengesStore.reset()`
   alongside the existing `userStore.reset()`. This guarantees the board
   cache is cleared on the way out, regardless of whether logout went
   through the GUI menu or was triggered by a peer-tab broadcast / SSE
   `401`/`403`.

Additionally, the mutation paths (`applySolveEvent`, `applySubmitResponse`)
stopped OR-ing `solvedByMe`. They now take the server's authoritative
value verbatim, so a third-party solve cannot falsely flip a player's
`solvedByMe` from `false` to `true` even within a single session.

# Why a new concept doc

The fix spans three files that previously did not coordinate
(`ChallengesStore`, `HomeComponent`, `ChallengesPage`) and adds a public
`reset()` method to a previously opaque singleton. A tester verifying
the per-user invariant should not have to diff the store to learn the
reset rules, and a developer wiring a new "logout-adjacent" feature
should not have to guess that the challenges board also needs to be
flushed.

# Tester flows

> The following assume a configured event window with the event in
> `running` state and at least one challenge (`alpha`) that has been
> pre-solved by PlayerA.

## User switch via menu logout

1. Sign in as **PlayerA** and navigate to `/challenges`.
2. Confirm `alpha` shows the `✓` glyph (`.check` inside
   `[data-testid="challenge-card-alpha"]`) and the success border.
3. Open the user menu (`[data-testid="user-menu-trigger"]`) and click
   **Logout**.
4. The SPA navigates to `/login`; the `ChallengesStore` cache is cleared.
5. Sign in as **PlayerB** (a different account that has not solved
   `alpha`).
6. Navigate to `/challenges`. Confirm `alpha` shows:
   * `120 pts` and `4 solves` (the global counter — unchanged).
   * **No** `✓` glyph and **no** success border on the card.
   * **No** `[data-testid="modal-solved-banner"]` (`You solved this
     challenge.`) when the card is opened.

## User switch via peer-tab SSE unauthorized

1. Open the SPA in **Tab A** and **Tab B**, both signed in as PlayerA
   on `/challenges`. `alpha` shows `✓`.
2. From the server side, revoke PlayerA's refresh-cookie/session (e.g. an
   admin row-edit or a manual `refresh_token` deletion).
3. `EventStatusStore`'s SSE reconnect returns `401`. `Tab A` clears state
   and navigates to `/login`. The `ChallengesStore` cache in `Tab A` is
   reset.
4. In **Tab B**, the user menu can also be used to sign out as PlayerB
   (or wait for the broadcast from Tab A). Confirm the board does not
   briefly show PlayerA's `solvedByMe` on PlayerB's view during the
   transition.

## Third-party solve does not flip `solvedByMe`

1. Sign in as **PlayerB**. Confirm `alpha` shows `solvedByMe = false`.
2. From a second browser session, sign in as **PlayerA** and solve
   `alpha`. The SSE `solve` frame is broadcast.
3. In PlayerB's tab, confirm `alpha`'s `✓` does **not** appear, the
   border does **not** flip to success, and the modal does **not** show
   the solved banner. `livePoints` and `solveCount` may still update
   (those are global, not per-user).

## Negative cases

| Action | Expected |
|---|---|
| Reload `/challenges` as the same PlayerA | The board cache is preserved across the SPA reload (signal singletons survive), so `alpha` still shows `✓` after the reload completes its `load()`. |
| Navigate away from `/challenges` and back | The singleton keeps the cache; `alpha` still shows `✓`. |
| Have PlayerB solve `alpha` for the first time | The submit response drives `applySubmitResponse`; `solvedByMe` flips to `true`, `✓` appears, and the card border flips to success. |
| Logout PlayerB then log PlayerB back in (same user) | The store is reset on logout, so the new `load()` fetches a fresh board and `solvedByMe` is recomputed by the server. |

# Visual / interactive elements

There are **no new UI controls**. The existing card and modal selectors
are the regression targets:

| Element | Selector | After user-switch |
|---|---|---|
| Solved check | `.check` inside `[data-testid="challenge-card-<uuid>"]` | **Absent** for PlayerB if PlayerA solved it. |
| Solved border | `[data-testid="challenge-card-<uuid>"]` (border color) | Default border color, not success. |
| Modal solved banner | `[data-testid="modal-solved-banner"]` | **Absent** for PlayerB. |
| Awarded banner | `[data-testid="modal-awarded-banner"]` | **Absent** (no award yet for PlayerB). |

# How it works (developer map)

## `ChallengesStore` singleton lifecycle

`ChallengesStore` is `providedIn: 'root'`, so a single instance is
shared by every consumer (`ChallengesPage`, `HomeComponent`, any future
feature that injects it). The store never calls `reset()` itself based
on time — it only resets in response to explicit calls or to a
`setMyUserId` change.

### `setMyUserId(id: string | null): string | null`

Returns the previous user id (or `null`). If the store currently holds
cached board or detail data **and** the previous id differs from the new
id, it calls `reset()` first. The four cases:

| Previous `_myUserId` | New `id` | Cached state present? | Action |
|---|---|---|---|
| `null` | `playerB` | No | Just record the id. |
| `null` | `playerB` | Yes (orphan) | **Reset**, then record. *(new — closes the bug)* |
| `playerA` | `playerA` | Yes | Just record (re-mount path; keeps cache). |
| `playerA` | `playerB` | Yes | **Reset**, then record. |
| `playerA` | `null` | Yes | **Reset**, then record `null`. |

### `reset(): void`

New public method. Calls `stop()` (closes the SSE source, clears the
1-second tick interval), then nulls every signal and clears
`solveListeners` and `countdownZeroHandler`. Idempotent.

### Mutation paths take server values verbatim

`applySolveEvent` previously computed
`solvedByMe: card.solvedByMe || isMine`. This was wrong because if
`card.solvedByMe` was `true` from a stale cache and `isMine` was `false`
(a third party solved), it would leave the flag `true`. It is now
`solvedByMe: isMine ? true : card.solvedByMe`, so a non-mine event can
never promote `false` → `true`. `applySubmitResponse` no longer ORs
either — it takes `response.challenge.solvedByMe` directly, since the
server is authoritative.

## `ChallengesPage` mount

`ChallengesPage.ngOnInit()` now calls
`this.store.setMyUserId(user?.id ?? null)` (passing `null` explicitly
when there is no user, instead of the previous `if (user?.id)` guard).
This ensures the store gets the call even on the unauthenticated edge
case so the cache-reset decision runs once.

## `HomeComponent` session-boundary reset

`HomeComponent` injects `ChallengesStore` and calls
`challengesStore.reset()` in two places:

| Trigger | Method |
|---|---|
| User clicked Logout in the menu | `onLogout()` (after `await this.auth.logout()`, before `navigateByUrl('/login')`) |
| Peer-tab broadcast or SSE `401`/`403` | `handleSessionInvalidated()` (alongside `userStore.reset()` and the modal/menu close) |

The `ChallengesStore` is reset **before** navigation so the SPA never
renders `/challenges` with a stale board.

## Test coverage

| File | What it pins down |
|---|---|
| `tests/frontend/challenges.store.reset.spec.ts` | New: `reset()` clears board / detail / myUserId / SSE; `setMyUserId` flushes when switching; **regression for orphan board** (cached board with no recorded user id is cleared when PlayerB's id is set); third-party solve does not flip `solvedByMe`; `applySubmitResponse` takes the server value verbatim. |
| `tests/frontend/challenges.store.spec.ts` | Updated: the "marks solvedByMe" and "does not double-count" tests now call `setMyUserId('me-1')` *before* `load()`, so they exercise the realistic page-mount sequence. |

# See also

- [Challenges Board](/guides/challenges-board.md)
- [Challenges Endpoints](/api/challenges.md)
- [Cross-Tab Authenticated Shell Invalidation](/guides/cross-tab-invalidation.md)
- [Frontend Structure](/architecture/frontend-structure.md)
- [Key Files Index](/architecture/key-files.md)