diff --git a/docs/ISSUE-301-CLIENT-ACTION-GATING-ARTIFACT.md b/docs/ISSUE-301-CLIENT-ACTION-GATING-ARTIFACT.md
new file mode 100644
index 0000000..51cc364
--- /dev/null
+++ b/docs/ISSUE-301-CLIENT-ACTION-GATING-ARTIFACT.md
@@ -0,0 +1,52 @@
+# Issue #301 Artifact — Client action gating from canonical phase state
+
+Refs: #287, #301
+
+## What changed
+
+Frontend host/player shells now prefer the canonical phase exposed by `phase_view_model.current_phase` when deciding:
+
+- which gameplay actions are enabled
+- whether reveal data should still be shown
+- which SPA hash-route should represent the active game state
+
+This tightens the #301 slice so the client stays aligned with backend canonicalisation even when `session.status` lags during reveal/scoreboard promotion.
+
+## Gated UI actions by phase
+
+### Lobby
+- **Host:** `startRound`
+- **Player:** `join`
+
+### Bluff / lie
+- **Host:** `showQuestion`
+- **Player:** `submitLie`
+- **Blocked:** guess submission, scoreboard load, next round, finish game
+
+### Guess
+- **Host:** `mixAnswers`, `calculateScores`
+- **Player:** `submitGuess`
+- **Blocked:** lie submission, scoreboard load, next round, finish game
+
+### Reveal
+- **Host:** `loadScoreboard`
+- **Player:** display-only reveal state
+- **Blocked:** start next round, finish game, guess/lie submission
+
+### Scoreboard
+- **Host:** `startNextRound`, `finishGame`
+- **Player:** display-only reveal/scoreboard state
+- **Blocked:** scoreboard reload, guess/lie submission
+
+## Test evidence
+
+Targeted tests added/updated for:
+
+- host shell canonical gating and route sync when `current_phase` differs from `session.status`
+- player shell canonical gating and route sync when `current_phase` differs from `session.status`
+- shared gameplay phase machine gating from canonical permissions
+- shared API mapper contract coverage, including reveal/scoreboard payload stability
+
+## Contract note
+
+No backend protocol redesign was introduced. This follow-up only preserves and consumes the existing canonical phase/action contract more strictly on the client side.
diff --git a/frontend/angular/src/app/features/host/host-shell.component.spec.ts b/frontend/angular/src/app/features/host/host-shell.component.spec.ts
index d57ff4d..0d18e05 100644
--- a/frontend/angular/src/app/features/host/host-shell.component.spec.ts
+++ b/frontend/angular/src/app/features/host/host-shell.component.spec.ts
@@ -21,6 +21,7 @@ function createFetchRouteMock(handler: FetchRouteHandler): FetchMock {
 function sessionDetailPayload(
   status: string,
   options?: {
+    currentPhase?: string;
     roundQuestionId?: number | null;
     reveal?: {
       correct_answer: string;
@@ -81,6 +82,7 @@ function sessionDetailPayload(
           },
     phase_view_model: {
       status,
+      current_phase: options?.currentPhase ?? status,
       round_number: 1,
       players_count: 2,
       constraints: {
@@ -89,14 +91,18 @@ function sessionDetailPayload(
         min_players_reached: true,
         max_players_allowed: true,
       },
+      readiness: {
+        question_ready: (options?.currentPhase ?? status) !== 'lobby',
+        scoreboard_ready: (options?.currentPhase ?? status) === 'reveal' || (options?.currentPhase ?? status) === 'scoreboard',
+      },
       host: {
-        can_start_round: status === 'lobby',
-        can_show_question: status === 'lie',
-        can_mix_answers: status === 'lie' || status === 'guess',
-        can_calculate_scores: status === 'guess',
-        can_reveal_scoreboard: status === 'reveal',
-        can_start_next_round: status === 'reveal',
-        can_finish_game: status === 'reveal',
+        can_start_round: (options?.currentPhase ?? status) === 'lobby',
+        can_show_question: (options?.currentPhase ?? status) === 'lie',
+        can_mix_answers: (options?.currentPhase ?? status) === 'lie' || (options?.currentPhase ?? status) === 'guess',
+        can_calculate_scores: (options?.currentPhase ?? status) === 'guess',
+        can_reveal_scoreboard: (options?.currentPhase ?? status) === 'reveal',
+        can_start_next_round: (options?.currentPhase ?? status) === 'scoreboard',
+        can_finish_game: (options?.currentPhase ?? status) === 'scoreboard',
       },
       player: {
         can_join: status === 'lobby',
@@ -259,7 +265,7 @@ describe('HostShellComponent gameplay wiring', () => {
     component.scoreboardPayload = '{"leaderboard":[]}';
     component.finalLeaderboardPayload = '{"leaderboard":[{"nickname":"Old","score":1}]}' ;
     component.finalLeaderboard = [{ id: 9, nickname: 'Old', score: 1 }];
-    component.session = sessionDetailPayload('reveal', { roundQuestionId: 77 }) as any;
+    component.session = sessionDetailPayload('scoreboard', { roundQuestionId: 77 }) as any;
 
     await component.startNextRound();
 
@@ -296,7 +302,7 @@ describe('HostShellComponent gameplay wiring', () => {
 
     const component = new HostShellComponent();
     component.sessionCode = 'ABCD12';
-    component.session = sessionDetailPayload('reveal', { roundQuestionId: 77 }) as any;
+    component.session = sessionDetailPayload('scoreboard', { roundQuestionId: 77 }) as any;
 
     await component.finishGame();
     expect(component.finishError).toContain('Finish game failed: Final leaderboard timeout');
@@ -320,7 +326,7 @@ describe('HostShellComponent gameplay wiring', () => {
 
     const component = new HostShellComponent();
     component.sessionCode = '   ';
-    component.session = sessionDetailPayload('reveal', { roundQuestionId: 77 }) as any;
+    component.session = sessionDetailPayload('scoreboard', { roundQuestionId: 77 }) as any;
 
     await component.startNextRound();
     await component.finishGame();
@@ -351,6 +357,10 @@ describe('HostShellComponent gameplay wiring', () => {
     for (const status of ['lie', 'guess', 'scoreboard'] as const) {
       component.session = sessionDetailPayload(status, { roundQuestionId: 77 }) as any;
       await component.loadScoreboard();
+    }
+
+    for (const status of ['lie', 'guess', 'reveal'] as const) {
+      component.session = sessionDetailPayload(status, { roundQuestionId: 77 }) as any;
       await component.startNextRound();
       await component.finishGame();
     }
@@ -361,16 +371,42 @@ describe('HostShellComponent gameplay wiring', () => {
     component.session = sessionDetailPayload('reveal', { roundQuestionId: 77 }) as any;
     expect(component.canCalculateScores).toBe(false);
     expect(component.canLoadScoreboard).toBe(true);
-    expect(component.canStartNextRound).toBe(true);
-    expect(component.canFinishGame).toBe(true);
+    expect(component.canStartNextRound).toBe(false);
+    expect(component.canFinishGame).toBe(false);
 
     component.session = sessionDetailPayload('scoreboard', { roundQuestionId: 77 }) as any;
     expect(component.canLoadScoreboard).toBe(false);
-    expect(component.canStartNextRound).toBe(false);
-    expect(component.canFinishGame).toBe(false);
+    expect(component.canStartNextRound).toBe(true);
+    expect(component.canFinishGame).toBe(true);
     expect(fetchMock).not.toHaveBeenCalled();
   });
 
+  it('prefers canonical current_phase for reveal panel and host routing when status lags behind', async () => {
+    const fetchMock: FetchMock = vi.fn().mockResolvedValue(
+      jsonResponse(200, sessionDetailPayload('reveal', { currentPhase: 'scoreboard', roundQuestionId: 77, reveal: { correct_answer: 'Mercury' } }))
+    );
+    vi.stubGlobal('fetch', fetchMock);
+
+    const replaceState = vi.fn();
+    vi.stubGlobal('window', {
+      location: { hash: '#/host/reveal/ABCD12' },
+      history: { state: null, replaceState },
+      sessionStorage: { getItem: vi.fn().mockReturnValue(null), setItem: vi.fn() },
+    });
+
+    const component = new HostShellComponent();
+    component.sessionCode = 'ABCD12';
+
+    await component.refreshSession();
+
+    expect(component.gameplayPhase).toBe('scoreboard');
+    expect(component.showRevealPanel).toBe(true);
+    expect(component.canLoadScoreboard).toBe(false);
+    expect(component.canStartNextRound).toBe(true);
+    expect(component.canFinishGame).toBe(true);
+    expect(replaceState).toHaveBeenCalledWith(null, '', '#/host/scoreboard/ABCD12');
+  });
+
   it('syncs host hash-route with latest phase after refresh without page reload', async () => {
     const fetchMock: FetchMock = vi.fn().mockResolvedValue(jsonResponse(200, sessionDetailPayload('guess', { roundQuestionId: 77 })));
     vi.stubGlobal('fetch', fetchMock);
@@ -408,12 +444,12 @@ describe('HostShellComponent gameplay wiring', () => {
 
     component.session = sessionDetailPayload('reveal') as any;
     expect(component.canLoadScoreboard).toBe(true);
-    expect(component.canStartNextRound).toBe(true);
-    expect(component.canFinishGame).toBe(true);
+    expect(component.canStartNextRound).toBe(false);
+    expect(component.canFinishGame).toBe(false);
 
     component.session = sessionDetailPayload('scoreboard') as any;
     expect(component.canLoadScoreboard).toBe(false);
-    expect(component.canStartNextRound).toBe(false);
-    expect(component.canFinishGame).toBe(false);
+    expect(component.canStartNextRound).toBe(true);
+    expect(component.canFinishGame).toBe(true);
   });
 });
diff --git a/frontend/angular/src/app/features/host/host-shell.component.ts b/frontend/angular/src/app/features/host/host-shell.component.ts
index 9eb219a..5c2826a 100644
--- a/frontend/angular/src/app/features/host/host-shell.component.ts
+++ b/frontend/angular/src/app/features/host/host-shell.component.ts
@@ -48,7 +48,7 @@ type LeaderboardResponse = FinishGameResponse;
       <ul>
         <li *ngFor="let p of session.players">{{ p.nickname }}: {{ p.score }}</li>
       </ul>
-      <div class="panel" *ngIf="session.reveal && (session.session.status === 'reveal' || session.session.status === 'scoreboard')">
+      <div class="panel" *ngIf="showRevealPanel">
         <h3>Reveal</h3>
         <p><strong>Korrekt svar:</strong> {{ session.reveal.correct_answer }}</p>
         <p><strong>Spørgsmål:</strong> {{ session.reveal.prompt }}</p>
@@ -163,6 +163,10 @@ export class HostShellComponent implements OnInit, OnDestroy {
     return isHostGameplayActionAllowed(this.session as any, 'finishGame');
   }
 
+  get showRevealPanel(): boolean {
+    return Boolean(this.session?.reveal && (this.gameplayPhase === 'reveal' || this.gameplayPhase === 'scoreboard'));
+  }
+
   copy(key: string): string {
     return t(key, this.locale);
   }
@@ -364,7 +368,7 @@ export class HostShellComponent implements OnInit, OnDestroy {
       return;
     }
 
-    const phase = this.session.session.status || 'lobby';
+    const phase = this.gameplayPhase ?? this.session.session.status ?? 'lobby';
     const code = this.normalizeCode(this.session.session.code || this.sessionCode);
     if (!code) {
       return;
diff --git a/frontend/angular/src/app/features/player/player-shell.component.spec.ts b/frontend/angular/src/app/features/player/player-shell.component.spec.ts
index 389d682..15c908e 100644
--- a/frontend/angular/src/app/features/player/player-shell.component.spec.ts
+++ b/frontend/angular/src/app/features/player/player-shell.component.spec.ts
@@ -16,6 +16,7 @@ function jsonResponse(status: number, body: unknown) {
 function sessionDetailPayload(
   status: string,
   options?: {
+    currentPhase?: string;
     answers?: string[];
     players?: Array<{ id: number; nickname: string; score: number }>;
     roundQuestionId?: number | null;
@@ -79,6 +80,7 @@ function sessionDetailPayload(
           },
     phase_view_model: {
       status,
+      current_phase: options?.currentPhase ?? status,
       round_number: 1,
       players_count: (options?.players ?? []).length,
       constraints: {
@@ -87,6 +89,10 @@ function sessionDetailPayload(
         min_players_reached: true,
         max_players_allowed: true,
       },
+      readiness: {
+        question_ready: (options?.currentPhase ?? status) !== 'lobby',
+        scoreboard_ready: (options?.currentPhase ?? status) === 'reveal' || (options?.currentPhase ?? status) === 'scoreboard',
+      },
       host: {
         can_start_round: false,
         can_show_question: false,
@@ -97,10 +103,10 @@ function sessionDetailPayload(
         can_finish_game: false,
       },
       player: {
-        can_join: status === 'lobby',
-        can_submit_lie: status === 'lie',
-        can_submit_guess: status === 'guess',
-        can_view_final_result: status === 'finished',
+        can_join: (options?.currentPhase ?? status) === 'lobby',
+        can_submit_lie: (options?.currentPhase ?? status) === 'lie',
+        can_submit_guess: (options?.currentPhase ?? status) === 'guess',
+        can_view_final_result: (options?.currentPhase ?? status) === 'finished',
       },
     },
   };
@@ -437,6 +443,34 @@ describe('PlayerShellComponent gameplay wiring', () => {
     expect(values.get('wpp.session-context')).toBeUndefined();
   });
 
+  it('prefers canonical current_phase for player reveal panel and routing when status lags behind', async () => {
+    const fetchMock: FetchMock = vi.fn().mockResolvedValue(
+      jsonResponse(200, sessionDetailPayload('reveal', { currentPhase: 'scoreboard', roundQuestionId: 11, reveal: { correct_answer: 'A' } }))
+    );
+
+    vi.stubGlobal('fetch', fetchMock);
+
+    const replaceState = vi.fn();
+    const localStorage = { getItem: vi.fn().mockReturnValue(null), setItem: vi.fn(), removeItem: vi.fn() };
+    vi.stubGlobal('window', {
+      location: { hash: '#/player/reveal/ABCD12' },
+      history: { state: null, replaceState },
+      localStorage,
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+    });
+
+    const component = new PlayerShellComponent();
+    component.sessionCode = 'ABCD12';
+
+    await component.refreshSession();
+
+    expect(component.gameplayPhase).toBe('scoreboard');
+    expect(component.showRevealPanel).toBe(true);
+    expect(component.showGuessControls).toBe(false);
+    expect(replaceState).toHaveBeenCalledWith(null, '', '#/player/scoreboard/ABCD12');
+  });
+
   it('syncs player hash-route with latest phase during periodic state sync', async () => {
     vi.useFakeTimers();
 
diff --git a/frontend/angular/src/app/features/player/player-shell.component.ts b/frontend/angular/src/app/features/player/player-shell.component.ts
index 2e4e59f..a514f7a 100644
--- a/frontend/angular/src/app/features/player/player-shell.component.ts
+++ b/frontend/angular/src/app/features/player/player-shell.component.ts
@@ -95,7 +95,7 @@ function resolveLocalStorage(): Storage | undefined {
         <button *ngIf="submitError?.kind === 'guess'" (click)="submitGuess()" [disabled]="loading || !canSubmitGuess">{{ copy('player.retry_guess_submit') }}</button>
       </ng-container>
 
-      <div class="panel" *ngIf="session.reveal && (session.session.status === 'reveal' || session.session.status === 'scoreboard')">
+      <div class="panel" *ngIf="showRevealPanel">
         <h3>Reveal</h3>
         <p><strong>Korrekt svar:</strong> {{ session.reveal.correct_answer }}</p>
         <p><strong>Spørgsmål:</strong> {{ session.reveal.prompt }}</p>
@@ -221,6 +221,10 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     return isPlayerGameplayActionAllowed(this.session as any, 'submitGuess');
   }
 
+  get showRevealPanel(): boolean {
+    return Boolean(this.session?.reveal && (this.gameplayPhase === 'reveal' || this.gameplayPhase === 'scoreboard'));
+  }
+
   private readonly handleOnline = (): void => {
     this.connectionState = 'reconnecting';
     void this.retryReconnect();
@@ -469,7 +473,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
       return;
     }
 
-    const phase = this.session.session.status || 'lobby';
+    const phase = this.gameplayPhase ?? this.session.session.status ?? 'lobby';
     const code = this.normalizeCode(this.session.session.code || this.sessionCode);
     if (!code) {
       return;
diff --git a/frontend/src/api/mappers.ts b/frontend/src/api/mappers.ts
index 0cab015..fe7c89d 100644
--- a/frontend/src/api/mappers.ts
+++ b/frontend/src/api/mappers.ts
@@ -195,6 +195,7 @@ function mapSessionDetail(payload: unknown): SessionDetailResponse {
     reveal,
     phase_view_model: {
       status: readString(phase, 'status', 'session_detail.phase_view_model'),
+      current_phase: typeof phase.current_phase === 'string' ? phase.current_phase : undefined,
       round_number: readNumber(phase, 'round_number', 'session_detail.phase_view_model'),
       players_count: readNumber(phase, 'players_count', 'session_detail.phase_view_model'),
       constraints: {
@@ -203,6 +204,19 @@ function mapSessionDetail(payload: unknown): SessionDetailResponse {
         min_players_reached: readBoolean(constraints, 'min_players_reached', 'session_detail.phase_view_model.constraints'),
         max_players_allowed: readBoolean(constraints, 'max_players_allowed', 'session_detail.phase_view_model.constraints')
       },
+      readiness:
+        phase.readiness && typeof phase.readiness === 'object'
+          ? {
+              question_ready:
+                typeof (phase.readiness as Record<string, unknown>).question_ready === 'boolean'
+                  ? ((phase.readiness as Record<string, unknown>).question_ready as boolean)
+                  : undefined,
+              scoreboard_ready:
+                typeof (phase.readiness as Record<string, unknown>).scoreboard_ready === 'boolean'
+                  ? ((phase.readiness as Record<string, unknown>).scoreboard_ready as boolean)
+                  : undefined,
+            }
+          : undefined,
       host: {
         can_start_round: readBoolean(host, 'can_start_round', 'session_detail.phase_view_model.host'),
         can_show_question: readBoolean(host, 'can_show_question', 'session_detail.phase_view_model.host'),
diff --git a/frontend/src/api/types.ts b/frontend/src/api/types.ts
index 5a9a13a..926f28a 100644
--- a/frontend/src/api/types.ts
+++ b/frontend/src/api/types.ts
@@ -32,6 +32,7 @@ export interface SessionRoundQuestion {
 
 export interface PhaseViewModel {
   status: string;
+  current_phase?: string;
   round_number: number;
   players_count: number;
   constraints: {
@@ -40,6 +41,10 @@ export interface PhaseViewModel {
     min_players_reached: boolean;
     max_players_allowed: boolean;
   };
+  readiness?: {
+    question_ready?: boolean;
+    scoreboard_ready?: boolean;
+  };
   host: {
     can_start_round: boolean;
     can_show_question: boolean;