diff --git a/backend/src/main/java/com/goldenchart/controller/BacktestSettingsController.java b/backend/src/main/java/com/goldenchart/controller/BacktestSettingsController.java
index 7d872d9..9546fa7 100644
--- a/backend/src/main/java/com/goldenchart/controller/BacktestSettingsController.java
+++ b/backend/src/main/java/com/goldenchart/controller/BacktestSettingsController.java
@@ -16,14 +16,25 @@ public class BacktestSettingsController {
 
     @GetMapping
     public ResponseEntity<BacktestSettingsDto> get(
+            @RequestHeader(value = "X-User-Id", required = false) String userIdHeader,
             @RequestHeader(value = "X-Device-Id", defaultValue = "default") String deviceId) {
-        return ResponseEntity.ok(service.get(deviceId));
+        return ResponseEntity.ok(service.get(parseUserId(userIdHeader), deviceId));
     }
 
     @PostMapping
     public ResponseEntity<BacktestSettingsDto> save(
+            @RequestHeader(value = "X-User-Id", required = false) String userIdHeader,
             @RequestHeader(value = "X-Device-Id", defaultValue = "default") String deviceId,
             @RequestBody BacktestSettingsDto dto) {
-        return ResponseEntity.ok(service.save(deviceId, dto));
+        return ResponseEntity.ok(service.save(parseUserId(userIdHeader), deviceId, dto));
+    }
+
+    private Long parseUserId(String header) {
+        if (header == null || header.isBlank()) return null;
+        try {
+            return Long.parseLong(header);
+        } catch (NumberFormatException e) {
+            return null;
+        }
     }
 }
diff --git a/backend/src/main/java/com/goldenchart/entity/GcBacktestSettings.java b/backend/src/main/java/com/goldenchart/entity/GcBacktestSettings.java
index 51b969a..3779cf8 100644
--- a/backend/src/main/java/com/goldenchart/entity/GcBacktestSettings.java
+++ b/backend/src/main/java/com/goldenchart/entity/GcBacktestSettings.java
@@ -22,6 +22,9 @@ public class GcBacktestSettings {
     @Column(name = "device_id", length = 100)
     private String deviceId;
 
+    @Column(name = "user_id")
+    private Long userId;
+
     // ── 자본 설정 ──────────────────────────────────────────────────────────────
     @Column(name = "initial_capital", nullable = false, precision = 20, scale = 2)
     @Builder.Default
diff --git a/backend/src/main/java/com/goldenchart/repository/GcBacktestSettingsRepository.java b/backend/src/main/java/com/goldenchart/repository/GcBacktestSettingsRepository.java
index 0b116f1..f4f409b 100644
--- a/backend/src/main/java/com/goldenchart/repository/GcBacktestSettingsRepository.java
+++ b/backend/src/main/java/com/goldenchart/repository/GcBacktestSettingsRepository.java
@@ -7,4 +7,6 @@ import java.util.Optional;
 
 public interface GcBacktestSettingsRepository extends JpaRepository<GcBacktestSettings, Long> {
     Optional<GcBacktestSettings> findFirstByDeviceIdOrderByUpdatedAtDesc(String deviceId);
+
+    Optional<GcBacktestSettings> findFirstByUserIdOrderByUpdatedAtDesc(Long userId);
 }
diff --git a/backend/src/main/java/com/goldenchart/service/BacktestSettingsService.java b/backend/src/main/java/com/goldenchart/service/BacktestSettingsService.java
index 3dac6a3..2774c29 100644
--- a/backend/src/main/java/com/goldenchart/service/BacktestSettingsService.java
+++ b/backend/src/main/java/com/goldenchart/service/BacktestSettingsService.java
@@ -3,32 +3,99 @@ package com.goldenchart.service;
 import com.goldenchart.dto.BacktestSettingsDto;
 import com.goldenchart.entity.GcBacktestSettings;
 import com.goldenchart.repository.GcBacktestSettingsRepository;
+import com.goldenchart.trading.TradingAccess;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.util.Optional;
+
 @Service
 @RequiredArgsConstructor
 public class BacktestSettingsService {
 
     private final GcBacktestSettingsRepository repo;
 
-    /** device_id 기준 설정 조회 — 없으면 기본값 반환 */
+    /** userId 우선, 없으면 deviceId — 레거시 user:{id}·기기별 행 자동 승격 */
     @Transactional(readOnly = true)
-    public BacktestSettingsDto get(String deviceId) {
-        return repo.findFirstByDeviceIdOrderByUpdatedAtDesc(deviceId)
+    public BacktestSettingsDto get(Long userId, String deviceId) {
+        return findEntity(userId, deviceId)
                 .map(this::toDto)
                 .orElseGet(BacktestSettingsDto::new);
     }
 
-    /** upsert — 기존 설정이 있으면 덮어쓰기, 없으면 새 행 삽입 */
-    @Transactional
-    public BacktestSettingsDto save(String deviceId, BacktestSettingsDto dto) {
-        GcBacktestSettings entity = repo
-                .findFirstByDeviceIdOrderByUpdatedAtDesc(deviceId)
-                .orElseGet(GcBacktestSettings::new);
+    /**
+     * 레거시 호출 — scopeKey가 {@code user:{userId}} 이면 userId 조회로 위임.
+     */
+    @Transactional(readOnly = true)
+    public BacktestSettingsDto get(String scopeKey) {
+        if (scopeKey != null && scopeKey.startsWith("user:")) {
+            try {
+                long uid = Long.parseLong(scopeKey.substring(5));
+                return get(uid, null);
+            } catch (NumberFormatException ignored) {
+                /* fall through */
+            }
+        }
+        return get(null, scopeKey);
+    }
 
-        entity.setDeviceId(deviceId);
+    @Transactional
+    public BacktestSettingsDto save(Long userId, String deviceId, BacktestSettingsDto dto) {
+        GcBacktestSettings entity = findOrCreate(userId, deviceId);
+        applyFields(entity, dto, userId, deviceId);
+        return toDto(repo.save(entity));
+    }
+
+    // ── 조회·생성 ─────────────────────────────────────────────────────────────
+
+    private Optional<GcBacktestSettings> findEntity(Long userId, String deviceId) {
+        if (userId != null && userId > 0) {
+            Optional<GcBacktestSettings> byUser = repo.findFirstByUserIdOrderByUpdatedAtDesc(userId);
+            if (byUser.isPresent()) return byUser;
+
+            if (deviceId != null && !deviceId.isBlank()) {
+                Optional<GcBacktestSettings> byDevice = repo.findFirstByDeviceIdOrderByUpdatedAtDesc(deviceId);
+                if (byDevice.isPresent()) {
+                    return Optional.of(promoteToUser(byDevice.get(), userId));
+                }
+            }
+
+            Optional<GcBacktestSettings> legacy = repo.findFirstByDeviceIdOrderByUpdatedAtDesc(
+                    TradingAccess.accountDeviceKey(userId));
+            if (legacy.isPresent()) {
+                return Optional.of(promoteToUser(legacy.get(), userId));
+            }
+            return Optional.empty();
+        }
+        if (deviceId != null && !deviceId.isBlank()) {
+            return repo.findFirstByDeviceIdOrderByUpdatedAtDesc(deviceId);
+        }
+        return Optional.empty();
+    }
+
+    private GcBacktestSettings findOrCreate(Long userId, String deviceId) {
+        return findEntity(userId, deviceId)
+                .orElseGet(() -> GcBacktestSettings.builder()
+                        .userId(userId != null && userId > 0 ? userId : null)
+                        .deviceId(deviceId)
+                        .build());
+    }
+
+    /** 기기별 행을 로그인 사용자 소유로 1회 승격 (다른 PC와 공유) */
+    private GcBacktestSettings promoteToUser(GcBacktestSettings entity, Long userId) {
+        entity.setUserId(userId);
+        return repo.save(entity);
+    }
+
+    private void applyFields(GcBacktestSettings entity, BacktestSettingsDto dto,
+                           Long userId, String deviceId) {
+        if (userId != null && userId > 0) {
+            entity.setUserId(userId);
+        }
+        if (deviceId != null && !deviceId.isBlank()) {
+            entity.setDeviceId(deviceId);
+        }
         entity.setInitialCapital(dto.getInitialCapital());
         entity.setCommissionType(dto.getCommissionType());
         entity.setCommissionRate(dto.getCommissionRate());
@@ -58,8 +125,6 @@ public class BacktestSettingsService {
                 "SCAN_SIGNALS".equals(dto.getTradeExecutionMode())
                         ? "SCAN_SIGNALS"
                         : "BACKTEST_ENGINE");
-
-        return toDto(repo.save(entity));
     }
 
     // ── 변환 헬퍼 ─────────────────────────────────────────────────────────────
diff --git a/backend/src/main/java/com/goldenchart/service/LiveRiskMonitorService.java b/backend/src/main/java/com/goldenchart/service/LiveRiskMonitorService.java
index 84929b5..f6a5175 100644
--- a/backend/src/main/java/com/goldenchart/service/LiveRiskMonitorService.java
+++ b/backend/src/main/java/com/goldenchart/service/LiveRiskMonitorService.java
@@ -95,7 +95,7 @@ public class LiveRiskMonitorService {
             GcAppSettings app = appSettingsRepo.findByUserId(userId).orElse(null);
             if (app == null) continue;
 
-            BacktestSettingsDto risk = backtestSettingsService.get(cacheKey);
+            BacktestSettingsDto risk = backtestSettingsService.get(userId, null);
             double avg = pos[1];
             double pnlPct = (tradePrice - avg) / avg * 100.0;
 
diff --git a/backend/src/main/java/com/goldenchart/service/LiveStrategyEvaluator.java b/backend/src/main/java/com/goldenchart/service/LiveStrategyEvaluator.java
index 56fbed3..c32d840 100644
--- a/backend/src/main/java/com/goldenchart/service/LiveStrategyEvaluator.java
+++ b/backend/src/main/java/com/goldenchart/service/LiveStrategyEvaluator.java
@@ -389,11 +389,8 @@ public class LiveStrategyEvaluator {
             if (!globalLive && Boolean.TRUE.equals(s.getIsLiveCheck())) {
                 return s.getPositionMode() != null ? s.getPositionMode() : "LONG_ONLY";
             }
-            String deviceKey = s.getUserId() != null
-                    ? TradingAccess.accountDeviceKey(s.getUserId())
-                    : s.getDeviceId();
-            if (deviceKey != null && !deviceKey.isBlank()) {
-                BacktestSettingsDto bt = backtestSettingsService.get(deviceKey);
+            if (s.getUserId() != null || (s.getDeviceId() != null && !s.getDeviceId().isBlank())) {
+                BacktestSettingsDto bt = backtestSettingsService.get(s.getUserId(), s.getDeviceId());
                 if (bt.getPositionMode() != null) {
                     return "SIGNAL_ONLY".equals(bt.getPositionMode()) ? "SIGNAL_ONLY" : "LONG_ONLY";
                 }
diff --git a/backend/src/main/java/com/goldenchart/trading/pipeline/RealtimePositionMonitor.java b/backend/src/main/java/com/goldenchart/trading/pipeline/RealtimePositionMonitor.java
index 3cea2f0..1d6ff8f 100644
--- a/backend/src/main/java/com/goldenchart/trading/pipeline/RealtimePositionMonitor.java
+++ b/backend/src/main/java/com/goldenchart/trading/pipeline/RealtimePositionMonitor.java
@@ -75,7 +75,7 @@ public class RealtimePositionMonitor {
             double avg = pos.getAvgPrice().doubleValue();
             if (avg <= 0) continue;
 
-            BacktestSettingsDto risk = backtestSettingsService.get(TradingAccess.accountDeviceKey(userId));
+            BacktestSettingsDto risk = backtestSettingsService.get(userId, null);
             double pnlPct = (tradePrice - avg) / avg * 100.0;
 
             if (Boolean.TRUE.equals(risk.getStopLossEnabled())
diff --git a/backend/src/main/resources/db/migration/V70__backtest_settings_user_id.sql b/backend/src/main/resources/db/migration/V70__backtest_settings_user_id.sql
new file mode 100644
index 0000000..8e99659
--- /dev/null
+++ b/backend/src/main/resources/db/migration/V70__backtest_settings_user_id.sql
@@ -0,0 +1,11 @@
+-- 백테스트 설정: 로그인 사용자(user_id) 단위 공유 (기존 device_id 전용 → AppSettings와 동일 패턴)
+ALTER TABLE gc_backtest_settings
+    ADD COLUMN user_id BIGINT NULL AFTER device_id;
+
+-- 레거시 user:{id} device_id 행 → user_id 승격
+UPDATE gc_backtest_settings
+SET user_id = CAST(SUBSTRING(device_id, 6) AS UNSIGNED)
+WHERE device_id LIKE 'user:%'
+  AND user_id IS NULL;
+
+CREATE INDEX idx_gc_backtest_settings_user_id ON gc_backtest_settings (user_id);
diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index f3f85e6..d39123d 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -28,8 +28,10 @@ import { syncDocumentTheme } from './utils/documentTheme';
 import {
   loadLocalTheme,
   migrateDbThemeToLocalIfNeeded,
+  resolveThemeForSession,
   saveLocalTheme,
 } from './utils/localThemeStorage';
+import { hasRegisteredUser } from './utils/backendApi';
 import { useMenuPermissions, invalidateMenuPermissionsCache } from './hooks/useMenuPermissions';
 import { firstAllowedTopMenu, normalizeRole, type SettingsCategoryId } from './utils/permissions';
 import { clearAdminUnlock } from './utils/adminUnlock';
@@ -694,9 +696,12 @@ function App() {
     setTheme(t => {
       const next: Theme = t === 'dark' ? 'blue' : t === 'blue' ? 'light' : 'dark';
       saveLocalTheme(next);
+      if (hasRegisteredUser()) {
+        saveAppDef({ defaultTheme: next });
+      }
       return next;
     });
-  }, []);
+  }, [saveAppDef]);
 
   useEffect(() => {
     syncDocumentTheme(theme);
@@ -704,7 +709,12 @@ function App() {
 
   useEffect(() => {
     if (!appSettingsLoaded) return;
-    setTheme(migrateDbThemeToLocalIfNeeded(getAppSettingsCache().defaultTheme));
+    const dbTheme = getAppSettingsCache().defaultTheme;
+    if (hasRegisteredUser()) {
+      setTheme(resolveThemeForSession(dbTheme, true));
+    } else {
+      setTheme(migrateDbThemeToLocalIfNeeded(dbTheme));
+    }
   }, [appSettingsLoaded]);
 
   const openNotificationsPage = useCallback(
diff --git a/frontend/src/chart/useChartWorkspace.ts b/frontend/src/chart/useChartWorkspace.ts
index c2143c9..b1bd3e2 100644
--- a/frontend/src/chart/useChartWorkspace.ts
+++ b/frontend/src/chart/useChartWorkspace.ts
@@ -1,4 +1,4 @@
-import { useState, useEffect, useLayoutEffect, useCallback, useRef, useMemo } from 'react';
+import { useState, useEffect, useLayoutEffect, useCallback, useRef, useMemo, type SetStateAction } from 'react';
 import DrawingToolbar from '../components/DrawingToolbar';
 import BottomBar from '../components/BottomBar';
 import TradingChart from '../components/TradingChart';
@@ -90,7 +90,8 @@ import {
 import {
   sortIndicatorsByTypeOrder,
 } from '../utils/indicatorListOrder';
-import { getAppSettingsCache } from '../hooks/useAppSettings';
+import { getAppSettingsCache, isAppSettingsCacheLoaded, subscribeAppSettings } from '../hooks/useAppSettings';
+import { loadMagnetMode, saveMagnetMode, type MagnetMode } from '../utils/chartMagnetModeStorage';
 import type { AppSettingsDto } from '../utils/backendApi';
 import MarketPanel from '../components/MarketPanel';
 import { type MenuPage } from '../components/TopMenuBar';
@@ -245,7 +246,22 @@ export function useChartWorkspace({
   const [drawingsLocked,    setDrawingsLocked]    = useState(false);
   const [drawingsVisible,   setDrawingsVisible]   = useState(true);
   const [indicatorsVisible, setIndicatorsVisible] = useState(true);
-  const [magnetMode,        setMagnetMode]        = useState<'off'|'weak'|'strong'>('off');
+  const [magnetMode,        setMagnetModeState] = useState<MagnetMode>('off');
+  const setMagnetMode = useCallback((value: SetStateAction<MagnetMode>) => {
+    setMagnetModeState(prev => {
+      const next = typeof value === 'function' ? value(prev) : value;
+      if (isAppSettingsCacheLoaded()) saveMagnetMode(next);
+      return next;
+    });
+  }, []);
+
+  useEffect(() => {
+    const syncMagnet = () => {
+      if (isAppSettingsCacheLoaded()) setMagnetModeState(loadMagnetMode());
+    };
+    syncMagnet();
+    return subscribeAppSettings(syncMagnet);
+  }, []);
   const [snapToIndicator,   setSnapToIndicator]   = useState(false);
   const [keepLockedOnDelete,setKeepLockedOnDelete]= useState(false);
   const [legend,      setLegend]      = useState<LegendData | null>(null);
diff --git a/frontend/src/hooks/useAppSettings.ts b/frontend/src/hooks/useAppSettings.ts
index 741e1e3..7860a42 100644
--- a/frontend/src/hooks/useAppSettings.ts
+++ b/frontend/src/hooks/useAppSettings.ts
@@ -7,7 +7,7 @@
  *  - defaultSymbol    : 기본 종목 (DEFAULT_STATE.symbol)
  *  - defaultTimeframe : 기본 타임프레임 (DEFAULT_STATE.timeframe)
  *  - defaultChartType : 기본 차트 타입
- *  - (테마는 DB 미사용 — localStorage, see localThemeStorage)
+ *  - defaultTheme     : 기본 테마 (로그인 시 DB 공유, 게스트는 localStorage)
  *  - defaultLogScale  : 기본 로그 스케일
  *  - defaultLayoutId  : 기본 레이아웃 ID
  *  - mainChartStyle   : 캔들 색상 (DEFAULT_MAIN_CHART_STYLE)
@@ -20,7 +20,7 @@
  * // 기본 심볼 사용
  * const symbol = settings.defaultSymbol ?? 'KRW-BTC';
  *
- * // 테마 변경 시 saveLocalTheme() (App.tsx)
+ * // 테마 변경 시 saveAppDef({ defaultTheme }) + saveLocalTheme() (App.tsx)
  * ```
  */
 
@@ -65,7 +65,7 @@ import {
 } from '../types/chartPaneSeparator';
 import { migrateLocalStorageToUiPreferences } from '../utils/uiPreferencesMigrate';
 import { reconcilePendingUiPreferencesOnLoad } from '../utils/uiPreferencesDb';
-import { loadLocalTheme } from '../utils/localThemeStorage';
+import { loadLocalTheme, resolveThemeForSession } from '../utils/localThemeStorage';
 
 // 전역 캐시 — 여러 컴포넌트에서 공유하여 중복 요청 방지
 let _cache: AppSettingsDto | null = null;
@@ -127,6 +127,21 @@ function ensureLoaded(): Promise<AppSettingsDto> {
         }
       }
     }
+    if (hasRegisteredUser() && _cache) {
+      const local = loadLocalTheme();
+      const dbTheme = _cache.defaultTheme;
+      const dbIsDefault = !dbTheme || dbTheme === 'dark';
+      if (dbIsDefault && local !== 'dark') {
+        try {
+          const saved = await saveAppSettings({ defaultTheme: local });
+          if (generation === _loadGeneration && saved) {
+            _cache = { ..._cache, ...saved, defaultTheme: local };
+          }
+        } catch (e) {
+          console.warn('[useAppSettings] 테마 localStorage→DB 이전 실패:', e);
+        }
+      }
+    }
     if (hasRegisteredUser()) {
       try {
         await loadStrategies();
@@ -161,11 +176,12 @@ export function reloadAppSettingsCache(): Promise<AppSettingsDto> {
 
 /** DB 또는 fallback 기본값 접근 헬퍼 */
 export function resolveAppDefaults(s: AppSettingsDto) {
+  const accountTheme = resolveThemeForSession(s.defaultTheme, hasRegisteredUser());
   return {
     symbol:        (s.defaultSymbol    ?? 'KRW-BTC')    as string,
     timeframe:     (s.defaultTimeframe ?? '1D')          as Timeframe,
     chartType:     (s.defaultChartType ?? 'candlestick') as ChartType,
-    theme:         loadLocalTheme(),
+    theme:         accountTheme,
     logScale:      s.defaultLogScale   ?? false,
     layoutId:      s.defaultLayoutId   ?? '1',
     mainChartStyle:(s.mainChartStyle as unknown as MainChartStyle | null) ?? DEFAULT_MAIN_CHART_STYLE,
@@ -184,7 +200,7 @@ export function resolveAppDefaults(s: AppSettingsDto) {
     ),
     chartPaneSeparator:     resolveChartPaneSeparatorOptions(
       s.chartPaneSeparator as Partial<ChartPaneSeparatorOptions> | null | undefined,
-      loadLocalTheme(),
+      accountTheme,
     ),
     tradeAlertPopup:  s.tradeAlertPopup  ?? true,
     tradeAlertSoundEnabled: s.tradeAlertSoundEnabled ?? true,
@@ -288,9 +304,7 @@ export function useAppSettings(sessionKey = 0) {
    * 낙관적 업데이트 — DB 저장 실패해도 UI 는 즉시 반영.
    */
   const save = useCallback((patch: AppSettingsDto) => {
-    const { defaultTheme: _omitTheme, ...patchWithoutTheme } = patch;
-    const apiPatch = 'defaultTheme' in patch ? patchWithoutTheme : patch;
-    const merged = { ...(_cache ?? {}), ...apiPatch };
+    const merged = { ...(_cache ?? {}), ...patch };
     _cache = merged;
     notifyAppSettingsListeners();
     setSettings(merged);
@@ -303,7 +317,7 @@ export function useAppSettings(sessionKey = 0) {
     if (patch.tradeAlertTimeFormat != null) {
       setTradeAlertTimeFormat(normalizeChartTimeFormat(patch.tradeAlertTimeFormat));
     }
-    saveAppSettings(apiPatch).then(updated => {
+    saveAppSettings(patch).then(updated => {
       if (updated) {
         _cache = { ...(_cache ?? {}), ...updated };
         notifyAppSettingsListeners();
diff --git a/frontend/src/types/uiPreferences.ts b/frontend/src/types/uiPreferences.ts
index f07e55d..770c466 100644
--- a/frontend/src/types/uiPreferences.ts
+++ b/frontend/src/types/uiPreferences.ts
@@ -28,6 +28,8 @@ export interface UiPreferences {
   chart?: {
     alertPrices?: number[];
     legacyIndicators?: IndicatorConfig[];
+    /** 차트 자석 모드 — 설정 화면·툴바 공유 */
+    magnetMode?: 'off' | 'weak' | 'strong';
   };
   panels?: Record<string, number | boolean | string>;
   virtual?: {
diff --git a/frontend/src/utils/chartMagnetModeStorage.ts b/frontend/src/utils/chartMagnetModeStorage.ts
new file mode 100644
index 0000000..b670ac6
--- /dev/null
+++ b/frontend/src/utils/chartMagnetModeStorage.ts
@@ -0,0 +1,16 @@
+import { getUiPreferences, patchUiPreferences } from './uiPreferencesDb';
+
+export type MagnetMode = 'off' | 'weak' | 'strong';
+
+function normalizeMagnetMode(v: unknown): MagnetMode {
+  return v === 'weak' || v === 'strong' ? v : 'off';
+}
+
+/** DB ui_preferences.chart.magnetMode */
+export function loadMagnetMode(): MagnetMode {
+  return normalizeMagnetMode(getUiPreferences().chart?.magnetMode);
+}
+
+export function saveMagnetMode(mode: MagnetMode): void {
+  patchUiPreferences({ chart: { magnetMode: mode } });
+}
diff --git a/frontend/src/utils/localThemeStorage.ts b/frontend/src/utils/localThemeStorage.ts
index 63abb4a..aabfb52 100644
--- a/frontend/src/utils/localThemeStorage.ts
+++ b/frontend/src/utils/localThemeStorage.ts
@@ -8,7 +8,7 @@ function isTheme(v: unknown): v is Theme {
   return typeof v === 'string' && (VALID as readonly string[]).includes(v);
 }
 
-/** 이 브라우저(기기)에 저장된 UI 테마. 계정·DB와 무관 */
+/** 이 브라우저(기기)에 저장된 UI 테마 — 게스트·오프라인 폴백 */
 export function loadLocalTheme(): Theme {
   try {
     const raw = localStorage.getItem(STORAGE_KEY);
@@ -27,7 +27,13 @@ export function saveLocalTheme(theme: Theme): void {
   }
 }
 
-/** localStorage에 없을 때만 DB defaultTheme을 이 기기에 1회 복사 */
+/** 로그인 사용자: DB defaultTheme 우선. 게스트: localStorage */
+export function resolveThemeForSession(dbTheme: string | undefined, useAccountScope: boolean): Theme {
+  if (useAccountScope && isTheme(dbTheme)) return dbTheme;
+  return loadLocalTheme();
+}
+
+/** localStorage에 없을 때만 DB defaultTheme을 이 기기에 1회 복사 (게스트) */
 export function migrateDbThemeToLocalIfNeeded(dbTheme: string | undefined): Theme {
   try {
     const existing = localStorage.getItem(STORAGE_KEY);
@@ -39,3 +45,5 @@ export function migrateDbThemeToLocalIfNeeded(dbTheme: string | undefined): Them
   saveLocalTheme(theme);
   return theme;
 }
+
+export { isTheme };