diff --git a/app/game-frontend/e2e/mainNavigation.spec.ts b/app/game-frontend/e2e/mainNavigation.spec.ts
index 34c3b21a..1aa67dbd 100644
--- a/app/game-frontend/e2e/mainNavigation.spec.ts
+++ b/app/game-frontend/e2e/mainNavigation.spec.ts
@@ -3083,6 +3083,51 @@ test('main cards and command input stay inside their Ref-sized grid slots', asyn
     await captureProgress('mobile-500');
 });
 
+test('main layout and map use the same mobile/desktop boundary', async ({ page }, testInfo) => {
+    const state: NavigationFixture = {
+        officerLevel: 5,
+        permission: 2,
+        nationLevel: 3,
+        stage: 6,
+        npcMode: 1,
+        scenarioTitle: '모바일 검증 시나리오',
+        lastExecuted: null,
+        latestVote: null,
+        generalMeCalls: 0,
+        operations: [],
+        validMapImages: true,
+    };
+    await installFixture(page, state);
+    await page.setViewportSize({ width: 1000, height: 900 });
+    await waitForMain(page);
+    await expect(page.locator('.layout-desktop [data-main-target="map"] .map-area')).toBeVisible();
+    expect(
+        await page
+            .locator('.layout-desktop [data-main-target="map"] .map-area')
+            .evaluate((element) => element.getBoundingClientRect().width)
+    ).toBe(700);
+    await page.screenshot({ path: testInfo.outputPath('screen-mode-desktop-1000.png'), fullPage: true });
+
+    await page.setViewportSize({ width: 940, height: 900 });
+    await expect(page.locator('.layout-desktop')).toBeVisible();
+    await expect(page.locator('.layout-desktop [data-main-target="map"] .map-area')).toBeVisible();
+    expect(
+        await page
+            .locator('.layout-desktop [data-main-target="map"] .map-area')
+            .evaluate((element) => element.getBoundingClientRect().width)
+    ).toBeGreaterThan(500);
+
+    await page.setViewportSize({ width: 939, height: 900 });
+    await expect(page.locator('.layout-mobile')).toBeVisible();
+    await expect(page.locator('.layout-mobile [data-main-target="map"] .map-area')).toBeVisible();
+    expect(
+        await page
+            .locator('.layout-mobile [data-main-target="map"] .map-area')
+            .evaluate((element) => element.getBoundingClientRect().width)
+    ).toBe(500);
+    await page.screenshot({ path: testInfo.outputPath('screen-mode-mobile-939.png'), fullPage: true });
+});
+
 test('the 939/940 boundary switches to the Ref-style 500px single document', async ({ page }) => {
     const state: NavigationFixture = {
         officerLevel: 5,
@@ -3630,12 +3675,20 @@ test('automatic screen mode switches wide mobile screens to the 1000px layout at
             npcMode: 1,
             generalMeCalls: 0,
             operations: [],
+            validMapImages: true,
         };
         await installFixture(mobilePage, state);
         await waitForMain(mobilePage);
 
         const expectedWideLayout = deviceWidth >= 700;
         await expect(mobilePage.locator(expectedWideLayout ? '.layout-desktop' : '.layout-mobile')).toBeVisible();
+        const activeMap = mobilePage.locator(
+            `${expectedWideLayout ? '.layout-desktop' : '.layout-mobile'} [data-main-target="map"] .map-area`
+        );
+        await expect(activeMap).toBeVisible();
+        expect(await activeMap.evaluate((element) => element.getBoundingClientRect().width)).toBe(
+            expectedWideLayout ? 700 : 500
+        );
         expect(
             await mobilePage.evaluate(() => document.querySelector<HTMLMetaElement>('meta[name="viewport"]')?.content)
         ).toBe(expectedWideLayout ? 'width=1000' : 'width=device-width, initial-scale=1');
@@ -3664,6 +3717,10 @@ test('automatic screen mode switches wide mobile screens to the 1000px layout at
                 document.dispatchEvent(new CustomEvent('tryChangeScreenMode'));
             });
             await expect(mobilePage.locator('.layout-mobile')).toBeVisible();
+            await expect(mobilePage.locator('.layout-mobile [data-main-target="map"] .map-area')).toHaveCSS(
+                'width',
+                '500px'
+            );
             expect(
                 await mobilePage.evaluate(
                     () => document.querySelector<HTMLMetaElement>('meta[name="viewport"]')?.content
@@ -3686,6 +3743,10 @@ test('automatic screen mode switches wide mobile screens to the 1000px layout at
                 document.dispatchEvent(new CustomEvent('tryChangeScreenMode'));
             });
             await expect(mobilePage.locator('.layout-desktop')).toBeVisible();
+            await expect(mobilePage.locator('.layout-desktop [data-main-target="map"] .map-area')).toHaveCSS(
+                'width',
+                '700px'
+            );
             expect(
                 await mobilePage.evaluate(
                     () => document.querySelector<HTMLMetaElement>('meta[name="viewport"]')?.content
diff --git a/app/game-frontend/src/components/main/MapViewer.vue b/app/game-frontend/src/components/main/MapViewer.vue
index d757caee..5de4e844 100644
--- a/app/game-frontend/src/components/main/MapViewer.vue
+++ b/app/game-frontend/src/components/main/MapViewer.vue
@@ -9,6 +9,7 @@ import { useMapViewerStore } from '../../stores/mapViewer';
 import { buildAssetUrl } from '../../utils/mapAssets';
 import { resolveMapBackgroundPath, resolveMapSeason, resolveNextMapSeason } from '../../utils/mapBackground';
 import { configuredGameAssetUrl } from '../../utils/imageAssets';
+import { SCREEN_MODE_DESKTOP_MEDIA_QUERY } from '../../utils/screenModeViewport';
 
 interface MapSummary {
     year: number;
@@ -133,7 +134,7 @@ const preloadDecodedImage = (url: string): Promise<void> => {
     return pending;
 };
 
-const isWide = useMediaQuery('(min-width: 1024px)');
+const isWide = useMediaQuery(SCREEN_MODE_DESKTOP_MEDIA_QUERY);
 const mapStore = useMapViewerStore();
 const {
     showCityName,
diff --git a/app/game-frontend/src/utils/screenModeViewport.ts b/app/game-frontend/src/utils/screenModeViewport.ts
index 260fec55..d72978ba 100644
--- a/app/game-frontend/src/utils/screenModeViewport.ts
+++ b/app/game-frontend/src/utils/screenModeViewport.ts
@@ -1,5 +1,8 @@
 export const SCREEN_MODE_KEY = 'sam.screenMode';
 export const SCREEN_MODE_CHANGE_EVENT = 'tryChangeScreenMode';
+export const SCREEN_MODE_DESKTOP_MIN_WIDTH = 940;
+export const SCREEN_MODE_DESKTOP_MEDIA_QUERY = `(min-width: ${SCREEN_MODE_DESKTOP_MIN_WIDTH}px)`;
+export const SCREEN_MODE_MOBILE_MEDIA_QUERY = `(max-width: ${SCREEN_MODE_DESKTOP_MIN_WIDTH - 0.02}px)`;
 
 export type ScreenMode = 'auto' | '500px' | '1000px';
 
diff --git a/app/game-frontend/src/views/MainView.vue b/app/game-frontend/src/views/MainView.vue
index 0411673b..4548993e 100644
--- a/app/game-frontend/src/views/MainView.vue
+++ b/app/game-frontend/src/views/MainView.vue
@@ -37,11 +37,12 @@ import {
     MOBILE_MAIN_PANEL_ORDER_STORAGE_KEY,
     type MobileMainPanelId,
 } from '../utils/mobileMainPanelOrder';
+import { SCREEN_MODE_MOBILE_MEDIA_QUERY } from '../utils/screenModeViewport';
 
 const session = useSessionStore();
 const dashboard = useMainDashboardStore();
 const { info: showInfoToast } = useGameFeedback();
-const isMobile = useMediaQuery('(max-width: 939.98px)');
+const isMobile = useMediaQuery(SCREEN_MODE_MOBILE_MEDIA_QUERY);
 
 const npcMode = ref(0);
 const globalNavigation = ref<MainNavigationEntry[]>(defaultGlobalNavigation);
diff --git a/app/game-frontend/test/screenModeViewport.test.ts b/app/game-frontend/test/screenModeViewport.test.ts
index 45e426a9..0ac60f72 100644
--- a/app/game-frontend/test/screenModeViewport.test.ts
+++ b/app/game-frontend/test/screenModeViewport.test.ts
@@ -5,8 +5,17 @@ import {
     normalizeScreenMode,
     resolveAutoViewportContent,
     resolveViewportContent,
+    SCREEN_MODE_DESKTOP_MEDIA_QUERY,
+    SCREEN_MODE_DESKTOP_MIN_WIDTH,
+    SCREEN_MODE_MOBILE_MEDIA_QUERY,
 } from '../src/utils/screenModeViewport.ts';
 
+void test('main and map layouts share one 939/940 screen-mode boundary', () => {
+    assert.equal(SCREEN_MODE_DESKTOP_MIN_WIDTH, 940);
+    assert.equal(SCREEN_MODE_DESKTOP_MEDIA_QUERY, '(min-width: 940px)');
+    assert.equal(SCREEN_MODE_MOBILE_MEDIA_QUERY, '(max-width: 939.98px)');
+});
+
 void test('automatic mode follows the Ref physical-screen thresholds', () => {
     assert.equal(resolveAutoViewportContent({ deviceWidth: 390, viewportHeight: 844 }), 'width=500');
     assert.equal(