diff --git a/apps/web/e2e/arcade-modal-session.spec.ts b/apps/web/e2e/arcade-modal-session.spec.ts
new file mode 100644
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+++ b/apps/web/e2e/arcade-modal-session.spec.ts
@@ -0,0 +1,319 @@
+import { test, expect } from '@playwright/test'
+
+/**
+ * Arcade Modal Session E2E Tests
+ *
+ * These tests verify that the arcade modal session system works correctly:
+ * - Users are locked into games once they start
+ * - Automatic redirects to active games
+ * - Player modification is blocked during games
+ * - "Return to Arcade" button properly ends sessions
+ */
+
+test.describe('Arcade Modal Session - Redirects', () => {
+  test.beforeEach(async ({ page }) => {
+    // Clear arcade session before each test
+    await page.goto('/arcade')
+    await page.waitForLoadState('networkidle')
+
+    // Click "Return to Arcade" button if it exists (to clear any existing session)
+    const returnButton = page.locator('button:has-text("Return to Arcade")')
+    if (await returnButton.isVisible({ timeout: 1000 }).catch(() => false)) {
+      await returnButton.click()
+      await page.waitForLoadState('networkidle')
+    }
+  })
+
+  test('should stay on arcade lobby when no active session', async ({ page }) => {
+    await page.goto('/arcade')
+    await page.waitForLoadState('networkidle')
+
+    // Should see "Champion Arena" title
+    const title = page.locator('h1:has-text("Champion Arena")')
+    await expect(title).toBeVisible()
+
+    // Should be able to select players
+    const playerSection = page.locator('text=/Player|Select|Add/i')
+    await expect(playerSection.first()).toBeVisible()
+  })
+
+  test('should redirect from arcade to active game when session exists', async ({ page }) => {
+    // Start a game to create a session
+    await page.goto('/arcade')
+    await page.waitForLoadState('networkidle')
+
+    // Find and click a player card to activate
+    const playerCard = page.locator('[data-testid="player-card"]').first()
+    if (await playerCard.isVisible({ timeout: 2000 }).catch(() => false)) {
+      await playerCard.click()
+      await page.waitForTimeout(500)
+    }
+
+    // Navigate to matching game to create session
+    await page.goto('/arcade/matching')
+    await page.waitForLoadState('networkidle')
+
+    // Start the game (click Start button if visible)
+    const startButton = page.locator('button:has-text("Start")')
+    if (await startButton.isVisible({ timeout: 2000 }).catch(() => false)) {
+      await startButton.click()
+      await page.waitForTimeout(1000)
+    }
+
+    // Try to navigate back to arcade lobby
+    await page.goto('/arcade')
+    await page.waitForTimeout(2000) // Give time for redirect
+
+    // Should be redirected back to the game
+    await expect(page).toHaveURL(/\/arcade\/matching/)
+    const gameTitle = page.locator('h1:has-text("Memory Pairs")')
+    await expect(gameTitle).toBeVisible()
+  })
+
+  test('should redirect to correct game when navigating to wrong game', async ({ page }) => {
+    // Create a session with matching game
+    await page.goto('/arcade')
+    await page.waitForLoadState('networkidle')
+
+    // Activate a player
+    const addPlayerButton = page.locator('button:has-text("Add Player"), button:has-text("+")')
+    if (await addPlayerButton.first().isVisible({ timeout: 2000 }).catch(() => false)) {
+      await addPlayerButton.first().click()
+      await page.waitForTimeout(500)
+    }
+
+    // Go to matching game
+    await page.goto('/arcade/matching')
+    await page.waitForLoadState('networkidle')
+
+    // Start game if needed
+    const startButton = page.locator('button:has-text("Start")')
+    if (await startButton.isVisible({ timeout: 2000 }).catch(() => false)) {
+      await startButton.click()
+      await page.waitForTimeout(1000)
+    }
+
+    // Try to navigate to a different game
+    await page.goto('/arcade/memory-quiz')
+    await page.waitForTimeout(2000) // Give time for redirect
+
+    // Should be redirected back to matching
+    await expect(page).toHaveURL(/\/arcade\/matching/)
+  })
+
+  test('should NOT redirect when on correct game page', async ({ page }) => {
+    // Navigate to matching game
+    await page.goto('/arcade/matching')
+    await page.waitForLoadState('networkidle')
+
+    // Should stay on matching page
+    await expect(page).toHaveURL(/\/arcade\/matching/)
+    const gameTitle = page.locator('h1:has-text("Memory Pairs")')
+    await expect(gameTitle).toBeVisible()
+  })
+})
+
+test.describe('Arcade Modal Session - Player Modification Blocking', () => {
+  test.beforeEach(async ({ page }) => {
+    // Clear session
+    await page.goto('/arcade')
+    await page.waitForLoadState('networkidle')
+
+    const returnButton = page.locator('button:has-text("Return to Arcade")')
+    if (await returnButton.isVisible({ timeout: 1000 }).catch(() => false)) {
+      await returnButton.click()
+      await page.waitForLoadState('networkidle')
+    }
+  })
+
+  test('should allow player modification in arcade lobby with no session', async ({ page }) => {
+    await page.goto('/arcade')
+    await page.waitForLoadState('networkidle')
+
+    // Look for add player button (should be enabled)
+    const addPlayerButton = page.locator('button:has-text("Add Player"), button:has-text("+")')
+    const firstButton = addPlayerButton.first()
+
+    if (await firstButton.isVisible({ timeout: 2000 }).catch(() => false)) {
+      // Should be clickable
+      await expect(firstButton).toBeEnabled()
+
+      // Try to click it
+      await firstButton.click()
+      await page.waitForTimeout(500)
+
+      // Should see player added
+      const activePlayer = page.locator('[data-testid="active-player"]')
+      await expect(activePlayer.first()).toBeVisible({ timeout: 3000 })
+    }
+  })
+
+  test('should block player modification during active game', async ({ page }) => {
+    // Start a game
+    await page.goto('/arcade/matching')
+    await page.waitForLoadState('networkidle')
+
+    // Start game
+    const startButton = page.locator('button:has-text("Start")')
+    if (await startButton.isVisible({ timeout: 2000 }).catch(() => false)) {
+      await startButton.click()
+      await page.waitForTimeout(1000)
+    }
+
+    // Look for player modification controls
+    // They should be disabled or have reduced opacity
+    const playerControls = page.locator('[data-testid="player-controls"], .player-list')
+    if (await playerControls.isVisible({ timeout: 1000 }).catch(() => false)) {
+      // Check if controls have pointer-events: none or low opacity
+      const opacity = await playerControls.evaluate((el) => {
+        return window.getComputedStyle(el).opacity
+      })
+
+      // If controls are visible, they should be dimmed (opacity < 1)
+      if (parseFloat(opacity) < 1) {
+        expect(parseFloat(opacity)).toBeLessThan(1)
+      }
+    }
+
+    // "Add Player" button should not be visible during game
+    const addPlayerButton = page.locator('button:has-text("Add Player")')
+    if (await addPlayerButton.isVisible({ timeout: 500 }).catch(() => false)) {
+      // If visible, should be disabled
+      const isDisabled = await addPlayerButton.isDisabled()
+      expect(isDisabled).toBe(true)
+    }
+  })
+
+  test('should show "Return to Arcade" button during game', async ({ page }) => {
+    // Start a game
+    await page.goto('/arcade/matching')
+    await page.waitForLoadState('networkidle')
+
+    // Look for "Return to Arcade" button
+    const returnButton = page.locator('button:has-text("Return to Arcade")')
+
+    // During game setup, might see "Setup" button instead
+    const setupButton = page.locator('button:has-text("Setup")')
+
+    // One of these should be visible
+    const hasReturnButton = await returnButton.isVisible({ timeout: 2000 }).catch(() => false)
+    const hasSetupButton = await setupButton.isVisible({ timeout: 2000 }).catch(() => false)
+
+    expect(hasReturnButton || hasSetupButton).toBe(true)
+  })
+
+  test('should NOT show "Setup" button in arcade lobby with no session', async ({ page }) => {
+    await page.goto('/arcade')
+    await page.waitForLoadState('networkidle')
+
+    // Should NOT see "Return to Arcade" or "Setup" button in lobby
+    const returnButton = page.locator('button:has-text("Return to Arcade")')
+    const setupButton = page.locator('button:has-text("Setup")')
+
+    const hasReturnButton = await returnButton.isVisible({ timeout: 1000 }).catch(() => false)
+    const hasSetupButton = await setupButton.isVisible({ timeout: 1000 }).catch(() => false)
+
+    // Neither should be visible in empty lobby
+    expect(hasReturnButton).toBe(false)
+    expect(hasSetupButton).toBe(false)
+  })
+})
+
+test.describe('Arcade Modal Session - Return to Arcade Button', () => {
+  test.beforeEach(async ({ page }) => {
+    // Clear session
+    await page.goto('/arcade')
+    await page.waitForLoadState('networkidle')
+  })
+
+  test('should end session and return to arcade when clicking "Return to Arcade"', async ({ page }) => {
+    // Start a game
+    await page.goto('/arcade/matching')
+    await page.waitForLoadState('networkidle')
+
+    // Start game if needed
+    const startButton = page.locator('button:has-text("Start")')
+    if (await startButton.isVisible({ timeout: 2000 }).catch(() => false)) {
+      await startButton.click()
+      await page.waitForTimeout(1000)
+    }
+
+    // Find and click "Return to Arcade" button
+    const returnButton = page.locator('button:has-text("Return to Arcade")')
+    if (await returnButton.isVisible({ timeout: 2000 }).catch(() => false)) {
+      await returnButton.click()
+      await page.waitForTimeout(1000)
+
+      // Should be redirected to arcade lobby
+      await expect(page).toHaveURL(/\/arcade\/?$/)
+
+      // Should see arcade lobby title
+      const title = page.locator('h1:has-text("Champion Arena")')
+      await expect(title).toBeVisible()
+
+      // Now should be able to modify players again
+      const addPlayerButton = page.locator('button:has-text("Add Player"), button:has-text("+")')
+      if (await addPlayerButton.first().isVisible({ timeout: 2000 }).catch(() => false)) {
+        await expect(addPlayerButton.first()).toBeEnabled()
+      }
+    }
+  })
+
+  test('should allow navigating to different game after returning to arcade', async ({ page }) => {
+    // Start matching game
+    await page.goto('/arcade/matching')
+    await page.waitForLoadState('networkidle')
+
+    // Return to arcade
+    const returnButton = page.locator('button:has-text("Return to Arcade"), button:has-text("Setup")')
+    if (await returnButton.first().isVisible({ timeout: 2000 }).catch(() => false)) {
+      await returnButton.first().click()
+      await page.waitForTimeout(1000)
+    }
+
+    // Should be in arcade lobby
+    await expect(page).toHaveURL(/\/arcade\/?$/)
+
+    // Now navigate to different game - should NOT redirect back to matching
+    await page.goto('/arcade/memory-quiz')
+    await page.waitForTimeout(2000)
+
+    // Should stay on memory-quiz (not redirect back to matching)
+    await expect(page).toHaveURL(/\/arcade\/memory-quiz/)
+
+    // Should see memory quiz title
+    const title = page.locator('h1:has-text("Memory Lightning")')
+    await expect(title).toBeVisible({ timeout: 3000 })
+  })
+})
+
+test.describe('Arcade Modal Session - Session Persistence', () => {
+  test('should maintain active session across page reloads', async ({ page }) => {
+    // Start a game
+    await page.goto('/arcade/matching')
+    await page.waitForLoadState('networkidle')
+
+    // Start game
+    const startButton = page.locator('button:has-text("Start")')
+    if (await startButton.isVisible({ timeout: 2000 }).catch(() => false)) {
+      await startButton.click()
+      await page.waitForTimeout(1000)
+    }
+
+    // Reload the page
+    await page.reload()
+    await page.waitForLoadState('networkidle')
+
+    // Should still be on matching game
+    await expect(page).toHaveURL(/\/arcade\/matching/)
+    const gameTitle = page.locator('h1:has-text("Memory Pairs")')
+    await expect(gameTitle).toBeVisible()
+
+    // Try to navigate to arcade
+    await page.goto('/arcade')
+    await page.waitForTimeout(2000)
+
+    // Should be redirected back to matching
+    await expect(page).toHaveURL(/\/arcade\/matching/)
+  })
+})