diff --git a/frontend-sba/composables/useWebSocket.ts b/frontend-sba/composables/useWebSocket.ts
index f42c426..3aeaa12 100644
--- a/frontend-sba/composables/useWebSocket.ts
+++ b/frontend-sba/composables/useWebSocket.ts
@@ -306,10 +306,8 @@ export function useWebSocket() {
     socketInstance.on('game_state_sync', (data) => {
       console.log('[WebSocket] Full game state sync received')
       gameStore.setGameState(data.state)
-      // Add recent plays to history
-      data.recent_plays.forEach((play) => {
-        gameStore.addPlayToHistory(play)
-      })
+      // Replace play history with synced plays (O(1) - no iteration/dedup needed)
+      gameStore.setPlayHistory(data.recent_plays)
     })
 
     socketInstance.on('inning_change', (data) => {
diff --git a/frontend-sba/store/game.ts b/frontend-sba/store/game.ts
index 61be00c..055c825 100644
--- a/frontend-sba/store/game.ts
+++ b/frontend-sba/store/game.ts
@@ -178,15 +178,18 @@ export const useGameStore = defineStore('game', () => {
   }
 
   /**
-   * Add play to history (with deduplication by play_number)
+   * Set play history (replaces entire array - used for initial sync)
+   * O(1) operation - no deduplication needed
+   */
+  function setPlayHistory(plays: PlayResult[]) {
+    playHistory.value = plays
+  }
+
+  /**
+   * Add play to history (used for live play_resolved events)
+   * O(1) operation - assumes no duplicates from live events
    */
   function addPlayToHistory(play: PlayResult) {
-    // Check if play already exists (deduplicate by play_number)
-    const exists = playHistory.value.some(p => p.play_number === play.play_number)
-    if (exists) {
-      return
-    }
-
     playHistory.value.push(play)
 
     // Update game state from play result if provided
@@ -409,6 +412,7 @@ export const useGameStore = defineStore('game', () => {
     updateGameState,
     setLineups,
     updateLineup,
+    setPlayHistory,
     addPlayToHistory,
     setDecisionPrompt,
     clearDecisionPrompt,