diff --git a/src/main/java/top/ellan/mahjong/table/core/round/GbBotDecisionService.java b/src/main/java/top/ellan/mahjong/table/core/round/GbBotDecisionService.java
index 7045301..cd3298e 100644
--- a/src/main/java/top/ellan/mahjong/table/core/round/GbBotDecisionService.java
+++ b/src/main/java/top/ellan/mahjong/table/core/round/GbBotDecisionService.java
@@ -30,8 +30,7 @@ int suggestedDiscardIndex(
         if (hand == null || hand.isEmpty()) {
             return -1;
         }
-        DiscardChoice best = this.bestDiscardChoice(hand, melds, tingEvaluator);
-        return best == null ? hand.size() - 1 : best.index();
+        return this.bestDiscardIndex(hand, melds, tingEvaluator);
     }
 
     ReactionResponse suggestedReaction(
@@ -178,6 +177,54 @@ private long readyScoreForBestDiscard(
         return best == null ? 0 : best.readyScore();
     }
 
+    /**
+     * Index-only variant of {@link #bestDiscardChoice} for the
+     * {@link #suggestedDiscardIndex} hot path. Avoids allocating a
+     * {@link DiscardChoice} record per call when the caller only needs the
+     * discard index. The loop body is identical; only the return shape
+     * differs (primitive {@code int} vs record).
+     */
+    private int bestDiscardIndex(
+        List<MahjongTile> hand,
+        List<GbMeldState> melds,
+        TingEvaluator tingEvaluator
+    ) {
+        int bestIndex = -1;
+        long bestReadyScore = 0;
+        int bestDiscardPreference = 0;
+        GbTingResponse[] tingMemo = new GbTingResponse[TILE_KIND_COUNT];
+        MahjongTile previousDiscarded = null;
+        int previousDiscardPreference = 0;
+        for (int i = 0; i < hand.size(); i++) {
+            MahjongTile discarded = hand.get(i);
+            int discardedOrdinal = discarded.ordinal();
+            GbTingResponse ting = tingMemo[discardedOrdinal];
+            boolean tingMemoHit = ting != null;
+            if (ting == null) {
+                List<MahjongTile> remaining = new ArrayList<>(hand);
+                remaining.remove(i);
+                ting = tingEvaluator.evaluate(remaining, melds);
+                if (ting != null) {
+                    tingMemo[discardedOrdinal] = ting;
+                }
+            }
+            long candidateReadyScore = readyScore(ting);
+            int candidateDiscardPreference = tingMemoHit && discarded == previousDiscarded
+                ? previousDiscardPreference
+                : discardPreference(hand, discarded);
+            previousDiscarded = discarded;
+            previousDiscardPreference = candidateDiscardPreference;
+            if (bestIndex < 0
+                || candidateReadyScore > bestReadyScore
+                || (candidateReadyScore == bestReadyScore && candidateDiscardPreference > bestDiscardPreference)) {
+                bestIndex = i;
+                bestReadyScore = candidateReadyScore;
+                bestDiscardPreference = candidateDiscardPreference;
+            }
+        }
+        return bestIndex < 0 ? hand.size() - 1 : bestIndex;
+    }
+
     private DiscardChoice bestDiscardChoice(
         List<MahjongTile> hand,
         List<GbMeldState> melds,
diff --git a/src/main/java/top/ellan/mahjong/table/core/round/GbRoundSupport.java b/src/main/java/top/ellan/mahjong/table/core/round/GbRoundSupport.java
index 3dbbaf6..e7a688d 100644
--- a/src/main/java/top/ellan/mahjong/table/core/round/GbRoundSupport.java
+++ b/src/main/java/top/ellan/mahjong/table/core/round/GbRoundSupport.java
@@ -118,15 +118,55 @@ static boolean sameKind(MahjongTile left, MahjongTile right) {
         return leftBase == rightBase;
     }
 
+    // Precomputed lookup tables indexed by MahjongTile.ordinal(). Eliminates the
+    // per-call String allocation (name().substring(1,2)) and Integer.parseInt
+    // parsing inside hot loops such as GbBotDecisionService.discardPreference.
+    private static final int[] TILE_NUMBERS = buildTileNumbers();
+    private static final boolean[] TILE_HONORS = buildTileHonors();
+
+    private static int[] buildTileNumbers() {
+        MahjongTile[] values = MahjongTile.values();
+        int[] numbers = new int[values.length];
+        int east = MahjongTile.EAST.ordinal();
+        int redDragon = MahjongTile.RED_DRAGON.ordinal();
+        for (MahjongTile tile : values) {
+            int ord = tile.ordinal();
+            if (tile.isFlower() || (ord >= east && ord <= redDragon)) {
+                numbers[ord] = 0;
+                continue;
+            }
+            // UNKNOWN and any other non-suited tile would fail parseInt; leave 0.
+            // Callers never pass such tiles to tileNumber() (they guard with
+            // isFlower()/isHonor() or only pass suited tiles from hands/walls).
+            try {
+                numbers[ord] = Integer.parseInt(tile.name().substring(1, 2));
+            } catch (NumberFormatException ignored) {
+                numbers[ord] = 0;
+            }
+        }
+        return numbers;
+    }
+
+    private static boolean[] buildTileHonors() {
+        MahjongTile[] values = MahjongTile.values();
+        boolean[] honors = new boolean[values.length];
+        int east = MahjongTile.EAST.ordinal();
+        int redDragon = MahjongTile.RED_DRAGON.ordinal();
+        for (int i = 0; i < values.length; i++) {
+            honors[i] = i >= east && i <= redDragon;
+        }
+        return honors;
+    }
+
     static boolean isHonor(MahjongTile tile) {
-        return tile.ordinal() >= MahjongTile.EAST.ordinal() && tile.ordinal() <= MahjongTile.RED_DRAGON.ordinal();
+        return TILE_HONORS[tile.ordinal()];
     }
 
     static int tileNumber(MahjongTile tile) {
         if (tile == null || tile.isFlower() || isHonor(tile)) {
             return 0;
         }
-        return Integer.parseInt(tile.name().substring(1, 2));
+        return TILE_NUMBERS[tile.ordinal()];
     }
 
     static MahjongTile offsetTile(MahjongTile tile, int delta) {