1 files changed, 23 insertions, 0 deletions
diff --git a/src/chess.h b/src/chess.h
index 6b09840..aababc0 100755
--- a/src/chess.h
+++ b/src/chess.h
@@ -614,6 +614,10 @@ ATTACK_BITV;
 #define ROOK_XRAY_BIT  0x20000000UL
 #define QUEEN_BIT      0x00000010UL
 #define QUEEN_XRAY_BIT 0x10000000UL
+// King never x-rays (it can't move through a blocker), so there's no
+// KING_XRAY_BIT to go with this -- matches struct _ATTACK_BITV's
+// .small.uKing bit position (byte 0, bit 3).
+#define KING_BIT       0x00000008UL
 
 #define INVALID_PIECE_INDEX (17)
 #define IS_VALID_PIECE_INDEX(x) ((x) < INVALID_PIECE_INDEX)
@@ -770,6 +774,25 @@ typedef struct _POSITION
     BITBOARD bbQueenAttacks[2];
     BITBOARD bbQueenXrayAttacks[2];
 
+    // King's turn to convert (board_representation/EVAL.md section 9,
+    // 2026-09-05) -- the last piece type contributing to the old
+    // bvAttacks/ATTACK_BITV mechanism. Just g_KingAttacksBB[c]
+    // (generate.c's precomputed table, already used by move
+    // generation), no mobility computation involved and no x-ray
+    // (a king can't move through a blocker). Same Eval()-scoped/
+    // cleared-per-call lifetime as every other bbXAttacks accumulator
+    // above -- this also reproduces, for free, an existing
+    // order-dependent asymmetry _EvalKing's mailbox version already
+    // had: kings are evaluated black-then-white (Eval()'s fixed
+    // order), so white's king-safety computation can see black's
+    // already-written attack bits but not vice versa. Once this
+    // lands, nothing writes bvAttacks/ATTACK_BITV any more -- see
+    // EVAL.md section 9 for the planned follow-up that deletes the
+    // whole mechanism and simplifies the transitional
+    // _IsSquareAttackedByX/_IsSquareXrayedByX helpers into plain
+    // bitboard reads.
+    BITBOARD bbKingAttacks[2];
+
     ULONG uWhiteSqBishopCount[2];          // num bishops on white squares
     SCORE iMaterialBalance[2];             // material balance