diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f80f75c..4e1a665 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -51,11 +51,18 @@ jobs:
       - name: Configure CMake
         shell: bash
         run: |
+          if [[ "${{ matrix.os }}" == "ubuntu-latest" ]]; then
+            if "${{ matrix.cpp_compiler }}" == "clang++" ]]; then
+              SANITIZERS="memory,undefined"
+            else
+              SANITIZERS="address,undefined"
+            fi
+          fi
           cmake -B "${{ steps.vars.outputs.dir }}" \
                 -DCMAKE_C_COMPILER=${{ matrix.c_compiler }} \
                 -DCMAKE_CXX_COMPILER=${{ matrix.cpp_compiler }} \
                 -DCMAKE_BUILD_TYPE=${{ matrix.build_type }} \
-                -DSANITIZERS="address,undefined" \
+                -DSANITIZERS=${SANITIZERS} \
                 -DDART_TESTING_TIMEOUT=0 \
                 -S "${{ github.workspace }}"
 
diff --git a/.github/workflows/try_compile.yml b/.github/workflows/try_compile.yml
index 730a31e..e436057 100644
--- a/.github/workflows/try_compile.yml
+++ b/.github/workflows/try_compile.yml
@@ -1,7 +1,7 @@
 name: Compilation
 
 on:
-  pull_request: 
+  push: 
 
 jobs:
   build:
diff --git a/movegen.cpp b/movegen.cpp
index 5bdfcc5..d92e78a 100644
--- a/movegen.cpp
+++ b/movegen.cpp
@@ -4,7 +4,39 @@
 namespace chess {
 
 namespace _chess {
-#if defined(__AVX512BW__)
+
+#if defined(USE_AVX512ICL)
+
+// clang-format off
+const __m512i AllSquares = _mm512_set_epi8(
+  63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41,
+  40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18,
+  17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0);
+// clang-format on
+
+template <Direction offset> inline Move *splat_pawn_moves(Move *moveList, Bitboard to_bb) {
+    assert(popcount(to_bb) <= 8); // <= 8 pawns per side
+
+    const __m128i toSquares = _mm_cvtepi8_epi16(_mm512_castsi512_si128(_mm512_maskz_compress_epi8(to_bb, AllSquares)));
+    const __m128i fromSquares = _mm_subs_epi16(toSquares, _mm_set1_epi16(offset));
+    const __m128i moves = _mm_or_si128(_mm_slli_epi16(fromSquares, 6), _mm_slli_epi16(toSquares, 0));
+
+    _mm_storeu_si128(reinterpret_cast<__m128i *>(moveList), moves);
+    return moveList + popcount(to_bb);
+}
+
+inline Move *splat_moves(Move *moveList, Square from, Bitboard to_bb) {
+    assert(popcount(to_bb) <= 32); // Q can attack up to 27 squares
+
+    const __m512i fromVec = _mm512_set1_epi16(Move(from, SQUARE_ZERO).raw());
+    const __m512i toSquares = _mm512_cvtepi8_epi16(_mm512_castsi512_si256(_mm512_maskz_compress_epi8(to_bb, AllSquares)));
+    const __m512i moves = _mm512_or_si512(fromVec, _mm512_slli_epi16(toSquares, Move::ToSqShift));
+
+    _mm512_storeu_si512(moveList, moves);
+    return moveList + popcount(to_bb);
+}
+
+#elif defined(__AVX512BW__)
 template <int Offset = 0> struct alignas(64) SplatTable {
     std::array<uint16_t, 64> data;
     constexpr int clamp64(int x) { return (x < 0) ? 0 : (x > 63 ? 63 : x); }
@@ -213,7 +245,7 @@ void movegen::genPawnSingleMoves(
 }
 template <typename T, Color c, bool capturesOnly>
 void movegen::genKnightMoves(const _Position<T, void> &pos, Movelist &list, Bitboard _pin_mask, Bitboard _check_mask) {
-    Bitboard knights = pos.template pieces<KNIGHT, c>() & ~_pin_mask; // yes, unconditionally.
+    Bitboard knights = pos.template pieces<KNIGHT, c>() & ~_pin_mask;
     while (knights) {
         Square x = static_cast<Square>(pop_lsb(knights));
         Bitboard moves = attacks::knight(x) & ~pos.occ(c);
@@ -253,7 +285,6 @@ void movegen::genKingMoves(const _Position<T, void> &pos, Movelist &out, Bitboar
     // Enemy king (adjacent control squares)
     enemyAttacks |= attacks::king(pos.kingSq(them));
 
-    // Candidate king moves = legal squares not attacked by enemy
     Bitboard moves = attacks::king(kingSq) & ~myOcc & ~enemyAttacks;
     if constexpr (capturesOnly)
         moves &= pos.occ(~c);
@@ -289,8 +320,7 @@ void movegen::genSlidingMoves(
     static_assert(pt == BISHOP || pt == ROOK || pt == QUEEN, "Sliding pieces only.");
     Bitboard sliders = pos.template pieces<pt, c>();
     Bitboard occ_all = pos.occ();
-    // Square king_sq = current_state.kings[c];
-    Bitboard rook_pinners = _rook_pin; // bitboard of enemy rooks/queens pinning
+    Bitboard rook_pinners = _rook_pin;
     Bitboard bishop_pinners = _bishop_pin;
     if constexpr (pt == BISHOP)
         sliders &= ~rook_pinners;
@@ -305,7 +335,6 @@ void movegen::genSlidingMoves(
         Bitboard bishop_hit = bishop_pinners & from_bb;
         Bitboard pin_mask = rook_hit ? rook_pinners : bishop_hit ? bishop_pinners : ~0ULL;
 
-        // Bitboard blockers = occ() ^ from_bb; // remove piece temporarily
         auto func = attacks::queen;
         if constexpr (pt == BISHOP)
             func = attacks::bishop;
diff --git a/non_core_tests.cpp b/non_core_tests.cpp
index b9536ac..a5116a7 100644
--- a/non_core_tests.cpp
+++ b/non_core_tests.cpp
@@ -893,9 +893,13 @@ TEST_SUITE("SAN Parser") {
 }
 
 TEST_SUITE("misc tests") {
-    TEST_CASE("FEN reconstruction") {
+    TEST_CASE("FEN reconstruction (Chess960)") {
         Position pos(Position::START_CHESS960_FEN, true);
-        REQUIRE(pos.fen() == Position::START_CHESS960_FEN);
+        REQUIRE(pos.fen(false) == Position::START_CHESS960_FEN);
+        REQUIRE(pos.fen() == Position::START_FEN);
+        pos.setFEN(Position::START_CHESS960_FEN, true, chess::MODE_SMK);
+        REQUIRE(pos.fen(false) == Position::START_CHESS960_FEN);
+        REQUIRE(pos.fen() == Position::START_FEN);
     }
 }
 int main(int argc, char **argv) {
diff --git a/position.cpp b/position.cpp
index c8bc9ec..d3bdbeb 100644
--- a/position.cpp
+++ b/position.cpp
@@ -197,7 +197,8 @@ template <typename PieceC, typename T> template <bool Strict> void _Position<Pie
     }
 }
 
-template <typename PieceC, typename T> void _Position<PieceC, T>::setFEN(const std::string &str, bool chess960) {
+template <typename PieceC, typename T>
+void _Position<PieceC, T>::setFEN(const std::string &str, bool chess960, FENParsingMode mode) {
     current_state = HistoryEntry<PieceC>();
     history.clear();
     _chess960 = chess960;
@@ -329,6 +330,8 @@ template <typename PieceC, typename T> void _Position<PieceC, T>::setFEN(const s
                 }
                 return SQ_NONE;
             };
+            bool allow_xfen = (mode == MODE_XFEN || mode == MODE_AUTO);
+            bool allow_smk = (mode == MODE_SMK || mode == MODE_AUTO);
             auto apply = [&](char c) {
                 Square king_sq = findKing();
                 if (king_sq == SQ_NONE)
@@ -368,24 +371,28 @@ template <typename PieceC, typename T> void _Position<PieceC, T>::setFEN(const s
                 };
 
                 if (c == 'K' && color == WHITE) {
+                    INVALID_ARG_IF(chess960 && !allow_xfen, "shredder fen into xfen parser");
                     if (rook_ks == SQ_NONE)
                         return;
                     if (rank_of(king_sq) != rank_of(rook_ks))
                         return;
                     setKS(rook_ks);
                 } else if (c == 'Q' && color == WHITE) {
+                    INVALID_ARG_IF(chess960 && !allow_xfen, "shredder fen into xfen parser");
                     if (rook_qs == SQ_NONE)
                         return;
                     if (rank_of(king_sq) != rank_of(rook_qs))
                         return;
                     setQS(rook_qs);
                 } else if (c == 'k' && color == BLACK) {
+                    INVALID_ARG_IF(chess960 && !allow_xfen, "shredder fen into xfen parser");
                     if (rook_ks == SQ_NONE)
                         return;
                     if (rank_of(king_sq) != rank_of(rook_ks))
                         return;
                     setKS(rook_ks);
                 } else if (c == 'q' && color == BLACK) {
+                    INVALID_ARG_IF(chess960 && !allow_xfen, "shredder fen into xfen parser");
                     if (rook_qs == SQ_NONE)
                         return;
                     if (rank_of(king_sq) != rank_of(rook_qs))
@@ -394,6 +401,7 @@ template <typename PieceC, typename T> void _Position<PieceC, T>::setFEN(const s
                 }
 
                 else if (c >= 'A' && c <= 'H' && color == WHITE) {
+                    INVALID_ARG_IF(chess960 && !allow_smk, "xfen into shredder fen parser");
                     File f = static_cast<File>(c - 'A');
                     Square rook_sq = make_sq(RANK_1, f);
 
@@ -403,6 +411,7 @@ template <typename PieceC, typename T> void _Position<PieceC, T>::setFEN(const s
 
                     (f > file_of(king_sq)) ? setKS(rook_sq) : setQS(rook_sq);
                 } else if (c >= 'a' && c <= 'h' && color == BLACK) {
+                    INVALID_ARG_IF(chess960 && !allow_smk, "xfen into shredder fen parser");
                     File f = static_cast<File>(c - 'a');
                     Square rook_sq = make_sq(RANK_8, f);
 
@@ -474,7 +483,7 @@ template <typename PieceC, typename T> void _Position<PieceC, T>::setFEN(const s
     current_state.repetition = current_state.pliesFromNull = 0;
 }
 
-template <typename PieceC, typename T> std::string _Position<PieceC, T>::fen() const {
+template <typename PieceC, typename T> std::string _Position<PieceC, T>::fen(bool xfen) const {
     std::ostringstream ss;
 
     // 1) Piece placement
@@ -508,13 +517,21 @@ template <typename PieceC, typename T> std::string _Position<PieceC, T>::fen() c
     std::string castlingStr;
     if (chess960()) {
         if (castlingRights() & WHITE_OO)
-            castlingStr += static_cast<char>('A' + file_of(current_state.castlingMetadata[WHITE].rook_start_ks));
+            castlingStr += (xfen && current_state.castlingMetadata[WHITE].rook_start_ks == SQ_H1)
+                               ? 'K'
+                               : static_cast<char>('A' + file_of(current_state.castlingMetadata[WHITE].rook_start_ks));
         if (castlingRights() & WHITE_OOO)
-            castlingStr += static_cast<char>('A' + file_of(current_state.castlingMetadata[WHITE].rook_start_qs));
+            castlingStr += (xfen && current_state.castlingMetadata[WHITE].rook_start_qs == SQ_A1)
+                               ? 'Q'
+                               : static_cast<char>('A' + file_of(current_state.castlingMetadata[WHITE].rook_start_qs));
         if (castlingRights() & BLACK_OO)
-            castlingStr += static_cast<char>('a' + file_of(current_state.castlingMetadata[BLACK].rook_start_ks));
+            castlingStr += (xfen && current_state.castlingMetadata[BLACK].rook_start_ks == SQ_H8)
+                               ? 'k'
+                               : static_cast<char>('a' + file_of(current_state.castlingMetadata[BLACK].rook_start_ks));
         if (castlingRights() & BLACK_OOO)
-            castlingStr += static_cast<char>('a' + file_of(current_state.castlingMetadata[BLACK].rook_start_qs));
+            castlingStr += (xfen && current_state.castlingMetadata[BLACK].rook_start_qs == SQ_A8)
+                               ? 'q'
+                               : static_cast<char>('a' + file_of(current_state.castlingMetadata[BLACK].rook_start_qs));
     } else {
         if (castlingRights() & WHITE_OO)
             castlingStr += 'K';
@@ -858,8 +875,8 @@ template <typename PieceC, typename T> CastlingRights _Position<PieceC, T>::clea
 }
 // clang-format off
 #define INSTANTIATE(PieceC) \
-template void _Position<PieceC, void>::setFEN(const std::string &, bool); \
-template std::string _Position<PieceC, void>::fen() const; \
+template void _Position<PieceC, void>::setFEN(const std::string &, bool, FENParsingMode); \
+template std::string _Position<PieceC, void>::fen(bool) const; \
 template void _Position<PieceC, void>::doMove<false>(const Move &move); \
 template void _Position<PieceC, void>::doMove<true>(const Move &move); \
 template void _Position<PieceC, void>::refresh_attacks(); \
diff --git a/position.h b/position.h
index 482fd33..4fd1fc3 100644
--- a/position.h
+++ b/position.h
@@ -36,6 +36,9 @@ template <typename Piece> struct alignas(64) HistoryEntry {
 };
 
 enum class CheckType { NO_CHECK, DIRECT_CHECK, DISCOVERY_CHECK };
+
+enum FENParsingMode { MODE_XFEN, MODE_SMK, MODE_AUTO };
+
 enum class MoveGenType : uint16_t {
     NONE = 0,
 
@@ -396,16 +399,16 @@ template <typename PieceC = EnginePiece, typename = std::enable_if_t<is_piece_en
     [[nodiscard]] inline Square kingSq(Color c) const { return current_state.kings[c]; }
     [[nodiscard]] inline Bitboard checkers() const { return _checkers; }
     [[nodiscard]] inline Bitboard pin_mask() const { return _pin_mask; }
-    inline _Position(std::string fen = START_FEN, bool chess960 = false) {
+    inline _Position(std::string fen = START_FEN, bool chess960 = false, FENParsingMode xfen = MODE_AUTO) {
         history.reserve(6144);
-        setFEN(fen, chess960);
+        setFEN(fen, chess960, xfen);
     }
     [[nodiscard]] inline bool isCapture(Move mv) const {
         return mv.type_of() == EN_PASSANT || (mv.type_of() != CASTLING && piece_on(mv.to_sq()) != PieceC::NO_PIECE);
     }
     [[nodiscard]] inline bool is_capture(Move mv) const { return isCapture(mv); }
     [[nodiscard]] inline bool is_zeroing(Move mv) const { return isCapture(mv) || at<PieceType>(mv.from_sq()) == PAWN; }
-    [[nodiscard]] std::string fen() const;
+    [[nodiscard]] std::string fen(bool xfen = true) const;
     [[nodiscard]] inline uint8_t halfmoveClock() const { return current_state.halfMoveClock; }
     [[nodiscard]] inline uint16_t fullmoveNumber() const { return current_state.fullMoveNumber; }
     [[nodiscard]] inline uint8_t rule50_count() const { return current_state.halfMoveClock; }
@@ -428,9 +431,13 @@ template <typename PieceC = EnginePiece, typename = std::enable_if_t<is_piece_en
     }
     inline Square enpassantSq() const { return ep_square(); }
     CastlingRights clean_castling_rights() const;
-    void setFEN(const std::string &str, bool chess960 = false);
-    inline void set_fen(const std::string &str, bool chess960 = false) { setFEN(str, chess960); }
-    inline void setFen(const std::string &str, bool chess960 = false) { setFEN(str, chess960); }
+    void setFEN(const std::string &str, bool chess960 = false, FENParsingMode xfen = MODE_AUTO);
+    inline void set_fen(const std::string &str, bool chess960 = false, FENParsingMode xfen = MODE_AUTO) {
+        setFEN(str, chess960, xfen);
+    }
+    inline void setFen(const std::string &str, bool chess960 = false, FENParsingMode xfen = MODE_AUTO) {
+        setFEN(str, chess960, xfen);
+    }
     Move parse_uci(std::string) const;
     Move push_uci(std::string);
     Square _valid_ep_square() const;