diff --git a/.github/workflows/build-ton-linux-arm64-appimage.yml b/.github/workflows/build-ton-linux-arm64-appimage.yml
index cb8a49844..cccebce35 100644
--- a/.github/workflows/build-ton-linux-arm64-appimage.yml
+++ b/.github/workflows/build-ton-linux-arm64-appimage.yml
@@ -24,13 +24,13 @@ jobs:
         sudo apt install -y build-essential git cmake ninja-build zlib1g-dev libsecp256k1-dev libmicrohttpd-dev libsodium-dev liblz4-dev ccache libgsl-dev libblas-dev libgslcblas0
         mkdir ~/.ccache 3pp
 
-    - name: Install clang-16
+    - name: Install clang-21
       run: |
         lsb_release -a
         wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-        echo "deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-16 main" | sudo tee /etc/apt/sources.list.d/llvm.list
+        echo "deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
         sudo apt-get -y update
-        sudo apt-get install -y clang-16
+        sudo apt-get install -y clang-21
 
     - name: Cache 3pp
       id: cache-3pp
diff --git a/.github/workflows/build-ton-linux-arm64-shared.yml b/.github/workflows/build-ton-linux-arm64-shared.yml
index 1c5ffae8f..5c5e86d17 100644
--- a/.github/workflows/build-ton-linux-arm64-shared.yml
+++ b/.github/workflows/build-ton-linux-arm64-shared.yml
@@ -29,13 +29,22 @@ jobs:
         mkdir ~/.ccache
 
     - if: matrix.os != 'ubuntu-24.04-arm'
-      name: Install llvm-16
+      name: Install llvm-21
       run: |
         lsb_release -a
         wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-        echo "deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-16 main" | sudo tee /etc/apt/sources.list.d/llvm.list
+        echo "deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
         sudo apt-get -y update
-        sudo apt-get install -y clang-16
+        sudo apt-get install -y clang-21
+
+    - if: matrix.os == 'ubuntu-24.04-arm'
+      name: Install llvm-21
+      run: |
+        lsb_release -a
+        wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
+        echo "deb http://apt.llvm.org/noble/ llvm-toolchain-noble-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
+        sudo apt-get -y update
+        sudo apt-get install -y clang-21
 
     - name: Cache OpenSSL
       id: cache-openssl
diff --git a/.github/workflows/build-ton-linux-x86-64-appimage.yml b/.github/workflows/build-ton-linux-x86-64-appimage.yml
index 0bebcbadc..aa9787cd6 100644
--- a/.github/workflows/build-ton-linux-x86-64-appimage.yml
+++ b/.github/workflows/build-ton-linux-x86-64-appimage.yml
@@ -24,11 +24,11 @@ jobs:
         sudo apt install -y build-essential git cmake ninja-build zlib1g-dev libsecp256k1-dev libmicrohttpd-dev libsodium-dev liblz4-dev ccache libgsl-dev libblas-dev libgslcblas0       
         mkdir ~/.ccache 3pp
 
-    - name: Install clang-16
+    - name: Install clang-21
       run: |
         wget https://apt.llvm.org/llvm.sh
         chmod +x llvm.sh
-        sudo ./llvm.sh 16 clang
+        sudo ./llvm.sh 21 clang
 
     - name: Cache 3pp
       id: cache-3pp
diff --git a/.github/workflows/build-ton-linux-x86-64-shared.yml b/.github/workflows/build-ton-linux-x86-64-shared.yml
index 87b9dc15a..bccfab3af 100644
--- a/.github/workflows/build-ton-linux-x86-64-shared.yml
+++ b/.github/workflows/build-ton-linux-x86-64-shared.yml
@@ -32,7 +32,16 @@ jobs:
       run: |
         wget https://apt.llvm.org/llvm.sh
         chmod +x llvm.sh
-        sudo ./llvm.sh 16 clang
+        sudo ./llvm.sh 21 clang
+
+    - if: matrix.os == 'ubuntu-24.04'
+      name: Install llvm-21
+      run: |
+        lsb_release -a
+        wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
+        echo "deb http://apt.llvm.org/noble/ llvm-toolchain-noble-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
+        sudo apt -y update
+        sudo apt install -y clang-21
 
     - name: Cache OpenSSL
       id: cache-openssl
diff --git a/.github/workflows/build-ton-wasm-emscripten.yml b/.github/workflows/build-ton-wasm-emscripten.yml
index ce09f530e..6e575b399 100644
--- a/.github/workflows/build-ton-wasm-emscripten.yml
+++ b/.github/workflows/build-ton-wasm-emscripten.yml
@@ -18,11 +18,11 @@ jobs:
         sudo apt-get install -y build-essential git openssl cmake ninja-build zlib1g-dev libssl-dev libsecp256k1-dev libmicrohttpd-dev libsodium-dev liblz4-dev libjemalloc-dev
         mkdir -p 3pp_emscripten
 
-    - name: Install clang-16
+    - name: Install clang-21
       run: |
         wget https://apt.llvm.org/llvm.sh
         chmod +x llvm.sh
-        sudo ./llvm.sh 16 clang
+        sudo ./llvm.sh 21 clang
 
     - name: Cache OpenSSL
       id: cache-openssl
diff --git a/Dockerfile b/Dockerfile
index 7a53500db..6e7668b00 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -11,11 +11,11 @@ RUN apt-get update && \
 
 RUN wget https://apt.llvm.org/llvm.sh && \
     chmod +x llvm.sh && \
-    ./llvm.sh 16 all && \
+    ./llvm.sh 21 all && \
     rm -rf /var/lib/apt/lists/*
 
-ENV CC=/usr/bin/clang-16
-ENV CXX=/usr/bin/clang++-16
+ENV CC=/usr/bin/clang-21
+ENV CXX=/usr/bin/clang++-21
 ENV CCACHE_DISABLE=1
 
 WORKDIR /
diff --git a/README.md b/README.md
index 897ba809a..9833cecd9 100644
--- a/README.md
+++ b/README.md
@@ -79,7 +79,7 @@ Install additional system libraries
           
   wget https://apt.llvm.org/llvm.sh
   chmod +x llvm.sh
-  sudo ./llvm.sh 16 all
+  sudo ./llvm.sh 21 clang
 ```
 Compile TON binaries
 ```bash
@@ -117,7 +117,7 @@ Install additional system libraries on Ubuntu
           
   wget https://apt.llvm.org/llvm.sh
   chmod +x llvm.sh
-  sudo ./llvm.sh 16 all
+  sudo ./llvm.sh 21 clang
 ```
 Compile TON binaries with emscripten
 ```bash
diff --git a/assembly/android/build-android-tonlib.sh b/assembly/android/build-android-tonlib.sh
index dda74c166..b1bff6c4a 100644
--- a/assembly/android/build-android-tonlib.sh
+++ b/assembly/android/build-android-tonlib.sh
@@ -8,8 +8,8 @@ while getopts 'a' flag; do
   esac
 done
 
-export CC=$(which clang-16)
-export CXX=$(which clang++-16)
+export CC=$(which clang-21)
+export CXX=$(which clang++-21)
 export CCACHE_DISABLE=1
 
 if [ ! -d android-ndk-r27d ]; then
diff --git a/assembly/native/build-macos-portable.sh b/assembly/native/build-macos-portable.sh
index a86435a4f..29bb51409 100644
--- a/assembly/native/build-macos-portable.sh
+++ b/assembly/native/build-macos-portable.sh
@@ -6,6 +6,13 @@ with_ccache=false
 
 OSX_TARGET=11.0
 
+MACOS_MAJOR=0
+if [ "$(uname)" = "Darwin" ]; then
+  MACOS_MAJOR=$(sw_vers -productVersion | cut -d. -f1)
+  export SDKROOT="$(xcrun --sdk macosx --show-sdk-path)"
+  echo "Using SDKROOT=$SDKROOT"
+fi
+
 while getopts 'taco:' flag; do
   case "${flag}" in
     t) with_tests=true ;;
@@ -21,14 +28,26 @@ if [ ! -d "build" ]; then
   mkdir build
   cd build
 else
-  cd build
+  cd build || exit
   rm -rf .ninja* CMakeCache.txt
 fi
 
 export NONINTERACTIVE=1
 brew install ninja pkg-config automake libtool autoconf texinfo
 export PATH=/usr/local/opt/ccache/libexec:$PATH
-brew install llvm@16
+
+if [ "$(uname)" = "Darwin" ]; then
+  if [ "$MACOS_MAJOR" -ge 15 ]; then
+    echo "macOS $MACOS_MAJOR detected -> using AppleClang (Xcode toolchain), NOT llvm@21"
+    export CC="$(xcrun --find clang)"
+    export CXX="$(xcrun --find clang++)"
+  else
+    echo "macOS $MACOS_MAJOR detected -> using Homebrew llvm@21"
+    brew install llvm@21
+    export CC="$(brew --prefix llvm@21)"/bin/clang
+    export CXX="$(brew --prefix llvm@21)"/bin/clang++
+  fi
+fi
 
 if [ "$with_ccache" = true ]; then
   brew install ccache
@@ -40,24 +59,15 @@ else
   export CCACHE_DISABLE=1
 fi
 
-
-if [ -f /opt/homebrew/opt/llvm@16/bin/clang ]; then
-  export CC=/opt/homebrew/opt/llvm@16/bin/clang
-  export CXX=/opt/homebrew/opt/llvm@16/bin/clang++
-else
-  export CC=/usr/local/opt/llvm@16/bin/clang
-  export CXX=/usr/local/opt/llvm@16/bin/clang++
-fi
-
 if [ ! -d "../3pp/lz4" ]; then
 mkdir -p ../3pp
 git clone https://github.com/lz4/lz4.git ../3pp/lz4
-cd ../3pp/lz4
+cd ../3pp/lz4 || exit
 lz4Path=`pwd`
 git checkout v1.9.4
-make -j4
+make -j4 CC="$CC" CFLAGS="--sysroot=$SDKROOT"
 test $? -eq 0 || { echo "Can't compile lz4"; exit 1; }
-cd ../../build
+cd ../../build  || exit
 # ./lib/liblz4.a
 # ./lib
 else
@@ -67,15 +77,15 @@ fi
 
 if [ ! -d "../3pp/libsodium-1.0.18" ]; then
   export LIBSODIUM_FULL_BUILD=1
-  cd ../3pp
+  cd ../3pp || exit
   curl -LO https://download.libsodium.org/libsodium/releases/libsodium-1.0.18.tar.gz
   tar -xzf libsodium-1.0.18.tar.gz
-  cd libsodium-1.0.18
+  cd libsodium-1.0.18  || exit
   sodiumPath=`pwd`
   ./configure --with-pic --enable-static
-  make -j4
+  make -j4 CC="$CC" CFLAGS="--sysroot=$SDKROOT"
   test $? -eq 0 || { echo "Can't compile libsodium"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   sodiumPath=$(pwd)/../3pp/libsodium-1.0.18
   echo "Using compiled libsodium"
@@ -83,13 +93,13 @@ fi
 
 if [ ! -d "../3pp/openssl_3" ]; then
   git clone https://github.com/openssl/openssl ../3pp/openssl_3
-  cd ../3pp/openssl_3
+  cd ../3pp/openssl_3 || exit
   opensslPath=`pwd`
   git checkout openssl-3.1.4
   ./config
-  make build_libs -j4
+  make build_libs -j4 CC="$CC" CFLAGS="--sysroot=$SDKROOT"
   test $? -eq 0 || { echo "Can't compile openssl_3"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   opensslPath=$(pwd)/../3pp/openssl_3
   echo "Using compiled openssl_3"
@@ -97,12 +107,12 @@ fi
 
 if [ ! -d "../3pp/zlib" ]; then
   git clone https://github.com/madler/zlib.git ../3pp/zlib
-  cd ../3pp/zlib
+  cd ../3pp/zlib || exit
   zlibPath=`pwd`
   ./configure --static
-  make -j4
+  make -j4 CC="$CC" CFLAGS="--sysroot=$SDKROOT"
   test $? -eq 0 || { echo "Can't compile zlib"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   zlibPath=$(pwd)/../3pp/zlib
   echo "Using compiled zlib"
@@ -110,12 +120,12 @@ fi
 
 if [ ! -d "../3pp/libmicrohttpd" ]; then
   git clone https://github.com/ton-blockchain/libmicrohttpd.git ../3pp/libmicrohttpd
-  cd ../3pp/libmicrohttpd
+  cd ../3pp/libmicrohttpd || exit
   libmicrohttpdPath=`pwd`
   ./configure --enable-static --disable-tests --disable-benchmark --disable-shared --disable-https --with-pic
-  make -j4
+  make -j4 CC="$CC" CFLAGS="--sysroot=$SDKROOT"
   test $? -eq 0 || { echo "Can't compile libmicrohttpd"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   libmicrohttpdPath=$(pwd)/../3pp/libmicrohttpd
   echo "Using compiled libmicrohttpd"
@@ -124,8 +134,8 @@ fi
 cmake -GNinja .. \
 -DPORTABLE=1 \
 -DCMAKE_OSX_DEPLOYMENT_TARGET:STRING=$OSX_TARGET \
--DCMAKE_CXX_FLAGS="-stdlib=libc++" \
--DCMAKE_SYSROOT=$(xcrun --show-sdk-path) \
+-DCMAKE_CXX_FLAGS="-nostdinc++ -isystem ${SDKROOT}/usr/include/c++/v1 -isystem ${SDKROOT}/usr/include" \
+-DCMAKE_SYSROOT="$(xcrun --show-sdk-path)" \
 -DCMAKE_BUILD_TYPE=Release \
 -DOPENSSL_FOUND=1 \
 -DOPENSSL_INCLUDE_DIR=$opensslPath/include \
diff --git a/assembly/native/build-macos-shared.sh b/assembly/native/build-macos-shared.sh
index 2d0638c1c..698343d3d 100644
--- a/assembly/native/build-macos-shared.sh
+++ b/assembly/native/build-macos-shared.sh
@@ -6,6 +6,13 @@ with_ccache=false
 
 OSX_TARGET=11.0
 
+MACOS_MAJOR=0
+if [ "$(uname)" = "Darwin" ]; then
+  MACOS_MAJOR=$(sw_vers -productVersion | cut -d. -f1)
+  export SDKROOT="$(xcrun --sdk macosx --show-sdk-path)"
+  echo "Using SDKROOT=$SDKROOT"
+fi
+
 while getopts 'taco:' flag; do
   case "${flag}" in
     t) with_tests=true ;;
@@ -21,14 +28,26 @@ if [ ! -d "build" ]; then
   mkdir build
   cd build
 else
-  cd build
+  cd build || exit
   rm -rf .ninja* CMakeCache.txt
 fi
 
 export NONINTERACTIVE=1
 brew install ninja libsodium libmicrohttpd pkg-config automake libtool autoconf gnutls
 export PATH=/usr/local/opt/ccache/libexec:$PATH
-brew install llvm@16
+
+if [ "$(uname)" = "Darwin" ]; then
+  if [ "$MACOS_MAJOR" -ge 15 ]; then
+    echo "macOS $MACOS_MAJOR detected -> using AppleClang (Xcode toolchain), NOT llvm@21"
+    export CC="$(xcrun --find clang)"
+    export CXX="$(xcrun --find clang++)"
+  else
+    echo "macOS $MACOS_MAJOR detected -> using Homebrew llvm@21"
+    brew install llvm@21
+    export CC="$(brew --prefix llvm@21)"/bin/clang
+    export CXX="$(brew --prefix llvm@21)"/bin/clang++
+  fi
+fi
 
 if [ "$with_ccache" = true ]; then
   brew install ccache
@@ -40,20 +59,12 @@ else
   export CCACHE_DISABLE=1
 fi
 
-if [ -f /opt/homebrew/opt/llvm@16/bin/clang ]; then
-  export CC=/opt/homebrew/opt/llvm@16/bin/clang
-  export CXX=/opt/homebrew/opt/llvm@16/bin/clang++
-else
-  export CC=/usr/local/opt/llvm@16/bin/clang
-  export CXX=/usr/local/opt/llvm@16/bin/clang++
-fi
-
 if [ ! -d "lz4" ]; then
   git clone https://github.com/lz4/lz4
-  cd lz4
+  cd lz4 || exit
   lz4Path=`pwd`
   git checkout v1.9.4
-  make -j4
+  make -j4 CC="$CC" CFLAGS="--sysroot=$SDKROOT"
   test $? -eq 0 || { echo "Can't compile lz4"; exit 1; }
   cd ..
 else
@@ -61,26 +72,13 @@ else
   echo "Using compiled lz4"
 fi
 
-if [ ! -d "zlib" ]; then
-  git clone https://github.com/madler/zlib.git
-  cd zlib
-  zlibPath=`pwd`
-  ./configure --static
-  make -j4
-  test $? -eq 0 || { echo "Can't compile zlib"; exit 1; }
-  cd ..
-else
-  zlibPath=$(pwd)/zlib
-  echo "Using compiled zlib"
-fi
-
 brew unlink openssl@1.1
 brew install openssl@3
 brew unlink openssl@3 &&  brew link --overwrite openssl@3
 
 cmake -GNinja -DCMAKE_BUILD_TYPE=Release .. \
--DCMAKE_CXX_FLAGS="-stdlib=libc++" \
--DCMAKE_SYSROOT=$(xcrun --show-sdk-path) \
+-DCMAKE_CXX_FLAGS="-nostdinc++ -isystem ${SDKROOT}/usr/include/c++/v1 -isystem ${SDKROOT}/usr/include" \
+-DCMAKE_SYSROOT="$(xcrun --show-sdk-path)" \
 -DLZ4_FOUND=1 \
 -DLZ4_LIBRARIES=$lz4Path/lib/liblz4.a \
 -DLZ4_INCLUDE_DIRS=$lz4Path/lib \
diff --git a/assembly/native/build-ubuntu-appimages.sh b/assembly/native/build-ubuntu-appimages.sh
index ef54f0632..d6ca99f2f 100644
--- a/assembly/native/build-ubuntu-appimages.sh
+++ b/assembly/native/build-ubuntu-appimages.sh
@@ -27,22 +27,22 @@ if [ ! -d "build" ]; then
   mkdir build
   cd build
 else
-  cd build
+  cd build || exit
   rm -rf .ninja* CMakeCache.txt
 fi
 
-export CC=$(which clang-16)
-export CXX=$(which clang++-16)
+export CC=$(which clang-21)
+export CXX=$(which clang++-21)
 
 if [ ! -d "../openssl_3" ]; then
   git clone https://github.com/openssl/openssl ../openssl_3
-  cd ../openssl_3
+  cd ../openssl_3 || exit
   opensslPath=`pwd`
   git checkout openssl-3.1.4
   ./config
   make build_libs -j$(nproc)
   test $? -eq 0 || { echo "Can't compile openssl_3"; exit 1; }
-  cd ../build
+  cd ../build || exit
 else
   opensslPath=$(pwd)/../openssl_3
   echo "Using compiled openssl_3"
@@ -110,6 +110,6 @@ if [ "$with_artifacts" = true ]; then
 fi
 
 if [ "$with_tests" = true ]; then
-  cd build
+  cd build || exit
   ctest --output-on-failure --timeout 1800
 fi
diff --git a/assembly/native/build-ubuntu-portable-libs.sh b/assembly/native/build-ubuntu-portable-libs.sh
index cf797cd23..f4dccdea9 100644
--- a/assembly/native/build-ubuntu-portable-libs.sh
+++ b/assembly/native/build-ubuntu-portable-libs.sh
@@ -28,22 +28,22 @@ if [ ! -d "build" ]; then
   mkdir build
   cd build
 else
-  cd build
+  cd build || exit
   rm -rf .ninja* CMakeCache.txt
 fi
 
-export CC=$(which clang-16)
-export CXX=$(which clang++-16)
+export CC=$(which clang-21)
+export CXX=$(which clang++-21)
 
 if [ ! -d "../3pp/lz4" ]; then
 mkdir -p ../3pp
 git clone https://github.com/lz4/lz4.git ../3pp/lz4
-cd ../3pp/lz4
+cd ../3pp/lz4 || exit
 lz4Path=`pwd`
 git checkout v1.9.4
 CFLAGS="-fPIC" make -j$(nproc)
 test $? -eq 0 || { echo "Can't compile lz4"; exit 1; }
-cd ../../build
+cd ../../build || exit
 else
   lz4Path=$(pwd)/../3pp/lz4
   echo "Using compiled lz4"
@@ -53,14 +53,14 @@ if [ ! -d "../3pp/libsodium" ]; then
   export LIBSODIUM_FULL_BUILD=1
   mkdir -p ../3pp/libsodium
   wget -O ../3pp/libsodium/libsodium-1.0.18.tar.gz https://github.com/jedisct1/libsodium/releases/download/1.0.18-RELEASE/libsodium-1.0.18.tar.gz
-  cd ../3pp/libsodium
+  cd ../3pp/libsodium || exit
   tar xf libsodium-1.0.18.tar.gz
-  cd libsodium-1.0.18
+  cd libsodium-1.0.18 || exit
   sodiumPath=`pwd`
   ./configure --with-pic --enable-static
   make -j$(nproc)
   test $? -eq 0 || { echo "Can't compile libsodium"; exit 1; }
-  cd ../../../build
+  cd ../../../build || exit
 else
   sodiumPath=$(pwd)/../3pp/libsodium/libsodium-1.0.18
   echo "Using compiled libsodium"
@@ -68,13 +68,13 @@ fi
 
 if [ ! -d "../3pp/openssl_3" ]; then
   git clone https://github.com/openssl/openssl ../3pp/openssl_3
-  cd ../3pp/openssl_3
+  cd ../3pp/openssl_3 || exit
   opensslPath=`pwd`
   git checkout openssl-3.1.4
   ./config
   make build_libs -j$(nproc)
   test $? -eq 0 || { echo "Can't compile openssl_3"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   opensslPath=$(pwd)/../3pp/openssl_3
   echo "Using compiled openssl_3"
@@ -82,12 +82,12 @@ fi
 
 if [ ! -d "../3pp/zlib" ]; then
   git clone https://github.com/madler/zlib.git ../3pp/zlib
-  cd ../3pp/zlib
+  cd ../3pp/zlib || exit
   zlibPath=`pwd`
   ./configure --static
   make -j$(nproc)
   test $? -eq 0 || { echo "Can't compile zlib"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   zlibPath=$(pwd)/../3pp/zlib
   echo "Using compiled zlib"
@@ -95,12 +95,12 @@ fi
 
 if [ ! -d "../3pp/libmicrohttpd" ]; then
   git clone https://github.com/ton-blockchain/libmicrohttpd.git ../3pp/libmicrohttpd
-  cd ../3pp/libmicrohttpd
+  cd ../3pp/libmicrohttpd || exit
   libmicrohttpdPath=`pwd`
   ./configure --enable-static --disable-tests --disable-benchmark --disable-shared --disable-https --with-pic
-  make -j4
+  make -j$(nproc)
   test $? -eq 0 || { echo "Can't compile libmicrohttpd"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   libmicrohttpdPath=$(pwd)/../3pp/libmicrohttpd
   echo "Using compiled libmicrohttpd"
diff --git a/assembly/native/build-ubuntu-portable.sh b/assembly/native/build-ubuntu-portable.sh
index 49a0205f6..38b0ddd2b 100644
--- a/assembly/native/build-ubuntu-portable.sh
+++ b/assembly/native/build-ubuntu-portable.sh
@@ -30,22 +30,22 @@ if [ ! -d "build" ]; then
   mkdir build
   cd build
 else
-  cd build
+  cd build || exit
   rm -rf .ninja* CMakeCache.txt
 fi
 
-export CC=$(which clang-16)
-export CXX=$(which clang++-16)
+export CC=$(which clang-21)
+export CXX=$(which clang++-21)
 
 if [ ! -d "../3pp/lz4" ]; then
 mkdir -p ../3pp
 git clone https://github.com/lz4/lz4.git ../3pp/lz4
-cd ../3pp/lz4
+cd ../3pp/lz4 || exit
 lz4Path=`pwd`
 git checkout v1.9.4
 CFLAGS="-fPIC" make -j$(nproc)
 test $? -eq 0 || { echo "Can't compile lz4"; exit 1; }
-cd ../../build
+cd ../../build || exit
 else
   lz4Path=$(pwd)/../3pp/lz4
   echo "Using compiled lz4"
@@ -54,14 +54,14 @@ fi
 if [ ! -d "../3pp/libsodium" ]; then
   export LIBSODIUM_FULL_BUILD=1
   git clone https://github.com/jedisct1/libsodium.git ../3pp/libsodium
-  cd ../3pp/libsodium
+  cd ../3pp/libsodium || exit
   sodiumPath=`pwd`
   git checkout 1.0.18
   ./autogen.sh
   ./configure --with-pic --enable-static
   make -j$(nproc)
   test $? -eq 0 || { echo "Can't compile libsodium"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   sodiumPath=$(pwd)/../3pp/libsodium
   echo "Using compiled libsodium"
@@ -69,13 +69,13 @@ fi
 
 if [ ! -d "../3pp/openssl_3" ]; then
   git clone https://github.com/openssl/openssl ../3pp/openssl_3
-  cd ../3pp/openssl_3
+  cd ../3pp/openssl_3 || exit
   opensslPath=`pwd`
   git checkout openssl-3.1.4
   ./config
   make build_libs -j$(nproc)
   test $? -eq 0 || { echo "Can't compile openssl_3"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   opensslPath=$(pwd)/../3pp/openssl_3
   echo "Using compiled openssl_3"
@@ -83,12 +83,12 @@ fi
 
 if [ ! -d "../3pp/zlib" ]; then
   git clone https://github.com/madler/zlib.git ../3pp/zlib
-  cd ../3pp/zlib
+  cd ../3pp/zlib || exit
   zlibPath=`pwd`
   ./configure --static
   make -j$(nproc)
   test $? -eq 0 || { echo "Can't compile zlib"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   zlibPath=$(pwd)/../3pp/zlib
   echo "Using compiled zlib"
@@ -96,12 +96,12 @@ fi
 
 if [ ! -d "../3pp/libmicrohttpd" ]; then
   git clone https://github.com/ton-blockchain/libmicrohttpd.git ../3pp/libmicrohttpd
-  cd ../3pp/libmicrohttpd
+  cd ../3pp/libmicrohttpd || exit
   libmicrohttpdPath=`pwd`
   ./configure --enable-static --disable-tests --disable-benchmark --disable-shared --disable-https --with-pic
-  make -j4
+  make -j$(nproc)
   test $? -eq 0 || { echo "Can't compile libmicrohttpd"; exit 1; }
-  cd ../../build
+  cd ../../build || exit
 else
   libmicrohttpdPath=$(pwd)/../3pp/libmicrohttpd
   echo "Using compiled libmicrohttpd"
@@ -170,7 +170,7 @@ if [ "$with_artifacts" = true ]; then
 fi
 
 if [ "$with_tests" = true ]; then
-  cd build
+  cd build || exit
 #  ctest --output-on-failure -E "test-catchain|test-actors|test-smartcont|test-adnl|test-validator-session-state|test-dht|test-rldp"
   ctest --output-on-failure -E "test-adnl"
 fi
diff --git a/assembly/native/build-ubuntu-shared.sh b/assembly/native/build-ubuntu-shared.sh
index 4db66a11e..5020a5658 100644
--- a/assembly/native/build-ubuntu-shared.sh
+++ b/assembly/native/build-ubuntu-shared.sh
@@ -30,23 +30,23 @@ if [ ! -d "build" ]; then
   mkdir build
   cd build
 else
-  cd build
+  cd build || exit
   rm -rf .ninja* CMakeCache.txt
 fi
 
-export CC=$(which clang-16)
-export CXX=$(which clang++-16)
+export CC=$(which clang-21)
+export CXX=$(which clang++-21)
 
 
 if [ ! -d "../openssl_3" ]; then
   git clone https://github.com/openssl/openssl ../openssl_3
-  cd ../openssl_3
+  cd ../openssl_3 || exit
   opensslPath=`pwd`
   git checkout openssl-3.1.4
   ./config
   make build_libs -j$(nproc)
   test $? -eq 0 || { echo "Can't compile openssl_3"; exit 1; }
-  cd ../build
+  cd ../build || exit
 else
   opensslPath=$(pwd)/../openssl_3
   echo "Using compiled openssl_3"
diff --git a/assembly/wasm/fift-func-wasm-build-ubuntu.sh b/assembly/wasm/fift-func-wasm-build-ubuntu.sh
index a99f27392..0c08c8c47 100644
--- a/assembly/wasm/fift-func-wasm-build-ubuntu.sh
+++ b/assembly/wasm/fift-func-wasm-build-ubuntu.sh
@@ -6,7 +6,7 @@
 
 # wget https://apt.llvm.org/llvm.sh
 # chmod +x llvm.sh
-# sudo ./llvm.sh 16 all
+# sudo ./llvm.sh 21 clang
 
 with_artifacts=false
 scratch_new=false
@@ -20,8 +20,8 @@ while getopts 'af' flag; do
   esac
 done
 
-export CC=$(which clang-16)
-export CXX=$(which clang++-16)
+export CC=$(which clang-21)
+export CXX=$(which clang++-21)
 export CCACHE_DISABLE=1
 
 echo `pwd`
@@ -32,7 +32,7 @@ fi
 
 if [ ! -d "openssl_3" ]; then
   git clone https://github.com/openssl/openssl openssl_3
-  cd openssl_3
+  cd openssl_3 || exit
   opensslPath=`pwd`
   git checkout openssl-3.1.4
   ./config
@@ -69,7 +69,7 @@ echo
   echo Using cloned emsdk
 fi
 
-cd emsdk
+cd emsdk || exit
 ./emsdk install 4.0.17
 ./emsdk activate 4.0.17
 EMSDK_DIR=`pwd`
@@ -84,7 +84,7 @@ cd ..
 if [ ! -f "3pp_emscripten/openssl_em/openssl_em" ]; then
   mkdir -p 3pp_emscripten
   git clone https://github.com/openssl/openssl 3pp_emscripten/openssl_em
-  cd 3pp_emscripten/openssl_em
+  cd 3pp_emscripten/openssl_em || exit
   emconfigure ./Configure linux-generic32 no-shared no-dso no-engine no-unit-test no-tests no-fuzz-afl no-fuzz-libfuzzer
   sed -i 's/CROSS_COMPILE=.*/CROSS_COMPILE=/g' Makefile
   sed -i 's/-ldl//g' Makefile
@@ -102,7 +102,7 @@ fi
 
 if [ ! -d "3pp_emscripten/zlib" ]; then
   git clone https://github.com/madler/zlib.git 3pp_emscripten/zlib
-  cd 3pp_emscripten/zlib
+  cd 3pp_emscripten/zlib || exit
   git checkout v1.3.1
   ZLIB_DIR=`pwd`
   emconfigure ./configure --static
@@ -116,7 +116,7 @@ fi
 
 if [ ! -d "3pp_emscripten/lz4" ]; then
   git clone https://github.com/lz4/lz4.git 3pp_emscripten/lz4
-  cd 3pp_emscripten/lz4
+  cd 3pp_emscripten/lz4 || exit
   git checkout v1.9.4
   LZ4_DIR=`pwd`
   emmake make -j$(nproc)
@@ -129,7 +129,7 @@ fi
 
 if [ ! -d "3pp_emscripten/libsodium" ]; then
   git clone https://github.com/jedisct1/libsodium 3pp_emscripten/libsodium
-  cd 3pp_emscripten/libsodium
+  cd 3pp_emscripten/libsodium || exit
   git checkout 1.0.18-RELEASE
   SODIUM_DIR=`pwd`
   emconfigure ./configure --disable-ssp
@@ -141,7 +141,7 @@ else
   echo Using compiled libsodium with emscripten at $SODIUM_DIR
 fi
 
-cd build
+cd build || exit
 
 emcmake cmake -DUSE_EMSCRIPTEN=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_VERBOSE_MAKEFILE:BOOL=ON \
 -DZLIB_FOUND=1 \