diff --git a/Formula/llvm/libc++2.rb b/Formula/llvm/libc++2.rb
new file mode 100644
index 00000000..b6c860a0
--- /dev/null
+++ b/Formula/llvm/libc++2.rb
@@ -0,0 +1,69 @@
+class Libcxx2 < Formula
+  desc "LLVM C++ standard library (unstable ABI)"
+  homepage "https://libcxx.llvm.org/"
+  url "https://github.com/llvm/llvm-project/releases/download/llvmorg-20.1.0/llvm-project-20.1.0.src.tar.xz"
+  sha256 "4579051e3c255fb4bb795d54324f5a7f3ef79bd9181e44293d7ee9a7f62aad9a"
+  license "Apache-2.0" => { with: "LLVM-exception" }
+
+  bottle do
+    root_url "https://github.com/paperchalice/homebrew-private/releases/download/libc++-19.1.5"
+    sha256 cellar: :any, ventura: "8202d54aeb93ffaecd47aec1a9a3b14f2dd3e1c78da52c400ae8bee12b07f652"
+  end
+
+  depends_on "clang" => :build
+  depends_on "cmake" => :build
+
+  depends_on "libc++abi"
+  depends_on "tzdb"
+  depends_on "unwind"
+
+  def install
+    inreplace "libcxx/src/experimental/tzdb.cpp" do |s|
+      tzdb = Formula["tzdb"]
+      s.gsub! "__linux__", "__APPLE__"
+      s.gsub! "/usr/share/zoneinfo/", "#{tzdb.share}/zoneinfo/"
+    end
+
+    clang = Formula["clang"]
+    ENV["CC"] = clang.bin/"clang"
+    ENV["CXX"] = clang.bin/"clang++"
+
+    libunwind = Formula["unwind"]
+    libcxxabi = Formula["libc++abi"]
+    rpaths = [rpath, libunwind.opt_lib, libcxxabi.opt_lib]
+    cmake_args = std_cmake_args+ %W[
+      -D CMAKE_INSTALL_RPATH=#{rpaths.join(";")}
+      -D LLVM_ENABLE_RUNTIMES=libcxx;libcxxabi;libunwind
+      -D LIBCXX_INSTALL_MODULES=ON
+      -D LIBCXX_ENABLE_TIME_ZONE_DATABASE=ON
+      -D LIBCXX_ABI_UNSTABLE=ON
+
+      -S runtimes
+      -B build
+    ]
+
+    system "cmake", *cmake_args
+    system "cmake", "--build", "build", "--target", "install-cxx-stripped"
+  end
+
+  test do
+    (testpath/"main.cpp").write <<~EOS
+      #include <iostream>
+      #include <vector>
+      int main() {
+        std::vector<int> vec = {1, 2, 3};
+        for(const auto &i : vec) {
+          std::cout << vec[0] << std::endl;
+        }
+        return 0;
+      }
+    EOS
+    args = %W[
+      -std=c++17
+      -nostdlibinc
+      -I#{include}/c++/v1
+      -L#{lib}
+    ]
+    system ENV.cxx, "main.cpp", *args
+  end
+end