diff --git a/llvm-runtimes/libcxx/Manifest b/llvm-runtimes/libcxx/Manifest
index 016c1cb37f48d..991c8b7fa5c92 100644
--- a/llvm-runtimes/libcxx/Manifest
+++ b/llvm-runtimes/libcxx/Manifest
@@ -11,6 +11,7 @@ DIST llvm-project-18.1.8.src.tar.xz.sig 566 BLAKE2B 6ab0efc5b38d4483f4e32e8b8577
 DIST llvm-project-19.1.7.src.tar.xz 141249332 BLAKE2B 1259ed7f9aca7b35e89d818befdee20fd8bed4d2dc2c2c6f6f56451fd43d35ac03a0a5a406e142d22b25137999dc5b17471c196f8fcf79f20a8296832d900f6d SHA512 c7d63286d662707a9cd54758c9e3aaf52794a91900c484c4a6efa62d90bc719d5e7a345e4192feeb0c9fd11c82570d64677c781e5be1d645556b6aa018e47ec8
 DIST llvm-project-19.1.7.src.tar.xz.sig 438 BLAKE2B 4015140f4ba77de45039bdbdfbaf6f30e75705123d067ea97175d91d7a5b6a75008df01d99ae7aa16aaa3b101f3f41e38d01f04158f95a261d617b3ede0254cd SHA512 195797b06ac80a742e0ccbc03a50dc06dd2e04377d783d5474e3e72c5a75203b60292b047929312a411d22b137a239943fba414a4d136a2be14cbff978eb6bda
 DIST llvm-project-190fcc28af585cb06480b026afd14ed87b18adb8.tar.gz 243483242 BLAKE2B f53d743ca332dfffe1f98d51f0528e14b61e4c11904ec20c4b4c9b285f8ca7eb25eb2ce8549e21566e63ab393697c74acd4a41fddc7bab282535aa8ccf9195da SHA512 b6bcf8647f35fee209fbd8a8c297f7d89f1aac9cac4e3c62abd73171350c4c7a98572ccd175ca0a8fce8d2fe00bf5cfbeea329689b687ab6261586e894397150
+DIST llvm-project-1c7720ef78dc5eb9196d6c178afe03b60f201b78.tar.gz 245239122 BLAKE2B 74342ef3a8105915201f6260aa8c633ccd67821894d33605d82ca0f02d0d0766fe3198e834c4c5cae8123d911b5a20849c04ea02aea52f57f8d1a09e17c18199 SHA512 10a63bdf7d790c5964274414dc01b480a976318f27b5807ca47d9149b97106530264a75930c689ca7cc417de3df44142280cd92559ff7873190f1045d79e7856
 DIST llvm-project-20.1.7.src.tar.xz 147245448 BLAKE2B f7c57d1eba4e97e875b624dec3fb1b261a0203de7200366de5b3edcfbca2a170c41df46e91cd9cb78ae2af66120aef95334f5eb9628a1489e921c6bdf4cccfe8 SHA512 c2dbf6a468a8152409db7ff52902ecf8768a1d0328e386999f4f3672613903e1c10bddbba66b8553a6222952f8edb66266947f1fb21d0b09ae741e6249b6d1fa
 DIST llvm-project-20.1.7.src.tar.xz.sig 566 BLAKE2B 72ce2a18c211cfce9581a9e3e71f1c55cf18672aa355267581220e1a89e3327f9e16107970b69bb8f10f390baa5e286487bdc4cc0a7d9155ec13a4977cd3f472 SHA512 eff885059d547f57b98bda1fc9631f716ca6c650cd48203d9ed5443a6afb9a2d4d91d3f5c8618e307c0a44b3040bce61fdc6bce965073adc537655755d9f2112
 DIST llvm-project-20.1.8.src.tar.xz 147242952 BLAKE2B 7657ac0b26acc5affb1bfc91b912ade3191c5d77f3979d5a80d5f6ce52f56a7d1c448bd257398390bf10838f02faa6f3ece37a7327cced69d165ec2e2e699316 SHA512 f330e72e6a1da468569049437cc0ba7a41abb816ccece7367189344f7ebfef730f4788ac7af2bef0aa8a49341c15ab1d31e941ffa782f264d11fe0dc05470773
diff --git a/llvm-runtimes/libcxx/libcxx-22.0.0_pre20250815.ebuild b/llvm-runtimes/libcxx/libcxx-22.0.0_pre20250815.ebuild
new file mode 100644
index 0000000000000..cb170c03ff836
--- /dev/null
+++ b/llvm-runtimes/libcxx/libcxx-22.0.0_pre20250815.ebuild
@@ -0,0 +1,251 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+PYTHON_COMPAT=( python3_{11..14} )
+inherit cmake-multilib crossdev flag-o-matic llvm.org llvm-utils
+inherit python-any-r1 toolchain-funcs
+
+DESCRIPTION="New implementation of the C++ standard library, targeting C++11"
+HOMEPAGE="https://libcxx.llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions || ( UoI-NCSA MIT )"
+SLOT="0"
+IUSE="+clang +libcxxabi +static-libs test"
+REQUIRED_USE="test? ( clang )"
+RESTRICT="!test? ( test )"
+
+RDEPEND="
+	libcxxabi? (
+		~llvm-runtimes/libcxxabi-${PV}[static-libs?,${MULTILIB_USEDEP}]
+	)
+	!libcxxabi? ( >=sys-devel/gcc-4.7:=[cxx] )
+"
+DEPEND="
+	${RDEPEND}
+	llvm-core/llvm:${LLVM_MAJOR}
+"
+BDEPEND="
+	clang? (
+		llvm-core/clang:${LLVM_MAJOR}
+	)
+	!test? (
+		${PYTHON_DEPS}
+	)
+	test? (
+		dev-debug/gdb[python]
+		$(python_gen_any_dep 'dev-python/lit[${PYTHON_USEDEP}]')
+	)
+"
+
+LLVM_COMPONENTS=(
+	runtimes libcxx{,abi} libc llvm/{cmake,utils/llvm-lit} cmake
+)
+llvm.org_set_globals
+
+python_check_deps() {
+	use test || return 0
+	python_has_version "dev-python/lit[${PYTHON_USEDEP}]"
+}
+
+pkg_setup() {
+	python-any-r1_pkg_setup
+
+	if ! use libcxxabi && ! tc-is-gcc ; then
+		eerror "To build ${PN} against libsupc++, you have to use gcc. Other"
+		eerror "compilers are not supported. Please set CC=gcc and CXX=g++"
+		eerror "and try again."
+		die
+	fi
+}
+
+test_compiler() {
+	$(tc-getCXX) ${CXXFLAGS} ${LDFLAGS} "${@}" -o /dev/null -x c++ - \
+		<<<'int main() { return 0; }' &>/dev/null
+}
+
+src_configure() {
+	local install_prefix=${EPREFIX}
+	is_crosspkg && install_prefix+=/usr/${CTARGET}
+
+	# note: we need to do this before multilib kicks in since it will
+	# alter the CHOST
+	local cxxabi cxxabi_incs
+	if use libcxxabi; then
+		cxxabi=system-libcxxabi
+		cxxabi_incs="${install_prefix}/usr/include/c++/v1"
+	else
+		local gcc_inc="${EPREFIX}/usr/lib/gcc/${CHOST}/$(gcc-fullversion)/include/g++-v$(gcc-major-version)"
+		cxxabi=libsupc++
+		cxxabi_incs="${gcc_inc};${gcc_inc}/${CHOST}"
+	fi
+
+	multilib-minimal_src_configure
+}
+
+multilib_src_configure() {
+	# Workaround for bgo #961153.
+	# TODO: Fix the multilib.eclass, so it sets CTARGET properly.
+	if ! is_crosspkg; then
+		export CTARGET=${CHOST}
+	fi
+
+	if use clang; then
+		llvm_prepend_path -b "${LLVM_MAJOR}"
+		local -x CC=${CTARGET}-clang
+		local -x CXX=${CTARGET}-clang++
+		strip-unsupported-flags
+	fi
+
+	# link to compiler-rt
+	local use_compiler_rt=OFF
+	[[ $(tc-get-c-rtlib) == compiler-rt ]] && use_compiler_rt=ON
+
+	# Scenarios to consider:
+	#
+	# 1. Compiler test works with the default flags.
+	# 2. There is a runtime library, but no stdlib. In that case, leave the
+	#    LDFLAGS untouched, since there is no self-dependency in libc++.
+	# 3. There is no runtime library nor stdlib. In that case, overwrite the
+	#    LDFLAGS.
+	local nostdlib_flags=( -nostdlib --rtlib=compiler-rt -lc )
+	local nort_flags=( -nodefaultlibs -lc )
+	if ! test_compiler && ! test_compiler "${nostdlib_flags[@]}"; then
+		if test_compiler "${nort_flags[@]}"; then
+			local -x LDFLAGS="${LDFLAGS} ${nort_flags[*]}"
+			ewarn "${CXX} seems to lack runtime, trying with ${nort_flags[*]}"
+		fi
+	fi
+
+	local libdir=$(get_libdir)
+	local mycmakeargs=(
+		-DLLVM_ROOT="${ESYSROOT}/usr/lib/llvm/${LLVM_MAJOR}"
+
+		-DCMAKE_CXX_COMPILER_TARGET="${CTARGET}"
+		-DPython3_EXECUTABLE="${PYTHON}"
+		-DLLVM_ENABLE_RUNTIMES=libcxx
+		-DLLVM_INCLUDE_TESTS=OFF
+		-DLLVM_LIBDIR_SUFFIX=${libdir#lib}
+
+		-DLIBCXX_ENABLE_SHARED=ON
+		-DLIBCXX_ENABLE_STATIC=$(usex static-libs)
+		-DLIBCXX_CXX_ABI=${cxxabi}
+		-DLIBCXX_CXX_ABI_INCLUDE_PATHS=${cxxabi_incs}
+		# we're using our own mechanism for generating linker scripts
+		-DLIBCXX_ENABLE_ABI_LINKER_SCRIPT=OFF
+		-DLIBCXX_HAS_MUSL_LIBC=$(llvm_cmake_use_musl)
+		-DLIBCXX_INCLUDE_BENCHMARKS=OFF
+		-DLIBCXX_INCLUDE_TESTS=$(usex test)
+		-DLIBCXX_INSTALL_MODULES=ON
+		-DLIBCXX_USE_COMPILER_RT=${use_compiler_rt}
+		# this is broken with standalone builds, and also meaningless
+		-DLIBCXXABI_USE_LLVM_UNWINDER=OFF
+	)
+	if is_crosspkg; then
+		# Needed to target built libc headers
+		local -x CFLAGS="${CFLAGS} -isystem ${ESYSROOT}/usr/${CTARGET}/usr/include"
+		mycmakeargs+=(
+			# Without this, the compiler will compile a test program
+			# and fail due to no builtins.
+			-DCMAKE_C_COMPILER_WORKS=1
+			-DCMAKE_CXX_COMPILER_WORKS=1
+			# Install inside the cross sysroot.
+			-DCMAKE_INSTALL_PREFIX="${EPREFIX}/usr/${CTARGET}/usr"
+		)
+	fi
+	if use test; then
+		mycmakeargs+=(
+			-DLLVM_EXTERNAL_LIT="${EPREFIX}/usr/bin/lit"
+			-DLLVM_LIT_ARGS="$(get_lit_flags)"
+			-DPython3_EXECUTABLE="${PYTHON}"
+		)
+	fi
+	cmake_src_configure
+}
+
+multilib_src_compile() {
+	cmake_src_compile
+	if [[ ${CHOST} != *-darwin* ]] ; then
+		gen_shared_ldscript
+		use static-libs && gen_static_ldscript
+	fi
+}
+
+multilib_src_test() {
+	local -x LIT_PRESERVES_TMP=1
+	cmake_build install-cxx-test-suite-prefix
+	cp "${BUILD_DIR}"/{lib,libcxx/test-suite-install/$(get_libdir)}/libc++_shared.so || die
+	if use static-libs; then
+		cp "${BUILD_DIR}"/{lib,libcxx/test-suite-install/$(get_libdir)}/libc++_static.a || die
+	fi
+	cmake_build check-cxx
+}
+
+multilib_src_install() {
+	cmake_src_install
+	# since we've replaced libc++.{a,so} with ldscripts, now we have to
+	# install the extra symlinks
+	if [[ ${CHOST} != *-darwin* ]] ; then
+		is_crosspkg && into /usr/${CTARGET}
+		dolib.so lib/libc++_shared.so
+		use static-libs && dolib.a lib/libc++_static.a
+	fi
+
+	local install_prefix=
+	is_crosspkg && install_prefix=/usr/${CTARGET}
+	insinto "${install_prefix}/usr/share/libc++/gdb"
+	doins ../libcxx/utils/gdb/libcxx/printers.py
+
+	local lib_version=$(sed -n -e 's/^LIBCXX_LIBRARY_VERSION:STRING=//p' CMakeCache.txt || die)
+	[[ -n ${lib_version} ]] || die "Could not determine LIBCXX_LIBRARY_VERSION from CMakeCache.txt"
+
+	insinto "${install_prefix}/usr/share/gdb/auto-load/usr/$(get_libdir)"
+	newins - "libc++.so.${lib_version}-gdb.py" <<-EOF
+		__import__("sys").path.insert(0, "${EPREFIX}/usr/share/libc++/gdb")
+		__import__("printers").register_libcxx_printer_loader()
+	EOF
+}
+
+# Usage: deps
+gen_ldscript() {
+	local output_format
+	output_format=$($(tc-getCC) ${CFLAGS} ${LDFLAGS} -Wl,--verbose 2>&1 | sed -n 's/^OUTPUT_FORMAT("\([^"]*\)",.*/\1/p')
+	[[ -n ${output_format} ]] && output_format="OUTPUT_FORMAT ( ${output_format} )"
+
+	cat <<-END_LDSCRIPT
+/* GNU ld script
+   Include missing dependencies
+*/
+${output_format}
+GROUP ( $@ )
+END_LDSCRIPT
+}
+
+gen_static_ldscript() {
+	# Move it first.
+	mv lib/libc++{,_static}.a || die
+	# Generate libc++.a ldscript for inclusion of its dependencies so that
+	# clang++ -stdlib=libc++ -static works out of the box.
+	local deps=(
+		libc++_static.a
+		$(usex libcxxabi libc++abi.a libsupc++.a)
+	)
+	# On Linux/glibc it does not link without libpthread or libdl. It is
+	# fine on FreeBSD.
+	use elibc_glibc && deps+=( libpthread.a libdl.a )
+
+	gen_ldscript "${deps[*]}" > lib/libc++.a || die
+}
+
+gen_shared_ldscript() {
+	# Move it first.
+	mv lib/libc++{,_shared}.so || die
+	local deps=(
+		libc++_shared.so
+		# libsupc++ doesn't have a shared version
+		$(usex libcxxabi libc++abi.so libsupc++.a)
+	)
+
+	gen_ldscript "${deps[*]}" > lib/libc++.so || die
+}