diff --git a/llvm-runtimes/libcxxabi/Manifest b/llvm-runtimes/libcxxabi/Manifest
index bf9c25406e41..3804fbbfcdf2 100644
--- a/llvm-runtimes/libcxxabi/Manifest
+++ b/llvm-runtimes/libcxxabi/Manifest
@@ -17,5 +17,7 @@ DIST llvm-project-21.1.6.src.tar.xz 158947864 BLAKE2B eeda7b9903ef59319ad22e5e3a
 DIST llvm-project-21.1.6.src.tar.xz.sig 119 BLAKE2B 2e3de87f4adb181740cfc8a5f8de3e6f4090f50d2f0dfa2670b27c0a6dde296b399ee017b5f6220aa80581a16c81afb5c96454d69dac8ce246713570470956b8 SHA512 637cc9f778f8303e80985469c3102573a9cf6264093b1a83fb494e34b5cb444f76cbb7d6d497d44b05250d56e25ec27dd9df685e0b78b23bb71e4bcd05a8facf
 DIST llvm-project-21.1.7.src.tar.xz 158956584 BLAKE2B dc9738fdde764d520f0e6d615295133a96833935b38239ea2ec6dffe72558d01332905fa265a55eb105ab4c4f88f37d5b3427126b1f7c788dc266add581cdf25 SHA512 ae30a53ed929df979849f7433bf705bc3d540aa9e12a02a175eb2483d1a56f9ca1203c9b67795f6e84cf2407c28d46d5d5351b290d8735adb5206103fee6f379
 DIST llvm-project-21.1.7.src.tar.xz.sig 438 BLAKE2B be4808a0888b088df0be4edaa7d49361dee717508d4438ad09c18b00752cd7a14ef56f5f18e3e4306a9ace95d9da7ed6904c998eb8a386577f21049bf5b6c0ce SHA512 d02b09c77abd537eb24d6d43470f962c80a9ec6ccc03ac0efc950d90dbdec5b94dd6abad18143890ff85cee2bdeb7bcf1dac2a576ffcab8ef053d8526417bdcc
+DIST llvm-project-21.1.8.src.tar.xz 158958576 BLAKE2B 0d3d4ee920f8e5db50e98152616f16004c74df0e7313cc86d893428fb7b1c875109988a5e40ea6f2e5d0fef53c7bfe2fc2b69e84807f6eb440b03afa1b228a36 SHA512 cae4c44e7bf678071723da63ad5839491d717a7233e7f4791aa408207f3ea42f52de939ad15189b112c02a0770f1bb8d59bae6ad31ef53417a6eea7770fe52ab
+DIST llvm-project-21.1.8.src.tar.xz.sig 119 BLAKE2B cffc1825f5778a3e3c128ec3e856ff6ee50687319d621cdf42e895abf67e05cc51cb7493308e2b506ab60dbdbaca7aa75eb9f78d91d42c81f9682a36f4042e9d SHA512 10f58eff58ed6e701d0f123b15e68c82ab8cbdf99b1c86c0d83e3b8553e90ea51055e30327e8e442ded57c8f503e2a2de9ee075e9c28b5ba815a0f8922f8671c
 DIST llvm-project-21c4c1502e3383988ba77eac75b13da7b9426957.tar.gz 254650569 BLAKE2B aaa8fffbe3b8ddcffa232c6cd078d33efc0f23453fd79b2ae71a0760b35da2ad17ffaed95d99c2548904468767d9f95af2ca4a59245e1ddf51a6612bda61cda4 SHA512 40a97c53cf7825b5c1e6867df74fa22e3b786a2ec9bcb478e1af0e6a165c582316c3c75b12f4704227b8e95cce91ab110acb10f2d8f30bc82319d6af4d201956
 DIST llvm-project-8401a8d0be7671fb5089f850a34dc92ad4a2eb12.tar.gz 254694831 BLAKE2B edac68e2b57124504262d68d1fabbb2161af023c2b9f96f304ce220e3d84249e2a2c1137c83bcfb15f6f082b68ef24a775150e5f435ec14d0f471c51ec438346 SHA512 a35f918fc3363df20fecac5820595060acd9fa0bce2cc3f696603192100a63ff4d31f6ba6ac98ad13f62b01c0789f3cce2ecbe4b9c0095d2bf02d2b24971d973
diff --git a/llvm-runtimes/libcxxabi/libcxxabi-21.1.8.ebuild b/llvm-runtimes/libcxxabi/libcxxabi-21.1.8.ebuild
new file mode 100644
index 000000000000..76793f80f5b7
--- /dev/null
+++ b/llvm-runtimes/libcxxabi/libcxxabi-21.1.8.ebuild
@@ -0,0 +1,150 @@
+# 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="Low level support for a standard C++ library"
+HOMEPAGE="https://libcxxabi.llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions || ( UoI-NCSA MIT )"
+SLOT="0"
+KEYWORDS="~amd64 ~arm ~arm64 ~loong ~riscv ~sparc ~x86 ~arm64-macos ~x64-macos"
+IUSE="+clang +static-libs test"
+REQUIRED_USE="test? ( clang )"
+RESTRICT="!test? ( test )"
+
+DEPEND="
+	${RDEPEND}
+	llvm-core/llvm:${LLVM_MAJOR}
+"
+BDEPEND="
+	clang? (
+		llvm-core/clang:${LLVM_MAJOR}
+		llvm-core/clang-linker-config:${LLVM_MAJOR}
+		llvm-runtimes/clang-rtlib-config:${LLVM_MAJOR}
+		llvm-runtimes/clang-unwindlib-config:${LLVM_MAJOR}
+	)
+	!test? (
+		${PYTHON_DEPS}
+	)
+	test? (
+		$(python_gen_any_dep 'dev-python/lit[${PYTHON_USEDEP}]')
+	)
+"
+
+LLVM_COMPONENTS=( runtimes libcxx{abi,} llvm/cmake cmake )
+LLVM_TEST_COMPONENTS=(
+	libc llvm/include/llvm/{Demangle,Testing} llvm/utils/llvm-lit
+)
+llvm.org_set_globals
+
+python_check_deps() {
+	use test || return 0
+	python_has_version "dev-python/lit[${PYTHON_USEDEP}]"
+}
+
+test_compiler() {
+	target_is_not_host && return
+	$(tc-getCXX) ${CXXFLAGS} ${LDFLAGS} "${@}" -o /dev/null -x c - \
+		<<<'int main() { return 0; }' &>/dev/null
+}
+
+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=${CTARGET}-clang-${LLVM_MAJOR}
+		local -x CXX=${CTARGET}-clang++-${LLVM_MAJOR}
+		strip-unsupported-flags
+
+		# The full clang configuration might not be ready yet. Use the partial
+		# configuration of components that libunwind depends on.
+		#
+		local flags=(
+			--config="${ESYSROOT}"/etc/clang/"${LLVM_MAJOR}"/gentoo-{rtlib,unwindlib,linker}.cfg
+		)
+		local -x CFLAGS="${CFLAGS} ${flags[@]}"
+		local -x CXXFLAGS="${CXXFLAGS} ${flags[@]}"
+		local -x LDFLAGS="${LDFLAGS} ${flags[@]}"
+	fi
+
+	local nostdlib_flags=( -nostdlib++ )
+	if ! test_compiler && test_compiler "${nostdlib_flags[@]}"; then
+		local -x LDFLAGS="${LDFLAGS} ${nostdlib_flags[*]}"
+		ewarn "${CXX} seems to lack stdlib, trying with ${nostdlib_flags[*]}"
+	fi
+
+	# link to compiler-rt
+	local use_compiler_rt=OFF
+	[[ $(tc-get-c-rtlib) == compiler-rt ]] && use_compiler_rt=ON
+
+	local libdir=$(get_libdir)
+	local mycmakeargs=(
+		-DLLVM_ROOT="${ESYSROOT}/usr/lib/llvm/${LLVM_MAJOR}"
+
+		-DCMAKE_CXX_COMPILER_TARGET="${CTARGET}"
+		-DPython3_EXECUTABLE="${PYTHON}"
+		-DLLVM_ENABLE_RUNTIMES="libcxxabi;libcxx"
+		-DLLVM_INCLUDE_TESTS=OFF
+		-DLLVM_LIBDIR_SUFFIX=${libdir#lib}
+		-DLIBCXXABI_ENABLE_SHARED=ON
+		-DLIBCXXABI_ENABLE_STATIC=$(usex static-libs)
+		-DLIBCXXABI_INCLUDE_TESTS=$(usex test)
+		-DLIBCXXABI_USE_COMPILER_RT=${use_compiler_rt}
+
+		# upstream is omitting standard search path for this
+		# probably because gcc & clang are bundling their own unwind.h
+		-DLIBCXXABI_LIBUNWIND_INCLUDES="${EPREFIX}"/usr/include
+		# this is broken with standalone builds, and also meaningless
+		-DLIBCXXABI_USE_LLVM_UNWINDER=OFF
+
+		-DLIBCXX_ENABLE_SHARED=ON
+		-DLIBCXX_ENABLE_STATIC=OFF
+		-DLIBCXX_CXX_ABI=libcxxabi
+		-DLIBCXX_ENABLE_ABI_LINKER_SCRIPT=OFF
+		-DLIBCXX_HAS_MUSL_LIBC=$(llvm_cmake_use_musl)
+		-DLIBCXX_HAS_GCC_S_LIB=OFF
+		-DLIBCXX_INCLUDE_BENCHMARKS=OFF
+		-DLIBCXX_INCLUDE_TESTS=OFF
+	)
+	if is_crosspkg; then
+		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="${PYTHON}"
+		)
+	fi
+	cmake_src_configure
+}
+
+multilib_src_compile() {
+	cmake_build cxxabi
+}
+
+multilib_src_test() {
+	local -x LIT_PRESERVES_TMP=1
+	cmake_build check-cxxabi
+}
+
+multilib_src_install() {
+	DESTDIR="${D}" cmake_build install-cxxabi
+}