diff --git a/dev-libs/boost/boost-1.90.0-r2.ebuild b/dev-libs/boost/boost-1.90.0-r2.ebuild
new file mode 100644
index 0000000000000..c35327225d902
--- /dev/null
+++ b/dev-libs/boost/boost-1.90.0-r2.ebuild
@@ -0,0 +1,478 @@
+# Copyright 1999-2026 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+# Keep an eye on releases: https://www.boost.org/releases/
+
+PYTHON_COMPAT=( python3_{11..14} )
+
+inherit dot-a edo flag-o-matic multiprocessing python-r1 toolchain-funcs multilib-minimal
+
+MY_PV="$(ver_rs 1- _)"
+
+DESCRIPTION="Boost Libraries for C++"
+HOMEPAGE="https://www.boost.org/"
+SRC_URI="https://archives.boost.io/release/${PV}/source/boost_${MY_PV}.tar.bz2"
+S="${WORKDIR}/${PN}_${MY_PV}"
+
+LICENSE="Boost-1.0"
+SLOT="0/${PV}"
+KEYWORDS="~alpha amd64 arm arm64 ~hppa ~loong ~m68k ~mips ppc ppc64 ~riscv ~s390 ~sparc x86 ~arm64-macos ~x64-macos ~x64-solaris"
+IUSE="bzip2 +context debug doc icu lzma +nls mpi numpy python +stacktrace test test-full tools zlib zstd"
+REQUIRED_USE="
+	python? ( ${PYTHON_REQUIRED_USE} )
+	test-full? ( test )
+"
+RESTRICT="!test? ( test )"
+
+RDEPEND="
+	bzip2? ( app-arch/bzip2:=[${MULTILIB_USEDEP}] )
+	icu? ( dev-libs/icu:=[${MULTILIB_USEDEP}] )
+	!icu? ( virtual/libiconv[${MULTILIB_USEDEP}] )
+	lzma? ( app-arch/xz-utils:=[${MULTILIB_USEDEP}] )
+	mpi? ( virtual/mpi[${MULTILIB_USEDEP},threads] )
+	python? (
+		${PYTHON_DEPS}
+		numpy? ( dev-python/numpy:=[${PYTHON_USEDEP}] )
+	)
+	zlib? ( virtual/zlib:=[${MULTILIB_USEDEP}] )
+	zstd? ( app-arch/zstd:=[${MULTILIB_USEDEP}] )"
+DEPEND="${RDEPEND}"
+BDEPEND=">=dev-build/b2-5.1.0"
+
+PATCHES=(
+	"${FILESDIR}"/${PN}-1.88.0-disable_icu_rpath.patch
+	"${FILESDIR}"/${PN}-1.88.0-build-auto_index-tool.patch
+	"${FILESDIR}"/${PN}-1.88.0-algorithm-reverse_copy.patch
+	"${FILESDIR}"/${PN}-1.88.0-beast-network-sandbox.patch
+	"${FILESDIR}"/${PN}-1.88.0-bind-no-Werror.patch
+	"${FILESDIR}"/${PN}-1.88.0-range-any_iterator.patch
+	"${FILESDIR}"/${PN}-1.88.0-system-crashing-test.patch
+	"${FILESDIR}"/${PN}-1.88.0-yap-cstdint.patch
+	# https://github.com/boostorg/dll/issues/108
+	"${FILESDIR}"/${PN}-1.89.0-dll-no-lto.patch
+	"${FILESDIR}"/${PN}-1.89.0-graph-remove-system-dependency.patch
+	"${FILESDIR}"/${PN}-1.89.0-predef-include-path.patch
+	"${FILESDIR}"/${PN}-1.89.0-python-exclude-broken-tests.patch
+	"${FILESDIR}"/${PN}-1.89.0-unordered-no-tbb.patch
+	"${FILESDIR}"/${PN}-1.90.0-cobalt.patch
+	"${FILESDIR}"/${PN}-1.90.0-msm-std.patch
+	"${FILESDIR}"/${PN}-1.90.0-unsigned-char-EOF.patch
+)
+
+create_user-config.jam() {
+	local user_config_jam="${BUILD_DIR}"/user-config.jam
+	if [[ -s ${user_config_jam} ]]; then
+		einfo "${user_config_jam} already exists, skipping configuration"
+		return
+	else
+		einfo "Creating configuration in ${user_config_jam}"
+	fi
+
+	local compiler compiler_version compiler_executable="$(tc-getCXX)"
+	compiler="gcc"
+	compiler_version="$(gcc-version)"
+
+	if use mpi; then
+		local mpi_configuration="using mpi ;"
+	fi
+
+	cat > "${user_config_jam}" <<- __EOF__ || die
+		using ${compiler} : ${compiler_version} : ${compiler_executable} : <cflags>"${CPPFLAGS} ${CFLAGS}" <cxxflags>"${CPPFLAGS} ${CXXFLAGS}" <linkflags>"${LDFLAGS}" <archiver>"$(tc-getAR)" <ranlib>"$(tc-getRANLIB)" ;
+		${mpi_configuration}
+	__EOF__
+
+	if multilib_native_use python; then
+		append_to_user_config() {
+			local py_config
+			if tc-is-cross-compiler; then
+				py_config="using python : ${EPYTHON#python} : : ${ESYSROOT}/usr/include/${EPYTHON} : ${ESYSROOT}/usr/$(get_libdir) ;"
+			else
+				py_config="using python : ${EPYTHON#python} : ${PYTHON} : $(python_get_includedir) ;"
+			fi
+			echo "${py_config}" >> "${user_config_jam}" || die
+		}
+		python_foreach_impl append_to_user_config
+	fi
+
+	if multilib_native_use python && use numpy; then
+		einfo "Enabling support for NumPy extensions in Boost.Python"
+	else
+		einfo "Disabling support for NumPy extensions in Boost.Python"
+
+		# Boost.Build does not allow for disabling of numpy
+		# extensions, thereby leading to automagic numpy
+		# https://github.com/boostorg/python/issues/111#issuecomment-280447482
+		sed \
+			-e 's/\[ unless \[ python\.numpy \] : <build>no \]/<build>no/g' \
+			-i "${BUILD_DIR}"/libs/python/build/Jamfile || die
+	fi
+}
+
+pkg_setup() {
+	# Bail out on unsupported build configuration, bug #456792
+	if [[ -f "${EROOT}"/etc/site-config.jam ]]; then
+		if ! grep -q 'gentoo\(debug\|release\)' "${EROOT}"/etc/site-config.jam; then
+			eerror "You are using custom ${EROOT}/etc/site-config.jam without defined gentoorelease/gentoodebug targets."
+			eerror "Boost can not be built in such configuration."
+			eerror "Please, either remove this file or add targets from ${EROOT}/usr/share/boost-build/site-config.jam to it."
+			die "Unsupported target in ${EROOT}/etc/site-config.jam"
+		fi
+	fi
+}
+
+src_prepare() {
+	default
+	multilib_copy_sources
+}
+
+ejam() {
+	create_user-config.jam
+
+	local b2_opts=( "--user-config=${BUILD_DIR}/user-config.jam" )
+	if multilib_native_use python; then
+		append_to_b2_opts() {
+			b2_opts+=( python="${EPYTHON#python}" )
+		}
+		python_foreach_impl append_to_b2_opts
+	else
+		b2_opts+=( --without-python )
+	fi
+	b2_opts+=( "$@" )
+
+	echo b2 "${b2_opts[@]}" >&2
+	b2 "${b2_opts[@]}"
+}
+
+src_configure() {
+	# -Werror=odr
+	# https://bugs.gentoo.org/943975
+	# https://github.com/boostorg/quickbook/issues/27
+	# https://github.com/boostorg/spirit/issues/800
+	#
+	# Tests also fail:
+	# https://bugs.gentoo.org/956660
+	# https://github.com/boostorg/smart_ptr/issues/121
+	# https://github.com/boostorg/thread/issues/415
+	filter-lto
+
+	lto-guarantee-fat
+
+	# Workaround for too many parallel processes requested, bug #506064
+	[[ "$(makeopts_jobs)" -gt 64 ]] && MAKEOPTS="${MAKEOPTS} -j64"
+
+	# We don't want to end up with -L/usr/lib on our linker lines
+	# which then gives us lots of
+	#   skipping incompatible /usr/lib/libc.a when searching for -lc
+	# warnings
+	[[ -n ${ESYSROOT} ]] && local icuarg="-sICU_PATH=${ESYSROOT}/usr"
+
+	OPTIONS=(
+		$(usex debug gentoodebug gentoorelease)
+		"-j$(makeopts_jobs)"
+		-q
+		-d+2
+		pch=off
+		$(usex icu "${icuarg}" '--disable-icu boost.locale.icu=off')
+		$(usev !mpi --without-mpi)
+		$(usev !nls --without-locale)
+		$(usev !context '--without-context --without-coroutine --without-fiber')
+		$(usev !stacktrace --without-stacktrace)
+		--boost-build="${BROOT}"/usr/share/b2/src
+		--layout=system
+		# building with threading=single is currently not possible
+		# https://svn.boost.org/trac/boost/ticket/7105
+		threading=multi
+		link=shared
+		# this seems to be the only way to disable compression algorithms
+		# https://www.boost.org/doc/libs/1_70_0/libs/iostreams/doc/installation.html#boost-build
+		-sNO_BZIP2=$(usex bzip2 0 1)
+		-sNO_LZMA=$(usex lzma 0 1)
+		-sNO_ZLIB=$(usex zlib 0 1)
+		-sNO_ZSTD=$(usex zstd 0 1)
+		boost.stacktrace.from_exception=off
+	)
+
+	if [[ ${CHOST} == *-darwin* ]]; then
+		# We need to add the prefix, and in two cases this exceeds, so prepare
+		# for the largest possible space allocation.
+		append-ldflags -Wl,-headerpad_max_install_names
+	fi
+
+	# Use C++17 globally as of 1.80
+	append-cxxflags -std=c++17
+
+	if [[ ${CHOST} != *-darwin* ]]; then
+		# On modern macOS, file I/O is already 64-bit by default,
+		# there's no support for special options like O_LARGEFILE.
+		# Thus, LFS must be disabled.
+		#
+		# On other systems, we need to enable LFS explicitly for 64-bit
+		# offsets on 32-bit hosts (#894564)
+		append-lfs-flags
+	fi
+}
+
+multilib_src_compile() {
+	ejam \
+		--prefix="${EPREFIX}"/usr \
+		"${OPTIONS[@]}" || die
+
+	if multilib_native_use tools; then
+		pushd tools >/dev/null || die
+		ejam \
+			--prefix="${EPREFIX}"/usr \
+			"${OPTIONS[@]}" \
+			|| die "Building of Boost tools failed"
+		popd >/dev/null || die
+	fi
+}
+
+multilib_src_test() {
+	##
+	## Test exclusions
+	##
+
+	# The following libraries do not compile or fail their tests:
+	local libs_excluded=(
+		# it seems tests are no longer built
+		"callable_traits"
+		# test output comparison failure
+		"config"
+		# undefined reference to `boost::math::concepts::real_concept boost::math::bernoulli_b2n<boost::math::concepts::real_concept>(int)
+		"math"
+		# In function 'PyObject* boost::parameter::python::aux::unspecified_type()':
+		#  /usr/include/python3.13/object.h:339:30: error: lvalue required as left operand of assignment
+		#  #define Py_TYPE(ob) Py_TYPE(_PyObject_CAST(ob))
+		#                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~
+		"parameter_python"
+		# scope/lambda_tests22.cpp(27): test 'x == 1' failed in function 'int main()'
+		"phoenix"
+		# vec_access.hpp:95:223: error: static assertion failed: Boost QVM static assertion failure
+		"qvm"
+		# Processing file ../boost_1_89_0/libs/regex/example/../include/boost/regex/v5/regex_iterator.hpp
+		# terminate called after throwing an instance of 'std::length_error'
+		#   what():  basic_string::_M_create
+		"regex"
+		# in function `boost::archive::tmpnam(char*)': test_array.cpp:(.text+0x108):
+		#   undefined reference to `boost::filesystem::detail::unique_path(...)'
+		"serialization"
+		# TuTestMain.cpp(22) fatal error: in "test_main_caller( argc_ argv )":
+		#   std::runtime_error: Event was not consumed!
+		"statechart"
+		# t_5_007.cpp(22): error: could not find include file: boost/version.hpp
+		"wave"
+	)
+
+	if ! use mpi; then
+		# graph_parallel tries to use MPI even with use=-mpi
+		local no_mpi=( "mpi" "graph_parallel" )
+		einfo "Disabling tests due to USE=-mpi: ${no_mpi[@]}"
+		libs_excluded+=( ${no_mpi[@]} )
+	fi
+
+	if ! use test-full; then
+		# passes its tests but takes a very long time to build
+		local no_full=( "geometry" "multiprecision" )
+		einfo "Disabling expensive tests due to USE=-test-full: ${no_full[@]}"
+		libs_excluded+=( ${no_full[@]} )
+	fi
+
+	einfo "Skipping the following tests: ${libs_excluded[@]}"
+
+	##
+	## Find and run tests
+	##
+
+	# Prepare to find libraries but without exclusions
+	local excluded findlibs="find ${BUILD_DIR}/libs -maxdepth 1 -mindepth 1 -type d "
+	for excluded in ${libs_excluded[@]}; do
+	   findlibs+="-not -name ${excluded} "
+	done
+
+	# Must come as last argument
+	findlibs+="-print0"
+
+	# Collect libraries to test, with full path.
+	# The list is then sorted to provide predictable execution order,
+	# which would otherwise depend on the file system.
+	local libs
+	readarray -td '' libs < <(${findlibs})
+	readarray -td '' libs < <(printf '%s\0' "${libs[@]}" | sort -z)
+
+	# Build the list of test names we are about to run
+	local lib_names
+	for lib in ${libs[@]}; do
+		lib_names+=("${lib##*/}")
+	done
+
+	# Create custom options for tests based on the build settings
+	TEST_OPTIONS=("${OPTIONS[@]}")
+
+	# Dial down log output - the full b2 command used to compile & run
+	# a test suite will be printed by ejam and can be used to build
+	# and run the tests in a test suite's directory.
+	TEST_OPTIONS=("${TEST_OPTIONS[@]/-d+2/-d0}")
+
+	# Finally build & run all test suites
+	einfo "Running the following tests: ${lib_names[*]}"
+
+	local failed_tests=()
+	for lib in "${libs[@]}"; do
+		# Skip libraries without test directory
+		[[ ! -d "${lib}/test" ]] && continue
+
+		# Move into library test dir & run all tests
+		pushd "${lib}/test" >/dev/null || die
+		nonfatal edob -m "Running tests in: $(pwd)" ejam --prefix="${EPREFIX}"/usr "${TEST_OPTIONS[@]}" || failed_tests+=( "${lib}" )
+		popd >/dev/null || die
+	done
+
+	if (( ${#failed_tests[@]} )); then
+		eerror "Failed tests. Printing summary."
+		local failed_test
+		for failed_test in "${failed_tests[@]}" ; do
+			eerror "Failed test: ${failed_test}"
+		done
+		die "Tests failed."
+	fi
+}
+
+multilib_src_install() {
+	ejam \
+		--prefix="${ED}"/usr \
+		--includedir="${ED}"/usr/include \
+		--libdir="${ED}"/usr/$(get_libdir) \
+		"${OPTIONS[@]}" install || die "Installation of Boost libraries failed"
+
+	if multilib_native_use tools; then
+		dobin dist/bin/*
+
+		insinto /usr/share
+		doins -r dist/share/boostbook
+	fi
+
+	# boost's build system truely sucks for not having a destdir.  Because for
+	# this reason we are forced to build with a prefix that includes the
+	# DESTROOT, dynamic libraries on Darwin end messed up, referencing the
+	# DESTROOT instread of the actual EPREFIX.  There is no way out of here
+	# but to do it the dirty way of manually setting the right install_names.
+	if [[ ${CHOST} == *-darwin* ]]; then
+		einfo "Working around completely broken build-system(tm)"
+		local d
+		for d in "${ED}"/usr/lib/*.dylib; do
+			if [[ -f ${d} ]]; then
+				# fix the "soname"
+				ebegin "  correcting install_name of ${d#${ED}}"
+				install_name_tool -id "/${d#${D}}" "${d}"
+				eend $?
+				# fix references to other libs
+				# these paths look like this:
+				# bin.v2/libs/thread/build/gcc-12.1/gentoorelease/pch-off/
+				#  threadapi-pthread/threading-multi/visibility-hidden/
+				#  libboost_thread.dylib
+				refs=$(otool -XL "${d}" | \
+					sed -e '1d' -e 's/^\t//' | \
+					grep "libboost_" | \
+					cut -f1 -d' ')
+				local r
+				for r in ${refs}; do
+					# strip path prefix from references, so we obtain
+					# something like libboost_thread.dylib.
+					local r_basename=${r##*/}
+
+					ebegin "    correcting reference to ${r_basename}"
+					install_name_tool -change \
+						"${r}" \
+						"${EPREFIX}/usr/lib/${r_basename}" \
+						"${d}"
+					eend $?
+				done
+			fi
+		done
+	fi
+}
+
+multilib_src_install_all() {
+	if ! use numpy; then
+		rm -r "${ED}"/usr/include/boost/python/numpy* || die
+	fi
+
+	if use python; then
+		if use mpi; then
+			move_mpi_py_into_sitedir() {
+				python_moduleinto boost
+
+				python_domodule "${ED}"/usr/$(get_libdir)/boost-${EPYTHON}/mpi.so
+				rm -r "${ED}"/usr/$(get_libdir)/boost-${EPYTHON} || die
+
+				python_optimize
+			}
+			python_foreach_impl move_mpi_py_into_sitedir
+		else
+			rm -r "${ED}"/usr/include/boost/mpi/python* || die
+		fi
+	else
+		rm -r "${ED}"/usr/include/boost/{python*,mpi/python*,parameter/aux_/python,parameter/python*} || die
+	fi
+
+	if ! use nls; then
+		rm -r "${ED}"/usr/include/boost/locale || die
+	fi
+
+	if ! use context; then
+		rm -r "${ED}"/usr/include/boost/context || die
+		rm -r "${ED}"/usr/include/boost/coroutine{,2} || die
+		rm "${ED}"/usr/include/boost/asio/spawn.hpp || die
+	fi
+
+	if use doc; then
+		# find extraneous files that shouldn't be installed
+		# as part of the documentation and remove them.
+		find libs/*/* \( -iname 'test' -o -iname 'src' \) -exec rm -rf '{}' + || die
+		find doc \( -name 'Jamfile.v2' -o -name 'build' -o -name '*.manifest' \) -exec rm -rf '{}' + || die
+		find tools \( -name 'Jamfile.v2' -o -name 'src' -o -name '*.cpp' -o -name '*.hpp' \) -exec rm -rf '{}' + || die
+
+		docinto html
+		dodoc *.{htm,html,png,css}
+		dodoc -r doc libs more tools
+
+		# To avoid broken links
+		dodoc LICENSE_1_0.txt
+
+		dosym ../../../../include/boost /usr/share/doc/${PF}/html/boost
+	fi
+
+	strip-lto-bytecode
+}
+
+pkg_preinst() {
+	# Yay for having symlinks that are nigh-impossible to remove without
+	# resorting to dirty hacks like these. Removes lingering symlinks
+	# from the slotted versions.
+	local symlink
+	for symlink in "${EROOT}"/usr/include/boost "${EROOT}"/usr/share/boostbook; do
+		if [[ -L ${symlink} ]]; then
+			rm -f "${symlink}" || die
+		fi
+	done
+
+	# some ancient installs still have boost cruft lying around
+	# for unknown reasons, causing havoc for reverse dependencies
+	# Bug: 607734
+	rm -rf "${EROOT}"/usr/include/boost-1_[3-5]? || die
+}
+
+pkg_postinst() {
+	elog "Boost.Regex is *extremely* ABI sensitive. If you get errors such as"
+	elog
+	elog "  undefined reference to \`boost::re_detail_$(ver_cut 1)0$(ver_cut 2)00::cpp_regex_traits_implementation"
+	elog "    <char>::transform_primary[abi:cxx11](char const*, char const*) const'"
+	elog
+	elog "Then you need to recompile Boost and all its reverse dependencies"
+	elog "using the same toolchain. In general, *every* change of the C++ toolchain"
+	elog "requires a complete rebuild of the Boost-dependent ecosystem."
+	elog
+	elog "See for instance https://bugs.gentoo.org/638138"
+}
diff --git a/dev-libs/boost/boost-1.91.0.ebuild b/dev-libs/boost/boost-1.91.0-r1.ebuild
similarity index 99%
rename from dev-libs/boost/boost-1.91.0.ebuild
rename to dev-libs/boost/boost-1.91.0-r1.ebuild
index b4f16ea383bdb..7e374ddaad9a3 100644
--- a/dev-libs/boost/boost-1.91.0.ebuild
+++ b/dev-libs/boost/boost-1.91.0-r1.ebuild
@@ -54,6 +54,7 @@ PATCHES=(
 	"${FILESDIR}"/${PN}-1.89.0-predef-include-path.patch
 	"${FILESDIR}"/${PN}-1.89.0-python-exclude-broken-tests.patch
 	"${FILESDIR}"/${PN}-1.89.0-unordered-no-tbb.patch
+	"${FILESDIR}"/${PN}-1.90.0-cobalt.patch
 	"${FILESDIR}"/${PN}-1.90.0-msm-std.patch
 	"${FILESDIR}"/${PN}-1.90.0-unsigned-char-EOF.patch
 	"${FILESDIR}"/${PN}-1.91.0-spirit-test.patch
diff --git a/dev-libs/boost/files/boost-1.90.0-cobalt.patch b/dev-libs/boost/files/boost-1.90.0-cobalt.patch
new file mode 100644
index 0000000000000..560bb9dca106d
--- /dev/null
+++ b/dev-libs/boost/files/boost-1.90.0-cobalt.patch
@@ -0,0 +1,34 @@
+Make sure cobalt gets actually built & installed correctly even when the
+toplevel build is using std=c++17. Similar to the fix for msm.
+https://bugs.gentoo.org/977237
+
+--- a/libs/cobalt/build/Jamfile
++++ a/libs/cobalt/build/Jamfile
+@@ -21,6 +21,7 @@ explicit
+ 
+ project : requirements
+   <define>BOOST_ASIO_NO_DEPRECATED
++  <toolset>gcc:<cxxflags>"-std=c++20 -fcoroutines"
+   <toolset>msvc:<define>_SCL_SECURE_NO_WARNINGS
+   <toolset>msvc:<define>_CRT_SECURE_NO_DEPRECATE
+   <toolset>msvc:<cxxflags>/bigobj
+@@ -57,9 +57,6 @@ lib boost_cobalt
+    : cobalt_sources
+    : requirements <define>BOOST_COBALT_SOURCE=1
+      <link>shared:<define>BOOST_COBALT_DYN_LINK=1
+-     [ requires
+-        cxx20_hdr_concepts
+-     ]
+      <boost.cobalt.pmr>boost-container:<library>/boost/container//boost_container
+       [ check-target-builds
+           $(config-binding:D)//cpp_lib_memory_resource
+--- a/libs/cobalt/test/Jamfile.jam
++++ a/libs/cobalt/test/Jamfile.jam
+@@ -10,6 +10,7 @@ import boost-cobalt ;
+ 
+ project : requirements
+   <define>BOOST_ASIO_NO_DEPRECATED
++  <toolset>gcc:<cxxflags>"-std=c++20 -fcoroutines"
+   <toolset>msvc:<define>_SCL_SECURE_NO_WARNINGS
+   <toolset>msvc:<define>_CRT_SECURE_NO_DEPRECATE
+   <toolset>msvc:<cxxflags>/bigobj