diff --git a/dev-build/meson/Manifest b/dev-build/meson/Manifest
index bf4251bb53ccb..0afe03e43aa0c 100644
--- a/dev-build/meson/Manifest
+++ b/dev-build/meson/Manifest
@@ -6,10 +6,13 @@ DIST meson-1.11.2.tar.gz 2463316 BLAKE2B c4ad77fe543b555d23f511dd2de43f6ee259384
 DIST meson-1.11.2.tar.gz.asc 833 BLAKE2B 937dd1858679140471deaa8ffd6aaa76873f1f67bfffac406b3ca516635b1dadb8e554e45bb34611f52c0d5b61426aca9d23d399bf844f5ca590a75090af5b8f SHA512 370cf3d26c36e1a3c775309450f3191532953626f58e04cc059cfd719f1444778025b61591b33e7749c13e0cc841461f2063369abe27b78c6b77522322df5e76
 DIST meson-1.12.0rc1.tar.gz 2516312 BLAKE2B 75f6f2648f6f9aa382bb605abd2c4cd5b53a99a6209b7036b6c613333f0eae8a698ee58cba80b362340055aadf1f05b4a0f29ca2527cd0bbabc994527d21a008 SHA512 382681d54bb6e5713bb36b335c420b8aeaffe3aaac25c5554355a841ba36c01f2af18f4af52de8e802115fcfd395a81dc216e017a79a206700b509a2dca9eb2a
 DIST meson-1.12.0rc1.tar.gz.asc 833 BLAKE2B 7ed2b8c568281450654ae3eeda44bd87ee5bbbc8e7d77d211df6899b25c23189fabc6eea816e81089240708724a906f995cee70d08cc2ab830ea17627b5ffb57 SHA512 0551dcdb1a47be403ba322e82de369e879505d7a3963eacb9102926b94a272da787581e173cc6c12be10c870f38afdcd14c4dc6c955e60acfbd3d7ea16a60ace
+DIST meson-1.12.0rc2.tar.gz 2519078 BLAKE2B 640356e2d1fbe0834d71c885ff2ab8d13a3ba6994ac4bebe1f52260196fa2c6b2574afc150238efbe05fbb240a5fcc69bc52de54964522da6f365e7ee1d04803 SHA512 5a7bd6379933fb2b63c596c6c40a8963052dbfe76003c2d73037c85379ccfbe04f283f3823f6b28f5bfdde72e6e21b040a29a5bce9989eacc7659c236e7f92ac
+DIST meson-1.12.0rc2.tar.gz.asc 833 BLAKE2B 605e2f57332023028a3554d0a9d2937dcb94c7f3933d72b7ad364cbe04e56b094542c939085a6d12ac53d76ef599292a10a2e28a09a866ea1f453f4799726685 SHA512 ad04b9878d26c0843d1518ee53b7d10a99f882b805980e5cfce863ff460441658471d3ff2b071741a5463d51163eead3cdb6c6e46813af3d5f336c3c2e604516
 DIST meson-1.9.2.tar.gz 2382854 BLAKE2B f099352abbc0fa8d358cbe406955ddf817453cdc244b36f322e11b5b3020013641d162c68c9bce119cf866e8082a14a3f7db9930b66dfba15805afb32440f555 SHA512 3237e55bb8374f65f40dccd8a93493a42fc425337758b8600b377c5e9795a1bdc97942fc19fedd4c3cb697f87c1d54364a637110704a5dc1a391d712be1463bc
 DIST meson-1.9.2.tar.gz.asc 833 BLAKE2B f161b2918c341172de5f141ac367d7d62a60f2d0eadd793f71fb6a19e8944b4ad6bbfbb25d233862066eec8e422295d46e03ce8aca26e1081f2bcb456b7c1057 SHA512 c8cace334e31d5ba3e4f2da687ed945182e3039dc8bbea94015caa82d373c4b4d96a425eccb7617793fd471040705711b00ab37705dcd2070be6ba089586652b
 DIST meson-reference-1.10.2.3 366569 BLAKE2B 28b37c33cb94f3cad8de68eeaaf210a470d14df68fa00d8fe18b79ab9acee71a725fa9cbcf57c9c470f98acd540123612dfd9974fb67121ce72fdc70168cfab8 SHA512 1defa912aeac9a5768e7f3ad669d4471a457c6fc70ead30c428ecc335d3a06db56314a5ad343aff7805b1a46388cbfba5b4188e2ef55d10b35767c046dcb0f36
 DIST meson-reference-1.11.1.3 383896 BLAKE2B 6262239b32c9be67eb426f2c208f7395ddb7894869d2d96618aec035a60e1529273c0e22f8fe141393465a96a962f3f307cad2353569dd0d7006e79cd9e36f41 SHA512 52a6efd4b52b389986c7ce346b5ccb2abc9e2afc66dcc83ee3b2d981a81c7052520afbbc34c483e6db53660048fb14925ca6fb5718c76768c6773458b8adf814
 DIST meson-reference-1.11.2.3 383896 BLAKE2B f202f256f49a7c9a47f142bed4327097ea2af0d321356efdd01f0612ad38acb372e7a1d2623ca8d490d6eeded7256edc9ac91080d05d966899b94da96b174cb9 SHA512 3f55e8a79eddf20c6562c9ebe9d820db1ead649d0f3c6c47a7a888b3ec05f05202e6087e39d3810f786ce4cd375a5e0b7397c9851040a3f4c46f01ad472d1898
 DIST meson-reference-1.12.0rc1.3 385710 BLAKE2B c963b93419cc048d85daaf2c8280fa60891bc7b888bac1621af807d7faa4a60ca7822f48fec3431181f118122fb8c1bf5a041465cd3d0e6bf4cb30cc1fe019c3 SHA512 76bb6d4b77e88137bd3bb09b122807d378821c02b17ae115bfb60b462d59a5b50e469032e596eb10de21cf3a64304ce99c4bafe7fd6bedc3fa24bdbec2c8f679
+DIST meson-reference-1.12.0rc2.3 385710 BLAKE2B 04839b450dac0d95f01ce0ca6289a92f1c1ae6d51308872e70205e27915f637ca2ec2ddd4e8e12fcff38f54abb25bb1fee0108737f2772c104bda902bcdf98d0 SHA512 8bcc883e08977d0ac42c052c6fab5aacc38b4c6a1983ea550a826350d51d153213872478e244032d54b57a32832d9b59aa9b40b19948093090fe3b8c0b7a5984
 DIST meson-reference-1.9.2.3 347286 BLAKE2B ece5e2075e1d1aabe9daf09e8dbdd4c22d0940b957cc61443c9ea0136e54c9f39244cc082f7a784209bb1bb81b116acae74f02501a9cd16df6d06ff9dcda08c0 SHA512 dbf57730e6c6ac6d3ebfba70f4c4b479d8e1a502854343c776f5ba0e9c7a4ba10bf75758b3434dd418041019ab7d704fe1424f49adaf41e260f652b58fd9cb23
diff --git a/dev-build/meson/meson-1.12.0_rc2.ebuild b/dev-build/meson/meson-1.12.0_rc2.ebuild
new file mode 100644
index 0000000000000..e8ba3870cc367
--- /dev/null
+++ b/dev-build/meson/meson-1.12.0_rc2.ebuild
@@ -0,0 +1,242 @@
+# Copyright 2016-2026 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+PYTHON_COMPAT=( python3_{12..15} )
+DISTUTILS_USE_PEP517=setuptools
+
+inherit shell-completion edo distutils-r1 flag-o-matic toolchain-funcs vala
+
+if [[ ${PV} = *9999* ]]; then
+	EGIT_REPO_URI="https://github.com/mesonbuild/meson"
+	inherit ninja-utils git-r3
+
+	BDEPEND="
+		${NINJA_DEPEND}
+		$(python_gen_any_dep 'dev-python/pyyaml[${PYTHON_USEDEP}]')
+	"
+
+else
+	inherit verify-sig
+
+	MY_PV=${PV/_/}
+	MY_P=${P/_/}
+	S=${WORKDIR}/${MY_P}
+
+	SRC_URI="
+		https://github.com/mesonbuild/meson/releases/download/${MY_PV}/${MY_P}.tar.gz
+		verify-sig? ( https://github.com/mesonbuild/meson/releases/download/${MY_PV}/${MY_P}.tar.gz.asc )
+		https://github.com/mesonbuild/meson/releases/download/${MY_PV}/meson-reference.3 -> meson-reference-${MY_PV}.3
+	"
+	# Releases may be signed by those listed in Releasing.md. Jussi
+	# remains the default release manager.
+	# https://github.com/mesonbuild/meson/commit/c2d795735fa1c46c54d6aed4d4a30f36a1f853cb
+	BDEPEND="verify-sig? ( >=sec-keys/openpgp-keys-eschwartz-20250723-r1 sec-keys/openpgp-keys-jpakkane )"
+	#VERIFY_SIG_OPENPGP_KEY_PATH=/usr/share/openpgp-keys/eschwartz.asc
+	VERIFY_SIG_OPENPGP_KEY_PATH=/usr/share/openpgp-keys/jpakkane.gpg
+
+	if [[ ${PV} != *_rc* ]] ; then
+		KEYWORDS="~alpha ~amd64 ~arm ~arm64 ~hppa ~loong ~m68k ~mips ~ppc ~ppc64 ~riscv ~s390 ~sparc ~x86 ~arm64-macos ~x64-macos ~x64-solaris"
+	fi
+fi
+
+DESCRIPTION="Open source build system"
+HOMEPAGE="https://mesonbuild.com/"
+
+LICENSE="Apache-2.0"
+SLOT="0"
+IUSE="test test-full"
+RESTRICT="!test? ( test )"
+REQUIRED_USE="test-full? ( test )"
+
+# test-full contains various test dependencies, for optional test cases of
+# frameworks Meson has support for. These will *usually* get skipped
+# automatically if uninstalled. The dep allows:
+# - guaranteeing the whole test suite runs transparently without skips
+# - reducing brittleness of frameworks that straddle multiple packages
+#   - Qt is a particular example of this. qt5 is deprecated, but we need qtbase
+#     consistently installed as long as it isn't masked for removal. TODO: drop
+#     dev-qt/*:5 from DEPEND once they are masked.
+
+DEPEND="
+	test? (
+		dev-libs/glib:2
+		>=dev-libs/gobject-introspection-1.82.0-r2
+		app-alternatives/ninja
+		dev-vcs/git
+		virtual/zlib:=[static-libs(+)]
+		virtual/pkgconfig
+		dev-build/cmake
+	)
+	test-full? (
+		|| ( dev-lang/rust dev-lang/rust-bin )
+		dev-lang/nasm
+		>=dev-lang/pypy-3
+		$(vala_depend)
+		dev-python/cython
+		virtual/fortran
+		virtual/jdk
+
+		app-text/doxygen
+		dev-cpp/gtest
+		dev-libs/protobuf
+		dev-util/bindgen
+		dev-util/gtk-doc
+		dev-util/itstool
+		llvm-core/llvm
+		media-libs/libsdl2
+		media-libs/libwmf
+		net-libs/libpcap
+		sci-libs/hdf5[cxx,fortran]
+		sci-libs/netcdf
+		sys-cluster/openmpi[fortran]
+		sys-devel/bison
+		sys-devel/flex
+
+		dev-qt/qtbase:6[gui,widgets]
+		dev-qt/qtdeclarative:6
+		dev-qt/qttools:6
+		>=dev-util/gdbus-codegen-2.80.5-r1
+		x11-libs/gtk+:3
+
+		dev-libs/wayland
+		dev-util/wayland-scanner
+	)
+"
+RDEPEND="
+	!<dev-build/muon-0.2.0-r2[man(-)]
+	virtual/pkgconfig
+"
+
+PATCHES=(
+	"${FILESDIR}"/${PN}-1.10.0-python-path.patch
+)
+
+src_unpack() {
+	if [[ ${PV} = *9999* ]]; then
+		git-r3_src_unpack
+	else
+		default
+		use verify-sig && verify-sig_verify_detached "${DISTDIR}"/${MY_P}.tar.gz{,.asc}
+	fi
+}
+
+python_prepare_all() {
+	local disable_unittests=(
+		# ASAN and sandbox both want control over LD_PRELOAD
+		# https://bugs.gentoo.org/673016
+		-e 's/test_generate_gir_with_address_sanitizer/_&/'
+		-e 's/test_env_cflags_ldflags/_&/'
+		-e 's/test_c_link_args_and_env/_&/'
+
+		# ASAN is unsupported on some targets
+		# https://bugs.gentoo.org/692822
+		-e 's/test_pch_with_address_sanitizer/_&/'
+
+		# clippy-driver fails, but only when run via portage.
+		#
+		#   error[E0463]: can't find crate for `std`
+		#   error: requires `sized` lang_item
+		-e 's/test_rust_clippy/_&/'
+	)
+
+	sed -i "${disable_unittests[@]}" unittests/*.py || die
+
+	# Broken due to python2 script created by python_wrapper_setup
+	rm -r "test cases/frameworks/1 boost" || die
+	# nvcc breaks on essentially any LDFLAGS
+	# https://bugs.gentoo.org/936757
+	# https://github.com/mesonbuild/meson/issues/11234
+	rm -r "test cases/cuda"/* || die
+
+	distutils-r1_python_prepare_all
+}
+
+python_check_deps() {
+	if [[ ${PV} = *9999* ]]; then
+		python_has_version "dev-python/pyyaml[${PYTHON_USEDEP}]"
+	fi
+}
+
+python_configure_all() {
+	if [[ ${PV} = *9999* ]]; then
+		# We use the unsafe_yaml loader because strictyaml is not packaged. In
+		# theory they produce the same results, but pyyaml is faster and
+		# without safety checks.
+		edo ./meson.py setup \
+			--prefix "${EPREFIX}/usr" \
+			-Dhtml=false \
+			-Dunsafe_yaml=true \
+			docs/ docs/builddir
+	fi
+}
+
+python_compile_all() {
+	if [[ ${PV} = *9999* ]]; then
+		eninja -C docs/builddir
+	fi
+}
+
+src_test() {
+	tc-export PKG_CONFIG
+	if ${PKG_CONFIG} --exists Qt5Core && ! ${PKG_CONFIG} --exists Qt5Gui; then
+		ewarn "Found Qt5Core but not Qt5Gui; skipping tests"
+	else
+		distutils-r1_src_test
+	fi
+}
+
+python_test() {
+	(
+		# meson has its own tests for LTO support. We don't need to verify that
+		# all tests work when they happen to use it. And in particular, this
+		# breaks rust.
+		filter-lto
+
+		# bug 513658
+		has_version -b dev-lang/vala && vala_setup
+
+		# remove unwanted python_wrapper_setup contents
+		# We actually do want to non-error if python2 is installed and tested.
+		remove="${T}/${EPYTHON}/bin:"
+		PATH=${PATH/${remove}/}
+
+		# test_meson_installed
+		unset PYTHONDONTWRITEBYTECODE
+
+		# https://bugs.gentoo.org/687792
+		unset PKG_CONFIG
+
+		# test_cross_file_system_paths
+		unset XDG_DATA_HOME
+
+		# 'test cases/unit/73 summary' expects 80 columns
+		export COLUMNS=80
+
+		# If JAVA_HOME is not set, meson looks for javac in PATH.
+		# If javac is in /usr/bin, meson assumes /usr/include is a valid
+		# JDK include path. Setting JAVA_HOME works around this broken
+		# autodetection. If no JDK is installed, we should end up with an empty
+		# value in JAVA_HOME, and the tests should get skipped.
+		export JAVA_HOME=$(java-config -O 2>/dev/null)
+
+		${EPYTHON} -u run_tests.py
+	) || die "Testing failed with ${EPYTHON}"
+}
+
+python_install_all() {
+	distutils-r1_python_install_all
+
+	insinto /usr/share/vim/vimfiles
+	doins -r data/syntax-highlighting/vim/{ftdetect,indent,syntax}
+
+	dozshcomp data/shell-completions/zsh/_meson
+	dobashcomp data/shell-completions/bash/meson
+
+	if [[ ${PV} = *9999* ]]; then
+		DESTDIR="${ED}" eninja -C docs/builddir install
+	else
+		newman "${DISTDIR}"/meson-reference-${MY_PV}.3 meson-reference.3
+	fi
+}