diff --git a/.github/workflows/portage-stable-packages-list b/.github/workflows/portage-stable-packages-list
index 00d4f95d24..09b99ad147 100644
--- a/.github/workflows/portage-stable-packages-list
+++ b/.github/workflows/portage-stable-packages-list
@@ -293,6 +293,7 @@ dev-libs/tree-sitter
dev-libs/tree-sitter-bash
dev-libs/userspace-rcu
dev-libs/xmlsec
+dev-libs/xxhash
dev-libs/yajl
dev-perl/File-Slurper
@@ -671,6 +672,7 @@ sys-fs/btrfs-progs
sys-fs/cryptsetup
sys-fs/dosfstools
sys-fs/e2fsprogs
+sys-fs/erofs-utils
sys-fs/fuse
sys-fs/fuse-common
sys-fs/fuse-overlayfs
diff --git a/sdk_container/src/third_party/coreos-overlay/coreos-devel/sdk-depends/sdk-depends-0.0.1.ebuild b/sdk_container/src/third_party/coreos-overlay/coreos-devel/sdk-depends/sdk-depends-0.0.1.ebuild
index 0d8be10a14..f6812c1f75 100644
--- a/sdk_container/src/third_party/coreos-overlay/coreos-devel/sdk-depends/sdk-depends-0.0.1.ebuild
+++ b/sdk_container/src/third_party/coreos-overlay/coreos-devel/sdk-depends/sdk-depends-0.0.1.ebuild
@@ -46,6 +46,7 @@ DEPEND="
sys-firmware/edk2-bin
sys-fs/btrfs-progs
sys-fs/cryptsetup
+ sys-fs/erofs-utils
dev-perl/Parse-Yapp
dev-util/pkgcheck
"
diff --git a/sdk_container/src/third_party/coreos-overlay/profiles/coreos/targets/sdk/package.accept_keywords b/sdk_container/src/third_party/coreos-overlay/profiles/coreos/targets/sdk/package.accept_keywords
index 5a492c6d65..7eb67dc025 100644
--- a/sdk_container/src/third_party/coreos-overlay/profiles/coreos/targets/sdk/package.accept_keywords
+++ b/sdk_container/src/third_party/coreos-overlay/profiles/coreos/targets/sdk/package.accept_keywords
@@ -1 +1,5 @@
# Temporarily put the SDK version ahead for sd-json support in Dracut.
+
+# Needed for building signed sysexts with systemd-repart
+dev-libs/xxhash
+sys-fs/erofs-utils
diff --git a/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/Manifest b/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/Manifest
new file mode 100644
index 0000000000..1ea2e70343
--- /dev/null
+++ b/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/Manifest
@@ -0,0 +1,2 @@
+DIST xxhash-0.8.2.tar.gz 1141188 BLAKE2B 735408256240760778fa516e01bed428f04837eb4e059c512e924f13e4a96db6cacbbefb04dea65a37b0f25b52cf13c4927a6e7870dc8c0d45b1b955d4ba3da1 SHA512 3e3eef21432fe88bc4dd9940ccad0308fdea3537b06fa5ac0e74c1bde53413dff29c8b3fc617a8a42b9ce88fcf213311d338a31b1ce73b3729342c9e68f06c78
+DIST xxhash-0.8.3.tar.gz 1147630 BLAKE2B 75923c7c5df3490062791fa02ccddfb7281b3646e2b3e4b4a0c0d611c339e07c8d9cb656777fd0fcec9cda484f7b33edf080116bb011f70d6b8299cda63afa4e SHA512 8b5c8b9aad4e869f28310b12cc314037feda81d92f26c23eaecdb35dc65042ca2e65f2e9606033e62a31bcc737a9a950500ffcbdb8677d6ab20e820ea14f2b79
diff --git a/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/metadata.xml b/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/metadata.xml
new file mode 100644
index 0000000000..63e48a416a
--- /dev/null
+++ b/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/metadata.xml
@@ -0,0 +1,12 @@
+
+
+
+
+ amadio@gentoo.org
+ Guilherme Amadio
+
+
+ Cyan4973/xxHash
+ https://github.com/Cyan4973/xxHash/issues
+
+
diff --git a/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/xxhash-0.8.2.ebuild b/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/xxhash-0.8.2.ebuild
new file mode 100644
index 0000000000..1a4ff1b570
--- /dev/null
+++ b/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/xxhash-0.8.2.ebuild
@@ -0,0 +1,43 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit multilib-minimal toolchain-funcs
+
+DESCRIPTION="Extremely fast non-cryptographic hash algorithm"
+HOMEPAGE="https://xxhash.com/"
+SRC_URI="https://github.com/Cyan4973/xxHash/archive/v${PV}.tar.gz -> ${P}.tar.gz"
+S=${WORKDIR}/xxHash-${PV}
+
+LICENSE="BSD-2 GPL-2+"
+# https://abi-laboratory.pro/tracker/timeline/xxhash
+SLOT="0"
+KEYWORDS="~alpha amd64 arm arm64 ~hppa ~loong ~mips ppc ppc64 ~riscv ~s390 ~sparc x86 ~x64-macos"
+
+src_prepare() {
+ default
+
+ multilib_copy_sources
+}
+
+multilib_src_compile() {
+ emake AR="$(tc-getAR)" CC="$(tc-getCC)"
+}
+
+multilib_src_test() {
+ emake CC="$(tc-getCC)" check
+}
+
+multilib_src_install() {
+ local emakeargs=(
+ DESTDIR="${D}"
+ PREFIX="${EPREFIX}"/usr
+ LIBDIR="${EPREFIX}"/usr/$(get_libdir)
+ )
+
+ emake "${emakeargs[@]}" install
+ einstalldocs
+
+ rm "${ED}"/usr/$(get_libdir)/libxxhash.a || die
+}
diff --git a/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/xxhash-0.8.3.ebuild b/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/xxhash-0.8.3.ebuild
new file mode 100644
index 0000000000..ef8732bc66
--- /dev/null
+++ b/sdk_container/src/third_party/portage-stable/dev-libs/xxhash/xxhash-0.8.3.ebuild
@@ -0,0 +1,57 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit flag-o-matic multilib-minimal toolchain-funcs
+
+DESCRIPTION="Extremely fast non-cryptographic hash algorithm"
+HOMEPAGE="https://xxhash.com/"
+SRC_URI="https://github.com/Cyan4973/xxHash/archive/v${PV}.tar.gz -> ${P}.tar.gz"
+S=${WORKDIR}/xxHash-${PV}
+
+LICENSE="BSD-2 GPL-2+"
+SLOT="0"
+KEYWORDS="~alpha amd64 arm arm64 ~hppa ~loong ~mips ppc ppc64 ~riscv ~s390 ~sparc x86 ~x64-macos"
+
+src_prepare() {
+ default
+
+ multilib_copy_sources
+}
+
+src_configure() {
+ # Needed for -Og to be buildable, otherwise fails a/ always_inline (bug #961093)
+ # https://github.com/Cyan4973/xxHash?tab=readme-ov-file#binary-size-control
+ is-flagq '-Og' && append-cppflags -DXXH_NO_INLINE_HINTS
+ multilib-minimal_src_configure
+}
+
+myemake() {
+ emake \
+ AR="$(tc-getAR)" \
+ CC="$(tc-getCC)" \
+ "${@}"
+}
+
+multilib_src_compile() {
+ myemake
+}
+
+multilib_src_test() {
+ # Injecting CPPFLAGS into CFLAGS is needed for test_sanity
+ myemake CFLAGS="${CPPFLAGS} ${CFLAGS}" check
+}
+
+multilib_src_install() {
+ local emakeargs=(
+ DESTDIR="${D}"
+ PREFIX="${EPREFIX}"/usr
+ LIBDIR="${EPREFIX}"/usr/$(get_libdir)
+ )
+
+ myemake "${emakeargs[@]}" install
+ einstalldocs
+
+ rm "${ED}"/usr/$(get_libdir)/libxxhash.a || die
+}
diff --git a/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/Manifest b/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/Manifest
new file mode 100644
index 0000000000..07b48fc200
--- /dev/null
+++ b/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/Manifest
@@ -0,0 +1,2 @@
+DIST erofs-utils-1.8.10.tar.gz 201240 BLAKE2B 9575258115192dc0ef7999dd1fa44f619f9f62c93cfe28e3e65fd5d9a601b09acdce293552c90f51c2f7b557d8830e856d6706af6ccd98fc157b05f819d136b4 SHA512 8c7afd3db55fd4c4f7aa9fbd7ed40fa40de0bfffcee601a3f5dce823d406a32b5e939e24cd6dc336e3033e940fb16ee93f8821f627f90b10e6137113949933dd
+DIST erofs-utils-1.8.4.tar.gz 187276 BLAKE2B da0d80abbfd9b2d547c30bad7647165a3500f20e5de0b5db4c54efb27ec895fd069be983193b06d35728f5a8e1490e6cd255207c76135d8978d86e1512430755 SHA512 c941b0a2ab6c650a9aa4c9cadeb277ebc87007dc51354ff013c7cb763e6e8c9d44ed9e4791730ed05088faaba8c612198b924e70f5e52019382cfdf6d2e6b677
diff --git a/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/erofs-utils-1.8.10.ebuild b/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/erofs-utils-1.8.10.ebuild
new file mode 100644
index 0000000000..a55ac845ea
--- /dev/null
+++ b/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/erofs-utils-1.8.10.ebuild
@@ -0,0 +1,63 @@
+# Copyright 2021-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit autotools
+
+DESCRIPTION="Userspace tools for EROFS"
+HOMEPAGE="https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git"
+
+SRC_URI="https://git.kernel.org/pub/scm/linux/kernel/git/xiang/${PN}.git/snapshot/${P}.tar.gz"
+
+LICENSE="GPL-2+"
+SLOT="0"
+KEYWORDS="~amd64 ~arm64 ~loong"
+
+IUSE="fuse libdeflate +lz4 +lzma selinux static-libs +threads +uuid +zlib +zstd"
+
+RDEPEND="
+ dev-libs/xxhash:0=
+ fuse? ( sys-fs/fuse:0 )
+ lz4? ( app-arch/lz4:0= )
+ lzma? ( >=app-arch/xz-utils-5.4.0:0= )
+ selinux? ( sys-libs/libselinux:0= )
+ uuid? ( sys-apps/util-linux )
+ zlib? (
+ libdeflate? ( app-arch/libdeflate:0= )
+ !libdeflate? ( virtual/zlib:= )
+ )
+ zstd? ( app-arch/zstd:0= )
+"
+DEPEND="${RDEPEND}"
+BDEPEND="virtual/pkgconfig"
+
+PATCHES=(
+)
+
+src_prepare() {
+ default
+ eautoreconf
+}
+
+src_configure() {
+ local myeconfargs=(
+ --disable-werror
+ $(use_enable fuse)
+ $(use_with libdeflate)
+ $(use_enable lz4)
+ $(use_enable lzma)
+ $(use_with selinux)
+ $(use_enable static-libs static-fuse)
+ $(use_enable threads multithreading)
+ $(use_with uuid)
+ $(use_with zlib)
+ $(use_with zstd libzstd)
+ --without-qpl # not packaged
+ # do not use bundled xxhash; also upstream says "expected to be
+ # faster than the internal one"
+ --with-xxhash
+ )
+
+ econf "${myeconfargs[@]}"
+}
diff --git a/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/erofs-utils-1.8.4.ebuild b/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/erofs-utils-1.8.4.ebuild
new file mode 100644
index 0000000000..a55ac845ea
--- /dev/null
+++ b/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/erofs-utils-1.8.4.ebuild
@@ -0,0 +1,63 @@
+# Copyright 2021-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit autotools
+
+DESCRIPTION="Userspace tools for EROFS"
+HOMEPAGE="https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git"
+
+SRC_URI="https://git.kernel.org/pub/scm/linux/kernel/git/xiang/${PN}.git/snapshot/${P}.tar.gz"
+
+LICENSE="GPL-2+"
+SLOT="0"
+KEYWORDS="~amd64 ~arm64 ~loong"
+
+IUSE="fuse libdeflate +lz4 +lzma selinux static-libs +threads +uuid +zlib +zstd"
+
+RDEPEND="
+ dev-libs/xxhash:0=
+ fuse? ( sys-fs/fuse:0 )
+ lz4? ( app-arch/lz4:0= )
+ lzma? ( >=app-arch/xz-utils-5.4.0:0= )
+ selinux? ( sys-libs/libselinux:0= )
+ uuid? ( sys-apps/util-linux )
+ zlib? (
+ libdeflate? ( app-arch/libdeflate:0= )
+ !libdeflate? ( virtual/zlib:= )
+ )
+ zstd? ( app-arch/zstd:0= )
+"
+DEPEND="${RDEPEND}"
+BDEPEND="virtual/pkgconfig"
+
+PATCHES=(
+)
+
+src_prepare() {
+ default
+ eautoreconf
+}
+
+src_configure() {
+ local myeconfargs=(
+ --disable-werror
+ $(use_enable fuse)
+ $(use_with libdeflate)
+ $(use_enable lz4)
+ $(use_enable lzma)
+ $(use_with selinux)
+ $(use_enable static-libs static-fuse)
+ $(use_enable threads multithreading)
+ $(use_with uuid)
+ $(use_with zlib)
+ $(use_with zstd libzstd)
+ --without-qpl # not packaged
+ # do not use bundled xxhash; also upstream says "expected to be
+ # faster than the internal one"
+ --with-xxhash
+ )
+
+ econf "${myeconfargs[@]}"
+}
diff --git a/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/metadata.xml b/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/metadata.xml
new file mode 100644
index 0000000000..15abb558de
--- /dev/null
+++ b/sdk_container/src/third_party/portage-stable/sys-fs/erofs-utils/metadata.xml
@@ -0,0 +1,13 @@
+
+
+
+
+ xen0n@gentoo.org
+ WANG Xuerui
+
+
+