diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9c1c4d4..198fb61 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -33,6 +33,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v7
+        with:
+          submodules: recursive
 
       - name: Clean
         uses: ./.github/actions/maximize-build-space
diff --git a/.github/workflows/daily.yml b/.github/workflows/daily.yml
index 2f4ee77..358be27 100644
--- a/.github/workflows/daily.yml
+++ b/.github/workflows/daily.yml
@@ -34,6 +34,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v7
+        with:
+          submodules: recursive
 
       - name: Clean
         uses: ./.github/actions/maximize-build-space
diff --git a/.github/workflows/flatpak-x-checker.yml b/.github/workflows/flatpak-x-checker.yml
index a32782e..08b2b89 100644
--- a/.github/workflows/flatpak-x-checker.yml
+++ b/.github/workflows/flatpak-x-checker.yml
@@ -10,6 +10,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v7
+        with:
+          submodules: recursive
       - uses: docker://ghcr.io/flathub/flatpak-external-data-checker:latest
         env:
           GIT_AUTHOR_NAME: elementaryBot
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index ed270ad..b6f42b6 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -37,6 +37,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v7
+        with:
+          submodules: recursive
 
       - name: Clean
         uses: ./.github/actions/maximize-build-space
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..1e7a990
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "shared-modules"]
+	path = shared-modules
+	url = https://github.com/flathub/shared-modules.git
diff --git a/io.elementary.Sdk.json.in b/io.elementary.Sdk.json.in
index e8e63e1..c5031ad 100644
--- a/io.elementary.Sdk.json.in
+++ b/io.elementary.Sdk.json.in
@@ -3,16 +3,17 @@
     "id": "io.elementary.Sdk",
     "id-platform": "io.elementary.Platform",
     "default-branch": "@branch@",
-    "runtime-version": "51",
-    "runtime": "org.gnome.Platform",
-    "sdk": "org.gnome.Sdk",
+    "runtime-version": "26.08",
+    "runtime": "org.freedesktop.Platform",
+    "sdk": "org.freedesktop.Sdk",
     "sdk-extensions": [
-        "org.gnome.Sdk.Debug",
-        "org.gnome.Sdk.Locale",
-        "org.gnome.Sdk.Docs"
+        "org.freedesktop.Sdk.Debug",
+        "org.freedesktop.Sdk.Locale",
+        "org.freedesktop.Sdk.Docs",
+        "org.freedesktop.Sdk.Extension.vala"
     ],
     "platform-extensions": [
-        "org.gnome.Platform.Locale"
+        "org.freedesktop.Platform.Locale"
     ],
     "inherit-extensions": [
         "org.freedesktop.Platform.GL",
@@ -47,9 +48,127 @@
     "build-options": {
         "env": {
             "PYTHON": "python3"
-        }
+        },
+        "prepend-path": "/usr/lib/sdk/vala/bin",
+        "prepend-ld-library-path": "/usr/lib/sdk/vala/lib"
     },
     "modules": [
+        {
+            "name": "libgee",
+            "buildsystem": "autotools",
+            "sources": [
+                {
+                    "type": "archive",
+                    "url": "https://download.gnome.org/sources/libgee/0.20/libgee-0.20.8.tar.xz",
+                    "sha256": "189815ac143d89867193b0c52b7dc31f3aa108a15f04d6b5dca2b6adfad0b0ee",
+                    "x-checker-data": {
+                        "type": "gnome",
+                        "name": "libgee"
+                    }
+                }
+            ]
+        },
+        {
+            "name": "gtk4",
+            "cleanup": [
+                "/bin",
+                "/share/bash-completion",
+                "/share/gettext",
+                "/share/glib-2.0",
+                "/share/gtk-4.0"
+            ],
+            "buildsystem": "meson",
+            "config-opts": [
+                "-Dintrospection=enabled",
+                "-Dbuild-demos=false",
+                "-Dbuild-testsuite=false",
+                "-Dbuild-examples=false",
+                "-Dbuild-tests=false"
+            ],
+            "sources": [
+                {
+                    "type": "archive",
+                    "url": "https://download.gnome.org/sources/gtk/4.22/gtk-4.22.5.tar.xz",
+                    "sha256": "7fd725deb2cb3f8dc218ad862c5056ff8548f49d3b0e4081796e444c22d19686",
+                    "x-checker-data": {
+                        "type": "gnome",
+                        "name": "gtk",
+                        "stable-only": true,
+                        "version-scheme": "odd-minor-is-unstable",
+                        "versions": {
+                            "<": "2.24.0"
+                        }
+                    }
+                }
+            ]
+        },
+        {
+            "name": "sassc",
+            "cleanup": [
+                "*"
+            ],
+            "sources": [
+                {
+                    "type": "git",
+                    "url": "https://github.com/sass/sassc.git",
+                    "tag": "3.6.2"
+                },
+                {
+                    "type": "script",
+                    "dest-filename": "autogen.sh",
+                    "commands": [
+                        "autoreconf -si"
+                    ]
+                }
+            ],
+            "modules": [
+                {
+                    "name": "libsass",
+                    "cleanup": [
+                        "*"
+                    ],
+                    "sources": [
+                        {
+                            "type": "git",
+                            "url": "https://github.com/sass/libsass.git",
+                            "tag": "3.6.5"
+                        },
+                        {
+                            "type": "script",
+                            "dest-filename": "autogen.sh",
+                            "commands": [
+                                "autoreconf -si"
+                            ]
+                        }
+                    ]
+                }
+            ]
+        },
+        {
+            "name": "libadwaita",
+            "buildsystem": "meson",
+            "config-opts": [
+                "-Dtests=false",
+                "-Dexamples=false"
+            ],
+            "sources": [
+                {
+                    "type": "archive",
+                    "url": "https://download.gnome.org/sources/libadwaita/1.9/libadwaita-1.9.4.tar.xz",
+                    "sha256": "f5ab3453ee743dc293cdf96d6821789cd20e8d125d9b41637703c12bfa4162ee",
+                    "x-checker-data": {
+                        "type": "gnome",
+                        "name": "libadwaita",
+                        "versions": {
+                            "<": "1.10.0"
+                        }
+                    }
+                }
+            ],
+            "modules": [
+                "../shared-modules/appstream/appstream-compose.json"
+            ]
+        },
         {
             "name": "icons",
             "buildsystem": "meson",
@@ -100,50 +219,6 @@
                         "tag-pattern": "^([\\d.]+)$"
                     }
                 }
-            ],
-            "modules": [
-                {
-                    "name": "sassc",
-                    "cleanup": [
-                        "*"
-                    ],
-                    "sources": [
-                        {
-                            "type": "git",
-                            "url": "https://github.com/sass/sassc.git",
-                            "tag": "3.6.2"
-                        },
-                        {
-                            "type": "script",
-                            "dest-filename": "autogen.sh",
-                            "commands": [
-                                "autoreconf -si"
-                            ]
-                        }
-                    ],
-                    "modules": [
-                        {
-                            "name": "libsass",
-                            "cleanup": [
-                                "*"
-                            ],
-                            "sources": [
-                                {
-                                    "type": "git",
-                                    "url": "https://github.com/sass/libsass.git",
-                                    "tag": "3.6.5"
-                                },
-                                {
-                                    "type": "script",
-                                    "dest-filename": "autogen.sh",
-                                    "commands": [
-                                        "autoreconf -si"
-                                    ]
-                                }
-                            ]
-                        }
-                    ]
-                }
             ]
         },
         {
diff --git a/shared-modules b/shared-modules
new file mode 160000
index 0000000..cb9ec60
--- /dev/null
+++ b/shared-modules
@@ -0,0 +1 @@
+Subproject commit cb9ec602a1ece1c76d5a4f8aa1d87c4a6bf99c3e