diff --git a/composer.lock b/composer.lock
index ca6011e482f64cb800a3762b11afcd56b237b70b..3f4c4c6c6e2730df4fb243b27cb9d17441a0327d 100644
--- a/composer.lock
+++ b/composer.lock
@@ -491,7 +491,7 @@
         },
         {
             "name": "drupal/core",
-            "version": "11.x-dev",
+            "version": "10.3.x-dev",
             "dist": {
                 "type": "path",
                 "url": "core",
@@ -652,7 +652,7 @@
         },
         {
             "name": "drupal/core-project-message",
-            "version": "11.x-dev",
+            "version": "10.3.x-dev",
             "dist": {
                 "type": "path",
                 "url": "composer/Plugin/ProjectMessage",
@@ -685,7 +685,7 @@
         },
         {
             "name": "drupal/core-vendor-hardening",
-            "version": "11.x-dev",
+            "version": "10.3.x-dev",
             "dist": {
                 "type": "path",
                 "url": "composer/Plugin/VendorHardening",
diff --git a/composer/Metapackage/CoreRecommended/composer.json b/composer/Metapackage/CoreRecommended/composer.json
index 1c185da55c5fd7d199b9deb66c7e6e45cd10dec2..d4fe6a131f01ad7d9001d9aec3293bf004301546 100644
--- a/composer/Metapackage/CoreRecommended/composer.json
+++ b/composer/Metapackage/CoreRecommended/composer.json
@@ -7,7 +7,7 @@
         "webflo/drupal-core-strict": "*"
     },
     "require": {
-        "drupal/core": "11.x-dev",
+        "drupal/core": "10.3.x-dev",
         "asm89/stack-cors": "~v2.2.0",
         "composer/semver": "~3.4.0",
         "doctrine/annotations": "~1.14.3",
diff --git a/composer/Metapackage/PinnedDevDependencies/composer.json b/composer/Metapackage/PinnedDevDependencies/composer.json
index b04ef07535c6c4f448bc45131eaaf16704c8b737..f5f2c3570c1660eaf050f0f1e4baf91028e41c07 100644
--- a/composer/Metapackage/PinnedDevDependencies/composer.json
+++ b/composer/Metapackage/PinnedDevDependencies/composer.json
@@ -7,7 +7,7 @@
         "webflo/drupal-core-require-dev": "*"
     },
     "require": {
-        "drupal/core": "11.x-dev",
+        "drupal/core": "10.3.x-dev",
         "behat/mink": "v1.11.0",
         "behat/mink-browserkit-driver": "v2.2.0",
         "behat/mink-selenium2-driver": "v1.7.0",
diff --git a/composer/Template/LegacyProject/composer.json b/composer/Template/LegacyProject/composer.json
index 204d1dcba1eb6ec152f3efdd116de2e9f579bdc8..da3bb1a0cb1540013457f5d98ef903dc4c433a85 100644
--- a/composer/Template/LegacyProject/composer.json
+++ b/composer/Template/LegacyProject/composer.json
@@ -16,13 +16,13 @@
     ],
     "require": {
         "composer/installers": "^2.0",
-        "drupal/core-composer-scaffold": "^11",
-        "drupal/core-project-message": "^11",
-        "drupal/core-recommended": "^11",
-        "drupal/core-vendor-hardening": "^11"
+        "drupal/core-composer-scaffold": "^10.3",
+        "drupal/core-project-message": "^10.3",
+        "drupal/core-recommended": "^10.3",
+        "drupal/core-vendor-hardening": "^10.3"
     },
     "require-dev": {
-        "drupal/core-dev": "^11"
+        "drupal/core-dev": "^10.3"
     },
     "conflict": {
         "drupal/drupal": "*"
diff --git a/composer/Template/RecommendedProject/composer.json b/composer/Template/RecommendedProject/composer.json
index 0b4926dabfda9080ceb2d992ffbaca187398ff0d..4814912141eb755b79d7e734a7785582320d1126 100644
--- a/composer/Template/RecommendedProject/composer.json
+++ b/composer/Template/RecommendedProject/composer.json
@@ -16,12 +16,12 @@
     ],
     "require": {
         "composer/installers": "^2.0",
-        "drupal/core-composer-scaffold": "^11",
-        "drupal/core-project-message": "^11",
-        "drupal/core-recommended": "^11"
+        "drupal/core-composer-scaffold": "^10.3",
+        "drupal/core-project-message": "^10.3",
+        "drupal/core-recommended": "^10.3"
     },
     "require-dev": {
-        "drupal/core-dev": "^11"
+        "drupal/core-dev": "^10.3"
     },
     "conflict": {
         "drupal/drupal": "*"
diff --git a/core/lib/Drupal.php b/core/lib/Drupal.php
index 99db2aec84534981e3c78ce8244a69f2d66a69ea..19f69d559a5f42e03549890cdba3a05822c89960 100644
--- a/core/lib/Drupal.php
+++ b/core/lib/Drupal.php
@@ -75,7 +75,7 @@ class Drupal {
   /**
    * The current system version.
    */
-  const VERSION = '11.0-dev';
+  const VERSION = '10.3.0-dev';
 
   /**
    * Core API compatibility.
diff --git a/core/lib/Drupal/Component/Annotation/composer.json b/core/lib/Drupal/Component/Annotation/composer.json
index 966b84e06ec9c3e26e5a9fcf1b36e9d9ada63837..218e7b2fa8ea9c9762cf8ac0386617e9216fceb2 100644
--- a/core/lib/Drupal/Component/Annotation/composer.json
+++ b/core/lib/Drupal/Component/Annotation/composer.json
@@ -9,10 +9,10 @@
     "require": {
         "php": ">=8.1.0",
         "doctrine/annotations": "^1.14",
-        "drupal/core-class-finder": "11.x-dev",
-        "drupal/core-file-cache": "11.x-dev",
-        "drupal/core-plugin": "11.x-dev",
-        "drupal/core-utility": "11.x-dev"
+        "drupal/core-class-finder": "10.3.x-dev",
+        "drupal/core-file-cache": "10.3.x-dev",
+        "drupal/core-plugin": "10.3.x-dev",
+        "drupal/core-utility": "10.3.x-dev"
     },
     "autoload": {
         "psr-4": {
diff --git a/core/lib/Drupal/Component/Datetime/composer.json b/core/lib/Drupal/Component/Datetime/composer.json
index 91bd608f5570c559da95bee80c2aa924234caaa8..c2391fb45a97bc00a5bc4ae6cb389eebf2013935 100644
--- a/core/lib/Drupal/Component/Datetime/composer.json
+++ b/core/lib/Drupal/Component/Datetime/composer.json
@@ -8,7 +8,7 @@
     "license": "GPL-2.0-or-later",
     "require": {
         "php": ">=8.1.0",
-        "drupal/core-utility": "11.x-dev"
+        "drupal/core-utility": "10.3.x-dev"
     },
     "autoload": {
         "psr-4": {
diff --git a/core/lib/Drupal/Component/Discovery/composer.json b/core/lib/Drupal/Component/Discovery/composer.json
index 4a9343967682b60fc6e33c276d411a1f80a6c365..758aef63450afb6a677f0501bda3dcb546d62da9 100644
--- a/core/lib/Drupal/Component/Discovery/composer.json
+++ b/core/lib/Drupal/Component/Discovery/composer.json
@@ -8,8 +8,8 @@
     "license": "GPL-2.0-or-later",
     "require": {
         "php": ">=8.1.0",
-        "drupal/core-file-cache": "11.x-dev",
-        "drupal/core-serialization": "11.x-dev"
+        "drupal/core-file-cache": "10.3.x-dev",
+        "drupal/core-serialization": "10.3.x-dev"
     },
     "autoload": {
         "psr-4": {
diff --git a/core/lib/Drupal/Component/FrontMatter/composer.json b/core/lib/Drupal/Component/FrontMatter/composer.json
index 9baa12c9d92d3c36b822103d0b4858281b873d51..5ff2dc304eb4d3615275ecbb3a815e3e5b5fc5a5 100644
--- a/core/lib/Drupal/Component/FrontMatter/composer.json
+++ b/core/lib/Drupal/Component/FrontMatter/composer.json
@@ -8,7 +8,7 @@
     "license": "GPL-2.0-or-later",
     "require": {
         "php": ">=8.1.0",
-        "drupal/core-serialization": "11.x-dev"
+        "drupal/core-serialization": "10.3.x-dev"
     },
     "autoload": {
         "psr-4": {
diff --git a/core/lib/Drupal/Component/Gettext/composer.json b/core/lib/Drupal/Component/Gettext/composer.json
index 0db3a4bc30b6db7ee1c4411bbd75614ab08f5f4d..61f297022976e690567909f0fa1a68b5651404e3 100644
--- a/core/lib/Drupal/Component/Gettext/composer.json
+++ b/core/lib/Drupal/Component/Gettext/composer.json
@@ -9,7 +9,7 @@
     },
     "require": {
         "php": ">=8.1.0",
-        "drupal/core-render": "11.x-dev"
+        "drupal/core-render": "10.3.x-dev"
     },
     "autoload": {
         "psr-4": {
diff --git a/core/lib/Drupal/Component/PhpStorage/composer.json b/core/lib/Drupal/Component/PhpStorage/composer.json
index 0517f06b0e35c65a610a043656a3c89ec3130299..be4099a3367f876b79d38a1fc09f773f0b7995d2 100644
--- a/core/lib/Drupal/Component/PhpStorage/composer.json
+++ b/core/lib/Drupal/Component/PhpStorage/composer.json
@@ -8,7 +8,7 @@
     "license": "GPL-2.0-or-later",
     "require": {
         "php": ">=8.1.0",
-        "drupal/core-file-security": "11.x-dev"
+        "drupal/core-file-security": "10.3.x-dev"
     },
     "autoload": {
         "psr-4": {
diff --git a/core/lib/Drupal/Component/Render/composer.json b/core/lib/Drupal/Component/Render/composer.json
index 338eb5135b2b8798493ed4c551ef5d4a8963d00e..5b2d7738f0c30848e81f0f29d5bbc68b43c513b9 100644
--- a/core/lib/Drupal/Component/Render/composer.json
+++ b/core/lib/Drupal/Component/Render/composer.json
@@ -8,7 +8,7 @@
     "license": "GPL-2.0-or-later",
     "require": {
         "php": ">=8.1.0",
-        "drupal/core-utility": "11.x-dev"
+        "drupal/core-utility": "10.3.x-dev"
     },
     "autoload": {
         "psr-4": {