diff --git a/.github/workflows/build-and-deploy-snapshot.yml b/.github/workflows/build-and-deploy-snapshot.yml
index 9288e202538..b7e70af19ff 100644
--- a/.github/workflows/build-and-deploy-snapshot.yml
+++ b/.github/workflows/build-and-deploy-snapshot.yml
@@ -3,7 +3,7 @@ on:
   workflow_dispatch:
   push:
     branches:
-      - main
+      - 4.0.x
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
 jobs:
@@ -28,7 +28,7 @@ jobs:
       - name: Deploy
         uses: spring-io/artifactory-deploy-action@dc1913008c0599f0c4b1fdafb6ff3c502b3565ea # v0.0.2
         with:
-          build-name: ${{ vars.COMMERCIAL && format('spring-boot-commercial-{0}', '3.5.x') || format('spring-boot-{0}', '3.5.x') }}
+          build-name: ${{ vars.COMMERCIAL && format('spring-boot-commercial-{0}', '4.0.x') || format('spring-boot-{0}', '4.0.x') }}
           folder: 'deployment-repository'
           password: ${{ vars.COMMERCIAL && secrets.COMMERCIAL_ARTIFACTORY_PASSWORD || secrets.ARTIFACTORY_PASSWORD }}
           project: ${{ vars.COMMERCIAL && 'spring' }}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1f32c5dab41..c40454d0917 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,7 +2,7 @@ name: CI
 on:
   push:
     branches:
-      - main
+      - 4.0.x
 jobs:
   ci:
     name: '${{ matrix.os.name}} | Java ${{ matrix.java.version}}'
diff --git a/.github/workflows/run-system-tests.yml b/.github/workflows/run-system-tests.yml
index 26d8c2ddafd..77db6ed25d3 100644
--- a/.github/workflows/run-system-tests.yml
+++ b/.github/workflows/run-system-tests.yml
@@ -2,7 +2,7 @@ name: Run System Tests
 on:
   push:
     branches:
-      - main
+      - 4.0.x
 jobs:
   run-system-tests:
     name: 'Java ${{ matrix.java.version}}'
diff --git a/gradle.properties b/gradle.properties
index 850e53994a2..bc0e93714be 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,4 +1,4 @@
-version=3.5.0-SNAPSHOT
+version=4.0.0-SNAPSHOT
 latestVersion=true
 spring.build-type=oss
 
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered-custom/jar/src/layers.xml b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered-custom/jar/src/layers.xml
index ee870e78305..a7a3dc82f48 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered-custom/jar/src/layers.xml
+++ b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered-custom/jar/src/layers.xml
@@ -1,7 +1,7 @@
 <layers xmlns="http://www.springframework.org/schema/boot/layers"
 	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 	xsi:schemaLocation="http://www.springframework.org/schema/boot/layers
-					  https://www.springframework.org/schema/layers/layers-3.5.xsd">
+					  https://www.springframework.org/schema/layers/layers-4.0.xsd">
 	<application>
 		<into layer="configuration">
 			<include>**/application*.*</include>
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/war-layered-custom/war/src/layers.xml b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/war-layered-custom/war/src/layers.xml
index ee870e78305..a7a3dc82f48 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/war-layered-custom/war/src/layers.xml
+++ b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/war-layered-custom/war/src/layers.xml
@@ -1,7 +1,7 @@
 <layers xmlns="http://www.springframework.org/schema/boot/layers"
 	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 	xsi:schemaLocation="http://www.springframework.org/schema/boot/layers
-					  https://www.springframework.org/schema/layers/layers-3.5.xsd">
+					  https://www.springframework.org/schema/layers/layers-4.0.xsd">
 	<application>
 		<into layer="configuration">
 			<include>**/application*.*</include>
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/xsd/layers-4.0.xsd b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/xsd/layers-4.0.xsd
new file mode 100644
index 00000000000..20219b9bd8b
--- /dev/null
+++ b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/xsd/layers-4.0.xsd
@@ -0,0 +1,100 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<xsd:schema elementFormDefault="qualified"
+	xmlns="http://www.springframework.org/schema/boot/layers"
+	xmlns:xsd="http://www.w3.org/2001/XMLSchema"
+	targetNamespace="http://www.springframework.org/schema/boot/layers">
+	<xsd:element name="layers" type="layersType" />
+	<xsd:complexType name="layersType">
+		<xsd:sequence>
+			<xsd:element name="application" type="applicationType" minOccurs="0"/>
+			<xsd:element name="dependencies" type="dependenciesType" minOccurs="0"/>
+			<xsd:element name="layerOrder" type="layerOrderType" minOccurs="0"/>
+		</xsd:sequence>
+	</xsd:complexType>
+	<xsd:complexType name="applicationType">
+		<xsd:annotation>
+			<xsd:documentation><![CDATA[
+	The 'into layer' selections that should be applied to application classes and resources.
+				]]></xsd:documentation>
+		</xsd:annotation>
+		<xsd:sequence maxOccurs="unbounded">
+			<xsd:element name="into" type="intoType" />
+		</xsd:sequence>
+	</xsd:complexType>
+	<xsd:complexType name="dependenciesType">
+		<xsd:annotation>
+			<xsd:documentation><![CDATA[
+	The 'into layer' selections that should be applied to dependencies.
+				]]></xsd:documentation>
+		</xsd:annotation>
+		<xsd:sequence maxOccurs="unbounded">
+			<xsd:element name="into" type="dependenciesIntoType" />
+		</xsd:sequence>
+	</xsd:complexType>
+	<xsd:complexType name="layerOrderType">
+		<xsd:annotation>
+			<xsd:documentation><![CDATA[
+	The order that layers should be added (starting with the least frequently changed layer).
+				]]></xsd:documentation>
+		</xsd:annotation>
+		<xsd:sequence>
+			<xsd:element name="layer" maxOccurs="unbounded">
+				<xsd:annotation>
+					<xsd:documentation><![CDATA[
+	The layer name.
+				]]></xsd:documentation>
+				</xsd:annotation>
+				<xsd:simpleType>
+					<xsd:restriction base="xsd:string">
+						<xsd:minLength value="1" />
+					</xsd:restriction>
+				</xsd:simpleType>
+			</xsd:element>
+		</xsd:sequence>
+	</xsd:complexType>
+	<xsd:complexType name="intoType">
+		<xsd:choice maxOccurs="unbounded">
+			<xsd:element type="xsd:string" name="include"
+				minOccurs="0" maxOccurs="unbounded">
+				<xsd:annotation>
+					<xsd:documentation><![CDATA[
+	Pattern of the elements to include.
+			]]></xsd:documentation>
+				</xsd:annotation>
+			</xsd:element>
+			<xsd:element type="xsd:string" name="exclude"
+				minOccurs="0" maxOccurs="unbounded">
+				<xsd:annotation>
+					<xsd:documentation><![CDATA[
+	Pattern of the elements to exclude.
+			]]></xsd:documentation>
+				</xsd:annotation>
+			</xsd:element>
+		</xsd:choice>
+		<xsd:attribute type="xsd:string" name="layer"
+			use="required" />
+	</xsd:complexType>
+	<xsd:complexType name="dependenciesIntoType">
+		<xsd:complexContent>
+			<xsd:extension base="intoType">
+				<xsd:choice minOccurs="0">
+					<xsd:element type="xsd:string" name="includeModuleDependencies" minOccurs="0">
+						<xsd:annotation>
+							<xsd:documentation><![CDATA[
+	Include dependencies on other modules in the build.
+							]]></xsd:documentation>
+						</xsd:annotation>
+					</xsd:element>
+					<xsd:element type="xsd:string" name="excludeModuleDependencies" minOccurs="0">
+						<xsd:annotation>
+							<xsd:documentation><![CDATA[
+	Exclude dependencies on other modules in the build.
+							]]></xsd:documentation>
+						</xsd:annotation>
+					</xsd:element>
+				</xsd:choice>
+			</xsd:extension>
+		</xsd:complexContent>
+	</xsd:complexType>
+
+</xsd:schema>
\ No newline at end of file
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/dependencies-layer-no-filter.xml b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/dependencies-layer-no-filter.xml
index 4a65ffd54c6..32808c3122f 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/dependencies-layer-no-filter.xml
+++ b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/dependencies-layer-no-filter.xml
@@ -1,7 +1,7 @@
 <layers xmlns="http://www.springframework.org/schema/boot/layers"
 	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 	xsi:schemaLocation="http://www.springframework.org/schema/boot/layers
-					  https://www.springframework.org/schema/boot/layers/layers-3.5.xsd">
+					  https://www.springframework.org/schema/boot/layers/layers-4.0.xsd">
 	<dependencies>
 		<into layer="my-deps" />
 	</dependencies>
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/layers.xml b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/layers.xml
index 731fd8ddfd4..b91c1f65d8e 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/layers.xml
+++ b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/layers.xml
@@ -1,7 +1,7 @@
 <layers xmlns="http://www.springframework.org/schema/boot/layers"
 	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 	xsi:schemaLocation="http://www.springframework.org/schema/boot/layers
-					  https://www.springframework.org/schema/boot/layers/layers-3.5.xsd">
+					  https://www.springframework.org/schema/boot/layers/layers-4.0.xsd">
 	<application>
 		<into layer="my-resources">
 			<include>META-INF/resources/**</include>
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/resource-layer-no-filter.xml b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/resource-layer-no-filter.xml
index 76d65328d8e..2669650cfc7 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/resource-layer-no-filter.xml
+++ b/spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/resources/resource-layer-no-filter.xml
@@ -1,7 +1,7 @@
 <layers xmlns="http://www.springframework.org/schema/boot/layers"
 	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 	xsi:schemaLocation="http://www.springframework.org/schema/boot/layers
-					  https://www.springframework.org/schema/boot/layers/layers-3.5.xsd">
+					  https://www.springframework.org/schema/boot/layers/layers-4.0.xsd">
 	<application>
 		<into layer="my-layer" />
 	</application>