diff --git a/build-logic/plugins/src/main/groovy/org/apache/grails/buildsrc/SbomPlugin.groovy b/build-logic/plugins/src/main/groovy/org/apache/grails/buildsrc/SbomPlugin.groovy
index 7af23167462..db20a07e60b 100644
--- a/build-logic/plugins/src/main/groovy/org/apache/grails/buildsrc/SbomPlugin.groovy
+++ b/build-logic/plugins/src/main/groovy/org/apache/grails/buildsrc/SbomPlugin.groovy
@@ -140,7 +140,10 @@ class SbomPlugin implements Plugin<Project> {
         configureNormalization(project)
         ensureLicensesValidated(project)
 
-        // sboms are only published to Grails jar files at this time
+        // sboms are only published to Grails jar files at this time. Projects that produce a fat
+        // jar via com.gradleup.shadow are responsible for wiring the SBOM into their shadowJar
+        // task in their own build.gradle (see grails-forge/grails-cli/build.gradle), since fat-jar
+        // packaging is a project-specific concern and shadow is not a dependency of this plugin.
         publishSbomForJarProjects(project, sbomOutputLocation)
     }
 
@@ -261,10 +264,20 @@ class SbomPlugin implements Plugin<Project> {
                             }
                         }
 
-                        // force the serialNumber to be reproducible by removing it & recalculating
+                        // force the serialNumber to be reproducible by clearing it & recalculating.
+                        // Mix the projectPath into the UUID seed so two modules whose post-processed
+                        // BOM JSON happens to be identical (for example, empty BOM platforms with no
+                        // runtime dependencies, or modules whose metadata.component is filled in
+                        // identically by the CycloneDX plugin) still receive distinct serialNumbers
+                        // as required by the CycloneDX specification. Including projectPath preserves
+                        // reproducibility because the same project path + same content always yields
+                        // the same UUID across rebuilds. This guards against collisions introduced by
+                        // CycloneDX 3.0.0 / Gradle 9 metadata changes.
+                        // See: https://cyclonedx.org/docs/1.6/json/#serialNumber
                         bom['serialNumber'] = ''
-                        def withOutSerial = JsonOutput.prettyPrint(JsonOutput.toJson(bom))
-                        def uuid = UUID.nameUUIDFromBytes(withOutSerial.getBytes(StandardCharsets.UTF_8.name()))
+                        def withoutSerial = JsonOutput.prettyPrint(JsonOutput.toJson(bom))
+                        def uuidSeed = "${projectPath}\n${withoutSerial}"
+                        def uuid = UUID.nameUUIDFromBytes(uuidSeed.getBytes(StandardCharsets.UTF_8))
                         bom['serialNumber'] = "urn:uuid:$uuid".toString()
 
                         f.setText(JsonOutput.prettyPrint(JsonOutput.toJson(bom)), StandardCharsets.UTF_8.name())
diff --git a/grails-forge/grails-cli-shadow/build.gradle b/grails-forge/grails-cli-shadow/build.gradle
index 6978124d70c..21c1ee17e80 100644
--- a/grails-forge/grails-cli-shadow/build.gradle
+++ b/grails-forge/grails-cli-shadow/build.gradle
@@ -77,6 +77,12 @@ shadowJarTask.configure { ShadowJar it ->
 
     it.exclude(
             'META-INF/DEPENDENCIES', // until we publish our own SBOM, this won't be correct so exclude
+            // This module does not apply org.apache.grails.buildsrc.sbom (it's an intermediate build
+            // artifact, not published). Without this exclude, shadow's first-wins merge picks one of
+            // the bundled transitive META-INF/sbom.json files (typically grails-shell-cli's),
+            // producing a fat jar whose SBOM describes the wrong module and shares its serialNumber
+            // with whichever sibling jar happens to win the merge - violating CycloneDX 1.6.
+            'META-INF/sbom.json',
             'about.html' // restatement of the Eclipse Distribution License - Version 1.0 for jakarta
     )
 }
diff --git a/grails-forge/grails-cli/build.gradle b/grails-forge/grails-cli/build.gradle
index 79b4657d98c..1f16d876cf3 100644
--- a/grails-forge/grails-cli/build.gradle
+++ b/grails-forge/grails-cli/build.gradle
@@ -18,6 +18,7 @@ import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 import org.apache.grails.forge.buildlogic.shadowjar.GrailsGroovyExtensionTransformer
 import org.apache.grails.forge.buildlogic.shadowjar.GrailsShadowLicenseTransform
 import org.apache.grails.forge.buildlogic.shadowjar.GrailsShadowNoticeTransform
+import org.cyclonedx.gradle.CyclonedxDirectTask
 
 plugins {
     id 'groovy'
@@ -92,6 +93,16 @@ jarTask.configure { Jar it ->
     }
 }
 
+// The shadowJar merges multiple jars (including transitive ones from grails-shell-cli, grails-forge-cli,
+// etc.) into a single fat jar. Each of those source jars carries its own META-INF/sbom.json published by
+// the org.apache.grails.buildsrc.sbom convention plugin, and shadow's first-wins merge would otherwise
+// pick a transitive sbom.json (typically grails-shell-cli's) and produce a fat jar whose SBOM describes
+// the wrong module. We exclude any incoming META-INF/sbom.json during the merge and then re-introduce
+// this project's own SBOM (whose serialNumber is project-path-seeded and unique). This keeps fat-jar
+// packaging concerns local to this project rather than leaking shadow knowledge into the generic
+// org.apache.grails.buildsrc.sbom plugin. See: https://cyclonedx.org/docs/1.6/json/#serialNumber
+TaskProvider<CyclonedxDirectTask> cyclonedxDirectBomTask = tasks.named('cyclonedxDirectBom', CyclonedxDirectTask)
+
 TaskProvider<Jar> shadowJarTask = tasks.named('shadowJar', ShadowJar)
 shadowJarTask.configure { ShadowJar it ->
     it.archiveClassifier = 'all'
@@ -122,8 +133,27 @@ shadowJarTask.configure { ShadowJar it ->
             'META-INF/DEPENDENCIES', // until we publish our own SBOM, this won't be correct so exclude
             'META-INF/grails-plugin.xml', // we do not start or compile a grails application so these files are not needed (grails-core, url mappings, etc plugins)
             'META-INF/grails-plugin.xml.asc', // avoid signing artifacts
+            // Drop any incoming sbom.json that arrives via transitive jars during the shadow merge;
+            // re-introduced below from this project's own cyclonedxDirectBom output.
+            'META-INF/sbom.json',
             'about.html' // restatement of the Eclipse Distribution License - Version 1.0 for jakarta
     )
+
+    // Re-introduce this project's own SBOM after the merge (mirrors the regular jar wiring done by
+    // the org.apache.grails.buildsrc.sbom plugin). Mirrored only when skipJavaComponent is unset to
+    // match the convention used elsewhere in the build for projects that opt out of jar publication.
+    if (!project.findProperty('skipJavaComponent')) {
+        it.from(cyclonedxDirectBomTask.flatMap { CyclonedxDirectTask t -> t.jsonOutput }) { CopySpec spec ->
+            spec.into('META-INF')
+            spec.rename {
+                'sbom.json'
+            }
+        }
+        it.manifest { Manifest manifest ->
+            manifest.attributes('Sbom-Location': 'META-INF/sbom.json')
+            manifest.attributes('Sbom-Format': 'CycloneDX')
+        }
+    }
 }
 // Make shadow jar a direct dependency of assemble instead of using deprecated archives configuration
 tasks.named('assemble').configure {