diff --git a/src/commands/manifest/scripts/assemble.mts b/src/commands/manifest/scripts/assemble.mts
index f4501a310..5634146c1 100644
--- a/src/commands/manifest/scripts/assemble.mts
+++ b/src/commands/manifest/scripts/assemble.mts
@@ -54,7 +54,11 @@ export function assembleFacts(
   const { directByRoot, finalNodes } = mergeByCoordinate(perRoot)
 
   const tool = (parsed.tool || 'gradle') as SocketFactsSbomMetadata['tool']
-  const components = buildComponents(finalNodes)
+  const projectsByGav = new Map<string, RawProject>()
+  for (const p of parsed.projects.values()) {
+    projectsByGav.set(gav(p.group, p.name, p.version), p)
+  }
+  const components = buildComponents(finalNodes, projectsByGav)
   const projects =
     opts.emitProjects === false
       ? []
@@ -77,6 +81,7 @@ export function assembleFacts(
     artifactPaths: buildArtifactPaths(
       finalNodes,
       [...parsed.projects.values()],
+      projectsByGav,
       perRoot,
       fileExists,
     ),
@@ -173,6 +178,7 @@ function mergeByCoordinate(perRoot: Map<string, PerRoot>): {
 
 function buildComponents(
   finalNodes: Map<string, MergedNode>,
+  projectsByGav: Map<string, RawProject>,
 ): SocketFactsSbomComponent[] {
   return [...finalNodes.keys()].sort().map(id => {
     const fn = finalNodes.get(id)!
@@ -200,6 +206,9 @@ function buildComponents(
     if (!fn.prod) {
       comp.dev = true
     }
+    if (projectsByGav.has(gav(c.group, c.name, c.version ?? ''))) {
+      comp.firstParty = true
+    }
     if (fn.children.size) {
       comp.dependencies = [...fn.children].sort()
     }
@@ -303,19 +312,10 @@ function buildClasspathByProject(
 function buildArtifactPaths(
   finalNodes: Map<string, MergedNode>,
   projects: RawProject[],
+  projectsByGav: Map<string, RawProject>,
   perRoot: Map<string, PerRoot>,
   fileExists: (path: string) => boolean,
 ): ResolvedArtifactPaths {
-  const projectsByGav = new Map<
-    string,
-    { sources: string[]; targets: string[] }
-  >()
-  for (const p of projects) {
-    projectsByGav.set(gav(p.group, p.name, p.version), {
-      sources: p.sources,
-      targets: p.targets,
-    })
-  }
   const targetsByCoord = new Map<string, string[]>()
   const targetsByGav = new Map<string, string[]>()
   const sourcesByCoord = new Map<string, string[]>()
diff --git a/src/commands/manifest/scripts/assemble.test.mts b/src/commands/manifest/scripts/assemble.test.mts
index af78da6d9..52a01a073 100644
--- a/src/commands/manifest/scripts/assemble.test.mts
+++ b/src/commands/manifest/scripts/assemble.test.mts
@@ -116,4 +116,37 @@ describe('records → assemble → sidecar', () => {
       'g:lib:jar:1',
     ])
   })
+  it('marks only components with the exact coordinate of a build module as firstParty', () => {
+    const records = [
+      'meta\tmaven\t3.9.6\t17',
+      'project\t:a\tg\ta\t1.0-SNAPSHOT\ta',
+      'project\t:b\tg\tb\t1.0-SNAPSHOT\tb',
+      'root\tr1\t:a\truntimeClasspath\t1',
+      'node\tr1\tg:ext:jar:2\tg\text\t2\tjar\t\t1',
+      'root\tr2\t:b\truntimeClasspath\t1',
+      'node\tr2\tg:a:jar:1.0-SNAPSHOT\tg\ta\t1.0-SNAPSHOT\tjar\t\t1',
+      'node\tr2\tg:ext:jar:2\tg\text\t2\tjar\t\t0',
+      'edge\tr2\tg:a:jar:1.0-SNAPSHOT\tg:ext:jar:2',
+      'node\tr2\tg:b:jar:0.9\tg\tb\t0.9\tjar\t\t1',
+    ].join('\n')
+    const { artifactPaths, facts } = assembleFacts(parseRecords(records))
+
+    expect(facts.components.map(c => [c.id, c.firstParty ?? 'absent'])).toEqual(
+      [
+        ['g:a:jar:1.0-SNAPSHOT', true],
+        ['g:b:jar:0.9', 'absent'],
+        ['g:ext:jar:2', 'absent'],
+      ],
+    )
+
+    const acc: SidecarAccumulator = new Map()
+    accumulateSidecar(acc, facts, artifactPaths, '/abs/.socket.facts.json')
+    const bucket = serializeSidecar(acc)['/abs/.socket.facts.json']!
+    expect(
+      bucket.components.find(c => c.id === 'g:a:jar:1.0-SNAPSHOT')?.firstParty,
+    ).toBe(true)
+    for (const project of bucket.projects) {
+      expect(project).not.toHaveProperty('firstParty')
+    }
+  })
 })
diff --git a/src/commands/manifest/scripts/facts.mts b/src/commands/manifest/scripts/facts.mts
index 1ff25965f..aab42c0d2 100644
--- a/src/commands/manifest/scripts/facts.mts
+++ b/src/commands/manifest/scripts/facts.mts
@@ -27,6 +27,8 @@ export type SocketFactsSbomComponent = AnyPURL & {
   id: string
   direct?: boolean | undefined
   dev?: boolean | undefined
+  // A module of the scanned build itself (same GAV as a projects[] entry).
+  firstParty?: true | undefined
   dependencies?: string[] | undefined
 }