diff --git a/src/domain/artifactComparison.ts b/src/domain/artifactComparison.ts
index a9f69be471..b3542d7f98 100644
--- a/src/domain/artifactComparison.ts
+++ b/src/domain/artifactComparison.ts
@@ -538,6 +538,11 @@ const relationsByPath = (
           ? null
           : (occurrences.get(occurrence.parent_occurrence_id)?.logical_path ??
             null),
+      // Containment roots are path-normalized to avoid graph-wide deltas, but
+      // a source map's target is a semantic content identity, not its parent
+      // directory. Preserve that identity in the relation comparison.
+      mapped_artifact_id:
+        edge.relation === "maps-source" ? edge.parent_artifact_id : null,
       child_artifact_id: occurrence.artifact_id,
       relation: edge.relation,
       logical_path: occurrence.logical_path,
@@ -556,6 +561,8 @@ const relationsByPath = (
 interface RelationProjection {
   /** Logical parent is stable across graph-root ID changes. */
   readonly parent_logical_path: string | null;
+  /** Content identity is material for a maps-source edge. */
+  readonly mapped_artifact_id: string | null;
   readonly child_artifact_id: string;
   readonly relation: ArtifactInventoryResult["edges"][number]["relation"];
   readonly logical_path: string | null;
diff --git a/tests/boundary/filesystem/artifactComparison.test.ts b/tests/boundary/filesystem/artifactComparison.test.ts
index a34cb46758..4b9b07321f 100644
--- a/tests/boundary/filesystem/artifactComparison.test.ts
+++ b/tests/boundary/filesystem/artifactComparison.test.ts
@@ -571,6 +571,49 @@ describe("artifact comparison completeness", () => {
 });
 
 describe("artifact source-map relationship coverage", () => {
+  it("reports when an unchanged map points to changed source content", async () => {
+    const root = await createTestTempDirectory("rea-map-target-change-");
+    const leftPath = join(root, "left");
+    const rightPath = join(root, "right");
+    await Promise.all([mkdir(leftPath), mkdir(rightPath)]);
+    await Promise.all([
+      writeFile(join(leftPath, "main.js"), "/* first source */\n"),
+      writeFile(join(rightPath, "main.js"), "/* second source */\n"),
+      writeFile(
+        join(leftPath, "main.js.map"),
+        '{"version":3,"sources":[],"names":[],"mappings":""}',
+      ),
+      writeFile(
+        join(rightPath, "main.js.map"),
+        '{"version":3,"sources":[],"names":[],"mappings":""}',
+      ),
+    ]);
+    const [left, right] = await Promise.all([
+      observe(leftPath),
+      observe(rightPath),
+    ]);
+
+    const comparison = compareArtifacts(left, right);
+    const leftInventory = parseArtifactInventoryEvidence(left).inventory;
+    const rightInventory = parseArtifactInventoryEvidence(right).inventory;
+    const leftMap = leftInventory.occurrences.find(
+      ({ logical_path }) => logical_path === "main.js.map",
+    );
+    const rightMap = rightInventory.occurrences.find(
+      ({ logical_path }) => logical_path === "main.js.map",
+    );
+    expect(leftMap?.artifact_id).toBe(rightMap?.artifact_id);
+    expect(comparison.changes).toContainEqual(
+      expect.objectContaining({
+        logical_path: "main.js.map",
+        classification: "changed",
+        dimensions: ["relations"],
+        left_artifact_id: leftMap?.artifact_id,
+        right_artifact_id: rightMap?.artifact_id,
+      }),
+    );
+  });
+
   it("preserves unknown source-map relationships for duplicate ZIP paths", async () => {
     const root = await createTestTempDirectory("rea-duplicate-source-map-");
     const path = join(root, "duplicate-source-map.zip");