diff --git a/extensions/diffs/src/tool.test.ts b/extensions/diffs/src/tool.test.ts
index cefa9518278..28db0d61e53 100644
--- a/extensions/diffs/src/tool.test.ts
+++ b/extensions/diffs/src/tool.test.ts
@@ -397,7 +397,7 @@ describe("diffs tool", () => {
     });
 
     const viewerPath = String((result?.details as Record<string, unknown>).viewerPath);
-    const [id] = viewerPath.split("/").filter(Boolean).slice(-2);
+    const id = extractViewerArtifactId(viewerPath);
     const html = await store.readHtml(id);
     expect(html).toContain('body data-theme="light"');
     expect(html).toContain("--diffs-font-size: 17px;");
@@ -446,7 +446,7 @@ describe("diffs tool", () => {
     expect((result?.details as Record<string, unknown>).fileScale).toBe(2.75);
     expect((result?.details as Record<string, unknown>).fileMaxWidth).toBe(1320);
     const viewerPath = String((result?.details as Record<string, unknown>).viewerPath);
-    const [id] = viewerPath.split("/").filter(Boolean).slice(-2);
+    const id = extractViewerArtifactId(viewerPath);
     const html = await store.readHtml(id);
     expect(html).toContain('body data-theme="dark"');
   });
@@ -580,6 +580,22 @@ function readDetails(result: unknown): Record<string, unknown> {
   return details;
 }
 
+function extractViewerArtifactId(viewerPath: string): string {
+  let previousSegment: string | undefined;
+  let currentSegment: string | undefined;
+  for (const segment of viewerPath.split("/")) {
+    if (segment.length === 0) {
+      continue;
+    }
+    previousSegment = currentSegment;
+    currentSegment = segment;
+  }
+  if (!previousSegment) {
+    throw new Error(`Missing artifact id in viewer path: ${viewerPath}`);
+  }
+  return previousSegment;
+}
+
 function readParametersProperties(parameters: unknown): Record<string, unknown> {
   if (isRecord(parameters) && isRecord(parameters.properties)) {
     return parameters.properties;