diff --git a/src/domain/zipPackageFormat.ts b/src/domain/zipPackageFormat.ts
index 26f8af7c16..2a90e288aa 100644
--- a/src/domain/zipPackageFormat.ts
+++ b/src/domain/zipPackageFormat.ts
@@ -17,13 +17,14 @@ export const isZipPackageFormat = (
 ): format is ZipPackageFormat =>
   ZIP_PACKAGE_FORMATS.some((candidate) => candidate === format);
 
-/** Recognize local-header, empty-archive, or split-archive ZIP signatures, not archive validity. */
+/** Recognize local-header, classic/Zip64 empty-archive, or split ZIP signatures, not validity. */
 export const hasZipSignature = (bytes: Uint8Array): boolean =>
   bytes.length >= 4 &&
   bytes[0] === 0x50 &&
   bytes[1] === 0x4b &&
   ((bytes[2] === 0x03 && bytes[3] === 0x04) ||
     (bytes[2] === 0x05 && bytes[3] === 0x06) ||
+    (bytes[2] === 0x06 && bytes[3] === 0x06) ||
     (bytes[2] === 0x07 && bytes[3] === 0x08));
 
 const END_OF_CENTRAL_DIRECTORY = 0x06054b50;
diff --git a/tests/boundary/filesystem/artifactZipIntegrity.test.ts b/tests/boundary/filesystem/artifactZipIntegrity.test.ts
index 0f098fb05c..b771df65f7 100644
--- a/tests/boundary/filesystem/artifactZipIntegrity.test.ts
+++ b/tests/boundary/filesystem/artifactZipIntegrity.test.ts
@@ -1,8 +1,9 @@
-import { mkdir, readFile, readdir, writeFile } from "node:fs/promises";
+import { createHash } from "node:crypto";
+import { mkdir, readFile, readdir, rm, writeFile } from "node:fs/promises";
 import { join } from "node:path";
 
 import { TextReader, Uint8ArrayWriter, ZipWriter } from "@zip.js/zip.js";
-import { expect, it } from "vitest";
+import { expect, it, onTestFinished } from "vitest";
 
 import { writeOrderedZip } from "../../fixtures/artifactEntryOrder.js";
 import { inventoryArtifact } from "../../fixtures/artifactInventory.js";
@@ -23,27 +24,69 @@ import {
 import { artifactInspectionResultSchema } from "../../../src/domain/artifactInspection.js";
 import { parseEvidence } from "../../../src/domain/evidence.js";
 
-it("completes an empty ZIP extraction with an empty identity", async () => {
-  const root = await createTestTempDirectory("rea-empty-artifact-extraction-");
-  const archive = join(root, "empty.zip");
-  await writeOrderedZip(archive, []);
-  const archiveTarget = await parseBinaryTarget(archive);
-  if (!archiveTarget.ok) throw archiveTarget.error;
-
-  const output = join(root, "output");
-  const result = await withArtifactClient(archiveTarget.value, (client) =>
-    client.execute("extract_artifact", { output_root: output }),
+for (const zip64 of [false, true]) {
+  cliTest(
+    `inspects and extracts an empty ${zip64 ? "Zip64" : "classic ZIP"} without changing its identity`,
+    async ({ cli }) => {
+      const root = await createTestTempDirectory(
+        "rea-empty-artifact-extraction-",
+      );
+      const archive = join(root, "empty.zip");
+      const writer = new ZipWriter(new Uint8ArrayWriter(), {
+        zip64,
+        supportZip64SplitFile: false,
+      });
+      const bytes = Buffer.from(await writer.close());
+      await writeFile(archive, bytes);
+      const digest = createHash("sha256").update(bytes).digest("hex");
+      const inventory = await inventoryArtifact(archive);
+      expect(inventory.manifest).toMatchObject({
+        root_sha256: digest,
+        root_format: "zip",
+      });
+      expect(inventory.coverage).toEqual({
+        scope: "container-entries",
+        status: "complete",
+      });
+      const inspected = await cli.run({
+        arguments: ["inspect-artifact", archive, "--json"],
+      });
+      expect(inspected.exitCode, inspected.stdout + inspected.stderr).toBe(0);
+      const inspection = artifactInspectionResultSchema.parse(
+        parseEvidence(inspected.json).normalized_result,
+      );
+      const retained = artifactInventoryResultSchema.parse(
+        inspection.substeps[0]?.evidence?.normalized_result,
+      );
+      expect(retained.manifest).toMatchObject({
+        root_sha256: digest,
+        root_format: "zip",
+      });
+      const extracted = await cli.run({
+        arguments: ["extract-artifact", archive, "--json"],
+      });
+      expect(extracted.exitCode, extracted.stdout + extracted.stderr).toBe(0);
+      const extraction = artifactExtractionResultSchema.parse(
+        parseEvidence(extracted.json).normalized_result,
+      );
+      onTestFinished(() =>
+        rm(extraction.output_root, { recursive: true, force: true }),
+      );
+      expect(extraction.manifest).toMatchObject({
+        root_sha256: digest,
+        root_format: "zip",
+      });
+      expect(extraction.extraction_manifest).toMatchObject({
+        source_manifest_id: extraction.manifest.manifest_id,
+        selected_occurrence_ids: [],
+      });
+      expect(extraction.artifacts).toEqual([]);
+      expect(extraction.containment_verified).toBe(true);
+      expect(await readdir(extraction.output_root)).toEqual([]);
+      expect(await readFile(archive)).toEqual(bytes);
+    },
   );
-  if (!result.ok) throw result.error;
-  const extraction = artifactExtractionResultSchema.parse(result.value.result);
-  expect(extraction.extraction_manifest).toMatchObject({
-    source_manifest_id: extraction.manifest.manifest_id,
-    selected_occurrence_ids: [],
-  });
-  expect(extraction.artifacts).toEqual([]);
-  expect(extraction.containment_verified).toBe(true);
-  expect(await readdir(output)).toEqual([]);
-});
+}
 
 const legacyControlNames = [
   ["unflagged UTF-8-looking legacy bytes", Buffer.from("café"), false, "caf├⌐"],
@@ -573,17 +616,22 @@ it("preserves encrypted-member and corrupt-CRC observations", async () => {
   );
 });
 
-it("rejects a truncated ZIP through artifact inventory", async () => {
-  const root = await createTestTempDirectory("rea-zip-malformed-");
-  const path = join(root, "truncated.zip");
-  await writeFile(path, Buffer.from([0x50, 0x4b, 0x03, 0x04]));
+it.each([0x04034b50, 0x06064b50])(
+  "rejects a truncated ZIP signature %i through artifact inventory",
+  async (signature) => {
+    const root = await createTestTempDirectory("rea-zip-malformed-");
+    const path = join(root, "truncated.zip");
+    const bytes = Buffer.alloc(4);
+    bytes.writeUInt32LE(signature);
+    await writeFile(path, bytes);
 
-  await expectInventoryFailure(
-    path,
-    "format",
-    "ZIP archive is malformed: File format is not recognized",
-  );
-});
+    await expectInventoryFailure(
+      path,
+      "format",
+      "ZIP archive is malformed: File format is not recognized",
+    );
+  },
+);
 
 it("reports an unsupported ZIP compression method as unavailable", async () => {
   const root = await createTestTempDirectory("rea-zip-method-");