diff --git a/worker/src/archive/detect.test.ts b/worker/src/archive/detect.test.ts
new file mode 100644
index 0000000..49e627e
--- /dev/null
+++ b/worker/src/archive/detect.test.ts
@@ -0,0 +1,39 @@
+import { describe, it, expect } from "vitest";
+import { detectArchive, isArchiveAttachment } from "./detect.js";
+
+describe("detectArchive — 7z numbered multipart (pack.7z.001, pack.7z.002, ...)", () => {
+  it("recognizes a 7z multipart part as an archive attachment", () => {
+    expect(isArchiveAttachment("Lost Adventures Vol2.7z.001")).toBe(true);
+  });
+
+  it("extracts format, baseName, and partNumber", () => {
+    const info = detectArchive("Lost Adventures Vol2.7z.001");
+    expect(info).toEqual({
+      baseName: "Lost Adventures Vol2.7z",
+      partNumber: 1,
+      format: "7Z",
+      pattern: "SEVENZ_NUMBERED",
+    });
+  });
+
+  it("groups multiple parts under the same baseName + format key regardless of part number", () => {
+    const part1 = detectArchive("Lost Adventures Vol2.7z.001");
+    const part2 = detectArchive("Lost Adventures Vol2.7z.010");
+    expect(part1?.baseName).toBe(part2?.baseName);
+    expect(part1?.format).toBe(part2?.format);
+    expect(part2?.partNumber).toBe(10);
+  });
+
+  it("is case-insensitive on the .7z extension", () => {
+    expect(detectArchive("Archive.7Z.002")?.format).toBe("7Z");
+  });
+
+  it("still recognizes a standalone single .7z file", () => {
+    expect(detectArchive("Single Pack.7z")).toEqual({
+      baseName: "Single Pack",
+      partNumber: -1,
+      format: "7Z",
+      pattern: "SINGLE",
+    });
+  });
+});
diff --git a/worker/src/archive/detect.ts b/worker/src/archive/detect.ts
index f4a0c7a..2fe5853 100644
--- a/worker/src/archive/detect.ts
+++ b/worker/src/archive/detect.ts
@@ -4,7 +4,7 @@ export interface MultipartInfo {
   baseName: string;
   partNumber: number;
   format: ArchiveFormat;
-  pattern: "ZIP_NUMBERED" | "ZIP_LEGACY" | "RAR_PART" | "RAR_LEGACY" | "SINGLE";
+  pattern: "ZIP_NUMBERED" | "ZIP_LEGACY" | "RAR_PART" | "RAR_LEGACY" | "SEVENZ_NUMBERED" | "SINGLE";
 }
 
 const patterns: {
@@ -46,6 +46,14 @@ const patterns: {
     getBaseName: (m) => m[1],
     getPartNumber: (m) => parseInt(m[2], 10),
   },
+  // pack.7z.001, pack.7z.002 (native 7z volume split)
+  {
+    regex: /^(.+\.7z)\.(\d{3,})$/i,
+    format: "7Z",
+    pattern: "SEVENZ_NUMBERED",
+    getBaseName: (m) => m[1],
+    getPartNumber: (m) => parseInt(m[2], 10),
+  },
 ];
 
 /** Extensions we recognize as fetchable documents (archives + standalone files) */