diff --git a/apps/web/src/api/assets/upload.ts b/apps/web/src/api/assets/upload.ts
index 3a452945d..490b08df7 100644
--- a/apps/web/src/api/assets/upload.ts
+++ b/apps/web/src/api/assets/upload.ts
@@ -32,6 +32,8 @@ export const completeDirectUpload = async (data: {
   file_hash?: string
   /** 前端上传幂等 token（与 prepare 一致），同一次上传重发 complete 不重复建记录 */
   client_upload_id?: string
+  /** 文件字节数；后端同名兜底去重需用它做大小校验，缺失（=0）时同名记录一律不判重 */
+  file_size?: number
 }): Promise<DirectUploadCompleteResult> => {
   // complete 内含 OSS 存在性检查 + 建库 + 派单，放宽到 60s；
   // 超时不代表失败（记录可能已建成），调用方禁止超时后盲目重传整个文件
@@ -156,6 +158,8 @@ export const prepareDirectUploadHandle = async (data: {
         storage_key: prepared.storage_key,
         file_hash: data.fileHash,
         client_upload_id: data.clientUploadId,
+        // 透传文件字节数：后端同名兜底去重依赖大小校验，缺省会导致同名新视频被误判重复
+        file_size: data.file.size,
       }),
   }
 }
diff --git a/apps/web/src/test/api/assets.test.ts b/apps/web/src/test/api/assets.test.ts
index 90967f1f5..cce914b2e 100644
--- a/apps/web/src/test/api/assets.test.ts
+++ b/apps/web/src/test/api/assets.test.ts
@@ -242,6 +242,20 @@ describe("assets API", () => {
       await expect(completeDirectUpload({ name: "test-item" })).resolves.not.toThrow()
     })
 
+    it("请求体携带 file_size（后端同名兜底去重的大小校验依赖它）", async () => {
+      await completeDirectUpload({
+        project_id: "p-1",
+        library_id: "l-1",
+        storage_key: "uploads/k.mp4",
+        file_size: 12345,
+      } as never)
+      const completeCalls = mockPost.mock.calls.filter(
+        ([u]: [string]) => u === "/upload/direct/complete",
+      )
+      expect(completeCalls).toHaveLength(1)
+      expect(completeCalls[0][1]).toMatchObject({ file_size: 12345 })
+    })
+
     it("should reject on API error", async () => {
       mockGet.mockRejectedValue(new Error("Network error"))
       mockPost.mockRejectedValue(new Error("Network error"))
@@ -354,6 +368,8 @@ describe("assets API", () => {
         ([u]: [string]) => u === "/upload/direct/complete",
       )
       expect(completeCalls).toHaveLength(1)
+      // complete 请求必须带上 file_size，否则后端同名兜底会误杀同名新视频
+      expect(completeCalls[0][1]).toMatchObject({ file_size: file.size })
       XMLHttpRequest.prototype.open = origOpen
       XMLHttpRequest.prototype.send = origSend
       if (origSetReadyState) {