diff --git a/visionA-frontend/src/app/devices/[id]/device-detail-client.test.tsx b/visionA-frontend/src/app/devices/[id]/device-detail-client.test.tsx
index 52110ea..7ef6a82 100644
--- a/visionA-frontend/src/app/devices/[id]/device-detail-client.test.tsx
+++ b/visionA-frontend/src/app/devices/[id]/device-detail-client.test.tsx
@@ -192,6 +192,20 @@ describe("DeviceDetailClient serial 路由 gating（WP-C / ADR-018）", () => {
     expect(link).toHaveAttribute("href", "/workspace/dev-1");
   });
 
+  it("flash 完成後開啟工作區入口做醒目樣式（size=lg + 具名 testid，供使用者一眼發現）", () => {
+    useDeviceStore.setState({
+      selectedDevice: { ...onlineDevice, flashedModel: "yolo-v5" },
+    });
+    renderDetail();
+    const btn = screen.getByTestId("device-open-workspace-link");
+    // size=lg → h-10（比其他 default h-9 操作鈕大）
+    expect(btn.className).toContain("h-10");
+    // ring highlight（用設計系統 --primary token，非裸色碼）
+    expect(btn.className).toContain("ring-primary/40");
+    // 仍是可導航的連結入口（維持手動點擊、不自動跳）
+    expect(btn.closest("a")).toHaveAttribute("href", "/workspace/dev-1");
+  });
+
   it("serial 為空：flash 換成 disabled 按鈕、序號欄顯示未回報", () => {
     useDeviceStore.setState({
       selectedDevice: { ...onlineDevice, serialNumber: null },
diff --git a/visionA-frontend/src/app/devices/[id]/device-detail-client.tsx b/visionA-frontend/src/app/devices/[id]/device-detail-client.tsx
index 3dbecdb..bd85217 100644
--- a/visionA-frontend/src/app/devices/[id]/device-detail-client.tsx
+++ b/visionA-frontend/src/app/devices/[id]/device-detail-client.tsx
@@ -23,7 +23,7 @@
 import { useEffect } from "react";
 import Link from "next/link";
 import { useRouter } from "next/navigation";
-import { AlertTriangle, ArrowLeft, Trash2 } from "lucide-react";
+import { AlertTriangle, ArrowLeft, ArrowRight, Trash2 } from "lucide-react";
 import { toast } from "sonner";
 
 import { RemoteDeviceBadge } from "@/components/cloud/remote-device-badge";
@@ -259,7 +259,8 @@ export function DeviceDetailClient({ id }: DeviceDetailClientProps) {
               提早 disable 避免使用者按了才收 400（診斷原始 bug）。
               WP-C（ADR-018）：flash 走 serial 路由，serial 為空時同樣 disable + tooltip。
               flash 完成後 dialog 內部呼叫 fetchDevice → flashedModel 有值 → 下方
-              「開啟工作區」按鈕自動出現（gate 解鎖，無需改 gate 邏輯）。 */}
+              「開啟工作區」按鈕自動出現（gate 解鎖，無需改 gate 邏輯）；該按鈕
+              做醒目樣式（size=lg + 箭頭 + ring highlight）讓完成後易於發現。 */}
           {hasSerial ? (
             <FlashDialog
               deviceId={selectedDevice.id}
@@ -278,9 +279,21 @@ export function DeviceDetailClient({ id }: DeviceDetailClientProps) {
             </Tooltip>
           )}
 
+          {/* flash 完成後的主要動作入口 — 使用者反映原本樣式不明顯要自己找。
+              做法：維持手動導航（點擊才去、不自動 push，避免誤導），但把入口
+              做醒目：size=lg（比其他操作鈕大）+ 前往箭頭圖示 + primary ring
+              highlight（用設計系統 --primary token，不裸寫色碼），讓使用者一眼
+              看到燒錄完成後該點哪。serial 為空時仍走下方 disable 分支（gate 不變）。 */}
           {isOnline && selectedDevice.flashedModel && hasSerial && (
             <Link href={`/workspace/${selectedDevice.id}`}>
-              <Button>{t("devices.openWorkspace")}</Button>
+              <Button
+                size="lg"
+                data-testid="device-open-workspace-link"
+                className="ring-primary/40 ring-2 ring-offset-2"
+              >
+                {t("devices.openWorkspace")}
+                <ArrowRight aria-hidden="true" className="size-4" />
+              </Button>
             </Link>
           )}
           {isOnline && selectedDevice.flashedModel && !hasSerial && (
diff --git a/visionA-frontend/src/lib/i18n/dictionaries/en.ts b/visionA-frontend/src/lib/i18n/dictionaries/en.ts
index adcf1f2..694f525 100644
--- a/visionA-frontend/src/lib/i18n/dictionaries/en.ts
+++ b/visionA-frontend/src/lib/i18n/dictionaries/en.ts
@@ -362,7 +362,7 @@ export const en: Dictionary = {
   "workspace.media.image.primary": "Drag an image here to run inference",
   "workspace.media.image.hint": "JPG or PNG · up to 20 MB",
   "workspace.media.video.primary": "Drag a video here to run inference",
-  "workspace.media.video.hint": "MP4 / AVI / MOV / MPEG · up to 200 MB",
+  "workspace.media.video.hint": "MP4 / AVI / MOV / MPEG · up to 500 MB",
   "workspace.media.video.frame": "Frame",
   "workspace.media.video.seek": "Seek video",
   "workspace.media.batch.primary": "Drag images here (up to 50) for batch inference",
diff --git a/visionA-frontend/src/lib/i18n/dictionaries/zh-Hant.ts b/visionA-frontend/src/lib/i18n/dictionaries/zh-Hant.ts
index 82b66d1..f7a13c9 100644
--- a/visionA-frontend/src/lib/i18n/dictionaries/zh-Hant.ts
+++ b/visionA-frontend/src/lib/i18n/dictionaries/zh-Hant.ts
@@ -350,7 +350,7 @@ export const zhHant: Dictionary = {
   "workspace.media.image.primary": "將圖片拖曳到此處開始推論",
   "workspace.media.image.hint": "JPG 或 PNG · 上限 20 MB",
   "workspace.media.video.primary": "將影片拖曳到此處開始推論",
-  "workspace.media.video.hint": "MP4 / AVI / MOV / MPEG · 上限 200 MB",
+  "workspace.media.video.hint": "MP4 / AVI / MOV / MPEG · 上限 500 MB",
   "workspace.media.video.frame": "影格",
   "workspace.media.video.seek": "影片跳轉",
   "workspace.media.batch.primary": "將圖片拖曳到此處（最多 50 張）進行批次推論",
diff --git a/visionA-frontend/src/lib/media.test.ts b/visionA-frontend/src/lib/media.test.ts
index 840c495..92639e7 100644
--- a/visionA-frontend/src/lib/media.test.ts
+++ b/visionA-frontend/src/lib/media.test.ts
@@ -11,6 +11,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 import {
   MAX_BATCH_IMAGES,
+  MAX_VIDEO_BYTES,
   VIDEO_FALLBACK_FPS,
   buildBatchImageUrl,
   frameToSeekSeconds,
@@ -27,6 +28,16 @@ function makeFile(name: string, sizeBytes = 1024): File {
   return new File([blob], name);
 }
 
+/**
+ * 建立「宣稱」指定 size 的 File，但不實際配置該大小的記憶體。
+ * 用於大檔邊界測試（500 MB 若真配置 Uint8Array 會 OOM）——只覆寫 File.size getter。
+ */
+function makeSizedFile(name: string, sizeBytes: number): File {
+  const file = new File([new Blob([new Uint8Array(8)])], name);
+  Object.defineProperty(file, "size", { value: sizeBytes, configurable: true });
+  return file;
+}
+
 describe("media validation", () => {
   it("圖片：JPG/PNG 通過，其他型別擋 TYPE", () => {
     expect(validateImageFile(makeFile("a.jpg"))).toBeNull();
@@ -48,6 +59,18 @@ describe("media validation", () => {
     expect(validateVideoFile(makeFile("v.jpg"))?.code).toBe("TYPE");
   });
 
+  it("影片：上限為 500 MB（常數校驗）", () => {
+    expect(MAX_VIDEO_BYTES).toBe(500 * 1024 * 1024);
+  });
+
+  it("影片：499 MB 通過，剛好 500 MB 通過，501 MB 擋 SIZE（邊界）", () => {
+    const mb = 1024 * 1024;
+    expect(validateVideoFile(makeSizedFile("v.mp4", 499 * mb))).toBeNull();
+    // 剛好等於上限：validateVideoFile 用 > 判斷，等於上限應通過
+    expect(validateVideoFile(makeSizedFile("v.mp4", 500 * mb))).toBeNull();
+    expect(validateVideoFile(makeSizedFile("v.mp4", 501 * mb))?.code).toBe("SIZE");
+  });
+
   it("批次：空陣列 → EMPTY，超過 50 → COUNT，含非圖 → TYPE", () => {
     expect(validateBatchFiles([])?.code).toBe("EMPTY");
 
diff --git a/visionA-frontend/src/lib/media.ts b/visionA-frontend/src/lib/media.ts
index a9dc981..9a0906b 100644
--- a/visionA-frontend/src/lib/media.ts
+++ b/visionA-frontend/src/lib/media.ts
@@ -91,7 +91,7 @@ export const VIDEO_ACCEPT = ".mp4,.avi,.mov,.mpeg,.mpg";
 
 /** 前端上傳大小上限（防呆；影片經 tunnel 有 timeout 考量，見評估 R-M2）。 */
 export const MAX_IMAGE_BYTES = 20 * 1024 * 1024; // 20 MB
-export const MAX_VIDEO_BYTES = 200 * 1024 * 1024; // 200 MB
+export const MAX_VIDEO_BYTES = 500 * 1024 * 1024; // 500 MB（大檔經 tunnel，caller 端 timeout 設 0 = 不限，見 workspace-client VIDEO_UPLOAD_TIMEOUT_MS）
 
 export interface UploadMediaOptions {
   /** 上傳進度 callback（0~100） */