diff --git a/visionA-frontend/src/lib/i18n/dictionaries/en.ts b/visionA-frontend/src/lib/i18n/dictionaries/en.ts
index 694f525..8303ec6 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 500 MB",
+  "workspace.media.video.hint": "MP4 / AVI / MOV / MPEG · up to 90 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 f7a13c9..b1871fd 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 500 MB",
+  "workspace.media.video.hint": "MP4 / AVI / MOV / MPEG · 上限 90 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 92639e7..f5c32f8 100644
--- a/visionA-frontend/src/lib/media.test.ts
+++ b/visionA-frontend/src/lib/media.test.ts
@@ -59,16 +59,16 @@ 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：上限為 90 MB（常數校驗）", () => {
+    expect(MAX_VIDEO_BYTES).toBe(90 * 1024 * 1024);
   });
 
-  it("影片：499 MB 通過，剛好 500 MB 通過，501 MB 擋 SIZE（邊界）", () => {
+  it("影片：89 MB 通過，剛好 90 MB 通過，91 MB 擋 SIZE（邊界）", () => {
     const mb = 1024 * 1024;
-    expect(validateVideoFile(makeSizedFile("v.mp4", 499 * mb))).toBeNull();
+    expect(validateVideoFile(makeSizedFile("v.mp4", 89 * 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");
+    expect(validateVideoFile(makeSizedFile("v.mp4", 90 * mb))).toBeNull();
+    expect(validateVideoFile(makeSizedFile("v.mp4", 91 * mb))?.code).toBe("SIZE");
   });
 
   it("批次：空陣列 → EMPTY，超過 50 → COUNT，含非圖 → TYPE", () => {
diff --git a/visionA-frontend/src/lib/media.ts b/visionA-frontend/src/lib/media.ts
index 9a0906b..9ae4a5a 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 = 500 * 1024 * 1024; // 500 MB（大檔經 tunnel，caller 端 timeout 設 0 = 不限，見 workspace-client VIDEO_UPLOAD_TIMEOUT_MS）
+export const MAX_VIDEO_BYTES = 90 * 1024 * 1024; // 90 MB（過渡值：對齊 nginx client_max_body_size 100M，留 10 MB buffer 給 multipart overhead，避免 HTTP 413。未來影片走 localhost 直連後可放寬）
 
 export interface UploadMediaOptions {
   /** 上傳進度 callback（0~100） */