diff --git a/README.md b/README.md
index f7d4300..2bcf914 100644
--- a/README.md
+++ b/README.md
@@ -99,7 +99,7 @@ npm start
 - 新版素材库只在列表中返回 `ready` 素材；`pending` / `failed` 通过单素材接口查询。
 - 视频生成应长期保存素材库返回的 `asset://...` 引用，不要依赖原始图片 URL。
 - 参考图/参考视频/首帧/首尾帧属于不同互斥调用方式；本 Demo 采用“多模态参考图”方式。
-- 默认视频 720p，时长 4–15 秒；真人/数字人必须使用审核通过的 `mat_*` 素材 ID。
+- 默认视频 720p，时长可选 5–14 秒整数；真人/数字人必须使用审核通过的 `mat_*` 素材 ID。
 
 接口依据：[快快 AI Hub 最新文档](https://ai.kkidc.com/api-docs/8238027m0)。
 
diff --git a/public/app.js b/public/app.js
index 27942d0..241055c 100644
--- a/public/app.js
+++ b/public/app.js
@@ -456,6 +456,8 @@ function switchModule(module) {
 }
 
 function createShot(seed = {}, index = state.shots.length) {
+  const seedDuration = Number(seed.duration);
+  const duration = Number.isFinite(seedDuration) ? Math.min(14, Math.max(5, Math.round(seedDuration))) : 5;
   return {
     id: seed.id || `shot-${Date.now()}-${Math.random().toString(36).slice(2, 7)}`,
     title: seed.title || (index === 0 ? "电梯口对话" : `片段 ${String(index + 1).padStart(2, "0")}`),
@@ -466,7 +468,7 @@ function createShot(seed = {}, index = state.shots.length) {
     roleIds: Array.isArray(seed.roleIds) ? [...seed.roleIds] : state.roles.map((role) => role.id),
     model: seed.model || "doubao-seedance-2-0-260128",
     ratio: seed.ratio || "9:16",
-    duration: Number(seed.duration) || 5,
+    duration,
     resolution: seed.resolution || "720p",
     generateAudio: seed.generateAudio !== false,
     watermark: Boolean(seed.watermark),
diff --git a/public/index.html b/public/index.html
index 0c562d3..ebef5c2 100644
--- a/public/index.html
+++ b/public/index.html
@@ -204,9 +204,15 @@
               <span>时长</span>
               <select id="duration">
                 <option value="5">5 秒</option>
+                <option value="6">6 秒</option>
+                <option value="7">7 秒</option>
                 <option value="8">8 秒</option>
+                <option value="9">9 秒</option>
                 <option value="10">10 秒</option>
-                <option value="15">15 秒</option>
+                <option value="11">11 秒</option>
+                <option value="12">12 秒</option>
+                <option value="13">13 秒</option>
+                <option value="14">14 秒</option>
               </select>
             </label>
             <label class="field">
@@ -283,6 +289,6 @@
     </div>
 
     <div class="toast hidden" id="toast"></div>
-    <script src="./app.js?v=29"></script>
+    <script src="./app.js?v=30"></script>
   </body>
 </html>
diff --git a/server.mjs b/server.mjs
index ff24905..ea0f767 100644
--- a/server.mjs
+++ b/server.mjs
@@ -534,10 +534,6 @@ function requireCustomerToken(request, taskId = "") {
   return token;
 }
 
-function clamp(value, min, max) {
-  return Math.min(max, Math.max(min, value));
-}
-
 function resolveResolution(model = "", requested = "720p") {
   return requested === "480p" ? "480p" : "720p";
 }
@@ -562,6 +558,10 @@ function buildVideoPayload(body) {
     throw new ClientError("参考视频最多 3 条，且必须是公网可访问的 MP4/MOV URL");
   }
   if (!String(body.prompt || "").trim()) throw new ClientError("请填写分镜提示词");
+  const duration = Number(body.duration);
+  if (!Number.isInteger(duration) || duration < 5 || duration > 14) {
+    throw new ClientError("视频时长必须是 5～14 秒之间的整数");
+  }
   return {
     model: resolveVideoModel(body.model),
     content: [
@@ -577,7 +577,7 @@ function buildVideoPayload(body) {
         role: "reference_video",
       })),
     ],
-    duration: clamp(Number(body.duration || 5), 4, 15),
+    duration,
     resolution: resolveResolution(body.model, body.resolution),
     ratio: body.ratio || "9:16",
     generate_audio: body.generateAudio !== false,
diff --git a/tests/normalize.test.mjs b/tests/normalize.test.mjs
index 7077ca9..46a2bbf 100644
--- a/tests/normalize.test.mjs
+++ b/tests/normalize.test.mjs
@@ -1,5 +1,6 @@
 import test from "node:test";
 import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
 import {
   extractVideoTaskId,
   extractVideoUrl,
@@ -24,3 +25,10 @@ test("兼容视频任务 id 和状态字段", () => {
 test("从常见响应位置提取视频地址", () => {
   assert.equal(extractVideoUrl({ output: { video_url: "https://example.com/demo.mp4" } }), "https://example.com/demo.mp4");
 });
+
+test("生成时长提供 5 到 14 秒全部整数选项", () => {
+  const html = readFileSync(new URL("../public/index.html", import.meta.url), "utf8");
+  const durationSelect = html.match(/<select id="duration">([\s\S]*?)<\/select>/)?.[1] || "";
+  const values = [...durationSelect.matchAll(/<option value="(\d+)">/g)].map((match) => Number(match[1]));
+  assert.deepEqual(values, [5, 6, 7, 8, 9, 10, 11, 12, 13, 14]);
+});