diff --git a/admin-web/src/views/ModelService.vue b/admin-web/src/views/ModelService.vue
index 1c649f6..524cb62 100644
--- a/admin-web/src/views/ModelService.vue
+++ b/admin-web/src/views/ModelService.vue
@@ -201,7 +201,7 @@ function sourceLabel(source: ApiKeyState['source']) {
               <a-button danger :loading="deletingKey">删除</a-button>
             </a-popconfirm>
           </div>
-          <p class="key-note">服务端需配置 <code>Secrets__EncryptionKey</code> 才能加密保存，值为 Base64 编码的 32 字节密钥。</p>
+          <p class="key-note">保存时由服务端自动加密，不需要额外配置加密密钥。</p>
         </template>
         <a-alert v-else type="info" message="只有超级管理员可以替换或删除 API Key。" show-icon />
       </section>
@@ -234,7 +234,6 @@ function sourceLabel(source: ApiKeyState['source']) {
 .key-status strong { font-variant-numeric: tabular-nums; letter-spacing: .04em; }
 .key-editor { display: grid; grid-template-columns: minmax(240px, 1fr) auto auto; gap: 10px; }
 .key-note { margin: 10px 0 0; color: #5e6772; font-size: 12px; }
-.key-note code { color: #414eb8; }
 .result-alert { margin-bottom: 18px; }
 @media (max-width: 760px) {
   .page-heading { flex-direction: column; }
diff --git a/backend/MiaoJiZhang.Api.Tests/LlmConfigurationTests.cs b/backend/MiaoJiZhang.Api.Tests/LlmConfigurationTests.cs
index 087586c..04a74d9 100644
--- a/backend/MiaoJiZhang.Api.Tests/LlmConfigurationTests.cs
+++ b/backend/MiaoJiZhang.Api.Tests/LlmConfigurationTests.cs
@@ -9,11 +9,11 @@ public sealed class LlmSecretProtectorTests
     [Fact]
     public void Protect_RoundTripsWithoutEmbeddingPlaintext()
     {
-        var encryptionKey = Convert.ToBase64String(RandomNumberGenerator.GetBytes(32));
         var configuration = new ConfigurationBuilder()
             .AddInMemoryCollection(new Dictionary<string, string?>
             {
-                ["Secrets:EncryptionKey"] = encryptionKey,
+                ["Jwt:Secret"] = Convert.ToBase64String(
+                    RandomNumberGenerator.GetBytes(48)),
             })
             .Build();
         var protector = new LlmSecretProtector(configuration);
@@ -26,14 +26,14 @@ public sealed class LlmSecretProtectorTests
     }
 
     [Fact]
-    public void Protect_RejectsMissingEncryptionKey()
+    public void Protect_RejectsMissingServerSecret()
     {
         var protector = new LlmSecretProtector(new ConfigurationBuilder().Build());
 
         var exception = Assert.Throws<InvalidOperationException>(
             () => protector.Protect("sk-test"));
 
-        Assert.Contains("Secrets__EncryptionKey", exception.Message);
+        Assert.Contains("JWT 密钥", exception.Message);
     }
 
     [Fact]
diff --git a/backend/MiaoJiZhang.Api/Services/LlmSecretProtector.cs b/backend/MiaoJiZhang.Api/Services/LlmSecretProtector.cs
index 17c22e0..f189aa8 100644
--- a/backend/MiaoJiZhang.Api/Services/LlmSecretProtector.cs
+++ b/backend/MiaoJiZhang.Api/Services/LlmSecretProtector.cs
@@ -65,13 +65,11 @@ public sealed class LlmSecretProtector(IConfiguration configuration)
 
     private byte[] ReadEncryptionKey()
     {
-        var raw = configuration["Secrets:EncryptionKey"];
-        byte[]? key = null;
-        try { key = string.IsNullOrWhiteSpace(raw) ? null : Convert.FromBase64String(raw); }
-        catch (FormatException) { }
-        if (key?.Length != 32)
-            throw new InvalidOperationException(
-                "请通过 Secrets__EncryptionKey 配置 base64 编码的 32 字节密钥后再保存 API Key");
-        return key;
+        var jwtSecret = configuration["Jwt:Secret"];
+        if (string.IsNullOrWhiteSpace(jwtSecret) || jwtSecret.Length < 32)
+            throw new InvalidOperationException("服务端 JWT 密钥配置无效，无法保护 API Key");
+        return HMACSHA256.HashData(
+            Encoding.UTF8.GetBytes(jwtSecret),
+            Encoding.UTF8.GetBytes("jizhi:llm-api-key-encryption:v1"));
     }
 }
diff --git a/docs/DEVELOPER.md b/docs/DEVELOPER.md
index 297889d..0aff3b0 100644
--- a/docs/DEVELOPER.md
+++ b/docs/DEVELOPER.md
@@ -45,7 +45,6 @@
 cd backend
 export Admin__BootstrapUsername='admin'
 export Admin__BootstrapPassword='replace-with-a-password-longer-than-5-characters'
-export Secrets__EncryptionKey='base64-encoded-32-byte-key'
 dotnet build
 # 重启
 powershell -Command "Get-Process dotnet | Stop-Process -Force"
@@ -57,16 +56,9 @@ dotnet run --project MiaoJiZhang.Api
 引导变量。正式环境必须使用 HTTPS 并保持 `Admin__CookieSecure=true`。本地纯 HTTP 调试时才可
 临时设置 `Admin__CookieSecure=false`。
 
-后台“AI 配置 → 模型服务”可以保存和替换 LLM API Key。实际 API Key 使用 AES-GCM
-加密后写入配置表，服务端只需通过 `Secrets__EncryptionKey` 提供一个固定的 32 字节
-加密主密钥；页面和接口只显示 API Key 尾号。可使用 PowerShell 生成：
-
-```powershell
-[Convert]::ToBase64String([Security.Cryptography.RandomNumberGenerator]::GetBytes(32))
-```
-
-请将该值保存到部署平台的密钥管理中，不要提交到仓库。更换或丢失主密钥会导致后台已保存的
-LLM API Key 无法解密。旧的 `LLM_API_KEY` 仍作为回退配置；后台保存的密钥优先。
+后台“AI 配置 → 模型服务”可以直接保存和替换 LLM API Key。实际 API Key 使用 AES-GCM
+加密后写入配置表，加密密钥由服务端从必填的 `Jwt__Secret` 自动派生，无需增加部署变量；
+页面和接口只显示 API Key 尾号。旧的 `LLM_API_KEY` 仍作为回退配置，后台保存的密钥优先。
 
 ### 2. Admin Web
 ```powershell