diff --git a/docs/agents/config-profile-change.md b/docs/agents/config-profile-change.md
index fa4ec93..e382c11 100644
--- a/docs/agents/config-profile-change.md
+++ b/docs/agents/config-profile-change.md
@@ -44,6 +44,7 @@
 - `config list` 标识所有 Profile 与当前激活项。
 - `config show`、`auth status` 只输出本次最终选择的 `config` 和 `config_file`，不重复携带激活状态。
 - `config ui` 从持久化元数据读取激活项，提供显式激活操作，并在删除激活项后刷新为 `default`。
+- `config ui` 保存时只替换 UI 管理的字段；Profile 中未展示但仍属于 `ConfigFile` 的合法字段必须保留，不能因打开并保存 UI 而丢失。
 - 同步 E2E topic routes、Skill setup 和自动生成 reference。
 
 ## 6. 最小测试矩阵
@@ -57,6 +58,7 @@
 - 登录、退出、`config set` 分别覆盖“当前激活项”和“显式不存在名称成功后创建”。
 - Console token 自动刷新不从其他 Profile 借用 AK/SK，也不把新 token 写入其他 Profile。
 - `config list/show/use/ui`、`auth status` 和依赖默认模型的消费命令覆盖对应 E2E。
+- `config ui` 覆盖保存时保留未管理字段，并继续允许空值清除 UI 管理字段。
 
 ## 7. 完成检查
 
diff --git a/packages/commands/src/commands/config/ui.ts b/packages/commands/src/commands/config/ui.ts
index 4d206d2..2c10c68 100644
--- a/packages/commands/src/commands/config/ui.ts
+++ b/packages/commands/src/commands/config/ui.ts
@@ -7,6 +7,7 @@ import {
   BailianError,
   ExitCode,
   normalizeConfigName,
+  readConfigFile,
   writeConfigFile,
   deleteConfigProfile,
   type ConfigStore,
@@ -72,6 +73,19 @@ function buildProfilePatch(data: Record<string, unknown>): Record<string, string
   return cleaned;
 }
 
+/** Preserve valid Config fields that the UI does not expose or manage. */
+function mergeUnmanagedProfileFields(
+  existing: Record<string, unknown>,
+  managedPatch: Record<string, string | number>,
+): Record<string, unknown> {
+  const managedKeys = new Set<string>(VALID_KEYS);
+  const merged: Record<string, unknown> = {};
+  for (const [key, value] of Object.entries(existing)) {
+    if (!managedKeys.has(key)) merged[key] = value;
+  }
+  return { ...merged, ...managedPatch };
+}
+
 /**
  * Build the config-UI http server. Exported for tests. The handler enforces:
  * - Host header must be a loopback name (anti DNS-rebinding).
@@ -158,8 +172,10 @@ export function createConfigUiServer(token: string, configStore: ConfigStore): h
           sendJson(res, 400, { error: errMessage(err) });
           return;
         }
-        await writeConfigFile(cleaned, normalized);
-        sendJson(res, 200, { saved: cleaned });
+        const existing = readConfigFile(normalized) as Record<string, unknown>;
+        const saved = mergeUnmanagedProfileFields(existing, cleaned);
+        await writeConfigFile(saved, normalized);
+        sendJson(res, 200, { saved });
         return;
       }
 
diff --git a/packages/commands/tests/config-ui.test.ts b/packages/commands/tests/config-ui.test.ts
index 28bcf6e..5a91559 100644
--- a/packages/commands/tests/config-ui.test.ts
+++ b/packages/commands/tests/config-ui.test.ts
@@ -128,6 +128,47 @@ test("POST /api/profile 写命名 profile（timeout 强制为 number），空串
   });
 });
 
+test("POST /api/profile 保留 UI 未管理字段，同时替换 UI 管理字段", async () => {
+  await withServer(async (port) => {
+    await writeConfigFile(
+      {
+        api_key: "sk-old",
+        output: "json",
+        console_site: "international",
+        console_region: "ap-southeast-1",
+        console_switch_agent: 42,
+        telemetry: false,
+      },
+      "stage",
+    );
+
+    const save = await httpJson(port, "POST", `/api/profile?token=${TOKEN}`, {
+      body: { name: "stage", data: { api_key: "sk-new" } },
+    });
+    expect(save.status).toBe(200);
+
+    const profile = readConfigFile("stage");
+    expect(profile).toMatchObject({
+      api_key: "sk-new",
+      console_site: "international",
+      console_region: "ap-southeast-1",
+      console_switch_agent: 42,
+      telemetry: false,
+    });
+    expect(profile.output).toBeUndefined();
+
+    const rawConfig = JSON.parse(readFileSync(getConfigPath(), "utf8"));
+    expect(rawConfig.stage).toMatchObject({
+      api_key: "sk-new",
+      console_site: "international",
+      console_region: "ap-southeast-1",
+      console_switch_agent: 42,
+      telemetry: false,
+    });
+    expect(rawConfig.stage.output).toBeUndefined();
+  });
+});
+
 test("New profile 立即保存空 Profile，其他配置读取可以看到", async () => {
   await withServer(async (port) => {
     const create = await httpJson(port, "POST", `/api/profile?token=${TOKEN}`, {