diff --git a/src-tauri/src/mcp/codex.rs b/src-tauri/src/mcp/codex.rs
index 7ab7eef8f..73100beda 100644
--- a/src-tauri/src/mcp/codex.rs
+++ b/src-tauri/src/mcp/codex.rs
@@ -361,14 +361,11 @@ pub fn sync_single_server_to_codex(
     let mut doc = if config_path.exists() {
         let content =
             std::fs::read_to_string(&config_path).map_err(|e| AppError::io(&config_path, e))?;
-        // 尝试解析现有配置，如果失败则创建新文档（容错处理）
-        match content.parse::<toml_edit::DocumentMut>() {
-            Ok(doc) => doc,
-            Err(e) => {
-                log::warn!("解析 Codex config.toml 失败: {e}，将创建新配置");
-                toml_edit::DocumentMut::new()
-            }
-        }
+        // 解析失败必须报错而不是用空文档顶替：写回空文档会把用户
+        // config.toml 里的其它段落（model/model_providers/注释等）整体清空
+        content
+            .parse::<toml_edit::DocumentMut>()
+            .map_err(|e| AppError::McpValidation(format!("解析 config.toml 失败: {e}")))?
     } else {
         toml_edit::DocumentMut::new()
     };
diff --git a/src-tauri/tests/import_export_sync.rs b/src-tauri/tests/import_export_sync.rs
index e1e81d24e..f6df65876 100644
--- a/src-tauri/tests/import_export_sync.rs
+++ b/src-tauri/tests/import_export_sync.rs
@@ -497,6 +497,42 @@ fn sync_enabled_to_codex_returns_error_on_invalid_toml() {
     }
 }
 
+#[test]
+fn sync_single_server_to_codex_fails_closed_on_invalid_toml() {
+    let _guard = test_mutex().lock().expect("acquire test mutex");
+    reset_test_fs();
+    let path = cc_switch_lib::get_codex_config_path();
+    if let Some(parent) = path.parent() {
+        fs::create_dir_all(parent).expect("create codex dir");
+    }
+    // 含用户内容 + 语法错误的 config.toml：同步必须报错且不得覆盖文件
+    let broken = "model = \"gpt-5.5\"\ninvalid = [\n";
+    fs::write(&path, broken).expect("write invalid config");
+
+    let config = MultiAppConfig::default();
+    let err = cc_switch_lib::sync_single_server_to_codex(
+        &config,
+        "srv",
+        &json!({ "type": "stdio", "command": "echo" }),
+    )
+    .expect_err("sync should fail instead of wiping the file");
+    match err {
+        cc_switch_lib::AppError::McpValidation(msg) => {
+            assert!(
+                msg.contains("config.toml"),
+                "error message should mention config.toml"
+            );
+        }
+        other => panic!("unexpected error: {other:?}"),
+    }
+
+    let text = fs::read_to_string(&path).expect("read config.toml");
+    assert_eq!(
+        text, broken,
+        "invalid config.toml must be left untouched on sync failure"
+    );
+}
+
 #[test]
 fn sync_codex_provider_missing_auth_returns_error() {
     let _guard = test_mutex().lock().expect("acquire test mutex");