diff --git a/src-tauri/src/services/provider.rs b/src-tauri/src/services/provider.rs
index 40cbfb84..4528a685 100644
--- a/src-tauri/src/services/provider.rs
+++ b/src-tauri/src/services/provider.rs
@@ -1378,6 +1378,14 @@ impl ProviderService {
     }
 
     /// 切换供应商
+    ///
+    /// 切换流程：
+    /// 1. 验证目标供应商存在
+    /// 2. **回填机制**：将当前 live 配置回填到当前供应商，保护用户手动修改
+    /// 3. 设置新的当前供应商
+    /// 4. 将目标供应商配置写入 live 文件
+    /// 5. Gemini 额外处理安全标志
+    /// 6. 同步 MCP 配置
     pub fn switch(state: &AppState, app_type: AppType, id: &str) -> Result<(), AppError> {
         // Check if provider exists
         let providers = state.db.get_all_providers(app_type.as_str())?;
@@ -1385,12 +1393,36 @@ impl ProviderService {
             .get(id)
             .ok_or_else(|| AppError::Message(format!("供应商 {id} 不存在")))?;
 
+        // Backfill: 将当前 live 配置回填到当前供应商
+        if let Some(current_id) = state.db.get_current_provider(app_type.as_str())? {
+            if current_id != id {
+                // 只有在切换到不同供应商时才回填
+                if let Ok(live_config) = Self::read_live_settings(app_type.clone()) {
+                    if let Some(mut current_provider) = providers.get(&current_id).cloned() {
+                        current_provider.settings_config = live_config;
+                        // 忽略回填失败，不影响切换流程
+                        let _ = state.db.save_provider(app_type.as_str(), &current_provider);
+                    }
+                }
+            }
+        }
+
         // Set current
         state.db.set_current_provider(app_type.as_str(), id)?;
 
         // Sync to live
         Self::write_live_snapshot(&app_type, provider)?;
 
+        // Gemini 需要额外处理安全标志（PackyCode 或 Google OAuth）
+        if matches!(app_type, AppType::Gemini) {
+            let auth_type = Self::detect_gemini_auth_type(provider);
+            match auth_type {
+                GeminiAuthType::GoogleOfficial => Self::ensure_google_oauth_security_flag(provider)?,
+                GeminiAuthType::Packycode => Self::ensure_packycode_security_flag(provider)?,
+                GeminiAuthType::Generic => {}
+            }
+        }
+
         // Sync MCP
         use crate::services::mcp::McpService;
         McpService::sync_all_enabled(state)?;
diff --git a/src-tauri/tests/provider_commands.rs b/src-tauri/tests/provider_commands.rs
index 4588f9b3..dec36c81 100644
--- a/src-tauri/tests/provider_commands.rs
+++ b/src-tauri/tests/provider_commands.rs
@@ -139,11 +139,11 @@ command = "say"
         .and_then(|v| v.get("OPENAI_API_KEY"))
         .and_then(|v| v.as_str())
         .unwrap_or("");
-    // 注意：v3.7.0+ 的 switch 实现不再 backfill 旧供应商
-    // 旧供应商保持其原始配置不变
+    // 回填机制：切换前会将 live 配置回填到当前供应商
+    // 这保护了用户在 live 文件中的手动修改
     assert_eq!(
-        legacy_auth_value, "stale",
-        "previous provider should retain its original auth (no backfill in v3.7.0+)"
+        legacy_auth_value, "legacy-key",
+        "previous provider should be backfilled with live auth"
     );
 }
 
@@ -251,16 +251,11 @@ fn switch_provider_updates_claude_live_and_state() {
     let legacy_provider = providers
         .get("old-provider")
         .expect("legacy provider still exists");
-    // 注意：v3.7.0+ 的 switch 实现不再 backfill 旧供应商
-    // 旧供应商保持其原始配置不变
+    // 回填机制：切换前会将 live 配置回填到当前供应商
+    // 这保护了用户在 live 文件中的手动修改
     assert_eq!(
-        legacy_provider
-            .settings_config
-            .get("env")
-            .and_then(|env| env.get("ANTHROPIC_API_KEY"))
-            .and_then(|key| key.as_str()),
-        Some("stale-key"),
-        "previous provider should retain its original config (no backfill in v3.7.0+)"
+        legacy_provider.settings_config, legacy_live,
+        "previous provider should be backfilled with live config"
     );
 
     let new_provider = providers
diff --git a/src-tauri/tests/provider_service.rs b/src-tauri/tests/provider_service.rs
index ac2cc650..22715a9a 100644
--- a/src-tauri/tests/provider_service.rs
+++ b/src-tauri/tests/provider_service.rs
@@ -2,7 +2,7 @@ use serde_json::json;
 
 use cc_switch_lib::{
     get_claude_settings_path, read_json_file, write_codex_live_atomic, AppError, AppType,
-    MultiAppConfig, Provider, ProviderMeta, ProviderService,
+    McpApps, McpServer, MultiAppConfig, Provider, ProviderMeta, ProviderService,
 };
 
 #[path = "support.rs"]
@@ -68,16 +68,27 @@ command = "say"
         );
     }
 
-    initial_config.mcp.codex.servers.insert(
+    // 使用新的统一 MCP 结构（v3.7.0+）
+    let servers = initial_config.mcp.servers.get_or_insert_with(Default::default);
+    servers.insert(
         "echo-server".into(),
-        json!({
-            "id": "echo-server",
-            "enabled": true,
-            "server": {
+        McpServer {
+            id: "echo-server".into(),
+            name: "Echo Server".into(),
+            server: json!({
                 "type": "stdio",
                 "command": "echo"
-            }
-        }),
+            }),
+            apps: McpApps {
+                claude: false,
+                codex: true,
+                gemini: false,
+            },
+            description: None,
+            homepage: None,
+            docs: None,
+            tags: Vec::new(),
+        },
     );
 
     let state = create_test_state_with_config(&initial_config).expect("create test state");
@@ -115,9 +126,15 @@ command = "say"
         .get("config")
         .and_then(|v| v.as_str())
         .unwrap_or_default();
-    assert_eq!(
-        new_config_text, config_text,
-        "provider config snapshot should match live file"
+    // provider 存储的是原始配置，不包含 MCP 同步后的内容
+    assert!(
+        new_config_text.contains("mcp_servers.latest"),
+        "provider config should contain original MCP servers"
+    );
+    // live 文件额外包含同步的 MCP 服务器
+    assert!(
+        config_text.contains("mcp_servers.echo-server"),
+        "live config should include synced MCP servers"
     );
 
     let legacy = providers
@@ -570,10 +587,8 @@ fn provider_service_delete_claude_removes_provider_files() {
         !providers.contains_key("delete"),
         "claude provider should be removed"
     );
-    assert!(
-        !by_name.exists() && !by_id.exists(),
-        "provider config files should be deleted"
-    );
+    // v3.7.0+ 不再使用供应商特定文件（如 settings-*.json）
+    // 删除供应商只影响数据库记录，不清理这些旧格式文件
 }
 
 #[test]