diff --git a/src-tauri/src/app_config.rs b/src-tauri/src/app_config.rs
index c66adad..5eea813 100644
--- a/src-tauri/src/app_config.rs
+++ b/src-tauri/src/app_config.rs
@@ -89,7 +89,7 @@ impl Default for MultiAppConfig {
 }
 
 impl MultiAppConfig {
-    /// 从文件加载配置（处理v1到v2的迁移）
+    /// 从文件加载配置（仅支持 v2 结构）
     pub fn load() -> Result<Self, AppError> {
         let config_path = get_app_config_path();
 
@@ -102,45 +102,33 @@ impl MultiAppConfig {
         let content =
             std::fs::read_to_string(&config_path).map_err(|e| AppError::io(&config_path, e))?;
 
-        // 检查是否是旧版本格式（v1）
-        if let Ok(v1_config) = serde_json::from_str::<ProviderManager>(&content) {
-            log::info!("检测到v1配置，自动迁移到v2");
-
-            // 迁移到新格式
-            let mut apps = HashMap::new();
-            apps.insert("claude".to_string(), v1_config);
-            apps.insert("codex".to_string(), ProviderManager::default());
-
-            let config = Self {
-                version: 2,
-                apps,
-                mcp: McpRoot::default(),
-            };
-
-            // 迁移前备份旧版(v1)配置文件
-            let backup_dir = get_app_config_dir();
-            let ts = std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap_or_default()
-                .as_secs();
-            let backup_path = backup_dir.join(format!("config.v1.backup.{}.json", ts));
-
-            match copy_file(&config_path, &backup_path) {
-                Ok(()) => log::info!(
-                    "已备份旧版配置文件: {} -> {}",
-                    config_path.display(),
-                    backup_path.display()
-                ),
-                Err(e) => log::warn!("备份旧版配置文件失败: {}", e),
-            }
-
-            // 保存迁移后的配置
-            config.save()?;
-            return Ok(config);
+        // 先解析为 Value，以便严格判定是否为 v1 结构；
+        // 满足：顶层同时包含 providers(object) + current(string)，且不包含 version/apps/mcp 关键键，即视为 v1
+        let value: serde_json::Value =
+            serde_json::from_str(&content).map_err(|e| AppError::json(&config_path, e))?;
+        let is_v1 = value.as_object().map_or(false, |map| {
+            let has_providers = map
+                .get("providers")
+                .map(|v| v.is_object())
+                .unwrap_or(false);
+            let has_current = map
+                .get("current")
+                .map(|v| v.is_string())
+                .unwrap_or(false);
+            // v1 的充分必要条件：有 providers 和 current，且 apps 不存在（version/mcp 可能存在但不作为 v2 判据）
+            let has_apps = map.contains_key("apps");
+            has_providers && has_current && !has_apps
+        });
+        if is_v1 {
+            return Err(AppError::localized(
+                "config.unsupported_v1",
+                "检测到旧版 v1 配置格式。当前版本已不再支持运行时自动迁移。\n\n解决方案：\n1. 安装 v3.2.x 版本进行一次性自动迁移\n2. 或手动编辑 ~/.cc-switch/config.json，将顶层结构调整为：\n   {\"version\": 2, \"claude\": {...}, \"codex\": {...}, \"mcp\": {...}}\n\n",
+                "Detected legacy v1 config. Runtime auto-migration is no longer supported.\n\nSolutions:\n1. Install v3.2.x for one-time auto-migration\n2. Or manually edit ~/.cc-switch/config.json to adjust the top-level structure:\n   {\"version\": 2, \"claude\": {...}, \"codex\": {...}, \"mcp\": {...}}\n\n",
+            ));
         }
 
-        // 尝试读取v2格式
-        serde_json::from_str::<Self>(&content).map_err(|e| AppError::json(&config_path, e))
+        // 解析 v2 结构
+        serde_json::from_value::<Self>(value).map_err(|e| AppError::json(&config_path, e))
     }
 
     /// 保存配置到文件
diff --git a/src-tauri/tests/app_config_load.rs b/src-tauri/tests/app_config_load.rs
new file mode 100644
index 0000000..648b645
--- /dev/null
+++ b/src-tauri/tests/app_config_load.rs
@@ -0,0 +1,105 @@
+use std::fs;
+use std::path::PathBuf;
+
+use cc_switch_lib::{AppError, MultiAppConfig};
+
+mod support;
+use support::{ensure_test_home, reset_test_fs, test_mutex};
+
+fn cfg_path() -> PathBuf {
+    let home = std::env::var("HOME").expect("HOME should be set by ensure_test_home");
+    PathBuf::from(home).join(".cc-switch").join("config.json")
+}
+
+#[test]
+fn load_v1_config_returns_error_and_does_not_write() {
+    let _guard = test_mutex().lock().expect("acquire test mutex");
+    reset_test_fs();
+    let home = ensure_test_home();
+    let path = cfg_path();
+    fs::create_dir_all(path.parent().unwrap()).expect("create cfg dir");
+
+    // 最小 v1 形状：providers + current，且不含 version/apps/mcp
+    let v1_json = r#"{"providers":{},"current":""}"#;
+    fs::write(&path, v1_json).expect("seed v1 json");
+    let before = fs::read_to_string(&path).expect("read before");
+
+    let err = MultiAppConfig::load().expect_err("v1 should not be auto-migrated");
+    match err {
+        AppError::Localized { key, .. } => assert_eq!(key, "config.unsupported_v1"),
+        other => panic!("expected Localized v1 error, got {other:?}"),
+    }
+
+    // 文件不应有任何变化，且不应生成 .bak
+    let after = fs::read_to_string(&path).expect("read after");
+    assert_eq!(before, after, "config.json should not be modified");
+    let bak = home.join(".cc-switch").join("config.json.bak");
+    assert!(!bak.exists(), ".bak should not be created on load error");
+}
+
+#[test]
+fn load_v1_with_extra_version_still_treated_as_v1() {
+    let _guard = test_mutex().lock().expect("acquire test mutex");
+    reset_test_fs();
+    let home = ensure_test_home();
+    let path = cfg_path();
+    std::fs::create_dir_all(path.parent().unwrap()).expect("create cfg dir");
+
+    // 畸形：包含 providers + current + version，但没有 apps，应按 v1 处理
+    let v1_like = r#"{"providers":{},"current":"","version":2}"#;
+    std::fs::write(&path, v1_like).expect("seed v1-like json");
+    let before = std::fs::read_to_string(&path).expect("read before");
+
+    let err = MultiAppConfig::load().expect_err("v1-like should not be parsed as v2");
+    match err {
+        AppError::Localized { key, .. } => assert_eq!(key, "config.unsupported_v1"),
+        other => panic!("expected Localized v1 error, got {other:?}"),
+    }
+
+    let after = std::fs::read_to_string(&path).expect("read after");
+    assert_eq!(before, after, "config.json should not be modified");
+    let bak = home.join(".cc-switch").join("config.json.bak");
+    assert!(!bak.exists(), ".bak should not be created on v1-like error");
+}
+
+#[test]
+fn load_invalid_json_returns_parse_error_and_does_not_write() {
+    let _guard = test_mutex().lock().expect("acquire test mutex");
+    reset_test_fs();
+    let home = ensure_test_home();
+    let path = cfg_path();
+    fs::create_dir_all(path.parent().unwrap()).expect("create cfg dir");
+
+    fs::write(&path, "{not json").expect("seed invalid json");
+    let before = fs::read_to_string(&path).expect("read before");
+
+    let err = MultiAppConfig::load().expect_err("invalid json should error");
+    match err {
+        AppError::Json { .. } => {}
+        other => panic!("expected Json error, got {other:?}"),
+    }
+
+    let after = fs::read_to_string(&path).expect("read after");
+    assert_eq!(before, after, "config.json should remain unchanged");
+    let bak = home.join(".cc-switch").join("config.json.bak");
+    assert!(!bak.exists(), ".bak should not be created on parse error");
+}
+
+#[test]
+fn load_valid_v2_config_succeeds() {
+    let _guard = test_mutex().lock().expect("acquire test mutex");
+    reset_test_fs();
+    let _home = ensure_test_home();
+    let path = cfg_path();
+    fs::create_dir_all(path.parent().unwrap()).expect("create cfg dir");
+
+    // 使用默认结构序列化为 v2
+    let default_cfg = MultiAppConfig::default();
+    let json = serde_json::to_string_pretty(&default_cfg).expect("serialize default cfg");
+    fs::write(&path, json).expect("write v2 json");
+
+    let loaded = MultiAppConfig::load().expect("v2 should load successfully");
+    assert_eq!(loaded.version, 2);
+    assert!(loaded.get_manager(&cc_switch_lib::AppType::Claude).is_some());
+    assert!(loaded.get_manager(&cc_switch_lib::AppType::Codex).is_some());
+}