fix: stabilize download source switching

- serialize app and core version checks to prevent state races
- keep the source selector responsive during background checks
- prevent stale fallback results from overriding recent selections
- style the custom source action and restore the compact selector width

src-tauri/src/app_update.rs

@@ -130,6 +130,7 @@ pub(crate) async fn check_app_update(
     state: tauri::State<'_, AppUpdateState>,
     gui_config_state: tauri::State<'_, GuiConfigState>,
 ) -> Result<AppUpdateInfo, String> {
+    let _detection_guard = VERSION_SOURCE_DETECTION_LOCK.lock().await;
     let config = gui_config_state.snapshot()?;
     let proxy_url = config.proxy_url.clone();
     let client = build_http_client_with_proxy(

src-tauri/src/core_runtime.rs

@@ -5,6 +5,7 @@ pub(crate) async fn check_latest_core(
     app: tauri::AppHandle,
     gui_config_state: tauri::State<'_, GuiConfigState>,
 ) -> Result<CoreLatest, String> {
+    let _detection_guard = VERSION_SOURCE_DETECTION_LOCK.lock().await;
     let platform = current_core_platform()?;
     let config = gui_config_state.snapshot()?;
     let proxy_url = config.proxy_url.clone();

src-tauri/src/main.rs

@@ -111,6 +111,7 @@ const CORE_INSTALL_PROGRESS_EVENT: &str = "core-install-progress";
 const CORE_STATUS_EVENT: &str = "core-status-changed";
 const CONFIG_FILES_CHANGED_EVENT: &str = "config-files-changed";
 const VERSION_DOWNLOAD_SOURCE_CHANGED_EVENT: &str = "version-download-source-changed";
+static VERSION_SOURCE_DETECTION_LOCK: tokio::sync::Mutex<()> = tokio::sync::Mutex::const_new(());
 #[cfg(target_os = "windows")]
 const WINDOWS_CLOSE_REQUEST_EVENT: &str = "windows-close-requested";
 const CORE_METADATA_FILE: &str = "cpa-gui-meta.json";

src/pages/VersionManagementPage.tsx

@@ -245,7 +245,9 @@ export function VersionManagementPage() {
       cachedLatestError = '';
       setLatest(null);
       showToast(t('kernel.versions.gitcodeSwitchSuccess'), 'success');
-      await Promise.allSettled([checkAppUpdate(), checkLatest(true)]);
+      setVersionSourceSaving(false);
+      await checkAppUpdate();
+      await checkLatest(true);
     } catch (error) {
       await loadVersionSourceSettings();
       setVersionSourceError(t('kernel.versions.gitcodeSaveFailed', { error: String(error) }));
@@ -269,7 +271,9 @@ export function VersionManagementPage() {
       cachedLatestError = '';
       setLatest(null);
       showToast(t('kernel.versions.customMirrorAdded'), 'success');
-      await Promise.allSettled([checkAppUpdate(), checkLatest(true)]);
+      setVersionSourceSaving(false);
+      await checkAppUpdate();
+      await checkLatest(true);
     } catch (error) {
       const message = t('kernel.versions.customMirrorAddFailed', { error: String(error) });
       setVersionSourceError(message);
@@ -289,8 +293,10 @@ export function VersionManagementPage() {
       });
       setVersionSource(settings);
       showToast(t('kernel.versions.customMirrorRemoved'), 'success');
+      setVersionSourceSaving(false);
       if (wasSelected) {
-        await Promise.allSettled([checkAppUpdate(), checkLatest(true)]);
+        await checkAppUpdate();
+        await checkLatest(true);
       }
     } catch (error) {
       const message = t('kernel.versions.customMirrorRemoveFailed', { error: String(error) });
@@ -618,7 +624,7 @@ export function VersionManagementPage() {
             </label>
             <button
               type="button"
-              className="version-source-add-button"
+              className="primary-button version-source-add-button"
               disabled={versionSourceSaving || appUpdateTask.running || installing}
               onClick={() => {
                 setVersionSourceError('');

src/styles.css

@@ -1079,14 +1079,14 @@ textarea:focus-visible {
 
 .version-source-control {
   display: grid;
-  grid-template-columns: minmax(0, 250px) auto;
+  grid-template-columns: minmax(0, 220px) auto;
   width: max-content;
   max-width: 100%;
   gap: 8px;
 }
 
 .version-source-control select {
-  width: 250px;
+  width: 220px;
   max-width: 100%;
   height: 42px;
   padding: 0 36px 0 12px;
@@ -1114,15 +1114,6 @@ textarea:focus-visible {
   justify-content: center;
   gap: 6px;
   padding: 0 12px;
-  border: 1px solid var(--theme-d5d2cb);
-  border-radius: 8px;
-  background: var(--theme-fffdf8);
-  color: var(--theme-4b4742);
-}
-
-.version-source-add-button:hover:not(:disabled) {
-  border-color: var(--theme-9b958c);
-  background: var(--theme-faf8f2);
 }
 
 .version-source-add-button:disabled {