diff --git a/frontend/src/components/FileExplorer.tsx b/frontend/src/components/FileExplorer.tsx
index 7ae5e84..6b372a0 100644
--- a/frontend/src/components/FileExplorer.tsx
+++ b/frontend/src/components/FileExplorer.tsx
@@ -105,8 +105,9 @@ interface UploadBatch {
   uploadedBytes: number;
   totalFiles: number;
   filesUploaded: number;
-  status: 'uploading' | 'complete' | 'error';
+  status: 'uploading' | 'complete' | 'error' | 'canceled';
   error?: string;
+  abortController?: AbortController;
 }
 
 interface Toast {
@@ -908,8 +909,11 @@ export default function FileExplorer({ onLogout }: FileExplorerProps) {
       uploadedBytes: 0,
       totalFiles,
       filesUploaded: 0,
-      status: 'uploading'
-    }]);
+      status: 'uploading' as const,
+      abortController: new AbortController()
+    };
+
+    setUploads(prev => [...prev, newBatch]);
 
     const MAX_CONCURRENT = 4;
     let currentIndex = 0;
@@ -934,8 +938,10 @@ export default function FileExplorer({ onLogout }: FileExplorerProps) {
         const uploadPath = path ? (destPath === '.' ? path : `${destPath}/${path}`) : destPath;
         
         try {
+          if (newBatch.abortController.signal.aborted) throw new Error('Upload canceled');
           await api.upload(file, uploadPath, {
             overwrite,
+            signal: newBatch.abortController.signal,
             onProgress: (percent) => {
               fileProgressMap.set(file.name + path, (percent / 100) * file.size);
               updateProgress();
@@ -945,7 +951,12 @@ export default function FileExplorer({ onLogout }: FileExplorerProps) {
           fileProgressMap.set(file.name + path, file.size);
           updateProgress();
         } catch (err: any) {
-          setUploads(prev => prev.map(b => b.id === batchId ? { ...b, status: 'error', error: err.message || 'Upload failed' } : b));
+          setUploads(prev => prev.map(b => b.id === batchId ? { 
+            ...b, 
+            status: err.message === 'Upload canceled' ? 'canceled' : 'error', 
+            error: err.message || 'Upload failed' 
+          } : b));
+          if (err.message === 'Upload canceled') return;
         }
       }
     };
@@ -2093,7 +2104,7 @@ export default function FileExplorer({ onLogout }: FileExplorerProps) {
                 </span>
               </div>
               <button
-                onClick={() => setUploads(prev => prev.filter(u => u.status === 'uploading'))}
+                onClick={() => setUploads(prev => prev.filter(u => u.status !== 'uploading' && u.status !== 'error' && u.status !== 'canceled'))}
                 className="p-1 rounded hover:bg-white/10"
               >
                 <X className="w-4 h-4" style={{ color: 'var(--color-text-tertiary)' }} />
@@ -2104,17 +2115,28 @@ export default function FileExplorer({ onLogout }: FileExplorerProps) {
                 const percentage = batch.totalBytes > 0 ? (batch.uploadedBytes / batch.totalBytes) * 100 : 0;
                 return (
                   <div key={batch.id} className="p-3 rounded-xl" style={{ backgroundColor: 'var(--color-bg-elevated)' }}>
-                    <div className="flex items-center justify-between mb-1">
+                    <div className="flex items-center justify-between mb-2">
                       <span
-                        className="text-xs font-medium truncate max-w-[200px]"
+                        className="text-xs font-medium truncate max-w-[180px]"
                         style={{ color: 'var(--color-text-primary)' }}
                         title={batch.name}
                       >
                         {batch.name}
                       </span>
-                      <span className="text-xs" style={{ color: 'var(--color-text-tertiary)' }}>
-                        {batch.status === 'complete' ? '✓' : batch.status === 'error' ? '✗' : `${Math.round(percentage)}%`}
-                      </span>
+                      <div className="flex items-center gap-3">
+                        <span className="text-xs font-semibold" style={{ color: 'var(--color-text-secondary)' }}>
+                          {batch.status === 'canceled' ? 'Canceled' : `${Math.round(percentage)}%`}
+                        </span>
+                        {batch.status === 'uploading' && (
+                          <button
+                            onClick={() => batch.abortController?.abort()}
+                            className="p-1 rounded-full hover:bg-white/10 transition-colors"
+                            title="Cancel upload"
+                          >
+                            <X className="w-3 h-3 text-red-400 hover:text-red-300" />
+                          </button>
+                        )}
+                      </div>
                     </div>
                     {batch.totalFiles > 1 && (
                       <div className="text-[10px] mb-2" style={{ color: 'var(--color-text-secondary)' }}>
diff --git a/frontend/src/lib/api.ts b/frontend/src/lib/api.ts
index 05b53be..91c72a7 100644
--- a/frontend/src/lib/api.ts
+++ b/frontend/src/lib/api.ts
@@ -95,6 +95,7 @@ class ApiClient {
   }
 
   private async refreshAccessToken(): Promise<boolean> {
+    if (!this.refreshToken) return false;
     try {
       const response = await fetch(`${API_BASE}/api/auth/refresh`, {
         method: 'POST',
@@ -105,17 +106,35 @@ class ApiClient {
 
       if (response.ok) {
         const data = await response.json();
-        this.accessToken = data.access_token;
-        localStorage.setItem('access_token', data.access_token);
+        this.setTokens(data.access_token, data.refresh_token);
         return true;
       }
-    } catch {
+      
       // Refresh failed
+      this.clearTokens();
+      return false;
+    } catch (e) {
+      this.clearTokens();
+      return false;
     }
+  }
 
-    this.clearTokens();
-    if (typeof window !== 'undefined') window.dispatchEvent(new Event('auth_error'));
-    return false;
+  async ensureTokenFresh(): Promise<boolean> {
+    if (!this.accessToken) return false;
+    
+    try {
+      const parts = this.accessToken.split('.');
+      if (parts.length !== 3) return false;
+      const payload = JSON.parse(atob(parts[1]));
+      const exp = payload.exp * 1000;
+      // If expiring within 60 seconds, refresh it
+      if (Date.now() > exp - 60000) {
+        return await this.refreshAccessToken();
+      }
+      return true;
+    } catch (e) {
+      return false;
+    }
   }
 
   // --- Setup ---
@@ -227,13 +246,17 @@ class ApiClient {
         endpoint: `${API_BASE}/api/tus/`,
         chunkSize: 5 * 1024 * 1024, // 5MB chunks bypass Next.js 10MB proxy limit
         retryDelays: [0, 3000, 5000, 10000, 20000],
-        headers: this.getStreamHeaders(),
         metadata: {
           filename: file.name,
           filetype: file.type,
           path: destPath,
           overwrite: options?.overwrite ? "true" : "false",
         },
+        onBeforeRequest: async (req) => {
+          await this.ensureTokenFresh();
+          const xhr = req.getUnderlyingObject();
+          xhr.setRequestHeader('Authorization', `Bearer ${this.accessToken}`);
+        },
         onError: function (error) {
           reject(error);
         },
@@ -245,6 +268,15 @@ class ApiClient {
           resolve();
         },
       });
+
+      if (options?.signal) {
+        options.signal.addEventListener('abort', () => {
+          upload.abort(true).then(() => {
+             reject(new Error('Upload canceled'));
+          }).catch(reject);
+        });
+      }
+
       upload.start();
     });
   }