feat: implement background cleanup for uploaded files and enhance attachment removal logic

Author: alfarahn

src/Dashboard/AI/Tools/UploadedFileTools.cs

@@ -35,11 +35,22 @@ public sealed record UploadEntry(
     private const int TimeoutSeconds = 30;
     private const long MaxBytes = 100L * 1024 * 1024; // 100 MB
 
+    // .xls intentionally omitted — pandas needs the (uninstalled) xlrd package for legacy xls.
     private static readonly HashSet<string> SupportedExtensions = new(StringComparer.OrdinalIgnoreCase)
     {
-        ".csv", ".tsv", ".json", ".txt", ".log", ".md", ".xlsx", ".xls", ".pdf", ".parquet"
+        ".csv", ".tsv", ".json", ".txt", ".log", ".md", ".xlsx", ".pdf", ".parquet"
     };
 
+    static UploadedFileTools()
+    {
+        // Background TTL sweep — without this, expired temp files only get evicted
+        // when a new upload happens. Fires every 5 min, ignores its own exceptions.
+        _cleanupTimer = new Timer(_ => { try { Cleanup(); } catch { } },
+            null, TimeSpan.FromMinutes(5), TimeSpan.FromMinutes(5));
+    }
+
+    private static readonly Timer _cleanupTimer;
+
     private readonly UserTokens _tokens; // not used today, kept for symmetry with other per-user tools
 
     public UploadedFileTools(UserTokens tokens) => _tokens = tokens;
@@ -219,10 +230,11 @@ public static IReadOnlyList<UploadEntry> ListForUser(long userId)
 
     public static bool RemoveForUser(long userId, string fileId)
     {
-        // Soft remove: keep the entry + temp file alive so prior tool-call results in the
-        // chat history remain valid for follow-ups. The 30-min TTL (Cleanup) and
-        // /api/chat/reset (ClearForUser) handle actual disposal.
-        return UserFiles.TryGetValue(userId, out var bucket) && bucket.ContainsKey(fileId);
+        // Remove from the user's listing so the LLM context block no longer shows it,
+        // but keep the temp file on disk so any prior tool-call results in the chat
+        // history remain valid for replay. Actual file disposal happens on
+        // /api/chat/reset (ClearForUser) or via the 30-min TTL sweep.
+        return UserFiles.TryGetValue(userId, out var bucket) && bucket.TryRemove(fileId, out _);
     }
 
     public static void ClearForUser(long userId)

src/Dashboard/client/src/components/ChatView.vue

@@ -1648,10 +1648,17 @@ async function uploadFiles(files) {
 }
 
 function removeAttachment(att) {
-  // Soft remove on the client only — keep the file alive server-side so
-  // prior tool-call results in chat history stay valid for follow-ups.
-  // Actual disposal happens on /api/chat/reset or 30-min TTL.
+  // Drop from the client list immediately, and tell the server to remove it
+  // from the per-user listing so the next chat turn no longer surfaces this
+  // fileId in the [UPLOADED FILES…] context block. The temp file is kept
+  // on disk so prior tool-call results in chat history remain valid; full
+  // disposal happens on /api/chat/reset or via the 30-min TTL.
   attachments.value = attachments.value.filter((a) => a !== att);
+  if (att.fileId) {
+    fetch(`/api/uploads/${encodeURIComponent(att.fileId)}`, {
+      method: "DELETE",
+    }).catch(() => {});
+  }
 }
 
 function formatBytes(n) {