fix(download): skip blob sidecar download when Fulu fork is active

The logic now checks if the "fulu" fork is active for the current epoch. If Fulu is active, blob sidecars are no longer included in blocks, so the download is skipped to prevent unnecessary operations and potential errors.

Author: samcm

pkg/beacon/download.go

@@ -352,9 +352,15 @@ func (d *Default) fetchBundle(ctx context.Context, root phase0.Root, upstream *N
 	denebFork, err := sp.ForkEpochs.GetByName("deneb")
 	if err == nil && denebFork != nil {
 		if denebFork.Active(epoch) {
-			// Download and store blob sidecars
-			if err := d.downloadAndStoreBlobSidecars(ctx, slot, upstream); err != nil {
-				return nil, fmt.Errorf("failed to download and store blob sidecars: %w", err)
+			// Check if Fulu is active - if so, don't fetch blobs as they're no longer in blocks
+			fuluFork, fuluErr := sp.ForkEpochs.GetByName("fulu")
+			if fuluErr == nil && fuluFork != nil && fuluFork.Active(epoch) {
+				d.log.WithField("epoch", epoch).Debug("Skipping blob sidecar download - Fulu fork active")
+			} else {
+				// Download and store blob sidecars
+				if err := d.downloadAndStoreBlobSidecars(ctx, slot, upstream); err != nil {
+					return nil, fmt.Errorf("failed to download and store blob sidecars: %w", err)
+				}
 			}
 		}
 	}