diff --git a/internal/handler/targets.go b/internal/handler/targets.go
index 77a7f5b..6fac1fb 100644
--- a/internal/handler/targets.go
+++ b/internal/handler/targets.go
@@ -246,7 +246,10 @@ func (h *CorpusHandler) Upload(c *gin.Context) {
 		runID = &uid
 	}
 
-	blobKey := fmt.Sprintf("corpus/%s/%s/%s", target.RepoName, target.Name, header.Filename)
+	// Use a unique prefix to avoid filename collisions across runs.
+	var entryCount int64
+	h.DB.WithContext(ctx).Model(&models.CorpusEntry{}).Where("target_id = ?", targetID).Count(&entryCount)
+	blobKey := fmt.Sprintf("corpus/%s/%s/%d-%s", target.RepoName, target.Name, entryCount, header.Filename)
 
 	if err := h.Store.Put(ctx, blobKey, file, header.Size); err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": "storing blob: " + err.Error()})
@@ -362,7 +365,7 @@ func (h *CorpusHandler) DownloadAll(c *gin.Context) {
 		}
 
 		hdr := &tar.Header{
-			Name: filepath.Base(entry.BlobKey),
+			Name: fmt.Sprintf("%d-%s", entry.ID, filepath.Base(entry.BlobKey)),
 			Mode: 0o644,
 			Size: int64(len(data)),
 		}