diff --git a/src/webui/templates/authors.html b/src/webui/templates/authors.html
index d7d7063..4ba4d10 100644
--- a/src/webui/templates/authors.html
+++ b/src/webui/templates/authors.html
@@ -112,7 +112,7 @@
 {% if network.clusters %}
 <div class="bg-slate-900 rounded-xl border border-slate-800 p-5 mb-6">
     <h2 class="text-sm font-semibold text-slate-300 mb-1">Collaboration Clusters</h2>
-    <p class="text-xs text-slate-500 mb-4">Connected groups of authors who co-author drafts. Click a cluster to highlight it in the graph.</p>
+    <p class="text-xs text-slate-500 mb-4">Clusters are formed by connected-component analysis of the co-authorship graph: authors who share 2+ drafts are linked, and all authors reachable through such links form a cluster. This reveals research teams and institutional collaboration patterns — a cluster of 20 authors from 3 organizations means those groups actively co-author across org boundaries. Click a cluster to highlight it in the graph above.</p>
     <div class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4" id="clusterGrid">
         {% for c in network.clusters[:12] %}
         <div class="cluster-card bg-slate-800/50 rounded-lg border border-slate-700/50 p-4 cursor-pointer" data-cluster-id="{{ c.id }}" onclick="highlightCluster({{ c.id }})">