diff --git a/src/server/services/session-discovery.ts b/src/server/services/session-discovery.ts
index 9264275..8189137 100644
--- a/src/server/services/session-discovery.ts
+++ b/src/server/services/session-discovery.ts
@@ -80,6 +80,7 @@ export async function discoverSessions(
             modified: entry.modified || "",
             messageCount: entry.messageCount || 0,
             path: resolved,
+            duration: computeDuration(entry.created, entry.modified),
           });
         }
       } catch {
@@ -102,3 +103,12 @@ export async function discoverSessions(
 
   return sessions;
 }
+
+function computeDuration(created?: string, modified?: string): number {
+  if (!created || !modified) return 0;
+  const createdMs = new Date(created).getTime();
+  const modifiedMs = new Date(modified).getTime();
+  if (isNaN(createdMs) || isNaN(modifiedMs)) return 0;
+  const diff = modifiedMs - createdMs;
+  return diff > 0 ? diff : 0;
+}
diff --git a/src/shared/types.ts b/src/shared/types.ts
index f27a92a..0d2814d 100644
--- a/src/shared/types.ts
+++ b/src/shared/types.ts
@@ -28,6 +28,7 @@ export interface SessionEntry {
   modified: string;
   messageCount: number;
   path: string;
+  duration?: number; // Duration in milliseconds from first to last message
 }
 
 export interface SessionListResponse {