diff --git a/apps/server/src/services/threads/timeline.ts b/apps/server/src/services/threads/timeline.ts
index 430d64660..eb8b0d70f 100644
--- a/apps/server/src/services/threads/timeline.ts
+++ b/apps/server/src/services/threads/timeline.ts
@@ -631,8 +631,30 @@ function filterExactEventRowsForRequestedTurn(
 ): FilterExactEventRowsForRequestedTurnResult {
   const rows: StoredEventRow[] = [];
   let removedRows = false;
+  // PROTOTYPE (#1714): item ids the requested turn started. A later turn's
+  // item/* row for one of these ids is the same lifecycle the projection
+  // merges by bare call id (upsertRunningExecCall keeps the first scope), so
+  // keep it. Another item/started for the id (ACP id reuse, #1398) ends the
+  // ownership.
+  const ownedItemIds = new Set<string>();
   for (const row of args.exactEventRows) {
-    if (row.scopeKind === "turn" && row.turnId !== args.turnId) {
+    if (row.scopeKind === "turn" && row.turnId === args.turnId) {
+      if (row.type === "item/started" && row.itemId !== null) {
+        ownedItemIds.add(row.itemId);
+      }
+    } else if (row.scopeKind === "turn" && row.turnId !== args.turnId) {
+      if (row.type === "item/started" && row.itemId !== null) {
+        ownedItemIds.delete(row.itemId);
+      }
+      if (
+        row.itemId !== null &&
+        row.itemKind !== "backgroundTask" &&
+        row.type.startsWith("item/") &&
+        ownedItemIds.has(row.itemId)
+      ) {
+        rows.push(row);
+        continue;
+      }
       removedRows = true;
       continue;
     }