Let agents idle for updates required by creation cancellation

src/lib/server/hosts/index.ts

@@ -319,6 +319,13 @@ export function queueHostOperation(hostId: string, kind: string, payload: Record
 export function pendingHostOperations(hostId: string): HostOperation[] {
     const host = requireHost(hostId);
     if (host.mode === 'disabled' || !host.connected) return [];
+    // Older agents hold activity.lock across the entire delivered batch, including
+    // observations. Filtering only the unsupported cleanup can keep the updater
+    // busy indefinitely. Drain the old batch by withholding ALL further work;
+    // heartbeats and receipts still flow, and the new capability releases this hold.
+    // This must live in the controller so the fix also works before an agent update.
+    if (!host.inventory.capabilities?.includes('instance.cancel-create') && database().prepare(`SELECT 1 FROM ec_host_operations
+        WHERE host_id=? AND kind='instance.cancel-create' AND state IN ('pending','accepted','running','unknown') LIMIT 1`).get(hostId)) return [];
     // Accepted/running/unknown commands keep the same immutable ID. The agent
     // consults its durable journal before acknowledging or executing a replay.
     return database().transaction(() => {