fix(#937): skip scheduled delivery if target already has pending scheduled message

hive-c0re/src/broker.rs

@@ -263,6 +263,21 @@ impl Broker {
         Ok(u64::try_from(n.max(0)).unwrap_or(0))
     }
 
+    /// Returns true when the recipient already has at least one
+    /// undelivered message from `sender` in the broker. Used by the
+    /// scheduler to avoid piling up repeated prompts when an agent is
+    /// slow or was briefly offline.
+    pub fn has_pending_from(&self, recipient: &str, sender: &str) -> Result<bool> {
+        let conn = self.conn.lock().unwrap();
+        let n: i64 = conn.query_row(
+            "SELECT COUNT(*) FROM messages
+              WHERE recipient = ?1 AND sender = ?2 AND delivered_at IS NULL",
+            params![recipient, sender],
+            |row| row.get(0),
+        )?;
+        Ok(n > 0)
+    }
+
     /// Long-poll variant of `recv_batch`: returns immediately if any
     /// row is pending (popping up to `max`); otherwise waits up to
     /// `timeout` for the broker to emit a `Sent { to: recipient }`

hive-c0re/src/scheduled_prompts_worker.rs

@@ -96,6 +96,31 @@ fn fire_schedule(coord: &Arc<Coordinator>, schedule: &Schedule, now: i64) {
             notify_operator_missing_target(coord, schedule, target);
             continue;
         }
+        // Skip delivery if there is already an unread message from
+        // "scheduled" waiting in this target's inbox. Prevents prompt
+        // accumulation when the agent is slow to drain its queue or
+        // was briefly offline: at most one scheduled message is ever
+        // pending per target at a time.
+        match coord.broker.has_pending_from(target, "scheduled") {
+            Ok(true) => {
+                tracing::debug!(
+                    schedule = schedule.id,
+                    %target,
+                    "scheduled_prompts: skipping — target already has pending scheduled message"
+                );
+                let _ = coord.scheduled_prompts.record_target_result(
+                    schedule.id,
+                    target,
+                    now,
+                    "skipped: already pending",
+                );
+                continue;
+            }
+            Err(e) => {
+                tracing::warn!(schedule = schedule.id, %target, error = ?e, "has_pending_from failed");
+            }
+            Ok(false) => {}
+        }
         let msg = Message {
             from: "scheduled".to_owned(),
             to: target.clone(),