diff --git a/quickwit/quickwit-ingest/src/ingest_v2/router.rs b/quickwit/quickwit-ingest/src/ingest_v2/router.rs
index 581b648ae71..d27c5ebfb77 100644
--- a/quickwit/quickwit-ingest/src/ingest_v2/router.rs
+++ b/quickwit/quickwit-ingest/src/ingest_v2/router.rs
@@ -672,12 +672,17 @@ mod tests {
 
         {
             let mut state_guard = router.state.lock().await;
-            state_guard.routing_table.apply_capacity_update(
-                "test-ingester-0".into(),
+            state_guard.routing_table.merge_from_shards(
                 IndexUid::for_test("test-index-0", 0),
                 "test-source".to_string(),
-                8,
-                1,
+                vec![Shard {
+                    index_uid: Some(IndexUid::for_test("test-index-0", 0)),
+                    source_id: "test-source".to_string(),
+                    shard_id: Some(ShardId::from(1u64)),
+                    shard_state: ShardState::Open as i32,
+                    leader_id: "test-ingester-0".to_string(),
+                    ..Default::default()
+                }],
             );
         }
 
diff --git a/quickwit/quickwit-ingest/src/ingest_v2/routing_table.rs b/quickwit/quickwit-ingest/src/ingest_v2/routing_table.rs
index f5475387287..529922d657a 100644
--- a/quickwit/quickwit-ingest/src/ingest_v2/routing_table.rs
+++ b/quickwit/quickwit-ingest/src/ingest_v2/routing_table.rs
@@ -41,6 +41,11 @@ pub(super) struct IngesterNode {
 #[derive(Debug, Default)]
 pub(super) struct RoutingEntry {
     pub nodes: HashMap<NodeId, IngesterNode>,
+    /// Whether this entry has been seeded from a control plane response. During a rolling
+    /// deployment, Chitchat broadcasts from already-upgraded nodes may populate the table
+    /// before the router ever asks the CP, causing it to miss old-version nodes. This flag
+    /// ensures the router asks the CP at least once per (index, source) pair.
+    seeded_from_cp: bool,
 }
 
 /// Given a slice of candidates, picks the better of two random choices.
@@ -180,6 +185,10 @@ impl RoutingTable {
         let Some(entry) = self.table.get(&key) else {
             return false;
         };
+        // Routers must sync with the control plane at least once per (index, source).
+        if !entry.seeded_from_cp {
+            return false;
+        }
         entry.nodes.values().any(|node| {
             node.capacity_score > 0
                 && node.open_shard_count > 0
@@ -250,6 +259,7 @@ impl RoutingTable {
                     open_shard_count,
                 });
         }
+        entry.seeded_from_cp = true;
     }
 }
 
@@ -327,18 +337,33 @@ mod tests {
     fn test_has_open_nodes() {
         let mut table = RoutingTable::default();
         let pool = IngesterPool::default();
+        let index_uid = IndexUid::for_test("test-index", 0);
 
         // Empty table.
         assert!(!table.has_open_nodes("test-index", "test-source", &pool, &HashSet::new()));
 
+        // Seed from CP so has_open_nodes can return true.
+        let shards = vec![
+            Shard {
+                index_uid: Some(index_uid.clone()),
+                source_id: "test-source".to_string(),
+                shard_id: Some(ShardId::from(1u64)),
+                shard_state: ShardState::Open as i32,
+                leader_id: "node-1".to_string(),
+                ..Default::default()
+            },
+            Shard {
+                index_uid: Some(index_uid.clone()),
+                source_id: "test-source".to_string(),
+                shard_id: Some(ShardId::from(2u64)),
+                shard_state: ShardState::Open as i32,
+                leader_id: "node-2".to_string(),
+                ..Default::default()
+            },
+        ];
+        table.merge_from_shards(index_uid.clone(), "test-source".into(), shards);
+
         // Node exists but is not in pool.
-        table.apply_capacity_update(
-            "node-1".into(),
-            IndexUid::for_test("test-index", 0),
-            "test-source".into(),
-            8,
-            3,
-        );
         assert!(!table.has_open_nodes("test-index", "test-source", &pool, &HashSet::new()));
 
         // Node is in pool → true.
@@ -350,13 +375,6 @@ mod tests {
         assert!(!table.has_open_nodes("test-index", "test-source", &pool, &unavailable));
 
         // Second node available → true despite first being unavailable.
-        table.apply_capacity_update(
-            "node-2".into(),
-            IndexUid::for_test("test-index", 0),
-            "test-source".into(),
-            6,
-            2,
-        );
         pool.insert("node-2".into(), mocked_ingester(None));
         assert!(table.has_open_nodes("test-index", "test-source", &pool, &unavailable));
 
@@ -371,6 +389,40 @@ mod tests {
         assert!(!table.has_open_nodes("test-index", "test-source", &pool, &unavailable));
     }
 
+    #[test]
+    fn test_has_open_nodes_requires_cp_seed() {
+        let mut table = RoutingTable::default();
+        let pool = IngesterPool::default();
+        pool.insert("node-1".into(), mocked_ingester(None));
+
+        // Chitchat broadcast populates the entry, but has_open_nodes still returns false
+        // because the entry hasn't been seeded from the control plane yet.
+        table.apply_capacity_update(
+            "node-1".into(),
+            IndexUid::for_test("test-index", 0),
+            "test-source".into(),
+            8,
+            3,
+        );
+        assert!(!table.has_open_nodes("test-index", "test-source", &pool, &HashSet::new()));
+
+        // After merge_from_shards (CP response), has_open_nodes returns true.
+        let shards = vec![Shard {
+            index_uid: Some(IndexUid::for_test("test-index", 0)),
+            source_id: "test-source".to_string(),
+            shard_id: Some(ShardId::from(1u64)),
+            shard_state: ShardState::Open as i32,
+            leader_id: "node-1".to_string(),
+            ..Default::default()
+        }];
+        table.merge_from_shards(
+            IndexUid::for_test("test-index", 0),
+            "test-source".into(),
+            shards,
+        );
+        assert!(table.has_open_nodes("test-index", "test-source", &pool, &HashSet::new()));
+    }
+
     #[test]
     fn test_pick_node_prefers_same_az() {
         let mut table = RoutingTable::new(Some("az-1".to_string()));