diff --git a/python/sglang/srt/mem_cache/unified_cache/unified_tree_core_interface.py b/python/sglang/srt/mem_cache/unified_cache/unified_tree_core_interface.py
index 681567984..8111d0871 100644
--- a/python/sglang/srt/mem_cache/unified_cache/unified_tree_core_interface.py
+++ b/python/sglang/srt/mem_cache/unified_cache/unified_tree_core_interface.py
@@ -510,6 +510,9 @@ class UnifiedTreeCoreInterface(ABC):
         node_id: NodeId,
         phase: CacheTransferPhase,
         *,
+        # TODO(Jialin): Remove the legacy `host_indices` argument from the
+        # interface and bindings. Prefetch uses `staging_tokens`;
+        # `PoolTransfer.host_indices` is populated after the storage hit.
         host_indices: Optional[torch.Tensor] = None,
         token_ids: Optional[Sequence[int]] = None,
         prefetch_tokens: int = 0,
diff --git a/rust/sglang-radix-tree/src/tests/components/mamba.rs b/rust/sglang-radix-tree/src/tests/components/mamba.rs
index f223e7784..666f11d3b 100644
--- a/rust/sglang-radix-tree/src/tests/components/mamba.rs
+++ b/rust/sglang-radix-tree/src/tests/components/mamba.rs
@@ -1068,11 +1068,11 @@ fn backup_host_build_carries_the_device_slot() {
             MAMBA,
             tc.arena.node(a).id,
             CacheTransferPhase::BackupHost,
-            None,
-            None,
-            0,
-            0,
-            None,
+            /* host_indices = */ None,
+            /* token_ids = */ None,
+            /* prefetch_tokens = */ 0,
+            /* staging_tokens = */ 0,
+            /* last_hash = */ None,
         )
         .expect("live test node")
         .unwrap();
@@ -1100,11 +1100,11 @@ fn backup_host_build_carries_the_device_slot() {
             MAMBA,
             tc.arena.node(b).id,
             CacheTransferPhase::BackupHost,
-            None,
-            None,
-            0,
-            0,
-            None,
+            /* host_indices = */ None,
+            /* token_ids = */ None,
+            /* prefetch_tokens = */ 0,
+            /* staging_tokens = */ 0,
+            /* last_hash = */ None,
         )
         .expect("live test node")
         .is_none()
@@ -1121,11 +1121,11 @@ fn load_back_build_restores_the_host_only_node() {
             MAMBA,
             tc.arena.node(a).id,
             CacheTransferPhase::LoadBack,
-            None,
-            None,
-            0,
-            0,
-            None,
+            /* host_indices = */ None,
+            /* token_ids = */ None,
+            /* prefetch_tokens = */ 0,
+            /* staging_tokens = */ 0,
+            /* last_hash = */ None,
         )
         .expect("live test node")
         .unwrap();
@@ -1151,11 +1151,11 @@ fn load_back_build_skips_device_backed_and_bare_nodes() {
                 MAMBA,
                 tc.arena.node(node).id,
                 CacheTransferPhase::LoadBack,
-                None,
-                None,
-                0,
-                0,
-                None,
+                /* host_indices = */ None,
+                /* token_ids = */ None,
+                /* prefetch_tokens = */ 0,
+                /* staging_tokens = */ 0,
+                /* last_hash = */ None,
             )
             .expect("live test node")
             .is_none()
@@ -1174,11 +1174,11 @@ fn load_back_build_adds_the_per_request_cow_transfer() {
             a,
             CacheTransferPhase::LoadBack,
             /* mamba_pool_idx = */ Some(Tensor::from_slice(&[3i64]).squeeze()),
-            None,
-            None,
-            0,
-            0,
-            None,
+            /* host_indices = */ None,
+            /* token_ids = */ None,
+            /* prefetch_tokens = */ 0,
+            /* staging_tokens = */ 0,
+            /* last_hash = */ None,
         )
         .unwrap()
         .unwrap();
@@ -1390,11 +1390,11 @@ fn backup_storage_build_keys_the_trailing_hash() {
             MAMBA,
             tc.arena.node(a).id,
             CacheTransferPhase::BackupStorage,
-            None,
-            None,
-            0,
-            0,
-            None,
+            /* host_indices = */ None,
+            /* token_ids = */ None,
+            /* prefetch_tokens = */ 0,
+            /* staging_tokens = */ 0,
+            /* last_hash = */ None,
         )
         .expect("live test node")
         .is_none()
@@ -1406,11 +1406,11 @@ fn backup_storage_build_keys_the_trailing_hash() {
             MAMBA,
             tc.arena.node(a).id,
             CacheTransferPhase::BackupStorage,
-            None,
-            None,
-            0,
-            0,
-            None,
+            /* host_indices = */ None,
+            /* token_ids = */ None,
+            /* prefetch_tokens = */ 0,
+            /* staging_tokens = */ 0,
+            /* last_hash = */ None,
         )
         .expect("live test node")
         .is_none()
@@ -1421,11 +1421,11 @@ fn backup_storage_build_keys_the_trailing_hash() {
             MAMBA,
             tc.arena.node(a).id,
             CacheTransferPhase::BackupStorage,
-            None,
-            None,
-            0,
-            0,
-            None,
+            /* host_indices = */ None,
+            /* token_ids = */ None,
+            /* prefetch_tokens = */ 0,
+            /* staging_tokens = */ 0,
+            /* last_hash = */ None,
         )
         .expect("live test node")
         .unwrap();
@@ -1450,11 +1450,11 @@ fn prefetch_build_carries_a_placeholder_key_for_the_planned_slot() {
             MAMBA,
             root_id,
             CacheTransferPhase::Prefetch,
-            None,
-            None,
-            0,
-            staging_tokens,
-            None,
+            /* host_indices = */ None,
+            /* token_ids = */ None,
+            /* prefetch_tokens = */ 0,
+            /* staging_tokens = */ staging_tokens,
+            /* last_hash = */ None,
         )
         .expect("live test node")
     };