docs(subnet-splitting): mention splitting in registry CUPs

rs/cup_explorer/src/lib.rs

@@ -60,9 +60,9 @@ fn get_subnet_id(cup: &CatchUpPackage) -> Result<SubnetId, String> {
     // If the DKG key material was signed by the subnet itself — use it.
     match dkg_id.target_subnet {
         NiDkgTargetSubnet::Local => Ok(dkg_id.dealer_subnet),
-        // If we hit this case, then the local CUP is a genesis or recovery CUP of an application
-        // subnet or of the NNS subnet recovered on failover nodes. We cannot derive the subnet id
-        // from it.
+        // If we hit this case, then the local CUP is a genesis, recovery or post-split CUP of an
+        // application subnet or of the NNS subnet recovered on failover nodes. We cannot derive
+        // the subnet id from it.
         NiDkgTargetSubnet::Remote(_) => {
             Err("Registry CUPs cannot be verified with this tool".into())
         }

rs/orchestrator/src/catch_up_package_provider.rs

@@ -573,7 +573,7 @@ impl CatchUpPackageProvider {
         // version A creates a local unsigned CUP from the registry contents, persists it, then
         // detects a new replica version B, upgrades to it and starts the replica on the previously
         // created CUP. Now since such a case might happen on a new subnet creation or during a
-        // subnet recover with failover nodes, all nodes before upgrading to B might have been on
+        // subnet recovery with failover nodes, all nodes before upgrading to B might have been on
         // different versions and hence might have created different CUPs, which are then consumed
         // by the same replica version B, which is not guaranteed to be deterministic.
         //

rs/orchestrator/src/registry_helper.rs

@@ -157,7 +157,7 @@ impl RegistryHelper {
             ))
     }
 
-    /// Return the genesis cup at the given registry version for this node
+    /// Return the genesis/recovery CUP at the given registry version for this node
     pub(crate) fn get_registry_cup(
         &self,
         version: RegistryVersion,

rs/orchestrator/src/upgrade.rs

@@ -804,10 +804,11 @@ fn get_subnet_id(registry: &RegistryHelper, cup: &CatchUpPackage) -> Result<Subn
     // the subnet id from the registry.
     match dkg_id.target_subnet {
         NiDkgTargetSubnet::Local => Ok(dkg_id.dealer_subnet),
-        // If we hit this case, then the local CUP is a genesis or recovery CUP of an application
-        // subnet or of the NNS subnet recovered on failover nodes. We cannot derive the subnet id
-        // from it, so we use the registry version of that CUP and the node id of one of the
-        // high-threshold committee members, to find out to which subnet this node belongs to.
+        // If we hit this case, then the local CUP is a genesis, recovery or post-split CUP of an
+        // application subnet or of the NNS subnet recovered on failover nodes. We cannot derive
+        // the subnet id from it, so we use the registry version of that CUP and the node id of one
+        // of the high-threshold committee members, to find out to which subnet this node belongs
+        // to.
         NiDkgTargetSubnet::Remote(_) => {
             let node_id = dkg_summary
                 .current_transcripts()

rs/protobuf/def/registry/subnet/v1/subnet.proto

@@ -147,7 +147,8 @@ message ChainKeyInitialization {
 
 // Contains the initial DKG transcripts for the subnet and materials to construct a base CUP (i.e.
 // a CUP with no dependencies on previous CUPs or blocks). Such CUP materials can be used to
-// construct the genesis CUP or a recovery CUP in the event of a subnet stall.
+// construct the genesis CUP, a recovery CUP in the event of a subnet stall, or a post-split CUP
+// when the subnet is split in two.
 message CatchUpPackageContents {
   // Initial non-interactive low-threshold DKG transcript
   InitialNiDkgTranscriptRecord initial_ni_dkg_transcript_low_threshold = 1;

rs/protobuf/src/gen/registry/registry.subnet.v1.rs

@@ -144,7 +144,8 @@ pub mod chain_key_initialization {
 }
 /// Contains the initial DKG transcripts for the subnet and materials to construct a base CUP (i.e.
 /// a CUP with no dependencies on previous CUPs or blocks). Such CUP materials can be used to
-/// construct the genesis CUP or a recovery CUP in the event of a subnet stall.
+/// construct the genesis CUP, a recovery CUP in the event of a subnet stall, or a post-split CUP
+/// when the subnet is split in two.
 #[derive(serde::Serialize, serde::Deserialize, Clone, PartialEq, ::prost::Message)]
 pub struct CatchUpPackageContents {
     /// Initial non-interactive low-threshold DKG transcript

rs/protobuf/src/gen/state/registry.subnet.v1.rs

@@ -144,7 +144,8 @@ pub mod chain_key_initialization {
 }
 /// Contains the initial DKG transcripts for the subnet and materials to construct a base CUP (i.e.
 /// a CUP with no dependencies on previous CUPs or blocks). Such CUP materials can be used to
-/// construct the genesis CUP or a recovery CUP in the event of a subnet stall.
+/// construct the genesis CUP, a recovery CUP in the event of a subnet stall, or a post-split CUP
+/// when the subnet is split in two.
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct CatchUpPackageContents {
     /// Initial non-interactive low-threshold DKG transcript

rs/protobuf/src/gen/types/registry.subnet.v1.rs

@@ -144,7 +144,8 @@ pub mod chain_key_initialization {
 }
 /// Contains the initial DKG transcripts for the subnet and materials to construct a base CUP (i.e.
 /// a CUP with no dependencies on previous CUPs or blocks). Such CUP materials can be used to
-/// construct the genesis CUP or a recovery CUP in the event of a subnet stall.
+/// construct the genesis CUP, a recovery CUP in the event of a subnet stall, or a post-split CUP
+/// when the subnet is split in two.
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct CatchUpPackageContents {
     /// Initial non-interactive low-threshold DKG transcript

rs/registry/helpers/src/subnet.rs

@@ -223,8 +223,8 @@ pub trait SubnetRegistry {
         version: RegistryVersion,
     ) -> RegistryClientResult<Vec<(SubnetId, SubnetRecord)>>;
 
-    /// Get the necessary material to construct a genesis/recovery CUP for the
-    /// given subnet
+    /// Get the necessary material to construct a genesis/recovery/post-split CUP
+    /// for the given subnet
     fn get_cup_contents(
         &self,
         subnet_id: SubnetId,