diff --git a/lib/vagrant/protobufs/proto/vagrant_plugin_sdk/plugin_pb.rb b/lib/vagrant/protobufs/proto/vagrant_plugin_sdk/plugin_pb.rb
index dbd544b4b..d267ce6f3 100644
--- a/lib/vagrant/protobufs/proto/vagrant_plugin_sdk/plugin_pb.rb
+++ b/lib/vagrant/protobufs/proto/vagrant_plugin_sdk/plugin_pb.rb
@@ -338,6 +338,9 @@ Google::Protobuf::DescriptorPool.generated_pool.build do
     add_message "hashicorp.vagrant.sdk.Command.ExecuteResp" do
       optional :exit_code, :int64, 1
     end
+    add_message "hashicorp.vagrant.sdk.Command.SubcommandResp" do
+      repeated :commands, :string, 1
+    end
     add_message "hashicorp.vagrant.sdk.Command.Arguments" do
       repeated :flags, :message, 1, "hashicorp.vagrant.sdk.Command.Arguments.Flag"
       repeated :args, :string, 2
@@ -611,6 +614,7 @@ module Hashicorp
       Command::SynopsisResp = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("hashicorp.vagrant.sdk.Command.SynopsisResp").msgclass
       Command::FlagsResp = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("hashicorp.vagrant.sdk.Command.FlagsResp").msgclass
       Command::ExecuteResp = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("hashicorp.vagrant.sdk.Command.ExecuteResp").msgclass
+      Command::SubcommandResp = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("hashicorp.vagrant.sdk.Command.SubcommandResp").msgclass
       Command::Arguments = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("hashicorp.vagrant.sdk.Command.Arguments").msgclass
       Command::Arguments::Flag = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("hashicorp.vagrant.sdk.Command.Arguments.Flag").msgclass
       Command::Arguments::Flag::Type = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("hashicorp.vagrant.sdk.Command.Arguments.Flag.Type").enummodule
diff --git a/lib/vagrant/protobufs/proto/vagrant_plugin_sdk/plugin_services_pb.rb b/lib/vagrant/protobufs/proto/vagrant_plugin_sdk/plugin_services_pb.rb
index 1ba39e4d9..02b9d465b 100644
--- a/lib/vagrant/protobufs/proto/vagrant_plugin_sdk/plugin_services_pb.rb
+++ b/lib/vagrant/protobufs/proto/vagrant_plugin_sdk/plugin_services_pb.rb
@@ -149,6 +149,8 @@ module Hashicorp
           rpc :Flags, ::Hashicorp::Vagrant::Sdk::FuncSpec::Args, ::Hashicorp::Vagrant::Sdk::Command::FlagsResp
           rpc :ExecuteSpec, ::Google::Protobuf::Empty, ::Hashicorp::Vagrant::Sdk::FuncSpec
           rpc :Execute, ::Hashicorp::Vagrant::Sdk::FuncSpec::Args, ::Hashicorp::Vagrant::Sdk::Command::ExecuteResp
+          rpc :SubcommandSpec, ::Google::Protobuf::Empty, ::Hashicorp::Vagrant::Sdk::FuncSpec
+          rpc :Subcommands, ::Hashicorp::Vagrant::Sdk::FuncSpec::Args, ::Hashicorp::Vagrant::Sdk::Command::SubcommandResp
         end
 
         Stub = Service.rpc_stub_class
diff --git a/plugins/commands/serve/service/command_service.rb b/plugins/commands/serve/service/command_service.rb
index 806824b32..f906b024b 100644
--- a/plugins/commands/serve/service/command_service.rb
+++ b/plugins/commands/serve/service/command_service.rb
@@ -67,6 +67,19 @@ module VagrantPlugins
           end
         end
 
+        def subcommand_spec(*args)
+          return SDK::FuncSpec.new
+        end
+
+        def subcommands(req, ctx)
+          ServiceInfo.with_info(ctx) do |info|
+            
+          end
+          SDK::Command::SubcommandResp.new(
+            commands: ["test", "thing"],
+          )
+        end
+
         def augment_cmd_class(cmd_cls)
           # Create a new anonymous class based on the command class
           # so we can modify the setup behavior