diff --git a/plugins/commands/serve/service/capability_platform_service.rb b/plugins/commands/serve/service/capability_platform_service.rb
index ad7f626ee..286717621 100644
--- a/plugins/commands/serve/service/capability_platform_service.rb
+++ b/plugins/commands/serve/service/capability_platform_service.rb
@@ -24,12 +24,12 @@ module VagrantPlugins
 
         # TODO(spox): request scoping for seed values - needs investigation
         def seed(req, ctx)
-          @seeds = req.list.to_a
+          @seeds = req.arguments.to_a
           Empty.new
         end
 
         def seeds(req, ctx)
-          SDK::Args::Direct.new(list: @seeds)
+          SDK::Args::Direct.new(arguments: @seeds)
         end
 
         def has_capability_spec(*_)
@@ -68,7 +68,7 @@ module VagrantPlugins
         def capability_spec(req, ctx)
           SDK::FuncSpec.new(
             name: "capability_spec",
-            args: default_args + [
+            args: default_args.values + [
               SDK::FuncSpec::Value.new(
                 type: "hashicorp.vagrant.sdk.Args.Direct",
                 name: "",
@@ -93,10 +93,16 @@ module VagrantPlugins
             caps_registry = capabilities[plugin_name]
             target_cap = caps_registry.get(cap_name)
 
-            args = mapper.funcspec_map(req.func_args, mapper, broker)
-            args = [args.first] + args.last
+            args = mapper.funcspec_map(
+              req.func_args,
+              expect: default_args.keys + [Types::Direct]
+            )
+            args = capability_arguments(args)
             cap_method = target_cap.method(cap_name)
 
+            arg_list = args.join("\n  - ")
+            logger.debug("arguments to be passed to #{cap_name} on plugin #{plugin_name}:\n  - #{arg_list}")
+
             result = cap_method.call(*args)
 
             val = Google::Protobuf::Value.new
@@ -106,6 +112,11 @@ module VagrantPlugins
             )
           end
         end
+
+        def capability_arguments(args)
+          direct = args.pop
+          args + direct.arguments
+        end
       end
     end
   end
diff --git a/plugins/commands/serve/service/guest_service.rb b/plugins/commands/serve/service/guest_service.rb
index c087d1c10..3bce7980b 100644
--- a/plugins/commands/serve/service/guest_service.rb
+++ b/plugins/commands/serve/service/guest_service.rb
@@ -9,13 +9,12 @@ module VagrantPlugins
 
         def initialize(*args, **opts, &block)
           caps = Vagrant.plugin("2").manager.guest_capabilities
-          default_args = [
-            # Always get a target to pass the guest capability
-            SDK::FuncSpec::Value.new(
+          default_args = {
+            Client::Target => SDK::FuncSpec::Value.new(
               type: "hashicorp.vagrant.sdk.Args.Target",
               name: "",
             ),
-          ]
+          }
           initialize_capability_platform!(caps, default_args)
         end
 
@@ -40,10 +39,7 @@ module VagrantPlugins
         def detect(req, ctx)
           with_info(ctx) do |info|
             plugin_name = info.plugin_name
-            target = mapper.funcspec_map(req, expect: Client::Target)
-            project = target.project
-            env = Vagrant::Environment.new({client: project})
-            machine = env.machine(target.name.to_sym, target.provider_name.to_sym)
+            machine = mapper.funcspec_map(req, expect: Vagrant::Machine)
             plugin = Vagrant.plugin("2").manager.guests[plugin_name.to_s.to_sym].to_a.first
             if !plugin
               logger.debug("Failed to locate guest plugin for: #{plugin_name}")
@@ -86,6 +82,16 @@ module VagrantPlugins
             )
           end
         end
+
+        def capability_arguments(args)
+          target, direct = args
+          nargs = direct.args.dup
+          if !nargs.first.is_a?(Vagrant::Machine)
+            nargs.unshift(mapper.map(target, to: Vagrant::Machine))
+          end
+
+          nargs
+        end
       end
     end
   end
diff --git a/plugins/commands/serve/service/host_service.rb b/plugins/commands/serve/service/host_service.rb
index b9b9bd5be..942ab1620 100644
--- a/plugins/commands/serve/service/host_service.rb
+++ b/plugins/commands/serve/service/host_service.rb
@@ -9,13 +9,12 @@ module VagrantPlugins
 
         def initialize(*args, **opts, &block)
           caps = Vagrant.plugin("2").manager.host_capabilities
-          default_args = [
-            # Always get the state bag for host capabilities
-            SDK::FuncSpec::Value.new(
+          default_args = {
+            Vagrant::Environment => SDK::FuncSpec::Value.new(
               type: "hashicorp.vagrant.sdk.Args.Project",
               name: "",
             ),
-          ]
+          }
           initialize_capability_platform!(caps, default_args)
         end