diff --git a/include/nighthawk/adaptive_load/BUILD b/include/nighthawk/adaptive_load/BUILD
index 1e0728795..fd658e9f0 100644
--- a/include/nighthawk/adaptive_load/BUILD
+++ b/include/nighthawk/adaptive_load/BUILD
@@ -35,6 +35,7 @@ envoy_basic_cc_library(
         "@envoy//include/envoy/common:base_includes",
         "@envoy//include/envoy/common:time_interface",
         "@envoy//include/envoy/config:typed_config_interface",
+        "@envoy//source/common/protobuf:protobuf_with_external_headers",
     ],
 )
 
diff --git a/include/nighthawk/adaptive_load/metrics_evaluator.h b/include/nighthawk/adaptive_load/metrics_evaluator.h
index cc969a9dd..c72d03427 100644
--- a/include/nighthawk/adaptive_load/metrics_evaluator.h
+++ b/include/nighthawk/adaptive_load/metrics_evaluator.h
@@ -1,8 +1,9 @@
+#pragma once
+
 #include "envoy/config/core/v3/base.pb.h"
 
 #include "nighthawk/adaptive_load/metrics_plugin.h"
 
-#include "external/envoy/source/common/common/logger.h"
 #include "external/envoy/source/common/common/statusor.h"
 #include "external/envoy/source/common/protobuf/protobuf.h"
 
diff --git a/include/nighthawk/adaptive_load/session_spec_proto_helper.h b/include/nighthawk/adaptive_load/session_spec_proto_helper.h
index 06e77ded7..a8850c6b9 100644
--- a/include/nighthawk/adaptive_load/session_spec_proto_helper.h
+++ b/include/nighthawk/adaptive_load/session_spec_proto_helper.h
@@ -25,7 +25,7 @@ class AdaptiveLoadSessionSpecProtoHelper {
    * @return Adaptive load session spec with default values inserted.
    */
   virtual nighthawk::adaptive_load::AdaptiveLoadSessionSpec
-  SetSessionSpecDefaults(nighthawk::adaptive_load::AdaptiveLoadSessionSpec spec) PURE;
+  SetSessionSpecDefaults(nighthawk::adaptive_load::AdaptiveLoadSessionSpec spec) const PURE;
 
   /**
    * Checks whether a session spec is valid: No forbidden fields in Nighthawk traffic spec; no bad
@@ -37,7 +37,7 @@ class AdaptiveLoadSessionSpecProtoHelper {
    * @return Status OK if no problems were found, or InvalidArgument with all errors.
    */
   virtual absl::Status
-  CheckSessionSpec(const nighthawk::adaptive_load::AdaptiveLoadSessionSpec& spec) PURE;
+  CheckSessionSpec(const nighthawk::adaptive_load::AdaptiveLoadSessionSpec& spec) const PURE;
 };
 
 } // namespace Nighthawk
\ No newline at end of file
diff --git a/include/nighthawk/common/nighthawk_service_client.h b/include/nighthawk/common/nighthawk_service_client.h
index 4226837c6..e49ecf654 100644
--- a/include/nighthawk/common/nighthawk_service_client.h
+++ b/include/nighthawk/common/nighthawk_service_client.h
@@ -10,7 +10,7 @@
 namespace Nighthawk {
 
 /**
- * An interface for interacting with a Nighthawk Service gRPC stub.
+ * An interface for a stateless helper that interacts with a Nighthawk Service gRPC stub.
  */
 class NighthawkServiceClient {
 public:
@@ -30,7 +30,7 @@ class NighthawkServiceClient {
    */
   virtual absl::StatusOr<nighthawk::client::ExecutionResponse> PerformNighthawkBenchmark(
       nighthawk::client::NighthawkService::StubInterface* nighthawk_service_stub,
-      const nighthawk::client::CommandLineOptions& command_line_options) PURE;
+      const nighthawk::client::CommandLineOptions& command_line_options) const PURE;
 };
 
 } // namespace Nighthawk
diff --git a/source/adaptive_load/session_spec_proto_helper_impl.cc b/source/adaptive_load/session_spec_proto_helper_impl.cc
index 3c45d3d86..be8f53bcf 100644
--- a/source/adaptive_load/session_spec_proto_helper_impl.cc
+++ b/source/adaptive_load/session_spec_proto_helper_impl.cc
@@ -16,7 +16,7 @@ namespace Nighthawk {
 
 nighthawk::adaptive_load::AdaptiveLoadSessionSpec
 AdaptiveLoadSessionSpecProtoHelperImpl::SetSessionSpecDefaults(
-    nighthawk::adaptive_load::AdaptiveLoadSessionSpec spec) {
+    nighthawk::adaptive_load::AdaptiveLoadSessionSpec spec) const {
   if (!spec.nighthawk_traffic_template().has_open_loop()) {
     spec.mutable_nighthawk_traffic_template()->mutable_open_loop()->set_value(true);
   }
@@ -48,7 +48,7 @@ AdaptiveLoadSessionSpecProtoHelperImpl::SetSessionSpecDefaults(
 }
 
 absl::Status AdaptiveLoadSessionSpecProtoHelperImpl::CheckSessionSpec(
-    const nighthawk::adaptive_load::AdaptiveLoadSessionSpec& spec) {
+    const nighthawk::adaptive_load::AdaptiveLoadSessionSpec& spec) const {
   std::vector<std::string> errors;
   if (spec.nighthawk_traffic_template().has_duration()) {
     errors.emplace_back(
diff --git a/source/adaptive_load/session_spec_proto_helper_impl.h b/source/adaptive_load/session_spec_proto_helper_impl.h
index d47e3a680..d26dcd586 100644
--- a/source/adaptive_load/session_spec_proto_helper_impl.h
+++ b/source/adaptive_load/session_spec_proto_helper_impl.h
@@ -5,10 +5,10 @@ namespace Nighthawk {
 class AdaptiveLoadSessionSpecProtoHelperImpl : public AdaptiveLoadSessionSpecProtoHelper {
 public:
   nighthawk::adaptive_load::AdaptiveLoadSessionSpec
-  SetSessionSpecDefaults(nighthawk::adaptive_load::AdaptiveLoadSessionSpec spec) override;
+  SetSessionSpecDefaults(nighthawk::adaptive_load::AdaptiveLoadSessionSpec spec) const override;
 
   absl::Status
-  CheckSessionSpec(const nighthawk::adaptive_load::AdaptiveLoadSessionSpec& spec) override;
+  CheckSessionSpec(const nighthawk::adaptive_load::AdaptiveLoadSessionSpec& spec) const override;
 };
 
 } // namespace Nighthawk
diff --git a/source/common/nighthawk_service_client_impl.cc b/source/common/nighthawk_service_client_impl.cc
index db8f1c7dd..10dc82588 100644
--- a/source/common/nighthawk_service_client_impl.cc
+++ b/source/common/nighthawk_service_client_impl.cc
@@ -7,7 +7,7 @@ namespace Nighthawk {
 absl::StatusOr<nighthawk::client::ExecutionResponse>
 NighthawkServiceClientImpl::PerformNighthawkBenchmark(
     nighthawk::client::NighthawkService::StubInterface* nighthawk_service_stub,
-    const nighthawk::client::CommandLineOptions& command_line_options) {
+    const nighthawk::client::CommandLineOptions& command_line_options) const {
   nighthawk::client::ExecutionRequest request;
   nighthawk::client::ExecutionResponse response;
   *request.mutable_start_request()->mutable_options() = command_line_options;
diff --git a/source/common/nighthawk_service_client_impl.h b/source/common/nighthawk_service_client_impl.h
index 2dd29862e..d8a14eb44 100644
--- a/source/common/nighthawk_service_client_impl.h
+++ b/source/common/nighthawk_service_client_impl.h
@@ -19,7 +19,7 @@ class NighthawkServiceClientImpl : public NighthawkServiceClient {
 public:
   absl::StatusOr<nighthawk::client::ExecutionResponse> PerformNighthawkBenchmark(
       nighthawk::client::NighthawkService::StubInterface* nighthawk_service_stub,
-      const nighthawk::client::CommandLineOptions& command_line_options) override;
+      const nighthawk::client::CommandLineOptions& command_line_options) const override;
 };
 
 } // namespace Nighthawk