Rename Compatibility class to ProtocolTraits

...and move it to the common stage.

33 files changed, 127 insertions, 98 deletions

diff --git a/test/buildtool/build_engine/base_maps/TARGETS b/test/buildtool/build_engine/base_maps/TARGETS
index 855d6217..2c5f4029 100644
--- a/test/buildtool/build_engine/base_maps/TARGETS
+++ b/test/buildtool/build_engine/base_maps/TARGETS
@@ -63,6 +63,7 @@
     , ["", "catch-main"]
     , ["@", "json", "", "json"]
     , ["@", "src", "src/buildtool/common", "config"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/build_engine/base_maps", "directory_map"]
     , ["@", "src", "src/buildtool/build_engine/base_maps", "source_map"]
     , ["@", "src", "src/buildtool/build_engine/base_maps", "entity_name_data"]
diff --git a/test/buildtool/build_engine/base_maps/source_map.test.cpp b/test/buildtool/build_engine/base_maps/source_map.test.cpp
index 44c6863a..b6c7f1c1 100644
--- a/test/buildtool/build_engine/base_maps/source_map.test.cpp
+++ b/test/buildtool/build_engine/base_maps/source_map.test.cpp
@@ -25,6 +25,7 @@
 #include "src/buildtool/build_engine/base_maps/directory_map.hpp"
 #include "src/buildtool/build_engine/base_maps/entity_name.hpp"
 #include "src/buildtool/build_engine/base_maps/entity_name_data.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/repository_config.hpp"
 #include "src/buildtool/file_system/file_root.hpp"
 #include "src/buildtool/multithreading/async_map_consumer.hpp"
@@ -102,7 +103,8 @@ TEST_CASE("from file") {
         CHECK(ReadSourceTarget(name, consumer, /*use_git=*/true));
         CHECK(artifacts["file"]["type"] == "KNOWN");
         CHECK(artifacts["file"]["data"]["id"] ==
-              (Compatibility::IsCompatible() ? kEmptySha256 : kEmptySha1));
+              (ProtocolTraits::Instance().IsCompatible() ? kEmptySha256
+                                                         : kEmptySha1));
         CHECK(artifacts["file"]["data"]["size"] == 0);
     }
 }
@@ -168,7 +170,8 @@ TEST_CASE("subdir file") {
         CHECK(ReadSourceTarget(name, consumer, /*use_git=*/true));
         CHECK(artifacts["bar/file"]["type"] == "KNOWN");
         CHECK(artifacts["bar/file"]["data"]["id"] ==
-              (Compatibility::IsCompatible() ? kEmptySha256 : kEmptySha1));
+              (ProtocolTraits::Instance().IsCompatible() ? kEmptySha256
+                                                         : kEmptySha1));
         CHECK(artifacts["bar/file"]["data"]["size"] == 0);
     }
 }
@@ -189,9 +192,9 @@ TEST_CASE("subdir symlink") {
     SECTION("via git tree") {
         CHECK(ReadSourceTarget(name, consumer, /*use_git=*/true));
         CHECK(artifacts["link"]["type"] == "KNOWN");
-        CHECK(artifacts["link"]["data"]["id"] == (Compatibility::IsCompatible()
-                                                      ? kSrcLinkIdSha256
-                                                      : kSrcLinkIdSha1));
+        CHECK(artifacts["link"]["data"]["id"] ==
+              (ProtocolTraits::Instance().IsCompatible() ? kSrcLinkIdSha256
+                                                         : kSrcLinkIdSha1));
         CHECK(artifacts["link"]["data"]["size"] == 5);  // content: dummy
     }
 }
diff --git a/test/buildtool/common/TARGETS b/test/buildtool/common/TARGETS
index ef1fff25..1355af3f 100644
--- a/test/buildtool/common/TARGETS
+++ b/test/buildtool/common/TARGETS
@@ -9,9 +9,9 @@
     , ["@", "src", "src/buildtool/common", "artifact_description"]
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
     , ["@", "src", "src/buildtool/file_system", "object_type"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     ]
   , "stage": ["test", "buildtool", "common"]
   }
@@ -25,8 +25,8 @@
     , ["@", "json", "", "json"]
     , ["@", "src", "src/buildtool/common", "action_description"]
     , ["@", "src", "src/buildtool/common", "common"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     ]
   , "stage": ["test", "buildtool", "common"]
   }
diff --git a/test/buildtool/common/action_description.test.cpp b/test/buildtool/common/action_description.test.cpp
index 7d5a72d7..504f6aa3 100644
--- a/test/buildtool/common/action_description.test.cpp
+++ b/test/buildtool/common/action_description.test.cpp
@@ -20,7 +20,7 @@
 #include "nlohmann/json.hpp"
 #include "src/buildtool/common/action.hpp"
 #include "src/buildtool/common/artifact_description.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 
 [[nodiscard]] static inline auto GetHashType(bool compatible) noexcept
@@ -45,7 +45,8 @@ TEST_CASE("From JSON", "[action_description]") {
                           desc.Inputs()}
             .ToJson();
 
-    auto const hash_type = GetHashType(Compatibility::IsCompatible());
+    auto const hash_type =
+        GetHashType(ProtocolTraits::Instance().IsCompatible());
     SECTION("Parse full action") {
         auto description = ActionDescription::FromJson(hash_type, "id", json);
         REQUIRE(description);
diff --git a/test/buildtool/common/artifact_description.test.cpp b/test/buildtool/common/artifact_description.test.cpp
index a05baa66..99a24964 100644
--- a/test/buildtool/common/artifact_description.test.cpp
+++ b/test/buildtool/common/artifact_description.test.cpp
@@ -22,12 +22,12 @@
 #include "src/buildtool/common/artifact.hpp"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
 
 static auto NamedDigest(std::string const& str) -> ArtifactDigest {
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
     return ArtifactDigestFactory::HashDataAs<ObjectType::File>(hash_function,
@@ -50,7 +50,8 @@ TEST_CASE("Local artifact", "[artifact_description]") {
     auto local_desc = ArtifactDescription::CreateLocal(
         std::filesystem::path{"local_path"}, "repo");
     auto from_json = ArtifactDescription::FromJson(
-        GetHashType(Compatibility::IsCompatible()), local_desc.ToJson());
+        GetHashType(ProtocolTraits::Instance().IsCompatible()),
+        local_desc.ToJson());
     CHECK(local_desc == *from_json);
 }
 
@@ -59,21 +60,24 @@ TEST_CASE("Known artifact", "[artifact_description]") {
         auto known_desc = ArtifactDescription::CreateKnown(
             NamedDigest("f_fake_hash"), ObjectType::File);
         auto from_json = ArtifactDescription::FromJson(
-            GetHashType(Compatibility::IsCompatible()), known_desc.ToJson());
+            GetHashType(ProtocolTraits::Instance().IsCompatible()),
+            known_desc.ToJson());
         CHECK(known_desc == *from_json);
     }
     SECTION("Executable object") {
         auto known_desc = ArtifactDescription::CreateKnown(
             NamedDigest("x_fake_hash"), ObjectType::Executable);
         auto from_json = ArtifactDescription::FromJson(
-            GetHashType(Compatibility::IsCompatible()), known_desc.ToJson());
+            GetHashType(ProtocolTraits::Instance().IsCompatible()),
+            known_desc.ToJson());
         CHECK(known_desc == *from_json);
     }
     SECTION("Symlink object") {
         auto known_desc = ArtifactDescription::CreateKnown(
             NamedDigest("l_fake_hash"), ObjectType::Symlink);
         auto from_json = ArtifactDescription::FromJson(
-            GetHashType(Compatibility::IsCompatible()), known_desc.ToJson());
+            GetHashType(ProtocolTraits::Instance().IsCompatible()),
+            known_desc.ToJson());
         CHECK(known_desc == *from_json);
     }
 }
@@ -82,7 +86,8 @@ TEST_CASE("Action artifact", "[artifact_description]") {
     auto action_desc = ArtifactDescription::CreateAction(
         "action_id", std::filesystem::path{"out_path"});
     auto from_json = ArtifactDescription::FromJson(
-        GetHashType(Compatibility::IsCompatible()), action_desc.ToJson());
+        GetHashType(ProtocolTraits::Instance().IsCompatible()),
+        action_desc.ToJson());
     CHECK(action_desc == *from_json);
 }
 
@@ -93,7 +98,8 @@ TEST_CASE("From JSON", "[artifact_description]") {
             .ToJson();
     auto action = ArtifactDescription::CreateAction("id", "output").ToJson();
 
-    auto const hash_type = GetHashType(Compatibility::IsCompatible());
+    auto const hash_type =
+        GetHashType(ProtocolTraits::Instance().IsCompatible());
     SECTION("Parse artifacts") {
         CHECK(ArtifactDescription::FromJson(hash_type, local));
         CHECK(ArtifactDescription::FromJson(hash_type, known));
@@ -172,10 +178,10 @@ TEST_CASE("Description missing mandatory key/value pair",
           "[artifact_description]") {
     nlohmann::json const missing_type = {{"data", {{"path", "some/path"}}}};
     CHECK(not ArtifactDescription::FromJson(
-        GetHashType(Compatibility::IsCompatible()), missing_type));
+        GetHashType(ProtocolTraits::Instance().IsCompatible()), missing_type));
     nlohmann::json const missing_data = {{"type", "LOCAL"}};
     CHECK(not ArtifactDescription::FromJson(
-        GetHashType(Compatibility::IsCompatible()), missing_data));
+        GetHashType(ProtocolTraits::Instance().IsCompatible()), missing_data));
 }
 
 TEST_CASE("Local artifact description contains incorrect value for \"data\"",
@@ -183,7 +189,8 @@ TEST_CASE("Local artifact description contains incorrect value for \"data\"",
     nlohmann::json const local_art_missing_path = {
         {"type", "LOCAL"}, {"data", nlohmann::json::object()}};
     CHECK(not ArtifactDescription::FromJson(
-        GetHashType(Compatibility::IsCompatible()), local_art_missing_path));
+        GetHashType(ProtocolTraits::Instance().IsCompatible()),
+        local_art_missing_path));
 }
 
 TEST_CASE("Known artifact description contains incorrect value for \"data\"",
@@ -195,14 +202,15 @@ TEST_CASE("Known artifact description contains incorrect value for \"data\"",
             {"type", "KNOWN"},
             {"data", {{"size", 15}, {"file_type", file_type}}}};
         CHECK(not ArtifactDescription::FromJson(
-            GetHashType(Compatibility::IsCompatible()), known_art_missing_id));
+            GetHashType(ProtocolTraits::Instance().IsCompatible()),
+            known_art_missing_id));
     }
     SECTION("missing \"size\"") {
         nlohmann::json const known_art_missing_size = {
             {"type", "KNOWN"},
             {"data", {{"id", "known_input"}, {"file_type", file_type}}}};
         CHECK(not ArtifactDescription::FromJson(
-            GetHashType(Compatibility::IsCompatible()),
+            GetHashType(ProtocolTraits::Instance().IsCompatible()),
             known_art_missing_size));
     }
     SECTION("missing \"file_type\"") {
@@ -210,7 +218,7 @@ TEST_CASE("Known artifact description contains incorrect value for \"data\"",
             {"type", "KNOWN"}, {"data", {{"id", "known_input"}, {"size", 15}}}};
 
         CHECK(not ArtifactDescription::FromJson(
-            GetHashType(Compatibility::IsCompatible()),
+            GetHashType(ProtocolTraits::Instance().IsCompatible()),
             known_art_missing_file_type));
     }
 }
@@ -220,10 +228,12 @@ TEST_CASE("Action artifact description contains incorrect value for \"data\"",
     nlohmann::json const action_art_missing_id = {
         {"type", "ACTION"}, {"data", {{"path", "output/path"}}}};
     CHECK(not ArtifactDescription::FromJson(
-        GetHashType(Compatibility::IsCompatible()), action_art_missing_id));
+        GetHashType(ProtocolTraits::Instance().IsCompatible()),
+        action_art_missing_id));
 
     nlohmann::json const action_art_missing_path = {
         {"type", "ACTION"}, {"data", {{"id", "action_id"}}}};
     CHECK(not ArtifactDescription::FromJson(
-        GetHashType(Compatibility::IsCompatible()), action_art_missing_path));
+        GetHashType(ProtocolTraits::Instance().IsCompatible()),
+        action_art_missing_path));
 }
diff --git a/test/buildtool/execution_api/bazel/TARGETS b/test/buildtool/execution_api/bazel/TARGETS
index 192a6182..64e52ad6 100644
--- a/test/buildtool/execution_api/bazel/TARGETS
+++ b/test/buildtool/execution_api/bazel/TARGETS
@@ -9,6 +9,7 @@
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
     , ["@", "src", "src/buildtool/common", "bazel_digest_factory"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
     , ["@", "src", "src/buildtool/execution_api/bazel_msg", "bazel_msg"]
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel_network"]
@@ -29,12 +30,12 @@
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
     , ["@", "src", "src/buildtool/common", "bazel_digest_factory"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel_network"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/file_system", "object_type"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "bazel"]
   }
@@ -49,12 +50,12 @@
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
     , ["@", "src", "src/buildtool/common", "bazel_digest_factory"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/execution_api/bazel_msg", "bazel_msg"]
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel_network"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/file_system", "object_type"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "bazel"]
   }
@@ -69,8 +70,8 @@
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
     , ["@", "src", "src/buildtool/common", "bazel_digest_factory"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     , ["@", "src", "src/buildtool/execution_api/bazel_msg", "bazel_msg"]
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel_network"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
@@ -96,8 +97,8 @@
     , ["@", "src", "src/buildtool/file_system", "object_type"]
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     , ["@", "src", "src/buildtool/execution_api/common", "common"]
     , [ "@"
       , "src"
@@ -121,7 +122,7 @@
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel"]
     , ["buildtool/execution_api/common", "api_test"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "bazel"]
   }
diff --git a/test/buildtool/execution_api/bazel/bazel_api.test.cpp b/test/buildtool/execution_api/bazel/bazel_api.test.cpp
index bced4a87..5dc4198d 100644
--- a/test/buildtool/execution_api/bazel/bazel_api.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_api.test.cpp
@@ -18,8 +18,8 @@
 #include <string>
 
 #include "catch2/catch_test_macros.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "test/buildtool/execution_api/common/api_test.hpp"
@@ -64,7 +64,7 @@ TEST_CASE("BazelAPI: No input, no output", "[execution_api]") {
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -80,7 +80,7 @@ TEST_CASE("BazelAPI: No input, create output", "[execution_api]") {
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -96,7 +96,7 @@ TEST_CASE("BazelAPI: One input copied to output", "[execution_api]") {
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -112,7 +112,7 @@ TEST_CASE("BazelAPI: Non-zero exit code, create output", "[execution_api]") {
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -129,7 +129,7 @@ TEST_CASE("BazelAPI: Retrieve two identical trees to path", "[execution_api]") {
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -147,7 +147,7 @@ TEST_CASE("BazelAPI: Retrieve file and symlink with same content to path",
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -164,7 +164,7 @@ TEST_CASE("BazelAPI: Retrieve mixed blobs and trees", "[execution_api]") {
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -181,7 +181,7 @@ TEST_CASE("BazelAPI: Create directory prior to execution", "[execution_api]") {
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
diff --git a/test/buildtool/execution_api/bazel/bazel_cas_client.test.cpp b/test/buildtool/execution_api/bazel/bazel_cas_client.test.cpp
index e4772f7d..4be61071 100644
--- a/test/buildtool/execution_api/bazel/bazel_cas_client.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_cas_client.test.cpp
@@ -21,6 +21,7 @@
 #include "catch2/catch_test_macros.hpp"
 #include "gsl/gsl"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/bazel_msg/bazel_blob_container.hpp"
@@ -49,9 +50,10 @@ TEST_CASE("Bazel internals: CAS Client", "[execution_api]") {
 
     SECTION("Valid digest and blob") {
         // digest of "test"
-        HashFunction const hash_function{Compatibility::IsCompatible()
-                                             ? HashFunction::Type::PlainSHA256
-                                             : HashFunction::Type::GitSHA1};
+        HashFunction const hash_function{
+            ProtocolTraits::Instance().IsCompatible()
+                ? HashFunction::Type::PlainSHA256
+                : HashFunction::Type::GitSHA1};
         auto digest = BazelDigestFactory::HashDataAs<ObjectType::File>(
             hash_function, content);
 
diff --git a/test/buildtool/execution_api/bazel/bazel_execution_client.test.cpp b/test/buildtool/execution_api/bazel/bazel_execution_client.test.cpp
index c354316c..a0f77066 100644
--- a/test/buildtool/execution_api/bazel/bazel_execution_client.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_execution_client.test.cpp
@@ -18,8 +18,8 @@
 
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
@@ -31,7 +31,7 @@ TEST_CASE("Bazel internals: Execution Client", "[execution_api]") {
     std::string instance_name{"remote-execution"};
     std::string content("test");
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -115,7 +115,7 @@ TEST_CASE("Bazel internals: Execution Client using env variables",
     std::string instance_name{"remote-execution"};
     std::string content("contents of env variable");
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
diff --git a/test/buildtool/execution_api/bazel/bazel_msg_factory.test.cpp b/test/buildtool/execution_api/bazel/bazel_msg_factory.test.cpp
index 40dec8da..8ec074f9 100644
--- a/test/buildtool/execution_api/bazel/bazel_msg_factory.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_msg_factory.test.cpp
@@ -23,7 +23,7 @@
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/common/artifact_blob_container.hpp"
 #include "src/buildtool/file_system/file_system_manager.hpp"
@@ -62,7 +62,7 @@ TEST_CASE("Bazel internals: MessageFactory", "[execution_api]") {
     std::filesystem::path link = subdir1 / "link";
     REQUIRE(FileSystemManager::CreateSymlink("file1", link));
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
diff --git a/test/buildtool/execution_api/bazel/bazel_network.test.cpp b/test/buildtool/execution_api/bazel/bazel_network.test.cpp
index 01c5aea9..c69e7619 100644
--- a/test/buildtool/execution_api/bazel/bazel_network.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_network.test.cpp
@@ -22,8 +22,8 @@
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/auth/authentication.hpp"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/bazel_msg/bazel_blob_container.hpp"
 #include "src/buildtool/execution_api/remote/bazel/bazel_execution_client.hpp"
@@ -46,7 +46,7 @@ TEST_CASE("Bazel network: write/read blobs", "[execution_api]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -97,7 +97,7 @@ TEST_CASE("Bazel network: write/read blobs", "[execution_api]") {
 }
 
 TEST_CASE("Bazel network: read blobs with unknown size", "[execution_api]") {
-    if (Compatibility::IsCompatible()) {
+    if (ProtocolTraits::Instance().IsCompatible()) {
         // only supported in native mode
         return;
     }
@@ -113,7 +113,7 @@ TEST_CASE("Bazel network: read blobs with unknown size", "[execution_api]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
diff --git a/test/buildtool/execution_api/bazel/bytestream_client.test.cpp b/test/buildtool/execution_api/bazel/bytestream_client.test.cpp
index 731073e5..1956a6a3 100644
--- a/test/buildtool/execution_api/bazel/bytestream_client.test.cpp
+++ b/test/buildtool/execution_api/bazel/bytestream_client.test.cpp
@@ -21,7 +21,7 @@
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/auth/authentication.hpp"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/bazel_msg/bazel_blob_container.hpp"
 #include "src/buildtool/execution_api/common/execution_common.hpp"
@@ -45,7 +45,7 @@ TEST_CASE("ByteStream Client: Transfer single blob", "[execution_api]") {
                                    &*auth_config};
     auto uuid = CreateUUIDVersion4(*CreateProcessUniqueId());
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -152,7 +152,7 @@ TEST_CASE("ByteStream Client: Transfer multiple blobs", "[execution_api]") {
                                    &*auth_config};
     auto uuid = CreateUUIDVersion4(*CreateProcessUniqueId());
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
diff --git a/test/buildtool/execution_api/common/TARGETS b/test/buildtool/execution_api/common/TARGETS
index 08ee9c39..f58bb4f0 100644
--- a/test/buildtool/execution_api/common/TARGETS
+++ b/test/buildtool/execution_api/common/TARGETS
@@ -5,14 +5,14 @@
   , "deps":
     [ ["@", "catch2", "", "catch2"]
     , ["@", "src", "src/buildtool/common", "artifact_description"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
+    , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
     , ["@", "src", "src/buildtool/execution_api/common", "common"]
     , ["@", "src", "src/buildtool/execution_api/local", "config"]
     , ["@", "src", "src/buildtool/file_system", "file_system_manager"]
     , ["@", "src", "src/buildtool/logging", "log_level"]
     , ["@", "src", "src/buildtool/logging", "logging"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
-    , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "common"]
   }
diff --git a/test/buildtool/execution_api/common/api_test.hpp b/test/buildtool/execution_api/common/api_test.hpp
index 382760f6..3c4052b3 100644
--- a/test/buildtool/execution_api/common/api_test.hpp
+++ b/test/buildtool/execution_api/common/api_test.hpp
@@ -25,7 +25,7 @@
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/common/execution_action.hpp"
 #include "src/buildtool/execution_api/common/execution_api.hpp"
@@ -140,7 +140,7 @@ using ExecProps = std::map<std::string, std::string>;
     bool is_hermetic = false) {
     std::string test_content("test");
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -224,7 +224,7 @@ using ExecProps = std::map<std::string, std::string>;
     bool is_hermetic = false) {
     std::string test_content("test");
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -315,7 +315,7 @@ using ExecProps = std::map<std::string, std::string>;
     ExecProps const& props) {
     std::string test_content("test");
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
diff --git a/test/buildtool/execution_api/execution_service/TARGETS b/test/buildtool/execution_api/execution_service/TARGETS
index a2c1e9dd..776f0f2b 100644
--- a/test/buildtool/execution_api/execution_service/TARGETS
+++ b/test/buildtool/execution_api/execution_service/TARGETS
@@ -17,6 +17,7 @@
     , ["@", "src", "src/buildtool/file_system", "object_type"]
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "bazel_digest_factory"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/storage", "config"]
     , ["@", "src", "src/buildtool/storage", "storage"]
     , ["@", "gsl", "", "gsl"]
diff --git a/test/buildtool/execution_api/execution_service/cas_server.test.cpp b/test/buildtool/execution_api/execution_service/cas_server.test.cpp
index ca88b17b..8d68d9cb 100644
--- a/test/buildtool/execution_api/execution_service/cas_server.test.cpp
+++ b/test/buildtool/execution_api/execution_service/cas_server.test.cpp
@@ -20,6 +20,7 @@
 #include "gsl/gsl"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/execution_api/local/config.hpp"
 #include "src/buildtool/execution_api/local/context.hpp"
 #include "src/buildtool/file_system/git_repo.hpp"
@@ -47,7 +48,7 @@ namespace {
 
 TEST_CASE("CAS Service: upload incomplete tree", "[execution_service]") {
     // For compatible mode tree invariants aren't checked.
-    if (Compatibility::IsCompatible()) {
+    if (ProtocolTraits::Instance().IsCompatible()) {
         return;
     }
 
diff --git a/test/buildtool/execution_engine/executor/TARGETS b/test/buildtool/execution_engine/executor/TARGETS
index a3176e91..74247e49 100644
--- a/test/buildtool/execution_engine/executor/TARGETS
+++ b/test/buildtool/execution_engine/executor/TARGETS
@@ -7,6 +7,7 @@
     , ["@", "src", "src/buildtool/common", "artifact_description"]
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/execution_api/common", "common"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/execution_api/remote", "context"]
@@ -16,7 +17,6 @@
     , ["@", "src", "src/buildtool/file_system", "file_system_manager"]
     , ["@", "src", "src/buildtool/progress_reporting", "progress"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     , ["@", "catch2", "", "catch2"]
     , ["@", "gsl", "", "gsl"]
     , ["utils", "test_api_bundle"]
@@ -34,6 +34,7 @@
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
     , ["@", "src", "src/buildtool/common", "config"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
     , ["@", "src", "src/buildtool/execution_api/common", "common"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
@@ -43,7 +44,6 @@
     , ["@", "src", "src/buildtool/execution_engine/executor", "executor"]
     , ["@", "src", "src/buildtool/progress_reporting", "progress"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     , ["", "catch-main"]
     , ["@", "catch2", "", "catch2"]
     , ["@", "gsl", "", "gsl"]
@@ -84,13 +84,13 @@
     [ "executor_api_tests"
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "config"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/execution_engine/executor", "executor"]
     , ["@", "src", "src/buildtool/progress_reporting", "progress"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     , ["utils", "catch-main-remote-execution"]
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
diff --git a/test/buildtool/execution_engine/executor/executor.test.cpp b/test/buildtool/execution_engine/executor/executor.test.cpp
index ee950ec0..d0533f9c 100644
--- a/test/buildtool/execution_engine/executor/executor.test.cpp
+++ b/test/buildtool/execution_engine/executor/executor.test.cpp
@@ -29,9 +29,9 @@
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/repository_config.hpp"
 #include "src/buildtool/common/statistics.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/common/execution_api.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
@@ -64,7 +64,7 @@ struct TestApiConfig {
 };
 
 static auto NamedDigest(std::string const& str) -> ArtifactDigest {
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
     return ArtifactDigestFactory::HashDataAs<ObjectType::File>(hash_function,
@@ -305,7 +305,7 @@ TEST_CASE("Executor: Process artifact", "[executor]") {
     DependencyGraph g;
     auto [config, repo_config] = CreateTest(&g, workspace_path);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -383,7 +383,7 @@ TEST_CASE("Executor: Process action", "[executor]") {
     DependencyGraph g;
     auto [config, repo_config] = CreateTest(&g, workspace_path);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
diff --git a/test/buildtool/execution_engine/executor/executor_api.test.hpp b/test/buildtool/execution_engine/executor/executor_api.test.hpp
index c898d9e8..570c6e39 100644
--- a/test/buildtool/execution_engine/executor/executor_api.test.hpp
+++ b/test/buildtool/execution_engine/executor/executor_api.test.hpp
@@ -27,10 +27,10 @@
 #include "src/buildtool/common/artifact.hpp"
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
 #include "src/buildtool/common/repository_config.hpp"
 #include "src/buildtool/common/statistics.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/common/execution_api.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
@@ -56,7 +56,7 @@ static inline void RunBlobUpload(RepositoryConfig* repo_config,
                                  ApiFactory const& factory) {
     SetupConfig(repo_config);
     auto api = factory();
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -144,7 +144,7 @@ static inline void RunHelloWorldCompilation(
                                        .retry_config = &retry_config,
                                        .exec_config = &*remote_config};
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -279,7 +279,7 @@ static inline void RunGreeterCompilation(
                                        .retry_config = &retry_config,
                                        .exec_config = &*remote_config};
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -420,7 +420,7 @@ static inline void TestUploadAndDownloadTrees(
         env.emplace("PATH", "/bin:/usr/bin");
     }
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -576,7 +576,7 @@ static inline void TestRetrieveOutputDirectories(
     int /*expected_cached*/ = 0) {
     SetupConfig(repo_config);
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
diff --git a/test/buildtool/execution_engine/executor/executor_api_remote_bazel.test.cpp b/test/buildtool/execution_engine/executor/executor_api_remote_bazel.test.cpp
index 0e068ea9..fd2167a7 100644
--- a/test/buildtool/execution_engine/executor/executor_api_remote_bazel.test.cpp
+++ b/test/buildtool/execution_engine/executor/executor_api_remote_bazel.test.cpp
@@ -15,10 +15,10 @@
 #include <optional>
 
 #include "catch2/catch_test_macros.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
 #include "src/buildtool/common/repository_config.hpp"
 #include "src/buildtool/common/statistics.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/remote/bazel/bazel_api.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
@@ -41,7 +41,7 @@ TEST_CASE("Executor<BazelApi>: Upload blob", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -72,7 +72,7 @@ TEST_CASE("Executor<BazelApi>: Compile hello world", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -110,7 +110,7 @@ TEST_CASE("Executor<BazelApi>: Compile greeter", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -148,7 +148,7 @@ TEST_CASE("Executor<BazelApi>: Upload and download trees", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
@@ -186,7 +186,7 @@ TEST_CASE("Executor<BazelApi>: Retrieve output directories", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{Compatibility::IsCompatible()
+    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
                                          ? HashFunction::Type::PlainSHA256
                                          : HashFunction::Type::GitSHA1};
 
diff --git a/test/buildtool/execution_engine/traverser/TARGETS b/test/buildtool/execution_engine/traverser/TARGETS
index bdd7c4cc..7228b0af 100644
--- a/test/buildtool/execution_engine/traverser/TARGETS
+++ b/test/buildtool/execution_engine/traverser/TARGETS
@@ -7,11 +7,11 @@
     , ["", "catch-main"]
     , ["utils", "container_matchers"]
     , ["@", "src", "src/buildtool/common", "common"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common", "artifact_description"]
     , ["@", "src", "src/buildtool/execution_engine/dag", "dag"]
     , ["@", "src", "src/buildtool/execution_engine/traverser", "traverser"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     ]
   , "stage": ["test", "buildtool", "execution_engine", "traverser"]
   }
diff --git a/test/buildtool/execution_engine/traverser/traverser.test.cpp b/test/buildtool/execution_engine/traverser/traverser.test.cpp
index 70ab2465..7b2e6293 100644
--- a/test/buildtool/execution_engine/traverser/traverser.test.cpp
+++ b/test/buildtool/execution_engine/traverser/traverser.test.cpp
@@ -24,7 +24,7 @@
 
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/common/artifact_description.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_engine/dag/dag.hpp"
 #include "test/utils/container_matchers.hpp"
@@ -184,7 +184,7 @@ class TestProject {
         auto inputs_desc = ActionDescription::inputs_t{};
         if (not inputs.empty()) {
             command.emplace_back("FROM");
-            auto const hash_type = Compatibility::IsCompatible()
+            auto const hash_type = ProtocolTraits::Instance().IsCompatible()
                                        ? HashFunction::Type::PlainSHA256
                                        : HashFunction::Type::GitSHA1;
             for (auto const& input_desc : inputs) {
diff --git a/test/buildtool/file_system/TARGETS b/test/buildtool/file_system/TARGETS
index a7342221..eda8f376 100644
--- a/test/buildtool/file_system/TARGETS
+++ b/test/buildtool/file_system/TARGETS
@@ -62,6 +62,7 @@
     , ["@", "src", "src/buildtool/common", "artifact_description"]
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
     , ["@", "src", "src/buildtool/file_system", "file_root"]
     , ["@", "src", "src/buildtool/file_system", "file_system_manager"]
diff --git a/test/buildtool/file_system/file_root.test.cpp b/test/buildtool/file_system/file_root.test.cpp
index f709aa7a..1e7b9e7b 100644
--- a/test/buildtool/file_system/file_root.test.cpp
+++ b/test/buildtool/file_system/file_root.test.cpp
@@ -25,6 +25,7 @@
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/file_system/file_system_manager.hpp"
 #include "test/utils/container_matchers.hpp"
@@ -412,7 +413,7 @@ static void CheckGitRoot(bool ignore_special) noexcept {
 
     auto const foo = root->ToArtifactDescription("baz/foo", "repo");
     REQUIRE(foo);
-    if (Compatibility::IsCompatible()) {
+    if (ProtocolTraits::Instance().IsCompatible()) {
         auto const digest =
             ArtifactDigestFactory::Create(HashFunction::Type::PlainSHA256,
                                           kFooIdSha256,
@@ -435,7 +436,7 @@ static void CheckGitRoot(bool ignore_special) noexcept {
 
     auto const bar = root->ToArtifactDescription("baz/bar", "repo");
     REQUIRE(bar);
-    if (Compatibility::IsCompatible()) {
+    if (ProtocolTraits::Instance().IsCompatible()) {
         auto const digest =
             ArtifactDigestFactory::Create(HashFunction::Type::PlainSHA256,
                                           kBarIdSha256,
diff --git a/test/buildtool/graph_traverser/TARGETS b/test/buildtool/graph_traverser/TARGETS
index fcf2da20..d9dd7af6 100644
--- a/test/buildtool/graph_traverser/TARGETS
+++ b/test/buildtool/graph_traverser/TARGETS
@@ -7,6 +7,7 @@
     , ["@", "json", "", "json"]
     , ["@", "src", "src/buildtool/auth", "auth"]
     , ["@", "src", "src/buildtool/common", "common"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
     , ["@", "src", "src/buildtool/execution_api/local", "config"]
     , ["@", "src", "src/buildtool/execution_api/local", "context"]
@@ -39,6 +40,7 @@
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/storage", "config"]
     , ["@", "src", "src/buildtool/storage", "storage"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     ]
   , "stage": ["test", "buildtool", "graph_traverser"]
   }
@@ -56,6 +58,7 @@
     , ["@", "src", "src/buildtool/storage", "storage"]
     , ["@", "src", "src/buildtool/storage", "config"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     ]
   , "stage": ["test", "buildtool", "graph_traverser"]
   }
diff --git a/test/buildtool/graph_traverser/graph_traverser.test.hpp b/test/buildtool/graph_traverser/graph_traverser.test.hpp
index 28ec44e0..666b905f 100644
--- a/test/buildtool/graph_traverser/graph_traverser.test.hpp
+++ b/test/buildtool/graph_traverser/graph_traverser.test.hpp
@@ -29,6 +29,7 @@
 #include "gsl/gsl"
 #include "nlohmann/json.hpp"
 #include "src/buildtool/auth/authentication.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
 #include "src/buildtool/common/statistics.hpp"
 #include "src/buildtool/execution_api/common/api_bundle.hpp"
@@ -127,7 +128,7 @@ class TestProject {
         CommandLineArguments clargs{gtargs};
         clargs.artifacts = entry_points;
         auto const comp_graph = root_dir_ / "graph_description_compatible";
-        if (Compatibility::IsCompatible() and
+        if (ProtocolTraits::Instance().IsCompatible() and
             FileSystemManager::Exists(comp_graph)) {
             clargs.graph_description = comp_graph;
         }
diff --git a/test/buildtool/graph_traverser/graph_traverser_remote.test.cpp b/test/buildtool/graph_traverser/graph_traverser_remote.test.cpp
index d92b9ef9..bf3dfe02 100644
--- a/test/buildtool/graph_traverser/graph_traverser_remote.test.cpp
+++ b/test/buildtool/graph_traverser/graph_traverser_remote.test.cpp
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "catch2/catch_test_macros.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "src/buildtool/storage/config.hpp"
@@ -34,7 +35,7 @@
 
     StorageConfig::Builder builder;
     auto config = builder.SetBuildRoot(cache_dir)
-                      .SetHashType(Compatibility::IsCompatible()
+                      .SetHashType(ProtocolTraits::Instance().IsCompatible()
                                        ? HashFunction::Type::PlainSHA256
                                        : HashFunction::Type::GitSHA1)
                       .SetRemoteExecutionArgs(remote_config.remote_address,
diff --git a/test/buildtool/storage/TARGETS b/test/buildtool/storage/TARGETS
index 5eeafa9a..7b58b109 100644
--- a/test/buildtool/storage/TARGETS
+++ b/test/buildtool/storage/TARGETS
@@ -58,6 +58,7 @@
     , ["@", "src", "src/buildtool/storage", "config"]
     , ["utils", "test_storage_config"]
     , ["@", "src", "src/buildtool/common", "bazel_types"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["utils", "large_object_utils"]
     , ["@", "src", "src/utils/cpp", "tmp_dir"]
     , [ "@"
@@ -65,7 +66,6 @@
       , "src/buildtool/execution_api/bazel_msg"
       , "bazel_msg_factory"
       ]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
     ]
   , "stage": ["test", "buildtool", "storage"]
   }
diff --git a/test/buildtool/storage/large_object_cas.test.cpp b/test/buildtool/storage/large_object_cas.test.cpp
index f0644694..cbc92038 100644
--- a/test/buildtool/storage/large_object_cas.test.cpp
+++ b/test/buildtool/storage/large_object_cas.test.cpp
@@ -28,7 +28,7 @@
 
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/common/bazel_types.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/execution_api/bazel_msg/bazel_msg_factory.hpp"
 #include "src/buildtool/file_system/file_system_manager.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
@@ -405,7 +405,7 @@ static void TestExternal(StorageConfig const& storage_config,
             REQUIRE(FileSystemManager::IsFile(path));
         }
 
-        if (kIsTree and not Compatibility::IsCompatible()) {
+        if (kIsTree and not ProtocolTraits::Instance().IsCompatible()) {
             // Tree invariants check is omitted in compatible mode.
             SECTION("Tree invariants check fails") {
                 // Check splice fails due to the tree invariants check.
@@ -606,7 +606,7 @@ TEST_CASE("LargeObjectCAS: uplink nested large objects", "[storage]") {
 
     // However, in native mode they might be reconstructed on request because
     // their entries are in the latest generation:
-    if (not Compatibility::IsCompatible()) {
+    if (not ProtocolTraits::Instance().IsCompatible()) {
         auto split_nested_tree_2 = latest.CAS().SplitTree(*nested_tree_digest);
         REQUIRE(split_nested_tree_2);
 
@@ -720,7 +720,7 @@ auto Tree::StoreRaw(LocalCAS<kDefaultDoGlobalUplink> const& cas,
         return cas.StoreBlob(content);
     };
 
-    return Compatibility::IsCompatible()
+    return ProtocolTraits::Instance().IsCompatible()
                ? BazelMsgFactory::CreateDirectoryDigestFromLocalTree(
                      directory, store_blob, store_tree, store_symlink)
                : BazelMsgFactory::CreateGitTreeDigestFromLocalTree(
diff --git a/test/utils/TARGETS b/test/utils/TARGETS
index 9daecce8..d0a427a6 100644
--- a/test/utils/TARGETS
+++ b/test/utils/TARGETS
@@ -38,7 +38,7 @@
   , "hdrs": ["test_env.hpp"]
   , "deps":
     [ "log_config"
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/auth", "auth"]
     ]
   , "stage": ["test", "utils"]
@@ -54,6 +54,7 @@
     , ["@", "src", "src/buildtool/storage", "config"]
     , ["@", "src", "src/utils/cpp", "tmp_dir"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     ]
   , "stage": ["test", "utils"]
   }
@@ -134,7 +135,7 @@
     , ["@", "src", "src/buildtool/logging", "logging"]
     , ["@", "src", "src/buildtool/storage", "storage"]
     , ["@", "src", "src/buildtool/file_system", "file_system_manager"]
-    , ["@", "src", "src/buildtool/compatibility", "compatibility"]
+    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , "shell_quoting"
     , "log_config"
     , "test_env"
diff --git a/test/utils/hermeticity/test_storage_config.hpp b/test/utils/hermeticity/test_storage_config.hpp
index 4bcbc1be..4820782f 100644
--- a/test/utils/hermeticity/test_storage_config.hpp
+++ b/test/utils/hermeticity/test_storage_config.hpp
@@ -21,6 +21,7 @@
 #include <utility>  //std::move
 
 #include "gsl/gsl"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/logging/log_level.hpp"
 #include "src/buildtool/logging/logger.hpp"
@@ -53,7 +54,7 @@ class TestStorageConfig final {
 
         StorageConfig::Builder builder;
         auto config = builder.SetBuildRoot(temp_dir->GetPath())
-                          .SetHashType(Compatibility::IsCompatible()
+                          .SetHashType(ProtocolTraits::Instance().IsCompatible()
                                            ? HashFunction::Type::PlainSHA256
                                            : HashFunction::Type::GitSHA1)
                           .Build();
diff --git a/test/utils/serve_service/main-serve.cpp b/test/utils/serve_service/main-serve.cpp
index 5a08eb89..2868e354 100644
--- a/test/utils/serve_service/main-serve.cpp
+++ b/test/utils/serve_service/main-serve.cpp
@@ -23,7 +23,7 @@
 
 #include "catch2/catch_session.hpp"
 #include "catch2/catch_test_macros.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "src/buildtool/file_system/file_system_manager.hpp"
 #include "src/buildtool/logging/log_level.hpp"
diff --git a/test/utils/test_env.hpp b/test/utils/test_env.hpp
index 30eba26c..fc6ac739 100644
--- a/test/utils/test_env.hpp
+++ b/test/utils/test_env.hpp
@@ -23,7 +23,7 @@
 #include <string>
 
 #include "src/buildtool/auth/authentication.hpp"
-#include "src/buildtool/compatibility/compatibility.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "test/utils/logging/log_config.hpp"
 
 [[nodiscard]] static inline auto ReadPlatformPropertiesFromEnv()
@@ -43,7 +43,7 @@
 static inline void ReadCompatibilityFromEnv() {
     auto* compatible = std::getenv("COMPATIBLE");
     if (compatible != nullptr) {
-        Compatibility::SetCompatible();
+        ProtocolTraits::Instance().SetCompatible();
     }
 }