diff --git a/CMakeLists.txt b/CMakeLists.txt
index 33394953e8..56f588859b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -316,6 +316,13 @@ if(ENABLE_COVERAGE_TESTING)
     set(CMAKE_CXX_FLAGS "--coverage ${CMAKE_CXX_FLAGS}")
 endif()
 
+# Static libraries do not link, so a library's objects need not wait for its dependency
+# libraries to finish compiling, only for their generated sources. Without this the Makefile
+# generator builds target-by-target: nothing in graphene_chain starts until fc/protocol are
+# archived, and no plugin starts until database.cpp (the longest TU) finishes on one core.
+# Cold `make -j8 vizd cli_wallet` on an 8-core laptop: 805 s -> 305 s wall, ~2.4 -> ~4.8 cores busy.
+set(CMAKE_OPTIMIZE_DEPENDENCIES ON)
+
 add_subdirectory(thirdparty)
 add_subdirectory(libraries)
 add_subdirectory(plugins)
diff --git a/libraries/chain/CMakeLists.txt b/libraries/chain/CMakeLists.txt
index f7d9b824f4..d962cab2c1 100644
--- a/libraries/chain/CMakeLists.txt
+++ b/libraries/chain/CMakeLists.txt
@@ -33,9 +33,6 @@ set_source_files_properties("${hardfork_hpp_out}" PROPERTIES GENERATED TRUE)
 # Include the binary include dir
 include_directories("${CMAKE_CURRENT_BINARY_DIR}/include")
 
-# Variable used below in add_library
-set(hardfork_hpp_file "${hardfork_hpp_out}")
-
 ## SORT .cpp by most likely to change / break compile
 
 add_library(graphene_chain ${VIZ_LIBRARY_TYPE}
@@ -104,10 +101,12 @@ add_library(graphene_chain ${VIZ_LIBRARY_TYPE}
             include/graphene/chain/paid_subscription_objects.hpp
             include/graphene/chain/pm_objects.hpp
 
-            ${hardfork_hpp_file}
             )
 
-add_dependencies(graphene_chain graphene_protocol graphene_utilities build_hardfork_hpp)
+# Only the generated header is a real build-order dependency. Library-to-library order comes
+# from target_link_libraries; an explicit add_dependencies here would defeat
+# CMAKE_OPTIMIZE_DEPENDENCIES and make every chain TU wait for protocol to finish archiving.
+add_dependencies(graphene_chain build_hardfork_hpp)
 target_link_libraries(graphene_chain graphene_protocol graphene_utilities fc chainbase appbase ${PATCH_MERGE_LIB})
 target_include_directories(graphene_chain PUBLIC "${CMAKE_CURRENT_BINARY_DIR}/include" "${CMAKE_CURRENT_SOURCE_DIR}/include" "${CMAKE_CURRENT_SOURCE_DIR}/../../")
 
diff --git a/tests/consensus_sim/CMakeLists.txt b/tests/consensus_sim/CMakeLists.txt
index e286941967..9472e8d95d 100644
--- a/tests/consensus_sim/CMakeLists.txt
+++ b/tests/consensus_sim/CMakeLists.txt
@@ -67,6 +67,7 @@ set(SCENARIO_SOURCES
     scenarios/test_routable_endpoint.cpp
     scenarios/test_p2p_slot_scale.cpp
     scenarios/test_db_invariants.cpp
+    scenarios/test_operation_variant.cpp
 )
 
 # These scenarios require an actual HF14 activation and never soft-skip.
diff --git a/tests/consensus_sim/scenarios/test_operation_variant.cpp b/tests/consensus_sim/scenarios/test_operation_variant.cpp
new file mode 100644
index 0000000000..1e07cdc4f3
--- /dev/null
+++ b/tests/consensus_sim/scenarios/test_operation_variant.cpp
@@ -0,0 +1,59 @@
+// Contract of the `operation` static_variant: every alternative round-trips through the raw
+// and JSON serializers under its own tag, tags are what the type list says they are, and an
+// out-of-range tag is rejected instead of dispatching into garbage. The variant index is the
+// consensus op-id, so this pins the dispatch machinery itself, not any one operation.
+
+#include <boost/test/unit_test.hpp>
+
+#include <graphene/protocol/operations.hpp>
+#include <fc/io/raw.hpp>
+
+using namespace graphene::protocol;
+
+BOOST_AUTO_TEST_SUITE(operation_variant)
+
+BOOST_AUTO_TEST_CASE(every_alternative_round_trips_under_its_tag) {
+    for (int i = 0; i < operation::count(); ++i) {
+        operation op;
+        op.set_which(i);
+        BOOST_REQUIRE_EQUAL(op.which(), i);
+
+        auto bytes = fc::raw::pack(op);
+        BOOST_CHECK_EQUAL(fc::raw::unpack<operation>(bytes).which(), i);
+
+        fc::variant v;
+        fc::to_variant(op, v);
+        operation from_json;
+        fc::from_variant(v, from_json);
+        BOOST_CHECK_EQUAL(from_json.which(), i);
+
+        operation copied(op);
+        operation moved(std::move(copied));
+        BOOST_CHECK_EQUAL(moved.which(), i);
+        operation assigned;
+        assigned = op;
+        BOOST_CHECK_EQUAL(assigned.which(), i);
+    }
+}
+
+BOOST_AUTO_TEST_CASE(tags_follow_the_type_list) {
+    BOOST_CHECK_EQUAL(int(operation::tag<vote_operation>::value), 0);
+    BOOST_CHECK_EQUAL(int(operation::tag<transfer_operation>::value), 2);
+    BOOST_CHECK_EQUAL(int(operation::tag<validator_equivocation_operation>::value), operation::count() - 1);
+
+    operation op = transfer_operation();
+    BOOST_CHECK_EQUAL(op.which(), int(operation::tag<transfer_operation>::value));
+    op.get<transfer_operation>().memo = "x";
+    BOOST_CHECK_EQUAL(op.get<transfer_operation>().memo, "x");
+    BOOST_CHECK_THROW(op.get<vote_operation>(), fc::assert_exception);
+}
+
+BOOST_AUTO_TEST_CASE(out_of_range_tag_is_rejected) {
+    operation op;
+    BOOST_CHECK_THROW(op.set_which(operation::count()), fc::exception);
+
+    auto bytes = fc::raw::pack(fc::unsigned_int(operation::count() + 7));
+    BOOST_CHECK_THROW(fc::raw::unpack<operation>(bytes), fc::exception);
+}
+
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/thirdparty/fc b/thirdparty/fc
index 679e89e9cd..7889e2f73a 160000
--- a/thirdparty/fc
+++ b/thirdparty/fc
@@ -1 +1 @@
-Subproject commit 679e89e9cd503b97b6b1d7e436418408c0f9b35a
+Subproject commit 7889e2f73a3918b3855efad69869ec08952a3140