diff --git a/circuits/cpp/src/aztec3/circuits/abis/.test.cpp b/circuits/cpp/src/aztec3/circuits/abis/.test.cpp
index 0bee851c6627..e18331ea8eaa 100644
--- a/circuits/cpp/src/aztec3/circuits/abis/.test.cpp
+++ b/circuits/cpp/src/aztec3/circuits/abis/.test.cpp
@@ -9,7 +9,7 @@
 
 namespace {
 // Builder
-using Builder = UltraCircuitBuilder;
+using Builder = CircuitSimulatorBN254;
 
 // Types
 using CT = aztec3::utils::types::CircuitTypes<Builder>;
diff --git a/circuits/cpp/src/aztec3/circuits/apps/.test.cpp b/circuits/cpp/src/aztec3/circuits/apps/.test.cpp
index ab4ca379df42..c4ba2b5dab37 100644
--- a/circuits/cpp/src/aztec3/circuits/apps/.test.cpp
+++ b/circuits/cpp/src/aztec3/circuits/apps/.test.cpp
@@ -25,7 +25,7 @@
 
 namespace {
 // Builder
-using C = UltraCircuitBuilder;
+using C = CircuitSimulatorBN254;
 
 // Types
 using CT = aztec3::utils::types::CircuitTypes<C>;
diff --git a/circuits/cpp/src/aztec3/circuits/apps/test_apps/basic_contract_deployment/init.hpp b/circuits/cpp/src/aztec3/circuits/apps/test_apps/basic_contract_deployment/init.hpp
index 01f6f07bc04c..295b7f425e5a 100644
--- a/circuits/cpp/src/aztec3/circuits/apps/test_apps/basic_contract_deployment/init.hpp
+++ b/circuits/cpp/src/aztec3/circuits/apps/test_apps/basic_contract_deployment/init.hpp
@@ -16,8 +16,8 @@
 namespace aztec3::circuits::apps::test_apps::basic_contract_deployment {
 
 // Builder
-// using C = UltraCircuitBuilder;
-using C = UltraCircuitBuilder;
+// using C = CircuitSimulatorBN254;
+using C = CircuitSimulatorBN254;
 
 // Native and circuit types
 using CT = aztec3::utils::types::CircuitTypes<C>;
diff --git a/circuits/cpp/src/aztec3/circuits/apps/test_apps/escrow/init.hpp b/circuits/cpp/src/aztec3/circuits/apps/test_apps/escrow/init.hpp
index 7b773e8e9c8d..dcca315a7565 100644
--- a/circuits/cpp/src/aztec3/circuits/apps/test_apps/escrow/init.hpp
+++ b/circuits/cpp/src/aztec3/circuits/apps/test_apps/escrow/init.hpp
@@ -18,8 +18,8 @@ namespace aztec3::circuits::apps::test_apps::escrow {
 
 // Builder
 // WORKTODO: this is coupled to the circuit builder in the private kernel.
-using C = UltraCircuitBuilder;
-// using C = UltraCircuitBuilder;
+using C = CircuitSimulatorBN254;
+// using C = CircuitSimulatorBN254;
 
 // Native and circuit types
 using CT = aztec3::utils::types::CircuitTypes<C>;
diff --git a/circuits/cpp/src/aztec3/circuits/apps/test_apps/private_to_private_function_call/init.hpp b/circuits/cpp/src/aztec3/circuits/apps/test_apps/private_to_private_function_call/init.hpp
index 7f2e42a70a47..129156199952 100644
--- a/circuits/cpp/src/aztec3/circuits/apps/test_apps/private_to_private_function_call/init.hpp
+++ b/circuits/cpp/src/aztec3/circuits/apps/test_apps/private_to_private_function_call/init.hpp
@@ -13,7 +13,7 @@
 namespace aztec3::circuits::apps::test_apps::private_to_private_function_call {
 
 // Builder
-using C = UltraCircuitBuilder;
+using C = CircuitSimulatorBN254;
 
 // Native and circuit types
 using CT = aztec3::utils::types::CircuitTypes<C>;
diff --git a/circuits/cpp/src/aztec3/circuits/kernel/private/c_bind.cpp b/circuits/cpp/src/aztec3/circuits/kernel/private/c_bind.cpp
index 43e45c2e2401..e4e1a57bc795 100644
--- a/circuits/cpp/src/aztec3/circuits/kernel/private/c_bind.cpp
+++ b/circuits/cpp/src/aztec3/circuits/kernel/private/c_bind.cpp
@@ -12,7 +12,7 @@
 #include <array>
 
 namespace {
-using Builder = UltraCircuitBuilder;
+using Builder = CircuitSimulatorBN254;
 using NT = aztec3::utils::types::NativeTypes;
 using DummyBuilder = aztec3::utils::DummyCircuitBuilder;
 using aztec3::circuits::abis::PreviousKernelData;
diff --git a/circuits/cpp/src/aztec3/circuits/kernel/private/init.hpp b/circuits/cpp/src/aztec3/circuits/kernel/private/init.hpp
index e37c86057cb1..2e0f22fc45c2 100644
--- a/circuits/cpp/src/aztec3/circuits/kernel/private/init.hpp
+++ b/circuits/cpp/src/aztec3/circuits/kernel/private/init.hpp
@@ -11,8 +11,8 @@
 
 namespace aztec3::circuits::kernel::private_kernel {
 
-using Builder = UltraCircuitBuilder;
-// using Builder = UltraCircuitBuilder;
+using Builder = CircuitSimulatorBN254;
+// using Builder = CircuitSimulatorBN254;
 
 using Aggregator = aztec3::circuits::recursion::Aggregator;
 
diff --git a/circuits/cpp/src/aztec3/circuits/kernel/public/c_bind.cpp b/circuits/cpp/src/aztec3/circuits/kernel/public/c_bind.cpp
index b15896d162d1..2286aad080b6 100644
--- a/circuits/cpp/src/aztec3/circuits/kernel/public/c_bind.cpp
+++ b/circuits/cpp/src/aztec3/circuits/kernel/public/c_bind.cpp
@@ -12,7 +12,7 @@
 #include <barretenberg/barretenberg.hpp>
 
 namespace {
-using Builder = UltraCircuitBuilder;
+using Builder = CircuitSimulatorBN254;
 using NT = aztec3::utils::types::NativeTypes;
 using DummyBuilder = aztec3::utils::DummyCircuitBuilder;
 using aztec3::circuits::abis::KernelCircuitPublicInputs;
diff --git a/circuits/cpp/src/aztec3/circuits/kernel/public/init.hpp b/circuits/cpp/src/aztec3/circuits/kernel/public/init.hpp
index 5a7e60acb778..8b877095910a 100644
--- a/circuits/cpp/src/aztec3/circuits/kernel/public/init.hpp
+++ b/circuits/cpp/src/aztec3/circuits/kernel/public/init.hpp
@@ -10,7 +10,7 @@
 
 namespace aztec3::circuits::kernel::public_kernel {
 
-using Builder = proof_system::UltraCircuitBuilder;
+using Builder = proof_system::CircuitSimulatorBN254;
 
 using Aggregator = aztec3::circuits::recursion::Aggregator;
 
diff --git a/circuits/cpp/src/aztec3/circuits/recursion/init.hpp b/circuits/cpp/src/aztec3/circuits/recursion/init.hpp
index 91a66a2f1753..fdf857dc94b7 100644
--- a/circuits/cpp/src/aztec3/circuits/recursion/init.hpp
+++ b/circuits/cpp/src/aztec3/circuits/recursion/init.hpp
@@ -8,8 +8,8 @@
 
 namespace aztec3::circuits::recursion {
 // Builder
-// using Flavor = proof_system::plonk::flavor::SimulatorBN254;
-using Flavor = proof_system::plonk::flavor::Ultra;
+using Flavor = proof_system::plonk::flavor::SimulatorBN254;
+// using Flavor = proof_system::plonk::flavor::Ultra;
 using Builder = typename Flavor::CircuitBuilder;
 
 // Generic types:
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/base/c_bind.cpp b/circuits/cpp/src/aztec3/circuits/rollup/base/c_bind.cpp
index 0b20a881e403..69c59d27800d 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/base/c_bind.cpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/base/c_bind.cpp
@@ -11,7 +11,7 @@
 #include <barretenberg/barretenberg.hpp>
 
 namespace {
-using Builder = UltraCircuitBuilder;
+using Builder = CircuitSimulatorBN254;
 using NT = aztec3::utils::types::NativeTypes;
 using DummyBuilder = aztec3::utils::DummyCircuitBuilder;
 using aztec3::circuits::abis::BaseOrMergeRollupPublicInputs;
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/root/c_bind.cpp b/circuits/cpp/src/aztec3/circuits/rollup/root/c_bind.cpp
index 9bc1e7b66f7a..e05bbc5bf342 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/root/c_bind.cpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/root/c_bind.cpp
@@ -9,7 +9,7 @@
 #include <barretenberg/barretenberg.hpp>
 
 namespace {
-using Builder = UltraCircuitBuilder;
+using Builder = CircuitSimulatorBN254;
 using NT = aztec3::utils::types::NativeTypes;
 using DummyBuilder = aztec3::utils::DummyCircuitBuilder;
 using aztec3::circuits::rollup::native_root_rollup::root_rollup_circuit;