diff --git a/include/orderbook.hpp b/include/orderbook.hpp
index 92f1714..1788d34 100644
--- a/include/orderbook.hpp
+++ b/include/orderbook.hpp
@@ -151,12 +151,11 @@ void OrderBook<Notification>::addOrder(OrderID id, Type type, Side side, Decimal
 
 template <class Notification>
 void OrderBook<Notification>::processOrder(OrderID id, Type type, Side side, Decimal qty, Decimal price, Flag flag) {
-    static const auto tradeNotification = [this](OrderID mOrderID, OrderID tOrderID, OrderStatus mOrderStatus, OrderStatus tOrderStatus, Decimal qty,
-                                                 Decimal price) {
+    const auto tradeNotification = [this](OrderID mOrderID, OrderID tOrderID, OrderStatus mOrderStatus, OrderStatus tOrderStatus, Decimal qty, Decimal price) {
         this->putTradeNotification(mOrderID, tOrderID, mOrderStatus, tOrderStatus, qty, price);
         this->last_price = price;
     };
-    static const auto postOrderFill = [this](OrderID id) { this->eraseOrder(id); };
+    const auto postOrderFill = [this](OrderID id) { this->eraseOrder(id); };
 
     if (type == Type::Market) {
         if (side == Side::Buy) {
diff --git a/test/determinism_test.cpp b/test/determinism_test.cpp
new file mode 100644
index 0000000..83350b2
--- /dev/null
+++ b/test/determinism_test.cpp
@@ -0,0 +1,277 @@
+#include <gtest/gtest.h>
+
+#include <algorithm>
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "util.cpp"
+
+class DeterminismTest : public ::testing::Test {
+   protected:
+    struct Action {
+        enum class Kind : uint8_t { Add, Cancel, SetMatching };
+        Kind kind;
+        OrderID id = 0;
+        Type type = Type::Limit;
+        Side side = Side::Buy;
+        Decimal qty = Decimal(0, 0);
+        Decimal price = Decimal(0, 0);
+        Flag flag = Flag::None;
+        bool matching = true;
+    };
+
+    static void applyAction(const Action& action, const std::shared_ptr<OrderBook<Notification>>& localOb) {
+        if (action.kind == Action::Kind::SetMatching) {
+            localOb->setMatching(action.matching);
+        } else if (action.kind == Action::Kind::Cancel) {
+            localOb->cancelOrder(action.id);
+        } else {
+            localOb->addOrder(action.id, action.type, action.side, action.qty, action.price, action.flag);
+        }
+    }
+
+    static std::tuple<std::vector<std::string>, std::string, Decimal> runSequence(const std::vector<Action>& actions) {
+        Notification notification;
+        auto localOb = std::make_shared<orderbook::OrderBook<Notification>>(notification);
+        for (const auto& action : actions) {
+            applyAction(action, localOb);
+        }
+        return std::tuple{notification.Strings(), localOb->toString(), localOb->last_price};
+    }
+
+    static bool hasExactReport(const std::vector<std::string>& reports, const std::string& expected) {
+        return std::find(reports.begin(), reports.end(), expected) != reports.end();
+    }
+
+    static bool hasReportContaining(const std::vector<std::string>& reports, const std::string& token) {
+        for (const auto& report : reports) {
+            if (report.find(token) != std::string::npos) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    static bool hasActionKind(const std::vector<Action>& actions, Action::Kind expected) {
+        return std::any_of(actions.begin(), actions.end(), [expected](const Action& action) { return action.kind == expected; });
+    }
+
+    static bool hasType(const std::vector<Action>& actions, Type expected) {
+        return std::any_of(actions.begin(), actions.end(), [expected](const Action& action) { return action.kind == Action::Kind::Add && action.type == expected; });
+    }
+
+    static bool hasSide(const std::vector<Action>& actions, Side expected) {
+        return std::any_of(actions.begin(), actions.end(), [expected](const Action& action) { return action.kind == Action::Kind::Add && action.side == expected; });
+    }
+
+    static bool hasFlag(const std::vector<Action>& actions, Flag expected) {
+        return std::any_of(actions.begin(), actions.end(), [expected](const Action& action) { return action.kind == Action::Kind::Add && action.flag == expected; });
+    }
+
+    static std::vector<Action> marketAActions() {
+        return {
+            {Action::Kind::Add, 1, Type::Limit, Side::Buy, Decimal(0, 0), Decimal(100, 0), Flag::None},
+            {Action::Kind::Add, 2, Type::Limit, Side::Buy, Decimal(2, 0), Decimal(90, 0), Flag::None},
+            {Action::Kind::Cancel, 2},
+            {Action::Kind::Cancel, 2},
+            {Action::Kind::SetMatching, 0, Type::Limit, Side::Buy, Decimal(0, 0), Decimal(0, 0), Flag::None, false},
+            {Action::Kind::Add, 3, Type::Market, Side::Buy, Decimal(1, 0), Decimal(0, 0), Flag::None},
+            {Action::Kind::Add, 4, Type::Limit, Side::Sell, Decimal(1, 0), Decimal(80, 0), Flag::None},
+            {Action::Kind::Add, 5, Type::Limit, Side::Buy, Decimal(1, 0), Decimal(70, 0), Flag::None},
+            {Action::Kind::SetMatching, 0, Type::Limit, Side::Buy, Decimal(0, 0), Decimal(0, 0), Flag::None, true},
+            {Action::Kind::Add, 6, Type::Limit, Side::Buy, Decimal(2, 0), Decimal(90, 0), Flag::None},
+            {Action::Kind::Add, 6, Type::Limit, Side::Buy, Decimal(2, 0), Decimal(90, 0), Flag::None},
+            {Action::Kind::Add, 7, Type::Limit, Side::Sell, Decimal(2, 0), Decimal(100, 0), Flag::None},
+            {Action::Kind::Add, 8, Type::Limit, Side::Sell, Decimal(2, 0), Decimal(110, 0), Flag::None},
+            {Action::Kind::Add, 9, Type::Limit, Side::Buy, Decimal(1, 0), Decimal(0, 0), Flag::None},
+            {Action::Kind::Add, 10, Type::Limit, Side::Buy, Decimal(3, 0), Decimal(100, 0), Flag::None},
+            {Action::Kind::Add, 11, Type::Limit, Side::Sell, Decimal(5, 0), Decimal(90, 0), Flag::IoC},
+            {Action::Kind::Add, 12, Type::Limit, Side::Buy, Decimal(3, 0), Decimal(100, 0), Flag::AoN},
+            {Action::Kind::Add, 13, Type::Limit, Side::Buy, Decimal(4, 0), Decimal(120, 0), Flag::FoK},
+            {Action::Kind::Add, 14, Type::Market, Side::Sell, Decimal(3, 0), Decimal(0, 0), Flag::None},
+            {Action::Kind::Add, 15, Type::Market, Side::Buy, Decimal(5, 0), Decimal(0, 0), Flag::AoN},
+            {Action::Kind::Add, 16, Type::Market, Side::Buy, Decimal(2, 0), Decimal(0, 0), Flag::FoK},
+            {Action::Kind::Cancel, 8},
+            {Action::Kind::Cancel, 999},
+        };
+    }
+
+    static std::vector<Action> marketBActions() {
+        return {
+            {Action::Kind::Add, 1001, Type::Limit, Side::Sell, Decimal(0, 0), Decimal(100, 0), Flag::None},
+            {Action::Kind::Add, 1002, Type::Limit, Side::Sell, Decimal(2, 0), Decimal(110, 0), Flag::None},
+            {Action::Kind::Cancel, 1002},
+            {Action::Kind::Cancel, 1002},
+            {Action::Kind::SetMatching, 0, Type::Limit, Side::Buy, Decimal(0, 0), Decimal(0, 0), Flag::None, false},
+            {Action::Kind::Add, 1003, Type::Market, Side::Sell, Decimal(1, 0), Decimal(0, 0), Flag::None},
+            {Action::Kind::Add, 1004, Type::Limit, Side::Buy, Decimal(1, 0), Decimal(120, 0), Flag::None},
+            {Action::Kind::Add, 1005, Type::Limit, Side::Sell, Decimal(1, 0), Decimal(130, 0), Flag::None},
+            {Action::Kind::SetMatching, 0, Type::Limit, Side::Buy, Decimal(0, 0), Decimal(0, 0), Flag::None, true},
+            {Action::Kind::Add, 1006, Type::Limit, Side::Sell, Decimal(2, 0), Decimal(110, 0), Flag::None},
+            {Action::Kind::Add, 1006, Type::Limit, Side::Sell, Decimal(2, 0), Decimal(110, 0), Flag::None},
+            {Action::Kind::Add, 1007, Type::Limit, Side::Buy, Decimal(2, 0), Decimal(100, 0), Flag::None},
+            {Action::Kind::Add, 1008, Type::Limit, Side::Buy, Decimal(2, 0), Decimal(90, 0), Flag::None},
+            {Action::Kind::Add, 1009, Type::Limit, Side::Sell, Decimal(1, 0), Decimal(0, 0), Flag::None},
+            {Action::Kind::Add, 1010, Type::Limit, Side::Sell, Decimal(3, 0), Decimal(100, 0), Flag::None},
+            {Action::Kind::Add, 1011, Type::Limit, Side::Buy, Decimal(5, 0), Decimal(110, 0), Flag::IoC},
+            {Action::Kind::Add, 1012, Type::Limit, Side::Sell, Decimal(3, 0), Decimal(100, 0), Flag::AoN},
+            {Action::Kind::Add, 1013, Type::Limit, Side::Sell, Decimal(4, 0), Decimal(80, 0), Flag::FoK},
+            {Action::Kind::Add, 1014, Type::Market, Side::Buy, Decimal(3, 0), Decimal(0, 0), Flag::None},
+            {Action::Kind::Add, 1015, Type::Market, Side::Sell, Decimal(5, 0), Decimal(0, 0), Flag::AoN},
+            {Action::Kind::Add, 1016, Type::Market, Side::Sell, Decimal(2, 0), Decimal(0, 0), Flag::FoK},
+            {Action::Kind::Cancel, 1008},
+            {Action::Kind::Cancel, 1999},
+        };
+    }
+};
+
+TEST_F(DeterminismTest, ReplayProducesSameExecutionTraceAndBookState) {
+    const auto actions = marketAActions();
+    const auto [reportsA, bookA, lastPriceA] = runSequence(actions);
+    const auto [reportsB, bookB, lastPriceB] = runSequence(actions);
+    const auto [reportsC, bookC, lastPriceC] = runSequence(actions);
+
+    ASSERT_EQ(reportsA, reportsB);
+    ASSERT_EQ(reportsA, reportsC);
+    ASSERT_TRUE(hasExactReport(reportsA, "CreateOrder Rejected 1 0 0 ErrInvalidQty"));
+    ASSERT_TRUE(hasExactReport(reportsA, "CancelOrder Canceled 2 2 2"));
+    ASSERT_TRUE(hasExactReport(reportsA, "CancelOrder Rejected 2 0 0 ErrOrderNotExists"));
+    ASSERT_EQ(bookA, bookB);
+    ASSERT_EQ(bookA, bookC);
+    ASSERT_EQ(lastPriceA, lastPriceB);
+    ASSERT_EQ(lastPriceA, lastPriceC);
+}
+
+TEST_F(DeterminismTest, IndependentBooksStayIsolated) {
+    Notification n1;
+    Notification n2;
+    auto ob1 = std::make_shared<orderbook::OrderBook<Notification>>(n1);
+    auto ob2 = std::make_shared<orderbook::OrderBook<Notification>>(n2);
+
+    ob1->addOrder(1000, Type::Limit, Side::Buy, Decimal(2, 0), Decimal(100, 0), Flag::None);
+    ob1->addOrder(1001, Type::Limit, Side::Sell, Decimal(2, 0), Decimal(100, 0), Flag::None);
+
+    ob2->addOrder(2000, Type::Limit, Side::Buy, Decimal(2, 0), Decimal(100, 0), Flag::None);
+    ob2->addOrder(2001, Type::Limit, Side::Sell, Decimal(2, 0), Decimal(100, 0), Flag::None);
+
+    n1.Verify({"CreateOrder Accepted 1000 2 2", "CreateOrder Accepted 1001 2 2", "1000 1001 FilledComplete FilledComplete 2 100"});
+    n2.Verify({"CreateOrder Accepted 2000 2 2", "CreateOrder Accepted 2001 2 2", "2000 2001 FilledComplete FilledComplete 2 100"});
+    ASSERT_EQ(ob1->toString(), ob2->toString());
+}
+
+TEST_F(DeterminismTest, RecoverAtEveryMidpointThenReplaySuffix) {
+    const auto actions = marketAActions();
+
+    for (size_t split = 0; split <= actions.size(); ++split) {
+        Notification baselineN;
+        auto baselineOb = std::make_shared<orderbook::OrderBook<Notification>>(baselineN);
+        for (size_t i = 0; i < split; ++i) {
+            applyAction(actions[i], baselineOb);
+        }
+        const auto snapshotBookState = baselineOb->toString();
+        const auto snapshotLastPrice = baselineOb->last_price;
+
+        baselineN.Reset();
+        for (size_t i = split; i < actions.size(); ++i) {
+            applyAction(actions[i], baselineOb);
+        }
+        const auto baselineSuffixReports = baselineN.Strings();
+        const auto baselineFinalBook = baselineOb->toString();
+        const auto baselineFinalLastPrice = baselineOb->last_price;
+
+        Notification recoveredN;
+        auto recoveredOb = std::make_shared<orderbook::OrderBook<Notification>>(recoveredN);
+        for (size_t i = 0; i < split; ++i) {
+            applyAction(actions[i], recoveredOb);
+        }
+
+        ASSERT_EQ(recoveredOb->toString(), snapshotBookState) << "split=" << split;
+        ASSERT_EQ(recoveredOb->last_price, snapshotLastPrice) << "split=" << split;
+
+        recoveredN.Reset();
+        for (size_t i = split; i < actions.size(); ++i) {
+            applyAction(actions[i], recoveredOb);
+        }
+
+        ASSERT_EQ(recoveredN.Strings(), baselineSuffixReports) << "split=" << split;
+        ASSERT_EQ(recoveredOb->toString(), baselineFinalBook) << "split=" << split;
+        ASSERT_EQ(recoveredOb->last_price, baselineFinalLastPrice) << "split=" << split;
+    }
+}
+
+TEST_F(DeterminismTest, TwoCopiesPerMarketRemainDeterministicWithDifferentInterleavedMarkets) {
+    const auto marketA = marketAActions();
+    const auto marketB = marketBActions();
+
+    ASSERT_TRUE(hasActionKind(marketA, Action::Kind::Cancel));
+    ASSERT_TRUE(hasActionKind(marketA, Action::Kind::SetMatching));
+    ASSERT_TRUE(hasActionKind(marketB, Action::Kind::Cancel));
+    ASSERT_TRUE(hasActionKind(marketB, Action::Kind::SetMatching));
+    ASSERT_TRUE(hasType(marketA, Type::Limit));
+    ASSERT_TRUE(hasType(marketA, Type::Market));
+    ASSERT_TRUE(hasType(marketB, Type::Limit));
+    ASSERT_TRUE(hasType(marketB, Type::Market));
+    ASSERT_TRUE(hasSide(marketA, Side::Buy));
+    ASSERT_TRUE(hasSide(marketA, Side::Sell));
+    ASSERT_TRUE(hasSide(marketB, Side::Buy));
+    ASSERT_TRUE(hasSide(marketB, Side::Sell));
+    ASSERT_TRUE(hasFlag(marketA, Flag::None));
+    ASSERT_TRUE(hasFlag(marketA, Flag::IoC));
+    ASSERT_TRUE(hasFlag(marketA, Flag::AoN));
+    ASSERT_TRUE(hasFlag(marketA, Flag::FoK));
+    ASSERT_TRUE(hasFlag(marketB, Flag::None));
+    ASSERT_TRUE(hasFlag(marketB, Flag::IoC));
+    ASSERT_TRUE(hasFlag(marketB, Flag::AoN));
+    ASSERT_TRUE(hasFlag(marketB, Flag::FoK));
+
+    const auto [standaloneReportsA, standaloneBookA, standaloneLastPriceA] = runSequence(marketA);
+    const auto [standaloneReportsB, standaloneBookB, standaloneLastPriceB] = runSequence(marketB);
+
+    Notification nA1;
+    Notification nA2;
+    Notification nB1;
+    Notification nB2;
+    auto obA1 = std::make_shared<orderbook::OrderBook<Notification>>(nA1);
+    auto obA2 = std::make_shared<orderbook::OrderBook<Notification>>(nA2);
+    auto obB1 = std::make_shared<orderbook::OrderBook<Notification>>(nB1);
+    auto obB2 = std::make_shared<orderbook::OrderBook<Notification>>(nB2);
+
+    const size_t maxActions = std::max(marketA.size(), marketB.size());
+    for (size_t i = 0; i < maxActions; ++i) {
+        if (i < marketA.size()) {
+            applyAction(marketA[i], obA1);
+            applyAction(marketA[i], obA2);
+        }
+        if (i < marketB.size()) {
+            applyAction(marketB[i], obB1);
+            applyAction(marketB[i], obB2);
+        }
+    }
+
+    ASSERT_EQ(nA1.Strings(), nA2.Strings());
+    ASSERT_EQ(obA1->toString(), obA2->toString());
+    ASSERT_EQ(obA1->last_price, obA2->last_price);
+
+    ASSERT_EQ(nB1.Strings(), nB2.Strings());
+    ASSERT_EQ(obB1->toString(), obB2->toString());
+    ASSERT_EQ(obB1->last_price, obB2->last_price);
+
+    ASSERT_EQ(nA1.Strings(), standaloneReportsA);
+    ASSERT_EQ(obA1->toString(), standaloneBookA);
+    ASSERT_EQ(obA1->last_price, standaloneLastPriceA);
+    ASSERT_EQ(nB1.Strings(), standaloneReportsB);
+    ASSERT_EQ(obB1->toString(), standaloneBookB);
+    ASSERT_EQ(obB1->last_price, standaloneLastPriceB);
+
+    ASSERT_TRUE(hasReportContaining(nA1.Strings(), "Filled"));
+    ASSERT_TRUE(hasReportContaining(nA1.Strings(), "CreateOrder Rejected"));
+    ASSERT_TRUE(hasReportContaining(nA1.Strings(), "CancelOrder Canceled"));
+    ASSERT_TRUE(hasReportContaining(nA1.Strings(), "CancelOrder Rejected"));
+    ASSERT_TRUE(hasReportContaining(nB1.Strings(), "Filled"));
+    ASSERT_TRUE(hasReportContaining(nB1.Strings(), "CreateOrder Rejected"));
+    ASSERT_TRUE(hasReportContaining(nB1.Strings(), "CancelOrder Canceled"));
+    ASSERT_TRUE(hasReportContaining(nB1.Strings(), "CancelOrder Rejected"));
+}
diff --git a/test/orderbook_test.cpp b/test/orderbook_test.cpp
index d4a8ba7..b7180cb 100644
--- a/test/orderbook_test.cpp
+++ b/test/orderbook_test.cpp
@@ -1,6 +1,9 @@
 #include <gtest/gtest.h>
 
+#include <cstdint>
+#include <memory>
 #include <string>
+#include <tuple>
 #include <vector>
 
 #include "util.cpp"