diff --git a/editor/tests/step399_test.cpp b/editor/tests/step399_test.cpp
new file mode 100644
index 0000000..f3a6bae
--- /dev/null
+++ b/editor/tests/step399_test.cpp
@@ -0,0 +1,201 @@
+// Step 399: Phase 16a Integration (8 tests)
+
+#include <cassert>
+#include <iostream>
+#include <string>
+#include "ast/Parser.h"
+#include "ast/Generator.h"
+#include "ast/CppAdvancedNodes.h"
+#include "ast/EnumNamespaceNodes.h"
+#include "ast/ClassDeclaration.h"
+#include "Pipeline.h"
+
+int main() {
+    int passed = 0;
+
+    // Test 1: Parse Whetstone-style header fragment with all new constructs
+    {
+        std::string src = R"(
+#pragma once
+#include <memory>
+#include <string>
+
+using json = nlohmann::json;
+
+class ASTNode {
+public:
+    static int nodeCount;
+    virtual void accept() const { }
+    void setId(const std::string& id) { id_ = id; }
+private:
+    std::string id_;
+};
+
+void process(std::unique_ptr<ASTNode> node) {
+    auto* raw = node.get();
+}
+)";
+        auto mod = TreeSitterParser::parseCpp(src);
+        assert(mod != nullptr);
+
+        // Should have: type alias, class, function
+        bool hasTypeAlias = false;
+        for (auto* s : mod->getChildren("statements")) {
+            if (s->conceptType == "TypeAlias") hasTypeAlias = true;
+        }
+        assert(hasTypeAlias);
+
+        auto& classes = mod->getChildren("classes");
+        assert(!classes.empty());
+        auto* cls = static_cast<ClassDeclaration*>(classes[0]);
+        assert(cls->name == "ASTNode");
+
+        auto& fns = mod->getChildren("functions");
+        assert(!fns.empty());
+
+        std::cout << "PASS: test 1 — parse Whetstone-style header\n";
+        passed++;
+    }
+
+    // Test 2: Roundtrip: parse → generate produces valid C++
+    {
+        std::string src = R"(
+class Widget {
+public:
+    static int count;
+    virtual void draw() { }
+};
+)";
+        auto mod1 = TreeSitterParser::parseCpp(src);
+        assert(mod1 != nullptr);
+        auto& classes1 = mod1->getChildren("classes");
+        assert(!classes1.empty());
+
+        // Generate C++ from parsed AST
+        CppGenerator gen;
+        std::string generated = gen.generate(mod1.get());
+        assert(!generated.empty());
+
+        // Generated code should be non-empty (generator produces output)
+        // The CppGenerator may not perfectly roundtrip all class constructs
+        // but it should produce something
+
+        // Parse the generated code — verify it doesn't crash
+        auto mod2 = TreeSitterParser::parseCpp(generated);
+        assert(mod2 != nullptr);
+
+        std::cout << "PASS: test 2 — roundtrip parse → generate\n";
+        passed++;
+    }
+
+    // Test 3: Qualifier detection on mixed Whetstone code
+    {
+        std::string code1 = "static constexpr int MAX_NODES = 1000;";
+        auto q1 = detectQualifiers(code1);
+        assert(q1.isStatic && q1.isConstexpr);
+
+        std::string code2 = "const std::string& getName() const;";
+        assert(isConstMethod(code2));
+
+        std::string code3 = "std::unique_ptr<Module> parseModule();";
+        auto q3 = detectQualifiers(code3);
+        assert(q3.smartPointerKind == "unique_ptr");
+        std::cout << "PASS: test 3 — qualifier detection on mixed code\n";
+        passed++;
+    }
+
+    // Test 4: Smart pointer detection and ownership mapping
+    {
+        // unique_ptr → Unique (Rust: Box<T>)
+        assert(smartPointerOwnership(detectSmartPointerKind("std::unique_ptr<T>")) == "Unique");
+        // shared_ptr → Shared_ARC (Rust: Arc<T>)
+        assert(smartPointerOwnership(detectSmartPointerKind("std::shared_ptr<T>")) == "Shared_ARC");
+        // Regular pointer → no mapping
+        assert(smartPointerOwnership(detectSmartPointerKind("T*")) == "");
+        std::cout << "PASS: test 4 — smart pointer ownership mapping\n";
+        passed++;
+    }
+
+    // Test 5: Cast risk assessment
+    {
+        // static_cast = low, reinterpret_cast = high
+        assert(castRiskLevel("static_cast") == "low");
+        assert(castRiskLevel("reinterpret_cast") == "high");
+
+        // CastExpression node with risk
+        CastExpression safe("c1", "static_cast", "int");
+        CastExpression risky("c2", "reinterpret_cast", "void*");
+        assert(castRiskLevel(safe.castKind) != castRiskLevel(risky.castKind));
+        std::cout << "PASS: test 5 — cast risk assessment\n";
+        passed++;
+    }
+
+    // Test 6: Auto type detection in expressions
+    {
+        assert(isAutoType("auto"));
+        assert(isAutoType("auto*"));
+        assert(isAutoType("const auto&"));
+        assert(!isAutoType("int"));
+        assert(!isAutoType("automatic"));
+
+        AutoType at("a1", "const &");
+        assert(at.modifiers == "const &");
+        std::cout << "PASS: test 6 — auto type detection\n";
+        passed++;
+    }
+
+    // Test 7: Parse complex class with multiple features
+    {
+        std::string src = R"(
+class Pipeline {
+public:
+    static Pipeline& instance() {
+        static Pipeline p;
+        return p;
+    }
+    virtual void execute() { }
+    void run() const { execute(); }
+private:
+    std::shared_ptr<Config> config_;
+};
+)";
+        auto mod = TreeSitterParser::parseCpp(src);
+        auto& classes = mod->getChildren("classes");
+        assert(!classes.empty());
+        auto* cls = static_cast<ClassDeclaration*>(classes[0]);
+        assert(cls->name == "Pipeline");
+
+        auto& methods = cls->getChildren("methods");
+        assert(methods.size() >= 2);
+
+        // Check static method
+        bool hasStatic = false;
+        for (auto* m : methods) {
+            auto* meth = static_cast<MethodDeclaration*>(m);
+            if (meth->isStatic) hasStatic = true;
+        }
+        assert(hasStatic);
+        std::cout << "PASS: test 7 — complex class with multiple features\n";
+        passed++;
+    }
+
+    // Test 8: Pipeline integration — C++ parse produces valid AST
+    {
+        std::string src = R"(
+using StringVec = std::vector<std::string>;
+
+void process(StringVec items) {
+    auto count = items.size();
+}
+)";
+        Pipeline pipeline;
+        auto result = pipeline.run(src, "cpp", "cpp");
+        assert(result.ast != nullptr);
+        assert(result.ast->targetLanguage == "cpp");
+        std::cout << "PASS: test 8 — pipeline integration\n";
+        passed++;
+    }
+
+    std::cout << "\nStep 399 result: " << passed << "/8 tests passed\n";
+    return (passed == 8) ? 0 : 1;
+}