diff --git a/editor/tests/step398_test.cpp b/editor/tests/step398_test.cpp
new file mode 100644
index 0000000..8c56e0b
--- /dev/null
+++ b/editor/tests/step398_test.cpp
@@ -0,0 +1,152 @@
+// Step 398: Cast Expressions (12 tests)
+
+#include <cassert>
+#include <iostream>
+#include <string>
+#include "ast/Parser.h"
+#include "ast/CppAdvancedNodes.h"
+
+int main() {
+    int passed = 0;
+
+    // Test 1: CastExpression node construction
+    {
+        CastExpression ce("cast_1", "static_cast", "int");
+        assert(ce.conceptType == "CastExpression");
+        assert(ce.castKind == "static_cast");
+        assert(ce.targetType == "int");
+        std::cout << "PASS: test 1 — CastExpression construction\n";
+        passed++;
+    }
+
+    // Test 2: Detect static_cast
+    {
+        assert(detectCastKind("static_cast<int>(x)") == "static_cast");
+        std::cout << "PASS: test 2 — detect static_cast\n";
+        passed++;
+    }
+
+    // Test 3: Detect dynamic_cast
+    {
+        assert(detectCastKind("dynamic_cast<Derived*>(base)") == "dynamic_cast");
+        std::cout << "PASS: test 3 — detect dynamic_cast\n";
+        passed++;
+    }
+
+    // Test 4: Detect reinterpret_cast
+    {
+        assert(detectCastKind("reinterpret_cast<char*>(ptr)") == "reinterpret_cast");
+        std::cout << "PASS: test 4 — detect reinterpret_cast\n";
+        passed++;
+    }
+
+    // Test 5: Detect const_cast
+    {
+        assert(detectCastKind("const_cast<int*>(cptr)") == "const_cast");
+        std::cout << "PASS: test 5 — detect const_cast\n";
+        passed++;
+    }
+
+    // Test 6: Risk level for casts
+    {
+        assert(castRiskLevel("static_cast") == "low");
+        assert(castRiskLevel("dynamic_cast") == "medium");
+        assert(castRiskLevel("const_cast") == "medium");
+        assert(castRiskLevel("reinterpret_cast") == "high");
+        std::cout << "PASS: test 6 — cast risk levels\n";
+        passed++;
+    }
+
+    // Test 7: Parse static_cast in function
+    {
+        std::string src = R"(
+void convert() {
+    double d = 3.14;
+    int i = static_cast<int>(d);
+}
+)";
+        auto mod = TreeSitterParser::parseCpp(src);
+        assert(mod != nullptr);
+        auto& fns = mod->getChildren("functions");
+        assert(!fns.empty());
+        auto* fn = static_cast<Function*>(fns[0]);
+        assert(fn->name == "convert");
+        std::cout << "PASS: test 7 — parse static_cast in function\n";
+        passed++;
+    }
+
+    // Test 8: Parse dynamic_cast in function
+    {
+        std::string src = R"(
+class Base { virtual ~Base() {} };
+class Derived : public Base {};
+void check(Base* b) {
+    auto* d = dynamic_cast<Derived*>(b);
+}
+)";
+        auto mod = TreeSitterParser::parseCpp(src);
+        assert(mod != nullptr);
+        std::cout << "PASS: test 8 — parse dynamic_cast in function\n";
+        passed++;
+    }
+
+    // Test 9: CastExpression with operand child
+    {
+        CastExpression ce("cast_2", "static_cast", "const Foo*");
+        auto* operand = new VariableReference("ref_1", "bar");
+        ce.setChild("operand", operand);
+
+        auto* op = ce.getChild("operand");
+        assert(op != nullptr);
+        assert(op->conceptType == "VariableReference");
+        std::cout << "PASS: test 9 — CastExpression with operand child\n";
+        passed++;
+    }
+
+    // Test 10: Multiple casts in one function (no crash)
+    {
+        std::string src = R"(
+void multicast() {
+    int x = 42;
+    double d = static_cast<double>(x);
+    const int* cp = &x;
+    int* p = const_cast<int*>(cp);
+}
+)";
+        auto mod = TreeSitterParser::parseCpp(src);
+        assert(mod != nullptr);
+        auto& fns = mod->getChildren("functions");
+        assert(!fns.empty());
+        std::cout << "PASS: test 10 — multiple casts in one function\n";
+        passed++;
+    }
+
+    // Test 11: CastExpression span tracking
+    {
+        CastExpression ce("cast_3", "dynamic_cast", "Widget*");
+        ce.setSpan(15, 8, 15, 40);
+        assert(ce.spanStartLine == 15);
+        assert(ce.spanEndCol == 40);
+        std::cout << "PASS: test 11 — CastExpression span tracking\n";
+        passed++;
+    }
+
+    // Test 12: Risk annotation mapping for all cast kinds
+    {
+        std::vector<std::pair<std::string, std::string>> expected = {
+            {"static_cast", "low"},
+            {"dynamic_cast", "medium"},
+            {"const_cast", "medium"},
+            {"reinterpret_cast", "high"}
+        };
+        for (const auto& [kind, risk] : expected) {
+            CastExpression ce("cast_x", kind, "void*");
+            assert(castRiskLevel(ce.castKind) == risk);
+        }
+        std::cout << "PASS: test 12 — risk annotation mapping\n";
+        passed++;
+    }
+
+    std::cout << "\nStep 398 result: " << passed << "/12 tests passed\n";
+    return (passed == 12) ? 0 : 1;
+}