diff --git a/defects/swift/unit/SwiftTest.java b/defects/swift/unit/SwiftTest.java
new file mode 100644
index 000000000..d38dbaf6c
--- /dev/null
+++ b/defects/swift/unit/SwiftTest.java
@@ -0,0 +1,143 @@
+import java.util.*;
+
+/**
+ * CWE-407 simulation: Swift LoadableByAddress pass linear membership tests.
+ *
+ * The StructLoweringState in LoadableByAddress.cpp uses SmallVector with
+ * std::find for membership tests on largeLoadableArgs, applies, and other
+ * instruction vectors. For each instruction in the function, std::find
+ * performs O(A) linear scan where A = number of large loadable args.
+ *
+ * Defect: O(I x A) where I = instructions, A = large loadable args
+ * Fix: SmallPtrSet shadow for O(1) membership tests -> O(I + A)
+ *
+ * swift-0001: LoadableByAddress largeLoadableArgs/applies linear membership
+ */
+public class SwiftTest {
+
+    // --- Defective: SmallVector + std::find pattern ---
+    static long visitApplyDefective(List<Object> largeLoadableArgs,
+                                     List<Object> funcSigArgs,
+                                     List<Object> applies,
+                                     List<Object[]> applyOperands) {
+        long ops = 0;
+        for (Object[] operands : applyOperands) {
+            for (Object operand : operands) {
+                ops++;
+                // std::find(largeLoadableArgs.begin(), ..., currOperand)
+                boolean found = false;
+                for (Object arg : largeLoadableArgs) {
+                    ops++;
+                    if (arg == operand) { found = true; break; }
+                }
+                if (!found) {
+                    // std::find(funcSigArgs.begin(), ..., currOperand)
+                    for (Object arg : funcSigArgs) {
+                        ops++;
+                        if (arg == operand) { found = true; break; }
+                    }
+                }
+                if (found) {
+                    // Dedup check: std::find(applies.begin(), ..., instr)
+                    Object instr = operands; // proxy for instruction
+                    for (Object a : applies) {
+                        ops++;
+                        if (a == instr) { found = false; break; }
+                    }
+                    if (found) applies.add(instr);
+                }
+            }
+        }
+        return ops;
+    }
+
+    // --- Fixed: SmallPtrSet shadow for O(1) lookup ---
+    static long visitApplyFixed(Set<Object> largeLoadableArgsSet,
+                                 Set<Object> funcSigArgsSet,
+                                 Set<Object> appliesSet,
+                                 List<Object[]> applyOperands) {
+        long ops = 0;
+        for (Object[] operands : applyOperands) {
+            for (Object operand : operands) {
+                ops++;
+                boolean found = largeLoadableArgsSet.contains(operand);
+                ops++;
+                if (!found) {
+                    found = funcSigArgsSet.contains(operand);
+                    ops++;
+                }
+                if (found) {
+                    Object instr = operands;
+                    if (appliesSet.add(instr)) {
+                        ops++;
+                    }
+                }
+            }
+        }
+        return ops;
+    }
+
+    public static void main(String[] args) {
+        // Simulate a function with A large loadable args and I apply instructions
+        int[] sizes = {10, 50, 100, 200, 500};
+
+        System.out.println("swift-0001: LoadableByAddress largeLoadableArgs linear membership");
+        System.out.println("=================================================================");
+        System.out.printf("%-8s %-14s %-14s %-10s %-6s%n",
+                "A(args)", "Defective ops", "Fixed ops", "Ratio", "Status");
+
+        boolean allPass = true;
+        for (int A : sizes) {
+            // Create A large loadable args
+            List<Object> largeLoadableArgs = new ArrayList<>();
+            Set<Object> largeLoadableArgsSet = new HashSet<>();
+            List<Object> funcSigArgs = new ArrayList<>();
+            Set<Object> funcSigArgsSet = new HashSet<>();
+            List<Object> applies = new ArrayList<>();
+            Set<Object> appliesSet = new HashSet<>();
+
+            Object[] argPool = new Object[A];
+            for (int i = 0; i < A; i++) {
+                argPool[i] = new Object();
+                largeLoadableArgs.add(argPool[i]);
+                largeLoadableArgsSet.add(argPool[i]);
+                funcSigArgs.add(argPool[i]);
+                funcSigArgsSet.add(argPool[i]);
+            }
+
+            // Create I apply instructions, each with 3 operands from the arg pool
+            int I = A * 2;  // instructions proportional to args
+            List<Object[]> applyOperands = new ArrayList<>();
+            Random rng = new Random(42);
+            for (int i = 0; i < I; i++) {
+                Object[] ops = new Object[3];
+                for (int j = 0; j < 3; j++) {
+                    ops[j] = argPool[rng.nextInt(A)];
+                }
+                applyOperands.add(ops);
+            }
+
+            long defectOps = visitApplyDefective(
+                    new ArrayList<>(largeLoadableArgs),
+                    new ArrayList<>(funcSigArgs),
+                    new ArrayList<>(applies),
+                    applyOperands);
+            long fixedOps = visitApplyFixed(
+                    new HashSet<>(largeLoadableArgsSet),
+                    new HashSet<>(funcSigArgsSet),
+                    new HashSet<>(appliesSet),
+                    applyOperands);
+
+            double ratio = (double) defectOps / fixedOps;
+            boolean pass = ratio > 2.0;
+            allPass &= pass;
+
+            System.out.printf("%-8d %-14d %-14d %-10.1f %-6s%n",
+                    A, defectOps, fixedOps, ratio, pass ? "PASS" : "FAIL");
+        }
+
+        System.out.println();
+        System.out.println(allPass ? "ALL PASS" : "SOME FAIL");
+        System.exit(allPass ? 0 : 1);
+    }
+}