diff --git a/src/evm/SolidityMetadata.test.ts b/src/evm/SolidityMetadata.test.ts
index ff6c76bf9a..b10213ee4c 100644
--- a/src/evm/SolidityMetadata.test.ts
+++ b/src/evm/SolidityMetadata.test.ts
@@ -119,6 +119,9 @@ it("decodes distinct byte keys and distinct nested-container keys", () => {
   expect(inspectSolidityMetadata(bytecode("a2810101810202"))).toMatchObject({
     status: "partial",
   });
+  expect(inspectSolidityMetadata(bytecode("a281800181a002"))).toMatchObject({
+    status: "partial",
+  });
 });
 
 it.each([
@@ -128,6 +131,9 @@ it.each([
   ["floating point", "a16178fa3f800000"],
   ["duplicate key", "a2617801617802"],
   ["duplicate byte key", "a2410101410102"],
+  ["duplicate array key", "a280018002"],
+  ["duplicate map key", "a2a001a002"],
+  ["duplicate map key in another order", "a2a20102030401a20304010202"],
   ["excessive nesting", "a16178" + "81".repeat(65) + "00"],
   ["impossible collection", "a161788a00"],
 ])("keeps exact ranges and unavailable interpretation for %s", (_name, hex) => {
@@ -139,6 +145,18 @@ it.each([
   });
 });
 
+it("rejects repeated deeply nested container keys promptly", () => {
+  const key = "81".repeat(62) + "00";
+  const started = performance.now();
+  expect(
+    inspectSolidityMetadata(bytecode("a2" + key + "01" + key + "02")),
+  ).toMatchObject({
+    status: "not-decoded",
+    diagnostic: expect.stringContaining("found repeat map key"),
+  });
+  expect(performance.now() - started).toBeLessThan(1000);
+});
+
 it.each(["", "60006000f3", "000000", "00010001"])(
   "does not claim absent Solidity metadata for an unavailable trailer: %s",
   (hex) =>
diff --git a/src/evm/SolidityMetadata.ts b/src/evm/SolidityMetadata.ts
index b5cdfb64b1..ab92c97ea5 100644
--- a/src/evm/SolidityMetadata.ts
+++ b/src/evm/SolidityMetadata.ts
@@ -90,6 +90,17 @@ const scalar = (value: unknown): SolidityMetadataScalar => {
   );
 };
 
+/** Value identity for duplicate-key checks; map entry order is not significant. */
+const keyIdentity = (value: unknown): string => {
+  if (value instanceof Map)
+    return `{${[...value]
+      .map(([key, item]) => `${keyIdentity(key)}:${keyIdentity(item)}`)
+      .sort()
+      .join(",")}}`;
+  if (Array.isArray(value)) return `[${value.map(keyIdentity).join(",")}]`;
+  return JSON.stringify(scalar(value));
+};
+
 /** Parse only a plausible terminal root-map candidate; never establish absence. */
 export const inspectSolidityMetadata = (
   bytes: Uint8Array,
@@ -122,20 +133,15 @@ export const inspectSolidityMetadata = (
     });
     if (!(raw instanceof Map))
       throw new Error("Terminal CBOR candidate did not decode to a root map.");
-    // cborg compares Map keys by identity, so repeated byte-string keys (each
-    // its own Uint8Array) pass its duplicate check; compare scalars by value.
+    // cborg compares Map keys by identity, so repeated byte-string or container
+    // keys (each its own object) pass its duplicate check; compare by value.
     const seen = new Set<string>();
     for (const [key, value] of raw as Map<unknown, unknown>) {
-      const entry = { key: scalar(key), value: scalar(value) };
-      if (entry.key.kind !== "uninterpreted") {
-        const identity = JSON.stringify(entry.key);
-        if (seen.has(identity))
-          throw new Error(
-            `CBOR decode error: found repeat map key ${identity}`,
-          );
-        seen.add(identity);
-      }
-      result.entries.push(entry);
+      const identity = keyIdentity(key);
+      if (seen.has(identity))
+        throw new Error(`CBOR decode error: found repeat map key ${identity}`);
+      seen.add(identity);
+      result.entries.push({ key: scalar(key), value: scalar(value) });
     }
     result.status = result.entries.some(
       ({ key, value }) =>