diff --git a/README.md b/README.md
index 575409b3a96..c5b6b315990 100644
--- a/README.md
+++ b/README.md
@@ -220,3 +220,5 @@ Thank you for considering to help out with the source code! If you'd like to con
 # License
 
 java-tron is released under the [LGPLv3 license](https://github.com/tronprotocol/java-tron/blob/master/LICENSE).
+
+<!-- intentional non-Java change to verify Coverage Gate G1.4 (mixed PR ignores docs lines) -->
diff --git a/common/src/main/java/org/tron/common/utils/DecodeUtil.java b/common/src/main/java/org/tron/common/utils/DecodeUtil.java
index 769268da2b9..6161218e6da 100644
--- a/common/src/main/java/org/tron/common/utils/DecodeUtil.java
+++ b/common/src/main/java/org/tron/common/utils/DecodeUtil.java
@@ -32,4 +32,19 @@ public static boolean addressValid(byte[] address) {
     return true;
   }
 
+  /**
+   * Intentional uncovered helper used to exercise the Coverage Gate FAIL path
+   * (changed-line coverage below 60%). No unit test is added on purpose.
+   * Revert before merging.
+   */
+  public static int hexLengthForAddress(int byteLength) {
+    if (byteLength < 0) {
+      throw new IllegalArgumentException("byteLength must be non-negative");
+    }
+    if (byteLength == 0) {
+      return 0;
+    }
+    return byteLength * 2;
+  }
+
 }
diff --git a/framework/src/test/java/org/tron/common/utils/DecodeUtilTest.java b/framework/src/test/java/org/tron/common/utils/DecodeUtilTest.java
new file mode 100644
index 00000000000..f2e10a4e5c7
--- /dev/null
+++ b/framework/src/test/java/org/tron/common/utils/DecodeUtilTest.java
@@ -0,0 +1,58 @@
+package org.tron.common.utils;
+
+import org.junit.AfterClass;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.tron.core.Constant;
+
+public class DecodeUtilTest {
+
+  private static byte savedPrefixByte;
+
+  @BeforeClass
+  public static void saveAddressPrefix() {
+    savedPrefixByte = DecodeUtil.addressPreFixByte;
+    DecodeUtil.addressPreFixByte = Constant.ADD_PRE_FIX_BYTE_MAINNET;
+  }
+
+  @AfterClass
+  public static void restoreAddressPrefix() {
+    DecodeUtil.addressPreFixByte = savedPrefixByte;
+  }
+
+  @Test
+  public void addressValidRejectsNull() {
+    Assert.assertFalse(DecodeUtil.addressValid(null));
+  }
+
+  @Test
+  public void addressValidRejectsEmptyArray() {
+    Assert.assertFalse(DecodeUtil.addressValid(new byte[0]));
+  }
+
+  @Test
+  public void addressValidRejectsWrongLength() {
+    byte[] tooShort = new byte[DecodeUtil.ADDRESS_SIZE / 2 - 1];
+    tooShort[0] = Constant.ADD_PRE_FIX_BYTE_MAINNET;
+    Assert.assertFalse(DecodeUtil.addressValid(tooShort));
+
+    byte[] tooLong = new byte[DecodeUtil.ADDRESS_SIZE / 2 + 1];
+    tooLong[0] = Constant.ADD_PRE_FIX_BYTE_MAINNET;
+    Assert.assertFalse(DecodeUtil.addressValid(tooLong));
+  }
+
+  @Test
+  public void addressValidRejectsWrongPrefix() {
+    byte[] address = new byte[DecodeUtil.ADDRESS_SIZE / 2];
+    address[0] = (byte) (Constant.ADD_PRE_FIX_BYTE_MAINNET + 1);
+    Assert.assertFalse(DecodeUtil.addressValid(address));
+  }
+
+  @Test
+  public void addressValidAcceptsCanonicalAddress() {
+    byte[] address = new byte[DecodeUtil.ADDRESS_SIZE / 2];
+    address[0] = Constant.ADD_PRE_FIX_BYTE_MAINNET;
+    Assert.assertTrue(DecodeUtil.addressValid(address));
+  }
+}