diff --git a/src/test/java/com/alibaba/qlexpress4/test/issue/Issue439RegressionTest.java b/src/test/java/com/alibaba/qlexpress4/test/issue/Issue439RegressionTest.java
new file mode 100644
index 000000000..38545b4f7
--- /dev/null
+++ b/src/test/java/com/alibaba/qlexpress4/test/issue/Issue439RegressionTest.java
@@ -0,0 +1,201 @@
+package com.alibaba.qlexpress4.test.issue;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import com.alibaba.qlexpress4.Express4Runner;
+import com.alibaba.qlexpress4.InitOptions;
+import com.alibaba.qlexpress4.QLOptions;
+import com.alibaba.qlexpress4.aparser.InterpolationMode;
+import com.alibaba.qlexpress4.aparser.MockOpM;
+import com.alibaba.qlexpress4.aparser.QLexer;
+import com.alibaba.qlexpress4.aparser.Token;
+import com.alibaba.qlexpress4.security.QLSecurityStrategy;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Regression test for issue #439.
+ *
+ * Issue: In v4, the expression `if(oldObj!=null&&!oldObj.getLong("status").equals(5L))`
+ * fails to parse because `&&!` (&& immediately followed by !, with no whitespace)
+ * was not correctly tokenized by the old ANTLR4-based parser.
+ *
+ * The fix replaced the ANTLR4 parser with a hand-written Lexer that correctly
+ * separates `&&` (OPID) from `!` (BANG) even when they are adjacent.
+ */
+public class Issue439RegressionTest {
+
+    private static final Express4Runner RUNNER =
+        new Express4Runner(InitOptions.builder().securityStrategy(QLSecurityStrategy.open()).build());
+
+    // ==================== Lexer-level tokenization tests ====================
+
+    /**
+     * `&&!` should be tokenized as OPID("&&") + BANG("!")
+     */
+    @Test
+    public void lexerShouldSplitAndBangIntoOpidAndBang() {
+        List<Token> tokens = tokenize("a&&!b");
+        // a (ID) && (OPID) ! (BANG) b (ID) EOF
+        Token andToken = findTokenByType(tokens, QLexer.OPID);
+        Assert.assertNotNull("expected OPID token for &&", andToken);
+        Assert.assertEquals("&&", andToken.getText());
+
+        Token bangToken = findTokenByType(tokens, QLexer.BANG);
+        Assert.assertNotNull("expected BANG token for !", bangToken);
+        Assert.assertEquals("!", bangToken.getText());
+    }
+
+    /**
+     * `||!` should be tokenized as OPID("||") + BANG("!")
+     */
+    @Test
+    public void lexerShouldSplitOrBangIntoOpidAndBang() {
+        List<Token> tokens = tokenize("a||!b");
+        Token orToken = findTokenByType(tokens, QLexer.OPID);
+        Assert.assertNotNull("expected OPID token for ||", orToken);
+        Assert.assertEquals("||", orToken.getText());
+
+        Token bangToken = findTokenByType(tokens, QLexer.BANG);
+        Assert.assertNotNull("expected BANG token for !", bangToken);
+        Assert.assertEquals("!", bangToken.getText());
+    }
+
+    /**
+     * `==!` should be tokenized as OPID("==") + BANG("!")
+     */
+    @Test
+    public void lexerShouldSplitEqBangIntoOpidAndBang() {
+        List<Token> tokens = tokenize("a==!b");
+        Token eqToken = findTokenByType(tokens, QLexer.OPID);
+        Assert.assertNotNull("expected OPID token for ==", eqToken);
+        Assert.assertEquals("==", eqToken.getText());
+
+        Token bangToken = findTokenByType(tokens, QLexer.BANG);
+        Assert.assertNotNull("expected BANG token for !", bangToken);
+        Assert.assertEquals("!", bangToken.getText());
+    }
+
+    // ==================== Parser / Execution tests ====================
+
+    /**
+     * `a && !b` with spaces - baseline case that should always work
+     */
+    @Test
+    public void executeLogicalAndNotWithSpaces() {
+        Map<String, Object> ctx = new HashMap<>();
+        ctx.put("a", true);
+        ctx.put("b", false);
+        Object result = run("a && !b", ctx);
+        Assert.assertEquals(true, result);
+    }
+
+    /**
+     * `a&&!b` without spaces - core regression case for issue #439
+     */
+    @Test
+    public void executeLogicalAndNotWithoutSpaces() {
+        Map<String, Object> ctx = new HashMap<>();
+        ctx.put("a", true);
+        ctx.put("b", false);
+        Object result = run("a&&!b", ctx);
+        Assert.assertEquals(true, result);
+    }
+
+    /**
+     * `if(x!=null&&!y){return 1}` - typical pattern from issue report
+     */
+    @Test
+    public void executeIfNotNullAndNotWithNoSpaces() {
+        Map<String, Object> ctx = new HashMap<>();
+        ctx.put("x", "something");
+        ctx.put("y", false);
+        Object result = run("if(x!=null&&!y){return 1}", ctx);
+        Assert.assertEquals(1, result);
+    }
+
+    /**
+     * `a && !b && !c` - nested logical AND with multiple NOT operators
+     */
+    @Test
+    public void executeNestedAndNotWithoutSpaces() {
+        Map<String, Object> ctx = new HashMap<>();
+        ctx.put("a", true);
+        ctx.put("b", false);
+        ctx.put("c", false);
+        Object result = run("a&&!b&&!c", ctx);
+        Assert.assertEquals(true, result);
+    }
+
+    /**
+     * `oldObj!=null&&!oldObj.equals("test")` - complex real-world pattern from issue
+     */
+    @Test
+    public void executeComplexNotNullAndNotEqualsWithoutSpaces() {
+        Map<String, Object> ctx = new HashMap<>();
+        ctx.put("oldObj", "hello");
+        Object result = run("oldObj!=null&&!oldObj.equals(\"test\")", ctx);
+        Assert.assertEquals(true, result);
+    }
+
+    /**
+     * `oldObj!=null&&!oldObj.equals("test")` when oldObj is null - short circuit
+     */
+    @Test
+    public void executeComplexNotNullShortCircuitWhenNull() {
+        Map<String, Object> ctx = new HashMap<>();
+        ctx.put("oldObj", null);
+        Object result = run("oldObj!=null&&!oldObj.equals(\"test\")", ctx);
+        Assert.assertEquals(false, result);
+    }
+
+    /**
+     * `||!` execution: `a||!b` without spaces
+     */
+    @Test
+    public void executeLogicalOrNotWithoutSpaces() {
+        Map<String, Object> ctx = new HashMap<>();
+        ctx.put("a", false);
+        ctx.put("b", false);
+        Object result = run("a||!b", ctx);
+        Assert.assertEquals(true, result);
+    }
+
+    /**
+     * Full original pattern from issue #439
+     */
+    @Test
+    public void executeOriginalIssuePattern() {
+        Map<String, Object> ctx = new HashMap<>();
+        Map<String, Object> oldObj = new HashMap<>();
+        oldObj.put("status", 3L);
+        ctx.put("oldObj", oldObj);
+        // Simulates: if(oldObj!=null&&!oldObj.get("status").equals(5L)){return true}
+        Object result = run(
+            "if(oldObj!=null&&!oldObj.get(\"status\").equals(5L)){return true}",
+            ctx);
+        Assert.assertEquals(true, result);
+    }
+
+    // ==================== Helper methods ====================
+
+    private List<Token> tokenize(String script) {
+        return QLexer.tokenize(script, new MockOpM(), InterpolationMode.VARIABLE, "${", "}", true);
+    }
+
+    private Token findTokenByType(List<Token> tokens, int type) {
+        for (Token token : tokens) {
+            if (token.getType() == type) {
+                return token;
+            }
+        }
+        return null;
+    }
+
+    private Object run(String script, Map<String, Object> context) {
+        return RUNNER.execute(script, context, QLOptions.DEFAULT_OPTIONS).getResult();
+    }
+}