fix: < to <= in validate_uint_mutation

crates/evm/fuzz/src/strategies/mutators.rs

@@ -525,7 +525,7 @@ fn validate_uint_mutation(original: U256, mutated: U256, size: usize) -> Option<
 
     // Check if mutated value fits the given size.
     let max = if size < 256 { (U256::from(1) << size) - U256::from(1) } else { U256::MAX };
-    (mutated < max).then_some(mutated)
+    (mutated <= max).then_some(mutated)
 }
 
 /// Returns mutated int value if different from the original value and if it fits in the given size,
@@ -550,6 +550,22 @@ mod tests {
     use super::*;
     use proptest::test_runner::Config;
 
+    #[test]
+    fn validate_uint_mutation_accepts_inclusive_max() {
+        // For width `size`, valid unsigned values are 0..=max where max = 2^size - 1.
+        // Regression: `< max` incorrectly rejected `mutated == max`; must use `<= max`.
+        for size in [8usize, 16, 32, 64, 128] {
+            let max = (U256::from(1) << size) - U256::from(1);
+            assert_eq!(
+                super::validate_uint_mutation(U256::ZERO, max, size),
+                Some(max),
+                "size={size}"
+            );
+        }
+        let original = U256::from(1);
+        assert_eq!(super::validate_uint_mutation(original, U256::MAX, 256), Some(U256::MAX));
+    }
+
     #[test]
     fn test_mutate_uint() {
         let mut runner = TestRunner::new(Config::default());