required string? incorrectly loses nullable and gains MinLength=1

src/NJsonSchema.NewtonsoftJson/Generation/NewtonsoftJsonReflectionService.cs

@@ -186,11 +186,15 @@ private void LoadPropertyOrField(JsonProperty jsonProperty, ContextualAccessorIn
                     parentSchema.RequiredProperties.Add(propertyName);
                 }
 
-                var isNullable = propertyTypeDescription.IsNullable && !hasRequiredAttribute && jsonProperty.Required is Required.Default or Required.AllowNull;
+                // The C# required keyword marks a property as required in the schema's required array
+                // but does not imply a non-nullable value. Only [Required] carries the semantic meaning
+                // of "non-null value required" and should suppress nullability and trigger MinLength = 1
+                // on strings.
+                var isNullable = propertyTypeDescription.IsNullable && requiredAttribute == null && jsonProperty.Required is Required.Default or Required.AllowNull;
 
                 var defaultValue = jsonProperty.DefaultValue;
 
-                schemaGenerator.AddProperty(parentSchema, accessorInfo, propertyTypeDescription, propertyName, requiredAttribute, hasRequiredAttribute, isNullable, defaultValue, schemaResolver);
+                schemaGenerator.AddProperty(parentSchema, accessorInfo, propertyTypeDescription, propertyName, requiredAttribute, requiredAttribute != null, isNullable, defaultValue, schemaResolver);
             }
         }
 

src/NJsonSchema.Tests/Generation/AttributeGenerationTests.cs

@@ -353,6 +353,28 @@ public void When_property_has_required_keyword_then_it_is_required_in_Newtonsoft
             Assert.Contains("Name", schema.RequiredProperties);
             Assert.DoesNotContain("Optional", schema.RequiredProperties);
         }
+
+#nullable enable
+        public class ClassWithRequiredNullableKeyword
+        {
+            public required string? Name { get; set; }
+            public string? Optional { get; set; }
+        }
+#nullable restore
+
+        [Fact]
+        public void When_property_has_required_keyword_and_nullable_type_then_it_is_required_and_nullable_in_Newtonsoft_schema()
+        {
+            // Act
+            var schema = NewtonsoftJsonSchemaGenerator.FromType<ClassWithRequiredNullableKeyword>();
+
+            // Assert: required keyword adds to required array
+            Assert.Contains("Name", schema.RequiredProperties);
+            Assert.DoesNotContain("Optional", schema.RequiredProperties);
+            // Assert: nullable type is preserved — required keyword alone must not suppress nullability
+            Assert.True(schema.Properties["Name"].IsNullable(SchemaType.JsonSchema));
+            Assert.Null(schema.Properties["Name"].MinLength);
+        }
 #endif
 
 #if NET6_0_OR_GREATER

src/NJsonSchema.Tests/Generation/SystemTextJson/SystemTextJsonTests.cs

@@ -151,6 +151,28 @@ public void When_property_has_required_keyword_then_it_is_required_in_schema()
             Assert.DoesNotContain("Optional", schema.RequiredProperties);
         }
 
+#nullable enable
+        public class ClassWithRequiredNullableKeyword
+        {
+            public required string? Name { get; set; }
+            public string? Optional { get; set; }
+        }
+#nullable restore
+
+        [Fact]
+        public void When_property_has_required_keyword_and_nullable_type_then_it_is_required_and_nullable_in_schema()
+        {
+            // Act
+            var schema = JsonSchema.FromType<ClassWithRequiredNullableKeyword>();
+
+            // Assert: required keyword adds to required array
+            Assert.Contains("Name", schema.RequiredProperties);
+            Assert.DoesNotContain("Optional", schema.RequiredProperties);
+            // Assert: nullable type is preserved — required keyword alone must not suppress nullability
+            Assert.True(schema.Properties["Name"].IsNullable(SchemaType.JsonSchema));
+            Assert.Null(schema.Properties["Name"].MinLength);
+        }
+
         public class ClassWithJsonRequired
         {
             [System.Text.Json.Serialization.JsonRequired]
@@ -168,6 +190,30 @@ public void When_property_has_JsonRequired_then_it_is_required_in_schema()
             Assert.Contains("Name", schema.RequiredProperties);
             Assert.DoesNotContain("Optional", schema.RequiredProperties);
         }
+
+#nullable enable
+        public class ClassWithJsonRequiredNullable
+        {
+            [System.Text.Json.Serialization.JsonRequired]
+            public string? Name { get; set; }
+            public string? Optional { get; set; }
+        }
+#nullable restore
+
+        [Fact]
+        public void When_property_has_JsonRequired_and_nullable_type_then_it_is_required_and_nullable_in_schema()
+        {
+            // Act
+            var schema = JsonSchema.FromType<ClassWithJsonRequiredNullable>();
+
+            // Assert: [JsonRequired] is a presence marker (like the C# required keyword) and matches
+            // System.Text.Json runtime semantics — the property must be present in the JSON, but the
+            // value may be null. Only [Required] (DataAnnotations) implies a non-null value.
+            Assert.Contains("Name", schema.RequiredProperties);
+            Assert.DoesNotContain("Optional", schema.RequiredProperties);
+            Assert.True(schema.Properties["Name"].IsNullable(SchemaType.JsonSchema));
+            Assert.Null(schema.Properties["Name"].MinLength);
+        }
 #endif
 
         public class ClassWithPublicField

src/NJsonSchema/Generation/SystemTextJsonReflectionService.cs

@@ -104,10 +104,14 @@ public override void GenerateProperties(JsonSchema schema, ContextualType contex
                         schema.RequiredProperties.Add(propertyName);
                     }
 
-                    var isNullable = propertyTypeDescription.IsNullable && !hasRequiredAttribute;
+                    // Presence markers (C# required keyword, [JsonRequired], DataMember.IsRequired) only
+                    // mark a property as required in the schema's required array. Only [Required] carries
+                    // the semantic meaning of "non-null value required" and should suppress nullability
+                    // and trigger MinLength = 1 on strings.
+                    var isNullable = propertyTypeDescription.IsNullable && requiredAttribute == null;
 
                     // TODO: Add default value
-                    schemaGenerator.AddProperty(schema, accessorInfo, propertyTypeDescription, propertyName, requiredAttribute, hasRequiredAttribute, isNullable, null, schemaResolver);
+                    schemaGenerator.AddProperty(schema, accessorInfo, propertyTypeDescription, propertyName, requiredAttribute, requiredAttribute != null, isNullable, null, schemaResolver);
                 }
             }
         }