Fixed

src/WireMock.Net.Minimal/Matchers/CompositeMatcher.cs

@@ -0,0 +1,46 @@
+// Copyright © WireMock.Net
+
+using System;
+
+namespace WireMock.Matchers;
+
+/// <summary>
+/// Represents a matcher that combines multiple matching strategies into a single composite operation.
+/// </summary>
+public class CompositeMatcher : IMatcher
+{
+    /// <inheritdoc />
+    public string Name => nameof(CompositeMatcher);
+
+    /// <summary>
+    /// The logical operator used to combine the results of the matchers.
+    /// </summary>
+    public MatchOperator MatchOperator { get; }
+
+    /// <inheritdoc />
+    public MatchBehaviour MatchBehaviour { get; }
+
+    /// <summary>
+    /// All matchers.
+    /// </summary>
+    public IMatcher[] Matchers { get; }
+
+    /// <summary>
+    /// Initializes a new instance of the CompositeMatcher class with the specified matchers, operator, and match behaviour.
+    /// </summary>
+    /// <param name="matchers">An array of matchers to be combined. Cannot be null or contain null elements.</param>
+    /// <param name="matchOperator">The logical operator used to combine the results of the matchers.</param>
+    /// <param name="matchBehaviour">The behaviour that determines how the composite matcher interprets the combined results.</param>
+    public CompositeMatcher(IMatcher[] matchers, MatchOperator matchOperator, MatchBehaviour matchBehaviour)
+    {
+        Matchers = matchers;
+        MatchOperator = matchOperator;
+        MatchBehaviour = matchBehaviour;
+    }
+
+    /// <inheritdoc />
+    public string GetCSharpCodeArguments()
+    {
+        throw new NotImplementedException();
+    }
+}

src/WireMock.Net.Minimal/Matchers/Request/RequestMessageMultiPartMatcher.cs

@@ -12,6 +12,11 @@ namespace WireMock.Matchers.Request;
 /// </summary>
 public class RequestMessageMultiPartMatcher : IRequestMatcher
 {
+    /// <summary>
+    /// The name of this matcher.
+    /// </summary>
+    public const string MatcherName = "MultiPartMatcher";
+
     private readonly IMimeKitUtils _mimeKitUtils = LoadMimeKitUtils();
 
     /// <summary>
@@ -22,7 +27,7 @@ public class RequestMessageMultiPartMatcher : IRequestMatcher
     /// <summary>
     /// The <see cref="MatchOperator"/>
     /// </summary>
-    public MatchOperator MatchOperator { get; } = MatchOperator.Or;
+    public MatchOperator MatchOperator { get; } = MatchOperator.And;
 
     /// <summary>
     /// The <see cref="MatchBehaviour"/>

src/WireMock.Net.Minimal/Owin/MappingMatcher.cs

@@ -27,6 +27,11 @@ internal class MappingMatcher(IWireMockMiddlewareOptions options, IRandomizerDou
 
         foreach (var mapping in mappings)
         {
+            if (mapping.Guid == new Guid("b9c82182-e469-41da-bcaf-b6e3157fefdb") || mapping.Guid == new Guid("b9c82182-e469-41da-bcaf-b6e3157fefdc"))
+            {
+                int x = 9;
+            }
+
             try
             {
                 var nextState = GetNextState(mapping);

src/WireMock.Net.Minimal/RequestBuilders/Request.WithMultiPart.cs

@@ -15,7 +15,7 @@ public partial class Request
     }
 
     /// <inheritdoc />
-    public IRequestBuilder WithMultiPart(IMatcher[] matchers, MatchBehaviour matchBehaviour = MatchBehaviour.AcceptOnMatch, MatchOperator matchOperator = MatchOperator.Or)
+    public IRequestBuilder WithMultiPart(IMatcher[] matchers, MatchBehaviour matchBehaviour = MatchBehaviour.AcceptOnMatch, MatchOperator matchOperator = MatchOperator.And)
     {
         _requestMatchers.Add(new RequestMessageMultiPartMatcher(matchBehaviour, matchOperator, matchers));
         return this;

src/WireMock.Net.Minimal/Serialization/MatcherMapper.cs

@@ -25,9 +25,9 @@ internal class MatcherMapper
         _settings = Guard.NotNull(settings);
     }
 
-    public IMatcher[]? Map(IEnumerable<MatcherModel>? matchers)
+    public IMatcher[] Map(IEnumerable<MatcherModel>? matchers)
     {
-        return matchers?.Select(Map).OfType<IMatcher>().ToArray();
+        return matchers?.Select(Map).OfType<IMatcher>().ToArray() ?? [];
     }
 
     public IMatcher? Map(MatcherModel? matcherModel)

src/WireMock.Net.Minimal/Server/WireMockServer.ConvertMapping.cs

@@ -6,6 +6,7 @@ using System.Linq;
 using Stef.Validation;
 using WireMock.Admin.Mappings;
 using WireMock.Matchers;
+using WireMock.Matchers.Request;
 using WireMock.RequestBuilders;
 using WireMock.ResponseBuilders;
 using WireMock.Serialization;
@@ -253,7 +254,15 @@ public partial class WireMockServer
         else if (requestModel.Body?.Matchers != null)
         {
             var matchOperator = StringUtils.ParseMatchOperator(requestModel.Body.MatchOperator);
-            requestBuilder = requestBuilder.WithBody(_matcherMapper.Map(requestModel.Body.Matchers)!, matchOperator);
+
+            if (requestModel.Body.MatcherName == RequestMessageMultiPartMatcher.MatcherName)
+            {
+                requestBuilder = requestBuilder.WithMultiPart(_matcherMapper.Map(requestModel.Body.Matchers), matchOperator: matchOperator);
+            }
+            else
+            {
+                requestBuilder = requestBuilder.WithBody(_matcherMapper.Map(requestModel.Body.Matchers), matchOperator);
+            }
         }
 
         return requestBuilder;