SharedCode.Core/Xml/XDocumentExtensions.cs:53

• GetXmlSerializer currently takes a global lock for every call, including the cached fast-path. On a hot path under concurrency this can become a bottleneck and may partially negate the benefit of caching. Consider switching to a ConcurrentDictionary (optionally storing Lazy<XmlSerializer> values) so cached lookups are lock-free and serializer creation is still single-instance per type.

        lock (XmlSerializers)
        {
            if (XmlSerializers.TryGetValue(type.TypeHandle, out var serializer))
            {
                return serializer;
            }

            serializer = new XmlSerializer(type);
            XmlSerializers.Add(type.TypeHandle, serializer);

            return serializer;
        }

SharedCode.Core/Xml/XDocumentExtensions.cs:14

• The new cached-serializer field is indented with spaces, but the rest of this file (and most of the repo) uses tabs for indentation. Please re-indent the new block to match the existing style to keep formatting consistent.

    /// <summary>
    /// Cached XML serializers by runtime type.
    /// </summary>
    private static readonly Dictionary<RuntimeTypeHandle, XmlSerializer> XmlSerializers = [];

SharedCode.Core/Xml/XDocumentExtensions.cs:27

• This introduces a second XmlSerializer cache implementation; there is already very similar XmlSerializers + GetXmlSerializer(Type) logic in SharedCode.Core/Extensions.cs (e.g., around lines 18 and 450+). To avoid duplicated logic and potentially divergent behavior over time, consider factoring the serializer cache into a shared internal helper that both call sites can reuse.

		var xmlSerializer = GetXmlSerializer(typeof(T));