The XML/DOM parsing library has been replaced. The previous xmldom-based parser (with error messages like "end tag name: X is not complete", "unclosed xml attribute", etc.) has been swapped for a new implementation with W3C-compliant DOM exceptions (DOMException types like HierarchyRequestError, InvalidCharacterError, NamespaceError, etc.) and stricter validation. This is an internal change but may surface different error messages if XML parsing is used by MCP servers or plugins.

Several Smithy/AWS SDK utility modules (FetchHttpHandler, buildQueryString, escapeUri, fromBase64, toBase64, etc.) have been removed as standalone CommonJS modules and replaced by native implementations, reducing bundle size.