Vault 1.9 introduces several key features and improvements, including support for Vault as an OpenID Connect (OIDC) provider, enhancements to the Transform data transformation feature, and updates to the key management secrets engine for Google Cloud. The release also includes new features such as transparent data encryption for Microsoft SQL Server, a patch secrets ability for creating new versions of existing secrets without reading their contents, and support for user-defined custom HTTP response headers. Additionally, Vault 1.9 improves its UI and client count display, and adds new workflow enhancements and bug fixes. The release is now generally available, and users can access the detailed changelog and Learn Guides for more information on how to use these features.