The 4.0.0 release of SqlFluff, dated January 15, 2026, introduces key enhancements, notably the integration of Rust optimizations. Users can now opt into Rust support by installing sqlfluff[rs]. This change aims to improve performance, especially with large files and projects, although smaller files may experience slight slowdowns due to data transfer overhead. The Rust implementation has shown stability during testing, and it is expected to become the default in version 5.0. Testing in a development environment before deployment is recommended. The release also marks the end of support for dbt versions 1.4 and older, while adding compatibility for dbt 1.10. New features include the ability to enforce implicit indents and a variety of bug fixes. Notable changes involve support for various SQL statements across multiple databases, such as creating and dropping synonyms in Oracle and enhancements to T-SQL features. The update includes significant contributions from new developers, expanding the collaborative effort behind SqlFluff.