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Summary This paper has introduced &SCons;, a next-generation build tool with a modular, embeddable architecture and a direct Python interface. &SCons; has a global view of the dependencies in a source tree, uses MD5 signatures to decide if derived files are out of date, and automatically scans files for dependencies, all of which make &SCons; builds exceptionally reliable. The &SCons; development methodology has been described, notable for its emphasis on automated regression testing to ensure a robust and reliable tool from day one. Several future directions for &SCons; have also been discussed.