Build Tools compile, link, package, and test source code deterministically, producing the artifacts that CI/CD pipelines and runtime environments consume. Core capabilities include dependency graph analysis, incremental and remote build caching, parallel task execution, monorepo awareness (task filtering based on changed code), cross-language and polyglot builds, and deterministic output verification. The category splits between language-native build tools (Gradle for JVM, Maven for Java, SBT for Scala), monorepo-scale polyglot tools (Bazel, Buck2, Pants), and JS/TS monorepo tools (Nx, Turborepo, Rush). Modern tools emphasize correctness and cache-hit rate at scale, enabling large teams to share a single repository without unacceptable build times.