Tweag is a software innovation lab that helps deep tech startups quickly scale their engineering performance and execute on high-risk, high-reward projects with confidence. We find the best wherever they live, to build better software by applying mathematics, computer science and the methods of open source. Our core engineering mantras: functional, typed, immutable. These are the key technologies for composable software. We build parts as functions, because functions compose where objects do not. We use types to describe functions, because one type is worth a thousand out-of-date comments. We keep data immutable, because immutability lets us focus on the business logic holistically without getting bogged down by hundreds of corner cases. Tweag is a major proponent and contributor to new ways of building composable software. We are active contributors to GHC, have full-time researchers on staff to fund new language features (like linear types and dependent types), instigated the creation of the Haskell Foundation, and created many new libraries and tools in Haskell. We are the top contributors to Nix and were the first to be labeled Bazel Community Expert, because we’re passionate about the impact of great developer tools.