We introduce ƛ (“lambda-barrier”), a minimal extension of linear λ-calculus with concurrent communication, which adds only a single new fork construct for spawning threads. It is inspired by GV, a session-typed functional language that is also based on linear λ-calculus. Unlike GV, ƛ strives to be as simple as possible, and adds no new operations other than fork, no new type formers, and no explicit definition of session type duality. Instead, we use the linear function type τ₁ → τ₂ for communication between threads, which is dual to τ₂ → τ₁, i.e. the function type constructor is dual to itself. Nevertheless, we can encode session types as ƛ types, GV’s channel operations as ƛ terms, and show that this encoding is type-preserving. The linear type system of ƛ ensures that all programs are deadlock-free and satisfy global progress, which we prove in Coq. Because of ƛ’s minimality, these proofs are simpler and shorter than mechanized proofs of deadlock freedom for GV.