01
A call in, immutable data out
A call receives immutable problem data and returns immutable placements, alternatives, diagnostics and algorithm metadata. There is no service to run, no database to migrate and no framework to adopt.
02
Commerce is a leaf, not a dependency
Carrier rating, policy evaluation and catalog versioning import nothing from the solver layers, and nothing in those layers imports them, so a quote cannot reach into a solver and a solver cannot come to depend on a tariff.
03
Determinism is a boundary, not a setting
Search is bounded by explicit deadlines, effort budgets counted in operations rather than wall clock, and a seed. Nothing inside the engine acquires a network call, a clock or a retry.