Service-Layer Style (T3 Turbo)

Portable style guide for the packages/api/src/services/** layer in T3 Turbo monorepos (Next.js App Router + tRPC v11 + Drizzle + Neon Postgres). Applies to any T3 project — not framework-specific. The goal is a service layer that is typesafe, testable, observable, and free of this.x! traps.

Invariant: ServiceCtx

Every service function takes a ServiceCtx as its first argument. Not this, not a global, not a hidden import. Explicit parameter, typed once.