November 2026 Summaries

TypeSafe distinguishes Jev as a “System One” model rather than a decision model, drawing on Daniel Kahneman’s concept of fast, intuitive thinking to emphasize Jev’s role in making narrow judgments rather than determining whole business outcomes. It argues that systems should separate semantic questions that require model judgment, such as whether a customer reports an unauthorized charge or requests a refund, from deterministic facts and business rules that conventional code can calculate and enforce. Using a customer-support routing example, the piece warns that asking one model prompt to select a final action can lead to increasingly complex criteria and difficult-to-maintain “prompt gymnastics.” In contrast, decomposing workflows into isolated judgments combined through explicit code-based logic is presented as improving design clarity, operational observability, and extensibility: traces can reveal which judgment or rule caused an outcome, and new routes can be added without disrupting previously validated judgments.