10 Levels of Jev: from Smart IFs to self-directing agents with system-one models

IndyDevDan · youtube · 2026-09-28

IndyDevDan walks through 10 levels of using TypeSafe's Jev — a JSON-programmed "system one model" for narrow decisions — alongside coding agents, with an open-source repo.

Core idea: keep the coding agent for hard work, delegate narrow decisions to a single-purpose model.

Levels cover: prompt-injection yes/no checks, multiple-choice triage, composite scoring of tickets/review risk, confidence gating for bash commands, model/agent/workflow routing, pre-tool guardrail hooks in a Pi coding agent, auto-compact decisions, dirt-cheap file reads without loading files into agent context, multi-file recursive glob questions, and the agent choosing its own Jev questions to classify test failures.

Takeaway: don't default to the biggest model — define the decision, pick the right tool, inspect confidence, validate on your production workload.

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