Jev Router Plugin (migrated from Pi ecosystem jev-router.ts).

Dynamic model cascading and phase-based routing:

• Planning Phase: Routes to a high-reasoning frontier model (planning_model, e.g. gemini-3.1-pro-preview) while the agent is exploring, inspecting, and formulating architectural plans.
• Implementation Phase: Once the first write or edit tool is executed, automatically cascades the session to a fast, cost-effective model (implementation_model, e.g. gemini-3-flash-preview).

Reduces end-to-end token expenditure by 60–80% without sacrificing planning depth.

Configuration Options (ctx[:config] or harness tuple):

• :planning_model - Model identifier for planning phase.
• :implementation_model - Model identifier for implementation phase.
• :edit_tools - List of tool names that trigger transition to implementation phase (default: ["write", "edit"]).
• Environment variables: JEV_PLANNING_MODEL, JEV_IMPLEMENTATION_MODEL.