Model Router Core rule: Prefer NONE or one primary skill. Route by mechanism fit, not habit. Combine only when roles are distinct and necessary. When to Use - The right thinking skill is unclear and you would otherwise guess or stack tools. - Several catalog skills seem plausible and you need a single primary (or explicit NONE). - High-stakes work where a wrong frame is costly and a quick domain×type match helps. When NOT to Use - The match is already known or obvious ("where's the bottleneck?" → theory-of-constraints) — invoke that skill directly; do not route for show. - The task is routine…