What problem does it solve? Running every step of a multi-step prompt composition on the most expensive model tier wastes budget, but downgrading blindly risks compounding quality loss. This Skill finds the cheapest model-heterogeneous assignment that statistically ties the all-opus composition end-to-end. ## Core Features & Use Cases - All-opus reference measurement: Runs the composition once at all-opus across eval cases and seeds to establish the quality baseline. - Verify-escalate loop: Starts from a floor assignment derived from per-step tier-profiles, then escalates individual steps to higher tiers whenever compounding loss is detected. - Statistical decision CLI: Uses the tier-assemble CLI to emit decisions (need_seeds, escalate, ship, stop) with epsilon-based equivalence testing, and writes a frozen composition-tier-profile.json plus a report. - Use Case: After certifying per-step tier profiles with the tier-ladder skill, ask to "tier the composition" to get the cheapest safe mix of haiku, sonnet, and opus across steps. ## Quick Start Tier the composition to assemble the cheapest model assignment that still ties the all-opus baseline end-to-end.