unit-cost-probelisted

# Skill: unit-cost-probe ## Premise A cost per unit is a division, and both sides of it lie easily. The numerator lies through unallocated spend and unamortised commitments; the denominator lies through ambiguity ("per user" is at least three different counts). This skill makes both sides explicit and refuses to produce a figure whose inputs it cannot name. Every output states: the numerator's source and filters, the denominator's source and query, the period, and the label on each branch. ## Halt conditions - **Denominator undefined.** "Per user" is not a denominator; "monthly active users, as counted by `<named metric>`, over the same billing period" is. Refuse until it is named. - **Period mismatch** between numerator and denominator. A cost from a calendar month divided by a count from a trailing-30-day window is not a unit cost. - **Cost/usage export unavailable at row level.** Console summaries cannot be filtered to a branch. - **Shared-cost basis undeclared** when the unit's branches include shared infrastructure. The choice changes the answer materially and belongs to a human. - **Flat-rate capacity environment** — there is no marginal cost. Report share-of-a-fixed-pool instead and label it as such. ## When to run - Someone states a cost per customer, per order, or per request, and it needs verification. - Before a pricing, packaging, or plan-limit decision. - To populate or verify one branch of `/cost-model`'s driver tree independently. - After a change that `