Postconditions / Runtime Cost
Kind: tension
Record: tension:postconditions-runtime-cost
Canonical: Schema
"postconditions" (contracts-core layer) is traded against "Runtime Cost" (contracts-core layer) — a principle cannot be scope-separated from a quality, metric, or cost it competes with; resolve by measuring "Runtime Cost" and choosing an explicit operating point.
Listed in Tensions, after Preconditions / Permissive APIs and before Invariant / Flexibility.