{"id":"combiner-not-type-checked","text":"The combiner's callable signature matches the reducer's, but no runtime or static check verifies associativity or commutativity — a non-associative combiner (e.g., average) produces silently wrong results that vary with `num_mappers`","truth_value":"IN","source":"entries/2026/05/29/topic-combiner-correctness.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"explanation":{"steps":[{"node":"combiner-not-type-checked","truth_value":"IN","reason":"premise"}]}}