{"abstract":"Cluster randomization accepts contradictory unit assignments.","category":"Causal analysis data contracts","checks":6,"contract":"Rows [cluster,arm] use arms 0 and 1. Return sorted clusters violating the cluster-level assignment design.","contract_signature":"rows","evaluation_group":"model-cd94a634e35ebb0c","failed_approach":"Majority vote masks minority contradictions.","family":"z-causal_inference-cluster-integrity","id":"FA-12661","implementations":{"attempt":{"sha256":"9b804499f46999c881cc63da501c084a3afc8f2c35ef8d5117f945595d362e9e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(rows):\n    clusters = {c for c,a in rows}\n    return sorted(c for c in clusters if sum(a for k,a in rows if k == c)*2 == sum(k == c for k,a in rows))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('unequal conflict', solve([['a',0]]*(N+1)+[['a',1]]), ['a'])\ncheck('balanced conflict', solve([['a',0],['a',1]]), ['a'])\ncheck('all treated', solve([['a',1]]*N), [])\ncheck('all control', solve([['a',0]]*N), [])\ncheck('two clusters', solve([['a',0],['b',1]]), [])\ncheck('empty', solve([]), [])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"06144e31a0f7998b711e71cd52e76b99205e3e5fd45df9c82ab5dffd68cfe89f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(rows):\n    return []\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('unequal conflict', solve([['a',0]]*(N+1)+[['a',1]]), ['a'])\ncheck('balanced conflict', solve([['a',0],['a',1]]), ['a'])\ncheck('all treated', solve([['a',1]]*N), [])\ncheck('all control', solve([['a',0]]*N), [])\ncheck('two clusters', solve([['a',0],['b',1]]), [])\ncheck('empty', solve([]), [])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"Finite, fully specified synthetic data only; identification assumptions are supplied by the fixture design, not inferred from observations. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"z-causal_inference-cluster-integrity","generated_at":"2026-09-29T14:38:58.834900+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic synthetic study model isolates this data-contract defect; outputs alone establish no real-world causal identification.","root_cause":"A cluster is treated as a set of independent unit assignments.","sha256":"ce4838fc3bfe931ec71221f5377ee4293480a50df8233cf1478e28333b0bd4bd","title":"Cluster randomization accepts contradictory unit assignments · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":44.584,"exit_code":1,"observations":[{"actual":[],"check":"unequal conflict","expected":["a"],"passed":false},{"actual":["a"],"check":"balanced conflict","expected":["a"],"passed":true},{"actual":[],"check":"all treated","expected":[],"passed":true},{"actual":[],"check":"all control","expected":[],"passed":true},{"actual":[],"check":"two clusters","expected":[],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"unequal conflict\", \"actual\": [], \"expected\": [\"a\"], \"passed\": false}, {\"check\": \"balanced conflict\", \"actual\": [\"a\"], \"expected\": [\"a\"], \"passed\": true}, {\"check\": \"all treated\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"all control\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"two clusters\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.287,"exit_code":1,"observations":[{"actual":[],"check":"unequal conflict","expected":["a"],"passed":false},{"actual":[],"check":"balanced conflict","expected":["a"],"passed":false},{"actual":[],"check":"all treated","expected":[],"passed":true},{"actual":[],"check":"all control","expected":[],"passed":true},{"actual":[],"check":"two clusters","expected":[],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"unequal conflict\", \"actual\": [], \"expected\": [\"a\"], \"passed\": false}, {\"check\": \"balanced conflict\", \"actual\": [], \"expected\": [\"a\"], \"passed\": false}, {\"check\": \"all treated\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"all control\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"two clusters\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}