{"abstract":"Repeated scatter targets keep the earliest selected write.","category":"Data systems","checks":8,"contract":"Apply an ordered scatter update to a column using [target-index,value,is-valid,is-selected] records. Unselected writes do nothing; selected null writes clear validity. Repeated targets use the final selected write, and untouched lanes retain both payload visibility and validity.","evaluation_group":"s3-data-systems-masked-scatter-update","failed_approach":"Sorting writes by payload makes unrelated value ordering decide the winner.","family":"s3-data-systems-masked-scatter-update-write-order","id":"FA-45111","implementations":{"attempt":{"sha256":"81e7a2820cfd4e54de292686df0c3879a413c01a182c660e8bed42aac9f6ff9b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(d):\n    try:\n        values,valid,updates=d\n        values=list(values); valid=list(valid)\n        for target,value,known,selected in sorted(updates,key=lambda r:r[1],reverse=True):\n            if not selected: continue\n            values[target]=value\n            valid[target]=known\n        return [v if valid[i] else None for i,v in enumerate(values)]\n    except (IndexError, KeyError, ValueError, StopIteration) as exc:\n        return {\"representation_error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nif N == 1:\n    check('nonzero target', solve([[1, 2, 3], [True, True, True], [[2, 4, True, True]]]), [1, 2, 4])\n    check('masked value', solve([[1, 2], [True, True], [[1, 3, True, False]]]), [1, 2])\n    check('masked null', solve([[1, 2], [True, True], [[1, 3, False, False]]]), [1, 2])\n    check('selected null', solve([[1, 2], [True, True], [[1, 3, False, True]]]), [1, None])\n    check('resurrect null', solve([[1, 2], [True, False], [[1, 3, True, True]]]), [1, 3])\n    check('repeated target', solve([[1, 2], [True, True], [[1, 3, True, True], [1, 4, True, True]]]), [1, 4])\n    check('middle validity', solve([[1, 2, 3], [True, True, True], [[1, 4, False, True]]]), [1, None, 3])\n    check('no writes', solve([[1, 2], [False, True], []]), [None, 2])\nelif N == 2:\n    check('nonzero target', solve([[2, 3, 4], [True, True, True], [[2, 5, True, True]]]), [2, 3, 5])\n    check('masked value', solve([[2, 3], [True, True], [[1, 4, True, False]]]), [2, 3])\n    check('masked null', solve([[2, 3], [True, True], [[1, 4, False, False]]]), [2, 3])\n    check('selected null', solve([[2, 3], [True, True], [[1, 4, False, True]]]), [2, None])\n    check('resurrect null', solve([[2, 3], [True, False], [[1, 4, True, True]]]), [2, 4])\n    check('repeated target', solve([[2, 3], [True, True], [[1, 4, True, True], [1, 5, True, True]]]), [2, 5])\n    check('middle validity', solve([[2, 3, 4], [True, True, True], [[1, 5, False, True]]]), [2, None, 4])\n    check('no writes', solve([[2, 3], [False, True], []]), [None, 3])\nelif N == 3:\n    check('nonzero target', solve([[3, 4, 5], [True, True, True], [[2, 6, True, True]]]), [3, 4, 6])\n    check('masked value', solve([[3, 4], [True, True], [[1, 5, True, False]]]), [3, 4])\n    check('masked null', solve([[3, 4], [True, True], [[1, 5, False, False]]]), [3, 4])\n    check('selected null', solve([[3, 4], [True, True], [[1, 5, False, True]]]), [3, None])\n    check('resurrect null', solve([[3, 4], [True, False], [[1, 5, True, True]]]), [3, 5])\n    check('repeated target', solve([[3, 4], [True, True], [[1, 5, True, True], [1, 6, True, True]]]), [3, 6])\n    check('middle validity', solve([[3, 4, 5], [True, True, True], [[1, 6, False, True]]]), [3, None, 5])\n    check('no writes', solve([[3, 4], [False, True], []]), [None, 4])\nelif N == 4:\n    check('nonzero target', solve([[4, 5, 6], [True, True, True], [[2, 7, True, True]]]), [4, 5, 7])\n    check('masked value', solve([[4, 5], [True, True], [[1, 6, True, False]]]), [4, 5])\n    check('masked null', solve([[4, 5], [True, True], [[1, 6, False, False]]]), [4, 5])\n    check('selected null', solve([[4, 5], [True, True], [[1, 6, False, True]]]), [4, None])\n    check('resurrect null', solve([[4, 5], [True, False], [[1, 6, True, True]]]), [4, 6])\n    check('repeated target', solve([[4, 5], [True, True], [[1, 6, True, True], [1, 7, True, True]]]), [4, 7])\n    check('middle validity', solve([[4, 5, 6], [True, True, True], [[1, 7, False, True]]]), [4, None, 6])\n    check('no writes', solve([[4, 5], [False, True], []]), [None, 5])\nelif N == 5:\n    check('nonzero target', solve([[5, 6, 7], [True, True, True], [[2, 8, True, True]]]), [5, 6, 8])\n    check('masked value', solve([[5, 6], [True, True], [[1, 7, True, False]]]), [5, 6])\n    check('masked null', solve([[5, 6], [True, True], [[1, 7, False, False]]]), [5, 6])\n    check('selected null', solve([[5, 6], [True, True], [[1, 7, False, True]]]), [5, None])\n    check('resurrect null', solve([[5, 6], [True, False], [[1, 7, True, True]]]), [5, 7])\n    check('repeated target', solve([[5, 6], [True, True], [[1, 7, True, True], [1, 8, True, True]]]), [5, 8])\n    check('middle validity', solve([[5, 6, 7], [True, True, True], [[1, 8, False, True]]]), [5, None, 7])\n    check('no writes', solve([[5, 6], [False, True], []]), [None, 6])\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":"7985c42fb10f23464c80aeef0397d78a2bf2ff68e51b08c04982f562471722e5","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(d):\n    try:\n        values,valid,updates=d\n        values=list(values); valid=list(valid)\n        for target,value,known,selected in reversed(updates):\n            if not selected: continue\n            values[target]=value\n            valid[target]=known\n        return [v if valid[i] else None for i,v in enumerate(values)]\n    except (IndexError, KeyError, ValueError, StopIteration) as exc:\n        return {\"representation_error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nif N == 1:\n    check('nonzero target', solve([[1, 2, 3], [True, True, True], [[2, 4, True, True]]]), [1, 2, 4])\n    check('masked value', solve([[1, 2], [True, True], [[1, 3, True, False]]]), [1, 2])\n    check('masked null', solve([[1, 2], [True, True], [[1, 3, False, False]]]), [1, 2])\n    check('selected null', solve([[1, 2], [True, True], [[1, 3, False, True]]]), [1, None])\n    check('resurrect null', solve([[1, 2], [True, False], [[1, 3, True, True]]]), [1, 3])\n    check('repeated target', solve([[1, 2], [True, True], [[1, 3, True, True], [1, 4, True, True]]]), [1, 4])\n    check('middle validity', solve([[1, 2, 3], [True, True, True], [[1, 4, False, True]]]), [1, None, 3])\n    check('no writes', solve([[1, 2], [False, True], []]), [None, 2])\nelif N == 2:\n    check('nonzero target', solve([[2, 3, 4], [True, True, True], [[2, 5, True, True]]]), [2, 3, 5])\n    check('masked value', solve([[2, 3], [True, True], [[1, 4, True, False]]]), [2, 3])\n    check('masked null', solve([[2, 3], [True, True], [[1, 4, False, False]]]), [2, 3])\n    check('selected null', solve([[2, 3], [True, True], [[1, 4, False, True]]]), [2, None])\n    check('resurrect null', solve([[2, 3], [True, False], [[1, 4, True, True]]]), [2, 4])\n    check('repeated target', solve([[2, 3], [True, True], [[1, 4, True, True], [1, 5, True, True]]]), [2, 5])\n    check('middle validity', solve([[2, 3, 4], [True, True, True], [[1, 5, False, True]]]), [2, None, 4])\n    check('no writes', solve([[2, 3], [False, True], []]), [None, 3])\nelif N == 3:\n    check('nonzero target', solve([[3, 4, 5], [True, True, True], [[2, 6, True, True]]]), [3, 4, 6])\n    check('masked value', solve([[3, 4], [True, True], [[1, 5, True, False]]]), [3, 4])\n    check('masked null', solve([[3, 4], [True, True], [[1, 5, False, False]]]), [3, 4])\n    check('selected null', solve([[3, 4], [True, True], [[1, 5, False, True]]]), [3, None])\n    check('resurrect null', solve([[3, 4], [True, False], [[1, 5, True, True]]]), [3, 5])\n    check('repeated target', solve([[3, 4], [True, True], [[1, 5, True, True], [1, 6, True, True]]]), [3, 6])\n    check('middle validity', solve([[3, 4, 5], [True, True, True], [[1, 6, False, True]]]), [3, None, 5])\n    check('no writes', solve([[3, 4], [False, True], []]), [None, 4])\nelif N == 4:\n    check('nonzero target', solve([[4, 5, 6], [True, True, True], [[2, 7, True, True]]]), [4, 5, 7])\n    check('masked value', solve([[4, 5], [True, True], [[1, 6, True, False]]]), [4, 5])\n    check('masked null', solve([[4, 5], [True, True], [[1, 6, False, False]]]), [4, 5])\n    check('selected null', solve([[4, 5], [True, True], [[1, 6, False, True]]]), [4, None])\n    check('resurrect null', solve([[4, 5], [True, False], [[1, 6, True, True]]]), [4, 6])\n    check('repeated target', solve([[4, 5], [True, True], [[1, 6, True, True], [1, 7, True, True]]]), [4, 7])\n    check('middle validity', solve([[4, 5, 6], [True, True, True], [[1, 7, False, True]]]), [4, None, 6])\n    check('no writes', solve([[4, 5], [False, True], []]), [None, 5])\nelif N == 5:\n    check('nonzero target', solve([[5, 6, 7], [True, True, True], [[2, 8, True, True]]]), [5, 6, 8])\n    check('masked value', solve([[5, 6], [True, True], [[1, 7, True, False]]]), [5, 6])\n    check('masked null', solve([[5, 6], [True, True], [[1, 7, False, False]]]), [5, 6])\n    check('selected null', solve([[5, 6], [True, True], [[1, 7, False, True]]]), [5, None])\n    check('resurrect null', solve([[5, 6], [True, False], [[1, 7, True, True]]]), [5, 7])\n    check('repeated target', solve([[5, 6], [True, True], [[1, 7, True, True], [1, 8, True, True]]]), [5, 8])\n    check('middle validity', solve([[5, 6, 7], [True, True, True], [[1, 8, False, True]]]), [5, None, 7])\n    check('no writes', solve([[5, 6], [False, True], []]), [None, 6])\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"},"fixed":{"sha256":"58d89775778376c4728d77c82220a12fdefeca7ebe2c48462ce1da7ccd6be963","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(d):\n    try:\n        values,valid,updates=d\n        values=list(values); valid=list(valid)\n        for target,value,known,selected in updates:\n            if not selected: continue\n            values[target]=value\n            valid[target]=known\n        return [v if valid[i] else None for i,v in enumerate(values)]\n    except (IndexError, KeyError, ValueError, StopIteration) as exc:\n        return {\"representation_error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nif N == 1:\n    check('nonzero target', solve([[1, 2, 3], [True, True, True], [[2, 4, True, True]]]), [1, 2, 4])\n    check('masked value', solve([[1, 2], [True, True], [[1, 3, True, False]]]), [1, 2])\n    check('masked null', solve([[1, 2], [True, True], [[1, 3, False, False]]]), [1, 2])\n    check('selected null', solve([[1, 2], [True, True], [[1, 3, False, True]]]), [1, None])\n    check('resurrect null', solve([[1, 2], [True, False], [[1, 3, True, True]]]), [1, 3])\n    check('repeated target', solve([[1, 2], [True, True], [[1, 3, True, True], [1, 4, True, True]]]), [1, 4])\n    check('middle validity', solve([[1, 2, 3], [True, True, True], [[1, 4, False, True]]]), [1, None, 3])\n    check('no writes', solve([[1, 2], [False, True], []]), [None, 2])\nelif N == 2:\n    check('nonzero target', solve([[2, 3, 4], [True, True, True], [[2, 5, True, True]]]), [2, 3, 5])\n    check('masked value', solve([[2, 3], [True, True], [[1, 4, True, False]]]), [2, 3])\n    check('masked null', solve([[2, 3], [True, True], [[1, 4, False, False]]]), [2, 3])\n    check('selected null', solve([[2, 3], [True, True], [[1, 4, False, True]]]), [2, None])\n    check('resurrect null', solve([[2, 3], [True, False], [[1, 4, True, True]]]), [2, 4])\n    check('repeated target', solve([[2, 3], [True, True], [[1, 4, True, True], [1, 5, True, True]]]), [2, 5])\n    check('middle validity', solve([[2, 3, 4], [True, True, True], [[1, 5, False, True]]]), [2, None, 4])\n    check('no writes', solve([[2, 3], [False, True], []]), [None, 3])\nelif N == 3:\n    check('nonzero target', solve([[3, 4, 5], [True, True, True], [[2, 6, True, True]]]), [3, 4, 6])\n    check('masked value', solve([[3, 4], [True, True], [[1, 5, True, False]]]), [3, 4])\n    check('masked null', solve([[3, 4], [True, True], [[1, 5, False, False]]]), [3, 4])\n    check('selected null', solve([[3, 4], [True, True], [[1, 5, False, True]]]), [3, None])\n    check('resurrect null', solve([[3, 4], [True, False], [[1, 5, True, True]]]), [3, 5])\n    check('repeated target', solve([[3, 4], [True, True], [[1, 5, True, True], [1, 6, True, True]]]), [3, 6])\n    check('middle validity', solve([[3, 4, 5], [True, True, True], [[1, 6, False, True]]]), [3, None, 5])\n    check('no writes', solve([[3, 4], [False, True], []]), [None, 4])\nelif N == 4:\n    check('nonzero target', solve([[4, 5, 6], [True, True, True], [[2, 7, True, True]]]), [4, 5, 7])\n    check('masked value', solve([[4, 5], [True, True], [[1, 6, True, False]]]), [4, 5])\n    check('masked null', solve([[4, 5], [True, True], [[1, 6, False, False]]]), [4, 5])\n    check('selected null', solve([[4, 5], [True, True], [[1, 6, False, True]]]), [4, None])\n    check('resurrect null', solve([[4, 5], [True, False], [[1, 6, True, True]]]), [4, 6])\n    check('repeated target', solve([[4, 5], [True, True], [[1, 6, True, True], [1, 7, True, True]]]), [4, 7])\n    check('middle validity', solve([[4, 5, 6], [True, True, True], [[1, 7, False, True]]]), [4, None, 6])\n    check('no writes', solve([[4, 5], [False, True], []]), [None, 5])\nelif N == 5:\n    check('nonzero target', solve([[5, 6, 7], [True, True, True], [[2, 8, True, True]]]), [5, 6, 8])\n    check('masked value', solve([[5, 6], [True, True], [[1, 7, True, False]]]), [5, 6])\n    check('masked null', solve([[5, 6], [True, True], [[1, 7, False, False]]]), [5, 6])\n    check('selected null', solve([[5, 6], [True, True], [[1, 7, False, True]]]), [5, None])\n    check('resurrect null', solve([[5, 6], [True, False], [[1, 7, True, True]]]), [5, 7])\n    check('repeated target', solve([[5, 6], [True, True], [[1, 7, True, True], [1, 8, True, True]]]), [5, 8])\n    check('middle validity', solve([[5, 6, 7], [True, True, True], [[1, 8, False, True]]]), [5, None, 7])\n    check('no writes', solve([[5, 6], [False, True], []]), [None, 6])\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":"Offline stipulated semantics over valid small inputs; no performance, concurrency, or production-engine conformance claim. 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":"s3-data-systems-masked-scatter-update-write-order","generated_at":"2026-09-29T14:44:18.892105+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A bounded deterministic data engine model makes representation and changelog faults reproducible.","repair":"Preserve the stated physical representation and operation order: Apply an ordered scatter update to a column using [target-index,value,is-valid,is-selected] records. Unselected writes do nothing; selected null writes clear validity. Repeated targets use the final selected write, and untouched lanes retain both payload visibility and validity.","root_cause":"masked-scatter-update: Repeated scatter targets keep the earliest selected write.","sha256":"7b6916fd1bc3833c113227b674537d19cb751426d0ae9a8ae019229ee0b4e212","title":"Repeated scatter targets keep the earliest selected write · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":43.404,"exit_code":1,"observations":[{"actual":[1,2,4],"check":"nonzero target","expected":[1,2,4],"passed":true},{"actual":[1,2],"check":"masked value","expected":[1,2],"passed":true},{"actual":[1,2],"check":"masked null","expected":[1,2],"passed":true},{"actual":[1,null],"check":"selected null","expected":[1,null],"passed":true},{"actual":[1,3],"check":"resurrect null","expected":[1,3],"passed":true},{"actual":[1,3],"check":"repeated target","expected":[1,4],"passed":false},{"actual":[1,null,3],"check":"middle validity","expected":[1,null,3],"passed":true},{"actual":[null,2],"check":"no writes","expected":[null,2],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"nonzero target\", \"actual\": [1, 2, 4], \"expected\": [1, 2, 4], \"passed\": true}, {\"check\": \"masked value\", \"actual\": [1, 2], \"expected\": [1, 2], \"passed\": true}, {\"check\": \"masked null\", \"actual\": [1, 2], \"expected\": [1, 2], \"passed\": true}, {\"check\": \"selected null\", \"actual\": [1, null], \"expected\": [1, null], \"passed\": true}, {\"check\": \"resurrect null\", \"actual\": [1, 3], \"expected\": [1, 3], \"passed\": true}, {\"check\": \"repeated target\", \"actual\": [1, 3], \"expected\": [1, 4], \"passed\": false}, {\"check\": \"middle validity\", \"actual\": [1, null, 3], \"expected\": [1, null, 3], \"passed\": true}, {\"check\": \"no writes\", \"actual\": [null, 2], \"expected\": [null, 2], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":47.118,"exit_code":1,"observations":[{"actual":[1,2,4],"check":"nonzero target","expected":[1,2,4],"passed":true},{"actual":[1,2],"check":"masked value","expected":[1,2],"passed":true},{"actual":[1,2],"check":"masked null","expected":[1,2],"passed":true},{"actual":[1,null],"check":"selected null","expected":[1,null],"passed":true},{"actual":[1,3],"check":"resurrect null","expected":[1,3],"passed":true},{"actual":[1,3],"check":"repeated target","expected":[1,4],"passed":false},{"actual":[1,null,3],"check":"middle validity","expected":[1,null,3],"passed":true},{"actual":[null,2],"check":"no writes","expected":[null,2],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"nonzero target\", \"actual\": [1, 2, 4], \"expected\": [1, 2, 4], \"passed\": true}, {\"check\": \"masked value\", \"actual\": [1, 2], \"expected\": [1, 2], \"passed\": true}, {\"check\": \"masked null\", \"actual\": [1, 2], \"expected\": [1, 2], \"passed\": true}, {\"check\": \"selected null\", \"actual\": [1, null], \"expected\": [1, null], \"passed\": true}, {\"check\": \"resurrect null\", \"actual\": [1, 3], \"expected\": [1, 3], \"passed\": true}, {\"check\": \"repeated target\", \"actual\": [1, 3], \"expected\": [1, 4], \"passed\": false}, {\"check\": \"middle validity\", \"actual\": [1, null, 3], \"expected\": [1, null, 3], \"passed\": true}, {\"check\": \"no writes\", \"actual\": [null, 2], \"expected\": [null, 2], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":46.132,"exit_code":0,"observations":[{"actual":[1,2,4],"check":"nonzero target","expected":[1,2,4],"passed":true},{"actual":[1,2],"check":"masked value","expected":[1,2],"passed":true},{"actual":[1,2],"check":"masked null","expected":[1,2],"passed":true},{"actual":[1,null],"check":"selected null","expected":[1,null],"passed":true},{"actual":[1,3],"check":"resurrect null","expected":[1,3],"passed":true},{"actual":[1,4],"check":"repeated target","expected":[1,4],"passed":true},{"actual":[1,null,3],"check":"middle validity","expected":[1,null,3],"passed":true},{"actual":[null,2],"check":"no writes","expected":[null,2],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"nonzero target\", \"actual\": [1, 2, 4], \"expected\": [1, 2, 4], \"passed\": true}, {\"check\": \"masked value\", \"actual\": [1, 2], \"expected\": [1, 2], \"passed\": true}, {\"check\": \"masked null\", \"actual\": [1, 2], \"expected\": [1, 2], \"passed\": true}, {\"check\": \"selected null\", \"actual\": [1, null], \"expected\": [1, null], \"passed\": true}, {\"check\": \"resurrect null\", \"actual\": [1, 3], \"expected\": [1, 3], \"passed\": true}, {\"check\": \"repeated target\", \"actual\": [1, 4], \"expected\": [1, 4], \"passed\": true}, {\"check\": \"middle validity\", \"actual\": [1, null, 3], \"expected\": [1, null, 3], \"passed\": true}, {\"check\": \"no writes\", \"actual\": [null, 2], \"expected\": [null, 2], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}