{"abstract":"Overflow wraps instead of saturating.","category":"Integer arithmetic","checks":4,"contract":"Integer arguments; denominators, steps, moduli, and bit widths are positive. Unsigned word inputs fit the specified width except where masking is explicitly the operation. Sequence sizes are nonnegative. a and b are nonnegative; cap their sum at 2**bits-1. Exact operational definition: min((1<<bits)-1, a+b)","contract_signature":"a, b, bits","evaluation_group":"model-498a6594ef485c01","failed_approach":"The saturation ceiling includes an unrepresentable endpoint.","family":"xn-unsigned-saturating-addition","id":"FA-5371","implementations":{"attempt":{"sha256":"fc7816ea01487808b789445c3ec95b600399f7adccf42466d1129e006dcd49e7","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(a, b, bits):\n    return min(1<<bits, a+b)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: (250, 10, 8)', solve(*(250, 10, 8)), 255)\ncheck('fixture 2: (2, 3, 8)', solve(*(2, 3, 8)), 5)\ncheck('fixture 3: (0, 0, 1)', solve(*(0, 0, 1)), 0)\ncheck('fixture 4: (1, 1, 1)', solve(*(1, 1, 1)), 1)\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":"d38aaef3ef5fc837ed7f011531085828d9d87b296a137b55537f382be4605c45","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(a, b, bits):\n    return (a+b)% (1<<bits)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: (250, 10, 8)', solve(*(250, 10, 8)), 255)\ncheck('fixture 2: (2, 3, 8)', solve(*(2, 3, 8)), 5)\ncheck('fixture 3: (0, 0, 1)', solve(*(0, 0, 1)), 0)\ncheck('fixture 4: (1, 1, 1)', solve(*(1, 1, 1)), 1)\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":" 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":"xn-unsigned-saturating-addition","generated_at":"2026-09-29T14:37:48.632177+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Small exact fixtures expose this error without platform timing, external services, or probabilistic observations. Integer mathematics results depend on the stated convention.","root_cause":"Overflow wraps instead of saturating.","sha256":"dcc39f74aa23c6508fbc0723d97c16d744440f8cfceed26b06c6050656b71436","title":"Unsigned saturating addition · 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":40.153,"exit_code":1,"observations":[{"actual":256,"check":"fixture 1: (250, 10, 8)","expected":255,"passed":false},{"actual":5,"check":"fixture 2: (2, 3, 8)","expected":5,"passed":true},{"actual":0,"check":"fixture 3: (0, 0, 1)","expected":0,"passed":true},{"actual":2,"check":"fixture 4: (1, 1, 1)","expected":1,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: (250, 10, 8)\", \"actual\": 256, \"expected\": 255, \"passed\": false}, {\"check\": \"fixture 2: (2, 3, 8)\", \"actual\": 5, \"expected\": 5, \"passed\": true}, {\"check\": \"fixture 3: (0, 0, 1)\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 4: (1, 1, 1)\", \"actual\": 2, \"expected\": 1, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":48.289,"exit_code":1,"observations":[{"actual":4,"check":"fixture 1: (250, 10, 8)","expected":255,"passed":false},{"actual":5,"check":"fixture 2: (2, 3, 8)","expected":5,"passed":true},{"actual":0,"check":"fixture 3: (0, 0, 1)","expected":0,"passed":true},{"actual":0,"check":"fixture 4: (1, 1, 1)","expected":1,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: (250, 10, 8)\", \"actual\": 4, \"expected\": 255, \"passed\": false}, {\"check\": \"fixture 2: (2, 3, 8)\", \"actual\": 5, \"expected\": 5, \"passed\": true}, {\"check\": \"fixture 3: (0, 0, 1)\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 4: (1, 1, 1)\", \"actual\": 0, \"expected\": 1, \"passed\": false}], \"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."}}