{"abstract":"Only positive overflow is bounded.","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. Cap a+b to [-2**(bits-1),2**(bits-1)-1]. Exact operational definition: max(-(1<<(bits-1)), min((1<<(bits-1))-1,a+b))","contract_signature":"a, b, bits","evaluation_group":"model-e752fc2d00476777","failed_approach":"A symmetric bound excludes the representable negative endpoint.","family":"xn-signed-saturating-addition","id":"FA-5381","implementations":{"attempt":{"sha256":"78ef09f17a52bb08b8616c6b687bbc2816db4c0c3e16612157ec818743d44572","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 max(-(1<<(bits-1))+1, min((1<<(bits-1))-1,a+b))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: (-120, -20, 8)', solve(*(-120, -20, 8)), -128)\ncheck('fixture 2: (120, 20, 8)', solve(*(120, 20, 8)), 127)\ncheck('fixture 3: (1, -1, 8)', solve(*(1, -1, 8)), 0)\ncheck('fixture 4: (-128, 0, 8)', solve(*(-128, 0, 8)), -128)\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":"e9494df1baed8880a25e2734a61bc99b4e72abc1035337d9a9997f9a6ef0bdb8","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-1))-1,a+b)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: (-120, -20, 8)', solve(*(-120, -20, 8)), -128)\ncheck('fixture 2: (120, 20, 8)', solve(*(120, 20, 8)), 127)\ncheck('fixture 3: (1, -1, 8)', solve(*(1, -1, 8)), 0)\ncheck('fixture 4: (-128, 0, 8)', solve(*(-128, 0, 8)), -128)\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-signed-saturating-addition","generated_at":"2026-09-29T14:37:48.713471+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":"Only positive overflow is bounded.","sha256":"889410c3a0767795c7232384b3f4911575678187a0dcf134f62a408b475cb54a","title":"Signed 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":46.757,"exit_code":1,"observations":[{"actual":-127,"check":"fixture 1: (-120, -20, 8)","expected":-128,"passed":false},{"actual":127,"check":"fixture 2: (120, 20, 8)","expected":127,"passed":true},{"actual":0,"check":"fixture 3: (1, -1, 8)","expected":0,"passed":true},{"actual":-127,"check":"fixture 4: (-128, 0, 8)","expected":-128,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: (-120, -20, 8)\", \"actual\": -127, \"expected\": -128, \"passed\": false}, {\"check\": \"fixture 2: (120, 20, 8)\", \"actual\": 127, \"expected\": 127, \"passed\": true}, {\"check\": \"fixture 3: (1, -1, 8)\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 4: (-128, 0, 8)\", \"actual\": -127, \"expected\": -128, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.435,"exit_code":1,"observations":[{"actual":-140,"check":"fixture 1: (-120, -20, 8)","expected":-128,"passed":false},{"actual":127,"check":"fixture 2: (120, 20, 8)","expected":127,"passed":true},{"actual":0,"check":"fixture 3: (1, -1, 8)","expected":0,"passed":true},{"actual":-128,"check":"fixture 4: (-128, 0, 8)","expected":-128,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: (-120, -20, 8)\", \"actual\": -140, \"expected\": -128, \"passed\": false}, {\"check\": \"fixture 2: (120, 20, 8)\", \"actual\": 127, \"expected\": 127, \"passed\": true}, {\"check\": \"fixture 3: (1, -1, 8)\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 4: (-128, 0, 8)\", \"actual\": -128, \"expected\": -128, \"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."}}