{"abstract":"Padding bits are decoded as extra compressed symbols.","category":"Compression format semantics","checks":6,"contract":"Decode exactly count one-bit symbols from integer bytes in LSB order. Count is valid and padding is ignored.","contract_signature":"data, count","evaluation_group":"model-d0b05f656c072c5b","failed_approach":"Removing trailing zeros also removes valid final zero symbols.","family":"z-compression-padding-not-symbols","id":"FA-11616","implementations":{"attempt":{"sha256":"4a6f74b12131ccb69666a4251a23af3d1ded0ee90b4c91d4ba21d609ea975d80","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(data, count):\n    bits=[(v>>j)&1 for v in data for j in range(8)]\n    while bits and bits[-1]==0: bits.pop()\n    return bits\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('valid zero suffix',solve([1],N+1),[1]+[0]*N)\ncheck('no symbols',solve([],0),[])\ncheck('padding can be set',solve([255],1),[1])\ncheck('whole byte',solve([255],8),[1]*8)\ncheck('all zero symbols',solve([0],3),[0,0,0])\ncheck('cross byte',solve([255,1],9),[1]*9)\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":"16ba8a322939c1fa867c4b4bc1d4384215fd1959ad006fdc74bae22a5f4274b2","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(data, count):\n    return [(v>>j)&1 for v in data for j in range(8)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('valid zero suffix',solve([1],N+1),[1]+[0]*N)\ncheck('no symbols',solve([],0),[])\ncheck('padding can be set',solve([255],1),[1])\ncheck('whole byte',solve([255],8),[1]*8)\ncheck('all zero symbols',solve([0],3),[0,0,0])\ncheck('cross byte',solve([255,1],9),[1]*9)\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":"Controlled educational model, not a complete implementation of a production compression format. 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-compression-padding-not-symbols","generated_at":"2026-09-29T14:38:49.503082+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A small offline codec model isolates a compression-specific failure without external files or libraries.","root_cause":"A decoder returns every physical bit instead of the declared logical symbol count.","sha256":"4d89466eeacf654136b4ead358c4bd097b17f01a5f7f7a0accf264afdbbf10a7","title":"Padding bits are decoded as extra compressed symbols · 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":40.757,"exit_code":1,"observations":[{"actual":[1],"check":"valid zero suffix","expected":[1,0],"passed":false},{"actual":[],"check":"no symbols","expected":[],"passed":true},{"actual":[1,1,1,1,1,1,1,1],"check":"padding can be set","expected":[1],"passed":false},{"actual":[1,1,1,1,1,1,1,1],"check":"whole byte","expected":[1,1,1,1,1,1,1,1],"passed":true},{"actual":[],"check":"all zero symbols","expected":[0,0,0],"passed":false},{"actual":[1,1,1,1,1,1,1,1,1],"check":"cross byte","expected":[1,1,1,1,1,1,1,1,1],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid zero suffix\", \"actual\": [1], \"expected\": [1, 0], \"passed\": false}, {\"check\": \"no symbols\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"padding can be set\", \"actual\": [1, 1, 1, 1, 1, 1, 1, 1], \"expected\": [1], \"passed\": false}, {\"check\": \"whole byte\", \"actual\": [1, 1, 1, 1, 1, 1, 1, 1], \"expected\": [1, 1, 1, 1, 1, 1, 1, 1], \"passed\": true}, {\"check\": \"all zero symbols\", \"actual\": [], \"expected\": [0, 0, 0], \"passed\": false}, {\"check\": \"cross byte\", \"actual\": [1, 1, 1, 1, 1, 1, 1, 1, 1], \"expected\": [1, 1, 1, 1, 1, 1, 1, 1, 1], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.277,"exit_code":1,"observations":[{"actual":[1,0,0,0,0,0,0,0],"check":"valid zero suffix","expected":[1,0],"passed":false},{"actual":[],"check":"no symbols","expected":[],"passed":true},{"actual":[1,1,1,1,1,1,1,1],"check":"padding can be set","expected":[1],"passed":false},{"actual":[1,1,1,1,1,1,1,1],"check":"whole byte","expected":[1,1,1,1,1,1,1,1],"passed":true},{"actual":[0,0,0,0,0,0,0,0],"check":"all zero symbols","expected":[0,0,0],"passed":false},{"actual":[1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0],"check":"cross byte","expected":[1,1,1,1,1,1,1,1,1],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid zero suffix\", \"actual\": [1, 0, 0, 0, 0, 0, 0, 0], \"expected\": [1, 0], \"passed\": false}, {\"check\": \"no symbols\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"padding can be set\", \"actual\": [1, 1, 1, 1, 1, 1, 1, 1], \"expected\": [1], \"passed\": false}, {\"check\": \"whole byte\", \"actual\": [1, 1, 1, 1, 1, 1, 1, 1], \"expected\": [1, 1, 1, 1, 1, 1, 1, 1], \"passed\": true}, {\"check\": \"all zero symbols\", \"actual\": [0, 0, 0, 0, 0, 0, 0, 0], \"expected\": [0, 0, 0], \"passed\": false}, {\"check\": \"cross byte\", \"actual\": [1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0], \"expected\": [1, 1, 1, 1, 1, 1, 1, 1, 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."}}