{"abstract":"A header with division 0 is returned as ppq 0, which later divides by zero in timing code.","category":"MIDI event timing","checks":8,"contract":"Input the bytes of a header chunk: \"MThd\", a 32-bit big-endian length (>= 6; extra bytes ignored but must be present), 16-bit format (0, 1, 2), 16-bit track count (nonzero; exactly 1 for format 0) and 16-bit division. If bit 15 of division is set, the high byte is a negative two's-complement frame rate (24, 25, 29, 30) and the low byte ticks per frame; otherwise division is ticks per quarter note (nonzero). Return a dict or None.","contract_signature":"x","evaluation_group":"w2-midi-event-timing-smf-header","failed_approach":"Division is assembled from unsigned bytes, so a negative check never fires.","family":"w2-midi-event-timing-smf-header-zero-division","id":"FA-81401","implementations":{"attempt":{"sha256":"576444a3b55dc0a87211ad8eebb063372af7b407072e6c3f81af9624af5b720e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    if not isinstance(x, list) or len(x) < 14 or x[:4] != [77, 84, 104, 100]:\n        return None\n    length = (x[4] << 24) | (x[5] << 16) | (x[6] << 8) | x[7]\n    if length < 6 or len(x) < 8 + length:\n        return None\n    fmt = (x[8] << 8) | x[9]\n    ntrks = (x[10] << 8) | x[11]\n    division = (x[12] << 8) | x[13]\n    if fmt not in (0, 1, 2) or ntrks == 0 or (fmt == 0 and ntrks != 1):\n        return None\n    if division & 0x8000:\n        fps = 256 - x[12]\n        if fps not in (24, 25, 29, 30):\n            return None\n        return {'format': fmt, 'tracks': ntrks, 'fps': fps, 'ticks_per_frame': x[13]}\n    if division < 0:\n        return None\n    return {'format': fmt, 'tracks': ntrks, 'ppq': division}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 1, 224], {'format': 1, 'tracks': 2, 'ppq': 480}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 0, 0, 1, 0, 96], {'format': 0, 'tracks': 1, 'ppq': 96}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 0, 0, 2, 0, 96], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 3, 231, 40], {'format': 1, 'tracks': 3, 'fps': 25, 'ticks_per_frame': 40}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 232, 80], {'format': 1, 'tracks': 1, 'fps': 24, 'ticks_per_frame': 80}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 227, 4], {'format': 1, 'tracks': 1, 'fps': 29, 'ticks_per_frame': 4}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 226, 100], {'format': 1, 'tracks': 1, 'fps': 30, 'ticks_per_frame': 100}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None)], [([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 3, 231, 40], {'format': 1, 'tracks': 3, 'fps': 25, 'ticks_per_frame': 40}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 232, 80], {'format': 1, 'tracks': 1, 'fps': 24, 'ticks_per_frame': 80}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 227, 4], {'format': 1, 'tracks': 1, 'fps': 29, 'ticks_per_frame': 4}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 226, 100], {'format': 1, 'tracks': 1, 'fps': 30, 'ticks_per_frame': 100}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 230, 4], None), ([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224, 0, 0], {'format': 1, 'tracks': 2, 'ppq': 480}), ([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None)], [([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 226, 100], {'format': 1, 'tracks': 1, 'fps': 30, 'ticks_per_frame': 100}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 230, 4], None), ([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224, 0, 0], {'format': 1, 'tracks': 2, 'ppq': 480}), ([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 5, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 1, 0, 6, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 3, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None)], [([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 5, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 1, 0, 6, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 3, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 0, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 2, 0, 5, 0, 120], {'format': 2, 'tracks': 5, 'ppq': 120}), ([77, 84, 105, 100, 0, 0, 0, 6, 0, 1, 0, 2, 1, 224], None)], [([77, 84, 104, 100, 0, 0, 0, 6, 0, 3, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 0, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 2, 0, 5, 0, 120], {'format': 2, 'tracks': 5, 'ppq': 120}), ([77, 84, 105, 100, 0, 0, 0, 6, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1], None), ([77, 84, 104, 100, 0, 0, 0, 7, 0, 1, 0, 2, 1, 224, 9], {'format': 1, 'tracks': 2, 'ppq': 480}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 128, 0], None)]]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"oracle %d\" % i, solve(args), expected)\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":"0517738868eaf989f2749b76b200306f2baa62b0d831f5654cfcb025cd8b5255","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    if not isinstance(x, list) or len(x) < 14 or x[:4] != [77, 84, 104, 100]:\n        return None\n    length = (x[4] << 24) | (x[5] << 16) | (x[6] << 8) | x[7]\n    if length < 6 or len(x) < 8 + length:\n        return None\n    fmt = (x[8] << 8) | x[9]\n    ntrks = (x[10] << 8) | x[11]\n    division = (x[12] << 8) | x[13]\n    if fmt not in (0, 1, 2) or ntrks == 0 or (fmt == 0 and ntrks != 1):\n        return None\n    if division & 0x8000:\n        fps = 256 - x[12]\n        if fps not in (24, 25, 29, 30):\n            return None\n        return {'format': fmt, 'tracks': ntrks, 'fps': fps, 'ticks_per_frame': x[13]}\n    return {'format': fmt, 'tracks': ntrks, 'ppq': division}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 1, 224], {'format': 1, 'tracks': 2, 'ppq': 480}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 0, 0, 1, 0, 96], {'format': 0, 'tracks': 1, 'ppq': 96}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 0, 0, 2, 0, 96], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 3, 231, 40], {'format': 1, 'tracks': 3, 'fps': 25, 'ticks_per_frame': 40}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 232, 80], {'format': 1, 'tracks': 1, 'fps': 24, 'ticks_per_frame': 80}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 227, 4], {'format': 1, 'tracks': 1, 'fps': 29, 'ticks_per_frame': 4}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 226, 100], {'format': 1, 'tracks': 1, 'fps': 30, 'ticks_per_frame': 100}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None)], [([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 3, 231, 40], {'format': 1, 'tracks': 3, 'fps': 25, 'ticks_per_frame': 40}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 232, 80], {'format': 1, 'tracks': 1, 'fps': 24, 'ticks_per_frame': 80}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 227, 4], {'format': 1, 'tracks': 1, 'fps': 29, 'ticks_per_frame': 4}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 226, 100], {'format': 1, 'tracks': 1, 'fps': 30, 'ticks_per_frame': 100}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 230, 4], None), ([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224, 0, 0], {'format': 1, 'tracks': 2, 'ppq': 480}), ([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None)], [([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 226, 100], {'format': 1, 'tracks': 1, 'fps': 30, 'ticks_per_frame': 100}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 1, 230, 4], None), ([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224, 0, 0], {'format': 1, 'tracks': 2, 'ppq': 480}), ([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 5, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 1, 0, 6, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 3, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None)], [([77, 84, 104, 100, 0, 0, 0, 8, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 5, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 1, 0, 6, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 3, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 0, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 2, 0, 5, 0, 120], {'format': 2, 'tracks': 5, 'ppq': 120}), ([77, 84, 105, 100, 0, 0, 0, 6, 0, 1, 0, 2, 1, 224], None)], [([77, 84, 104, 100, 0, 0, 0, 6, 0, 3, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 0, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 0, 0], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 2, 0, 5, 0, 120], {'format': 2, 'tracks': 5, 'ppq': 120}), ([77, 84, 105, 100, 0, 0, 0, 6, 0, 1, 0, 2, 1, 224], None), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1], None), ([77, 84, 104, 100, 0, 0, 0, 7, 0, 1, 0, 2, 1, 224, 9], {'format': 1, 'tracks': 2, 'ppq': 480}), ([77, 84, 104, 100, 0, 0, 0, 6, 0, 1, 0, 2, 128, 0], None)]]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"oracle %d\" % i, solve(args), expected)\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":"A deterministic bounded teaching model with a stipulated toy contract; it is not a complete Standard MIDI File or MIDI 1.0/2.0 implementation. 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":"w2-midi-event-timing-smf-header-zero-division","generated_at":"2026-09-29T14:50:02.542522+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"MIDI sequencers, file readers and synth drivers depend on exact event ordering and tick/time arithmetic.","root_cause":"The metrical-division branch does not reject a zero tick resolution.","sha256":"b2015aa25d73a2cb9f40877c30b493028e04ee3c96c7e541976e9db24e312c71","title":"Standard MIDI File header chunk reader: zero ticks per quarter accepted · 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":39.199,"exit_code":1,"observations":[{"actual":{"format":1,"ppq":480,"tracks":2},"check":"oracle 0","expected":{"format":1,"ppq":480,"tracks":2},"passed":true},{"actual":{"format":0,"ppq":96,"tracks":1},"check":"oracle 1","expected":{"format":0,"ppq":96,"tracks":1},"passed":true},{"actual":null,"check":"oracle 2","expected":null,"passed":true},{"actual":{"format":1,"fps":25,"ticks_per_frame":40,"tracks":3},"check":"oracle 3","expected":{"format":1,"fps":25,"ticks_per_frame":40,"tracks":3},"passed":true},{"actual":{"format":1,"fps":24,"ticks_per_frame":80,"tracks":1},"check":"oracle 4","expected":{"format":1,"fps":24,"ticks_per_frame":80,"tracks":1},"passed":true},{"actual":{"format":1,"fps":29,"ticks_per_frame":4,"tracks":1},"check":"oracle 5","expected":{"format":1,"fps":29,"ticks_per_frame":4,"tracks":1},"passed":true},{"actual":{"format":1,"fps":30,"ticks_per_frame":100,"tracks":1},"check":"oracle 6","expected":{"format":1,"fps":30,"ticks_per_frame":100,"tracks":1},"passed":true},{"actual":{"format":1,"ppq":0,"tracks":2},"check":"oracle 7","expected":null,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 0\", \"actual\": {\"format\": 1, \"tracks\": 2, \"ppq\": 480}, \"expected\": {\"format\": 1, \"tracks\": 2, \"ppq\": 480}, \"passed\": true}, {\"check\": \"oracle 1\", \"actual\": {\"format\": 0, \"tracks\": 1, \"ppq\": 96}, \"expected\": {\"format\": 0, \"tracks\": 1, \"ppq\": 96}, \"passed\": true}, {\"check\": \"oracle 2\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 3\", \"actual\": {\"format\": 1, \"tracks\": 3, \"fps\": 25, \"ticks_per_frame\": 40}, \"expected\": {\"format\": 1, \"tracks\": 3, \"fps\": 25, \"ticks_per_frame\": 40}, \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": {\"format\": 1, \"tracks\": 1, \"fps\": 24, \"ticks_per_frame\": 80}, \"expected\": {\"format\": 1, \"tracks\": 1, \"fps\": 24, \"ticks_per_frame\": 80}, \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": {\"format\": 1, \"tracks\": 1, \"fps\": 29, \"ticks_per_frame\": 4}, \"expected\": {\"format\": 1, \"tracks\": 1, \"fps\": 29, \"ticks_per_frame\": 4}, \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": {\"format\": 1, \"tracks\": 1, \"fps\": 30, \"ticks_per_frame\": 100}, \"expected\": {\"format\": 1, \"tracks\": 1, \"fps\": 30, \"ticks_per_frame\": 100}, \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": {\"format\": 1, \"tracks\": 2, \"ppq\": 0}, \"expected\": null, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.95,"exit_code":1,"observations":[{"actual":{"format":1,"ppq":480,"tracks":2},"check":"oracle 0","expected":{"format":1,"ppq":480,"tracks":2},"passed":true},{"actual":{"format":0,"ppq":96,"tracks":1},"check":"oracle 1","expected":{"format":0,"ppq":96,"tracks":1},"passed":true},{"actual":null,"check":"oracle 2","expected":null,"passed":true},{"actual":{"format":1,"fps":25,"ticks_per_frame":40,"tracks":3},"check":"oracle 3","expected":{"format":1,"fps":25,"ticks_per_frame":40,"tracks":3},"passed":true},{"actual":{"format":1,"fps":24,"ticks_per_frame":80,"tracks":1},"check":"oracle 4","expected":{"format":1,"fps":24,"ticks_per_frame":80,"tracks":1},"passed":true},{"actual":{"format":1,"fps":29,"ticks_per_frame":4,"tracks":1},"check":"oracle 5","expected":{"format":1,"fps":29,"ticks_per_frame":4,"tracks":1},"passed":true},{"actual":{"format":1,"fps":30,"ticks_per_frame":100,"tracks":1},"check":"oracle 6","expected":{"format":1,"fps":30,"ticks_per_frame":100,"tracks":1},"passed":true},{"actual":{"format":1,"ppq":0,"tracks":2},"check":"oracle 7","expected":null,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 0\", \"actual\": {\"format\": 1, \"tracks\": 2, \"ppq\": 480}, \"expected\": {\"format\": 1, \"tracks\": 2, \"ppq\": 480}, \"passed\": true}, {\"check\": \"oracle 1\", \"actual\": {\"format\": 0, \"tracks\": 1, \"ppq\": 96}, \"expected\": {\"format\": 0, \"tracks\": 1, \"ppq\": 96}, \"passed\": true}, {\"check\": \"oracle 2\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 3\", \"actual\": {\"format\": 1, \"tracks\": 3, \"fps\": 25, \"ticks_per_frame\": 40}, \"expected\": {\"format\": 1, \"tracks\": 3, \"fps\": 25, \"ticks_per_frame\": 40}, \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": {\"format\": 1, \"tracks\": 1, \"fps\": 24, \"ticks_per_frame\": 80}, \"expected\": {\"format\": 1, \"tracks\": 1, \"fps\": 24, \"ticks_per_frame\": 80}, \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": {\"format\": 1, \"tracks\": 1, \"fps\": 29, \"ticks_per_frame\": 4}, \"expected\": {\"format\": 1, \"tracks\": 1, \"fps\": 29, \"ticks_per_frame\": 4}, \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": {\"format\": 1, \"tracks\": 1, \"fps\": 30, \"ticks_per_frame\": 100}, \"expected\": {\"format\": 1, \"tracks\": 1, \"fps\": 30, \"ticks_per_frame\": 100}, \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": {\"format\": 1, \"tracks\": 2, \"ppq\": 0}, \"expected\": null, \"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."}}