{"abstract":"The anti entropy repair operation is admitted even though compared digests describe different snapshot generations.","category":"Replication","checks":9,"contract":"Return a Boolean admission decision for apply an anti-entropy repair range. The record r must satisfy all of: all(r['range_ownership'][0] <= x < r['range_ownership'][1] for x in r['range_ownership'][2]); r['version_monotonic'][0] >= r['version_monotonic'][1]; r['tombstone_horizon'][0] >= r['tombstone_horizon'][1]; r['merkle_generation'][0] == r['merkle_generation'][1]; r['range_complete'][0] == r['range_complete'][1]. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-anti-entropy-repair","failed_approach":"Adding the merkle generation check repairs the reported defect, but replacing the adjacent range complete check loses that independent invariant.","family":"xd-anti-entropy-repair-merkle_generation","id":"FA-591","implementations":{"attempt":{"sha256":"140c822d03f7681299b96ab45ec809707b753eb850aae4896f62658d180651c9","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (all(r['range_ownership'][0] <= x < r['range_ownership'][1] for x in r['range_ownership'][2])) and (r['version_monotonic'][0] >= r['version_monotonic'][1]) and (r['tombstone_horizon'][0] >= r['tombstone_horizon'][1]) and (r['merkle_generation'][0] == r['merkle_generation'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'range_ownership': [10, 20, [10, 19]], 'version_monotonic': [7, 6], 'tombstone_horizon': [20, 20], 'merkle_generation': [8, 8], 'range_complete': [100, 100]}\ncheck('valid operation', solve(r), True)\ncheck('A repair writes keys outside the receiver owned range', solve(dict(r, **{'range_ownership': [10, 20, [9, 19]]})), False)\ncheck('Repair overwrites a record with an older revision', solve(dict(r, **{'version_monotonic': [5, 6]})), False)\ncheck('A deletion marker is dropped before repair safety horizon', solve(dict(r, **{'tombstone_horizon': [19, 20]})), False)\ncheck('Compared digests describe different snapshot generations', solve(dict(r, **{'merkle_generation': [7, 8]})), False)\ncheck('A partial range response is marked fully repaired', solve(dict(r, **{'range_complete': [80, 100]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'range_ownership': [10, 20, [9, 19]], 'version_monotonic': [5, 6], 'tombstone_horizon': [19, 20], 'merkle_generation': [7, 8], 'range_complete': [80, 100]}\nkeys = list(invalid)\npair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}\ncheck('two independent violations in variant', solve(dict(r, **pair)), False)\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":"851890b26dfae1434250329b7576418758f6ee469683962746317d3748513dcf","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (all(r['range_ownership'][0] <= x < r['range_ownership'][1] for x in r['range_ownership'][2])) and (r['version_monotonic'][0] >= r['version_monotonic'][1]) and (r['tombstone_horizon'][0] >= r['tombstone_horizon'][1]) and (r['range_complete'][0] == r['range_complete'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'range_ownership': [10, 20, [10, 19]], 'version_monotonic': [7, 6], 'tombstone_horizon': [20, 20], 'merkle_generation': [8, 8], 'range_complete': [100, 100]}\ncheck('valid operation', solve(r), True)\ncheck('A repair writes keys outside the receiver owned range', solve(dict(r, **{'range_ownership': [10, 20, [9, 19]]})), False)\ncheck('Repair overwrites a record with an older revision', solve(dict(r, **{'version_monotonic': [5, 6]})), False)\ncheck('A deletion marker is dropped before repair safety horizon', solve(dict(r, **{'tombstone_horizon': [19, 20]})), False)\ncheck('Compared digests describe different snapshot generations', solve(dict(r, **{'merkle_generation': [7, 8]})), False)\ncheck('A partial range response is marked fully repaired', solve(dict(r, **{'range_complete': [80, 100]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'range_ownership': [10, 20, [9, 19]], 'version_monotonic': [5, 6], 'tombstone_horizon': [19, 20], 'merkle_generation': [7, 8], 'range_complete': [80, 100]}\nkeys = list(invalid)\npair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}\ncheck('two independent violations in variant', solve(dict(r, **pair)), False)\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":"09ce6c3188d2db387b3f9a90778fba35d021dffcd6fd28d38e4e675e4c7b41be","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (all(r['range_ownership'][0] <= x < r['range_ownership'][1] for x in r['range_ownership'][2])) and (r['version_monotonic'][0] >= r['version_monotonic'][1]) and (r['tombstone_horizon'][0] >= r['tombstone_horizon'][1]) and (r['merkle_generation'][0] == r['merkle_generation'][1]) and (r['range_complete'][0] == r['range_complete'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'range_ownership': [10, 20, [10, 19]], 'version_monotonic': [7, 6], 'tombstone_horizon': [20, 20], 'merkle_generation': [8, 8], 'range_complete': [100, 100]}\ncheck('valid operation', solve(r), True)\ncheck('A repair writes keys outside the receiver owned range', solve(dict(r, **{'range_ownership': [10, 20, [9, 19]]})), False)\ncheck('Repair overwrites a record with an older revision', solve(dict(r, **{'version_monotonic': [5, 6]})), False)\ncheck('A deletion marker is dropped before repair safety horizon', solve(dict(r, **{'tombstone_horizon': [19, 20]})), False)\ncheck('Compared digests describe different snapshot generations', solve(dict(r, **{'merkle_generation': [7, 8]})), False)\ncheck('A partial range response is marked fully repaired', solve(dict(r, **{'range_complete': [80, 100]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'range_ownership': [10, 20, [9, 19]], 'version_monotonic': [5, 6], 'tombstone_horizon': [19, 20], 'merkle_generation': [7, 8], 'range_complete': [80, 100]}\nkeys = list(invalid)\npair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}\ncheck('two independent violations in variant', solve(dict(r, **pair)), False)\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":"xd-anti-entropy-repair-merkle_generation","generated_at":"2026-09-29T14:36:54.245655+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic local contract for replication. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.","repair":"Require r['merkle_generation'][0] == r['merkle_generation'][1] together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the merkle generation invariant while validating the other operation preconditions.","sha256":"58fabe21526a581e6647d703b2cfa807a277fdd91bab0cf2c7bd893bc6b406dc","title":"Apply an anti-entropy repair range: Compared digests describe different snapshot generations · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":32.207,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A repair writes keys outside the receiver owned range","expected":false,"passed":true},{"actual":false,"check":"Repair overwrites a record with an older revision","expected":false,"passed":true},{"actual":false,"check":"A deletion marker is dropped before repair safety horizon","expected":false,"passed":true},{"actual":false,"check":"Compared digests describe different snapshot generations","expected":false,"passed":true},{"actual":true,"check":"A partial range response is marked fully repaired","expected":false,"passed":false},{"actual":true,"check":"unrelated tracing metadata","expected":true,"passed":true},{"actual":true,"check":"repeat validation is pure","expected":true,"passed":true},{"actual":false,"check":"two independent violations in variant","expected":false,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid operation\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"A repair writes keys outside the receiver owned range\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Repair overwrites a record with an older revision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A deletion marker is dropped before repair safety horizon\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Compared digests describe different snapshot generations\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A partial range response is marked fully repaired\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"unrelated tracing metadata\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"repeat validation is pure\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"two independent violations in variant\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":30.114,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A repair writes keys outside the receiver owned range","expected":false,"passed":true},{"actual":false,"check":"Repair overwrites a record with an older revision","expected":false,"passed":true},{"actual":false,"check":"A deletion marker is dropped before repair safety horizon","expected":false,"passed":true},{"actual":true,"check":"Compared digests describe different snapshot generations","expected":false,"passed":false},{"actual":false,"check":"A partial range response is marked fully repaired","expected":false,"passed":true},{"actual":true,"check":"unrelated tracing metadata","expected":true,"passed":true},{"actual":true,"check":"repeat validation is pure","expected":true,"passed":true},{"actual":false,"check":"two independent violations in variant","expected":false,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid operation\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"A repair writes keys outside the receiver owned range\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Repair overwrites a record with an older revision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A deletion marker is dropped before repair safety horizon\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Compared digests describe different snapshot generations\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"A partial range response is marked fully repaired\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"unrelated tracing metadata\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"repeat validation is pure\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"two independent violations in variant\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":30.443,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A repair writes keys outside the receiver owned range","expected":false,"passed":true},{"actual":false,"check":"Repair overwrites a record with an older revision","expected":false,"passed":true},{"actual":false,"check":"A deletion marker is dropped before repair safety horizon","expected":false,"passed":true},{"actual":false,"check":"Compared digests describe different snapshot generations","expected":false,"passed":true},{"actual":false,"check":"A partial range response is marked fully repaired","expected":false,"passed":true},{"actual":true,"check":"unrelated tracing metadata","expected":true,"passed":true},{"actual":true,"check":"repeat validation is pure","expected":true,"passed":true},{"actual":false,"check":"two independent violations in variant","expected":false,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid operation\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"A repair writes keys outside the receiver owned range\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Repair overwrites a record with an older revision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A deletion marker is dropped before repair safety horizon\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Compared digests describe different snapshot generations\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A partial range response is marked fully repaired\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"unrelated tracing metadata\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"repeat validation is pure\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"two independent violations in variant\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}