{"abstract":"The joint configuration operation is admitted even though a second membership change overlaps an unfinalized change.","category":"Consensus","checks":9,"contract":"Return a Boolean admission decision for activate a joint voting configuration. The record r must satisfy all of: len(set(r['old_majority'][0]) & set(r['old_majority'][1])) * 2 > len(set(r['old_majority'][0])); len(set(r['new_majority'][0]) & set(r['new_majority'][1])) * 2 > len(set(r['new_majority'][0])); r['configuration_entry'][0] <= r['configuration_entry'][1]; r['no_pending_change'] is None; all(x >= r['learner_catchup'][0] for x in r['learner_catchup'][1]). Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-joint-configuration","failed_approach":"Adding the no pending change check repairs the reported defect, but replacing the adjacent learner catchup check loses that independent invariant.","family":"xd-joint-configuration-no_pending_change","id":"FA-366","implementations":{"attempt":{"sha256":"e8b59930d9767479e16d937283c0ee32a5e8a86d732d9f0346a44dce77842eb5","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (len(set(r['old_majority'][0]) & set(r['old_majority'][1])) * 2 > len(set(r['old_majority'][0]))) and (len(set(r['new_majority'][0]) & set(r['new_majority'][1])) * 2 > len(set(r['new_majority'][0]))) and (r['configuration_entry'][0] <= r['configuration_entry'][1]) and (r['no_pending_change'] is None)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'old_majority': [[1, 2, 3], [1, 2]], 'new_majority': [[3, 4, 5], [3, 4]], 'configuration_entry': [8, 8], 'no_pending_change': None, 'learner_catchup': [8, [8, 10]]}\ncheck('valid operation', solve(r), True)\ncheck('The old configuration has only a minority', solve(dict(r, **{'old_majority': [[1, 2, 3], [1]]})), False)\ncheck('The new configuration has only a minority', solve(dict(r, **{'new_majority': [[3, 4, 5], [3]]})), False)\ncheck('The configuration entry is beyond the committed prefix', solve(dict(r, **{'configuration_entry': [9, 8]})), False)\ncheck('A second membership change overlaps an unfinalized change', solve(dict(r, **{'no_pending_change': 'pending'})), False)\ncheck('A promoted learner lacks the configuration entry', solve(dict(r, **{'learner_catchup': [8, [7, 10]]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'old_majority': [[1, 2, 3], [1]], 'new_majority': [[3, 4, 5], [3]], 'configuration_entry': [9, 8], 'no_pending_change': 'pending', 'learner_catchup': [8, [7, 10]]}\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":"91bd59f43b044d8a649156208ff3f2d62685e1a63d8346b24a26de2baa2fa526","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (len(set(r['old_majority'][0]) & set(r['old_majority'][1])) * 2 > len(set(r['old_majority'][0]))) and (len(set(r['new_majority'][0]) & set(r['new_majority'][1])) * 2 > len(set(r['new_majority'][0]))) and (r['configuration_entry'][0] <= r['configuration_entry'][1]) and (all(x >= r['learner_catchup'][0] for x in r['learner_catchup'][1]))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'old_majority': [[1, 2, 3], [1, 2]], 'new_majority': [[3, 4, 5], [3, 4]], 'configuration_entry': [8, 8], 'no_pending_change': None, 'learner_catchup': [8, [8, 10]]}\ncheck('valid operation', solve(r), True)\ncheck('The old configuration has only a minority', solve(dict(r, **{'old_majority': [[1, 2, 3], [1]]})), False)\ncheck('The new configuration has only a minority', solve(dict(r, **{'new_majority': [[3, 4, 5], [3]]})), False)\ncheck('The configuration entry is beyond the committed prefix', solve(dict(r, **{'configuration_entry': [9, 8]})), False)\ncheck('A second membership change overlaps an unfinalized change', solve(dict(r, **{'no_pending_change': 'pending'})), False)\ncheck('A promoted learner lacks the configuration entry', solve(dict(r, **{'learner_catchup': [8, [7, 10]]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'old_majority': [[1, 2, 3], [1]], 'new_majority': [[3, 4, 5], [3]], 'configuration_entry': [9, 8], 'no_pending_change': 'pending', 'learner_catchup': [8, [7, 10]]}\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":"6e45b06d90952e6404847bc78b042d94f5bbf74d431eb4a6ec72d257ffdd3823","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (len(set(r['old_majority'][0]) & set(r['old_majority'][1])) * 2 > len(set(r['old_majority'][0]))) and (len(set(r['new_majority'][0]) & set(r['new_majority'][1])) * 2 > len(set(r['new_majority'][0]))) and (r['configuration_entry'][0] <= r['configuration_entry'][1]) and (r['no_pending_change'] is None) and (all(x >= r['learner_catchup'][0] for x in r['learner_catchup'][1]))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'old_majority': [[1, 2, 3], [1, 2]], 'new_majority': [[3, 4, 5], [3, 4]], 'configuration_entry': [8, 8], 'no_pending_change': None, 'learner_catchup': [8, [8, 10]]}\ncheck('valid operation', solve(r), True)\ncheck('The old configuration has only a minority', solve(dict(r, **{'old_majority': [[1, 2, 3], [1]]})), False)\ncheck('The new configuration has only a minority', solve(dict(r, **{'new_majority': [[3, 4, 5], [3]]})), False)\ncheck('The configuration entry is beyond the committed prefix', solve(dict(r, **{'configuration_entry': [9, 8]})), False)\ncheck('A second membership change overlaps an unfinalized change', solve(dict(r, **{'no_pending_change': 'pending'})), False)\ncheck('A promoted learner lacks the configuration entry', solve(dict(r, **{'learner_catchup': [8, [7, 10]]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'old_majority': [[1, 2, 3], [1]], 'new_majority': [[3, 4, 5], [3]], 'configuration_entry': [9, 8], 'no_pending_change': 'pending', 'learner_catchup': [8, [7, 10]]}\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-joint-configuration-no_pending_change","generated_at":"2026-09-29T14:36:52.596006+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic local contract for consensus. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.","repair":"Require r['no_pending_change'] is None together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the no pending change invariant while validating the other operation preconditions.","sha256":"586edfbcde4dea76707dbc2e76478a7fd2e78dc7888e06e30878db8cd9cac39d","title":"Activate a joint voting configuration: A second membership change overlaps an unfinalized change · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":33.967,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"The old configuration has only a minority","expected":false,"passed":true},{"actual":false,"check":"The new configuration has only a minority","expected":false,"passed":true},{"actual":false,"check":"The configuration entry is beyond the committed prefix","expected":false,"passed":true},{"actual":false,"check":"A second membership change overlaps an unfinalized change","expected":false,"passed":true},{"actual":true,"check":"A promoted learner lacks the configuration entry","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\": \"The old configuration has only a minority\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The new configuration has only a minority\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The configuration entry is beyond the committed prefix\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A second membership change overlaps an unfinalized change\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A promoted learner lacks the configuration entry\", \"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":34.187,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"The old configuration has only a minority","expected":false,"passed":true},{"actual":false,"check":"The new configuration has only a minority","expected":false,"passed":true},{"actual":false,"check":"The configuration entry is beyond the committed prefix","expected":false,"passed":true},{"actual":true,"check":"A second membership change overlaps an unfinalized change","expected":false,"passed":false},{"actual":false,"check":"A promoted learner lacks the configuration entry","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\": \"The old configuration has only a minority\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The new configuration has only a minority\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The configuration entry is beyond the committed prefix\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A second membership change overlaps an unfinalized change\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"A promoted learner lacks the configuration entry\", \"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":32.169,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"The old configuration has only a minority","expected":false,"passed":true},{"actual":false,"check":"The new configuration has only a minority","expected":false,"passed":true},{"actual":false,"check":"The configuration entry is beyond the committed prefix","expected":false,"passed":true},{"actual":false,"check":"A second membership change overlaps an unfinalized change","expected":false,"passed":true},{"actual":false,"check":"A promoted learner lacks the configuration entry","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\": \"The old configuration has only a minority\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The new configuration has only a minority\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The configuration entry is beyond the committed prefix\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A second membership change overlaps an unfinalized change\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A promoted learner lacks the configuration entry\", \"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"}