{"abstract":"The leader transfer operation is admitted even though leadership is handed to a learner.","category":"Consensus","checks":9,"contract":"Return a Boolean admission decision for transfer leadership to a chosen voter. The record r must satisfy all of: r['target_voter'][0] in r['target_voter'][1]; r['log_caught_up'][0] >= r['log_caught_up'][1]; r['transfer_term'][0] == r['transfer_term'][1]; r['transfer_deadline'][0] < r['transfer_deadline'][1]; r['writes_drained'] == 0. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-leader-transfer","failed_approach":"Adding the target voter check repairs the reported defect, but replacing the adjacent log caught up check loses that independent invariant.","family":"xd-leader-transfer-target_voter","id":"FA-376","implementations":{"attempt":{"sha256":"02da96ec2caf05b751084053113a8c66752a3924b909375c5a73715755eb3aff","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['target_voter'][0] in r['target_voter'][1]) and (r['transfer_term'][0] == r['transfer_term'][1]) and (r['transfer_deadline'][0] < r['transfer_deadline'][1]) and (r['writes_drained'] == 0)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'target_voter': ['b', ['a', 'b']], 'log_caught_up': [12, 12], 'transfer_term': [4, 4], 'transfer_deadline': [9, 10], 'writes_drained': 0}\ncheck('valid operation', solve(r), True)\ncheck('Leadership is handed to a learner', solve(dict(r, **{'target_voter': ['c', ['a', 'b']]})), False)\ncheck('The target lacks the leader final log entry', solve(dict(r, **{'log_caught_up': [11, 12]})), False)\ncheck('A delayed handoff names an obsolete term', solve(dict(r, **{'transfer_term': [3, 4]})), False)\ncheck('The handoff arrives after its transfer deadline', solve(dict(r, **{'transfer_deadline': [10, 10]})), False)\ncheck('A transfer races outstanding leader writes', solve(dict(r, **{'writes_drained': 1})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'target_voter': ['c', ['a', 'b']], 'log_caught_up': [11, 12], 'transfer_term': [3, 4], 'transfer_deadline': [10, 10], 'writes_drained': 1}\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":"8fb5f85ff2afe2cb770bd63ddbd75576dff157cd6de9ccf74e06b61011ac0b77","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['log_caught_up'][0] >= r['log_caught_up'][1]) and (r['transfer_term'][0] == r['transfer_term'][1]) and (r['transfer_deadline'][0] < r['transfer_deadline'][1]) and (r['writes_drained'] == 0)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'target_voter': ['b', ['a', 'b']], 'log_caught_up': [12, 12], 'transfer_term': [4, 4], 'transfer_deadline': [9, 10], 'writes_drained': 0}\ncheck('valid operation', solve(r), True)\ncheck('Leadership is handed to a learner', solve(dict(r, **{'target_voter': ['c', ['a', 'b']]})), False)\ncheck('The target lacks the leader final log entry', solve(dict(r, **{'log_caught_up': [11, 12]})), False)\ncheck('A delayed handoff names an obsolete term', solve(dict(r, **{'transfer_term': [3, 4]})), False)\ncheck('The handoff arrives after its transfer deadline', solve(dict(r, **{'transfer_deadline': [10, 10]})), False)\ncheck('A transfer races outstanding leader writes', solve(dict(r, **{'writes_drained': 1})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'target_voter': ['c', ['a', 'b']], 'log_caught_up': [11, 12], 'transfer_term': [3, 4], 'transfer_deadline': [10, 10], 'writes_drained': 1}\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":"4ce9e53377245e383b22d77dc0c1cb278b244dc64ac833b4e8de485fbcbfaf8f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['target_voter'][0] in r['target_voter'][1]) and (r['log_caught_up'][0] >= r['log_caught_up'][1]) and (r['transfer_term'][0] == r['transfer_term'][1]) and (r['transfer_deadline'][0] < r['transfer_deadline'][1]) and (r['writes_drained'] == 0)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'target_voter': ['b', ['a', 'b']], 'log_caught_up': [12, 12], 'transfer_term': [4, 4], 'transfer_deadline': [9, 10], 'writes_drained': 0}\ncheck('valid operation', solve(r), True)\ncheck('Leadership is handed to a learner', solve(dict(r, **{'target_voter': ['c', ['a', 'b']]})), False)\ncheck('The target lacks the leader final log entry', solve(dict(r, **{'log_caught_up': [11, 12]})), False)\ncheck('A delayed handoff names an obsolete term', solve(dict(r, **{'transfer_term': [3, 4]})), False)\ncheck('The handoff arrives after its transfer deadline', solve(dict(r, **{'transfer_deadline': [10, 10]})), False)\ncheck('A transfer races outstanding leader writes', solve(dict(r, **{'writes_drained': 1})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'target_voter': ['c', ['a', 'b']], 'log_caught_up': [11, 12], 'transfer_term': [3, 4], 'transfer_deadline': [10, 10], 'writes_drained': 1}\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-leader-transfer-target_voter","generated_at":"2026-09-29T14:36:52.596651+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['target_voter'][0] in r['target_voter'][1] together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the target voter invariant while validating the other operation preconditions.","sha256":"7369ec772835bb7d5155e261303c48125efac081945e367ae87e5b96211081fb","title":"Transfer leadership to a chosen voter: Leadership is handed to a learner · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":31.793,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Leadership is handed to a learner","expected":false,"passed":true},{"actual":true,"check":"The target lacks the leader final log entry","expected":false,"passed":false},{"actual":false,"check":"A delayed handoff names an obsolete term","expected":false,"passed":true},{"actual":false,"check":"The handoff arrives after its transfer deadline","expected":false,"passed":true},{"actual":false,"check":"A transfer races outstanding leader writes","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\": \"Leadership is handed to a learner\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The target lacks the leader final log entry\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"A delayed handoff names an obsolete term\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The handoff arrives after its transfer deadline\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A transfer races outstanding leader writes\", \"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"},"broken":{"elapsed_ms":34.918,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":true,"check":"Leadership is handed to a learner","expected":false,"passed":false},{"actual":false,"check":"The target lacks the leader final log entry","expected":false,"passed":true},{"actual":false,"check":"A delayed handoff names an obsolete term","expected":false,"passed":true},{"actual":false,"check":"The handoff arrives after its transfer deadline","expected":false,"passed":true},{"actual":false,"check":"A transfer races outstanding leader writes","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\": \"Leadership is handed to a learner\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"The target lacks the leader final log entry\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delayed handoff names an obsolete term\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The handoff arrives after its transfer deadline\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A transfer races outstanding leader writes\", \"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":32.356,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Leadership is handed to a learner","expected":false,"passed":true},{"actual":false,"check":"The target lacks the leader final log entry","expected":false,"passed":true},{"actual":false,"check":"A delayed handoff names an obsolete term","expected":false,"passed":true},{"actual":false,"check":"The handoff arrives after its transfer deadline","expected":false,"passed":true},{"actual":false,"check":"A transfer races outstanding leader writes","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\": \"Leadership is handed to a learner\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The target lacks the leader final log entry\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delayed handoff names an obsolete term\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The handoff arrives after its transfer deadline\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A transfer races outstanding leader writes\", \"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"}