{"abstract":"The distributed transaction operation is admitted even though a newly enlisted participant is omitted from the decision.","category":"Concurrency","checks":9,"contract":"Return a Boolean admission decision for commit a two-phase transaction. The record r must satisfy all of: all(x == 'prepared' for x in r['all_prepared']); 'abort' not in r['no_abort_vote']; r['decision_durable'] is True; set(r['participant_set'][0]) == set(r['participant_set'][1]); r['coordinator_epoch'][0] == r['coordinator_epoch'][1]. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-distributed-transaction","failed_approach":"Adding the participant set check repairs the reported defect, but replacing the adjacent coordinator epoch check loses that independent invariant.","family":"xd-distributed-transaction-participant_set","id":"FA-1466","implementations":{"attempt":{"sha256":"fffb8d2a0c65072b7c33b37bd54c503b9c5599896ca8296c1f8a7dfd56943f94","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (all(x == 'prepared' for x in r['all_prepared'])) and ('abort' not in r['no_abort_vote']) and (r['decision_durable'] is True) and (set(r['participant_set'][0]) == set(r['participant_set'][1]))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'all_prepared': ['prepared', 'prepared'], 'no_abort_vote': ['yes', 'yes'], 'decision_durable': True, 'participant_set': [['a', 'b'], ['a', 'b']], 'coordinator_epoch': [5, 5]}\ncheck('valid operation', solve(r), True)\ncheck('Commit proceeds while a participant has not prepared', solve(dict(r, **{'all_prepared': ['prepared', 'working']})), False)\ncheck('A participant abort vote is ignored', solve(dict(r, **{'no_abort_vote': ['yes', 'abort']})), False)\ncheck('Commit messages precede the durable coordinator decision', solve(dict(r, **{'decision_durable': False})), False)\ncheck('A newly enlisted participant is omitted from the decision', solve(dict(r, **{'participant_set': [['a', 'b'], ['a']]})), False)\ncheck('A recovered coordinator accepts the prior instance decision', solve(dict(r, **{'coordinator_epoch': [4, 5]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'all_prepared': ['prepared', 'working'], 'no_abort_vote': ['yes', 'abort'], 'decision_durable': False, 'participant_set': [['a', 'b'], ['a']], 'coordinator_epoch': [4, 5]}\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":"0f55dc2beff71a9b74690eeb4053848bfe4d64ace9f616b55968fcbfa43c5865","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (all(x == 'prepared' for x in r['all_prepared'])) and ('abort' not in r['no_abort_vote']) and (r['decision_durable'] is True) and (r['coordinator_epoch'][0] == r['coordinator_epoch'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'all_prepared': ['prepared', 'prepared'], 'no_abort_vote': ['yes', 'yes'], 'decision_durable': True, 'participant_set': [['a', 'b'], ['a', 'b']], 'coordinator_epoch': [5, 5]}\ncheck('valid operation', solve(r), True)\ncheck('Commit proceeds while a participant has not prepared', solve(dict(r, **{'all_prepared': ['prepared', 'working']})), False)\ncheck('A participant abort vote is ignored', solve(dict(r, **{'no_abort_vote': ['yes', 'abort']})), False)\ncheck('Commit messages precede the durable coordinator decision', solve(dict(r, **{'decision_durable': False})), False)\ncheck('A newly enlisted participant is omitted from the decision', solve(dict(r, **{'participant_set': [['a', 'b'], ['a']]})), False)\ncheck('A recovered coordinator accepts the prior instance decision', solve(dict(r, **{'coordinator_epoch': [4, 5]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'all_prepared': ['prepared', 'working'], 'no_abort_vote': ['yes', 'abort'], 'decision_durable': False, 'participant_set': [['a', 'b'], ['a']], 'coordinator_epoch': [4, 5]}\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":"94e1a49da4a6a7d3f634fc190726bb5ed57954c5c46cf0ab258b7cacc624f2ab","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (all(x == 'prepared' for x in r['all_prepared'])) and ('abort' not in r['no_abort_vote']) and (r['decision_durable'] is True) and (set(r['participant_set'][0]) == set(r['participant_set'][1])) and (r['coordinator_epoch'][0] == r['coordinator_epoch'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'all_prepared': ['prepared', 'prepared'], 'no_abort_vote': ['yes', 'yes'], 'decision_durable': True, 'participant_set': [['a', 'b'], ['a', 'b']], 'coordinator_epoch': [5, 5]}\ncheck('valid operation', solve(r), True)\ncheck('Commit proceeds while a participant has not prepared', solve(dict(r, **{'all_prepared': ['prepared', 'working']})), False)\ncheck('A participant abort vote is ignored', solve(dict(r, **{'no_abort_vote': ['yes', 'abort']})), False)\ncheck('Commit messages precede the durable coordinator decision', solve(dict(r, **{'decision_durable': False})), False)\ncheck('A newly enlisted participant is omitted from the decision', solve(dict(r, **{'participant_set': [['a', 'b'], ['a']]})), False)\ncheck('A recovered coordinator accepts the prior instance decision', solve(dict(r, **{'coordinator_epoch': [4, 5]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'all_prepared': ['prepared', 'working'], 'no_abort_vote': ['yes', 'abort'], 'decision_durable': False, 'participant_set': [['a', 'b'], ['a']], 'coordinator_epoch': [4, 5]}\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-distributed-transaction-participant_set","generated_at":"2026-09-29T14:37:02.428216+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic local contract for concurrency. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.","repair":"Require set(r['participant_set'][0]) == set(r['participant_set'][1]) together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the participant set invariant while validating the other operation preconditions.","sha256":"8312c3625d923352d2049a8da06de52e906df25f0cb6934f63940b4ec300bb7d","title":"Commit a two-phase transaction: A newly enlisted participant is omitted from the decision · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":106.352,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Commit proceeds while a participant has not prepared","expected":false,"passed":true},{"actual":false,"check":"A participant abort vote is ignored","expected":false,"passed":true},{"actual":false,"check":"Commit messages precede the durable coordinator decision","expected":false,"passed":true},{"actual":false,"check":"A newly enlisted participant is omitted from the decision","expected":false,"passed":true},{"actual":true,"check":"A recovered coordinator accepts the prior instance decision","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\": \"Commit proceeds while a participant has not prepared\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A participant abort vote is ignored\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Commit messages precede the durable coordinator decision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A newly enlisted participant is omitted from the decision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A recovered coordinator accepts the prior instance decision\", \"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":30.478,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Commit proceeds while a participant has not prepared","expected":false,"passed":true},{"actual":false,"check":"A participant abort vote is ignored","expected":false,"passed":true},{"actual":false,"check":"Commit messages precede the durable coordinator decision","expected":false,"passed":true},{"actual":true,"check":"A newly enlisted participant is omitted from the decision","expected":false,"passed":false},{"actual":false,"check":"A recovered coordinator accepts the prior instance decision","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\": \"Commit proceeds while a participant has not prepared\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A participant abort vote is ignored\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Commit messages precede the durable coordinator decision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A newly enlisted participant is omitted from the decision\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"A recovered coordinator accepts the prior instance decision\", \"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":36.712,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Commit proceeds while a participant has not prepared","expected":false,"passed":true},{"actual":false,"check":"A participant abort vote is ignored","expected":false,"passed":true},{"actual":false,"check":"Commit messages precede the durable coordinator decision","expected":false,"passed":true},{"actual":false,"check":"A newly enlisted participant is omitted from the decision","expected":false,"passed":true},{"actual":false,"check":"A recovered coordinator accepts the prior instance decision","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\": \"Commit proceeds while a participant has not prepared\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A participant abort vote is ignored\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Commit messages precede the durable coordinator decision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A newly enlisted participant is omitted from the decision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A recovered coordinator accepts the prior instance decision\", \"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"}