{"abstract":"The replication checkpoint operation is admitted even though a resume point splits a source transaction.","category":"Replication","checks":9,"contract":"Return a Boolean admission decision for persist a replication resume checkpoint. The record r must satisfy all of: all(x in r['contiguous_applied'][1] for x in range(r['contiguous_applied'][0]+1)); r['source_incarnation'][0] == r['source_incarnation'][1]; r['durable_destination'][0] <= r['durable_destination'][1]; r['transaction_boundary'][0] in r['transaction_boundary'][1]; r['checkpoint_monotonic'][0] >= r['checkpoint_monotonic'][1]. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-replication-checkpoint","failed_approach":"Adding the transaction boundary check repairs the reported defect, but replacing the adjacent checkpoint monotonic check loses that independent invariant.","family":"xd-replication-checkpoint-transaction_boundary","id":"FA-616","implementations":{"attempt":{"sha256":"0a0c975296cd05871dccbc2243be093479eb3a14cea4a20eda79e47fb7eb1d37","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (all(x in r['contiguous_applied'][1] for x in range(r['contiguous_applied'][0]+1))) and (r['source_incarnation'][0] == r['source_incarnation'][1]) and (r['durable_destination'][0] <= r['durable_destination'][1]) and (r['transaction_boundary'][0] in r['transaction_boundary'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'contiguous_applied': [3, [0, 1, 2, 3]], 'source_incarnation': ['g2', 'g2'], 'durable_destination': [7, 7], 'transaction_boundary': [8, [4, 8, 12]], 'checkpoint_monotonic': [9, 8]}\ncheck('valid operation', solve(r), True)\ncheck('The resume point crosses an unapplied sequence gap', solve(dict(r, **{'contiguous_applied': [3, [0, 1, 3]]})), False)\ncheck('A checkpoint is reused after the source log is recreated', solve(dict(r, **{'source_incarnation': ['g1', 'g2']})), False)\ncheck('The checkpoint exceeds durable destination progress', solve(dict(r, **{'durable_destination': [8, 7]})), False)\ncheck('A resume point splits a source transaction', solve(dict(r, **{'transaction_boundary': [7, [4, 8, 12]]})), False)\ncheck('A delayed checkpoint regresses persisted progress', solve(dict(r, **{'checkpoint_monotonic': [7, 8]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'contiguous_applied': [3, [0, 1, 3]], 'source_incarnation': ['g1', 'g2'], 'durable_destination': [8, 7], 'transaction_boundary': [7, [4, 8, 12]], 'checkpoint_monotonic': [7, 8]}\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":"95b9178c3341a2d0c629bfc14b08a4b8d0dfbe3b0bd99d5f873f6c93544f18a8","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (all(x in r['contiguous_applied'][1] for x in range(r['contiguous_applied'][0]+1))) and (r['source_incarnation'][0] == r['source_incarnation'][1]) and (r['durable_destination'][0] <= r['durable_destination'][1]) and (r['checkpoint_monotonic'][0] >= r['checkpoint_monotonic'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'contiguous_applied': [3, [0, 1, 2, 3]], 'source_incarnation': ['g2', 'g2'], 'durable_destination': [7, 7], 'transaction_boundary': [8, [4, 8, 12]], 'checkpoint_monotonic': [9, 8]}\ncheck('valid operation', solve(r), True)\ncheck('The resume point crosses an unapplied sequence gap', solve(dict(r, **{'contiguous_applied': [3, [0, 1, 3]]})), False)\ncheck('A checkpoint is reused after the source log is recreated', solve(dict(r, **{'source_incarnation': ['g1', 'g2']})), False)\ncheck('The checkpoint exceeds durable destination progress', solve(dict(r, **{'durable_destination': [8, 7]})), False)\ncheck('A resume point splits a source transaction', solve(dict(r, **{'transaction_boundary': [7, [4, 8, 12]]})), False)\ncheck('A delayed checkpoint regresses persisted progress', solve(dict(r, **{'checkpoint_monotonic': [7, 8]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'contiguous_applied': [3, [0, 1, 3]], 'source_incarnation': ['g1', 'g2'], 'durable_destination': [8, 7], 'transaction_boundary': [7, [4, 8, 12]], 'checkpoint_monotonic': [7, 8]}\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":"4587535ff7d136d91d32baecb3f787994644e06afeb88ee13ab465fdf281e443","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (all(x in r['contiguous_applied'][1] for x in range(r['contiguous_applied'][0]+1))) and (r['source_incarnation'][0] == r['source_incarnation'][1]) and (r['durable_destination'][0] <= r['durable_destination'][1]) and (r['transaction_boundary'][0] in r['transaction_boundary'][1]) and (r['checkpoint_monotonic'][0] >= r['checkpoint_monotonic'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'contiguous_applied': [3, [0, 1, 2, 3]], 'source_incarnation': ['g2', 'g2'], 'durable_destination': [7, 7], 'transaction_boundary': [8, [4, 8, 12]], 'checkpoint_monotonic': [9, 8]}\ncheck('valid operation', solve(r), True)\ncheck('The resume point crosses an unapplied sequence gap', solve(dict(r, **{'contiguous_applied': [3, [0, 1, 3]]})), False)\ncheck('A checkpoint is reused after the source log is recreated', solve(dict(r, **{'source_incarnation': ['g1', 'g2']})), False)\ncheck('The checkpoint exceeds durable destination progress', solve(dict(r, **{'durable_destination': [8, 7]})), False)\ncheck('A resume point splits a source transaction', solve(dict(r, **{'transaction_boundary': [7, [4, 8, 12]]})), False)\ncheck('A delayed checkpoint regresses persisted progress', solve(dict(r, **{'checkpoint_monotonic': [7, 8]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'contiguous_applied': [3, [0, 1, 3]], 'source_incarnation': ['g1', 'g2'], 'durable_destination': [8, 7], 'transaction_boundary': [7, [4, 8, 12]], 'checkpoint_monotonic': [7, 8]}\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-replication-checkpoint-transaction_boundary","generated_at":"2026-09-29T14:36:54.304281+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['transaction_boundary'][0] in r['transaction_boundary'][1] together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the transaction boundary invariant while validating the other operation preconditions.","sha256":"7ef2f521bc894c192357d677914f6a123388a17ad146455ae62aad1273c6fbd7","title":"Persist a replication resume checkpoint: A resume point splits a source transaction · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":33.113,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"The resume point crosses an unapplied sequence gap","expected":false,"passed":true},{"actual":false,"check":"A checkpoint is reused after the source log is recreated","expected":false,"passed":true},{"actual":false,"check":"The checkpoint exceeds durable destination progress","expected":false,"passed":true},{"actual":false,"check":"A resume point splits a source transaction","expected":false,"passed":true},{"actual":true,"check":"A delayed checkpoint regresses persisted progress","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 resume point crosses an unapplied sequence gap\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A checkpoint is reused after the source log is recreated\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The checkpoint exceeds durable destination progress\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A resume point splits a source transaction\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delayed checkpoint regresses persisted progress\", \"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":29.958,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"The resume point crosses an unapplied sequence gap","expected":false,"passed":true},{"actual":false,"check":"A checkpoint is reused after the source log is recreated","expected":false,"passed":true},{"actual":false,"check":"The checkpoint exceeds durable destination progress","expected":false,"passed":true},{"actual":true,"check":"A resume point splits a source transaction","expected":false,"passed":false},{"actual":false,"check":"A delayed checkpoint regresses persisted progress","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 resume point crosses an unapplied sequence gap\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A checkpoint is reused after the source log is recreated\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The checkpoint exceeds durable destination progress\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A resume point splits a source transaction\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"A delayed checkpoint regresses persisted progress\", \"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":29.145,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"The resume point crosses an unapplied sequence gap","expected":false,"passed":true},{"actual":false,"check":"A checkpoint is reused after the source log is recreated","expected":false,"passed":true},{"actual":false,"check":"The checkpoint exceeds durable destination progress","expected":false,"passed":true},{"actual":false,"check":"A resume point splits a source transaction","expected":false,"passed":true},{"actual":false,"check":"A delayed checkpoint regresses persisted progress","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 resume point crosses an unapplied sequence gap\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A checkpoint is reused after the source log is recreated\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The checkpoint exceeds durable destination progress\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A resume point splits a source transaction\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delayed checkpoint regresses persisted progress\", \"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"}