{"abstract":"The snapshot install operation is admitted even though a snapshot rolls back applied state.","category":"Replication","checks":9,"contract":"Return a Boolean admission decision for install a replicated state snapshot. The record r must satisfy all of: r['newer_applied'][0] >= r['newer_applied'][1]; set(r['complete_chunks'][0]) == set(range(r['complete_chunks'][1])); r['checksum_match'][0] == r['checksum_match'][1]; bool(r['configuration_present']); r['index_term_pair'][0] == r['index_term_pair'][1]. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-snapshot-install","failed_approach":"Adding the newer applied check repairs the reported defect, but replacing the adjacent complete chunks check loses that independent invariant.","family":"xd-snapshot-install-newer_applied","id":"FA-401","implementations":{"attempt":{"sha256":"ce6fbac50cce90b6a7ec7878d0f286abfa115b16ac2db946cdc86a53f3e118bc","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['newer_applied'][0] >= r['newer_applied'][1]) and (r['checksum_match'][0] == r['checksum_match'][1]) and (bool(r['configuration_present'])) and (r['index_term_pair'][0] == r['index_term_pair'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'newer_applied': [12, 10], 'complete_chunks': [[0, 1, 2], 3], 'checksum_match': ['abc', 'abc'], 'configuration_present': [1, 2, 3], 'index_term_pair': [[12, 3], [12, 3]]}\ncheck('valid operation', solve(r), True)\ncheck('A snapshot rolls back applied state', solve(dict(r, **{'newer_applied': [9, 10]})), False)\ncheck('An incomplete snapshot replaces the live state', solve(dict(r, **{'complete_chunks': [[0, 2], 3]})), False)\ncheck('Corrupt snapshot contents become authoritative', solve(dict(r, **{'checksum_match': ['bad', 'abc']})), False)\ncheck('The snapshot omits its membership configuration', solve(dict(r, **{'configuration_present': []})), False)\ncheck('Snapshot metadata refers to a different log term', solve(dict(r, **{'index_term_pair': [[12, 2], [12, 3]]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'newer_applied': [9, 10], 'complete_chunks': [[0, 2], 3], 'checksum_match': ['bad', 'abc'], 'configuration_present': [], 'index_term_pair': [[12, 2], [12, 3]]}\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":"310aa3b9cfb8a12b9465238aef0e65282bdbbedf41f4258faf1e862b73c2a351","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (set(r['complete_chunks'][0]) == set(range(r['complete_chunks'][1]))) and (r['checksum_match'][0] == r['checksum_match'][1]) and (bool(r['configuration_present'])) and (r['index_term_pair'][0] == r['index_term_pair'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'newer_applied': [12, 10], 'complete_chunks': [[0, 1, 2], 3], 'checksum_match': ['abc', 'abc'], 'configuration_present': [1, 2, 3], 'index_term_pair': [[12, 3], [12, 3]]}\ncheck('valid operation', solve(r), True)\ncheck('A snapshot rolls back applied state', solve(dict(r, **{'newer_applied': [9, 10]})), False)\ncheck('An incomplete snapshot replaces the live state', solve(dict(r, **{'complete_chunks': [[0, 2], 3]})), False)\ncheck('Corrupt snapshot contents become authoritative', solve(dict(r, **{'checksum_match': ['bad', 'abc']})), False)\ncheck('The snapshot omits its membership configuration', solve(dict(r, **{'configuration_present': []})), False)\ncheck('Snapshot metadata refers to a different log term', solve(dict(r, **{'index_term_pair': [[12, 2], [12, 3]]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'newer_applied': [9, 10], 'complete_chunks': [[0, 2], 3], 'checksum_match': ['bad', 'abc'], 'configuration_present': [], 'index_term_pair': [[12, 2], [12, 3]]}\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":"bdbee3faa7735838124026847fc899ef34d8cf5bb1df90b992c5676216fdb7ea","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['newer_applied'][0] >= r['newer_applied'][1]) and (set(r['complete_chunks'][0]) == set(range(r['complete_chunks'][1]))) and (r['checksum_match'][0] == r['checksum_match'][1]) and (bool(r['configuration_present'])) and (r['index_term_pair'][0] == r['index_term_pair'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'newer_applied': [12, 10], 'complete_chunks': [[0, 1, 2], 3], 'checksum_match': ['abc', 'abc'], 'configuration_present': [1, 2, 3], 'index_term_pair': [[12, 3], [12, 3]]}\ncheck('valid operation', solve(r), True)\ncheck('A snapshot rolls back applied state', solve(dict(r, **{'newer_applied': [9, 10]})), False)\ncheck('An incomplete snapshot replaces the live state', solve(dict(r, **{'complete_chunks': [[0, 2], 3]})), False)\ncheck('Corrupt snapshot contents become authoritative', solve(dict(r, **{'checksum_match': ['bad', 'abc']})), False)\ncheck('The snapshot omits its membership configuration', solve(dict(r, **{'configuration_present': []})), False)\ncheck('Snapshot metadata refers to a different log term', solve(dict(r, **{'index_term_pair': [[12, 2], [12, 3]]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'newer_applied': [9, 10], 'complete_chunks': [[0, 2], 3], 'checksum_match': ['bad', 'abc'], 'configuration_present': [], 'index_term_pair': [[12, 2], [12, 3]]}\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-snapshot-install-newer_applied","generated_at":"2026-09-29T14:36:52.658434+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['newer_applied'][0] >= r['newer_applied'][1] together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the newer applied invariant while validating the other operation preconditions.","sha256":"a123ec2782387a3ae6cb88e54c7bcceed23671f94fd63935b317312c70437f8b","title":"Install a replicated state snapshot: A snapshot rolls back applied state · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":30.987,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A snapshot rolls back applied state","expected":false,"passed":true},{"actual":true,"check":"An incomplete snapshot replaces the live state","expected":false,"passed":false},{"actual":false,"check":"Corrupt snapshot contents become authoritative","expected":false,"passed":true},{"actual":false,"check":"The snapshot omits its membership configuration","expected":false,"passed":true},{"actual":false,"check":"Snapshot metadata refers to a different log term","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 snapshot rolls back applied state\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"An incomplete snapshot replaces the live state\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"Corrupt snapshot contents become authoritative\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The snapshot omits its membership configuration\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Snapshot metadata refers to a different log term\", \"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":31.261,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":true,"check":"A snapshot rolls back applied state","expected":false,"passed":false},{"actual":false,"check":"An incomplete snapshot replaces the live state","expected":false,"passed":true},{"actual":false,"check":"Corrupt snapshot contents become authoritative","expected":false,"passed":true},{"actual":false,"check":"The snapshot omits its membership configuration","expected":false,"passed":true},{"actual":false,"check":"Snapshot metadata refers to a different log term","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 snapshot rolls back applied state\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"An incomplete snapshot replaces the live state\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Corrupt snapshot contents become authoritative\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The snapshot omits its membership configuration\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Snapshot metadata refers to a different log term\", \"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":29.568,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A snapshot rolls back applied state","expected":false,"passed":true},{"actual":false,"check":"An incomplete snapshot replaces the live state","expected":false,"passed":true},{"actual":false,"check":"Corrupt snapshot contents become authoritative","expected":false,"passed":true},{"actual":false,"check":"The snapshot omits its membership configuration","expected":false,"passed":true},{"actual":false,"check":"Snapshot metadata refers to a different log term","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 snapshot rolls back applied state\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"An incomplete snapshot replaces the live state\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Corrupt snapshot contents become authoritative\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"The snapshot omits its membership configuration\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Snapshot metadata refers to a different log term\", \"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"}