{"abstract":"The compare and swap operation is admitted even though a stale writer replaces a newer revision.","category":"Concurrency","checks":9,"contract":"Return a Boolean admission decision for apply a remote conditional state update. The record r must satisfy all of: r['revision_match'][0] == r['revision_match'][1]; r['object_incarnation'][0] == r['object_incarnation'][1]; r['expected_existence'] is False; tuple(r['transition_allowed'][0]) in [tuple(x) for x in r['transition_allowed'][1]]; r['revision_increment'][0] == r['revision_increment'][1]+1. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-compare-and-swap","failed_approach":"Adding the revision match check repairs the reported defect, but replacing the adjacent object incarnation check loses that independent invariant.","family":"xd-compare-and-swap-revision_match","id":"FA-1426","implementations":{"attempt":{"sha256":"191c08d458523689984b03879101fb7b231858a0c21fc9d5a93bdcf1c088cf7c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['revision_match'][0] == r['revision_match'][1]) and (r['expected_existence'] is False) and (tuple(r['transition_allowed'][0]) in [tuple(x) for x in r['transition_allowed'][1]]) and (r['revision_increment'][0] == r['revision_increment'][1]+1)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'revision_match': [7, 7], 'object_incarnation': ['g2', 'g2'], 'expected_existence': False, 'transition_allowed': [['open', 'closed'], [['open', 'closed']]], 'revision_increment': [8, 7]}\ncheck('valid operation', solve(r), True)\ncheck('A stale writer replaces a newer revision', solve(dict(r, **{'revision_match': [6, 7]})), False)\ncheck('Delete and recreate produces an ABA match on reused revision', solve(dict(r, **{'object_incarnation': ['g1', 'g2']})), False)\ncheck('A create-only write replaces an existing object', solve(dict(r, **{'expected_existence': True})), False)\ncheck('A conditional update performs an illegal lifecycle transition', solve(dict(r, **{'transition_allowed': [['closed', 'open'], [['open', 'closed']]]})), False)\ncheck('A successful update fails to advance the revision', solve(dict(r, **{'revision_increment': [7, 7]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'revision_match': [6, 7], 'object_incarnation': ['g1', 'g2'], 'expected_existence': True, 'transition_allowed': [['closed', 'open'], [['open', 'closed']]], 'revision_increment': [7, 7]}\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":"e2df964727d783f5b20119c97a96069686d50a303bea28825201d8bc67aadf45","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['object_incarnation'][0] == r['object_incarnation'][1]) and (r['expected_existence'] is False) and (tuple(r['transition_allowed'][0]) in [tuple(x) for x in r['transition_allowed'][1]]) and (r['revision_increment'][0] == r['revision_increment'][1]+1)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'revision_match': [7, 7], 'object_incarnation': ['g2', 'g2'], 'expected_existence': False, 'transition_allowed': [['open', 'closed'], [['open', 'closed']]], 'revision_increment': [8, 7]}\ncheck('valid operation', solve(r), True)\ncheck('A stale writer replaces a newer revision', solve(dict(r, **{'revision_match': [6, 7]})), False)\ncheck('Delete and recreate produces an ABA match on reused revision', solve(dict(r, **{'object_incarnation': ['g1', 'g2']})), False)\ncheck('A create-only write replaces an existing object', solve(dict(r, **{'expected_existence': True})), False)\ncheck('A conditional update performs an illegal lifecycle transition', solve(dict(r, **{'transition_allowed': [['closed', 'open'], [['open', 'closed']]]})), False)\ncheck('A successful update fails to advance the revision', solve(dict(r, **{'revision_increment': [7, 7]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'revision_match': [6, 7], 'object_incarnation': ['g1', 'g2'], 'expected_existence': True, 'transition_allowed': [['closed', 'open'], [['open', 'closed']]], 'revision_increment': [7, 7]}\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":"ec729cf5227b413021a5648beabc2283556e30e4e77d77a7fdfa98659adebf4b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['revision_match'][0] == r['revision_match'][1]) and (r['object_incarnation'][0] == r['object_incarnation'][1]) and (r['expected_existence'] is False) and (tuple(r['transition_allowed'][0]) in [tuple(x) for x in r['transition_allowed'][1]]) and (r['revision_increment'][0] == r['revision_increment'][1]+1)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'revision_match': [7, 7], 'object_incarnation': ['g2', 'g2'], 'expected_existence': False, 'transition_allowed': [['open', 'closed'], [['open', 'closed']]], 'revision_increment': [8, 7]}\ncheck('valid operation', solve(r), True)\ncheck('A stale writer replaces a newer revision', solve(dict(r, **{'revision_match': [6, 7]})), False)\ncheck('Delete and recreate produces an ABA match on reused revision', solve(dict(r, **{'object_incarnation': ['g1', 'g2']})), False)\ncheck('A create-only write replaces an existing object', solve(dict(r, **{'expected_existence': True})), False)\ncheck('A conditional update performs an illegal lifecycle transition', solve(dict(r, **{'transition_allowed': [['closed', 'open'], [['open', 'closed']]]})), False)\ncheck('A successful update fails to advance the revision', solve(dict(r, **{'revision_increment': [7, 7]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'revision_match': [6, 7], 'object_incarnation': ['g1', 'g2'], 'expected_existence': True, 'transition_allowed': [['closed', 'open'], [['open', 'closed']]], 'revision_increment': [7, 7]}\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-compare-and-swap-revision_match","generated_at":"2026-09-29T14:37:02.254698+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 r['revision_match'][0] == r['revision_match'][1] together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the revision match invariant while validating the other operation preconditions.","sha256":"ada28eaf3d3f76d72f25e1aeedc23c416fd27c241826c063d98248f9813bcee1","title":"Apply a remote conditional state update: A stale writer replaces a newer revision · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":39.427,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A stale writer replaces a newer revision","expected":false,"passed":true},{"actual":true,"check":"Delete and recreate produces an ABA match on reused revision","expected":false,"passed":false},{"actual":false,"check":"A create-only write replaces an existing object","expected":false,"passed":true},{"actual":false,"check":"A conditional update performs an illegal lifecycle transition","expected":false,"passed":true},{"actual":false,"check":"A successful update fails to advance the revision","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 stale writer replaces a newer revision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Delete and recreate produces an ABA match on reused revision\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"A create-only write replaces an existing object\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A conditional update performs an illegal lifecycle transition\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A successful update fails to advance the revision\", \"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":43.73,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":true,"check":"A stale writer replaces a newer revision","expected":false,"passed":false},{"actual":false,"check":"Delete and recreate produces an ABA match on reused revision","expected":false,"passed":true},{"actual":false,"check":"A create-only write replaces an existing object","expected":false,"passed":true},{"actual":false,"check":"A conditional update performs an illegal lifecycle transition","expected":false,"passed":true},{"actual":false,"check":"A successful update fails to advance the revision","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 stale writer replaces a newer revision\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"Delete and recreate produces an ABA match on reused revision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A create-only write replaces an existing object\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A conditional update performs an illegal lifecycle transition\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A successful update fails to advance the revision\", \"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":42.146,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A stale writer replaces a newer revision","expected":false,"passed":true},{"actual":false,"check":"Delete and recreate produces an ABA match on reused revision","expected":false,"passed":true},{"actual":false,"check":"A create-only write replaces an existing object","expected":false,"passed":true},{"actual":false,"check":"A conditional update performs an illegal lifecycle transition","expected":false,"passed":true},{"actual":false,"check":"A successful update fails to advance the revision","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 stale writer replaces a newer revision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Delete and recreate produces an ABA match on reused revision\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A create-only write replaces an existing object\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A conditional update performs an illegal lifecycle transition\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A successful update fails to advance the revision\", \"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"}