{"abstract":"The regional cutover operation is admitted even though a delayed cutover command reverses a newer regional decision.","category":"Reliability","checks":9,"contract":"Return a Boolean admission decision for cut traffic to a replacement region. The record r must satisfy all of: r['replication_caught_up'][0] >= r['replication_caught_up'][1]; r['source_writes_stopped'] is True; all(r['dependency_ready']); r['capacity_headroom'][0]+r['capacity_headroom'][1] <= r['capacity_headroom'][2]; r['cutover_generation'][0] > r['cutover_generation'][1]. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-regional-cutover","failed_approach":"Adding the cutover generation check repairs the reported defect, but replacing the adjacent replication caught up check loses that independent invariant.","family":"xd-regional-cutover-cutover_generation","id":"FA-1596","implementations":{"attempt":{"sha256":"532551d93d22c0616985447b46fcd7655cfeced149322a184530ada19dda36c0","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['source_writes_stopped'] is True) and (all(r['dependency_ready'])) and (r['capacity_headroom'][0]+r['capacity_headroom'][1] <= r['capacity_headroom'][2]) and (r['cutover_generation'][0] > r['cutover_generation'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'replication_caught_up': [30, 30], 'source_writes_stopped': True, 'dependency_ready': [True, True], 'capacity_headroom': [4, 5, 10], 'cutover_generation': [8, 7]}\ncheck('valid operation', solve(r), True)\ncheck('Cutover loses writes beyond the destination applied watermark', solve(dict(r, **{'replication_caught_up': [29, 30]})), False)\ncheck('Both regions accept writes during a single-writer cutover', solve(dict(r, **{'source_writes_stopped': False})), False)\ncheck('Application traffic arrives before regional dependencies are ready', solve(dict(r, **{'dependency_ready': [True, False]})), False)\ncheck('Destination capacity cannot serve the transferred load', solve(dict(r, **{'capacity_headroom': [6, 5, 10]})), False)\ncheck('A delayed cutover command reverses a newer regional decision', solve(dict(r, **{'cutover_generation': [7, 7]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'replication_caught_up': [29, 30], 'source_writes_stopped': False, 'dependency_ready': [True, False], 'capacity_headroom': [6, 5, 10], 'cutover_generation': [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":"9a7041798c3a947f0f4fe4627cb4498bd33ea4e02131a54686e02e82ca6b0c93","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['replication_caught_up'][0] >= r['replication_caught_up'][1]) and (r['source_writes_stopped'] is True) and (all(r['dependency_ready'])) and (r['capacity_headroom'][0]+r['capacity_headroom'][1] <= r['capacity_headroom'][2])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'replication_caught_up': [30, 30], 'source_writes_stopped': True, 'dependency_ready': [True, True], 'capacity_headroom': [4, 5, 10], 'cutover_generation': [8, 7]}\ncheck('valid operation', solve(r), True)\ncheck('Cutover loses writes beyond the destination applied watermark', solve(dict(r, **{'replication_caught_up': [29, 30]})), False)\ncheck('Both regions accept writes during a single-writer cutover', solve(dict(r, **{'source_writes_stopped': False})), False)\ncheck('Application traffic arrives before regional dependencies are ready', solve(dict(r, **{'dependency_ready': [True, False]})), False)\ncheck('Destination capacity cannot serve the transferred load', solve(dict(r, **{'capacity_headroom': [6, 5, 10]})), False)\ncheck('A delayed cutover command reverses a newer regional decision', solve(dict(r, **{'cutover_generation': [7, 7]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'replication_caught_up': [29, 30], 'source_writes_stopped': False, 'dependency_ready': [True, False], 'capacity_headroom': [6, 5, 10], 'cutover_generation': [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":"63d3ae437385c6647c5da1ed7936d71501c6ba47c5a7a73f6502f94452cec68d","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['replication_caught_up'][0] >= r['replication_caught_up'][1]) and (r['source_writes_stopped'] is True) and (all(r['dependency_ready'])) and (r['capacity_headroom'][0]+r['capacity_headroom'][1] <= r['capacity_headroom'][2]) and (r['cutover_generation'][0] > r['cutover_generation'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'replication_caught_up': [30, 30], 'source_writes_stopped': True, 'dependency_ready': [True, True], 'capacity_headroom': [4, 5, 10], 'cutover_generation': [8, 7]}\ncheck('valid operation', solve(r), True)\ncheck('Cutover loses writes beyond the destination applied watermark', solve(dict(r, **{'replication_caught_up': [29, 30]})), False)\ncheck('Both regions accept writes during a single-writer cutover', solve(dict(r, **{'source_writes_stopped': False})), False)\ncheck('Application traffic arrives before regional dependencies are ready', solve(dict(r, **{'dependency_ready': [True, False]})), False)\ncheck('Destination capacity cannot serve the transferred load', solve(dict(r, **{'capacity_headroom': [6, 5, 10]})), False)\ncheck('A delayed cutover command reverses a newer regional decision', solve(dict(r, **{'cutover_generation': [7, 7]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'replication_caught_up': [29, 30], 'source_writes_stopped': False, 'dependency_ready': [True, False], 'capacity_headroom': [6, 5, 10], 'cutover_generation': [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-regional-cutover-cutover_generation","generated_at":"2026-09-29T14:37:03.780740+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic local contract for reliability. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.","repair":"Require r['cutover_generation'][0] > r['cutover_generation'][1] together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the cutover generation invariant while validating the other operation preconditions.","sha256":"c64ec34fa728fe0342ab394681f34e3ec2b6db71dcf67f0f81a5373937bc7979","title":"Cut traffic to a replacement region: A delayed cutover command reverses a newer regional decision · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":35.346,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":true,"check":"Cutover loses writes beyond the destination applied watermark","expected":false,"passed":false},{"actual":false,"check":"Both regions accept writes during a single-writer cutover","expected":false,"passed":true},{"actual":false,"check":"Application traffic arrives before regional dependencies are ready","expected":false,"passed":true},{"actual":false,"check":"Destination capacity cannot serve the transferred load","expected":false,"passed":true},{"actual":false,"check":"A delayed cutover command reverses a newer regional 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\": \"Cutover loses writes beyond the destination applied watermark\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"Both regions accept writes during a single-writer cutover\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Application traffic arrives before regional dependencies are ready\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Destination capacity cannot serve the transferred load\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delayed cutover command reverses a newer regional 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"},"broken":{"elapsed_ms":38.165,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Cutover loses writes beyond the destination applied watermark","expected":false,"passed":true},{"actual":false,"check":"Both regions accept writes during a single-writer cutover","expected":false,"passed":true},{"actual":false,"check":"Application traffic arrives before regional dependencies are ready","expected":false,"passed":true},{"actual":false,"check":"Destination capacity cannot serve the transferred load","expected":false,"passed":true},{"actual":true,"check":"A delayed cutover command reverses a newer regional 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\": \"Cutover loses writes beyond the destination applied watermark\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Both regions accept writes during a single-writer cutover\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Application traffic arrives before regional dependencies are ready\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Destination capacity cannot serve the transferred load\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delayed cutover command reverses a newer regional 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"},"fixed":{"elapsed_ms":39.932,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Cutover loses writes beyond the destination applied watermark","expected":false,"passed":true},{"actual":false,"check":"Both regions accept writes during a single-writer cutover","expected":false,"passed":true},{"actual":false,"check":"Application traffic arrives before regional dependencies are ready","expected":false,"passed":true},{"actual":false,"check":"Destination capacity cannot serve the transferred load","expected":false,"passed":true},{"actual":false,"check":"A delayed cutover command reverses a newer regional 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\": \"Cutover loses writes beyond the destination applied watermark\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Both regions accept writes during a single-writer cutover\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Application traffic arrives before regional dependencies are ready\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Destination capacity cannot serve the transferred load\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delayed cutover command reverses a newer regional 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"}