{"abstract":"The queue acknowledge operation is admitted even though cumulative acknowledgement jumps over an unprocessed delivery.","category":"Queues","checks":9,"contract":"Return a Boolean admission decision for settle a queue delivery acknowledgement. The record r must satisfy all of: r['receipt_handle'][0] == r['receipt_handle'][1]; r['lease_live'][0] < r['lease_live'][1]; r['channel_scope'][0] == r['channel_scope'][1]; r['settlement_once'] is False; all(r['batch_prefix']). Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-queue-acknowledge","failed_approach":"Adding the batch prefix check repairs the reported defect, but replacing the adjacent receipt handle check loses that independent invariant.","family":"xd-queue-acknowledge-batch_prefix","id":"FA-796","implementations":{"attempt":{"sha256":"77874a193bd345a57d8bc6044bd1b75bd69244dd14c47b666773991e26cd1f67","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['lease_live'][0] < r['lease_live'][1]) and (r['channel_scope'][0] == r['channel_scope'][1]) and (r['settlement_once'] is False) and (all(r['batch_prefix']))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'receipt_handle': ['h2', 'h2'], 'lease_live': [8, 9], 'channel_scope': ['c2', 'c2'], 'settlement_once': False, 'batch_prefix': [True, True, True]}\ncheck('valid operation', solve(r), True)\ncheck('A receipt from an older delivery deletes the current message', solve(dict(r, **{'receipt_handle': ['h1', 'h2']})), False)\ncheck('An acknowledgement settles an already expired reservation', solve(dict(r, **{'lease_live': [9, 9]})), False)\ncheck('A delivery tag from another channel is settled', solve(dict(r, **{'channel_scope': ['c1', 'c2']})), False)\ncheck('A second settlement credits the consumer twice', solve(dict(r, **{'settlement_once': True})), False)\ncheck('Cumulative acknowledgement jumps over an unprocessed delivery', solve(dict(r, **{'batch_prefix': [True, False, True]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'receipt_handle': ['h1', 'h2'], 'lease_live': [9, 9], 'channel_scope': ['c1', 'c2'], 'settlement_once': True, 'batch_prefix': [True, False, True]}\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":"b98b42fb097e4b5e8af099a931238639ec3a84c04cced979c4e5980040fa7597","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['receipt_handle'][0] == r['receipt_handle'][1]) and (r['lease_live'][0] < r['lease_live'][1]) and (r['channel_scope'][0] == r['channel_scope'][1]) and (r['settlement_once'] is False)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'receipt_handle': ['h2', 'h2'], 'lease_live': [8, 9], 'channel_scope': ['c2', 'c2'], 'settlement_once': False, 'batch_prefix': [True, True, True]}\ncheck('valid operation', solve(r), True)\ncheck('A receipt from an older delivery deletes the current message', solve(dict(r, **{'receipt_handle': ['h1', 'h2']})), False)\ncheck('An acknowledgement settles an already expired reservation', solve(dict(r, **{'lease_live': [9, 9]})), False)\ncheck('A delivery tag from another channel is settled', solve(dict(r, **{'channel_scope': ['c1', 'c2']})), False)\ncheck('A second settlement credits the consumer twice', solve(dict(r, **{'settlement_once': True})), False)\ncheck('Cumulative acknowledgement jumps over an unprocessed delivery', solve(dict(r, **{'batch_prefix': [True, False, True]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'receipt_handle': ['h1', 'h2'], 'lease_live': [9, 9], 'channel_scope': ['c1', 'c2'], 'settlement_once': True, 'batch_prefix': [True, False, True]}\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":"81c12c323a149fb7e710ab7f3bdc6eca3d9e07adc199fb81244c4a0887a7daeb","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['receipt_handle'][0] == r['receipt_handle'][1]) and (r['lease_live'][0] < r['lease_live'][1]) and (r['channel_scope'][0] == r['channel_scope'][1]) and (r['settlement_once'] is False) and (all(r['batch_prefix']))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'receipt_handle': ['h2', 'h2'], 'lease_live': [8, 9], 'channel_scope': ['c2', 'c2'], 'settlement_once': False, 'batch_prefix': [True, True, True]}\ncheck('valid operation', solve(r), True)\ncheck('A receipt from an older delivery deletes the current message', solve(dict(r, **{'receipt_handle': ['h1', 'h2']})), False)\ncheck('An acknowledgement settles an already expired reservation', solve(dict(r, **{'lease_live': [9, 9]})), False)\ncheck('A delivery tag from another channel is settled', solve(dict(r, **{'channel_scope': ['c1', 'c2']})), False)\ncheck('A second settlement credits the consumer twice', solve(dict(r, **{'settlement_once': True})), False)\ncheck('Cumulative acknowledgement jumps over an unprocessed delivery', solve(dict(r, **{'batch_prefix': [True, False, True]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'receipt_handle': ['h1', 'h2'], 'lease_live': [9, 9], 'channel_scope': ['c1', 'c2'], 'settlement_once': True, 'batch_prefix': [True, False, True]}\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-queue-acknowledge-batch_prefix","generated_at":"2026-09-29T14:36:56.064109+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic local contract for queues. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.","repair":"Require all(r['batch_prefix']) together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the batch prefix invariant while validating the other operation preconditions.","sha256":"cbe828df1c34a7aec555a7ac1f804721b28f04095c54d111632e835db4ea9e04","title":"Settle a queue delivery acknowledgement: Cumulative acknowledgement jumps over an unprocessed delivery · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":33.689,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":true,"check":"A receipt from an older delivery deletes the current message","expected":false,"passed":false},{"actual":false,"check":"An acknowledgement settles an already expired reservation","expected":false,"passed":true},{"actual":false,"check":"A delivery tag from another channel is settled","expected":false,"passed":true},{"actual":false,"check":"A second settlement credits the consumer twice","expected":false,"passed":true},{"actual":false,"check":"Cumulative acknowledgement jumps over an unprocessed delivery","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 receipt from an older delivery deletes the current message\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"An acknowledgement settles an already expired reservation\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delivery tag from another channel is settled\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A second settlement credits the consumer twice\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Cumulative acknowledgement jumps over an unprocessed delivery\", \"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":33.431,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A receipt from an older delivery deletes the current message","expected":false,"passed":true},{"actual":false,"check":"An acknowledgement settles an already expired reservation","expected":false,"passed":true},{"actual":false,"check":"A delivery tag from another channel is settled","expected":false,"passed":true},{"actual":false,"check":"A second settlement credits the consumer twice","expected":false,"passed":true},{"actual":true,"check":"Cumulative acknowledgement jumps over an unprocessed delivery","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\": \"A receipt from an older delivery deletes the current message\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"An acknowledgement settles an already expired reservation\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delivery tag from another channel is settled\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A second settlement credits the consumer twice\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Cumulative acknowledgement jumps over an unprocessed delivery\", \"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":33.478,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A receipt from an older delivery deletes the current message","expected":false,"passed":true},{"actual":false,"check":"An acknowledgement settles an already expired reservation","expected":false,"passed":true},{"actual":false,"check":"A delivery tag from another channel is settled","expected":false,"passed":true},{"actual":false,"check":"A second settlement credits the consumer twice","expected":false,"passed":true},{"actual":false,"check":"Cumulative acknowledgement jumps over an unprocessed delivery","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 receipt from an older delivery deletes the current message\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"An acknowledgement settles an already expired reservation\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A delivery tag from another channel is settled\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A second settlement credits the consumer twice\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Cumulative acknowledgement jumps over an unprocessed delivery\", \"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"}