{"abstract":"The checkpoint barrier operation is admitted even though barriers from different checkpoint rounds are combined.","category":"Replication","checks":9,"contract":"Return a Boolean admission decision for complete a streaming checkpoint barrier. The record r must satisfy all of: set(r['all_inputs'][0]) == set(r['all_inputs'][1]); len(set(r['barrier_id'])) == 1; r['state_flushed'] is True; r['inflight_captured'][0] == r['inflight_captured'][1]; r['sink_prepared'] == 'prepared'. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-checkpoint-barrier","failed_approach":"Adding the barrier id check repairs the reported defect, but replacing the adjacent state flushed check loses that independent invariant.","family":"xd-checkpoint-barrier-barrier_id","id":"FA-1556","implementations":{"attempt":{"sha256":"4623e3eef7d45fd15bcf6d06281e66a9f5b2548d27520dfa66fc574b3dba444a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (set(r['all_inputs'][0]) == set(r['all_inputs'][1])) and (len(set(r['barrier_id'])) == 1) and (r['inflight_captured'][0] == r['inflight_captured'][1]) and (r['sink_prepared'] == 'prepared')\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'all_inputs': [['a', 'b'], ['a', 'b']], 'barrier_id': [4, 4], 'state_flushed': True, 'inflight_captured': [8, 8], 'sink_prepared': 'prepared'}\ncheck('valid operation', solve(r), True)\ncheck('A checkpoint completes before every input channel reaches its barrier', solve(dict(r, **{'all_inputs': [['a', 'b'], ['a']]})), False)\ncheck('Barriers from different checkpoint rounds are combined', solve(dict(r, **{'barrier_id': [4, 5]})), False)\ncheck('A checkpoint is acknowledged while state exists only in memory', solve(dict(r, **{'state_flushed': False})), False)\ncheck('Unaligned checkpoint omits messages already in transit', solve(dict(r, **{'inflight_captured': [5, 8]})), False)\ncheck('Upstream progress commits before the transactional sink prepares', solve(dict(r, **{'sink_prepared': 'open'})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'all_inputs': [['a', 'b'], ['a']], 'barrier_id': [4, 5], 'state_flushed': False, 'inflight_captured': [5, 8], 'sink_prepared': 'open'}\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":"b5b569f1d1b829ca0fe12444e59c4406809dcb6fe543b34243b2952e01eb1996","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (set(r['all_inputs'][0]) == set(r['all_inputs'][1])) and (r['state_flushed'] is True) and (r['inflight_captured'][0] == r['inflight_captured'][1]) and (r['sink_prepared'] == 'prepared')\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'all_inputs': [['a', 'b'], ['a', 'b']], 'barrier_id': [4, 4], 'state_flushed': True, 'inflight_captured': [8, 8], 'sink_prepared': 'prepared'}\ncheck('valid operation', solve(r), True)\ncheck('A checkpoint completes before every input channel reaches its barrier', solve(dict(r, **{'all_inputs': [['a', 'b'], ['a']]})), False)\ncheck('Barriers from different checkpoint rounds are combined', solve(dict(r, **{'barrier_id': [4, 5]})), False)\ncheck('A checkpoint is acknowledged while state exists only in memory', solve(dict(r, **{'state_flushed': False})), False)\ncheck('Unaligned checkpoint omits messages already in transit', solve(dict(r, **{'inflight_captured': [5, 8]})), False)\ncheck('Upstream progress commits before the transactional sink prepares', solve(dict(r, **{'sink_prepared': 'open'})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'all_inputs': [['a', 'b'], ['a']], 'barrier_id': [4, 5], 'state_flushed': False, 'inflight_captured': [5, 8], 'sink_prepared': 'open'}\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":"48c9c7fe09f33d1f5b31b9b62dc3af923959683f650e8242ce128d6996236799","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (set(r['all_inputs'][0]) == set(r['all_inputs'][1])) and (len(set(r['barrier_id'])) == 1) and (r['state_flushed'] is True) and (r['inflight_captured'][0] == r['inflight_captured'][1]) and (r['sink_prepared'] == 'prepared')\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'all_inputs': [['a', 'b'], ['a', 'b']], 'barrier_id': [4, 4], 'state_flushed': True, 'inflight_captured': [8, 8], 'sink_prepared': 'prepared'}\ncheck('valid operation', solve(r), True)\ncheck('A checkpoint completes before every input channel reaches its barrier', solve(dict(r, **{'all_inputs': [['a', 'b'], ['a']]})), False)\ncheck('Barriers from different checkpoint rounds are combined', solve(dict(r, **{'barrier_id': [4, 5]})), False)\ncheck('A checkpoint is acknowledged while state exists only in memory', solve(dict(r, **{'state_flushed': False})), False)\ncheck('Unaligned checkpoint omits messages already in transit', solve(dict(r, **{'inflight_captured': [5, 8]})), False)\ncheck('Upstream progress commits before the transactional sink prepares', solve(dict(r, **{'sink_prepared': 'open'})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'all_inputs': [['a', 'b'], ['a']], 'barrier_id': [4, 5], 'state_flushed': False, 'inflight_captured': [5, 8], 'sink_prepared': 'open'}\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-checkpoint-barrier-barrier_id","generated_at":"2026-09-29T14:37:03.635653+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 len(set(r['barrier_id'])) == 1 together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the barrier id invariant while validating the other operation preconditions.","sha256":"47a46b6868576c701bab3d95034e874eeaa9323cc401eeaef95c27e0dd80d056","title":"Complete a streaming checkpoint barrier: Barriers from different checkpoint rounds are combined · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":37.313,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A checkpoint completes before every input channel reaches its barrier","expected":false,"passed":true},{"actual":false,"check":"Barriers from different checkpoint rounds are combined","expected":false,"passed":true},{"actual":true,"check":"A checkpoint is acknowledged while state exists only in memory","expected":false,"passed":false},{"actual":false,"check":"Unaligned checkpoint omits messages already in transit","expected":false,"passed":true},{"actual":false,"check":"Upstream progress commits before the transactional sink prepares","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 checkpoint completes before every input channel reaches its barrier\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Barriers from different checkpoint rounds are combined\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A checkpoint is acknowledged while state exists only in memory\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"Unaligned checkpoint omits messages already in transit\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Upstream progress commits before the transactional sink prepares\", \"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":117.458,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A checkpoint completes before every input channel reaches its barrier","expected":false,"passed":true},{"actual":true,"check":"Barriers from different checkpoint rounds are combined","expected":false,"passed":false},{"actual":false,"check":"A checkpoint is acknowledged while state exists only in memory","expected":false,"passed":true},{"actual":false,"check":"Unaligned checkpoint omits messages already in transit","expected":false,"passed":true},{"actual":false,"check":"Upstream progress commits before the transactional sink prepares","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 checkpoint completes before every input channel reaches its barrier\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Barriers from different checkpoint rounds are combined\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"A checkpoint is acknowledged while state exists only in memory\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Unaligned checkpoint omits messages already in transit\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Upstream progress commits before the transactional sink prepares\", \"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":33.578,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A checkpoint completes before every input channel reaches its barrier","expected":false,"passed":true},{"actual":false,"check":"Barriers from different checkpoint rounds are combined","expected":false,"passed":true},{"actual":false,"check":"A checkpoint is acknowledged while state exists only in memory","expected":false,"passed":true},{"actual":false,"check":"Unaligned checkpoint omits messages already in transit","expected":false,"passed":true},{"actual":false,"check":"Upstream progress commits before the transactional sink prepares","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 checkpoint completes before every input channel reaches its barrier\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Barriers from different checkpoint rounds are combined\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A checkpoint is acknowledged while state exists only in memory\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Unaligned checkpoint omits messages already in transit\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Upstream progress commits before the transactional sink prepares\", \"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"}