{"abstract":"The work steal operation is admitted even though a worker steals a task requiring unsupported capabilities.","category":"Concurrency","checks":9,"contract":"Return a Boolean admission decision for steal a task from another worker deque. The record r must satisfy all of: r['task_unstarted'] == 'queued'; r['deque_revision'][0] == r['deque_revision'][1]; set(r['capability_match'][0]) <= set(r['capability_match'][1]); r['locality_constraint'][0] is None or r['locality_constraint'][0] == r['locality_constraint'][1]; r['thief_capacity'][0] < r['thief_capacity'][1]. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-work-steal","failed_approach":"Adding the capability match check repairs the reported defect, but replacing the adjacent locality constraint check loses that independent invariant.","family":"xd-work-steal-capability_match","id":"FA-1536","implementations":{"attempt":{"sha256":"eb178dffc6ef8966b6b2ba687edec91942621c2841ed515ac2148128ecce8bed","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['task_unstarted'] == 'queued') and (r['deque_revision'][0] == r['deque_revision'][1]) and (set(r['capability_match'][0]) <= set(r['capability_match'][1])) and (r['thief_capacity'][0] < r['thief_capacity'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'task_unstarted': 'queued', 'deque_revision': [10, 10], 'capability_match': [['gpu'], ['gpu', 'cpu']], 'locality_constraint': ['z1', 'z1'], 'thief_capacity': [2, 3]}\ncheck('valid operation', solve(r), True)\ncheck('A thief executes a task already started by its owner', solve(dict(r, **{'task_unstarted': 'running'})), False)\ncheck('A thief uses a deque position after the deque changed', solve(dict(r, **{'deque_revision': [9, 10]})), False)\ncheck('A worker steals a task requiring unsupported capabilities', solve(dict(r, **{'capability_match': [['gpu'], ['cpu']]})), False)\ncheck('A pinned task leaves its required execution locality', solve(dict(r, **{'locality_constraint': ['z1', 'z2']})), False)\ncheck('Work stealing exceeds the thief execution slots', solve(dict(r, **{'thief_capacity': [3, 3]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'task_unstarted': 'running', 'deque_revision': [9, 10], 'capability_match': [['gpu'], ['cpu']], 'locality_constraint': ['z1', 'z2'], 'thief_capacity': [3, 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":"bcc929099da8945e58c09e41bdbf2242972fc2106cda73edc2b4f68c7a34d949","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['task_unstarted'] == 'queued') and (r['deque_revision'][0] == r['deque_revision'][1]) and (r['locality_constraint'][0] is None or r['locality_constraint'][0] == r['locality_constraint'][1]) and (r['thief_capacity'][0] < r['thief_capacity'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'task_unstarted': 'queued', 'deque_revision': [10, 10], 'capability_match': [['gpu'], ['gpu', 'cpu']], 'locality_constraint': ['z1', 'z1'], 'thief_capacity': [2, 3]}\ncheck('valid operation', solve(r), True)\ncheck('A thief executes a task already started by its owner', solve(dict(r, **{'task_unstarted': 'running'})), False)\ncheck('A thief uses a deque position after the deque changed', solve(dict(r, **{'deque_revision': [9, 10]})), False)\ncheck('A worker steals a task requiring unsupported capabilities', solve(dict(r, **{'capability_match': [['gpu'], ['cpu']]})), False)\ncheck('A pinned task leaves its required execution locality', solve(dict(r, **{'locality_constraint': ['z1', 'z2']})), False)\ncheck('Work stealing exceeds the thief execution slots', solve(dict(r, **{'thief_capacity': [3, 3]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'task_unstarted': 'running', 'deque_revision': [9, 10], 'capability_match': [['gpu'], ['cpu']], 'locality_constraint': ['z1', 'z2'], 'thief_capacity': [3, 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":"dee7b72dcd9a63402bc4b8fdb78bcda7d827bb35300feceaf98b64192a4a9ed0","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['task_unstarted'] == 'queued') and (r['deque_revision'][0] == r['deque_revision'][1]) and (set(r['capability_match'][0]) <= set(r['capability_match'][1])) and (r['locality_constraint'][0] is None or r['locality_constraint'][0] == r['locality_constraint'][1]) and (r['thief_capacity'][0] < r['thief_capacity'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'task_unstarted': 'queued', 'deque_revision': [10, 10], 'capability_match': [['gpu'], ['gpu', 'cpu']], 'locality_constraint': ['z1', 'z1'], 'thief_capacity': [2, 3]}\ncheck('valid operation', solve(r), True)\ncheck('A thief executes a task already started by its owner', solve(dict(r, **{'task_unstarted': 'running'})), False)\ncheck('A thief uses a deque position after the deque changed', solve(dict(r, **{'deque_revision': [9, 10]})), False)\ncheck('A worker steals a task requiring unsupported capabilities', solve(dict(r, **{'capability_match': [['gpu'], ['cpu']]})), False)\ncheck('A pinned task leaves its required execution locality', solve(dict(r, **{'locality_constraint': ['z1', 'z2']})), False)\ncheck('Work stealing exceeds the thief execution slots', solve(dict(r, **{'thief_capacity': [3, 3]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'task_unstarted': 'running', 'deque_revision': [9, 10], 'capability_match': [['gpu'], ['cpu']], 'locality_constraint': ['z1', 'z2'], 'thief_capacity': [3, 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-work-steal-capability_match","generated_at":"2026-09-29T14:37:03.052654+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 set(r['capability_match'][0]) <= set(r['capability_match'][1]) together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the capability match invariant while validating the other operation preconditions.","sha256":"bc54e4ae39665b680f7d87935c3f70ae5bd57685af81d17dd90f8a51a1c55029","title":"Steal a task from another worker deque: A worker steals a task requiring unsupported capabilities · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":33.257,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A thief executes a task already started by its owner","expected":false,"passed":true},{"actual":false,"check":"A thief uses a deque position after the deque changed","expected":false,"passed":true},{"actual":false,"check":"A worker steals a task requiring unsupported capabilities","expected":false,"passed":true},{"actual":true,"check":"A pinned task leaves its required execution locality","expected":false,"passed":false},{"actual":false,"check":"Work stealing exceeds the thief execution slots","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 thief executes a task already started by its owner\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A thief uses a deque position after the deque changed\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A worker steals a task requiring unsupported capabilities\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A pinned task leaves its required execution locality\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"Work stealing exceeds the thief execution slots\", \"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":33.264,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A thief executes a task already started by its owner","expected":false,"passed":true},{"actual":false,"check":"A thief uses a deque position after the deque changed","expected":false,"passed":true},{"actual":true,"check":"A worker steals a task requiring unsupported capabilities","expected":false,"passed":false},{"actual":false,"check":"A pinned task leaves its required execution locality","expected":false,"passed":true},{"actual":false,"check":"Work stealing exceeds the thief execution slots","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 thief executes a task already started by its owner\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A thief uses a deque position after the deque changed\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A worker steals a task requiring unsupported capabilities\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"A pinned task leaves its required execution locality\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Work stealing exceeds the thief execution slots\", \"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":35.886,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A thief executes a task already started by its owner","expected":false,"passed":true},{"actual":false,"check":"A thief uses a deque position after the deque changed","expected":false,"passed":true},{"actual":false,"check":"A worker steals a task requiring unsupported capabilities","expected":false,"passed":true},{"actual":false,"check":"A pinned task leaves its required execution locality","expected":false,"passed":true},{"actual":false,"check":"Work stealing exceeds the thief execution slots","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 thief executes a task already started by its owner\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A thief uses a deque position after the deque changed\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A worker steals a task requiring unsupported capabilities\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A pinned task leaves its required execution locality\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Work stealing exceeds the thief execution slots\", \"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"}