{"abstract":"The operation returns a result or retained state that violates this contract: Add two counters and retain only strictly positive resulting counts.","category":"Multiset accounting","checks":4,"contract":"Add two counters and retain only strictly positive resulting counts. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","contract_signature":"x, y=None","evaluation_group":"model-7916c2175d677da5","failed_approach":"A nonnegative filter preserves zero entries that should be removed.","family":"xr-counter-addition-drops-nonpositive-sums","id":"FA-4666","implementations":{"attempt":{"sha256":"6096d40ab05c8f9b754edeaf8c616698d14d19d6444d8e9259c1bc8df4b810a2","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom collections import Counter, ChainMap, deque\nimport heapq\nN = 1\nobservations = []\ndef solve(x, y=None):\n    a=Counter(x); a.update(y); return {k:v for k,v in a.items() if v>=0}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('zero removed', solve({'a': 1, 'b': 2}, {'a': -1, 'b': -4}), {})\ncheck('positive retained', solve({'a': 2}, {'a': 1, 'b': 1}), {'a': 3, 'b': 1})\ncheck('empty', solve({}, {}), {})\ncheck('negative left removed', solve({'a': -1}, {'b': 2}), {'b': 2})\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":"e27d2d617c7a99df80ca3772019291fab1069c87940ba660c2781b986b547dc6","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom collections import Counter, ChainMap, deque\nimport heapq\nN = 1\nobservations = []\ndef solve(x, y=None):\n    a=Counter(x); a.update(y); return dict(a)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('zero removed', solve({'a': 1, 'b': 2}, {'a': -1, 'b': -4}), {})\ncheck('positive retained', solve({'a': 2}, {'a': 1, 'b': 1}), {'a': 3, 'b': 1})\ncheck('empty', solve({}, {}), {})\ncheck('negative left removed', solve({'a': -1}, {'b': 2}), {'b': 2})\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":"xr-counter-addition-drops-nonpositive-sums","generated_at":"2026-09-29T14:37:41.506665+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A controlled local-runtime regression for collection APIs, language semantics, or ownership wrappers. Fixtures include boundary and interaction cases.","root_cause":"In-place update retains signed entries that positive-bag addition must discard.","sha256":"8f593350380b3899a506b4f675fced47ebebd93a5b262697b1344a993e2c9027","title":"Counter addition drops nonpositive sums · case 01","variant":1,"variant_policy":"Five execution reruns of a fixed adversarial fixture suite; variant number does not alter semantic inputs.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":36.151,"exit_code":1,"observations":[{"actual":{"a":0},"check":"zero removed","expected":{},"passed":false},{"actual":{"a":3,"b":1},"check":"positive retained","expected":{"a":3,"b":1},"passed":true},{"actual":{},"check":"empty","expected":{},"passed":true},{"actual":{"b":2},"check":"negative left removed","expected":{"b":2},"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"zero removed\", \"actual\": {\"a\": 0}, \"expected\": {}, \"passed\": false}, {\"check\": \"positive retained\", \"actual\": {\"a\": 3, \"b\": 1}, \"expected\": {\"a\": 3, \"b\": 1}, \"passed\": true}, {\"check\": \"empty\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"negative left removed\", \"actual\": {\"b\": 2}, \"expected\": {\"b\": 2}, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":34.52,"exit_code":1,"observations":[{"actual":{"a":0,"b":-2},"check":"zero removed","expected":{},"passed":false},{"actual":{"a":3,"b":1},"check":"positive retained","expected":{"a":3,"b":1},"passed":true},{"actual":{},"check":"empty","expected":{},"passed":true},{"actual":{"a":-1,"b":2},"check":"negative left removed","expected":{"b":2},"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"zero removed\", \"actual\": {\"a\": 0, \"b\": -2}, \"expected\": {}, \"passed\": false}, {\"check\": \"positive retained\", \"actual\": {\"a\": 3, \"b\": 1}, \"expected\": {\"a\": 3, \"b\": 1}, \"passed\": true}, {\"check\": \"empty\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"negative left removed\", \"actual\": {\"a\": -1, \"b\": 2}, \"expected\": {\"b\": 2}, \"passed\": false}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}