{"abstract":"The operation returns a result or retained state that violates this contract: The parents view removes only the current first scope and retains remaining scope boundaries; an empty parent chain exposes one empty map.","category":"Scoped mappings","checks":4,"contract":"The parents view removes only the current first scope and retains remaining scope boundaries; an empty parent chain exposes one empty map. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","contract_signature":"x, y=None","evaluation_group":"model-469be15ebd0eae04","failed_approach":"Flattening all bindings loses both parent-only membership and scope boundaries.","family":"xr-chainmap-parents-drops-exactly-one-scope","id":"FA-4736","implementations":{"attempt":{"sha256":"6789e006983d01774e7c4c3d5982a3dba2df02d86fd3d2b5c52bafde6007cbcc","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    return [dict(ChainMap(*x))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('two scopes', solve([{'a': 1}, {'a': 2}]), [{'a': 2}])\ncheck('three scopes', solve([{'a': 1}, {'b': 2}, {'c': 3}]), [{'b': 2}, {'c': 3}])\ncheck('one scope', solve([{'a': 1}]), [{}])\ncheck('one empty scope', solve([{}]), [{}])\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":"f56dff541d748a9d94088dff63d2889b23d2aac7f1a5ffd8125f572bf3411320","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    return x\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('two scopes', solve([{'a': 1}, {'a': 2}]), [{'a': 2}])\ncheck('three scopes', solve([{'a': 1}, {'b': 2}, {'c': 3}]), [{'b': 2}, {'c': 3}])\ncheck('one scope', solve([{'a': 1}]), [{}])\ncheck('one empty scope', solve([{}]), [{}])\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-chainmap-parents-drops-exactly-one-scope","generated_at":"2026-09-29T14:37:42.187593+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":"The current scope remains in the parents view.","sha256":"90f3e7e7d12710c2e665853f3c12501e84e5ca9e8717237d1b7ac3b0bd447747","title":"Chainmap parents drops exactly one scope · 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":40.511,"exit_code":1,"observations":[{"actual":[{"a":1}],"check":"two scopes","expected":[{"a":2}],"passed":false},{"actual":[{"a":1,"b":2,"c":3}],"check":"three scopes","expected":[{"b":2},{"c":3}],"passed":false},{"actual":[{"a":1}],"check":"one scope","expected":[{}],"passed":false},{"actual":[{}],"check":"one empty scope","expected":[{}],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"two scopes\", \"actual\": [{\"a\": 1}], \"expected\": [{\"a\": 2}], \"passed\": false}, {\"check\": \"three scopes\", \"actual\": [{\"c\": 3, \"b\": 2, \"a\": 1}], \"expected\": [{\"b\": 2}, {\"c\": 3}], \"passed\": false}, {\"check\": \"one scope\", \"actual\": [{\"a\": 1}], \"expected\": [{}], \"passed\": false}, {\"check\": \"one empty scope\", \"actual\": [{}], \"expected\": [{}], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.56,"exit_code":1,"observations":[{"actual":[{"a":1},{"a":2}],"check":"two scopes","expected":[{"a":2}],"passed":false},{"actual":[{"a":1},{"b":2},{"c":3}],"check":"three scopes","expected":[{"b":2},{"c":3}],"passed":false},{"actual":[{"a":1}],"check":"one scope","expected":[{}],"passed":false},{"actual":[{}],"check":"one empty scope","expected":[{}],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"two scopes\", \"actual\": [{\"a\": 1}, {\"a\": 2}], \"expected\": [{\"a\": 2}], \"passed\": false}, {\"check\": \"three scopes\", \"actual\": [{\"a\": 1}, {\"b\": 2}, {\"c\": 3}], \"expected\": [{\"b\": 2}, {\"c\": 3}], \"passed\": false}, {\"check\": \"one scope\", \"actual\": [{\"a\": 1}], \"expected\": [{}], \"passed\": false}, {\"check\": \"one empty scope\", \"actual\": [{}], \"expected\": [{}], \"passed\": true}], \"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."}}