{"abstract":"The operation returns a result or retained state that violates this contract: Enumerate the entire stream starting at the supplied counter value; offset does not skip source values.","category":"Iterator consumption","checks":4,"contract":"Enumerate the entire stream starting at the supplied counter value; offset does not skip source values. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","evaluation_group":"model-e866c659e979a327","failed_approach":"Ignoring the configured starting counter produces incorrect labels.","family":"xr-enumerate-offset-affects-index-not-source","id":"FA-4636","implementations":{"attempt":{"sha256":"66038a7a1baed483969aa83086472cf21185afcea1838e7b8cc187446dc59fbd","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport itertools as it\nfrom collections import deque\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [[i,v] for i,v in enumerate(x)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('positive start', solve(['a', 'b'], 3), [[3, 'a'], [4, 'b']])\ncheck('negative start', solve(['a', 'b'], -2), [[-2, 'a'], [-1, 'b']])\ncheck('zero start', solve(['a'], 0), [[0, 'a']])\ncheck('empty', solve([], 4), [])\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":"90439d311997b284c884b451ddb63d2343ac1c00ab21776bbcd956c77e8a5cfc","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport itertools as it\nfrom collections import deque\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [[i,v] for i,v in enumerate(x[y:],y)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('positive start', solve(['a', 'b'], 3), [[3, 'a'], [4, 'b']])\ncheck('negative start', solve(['a', 'b'], -2), [[-2, 'a'], [-1, 'b']])\ncheck('zero start', solve(['a'], 0), [[0, 'a']])\ncheck('empty', solve([], 4), [])\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":"9ca893a90c8aa4d7ea4bc1110fdefd160ce58beb5f20ab30727a4e7c30b83ccb","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport itertools as it\nfrom collections import deque\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [[i,v] for i,v in enumerate(x,y)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('positive start', solve(['a', 'b'], 3), [[3, 'a'], [4, 'b']])\ncheck('negative start', solve(['a', 'b'], -2), [[-2, 'a'], [-1, 'b']])\ncheck('zero start', solve(['a'], 0), [[0, 'a']])\ncheck('empty', solve([], 4), [])\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-enumerate-offset-affects-index-not-source","generated_at":"2026-09-29T14:37:41.313773+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.","repair":"Enumerate the entire stream starting at the supplied counter value; offset does not skip source values.","root_cause":"The output counter offset is incorrectly used to skip source positions.","sha256":"18418bbfe23f7a1f5c37b004835f634d70cbc4b5c41b10e9a3302f003b69cb9f","title":"Enumerate offset affects index not source · case 01","variant":1,"variant_policy":"Five execution reruns of a fixed adversarial fixture suite; variant number does not alter semantic inputs.","verification":{"attempt":{"elapsed_ms":37.326,"exit_code":1,"observations":[{"actual":[[0,"a"],[1,"b"]],"check":"positive start","expected":[[3,"a"],[4,"b"]],"passed":false},{"actual":[[0,"a"],[1,"b"]],"check":"negative start","expected":[[-2,"a"],[-1,"b"]],"passed":false},{"actual":[[0,"a"]],"check":"zero start","expected":[[0,"a"]],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"positive start\", \"actual\": [[0, \"a\"], [1, \"b\"]], \"expected\": [[3, \"a\"], [4, \"b\"]], \"passed\": false}, {\"check\": \"negative start\", \"actual\": [[0, \"a\"], [1, \"b\"]], \"expected\": [[-2, \"a\"], [-1, \"b\"]], \"passed\": false}, {\"check\": \"zero start\", \"actual\": [[0, \"a\"]], \"expected\": [[0, \"a\"]], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":36.135,"exit_code":1,"observations":[{"actual":[],"check":"positive start","expected":[[3,"a"],[4,"b"]],"passed":false},{"actual":[[-2,"a"],[-1,"b"]],"check":"negative start","expected":[[-2,"a"],[-1,"b"]],"passed":true},{"actual":[[0,"a"]],"check":"zero start","expected":[[0,"a"]],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"positive start\", \"actual\": [], \"expected\": [[3, \"a\"], [4, \"b\"]], \"passed\": false}, {\"check\": \"negative start\", \"actual\": [[-2, \"a\"], [-1, \"b\"]], \"expected\": [[-2, \"a\"], [-1, \"b\"]], \"passed\": true}, {\"check\": \"zero start\", \"actual\": [[0, \"a\"]], \"expected\": [[0, \"a\"]], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":34.346,"exit_code":0,"observations":[{"actual":[[3,"a"],[4,"b"]],"check":"positive start","expected":[[3,"a"],[4,"b"]],"passed":true},{"actual":[[-2,"a"],[-1,"b"]],"check":"negative start","expected":[[-2,"a"],[-1,"b"]],"passed":true},{"actual":[[0,"a"]],"check":"zero start","expected":[[0,"a"]],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"positive start\", \"actual\": [[3, \"a\"], [4, \"b\"]], \"expected\": [[3, \"a\"], [4, \"b\"]], \"passed\": true}, {\"check\": \"negative start\", \"actual\": [[-2, \"a\"], [-1, \"b\"]], \"expected\": [[-2, \"a\"], [-1, \"b\"]], \"passed\": true}, {\"check\": \"zero start\", \"actual\": [[0, \"a\"]], \"expected\": [[0, \"a\"]], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}