{"abstract":"Earlier configuration layers override later ones.","category":"Configuration","checks":8,"contract":"Merge mappings left to right. None deletes a key, false and zero are retained, lists replace instead of concatenate, and mapping values replace atomically.","contract_signature":"layers","evaluation_group":"xt-config-overlay","failed_approach":"The attempted repair substitutes for layer in layers[:1]:. Fixture 2 still yields {'a': 1} instead of {'a': 2}.","family":"xt-config-overlay-precedence","id":"FA-9581","implementations":{"attempt":{"sha256":"c6267dd0f9026f63c42abda87ae7f7a9b683744be9736565cc96ed0d680f1844","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(layers):\n    result = {}\n    for layer in layers[:1]:\n        for key, value in layer.items():\n            if value is None: result.pop(key, None)\n            else: result[key] = value\n    return result\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve([]), {})\ncheck('fixture 2', solve([{'a': 1}, {'a': 2}]), {'a': 2})\ncheck('fixture 3', solve([{'a': 1}, {'a': None}]), {})\ncheck('fixture 4', solve([{'a': True}, {'a': False}]), {'a': False})\ncheck('fixture 5', solve([{'a': 2}, {'a': 0}]), {'a': 0})\ncheck('fixture 6', solve([{'a': [1]}, {'a': [2]}]), {'a': [2]})\ncheck('fixture 7', solve([{'a': {'x': 1}}, {'a': {'y': 2}}]), {'a': {'y': 2}})\ncheck('fixture 8', solve([{'a': 1}, {'b': 2}]), {'a': 1, '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":"c57ee74f1b4013b714498d98e9d7fea13cf7f6c8e23948b7e765234736ffbd15","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(layers):\n    result = {}\n    for layer in reversed(layers):\n        for key, value in layer.items():\n            if value is None: result.pop(key, None)\n            else: result[key] = value\n    return result\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve([]), {})\ncheck('fixture 2', solve([{'a': 1}, {'a': 2}]), {'a': 2})\ncheck('fixture 3', solve([{'a': 1}, {'a': None}]), {})\ncheck('fixture 4', solve([{'a': True}, {'a': False}]), {'a': False})\ncheck('fixture 5', solve([{'a': 2}, {'a': 0}]), {'a': 0})\ncheck('fixture 6', solve([{'a': [1]}, {'a': [2]}]), {'a': [2]})\ncheck('fixture 7', solve([{'a': {'x': 1}}, {'a': {'y': 2}}]), {'a': {'y': 2}})\ncheck('fixture 8', solve([{'a': 1}, {'b': 2}]), {'a': 1, '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":"xt-config-overlay-precedence","generated_at":"2026-09-29T14:38:31.455809+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"An offline model of explicit configuration overlay, suitable for testing build and release tooling without external services.","root_cause":"The implementation substitutes for layer in reversed(layers): for for layer in layers:, so earlier configuration layers override later ones.","sha256":"bc06c5cc32408cfaadfc01d18a53e4ac5c71f22b215577d99cad692ea4c8e310","title":"Explicit configuration overlay: Earlier configuration layers override later ones · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":39.799,"exit_code":1,"observations":[{"actual":{},"check":"fixture 1","expected":{},"passed":true},{"actual":{"a":1},"check":"fixture 2","expected":{"a":2},"passed":false},{"actual":{"a":1},"check":"fixture 3","expected":{},"passed":false},{"actual":{"a":true},"check":"fixture 4","expected":{"a":false},"passed":false},{"actual":{"a":2},"check":"fixture 5","expected":{"a":0},"passed":false},{"actual":{"a":[1]},"check":"fixture 6","expected":{"a":[2]},"passed":false},{"actual":{"a":{"x":1}},"check":"fixture 7","expected":{"a":{"y":2}},"passed":false},{"actual":{"a":1},"check":"fixture 8","expected":{"a":1,"b":2},"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": {\"a\": 1}, \"expected\": {\"a\": 2}, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": {\"a\": 1}, \"expected\": {}, \"passed\": false}, {\"check\": \"fixture 4\", \"actual\": {\"a\": true}, \"expected\": {\"a\": false}, \"passed\": false}, {\"check\": \"fixture 5\", \"actual\": {\"a\": 2}, \"expected\": {\"a\": 0}, \"passed\": false}, {\"check\": \"fixture 6\", \"actual\": {\"a\": [1]}, \"expected\": {\"a\": [2]}, \"passed\": false}, {\"check\": \"fixture 7\", \"actual\": {\"a\": {\"x\": 1}}, \"expected\": {\"a\": {\"y\": 2}}, \"passed\": false}, {\"check\": \"fixture 8\", \"actual\": {\"a\": 1}, \"expected\": {\"a\": 1, \"b\": 2}, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.128,"exit_code":1,"observations":[{"actual":{},"check":"fixture 1","expected":{},"passed":true},{"actual":{"a":1},"check":"fixture 2","expected":{"a":2},"passed":false},{"actual":{"a":1},"check":"fixture 3","expected":{},"passed":false},{"actual":{"a":true},"check":"fixture 4","expected":{"a":false},"passed":false},{"actual":{"a":2},"check":"fixture 5","expected":{"a":0},"passed":false},{"actual":{"a":[1]},"check":"fixture 6","expected":{"a":[2]},"passed":false},{"actual":{"a":{"x":1}},"check":"fixture 7","expected":{"a":{"y":2}},"passed":false},{"actual":{"a":1,"b":2},"check":"fixture 8","expected":{"a":1,"b":2},"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": {\"a\": 1}, \"expected\": {\"a\": 2}, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": {\"a\": 1}, \"expected\": {}, \"passed\": false}, {\"check\": \"fixture 4\", \"actual\": {\"a\": true}, \"expected\": {\"a\": false}, \"passed\": false}, {\"check\": \"fixture 5\", \"actual\": {\"a\": 2}, \"expected\": {\"a\": 0}, \"passed\": false}, {\"check\": \"fixture 6\", \"actual\": {\"a\": [1]}, \"expected\": {\"a\": [2]}, \"passed\": false}, {\"check\": \"fixture 7\", \"actual\": {\"a\": {\"x\": 1}}, \"expected\": {\"a\": {\"y\": 2}}, \"passed\": false}, {\"check\": \"fixture 8\", \"actual\": {\"b\": 2, \"a\": 1}, \"expected\": {\"a\": 1, \"b\": 2}, \"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."}}