{"abstract":"Calls both bases explicitly and duplicates downstream cooperative contributions and changes the required Python-language result.","category":"Method resolution","checks":6,"contract":"Traverse the actual C3 MRO cooperatively, appending each visited class once. Leaf bases are A,B or B,A and both derive from Root; start chooses normal dispatch or super after a specified class. Inputs use the finite Python types shown in the fixtures. An error string denotes the specified caught exception, not an unhandled process failure.","contract_signature":"order, start","evaluation_group":"xl-cooperative-diamond-mro","failed_approach":"The alternative still fails because it hardcodes A delegation to Root and skips a sibling in the MRO.","family":"xl-cooperative-diamond-mro-both-bases-explicit","id":"FA-5101","implementations":{"attempt":{"sha256":"fcd41b67981e24d16a8adf34fc4499f4c3860f9b913d31791cee887846fec5fd","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(order, start):\n    class Root:\n        def trace(self): return ['Root']\n    class A(Root):\n        def trace(self): return ['A']+Root.trace(self)\n    class B(Root):\n        def trace(self): return ['B']+super().trace()\n    def leaf_trace(self): return ['Leaf']+super(Leaf,self).trace()\n    Leaf=type('Leaf',(A,B) if order=='AB' else (B,A),{'trace':leaf_trace})\n    obj=Leaf()\n    if start=='leaf': return obj.trace()\n    if start=='after-leaf': return super(Leaf,obj).trace()\n    if start=='after-A': return super(A,obj).trace()\n    return super(B,obj).trace()\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('left-first diamond', solve('AB', 'leaf'), ['Leaf', 'A', 'B', 'Root'])\ncheck('right-first diamond', solve('BA', 'leaf'), ['Leaf', 'B', 'A', 'Root'])\ncheck('super after leaf', solve('AB', 'after-leaf'), ['A', 'B', 'Root'])\ncheck('super A follows dynamic MRO', solve('AB', 'after-A'), ['B', 'Root'])\ncheck('super B follows dynamic MRO', solve('BA', 'after-B'), ['A', 'Root'])\ncheck('terminal next', solve('AB', 'after-B'), ['Root'])\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":"f161b5777ccb86aec822340f6b36b5d843bb7a140b29f05c7409381bc49f95ee","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(order, start):\n    class Root:\n        def trace(self): return ['Root']\n    class A(Root):\n        def trace(self): return ['A']+super().trace()\n    class B(Root):\n        def trace(self): return ['B']+super().trace()\n    def leaf_trace(self): return ['Leaf']+A.trace(self)+B.trace(self)\n    Leaf=type('Leaf',(A,B) if order=='AB' else (B,A),{'trace':leaf_trace})\n    obj=Leaf()\n    if start=='leaf': return obj.trace()\n    if start=='after-leaf': return super(Leaf,obj).trace()\n    if start=='after-A': return super(A,obj).trace()\n    return super(B,obj).trace()\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('left-first diamond', solve('AB', 'leaf'), ['Leaf', 'A', 'B', 'Root'])\ncheck('right-first diamond', solve('BA', 'leaf'), ['Leaf', 'B', 'A', 'Root'])\ncheck('super after leaf', solve('AB', 'after-leaf'), ['A', 'B', 'Root'])\ncheck('super A follows dynamic MRO', solve('AB', 'after-A'), ['B', 'Root'])\ncheck('super B follows dynamic MRO', solve('BA', 'after-B'), ['A', 'Root'])\ncheck('terminal next', solve('AB', 'after-B'), ['Root'])\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":"xl-cooperative-diamond-mro-both-bases-explicit","generated_at":"2026-09-29T14:37:45.981747+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Runs Python standard-library language operations in a deterministic local reproducer. Literal expected answers are authored independently. Related defects share an evaluation group to avoid benchmark split leakage.","root_cause":"Calls both bases explicitly and duplicates downstream cooperative contributions. The executable reproducer isolates this operation from the rest of the contract.","sha256":"47fb8d86181fa1b3facc36ca50863f3777b707c83a6b727477154c7a6f2a3b07","title":"Cooperative diamond mro: Calls both bases explicitly and duplicates downstream cooperative contributions · case 01","variant":1,"variant_policy":"The five numbered cases rerun the same authored boundary fixtures; they are reproducibility runs, not independent input variants.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":40.017,"exit_code":1,"observations":[{"actual":["Leaf","A","Root"],"check":"left-first diamond","expected":["Leaf","A","B","Root"],"passed":false},{"actual":["Leaf","B","A","Root"],"check":"right-first diamond","expected":["Leaf","B","A","Root"],"passed":true},{"actual":["A","Root"],"check":"super after leaf","expected":["A","B","Root"],"passed":false},{"actual":["B","Root"],"check":"super A follows dynamic MRO","expected":["B","Root"],"passed":true},{"actual":["A","Root"],"check":"super B follows dynamic MRO","expected":["A","Root"],"passed":true},{"actual":["Root"],"check":"terminal next","expected":["Root"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"left-first diamond\", \"actual\": [\"Leaf\", \"A\", \"Root\"], \"expected\": [\"Leaf\", \"A\", \"B\", \"Root\"], \"passed\": false}, {\"check\": \"right-first diamond\", \"actual\": [\"Leaf\", \"B\", \"A\", \"Root\"], \"expected\": [\"Leaf\", \"B\", \"A\", \"Root\"], \"passed\": true}, {\"check\": \"super after leaf\", \"actual\": [\"A\", \"Root\"], \"expected\": [\"A\", \"B\", \"Root\"], \"passed\": false}, {\"check\": \"super A follows dynamic MRO\", \"actual\": [\"B\", \"Root\"], \"expected\": [\"B\", \"Root\"], \"passed\": true}, {\"check\": \"super B follows dynamic MRO\", \"actual\": [\"A\", \"Root\"], \"expected\": [\"A\", \"Root\"], \"passed\": true}, {\"check\": \"terminal next\", \"actual\": [\"Root\"], \"expected\": [\"Root\"], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.628,"exit_code":1,"observations":[{"actual":["Leaf","A","B","Root","B","Root"],"check":"left-first diamond","expected":["Leaf","A","B","Root"],"passed":false},{"actual":["Leaf","A","Root","B","A","Root"],"check":"right-first diamond","expected":["Leaf","B","A","Root"],"passed":false},{"actual":["A","B","Root"],"check":"super after leaf","expected":["A","B","Root"],"passed":true},{"actual":["B","Root"],"check":"super A follows dynamic MRO","expected":["B","Root"],"passed":true},{"actual":["A","Root"],"check":"super B follows dynamic MRO","expected":["A","Root"],"passed":true},{"actual":["Root"],"check":"terminal next","expected":["Root"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"left-first diamond\", \"actual\": [\"Leaf\", \"A\", \"B\", \"Root\", \"B\", \"Root\"], \"expected\": [\"Leaf\", \"A\", \"B\", \"Root\"], \"passed\": false}, {\"check\": \"right-first diamond\", \"actual\": [\"Leaf\", \"A\", \"Root\", \"B\", \"A\", \"Root\"], \"expected\": [\"Leaf\", \"B\", \"A\", \"Root\"], \"passed\": false}, {\"check\": \"super after leaf\", \"actual\": [\"A\", \"B\", \"Root\"], \"expected\": [\"A\", \"B\", \"Root\"], \"passed\": true}, {\"check\": \"super A follows dynamic MRO\", \"actual\": [\"B\", \"Root\"], \"expected\": [\"B\", \"Root\"], \"passed\": true}, {\"check\": \"super B follows dynamic MRO\", \"actual\": [\"A\", \"Root\"], \"expected\": [\"A\", \"Root\"], \"passed\": true}, {\"check\": \"terminal next\", \"actual\": [\"Root\"], \"expected\": [\"Root\"], \"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."}}