{"abstract":"Uniform unit pricing reads the last winner instead of the first loser.","category":"Auction allocation rules","checks":7,"contract":"Each integer bid requests one unit. For positive supply, return the first excluded bid as uniform payment, or zero if demand does not exceed supply. Zero supply returns None.","contract_signature":"bids, supply","evaluation_group":"model-638340c4f02bbb37","failed_approach":"Always taking the lowest bid ignores the actual supply cutoff.","family":"z-auction_matching-supply-losing-price","id":"FA-12696","implementations":{"attempt":{"sha256":"882c41fe11a09de411b1b25a8ac677aeb81d6f839655507a6c729e715ac3fe4b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(bids, supply):\n    return None if supply==0 else (min(bids) if len(bids)>supply else 0)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('interior cutoff', solve([30+N,20,10,5], 2), 10)\ncheck('one supplied', solve([9,7,2], 1), 7)\ncheck('all served', solve([9,7], 2), 0)\ncheck('excess supply', solve([9], 3), 0)\ncheck('empty demand', solve([], 2), 0)\ncheck('zero supply', solve([9], 0), None)\ncheck('tied marginal bids', solve([8,8,8,1], 2), 8)\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":"c9898979a01d3906b7fca6b303bf2f9c1b477842b1e4381aaa41f2a0b7fa4c31","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(bids, supply):\n    return None if supply==0 else (sorted(bids,reverse=True)[min(supply,len(bids))-1] if bids else 0)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('interior cutoff', solve([30+N,20,10,5], 2), 10)\ncheck('one supplied', solve([9,7,2], 1), 7)\ncheck('all served', solve([9,7], 2), 0)\ncheck('excess supply', solve([9], 3), 0)\ncheck('empty demand', solve([], 2), 0)\ncheck('zero supply', solve([9], 0), None)\ncheck('tied marginal bids', solve([8,8,8,1], 2), 8)\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":"Offline toy model with explicit integer inputs; no strategic behavior or real market execution. 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":"z-auction_matching-supply-losing-price","generated_at":"2026-09-29T14:38:59.345075+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Deterministic teaching model for reviewing auction allocation software; not a representation of any venue or financial advice.","root_cause":"The supply cutoff index is shifted into accepted demand.","sha256":"4e1ebc7f9edb1bb0f73191b42b3777a90d2dfe7042cc12cda615e19b3d80605e","title":"Uniform unit pricing reads the last winner instead of the first loser · 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":40.615,"exit_code":1,"observations":[{"actual":5,"check":"interior cutoff","expected":10,"passed":false},{"actual":2,"check":"one supplied","expected":7,"passed":false},{"actual":0,"check":"all served","expected":0,"passed":true},{"actual":0,"check":"excess supply","expected":0,"passed":true},{"actual":0,"check":"empty demand","expected":0,"passed":true},{"actual":null,"check":"zero supply","expected":null,"passed":true},{"actual":1,"check":"tied marginal bids","expected":8,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"interior cutoff\", \"actual\": 5, \"expected\": 10, \"passed\": false}, {\"check\": \"one supplied\", \"actual\": 2, \"expected\": 7, \"passed\": false}, {\"check\": \"all served\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"excess supply\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"empty demand\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"zero supply\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"tied marginal bids\", \"actual\": 1, \"expected\": 8, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.803,"exit_code":1,"observations":[{"actual":20,"check":"interior cutoff","expected":10,"passed":false},{"actual":9,"check":"one supplied","expected":7,"passed":false},{"actual":7,"check":"all served","expected":0,"passed":false},{"actual":9,"check":"excess supply","expected":0,"passed":false},{"actual":0,"check":"empty demand","expected":0,"passed":true},{"actual":null,"check":"zero supply","expected":null,"passed":true},{"actual":8,"check":"tied marginal bids","expected":8,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"interior cutoff\", \"actual\": 20, \"expected\": 10, \"passed\": false}, {\"check\": \"one supplied\", \"actual\": 9, \"expected\": 7, \"passed\": false}, {\"check\": \"all served\", \"actual\": 7, \"expected\": 0, \"passed\": false}, {\"check\": \"excess supply\", \"actual\": 9, \"expected\": 0, \"passed\": false}, {\"check\": \"empty demand\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"zero supply\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"tied marginal bids\", \"actual\": 8, \"expected\": 8, \"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."}}