{"abstract":"Adding opacities treats overlap as disjoint coverage.","category":"Raster compositing","checks":4,"contract":"Return source-over output alpha for two normalized opacities.","evaluation_group":"xg-source-over-alpha-union","failed_approach":"Taking maximum opacity omits partially overlapping coverage.","family":"xg-source-over-alpha-union","id":"FA-10541","implementations":{"attempt":{"sha256":"3ea08a9793eff899a629a85aa2be0afe8788cb841cf838e66410bad07ad8b6d1","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(source_alpha, destination_alpha):\n    return max(source_alpha,destination_alpha)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(0.5, 0.5)), 0.75)\ncheck('fixture 2', solve(*(0, 0.5)), 0.5)\ncheck('fixture 3', solve(*(1, 0.25)), 1)\ncheck('fixture 4', solve(*(0.25, 0.5)), 0.625)\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":"feac8c56618405f67f4ea32f99f3ad77147ded4edcc33175fbad6fe0ca411a38","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(source_alpha, destination_alpha):\n    return source_alpha+destination_alpha\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(0.5, 0.5)), 0.75)\ncheck('fixture 2', solve(*(0, 0.5)), 0.5)\ncheck('fixture 3', solve(*(1, 0.25)), 1)\ncheck('fixture 4', solve(*(0.25, 0.5)), 0.625)\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":"05049f735f63303c4e89fc3bdd2ee18cf76826e2f6dfa3626879c473b373d0ee","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(source_alpha, destination_alpha):\n    return source_alpha+destination_alpha*(1-source_alpha)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(0.5, 0.5)), 0.75)\ncheck('fixture 2', solve(*(0, 0.5)), 0.5)\ncheck('fixture 3', solve(*(1, 0.25)), 1)\ncheck('fixture 4', solve(*(0.25, 0.5)), 0.625)\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":"xg-source-over-alpha-union","generated_at":"2026-09-29T14:38:39.941818+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic software graphics stage with explicit channel and coordinate conventions; no hardware, device profile or API behavior is inferred.","repair":"Use the stage contract: Return source-over output alpha for two normalized opacities.","root_cause":"Adding opacities treats overlap as disjoint coverage.","sha256":"cf0ab29207486fa9e96267c912572cbea64cbfd547b9f52fc8d2b93b65dee932","title":"Source over alpha union · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":44.81,"exit_code":1,"observations":[{"actual":0.5,"check":"fixture 1","expected":0.75,"passed":false},{"actual":0.5,"check":"fixture 2","expected":0.5,"passed":true},{"actual":1,"check":"fixture 3","expected":1,"passed":true},{"actual":0.5,"check":"fixture 4","expected":0.625,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": 0.5, \"expected\": 0.75, \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": 0.5, \"expected\": 0.5, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 0.5, \"expected\": 0.625, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.199,"exit_code":1,"observations":[{"actual":1.0,"check":"fixture 1","expected":0.75,"passed":false},{"actual":0.5,"check":"fixture 2","expected":0.5,"passed":true},{"actual":1.25,"check":"fixture 3","expected":1,"passed":false},{"actual":0.75,"check":"fixture 4","expected":0.625,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": 1.0, \"expected\": 0.75, \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": 0.5, \"expected\": 0.5, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 1.25, \"expected\": 1, \"passed\": false}, {\"check\": \"fixture 4\", \"actual\": 0.75, \"expected\": 0.625, \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":43.204,"exit_code":0,"observations":[{"actual":0.75,"check":"fixture 1","expected":0.75,"passed":true},{"actual":0.5,"check":"fixture 2","expected":0.5,"passed":true},{"actual":1.0,"check":"fixture 3","expected":1,"passed":true},{"actual":0.625,"check":"fixture 4","expected":0.625,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": 0.75, \"expected\": 0.75, \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": 0.5, \"expected\": 0.5, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 1.0, \"expected\": 1, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 0.625, \"expected\": 0.625, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}