{"abstract":"The first matching chapter remains selected throughout later chapters.","category":"Media timeline seeking","checks":4,"contract":"Chapters are sorted unique start times. Select the latest chapter starting at or before playback time; no earlier chapter yields None.","evaluation_group":"xmed-chapter-selection-latest-start","failed_approach":"Strict comparison keeps the preceding chapter at an exact chapter boundary.","family":"xmed-chapter-selection-latest-start","id":"FA-11251","implementations":{"attempt":{"sha256":"7e7611733229edc095e68a0324b7828579fbadd1bf362bd1b7346bedeb99b568","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(chapters, time):\n    return next((name for start,name in reversed(chapters) if start<time),None)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*([[0, 'a'], [10, 'b'], [20, 'c']], 15)),'b')\ncheck('fixture 2',solve(*([[0, 'a'], [10, 'b']], 10)),'b')\ncheck('fixture 3',solve(*([[5, 'a']], 2)),None)\ncheck('fixture 4',solve(*([], 0)),None)\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":"7a8e700257720c4e04345751a2788fd5095c692db8f8079af42343fc31ee41bd","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(chapters, time):\n    return next((name for start,name in chapters if start<=time),None)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*([[0, 'a'], [10, 'b'], [20, 'c']], 15)),'b')\ncheck('fixture 2',solve(*([[0, 'a'], [10, 'b']], 10)),'b')\ncheck('fixture 3',solve(*([[5, 'a']], 2)),None)\ncheck('fixture 4',solve(*([], 0)),None)\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":"540d6713052a0c851c7ae893e8e7baaee3077a206d65dbb9195ae5d4bf4530cc","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(chapters, time):\n    return next((name for start,name in reversed(chapters) if start<=time),None)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*([[0, 'a'], [10, 'b'], [20, 'c']], 15)),'b')\ncheck('fixture 2',solve(*([[0, 'a'], [10, 'b']], 10)),'b')\ncheck('fixture 3',solve(*([[5, 'a']], 2)),None)\ncheck('fixture 4',solve(*([], 0)),None)\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":"xmed-chapter-selection-latest-start","generated_at":"2026-09-29T14:38:46.219978+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic local media controller stage; metadata and downloaded data are supplied explicitly. No external player, service or codec is required.","repair":"Preserve the media contract: Chapters are sorted unique start times. Select the latest chapter starting at or before playback time; no earlier chapter yields None.","root_cause":"The first matching chapter remains selected throughout later chapters.","sha256":"fec8bccf7ec55518dea897278f81ccd1e7e1a04b9dd857d02a8226072a2a1429","title":"Chapter selection latest start · case 01","variant":1,"variant_policy":"The five numbered cases rerun the same authored boundary fixtures; they are reproducibility runs, not independent input variants.","verification":{"attempt":{"elapsed_ms":37.019,"exit_code":1,"observations":[{"actual":"b","check":"fixture 1","expected":"b","passed":true},{"actual":"a","check":"fixture 2","expected":"b","passed":false},{"actual":null,"check":"fixture 3","expected":null,"passed":true},{"actual":null,"check":"fixture 4","expected":null,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": \"b\", \"expected\": \"b\", \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": \"a\", \"expected\": \"b\", \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": null, \"expected\": null, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":37.092,"exit_code":1,"observations":[{"actual":"a","check":"fixture 1","expected":"b","passed":false},{"actual":"a","check":"fixture 2","expected":"b","passed":false},{"actual":null,"check":"fixture 3","expected":null,"passed":true},{"actual":null,"check":"fixture 4","expected":null,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": \"a\", \"expected\": \"b\", \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": \"a\", \"expected\": \"b\", \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": null, \"expected\": null, \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":39.323,"exit_code":0,"observations":[{"actual":"b","check":"fixture 1","expected":"b","passed":true},{"actual":"b","check":"fixture 2","expected":"b","passed":true},{"actual":null,"check":"fixture 3","expected":null,"passed":true},{"actual":null,"check":"fixture 4","expected":null,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": \"b\", \"expected\": \"b\", \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": \"b\", \"expected\": \"b\", \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": null, \"expected\": null, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}