{"abstract":"Fails to advance the playlist cursor on ordinary fallback and produces an incorrect media-control or presentation result.","category":"Media playlist lifecycle","checks":7,"contract":"Consume the first enabled play-next queue occurrence before advancing the playlist. Queue plays do not move the playlist cursor; disabled queued occurrences are discarded. Return [selected ID or None,remaining queue,new playlist cursor]. Queue duplicates are independent requests.","contract_signature":"playlist, cursor, queue, disabled","evaluation_group":"xplay-play-next-queue","failed_approach":"The alternative still fails because it consumes play-next requests in reverse insertion order.","family":"xplay-play-next-queue-playlist-cursor-stale","id":"FA-11306","implementations":{"attempt":{"sha256":"f1df0f68e351204cdf5e2b388b6891ca706aa5127653f84e1486c446be72805f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(playlist, cursor, queue, disabled):\n    pending=list(queue)\n    while pending:\n        candidate=pending.pop()\n        if candidate in disabled: continue\n        return [candidate,pending,cursor]\n    start=playlist.index(cursor) if cursor in playlist else -1\n    for candidate in playlist[start+1:]:\n        if candidate not in disabled:\n            return [candidate,pending,candidate]\n    return [None,pending,cursor]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('queue has priority', solve(['a', 'b'], 'a', ['x', 'y'], []), ['x', ['y'], 'a'])\ncheck('same track queued twice', solve(['a', 'b'], 'a', ['x', 'x', 'y'], []), ['x', ['x', 'y'], 'a'])\ncheck('disabled queue discarded', solve(['a', 'b'], 'a', ['x', 'y'], ['x']), ['y', [], 'a'])\ncheck('fallback advances cursor', solve(['a', 'b'], 'a', [], []), ['b', [], 'b'])\ncheck('all queued disabled falls back', solve(['a', 'b'], 'a', ['x'], ['x']), ['b', [], 'b'])\ncheck('end has no track', solve(['a'], 'a', [], []), [None, [], 'a'])\ncheck('queue works without playlist', solve([], None, ['x'], []), ['x', [], 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":"5975f79860516f865c42cca4de40fa2102dff978e6a6d50ffb43d826df97156c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(playlist, cursor, queue, disabled):\n    pending=list(queue)\n    while pending:\n        candidate=pending.pop(0)\n        if candidate in disabled: continue\n        return [candidate,pending,cursor]\n    start=playlist.index(cursor) if cursor in playlist else -1\n    for candidate in playlist[start+1:]:\n        if candidate not in disabled:\n            return [candidate,pending,cursor]\n    return [None,pending,cursor]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('queue has priority', solve(['a', 'b'], 'a', ['x', 'y'], []), ['x', ['y'], 'a'])\ncheck('same track queued twice', solve(['a', 'b'], 'a', ['x', 'x', 'y'], []), ['x', ['x', 'y'], 'a'])\ncheck('disabled queue discarded', solve(['a', 'b'], 'a', ['x', 'y'], ['x']), ['y', [], 'a'])\ncheck('fallback advances cursor', solve(['a', 'b'], 'a', [], []), ['b', [], 'b'])\ncheck('all queued disabled falls back', solve(['a', 'b'], 'a', ['x'], ['x']), ['b', [], 'b'])\ncheck('end has no track', solve(['a'], 'a', [], []), [None, [], 'a'])\ncheck('queue works without playlist', solve([], None, ['x'], []), ['x', [], 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":"xplay-play-next-queue-playlist-cursor-stale","generated_at":"2026-09-29T14:38:46.798677+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic in-memory media application model with explicit playlist, timeline or synchronization semantics. Does not implement codecs, transport protocols, rendering hardware or concurrent playback.","root_cause":"Fails to advance the playlist cursor on ordinary fallback. The fixture suite isolates this decision from network delivery and codec details.","sha256":"86d1a5997d670324167ff0e5de96a39d089404ad28636bd534d1ac3bb57ef5ed","title":"Play next queue: Fails to advance the playlist cursor on ordinary fallback · case 01","variant":1,"variant_policy":"Numbered cases repeat the same authored boundary fixtures as reproducibility runs, not independent input variants.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":39.377,"exit_code":1,"observations":[{"actual":["y",["x"],"a"],"check":"queue has priority","expected":["x",["y"],"a"],"passed":false},{"actual":["y",["x","x"],"a"],"check":"same track queued twice","expected":["x",["x","y"],"a"],"passed":false},{"actual":["y",["x"],"a"],"check":"disabled queue discarded","expected":["y",[],"a"],"passed":false},{"actual":["b",[],"b"],"check":"fallback advances cursor","expected":["b",[],"b"],"passed":true},{"actual":["b",[],"b"],"check":"all queued disabled falls back","expected":["b",[],"b"],"passed":true},{"actual":[null,[],"a"],"check":"end has no track","expected":[null,[],"a"],"passed":true},{"actual":["x",[],null],"check":"queue works without playlist","expected":["x",[],null],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"queue has priority\", \"actual\": [\"y\", [\"x\"], \"a\"], \"expected\": [\"x\", [\"y\"], \"a\"], \"passed\": false}, {\"check\": \"same track queued twice\", \"actual\": [\"y\", [\"x\", \"x\"], \"a\"], \"expected\": [\"x\", [\"x\", \"y\"], \"a\"], \"passed\": false}, {\"check\": \"disabled queue discarded\", \"actual\": [\"y\", [\"x\"], \"a\"], \"expected\": [\"y\", [], \"a\"], \"passed\": false}, {\"check\": \"fallback advances cursor\", \"actual\": [\"b\", [], \"b\"], \"expected\": [\"b\", [], \"b\"], \"passed\": true}, {\"check\": \"all queued disabled falls back\", \"actual\": [\"b\", [], \"b\"], \"expected\": [\"b\", [], \"b\"], \"passed\": true}, {\"check\": \"end has no track\", \"actual\": [null, [], \"a\"], \"expected\": [null, [], \"a\"], \"passed\": true}, {\"check\": \"queue works without playlist\", \"actual\": [\"x\", [], null], \"expected\": [\"x\", [], null], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.222,"exit_code":1,"observations":[{"actual":["x",["y"],"a"],"check":"queue has priority","expected":["x",["y"],"a"],"passed":true},{"actual":["x",["x","y"],"a"],"check":"same track queued twice","expected":["x",["x","y"],"a"],"passed":true},{"actual":["y",[],"a"],"check":"disabled queue discarded","expected":["y",[],"a"],"passed":true},{"actual":["b",[],"a"],"check":"fallback advances cursor","expected":["b",[],"b"],"passed":false},{"actual":["b",[],"a"],"check":"all queued disabled falls back","expected":["b",[],"b"],"passed":false},{"actual":[null,[],"a"],"check":"end has no track","expected":[null,[],"a"],"passed":true},{"actual":["x",[],null],"check":"queue works without playlist","expected":["x",[],null],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"queue has priority\", \"actual\": [\"x\", [\"y\"], \"a\"], \"expected\": [\"x\", [\"y\"], \"a\"], \"passed\": true}, {\"check\": \"same track queued twice\", \"actual\": [\"x\", [\"x\", \"y\"], \"a\"], \"expected\": [\"x\", [\"x\", \"y\"], \"a\"], \"passed\": true}, {\"check\": \"disabled queue discarded\", \"actual\": [\"y\", [], \"a\"], \"expected\": [\"y\", [], \"a\"], \"passed\": true}, {\"check\": \"fallback advances cursor\", \"actual\": [\"b\", [], \"a\"], \"expected\": [\"b\", [], \"b\"], \"passed\": false}, {\"check\": \"all queued disabled falls back\", \"actual\": [\"b\", [], \"a\"], \"expected\": [\"b\", [], \"b\"], \"passed\": false}, {\"check\": \"end has no track\", \"actual\": [null, [], \"a\"], \"expected\": [null, [], \"a\"], \"passed\": true}, {\"check\": \"queue works without playlist\", \"actual\": [\"x\", [], null], \"expected\": [\"x\", [], null], \"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."}}