{"abstract":"A second append is started while the previous asynchronous append is still active.","category":"Streaming segment lifecycle","checks":4,"contract":"Schedule at most one source-buffer append: when busy retain queue; otherwise dequeue its head. Return [scheduled ID or None,pending].","contract_signature":"queue, busy","evaluation_group":"xmed-segment-append-must-finish-before-next","failed_approach":"Never dispatching avoids overlap but stalls all queued media.","family":"xmed-segment-append-must-finish-before-next","id":"FA-11166","implementations":{"attempt":{"sha256":"e63efad5c4d6a06cc79c109b64e5e613b816d0672711fa5a9d36bc9c71099f13","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(queue, busy):\n    return [None,list(queue)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*(['a', 'b'], True)),[None, ['a', 'b']])\ncheck('fixture 2',solve(*(['a', 'b'], False)),['a', ['b']])\ncheck('fixture 3',solve(*([], False)),[None, []])\ncheck('fixture 4',solve(*(['a'], False)),['a', []])\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":"74415d1b5301fe6759d76c4c5fc8eb3aaac6dc070c86499044ddbb7617ffd78c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(queue, busy):\n    return [queue[0],queue[1:]] if queue else [None,[]]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*(['a', 'b'], True)),[None, ['a', 'b']])\ncheck('fixture 2',solve(*(['a', 'b'], False)),['a', ['b']])\ncheck('fixture 3',solve(*([], False)),[None, []])\ncheck('fixture 4',solve(*(['a'], False)),['a', []])\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-segment-append-must-finish-before-next","generated_at":"2026-09-29T14:38:45.562380+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.","root_cause":"A second append is started while the previous asynchronous append is still active.","sha256":"2592d6c29c217b110425fc671d4e3bd8252a0bb4bfc0500ebca8282b62ade46f","title":"Segment append must finish before next · 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":41.052,"exit_code":1,"observations":[{"actual":[null,["a","b"]],"check":"fixture 1","expected":[null,["a","b"]],"passed":true},{"actual":[null,["a","b"]],"check":"fixture 2","expected":["a",["b"]],"passed":false},{"actual":[null,[]],"check":"fixture 3","expected":[null,[]],"passed":true},{"actual":[null,["a"]],"check":"fixture 4","expected":["a",[]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [null, [\"a\", \"b\"]], \"expected\": [null, [\"a\", \"b\"]], \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": [null, [\"a\", \"b\"]], \"expected\": [\"a\", [\"b\"]], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [null, []], \"expected\": [null, []], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [null, [\"a\"]], \"expected\": [\"a\", []], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.042,"exit_code":1,"observations":[{"actual":["a",["b"]],"check":"fixture 1","expected":[null,["a","b"]],"passed":false},{"actual":["a",["b"]],"check":"fixture 2","expected":["a",["b"]],"passed":true},{"actual":[null,[]],"check":"fixture 3","expected":[null,[]],"passed":true},{"actual":["a",[]],"check":"fixture 4","expected":["a",[]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [\"a\", [\"b\"]], \"expected\": [null, [\"a\", \"b\"]], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [\"a\", [\"b\"]], \"expected\": [\"a\", [\"b\"]], \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": [null, []], \"expected\": [null, []], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [\"a\", []], \"expected\": [\"a\", []], \"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."}}