{"abstract":"Sack reports out of order blocks without changing cumulative ack.","category":"Transport flow control","checks":4,"contract":"Bounded offline decision model: sack reports out of order blocks without changing cumulative ack. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","contract_signature":"blocks, next_","evaluation_group":"xh-sack-reports-out-of-order-blocks-without-changing-cumulative-ack","failed_approach":"The attempted repair uses `[(s,e) for s,e in blocks if e > next_]` and still violates a separate fixture.","family":"xh-sack-reports-out-of-order-blocks-without-changing-cumulative-ack","id":"FA-7301","implementations":{"attempt":{"sha256":"7123099455b09234be11deeaa4f2aa2321fbb04a100a62981f1e79a52c32524c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport ipaddress\nimport re\nfrom urllib.parse import urlsplit, urljoin\nN = 1\nobservations = []\ndef solve(blocks, next_):\n    return [(s,e) for s,e in blocks if e > next_]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve([(0, 5), (8, 10)], 5), [(8, 10)])\", \"check('fixture 2', solve([(3, 8)], 5), [])\", \"check('fixture 3', solve([], 5), [])\", \"check('fixture 4', solve([(9, 10)], 5), [(9, 10)])\"]\nfor _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:\n    exec(_line)\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":"f54bebb0a7575c6cbf95a0285e9eb6a4e2ed11c4883a18988228d7b1cb07e6a4","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport ipaddress\nimport re\nfrom urllib.parse import urlsplit, urljoin\nN = 1\nobservations = []\ndef solve(blocks, next_):\n    return blocks\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve([(0, 5), (8, 10)], 5), [(8, 10)])\", \"check('fixture 2', solve([(3, 8)], 5), [])\", \"check('fixture 3', solve([], 5), [])\", \"check('fixture 4', solve([(9, 10)], 5), [(9, 10)])\"]\nfor _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:\n    exec(_line)\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":"Bounded deterministic policy model over validated inputs; not a complete protocol stack or an interoperability claim. The five variants rotate the same explicit fixture set. 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":"xh-sack-reports-out-of-order-blocks-without-changing-cumulative-ack","generated_at":"2026-09-29T14:38:10.453232+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic transport flow control model isolates the sack-reports-out-of-order-blocks-without-changing-cumulative-ack policy at a network component boundary.","root_cause":"The faulty implementation uses `blocks` for the sack-reports-out-of-order-blocks-without-changing-cumulative-ack decision.","sha256":"3e7f6ef6a1a6eb56b91a7500ad0d51ec47dd12dea4098e2ba2db267599d1e124","title":"Sack reports out of order blocks without changing cumulative ack · 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":44.477,"exit_code":1,"observations":[{"actual":[[3,8]],"check":"fixture 2","expected":[],"passed":false},{"actual":[],"check":"fixture 3","expected":[],"passed":true},{"actual":[[9,10]],"check":"fixture 4","expected":[[9,10]],"passed":true},{"actual":[[8,10]],"check":"fixture 1","expected":[[8,10]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": [[3, 8]], \"expected\": [], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [[9, 10]], \"expected\": [[9, 10]], \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": [[8, 10]], \"expected\": [[8, 10]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":47.417,"exit_code":1,"observations":[{"actual":[[3,8]],"check":"fixture 2","expected":[],"passed":false},{"actual":[],"check":"fixture 3","expected":[],"passed":true},{"actual":[[9,10]],"check":"fixture 4","expected":[[9,10]],"passed":true},{"actual":[[0,5],[8,10]],"check":"fixture 1","expected":[[8,10]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": [[3, 8]], \"expected\": [], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [[9, 10]], \"expected\": [[9, 10]], \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": [[0, 5], [8, 10]], \"expected\": [[8, 10]], \"passed\": false}], \"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."}}