{"abstract":"Send buffer removes only cumulatively acknowledged segments.","category":"Transport flow control","checks":4,"contract":"Bounded offline decision model: send buffer removes only cumulatively acknowledged segments. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","contract_signature":"segments, ack","evaluation_group":"xh-send-buffer-removes-only-cumulatively-acknowledged-segments","failed_approach":"The attempted repair uses `[(s,e) for s,e in segments if e >= ack]` and still violates a separate fixture.","family":"xh-send-buffer-removes-only-cumulatively-acknowledged-segments","id":"FA-7291","implementations":{"attempt":{"sha256":"b9d0cf4721a3f7180785573eaa1ad484650ea64c334c6af3eb010efbd2807659","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(segments, ack):\n    return [(s,e) for s,e in segments if e >= ack]\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), (5, 10)], 5), [(5, 10)])\", \"check('fixture 2', solve([(0, 5)], 3), [(0, 5)])\", \"check('fixture 3', solve([], 0), [])\", \"check('fixture 4', solve([(0, 5)], 5), [])\"]\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":"a73216f82b2b4cb078903662f1eee0468d2ab666a95813b7a93133260632ee87","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(segments, ack):\n    return [(s,e) for s,e in segments if s > ack]\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), (5, 10)], 5), [(5, 10)])\", \"check('fixture 2', solve([(0, 5)], 3), [(0, 5)])\", \"check('fixture 3', solve([], 0), [])\", \"check('fixture 4', solve([(0, 5)], 5), [])\"]\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-send-buffer-removes-only-cumulatively-acknowledged-segments","generated_at":"2026-09-29T14:38:10.350041+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic transport flow control model isolates the send-buffer-removes-only-cumulatively-acknowledged-segments policy at a network component boundary.","root_cause":"The faulty implementation uses `[(s,e) for s,e in segments if s > ack]` for the send-buffer-removes-only-cumulatively-acknowledged-segments decision.","sha256":"59cdbc4f0d4927a9ddc8466adc7ab39357c89890f076ba1c89883dbde2b137c7","title":"Send buffer removes only cumulatively acknowledged segments · 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":52.936,"exit_code":1,"observations":[{"actual":[[0,5]],"check":"fixture 2","expected":[[0,5]],"passed":true},{"actual":[],"check":"fixture 3","expected":[],"passed":true},{"actual":[[0,5]],"check":"fixture 4","expected":[],"passed":false},{"actual":[[0,5],[5,10]],"check":"fixture 1","expected":[[5,10]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": [[0, 5]], \"expected\": [[0, 5]], \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [[0, 5]], \"expected\": [], \"passed\": false}, {\"check\": \"fixture 1\", \"actual\": [[0, 5], [5, 10]], \"expected\": [[5, 10]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":50.574,"exit_code":1,"observations":[{"actual":[],"check":"fixture 2","expected":[[0,5]],"passed":false},{"actual":[],"check":"fixture 3","expected":[],"passed":true},{"actual":[],"check":"fixture 4","expected":[],"passed":true},{"actual":[],"check":"fixture 1","expected":[[5,10]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": [], \"expected\": [[0, 5]], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": [], \"expected\": [[5, 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."}}