{"abstract":"Serial distance is forward modular distance.","category":"Transport flow control","checks":4,"contract":"Bounded offline decision model: serial distance is forward modular distance. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","contract_signature":"start, end","evaluation_group":"xh-serial-distance-is-forward-modular-distance","failed_approach":"The attempted repair uses `abs(end-start)` and still violates a separate fixture.","family":"xh-serial-distance-is-forward-modular-distance","id":"FA-7236","implementations":{"attempt":{"sha256":"0c16e6bfa4daca2c303dfb3440547b3941bfdcdb2137266e017bb82b2fb218f4","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(start, end):\n    return abs(end-start)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(250, 3), 9)\", \"check('fixture 2', solve(3, 250), 247)\", \"check('fixture 3', solve(10, 10), 0)\", \"check('fixture 4', solve(0, 1), 1)\"]\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":"72b3d52ade77f96d7b67b9e44562fdf3a0aa71aa7aea4ea8d28e453c9eee8d03","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(start, end):\n    return end-start\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(250, 3), 9)\", \"check('fixture 2', solve(3, 250), 247)\", \"check('fixture 3', solve(10, 10), 0)\", \"check('fixture 4', solve(0, 1), 1)\"]\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-serial-distance-is-forward-modular-distance","generated_at":"2026-09-29T14:38:09.770714+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic transport flow control model isolates the serial-distance-is-forward-modular-distance policy at a network component boundary.","root_cause":"The faulty implementation uses `end-start` for the serial-distance-is-forward-modular-distance decision.","sha256":"571314e66ddc43b3f2791848e78d4adb2d8f51a67105e61ac1a16048a087e808","title":"Serial distance is forward modular distance · 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":44.471,"exit_code":1,"observations":[{"actual":247,"check":"fixture 2","expected":247,"passed":true},{"actual":0,"check":"fixture 3","expected":0,"passed":true},{"actual":1,"check":"fixture 4","expected":1,"passed":true},{"actual":247,"check":"fixture 1","expected":9,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": 247, \"expected\": 247, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": 247, \"expected\": 9, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":43.273,"exit_code":1,"observations":[{"actual":247,"check":"fixture 2","expected":247,"passed":true},{"actual":0,"check":"fixture 3","expected":0,"passed":true},{"actual":1,"check":"fixture 4","expected":1,"passed":true},{"actual":-247,"check":"fixture 1","expected":9,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": 247, \"expected\": 247, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": -247, \"expected\": 9, \"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."}}