{"abstract":"Negotiation failure is distinct from empty representation.","category":"Content negotiation","checks":4,"contract":"Bounded offline decision model: negotiation failure is distinct from empty representation. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","evaluation_group":"xh-negotiation-failure-is-distinct-from-empty-representation","failed_approach":"The attempted repair uses `'ok'` and still violates a separate fixture.","family":"xh-negotiation-failure-is-distinct-from-empty-representation","id":"FA-6936","implementations":{"attempt":{"sha256":"33f8d3100cd226834fe79843e1550d45deb508d0a7f85ed5e4fd8ce0fc4af6f9","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(available, allowed):\n    return 'ok'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(['a'], []), '406')\", \"check('fixture 2', solve([], []), 'ok')\", \"check('fixture 3', solve(['a'], ['a']), 'ok')\", \"check('fixture 4', solve([], ['a']), 'ok')\"]\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":"3baaf943380aaf474d479a290010f229b14f9d1aca1db1877408f70d3c7cabdd","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(available, allowed):\n    return '406' if not allowed else 'ok'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(['a'], []), '406')\", \"check('fixture 2', solve([], []), 'ok')\", \"check('fixture 3', solve(['a'], ['a']), 'ok')\", \"check('fixture 4', solve([], ['a']), 'ok')\"]\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"},"fixed":{"sha256":"eb839c0eea4f37192c2f28c3137b6b8fa35b99c527928b713f76e28c921e3d9c","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(available, allowed):\n    return '406' if available and not allowed else 'ok'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(['a'], []), '406')\", \"check('fixture 2', solve([], []), 'ok')\", \"check('fixture 3', solve(['a'], ['a']), 'ok')\", \"check('fixture 4', solve([], ['a']), 'ok')\"]\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-negotiation-failure-is-distinct-from-empty-representation","generated_at":"2026-09-29T14:38:06.772640+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic content negotiation model isolates the negotiation-failure-is-distinct-from-empty-representation policy at a network component boundary.","repair":"Apply the explicit negotiation-failure-is-distinct-from-empty-representation contract, including the tested boundary and negative cases.","root_cause":"The faulty implementation uses `'406' if not allowed else 'ok'` for the negotiation-failure-is-distinct-from-empty-representation decision.","sha256":"27889ca8e39b7e97b0500eb2506335ddab20fbd70e9680a0e736989928a753ce","title":"Negotiation failure is distinct from empty representation · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":38.174,"exit_code":1,"observations":[{"actual":"ok","check":"fixture 2","expected":"ok","passed":true},{"actual":"ok","check":"fixture 3","expected":"ok","passed":true},{"actual":"ok","check":"fixture 4","expected":"ok","passed":true},{"actual":"ok","check":"fixture 1","expected":"406","passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": \"ok\", \"expected\": \"ok\", \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": \"ok\", \"expected\": \"ok\", \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": \"ok\", \"expected\": \"ok\", \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": \"ok\", \"expected\": \"406\", \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":137.647,"exit_code":1,"observations":[{"actual":"406","check":"fixture 2","expected":"ok","passed":false},{"actual":"ok","check":"fixture 3","expected":"ok","passed":true},{"actual":"ok","check":"fixture 4","expected":"ok","passed":true},{"actual":"406","check":"fixture 1","expected":"406","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": \"406\", \"expected\": \"ok\", \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": \"ok\", \"expected\": \"ok\", \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": \"ok\", \"expected\": \"ok\", \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": \"406\", \"expected\": \"406\", \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":33.634,"exit_code":0,"observations":[{"actual":"ok","check":"fixture 2","expected":"ok","passed":true},{"actual":"ok","check":"fixture 3","expected":"ok","passed":true},{"actual":"ok","check":"fixture 4","expected":"ok","passed":true},{"actual":"406","check":"fixture 1","expected":"406","passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": \"ok\", \"expected\": \"ok\", \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": \"ok\", \"expected\": \"ok\", \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": \"ok\", \"expected\": \"ok\", \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": \"406\", \"expected\": \"406\", \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}