{"abstract":"Revalidation 304 merges present fields and retains absent fields.","category":"HTTP caching","checks":4,"contract":"Bounded offline decision model: revalidation 304 merges present fields and retains absent fields. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","evaluation_group":"xh-revalidation-304-merges-present-fields-and-retains-absent-fields","failed_approach":"The attempted repair uses `dict(updates, **stored)` and still violates a separate fixture.","family":"xh-revalidation-304-merges-present-fields-and-retains-absent-fields","id":"FA-6761","implementations":{"attempt":{"sha256":"7c12a05f64096ba6795b4cad3996d3fe0cdfa77f853514a2d3ff58e030603b81","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(stored, updates):\n    return dict(updates, **stored)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve({'etag': 'a', 'type': 'text'}, {'etag': 'b'}), {'etag': 'b', 'type': 'text'})\", \"check('fixture 2', solve({'x': 1}, {}), {'x': 1})\", \"check('fixture 3', solve({}, {'x': 2}), {'x': 2})\", \"check('fixture 4', solve({}, {}), {})\"]\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":"82df867797c69b4f5ec66268f6963f1572a9b26de6c8f6c15ef37c0e83159307","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(stored, updates):\n    return updates\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve({'etag': 'a', 'type': 'text'}, {'etag': 'b'}), {'etag': 'b', 'type': 'text'})\", \"check('fixture 2', solve({'x': 1}, {}), {'x': 1})\", \"check('fixture 3', solve({}, {'x': 2}), {'x': 2})\", \"check('fixture 4', solve({}, {}), {})\"]\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":"93acdffdfc9f12b3796a772f45824e903dd04c5e020062bd3d4aa1ec222e2a34","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(stored, updates):\n    return dict(stored, **updates)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve({'etag': 'a', 'type': 'text'}, {'etag': 'b'}), {'etag': 'b', 'type': 'text'})\", \"check('fixture 2', solve({'x': 1}, {}), {'x': 1})\", \"check('fixture 3', solve({}, {'x': 2}), {'x': 2})\", \"check('fixture 4', solve({}, {}), {})\"]\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-revalidation-304-merges-present-fields-and-retains-absent-fields","generated_at":"2026-09-29T14:38:04.948606+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic http caching model isolates the revalidation-304-merges-present-fields-and-retains-absent-fields policy at a network component boundary.","repair":"Apply the explicit revalidation-304-merges-present-fields-and-retains-absent-fields contract, including the tested boundary and negative cases.","root_cause":"The faulty implementation uses `updates` for the revalidation-304-merges-present-fields-and-retains-absent-fields decision.","sha256":"7a216355ecdd7ae1657a69dfe25d031e21a37443a2829f19327d39ce2918c377","title":"Revalidation 304 merges present fields and retains absent fields · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":38.238,"exit_code":1,"observations":[{"actual":{"x":1},"check":"fixture 2","expected":{"x":1},"passed":true},{"actual":{"x":2},"check":"fixture 3","expected":{"x":2},"passed":true},{"actual":{},"check":"fixture 4","expected":{},"passed":true},{"actual":{"etag":"a","type":"text"},"check":"fixture 1","expected":{"etag":"b","type":"text"},"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": {\"x\": 1}, \"expected\": {\"x\": 1}, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": {\"x\": 2}, \"expected\": {\"x\": 2}, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": {\"etag\": \"a\", \"type\": \"text\"}, \"expected\": {\"etag\": \"b\", \"type\": \"text\"}, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.551,"exit_code":1,"observations":[{"actual":{},"check":"fixture 2","expected":{"x":1},"passed":false},{"actual":{"x":2},"check":"fixture 3","expected":{"x":2},"passed":true},{"actual":{},"check":"fixture 4","expected":{},"passed":true},{"actual":{"etag":"b"},"check":"fixture 1","expected":{"etag":"b","type":"text"},"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": {}, \"expected\": {\"x\": 1}, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": {\"x\": 2}, \"expected\": {\"x\": 2}, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": {\"etag\": \"b\"}, \"expected\": {\"etag\": \"b\", \"type\": \"text\"}, \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":37.794,"exit_code":0,"observations":[{"actual":{"x":1},"check":"fixture 2","expected":{"x":1},"passed":true},{"actual":{"x":2},"check":"fixture 3","expected":{"x":2},"passed":true},{"actual":{},"check":"fixture 4","expected":{},"passed":true},{"actual":{"etag":"b","type":"text"},"check":"fixture 1","expected":{"etag":"b","type":"text"},"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": {\"x\": 1}, \"expected\": {\"x\": 1}, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": {\"x\": 2}, \"expected\": {\"x\": 2}, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": {\"etag\": \"b\", \"type\": \"text\"}, \"expected\": {\"etag\": \"b\", \"type\": \"text\"}, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}