{"abstract":"A surviving old value wins because the merge removes deletion markers before comparing versions.","category":"Distributed coordination","checks":7,"contract":"Records are [version,kind,value] with kind put or delete. Return the latest value or None when the latest record is a deletion; deletion wins an equal-version put/delete tie. Equal-version put values are assumed identical; the model has no wall-clock conflict resolution.","contract_signature":"records","evaluation_group":"model-e2f64c3fe46b7064","failed_approach":"Making any tombstone permanently dominant also discards legitimate later recreations.","family":"dist-tombstone-reconciliation","id":"FA-076","implementations":{"attempt":{"sha256":"be9b211bb506d50d0a12b0ec0fb16a67c618e364511d8828d34fc7adade5f5c9","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(records):\n    if any(r[1] == 'delete' for r in records):\n        return None\n    return max(records, key=lambda r: r[0])[2] if records else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('new delete suppresses stale put', solve([[N, 'put', 'old'], [N+1, 'delete', None]]), None)\ncheck('later recreation', solve([[N, 'delete', None], [N+1, 'put', 'new']]), 'new')\ncheck('delete wins version tie', solve([[N, 'put', 'old'], [N, 'delete', None]]), None)\ncheck('tie independent of arrival', solve([[N, 'delete', None], [N, 'put', 'old']]), None)\ncheck('newer of two live values', solve([[N, 'put', 'old'], [N+2, 'put', 'new']]), 'new')\ncheck('empty replicas', solve([]), None)\ncheck('only tombstone', solve([[N, 'delete', None]]), None)\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":"6215124347f360e6afeccddaf115baa03285ad3db7d4fcf6ef24e7f7942fd92f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(records):\n    live = [r for r in records if r[1] == 'put']\n    return max(live, key=lambda r: r[0])[2] if live else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('new delete suppresses stale put', solve([[N, 'put', 'old'], [N+1, 'delete', None]]), None)\ncheck('later recreation', solve([[N, 'delete', None], [N+1, 'put', 'new']]), 'new')\ncheck('delete wins version tie', solve([[N, 'put', 'old'], [N, 'delete', None]]), None)\ncheck('tie independent of arrival', solve([[N, 'delete', None], [N, 'put', 'old']]), None)\ncheck('newer of two live values', solve([[N, 'put', 'old'], [N+2, 'put', 'new']]), 'new')\ncheck('empty replicas', solve([]), None)\ncheck('only tombstone', solve([[N, 'delete', None]]), None)\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":" 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":"dist-tombstone-reconciliation","generated_at":"2026-09-29T14:36:50.419225+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Models anti-entropy repair between replicas retaining different parts of a delete/recreate history.","root_cause":"A tombstone is treated as absence rather than a versioned state transition.","sha256":"04c38750a9a047c9c78d563a358c33ecd30939980436284ceaa79fcb1c7455af","title":"Read repair resurrects a deleted record · 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":36.91,"exit_code":1,"observations":[{"actual":null,"check":"new delete suppresses stale put","expected":null,"passed":true},{"actual":null,"check":"later recreation","expected":"new","passed":false},{"actual":null,"check":"delete wins version tie","expected":null,"passed":true},{"actual":null,"check":"tie independent of arrival","expected":null,"passed":true},{"actual":"new","check":"newer of two live values","expected":"new","passed":true},{"actual":null,"check":"empty replicas","expected":null,"passed":true},{"actual":null,"check":"only tombstone","expected":null,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"new delete suppresses stale put\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"later recreation\", \"actual\": null, \"expected\": \"new\", \"passed\": false}, {\"check\": \"delete wins version tie\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"tie independent of arrival\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"newer of two live values\", \"actual\": \"new\", \"expected\": \"new\", \"passed\": true}, {\"check\": \"empty replicas\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"only tombstone\", \"actual\": null, \"expected\": null, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":35.575,"exit_code":1,"observations":[{"actual":"old","check":"new delete suppresses stale put","expected":null,"passed":false},{"actual":"new","check":"later recreation","expected":"new","passed":true},{"actual":"old","check":"delete wins version tie","expected":null,"passed":false},{"actual":"old","check":"tie independent of arrival","expected":null,"passed":false},{"actual":"new","check":"newer of two live values","expected":"new","passed":true},{"actual":null,"check":"empty replicas","expected":null,"passed":true},{"actual":null,"check":"only tombstone","expected":null,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"new delete suppresses stale put\", \"actual\": \"old\", \"expected\": null, \"passed\": false}, {\"check\": \"later recreation\", \"actual\": \"new\", \"expected\": \"new\", \"passed\": true}, {\"check\": \"delete wins version tie\", \"actual\": \"old\", \"expected\": null, \"passed\": false}, {\"check\": \"tie independent of arrival\", \"actual\": \"old\", \"expected\": null, \"passed\": false}, {\"check\": \"newer of two live values\", \"actual\": \"new\", \"expected\": \"new\", \"passed\": true}, {\"check\": \"empty replicas\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"only tombstone\", \"actual\": null, \"expected\": null, \"passed\": true}], \"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."}}