{"abstract":"Channel admins lose receipts of members who disabled them, or non-admins see channel receipts.","category":"Chat ordering and read receipts","checks":8,"contract":"settings[u] is a user's \"send read receipts\" flag (default True). In direct chats a reader is shown only when both the reader and the viewer have receipts enabled (reciprocity). In group chats only the reader's flag matters. In channels only admins see receipts and they see every reader regardless of settings. The viewer never sees their own receipt. Result: sorted visible readers.","evaluation_group":"w2-chat_ordering_and_read_receipts-receipt-visibility","failed_approach":"Using the reader flag in channels shows receipts to every non-admin viewer. The attempted `ok = enabled(u)` still disagrees with a fixture.","family":"w2-chat_ordering_and_read_receipts-receipt-visibility-channel-admin-override","id":"FA-75981","implementations":{"attempt":{"sha256":"b5df47bf5110962065b720d12d8898a059f1691e8b6d4676013b79f194449e51","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(viewer, readers, settings, chat_kind, admins):\n    enabled = lambda u: settings.get(u, True)\n    out = []\n    for u in readers:\n        if u == viewer:\n            continue\n        if chat_kind == 'channel':\n            ok = enabled(u)\n        elif chat_kind == 'direct':\n            ok = enabled(u) and enabled(viewer)\n        else:\n            ok = enabled(u)\n        if ok:\n            out.append(u)\n    return sorted(out)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_CASES = {1: [('missing settings default on', ('v', ['r1'], {}, 'direct', []), ['r1']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r1'], {}, 'group', []), ['r1']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 2: [('missing settings default on', ('v', ['r2'], {}, 'direct', []), ['r2']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r2'], {}, 'group', []), ['r2']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 3: [('missing settings default on', ('v', ['r3'], {}, 'direct', []), ['r3']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r3'], {}, 'group', []), ['r3']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 4: [('missing settings default on', ('v', ['r4'], {}, 'direct', []), ['r4']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r4'], {}, 'group', []), ['r4']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 5: [('missing settings default on', ('v', ['r5'], {}, 'direct', []), ['r5']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r5'], {}, 'group', []), ['r5']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])]}\nfor _label, _args, _expected in _CASES[N]:\n    check(_label, solve(*_args), _expected)\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":"eafdcf052959a081e7388e9124796556c78e685d68ee7e722502c2e81ed6f042","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(viewer, readers, settings, chat_kind, admins):\n    enabled = lambda u: settings.get(u, True)\n    out = []\n    for u in readers:\n        if u == viewer:\n            continue\n        if chat_kind == 'channel':\n            ok = viewer in admins and enabled(u)\n        elif chat_kind == 'direct':\n            ok = enabled(u) and enabled(viewer)\n        else:\n            ok = enabled(u)\n        if ok:\n            out.append(u)\n    return sorted(out)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_CASES = {1: [('missing settings default on', ('v', ['r1'], {}, 'direct', []), ['r1']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r1'], {}, 'group', []), ['r1']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 2: [('missing settings default on', ('v', ['r2'], {}, 'direct', []), ['r2']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r2'], {}, 'group', []), ['r2']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 3: [('missing settings default on', ('v', ['r3'], {}, 'direct', []), ['r3']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r3'], {}, 'group', []), ['r3']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 4: [('missing settings default on', ('v', ['r4'], {}, 'direct', []), ['r4']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r4'], {}, 'group', []), ['r4']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 5: [('missing settings default on', ('v', ['r5'], {}, 'direct', []), ['r5']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r5'], {}, 'group', []), ['r5']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])]}\nfor _label, _args, _expected in _CASES[N]:\n    check(_label, solve(*_args), _expected)\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":"cc76d3fff826f13ffbe45e088089ff8ba069ab5926a314a4b0cb1ca2919a9d60","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(viewer, readers, settings, chat_kind, admins):\n    enabled = lambda u: settings.get(u, True)\n    out = []\n    for u in readers:\n        if u == viewer:\n            continue\n        if chat_kind == 'channel':\n            ok = viewer in admins\n        elif chat_kind == 'direct':\n            ok = enabled(u) and enabled(viewer)\n        else:\n            ok = enabled(u)\n        if ok:\n            out.append(u)\n    return sorted(out)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_CASES = {1: [('missing settings default on', ('v', ['r1'], {}, 'direct', []), ['r1']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r1'], {}, 'group', []), ['r1']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 2: [('missing settings default on', ('v', ['r2'], {}, 'direct', []), ['r2']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r2'], {}, 'group', []), ['r2']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 3: [('missing settings default on', ('v', ['r3'], {}, 'direct', []), ['r3']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r3'], {}, 'group', []), ['r3']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 4: [('missing settings default on', ('v', ['r4'], {}, 'direct', []), ['r4']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r4'], {}, 'group', []), ['r4']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])], 5: [('missing settings default on', ('v', ['r5'], {}, 'direct', []), ['r5']), ('viewer disabled in direct chat', ('v', ['r'], {'v': False}, 'direct', []), []), ('viewer disabled in group', ('v', ['r', 'q'], {'v': False, 'q': False}, 'group', []), ['r']), ('reader disabled in direct chat', ('v', ['r'], {'r': False, 'v': True}, 'direct', []), []), ('channel admin', ('v', ['r', 'q', 'p'], {'r': False}, 'channel', ['v']), ['p', 'q', 'r']), ('channel non-admin', ('v', ['r'], {}, 'channel', ['a']), []), ('own receipt in group', ('v', ['v', 'r5'], {}, 'group', []), ['r5']), ('own receipt in channel as admin', ('v', ['v'], {}, 'channel', ['v']), [])]}\nfor _label, _args, _expected in _CASES[N]:\n    check(_label, solve(*_args), _expected)\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":"Stipulated offline chat model; not a complete messaging protocol, client or server implementation. 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":"w2-chat_ordering_and_read_receipts-receipt-visibility-channel-admin-override","generated_at":"2026-09-29T14:49:12.065696+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Receipt privacy rules differ by conversation type; mistakes leak receipts users disabled or hide ones they may see.","repair":"Use `ok = viewer in admins` for the channel admin override decision and keep every other rule of the model unchanged.","root_cause":"The channel admin override decision evaluates `ok = viewer in admins and enabled(u)` where the contract requires `ok = viewer in admins`.","sha256":"010d667987f8b7f8bc42a52e639cb06df3aef2b55ced11bfda759076081fbaa9","title":"Filter read receipts by privacy settings and chat kind: channel admin override · case 01","variant":1,"variant_policy":"N selects a different enumerated fixture set (shifted clocks, identifiers and sizes); boundary fixtures recur across variants.","verification":{"attempt":{"elapsed_ms":40.94,"exit_code":1,"observations":[{"actual":["r1"],"check":"missing settings default on","expected":["r1"],"passed":true},{"actual":[],"check":"viewer disabled in direct chat","expected":[],"passed":true},{"actual":["r"],"check":"viewer disabled in group","expected":["r"],"passed":true},{"actual":[],"check":"reader disabled in direct chat","expected":[],"passed":true},{"actual":["p","q"],"check":"channel admin","expected":["p","q","r"],"passed":false},{"actual":["r"],"check":"channel non-admin","expected":[],"passed":false},{"actual":["r1"],"check":"own receipt in group","expected":["r1"],"passed":true},{"actual":[],"check":"own receipt in channel as admin","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"missing settings default on\", \"actual\": [\"r1\"], \"expected\": [\"r1\"], \"passed\": true}, {\"check\": \"viewer disabled in direct chat\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"viewer disabled in group\", \"actual\": [\"r\"], \"expected\": [\"r\"], \"passed\": true}, {\"check\": \"reader disabled in direct chat\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"channel admin\", \"actual\": [\"p\", \"q\"], \"expected\": [\"p\", \"q\", \"r\"], \"passed\": false}, {\"check\": \"channel non-admin\", \"actual\": [\"r\"], \"expected\": [], \"passed\": false}, {\"check\": \"own receipt in group\", \"actual\": [\"r1\"], \"expected\": [\"r1\"], \"passed\": true}, {\"check\": \"own receipt in channel as admin\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.832,"exit_code":1,"observations":[{"actual":["r1"],"check":"missing settings default on","expected":["r1"],"passed":true},{"actual":[],"check":"viewer disabled in direct chat","expected":[],"passed":true},{"actual":["r"],"check":"viewer disabled in group","expected":["r"],"passed":true},{"actual":[],"check":"reader disabled in direct chat","expected":[],"passed":true},{"actual":["p","q"],"check":"channel admin","expected":["p","q","r"],"passed":false},{"actual":[],"check":"channel non-admin","expected":[],"passed":true},{"actual":["r1"],"check":"own receipt in group","expected":["r1"],"passed":true},{"actual":[],"check":"own receipt in channel as admin","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"missing settings default on\", \"actual\": [\"r1\"], \"expected\": [\"r1\"], \"passed\": true}, {\"check\": \"viewer disabled in direct chat\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"viewer disabled in group\", \"actual\": [\"r\"], \"expected\": [\"r\"], \"passed\": true}, {\"check\": \"reader disabled in direct chat\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"channel admin\", \"actual\": [\"p\", \"q\"], \"expected\": [\"p\", \"q\", \"r\"], \"passed\": false}, {\"check\": \"channel non-admin\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"own receipt in group\", \"actual\": [\"r1\"], \"expected\": [\"r1\"], \"passed\": true}, {\"check\": \"own receipt in channel as admin\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":42.005,"exit_code":0,"observations":[{"actual":["r1"],"check":"missing settings default on","expected":["r1"],"passed":true},{"actual":[],"check":"viewer disabled in direct chat","expected":[],"passed":true},{"actual":["r"],"check":"viewer disabled in group","expected":["r"],"passed":true},{"actual":[],"check":"reader disabled in direct chat","expected":[],"passed":true},{"actual":["p","q","r"],"check":"channel admin","expected":["p","q","r"],"passed":true},{"actual":[],"check":"channel non-admin","expected":[],"passed":true},{"actual":["r1"],"check":"own receipt in group","expected":["r1"],"passed":true},{"actual":[],"check":"own receipt in channel as admin","expected":[],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"missing settings default on\", \"actual\": [\"r1\"], \"expected\": [\"r1\"], \"passed\": true}, {\"check\": \"viewer disabled in direct chat\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"viewer disabled in group\", \"actual\": [\"r\"], \"expected\": [\"r\"], \"passed\": true}, {\"check\": \"reader disabled in direct chat\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"channel admin\", \"actual\": [\"p\", \"q\", \"r\"], \"expected\": [\"p\", \"q\", \"r\"], \"passed\": true}, {\"check\": \"channel non-admin\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"own receipt in group\", \"actual\": [\"r1\"], \"expected\": [\"r1\"], \"passed\": true}, {\"check\": \"own receipt in channel as admin\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}