FA-76251 / Chat ordering and read receipts / Open access

Summarize a thread root's replies: latest reply · case 01

The latest-reply pointer targets a deleted reply.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The latest reply decision evaluates `max((m['seq'] for m in messages if m['root'] == root), default=None)` where the contract requires `replies[-1]['seq'] if replies else None`.

THE FAILURE

The latest reply decision evaluates `max((m['seq'] for m in messages if m['root'] == root), default=None)` where the contract requires `replies[-1]['seq'] if replies else None`.

Unsuccessful approach: Taking the first reply points at the oldest reply. The attempted `replies[0]['seq'] if replies else None` still disagrees with a fixture.

Case contract

messages {seq, root, author, deleted}; replies of a thread have root equal to the root seq (the root itself has root None). Deleted replies are ignored. Result {count, faces: first three distinct reply authors in order of their first reply, more: number of further distinct authors, last: seq of the newest reply or None}.

Why this case matters

Thread summaries sit under the root message and drive navigation into the thread.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(messages, root):
    replies = sorted((m for m in messages if m['root'] == root and not m['deleted']), key=lambda m: m['seq'])
    seen = []
    for m in replies:
        if m['author'] not in seen:
            seen.append(m['author'])
    return {'count': len(replies), 'faces': seen[:3], 'more': max(0, len(seen) - 3),
            'last': max((m['seq'] for m in messages if m['root'] == root), default=None)}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 10, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 10, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u4', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u0', 'u1'], 'last': 19, 'more': 2}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})], 2: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 11, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 11, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u1', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u5', 'u0'], 'last': 19, 'more': 3}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})], 3: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 12, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 12, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 6, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u5', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u5', 'u6'], 'last': 19, 'more': 4}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})], 4: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 13, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 13, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 7, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u7', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u7', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u3', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u5', 'u6'], 'last': 19, 'more': 5}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})], 5: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 14, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 14, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 8, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u7', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u8', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u7', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u8', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u1', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u5', 'u6'], 'last': 19, 'more': 6}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})]}
for _label, _args, _expected in _CASES[N]:
    check(_label, solve(*_args), _expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
root is not a reply	`{'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}`	`{'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}`	Passed
reply order by seq	`{'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 10, 'more': 0}`	`{'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 10, 'more': 0}`	Passed
few authors	`{'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}`	`{'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}`	Passed
newest reply deleted	`{'count': 1, 'faces': ['a'], 'last': 4, 'more': 0}`	`{'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}`	Failed
alternating authors	`{'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}`	`{'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}`	Passed
many authors	`{'count': 16, 'faces': ['u4', 'u0', 'u1'], 'last': 19, 'more': 2}`	`{'count': 16, 'faces': ['u4', 'u0', 'u1'], 'last': 19, 'more': 2}`	Passed
no replies	`{'count': 0, 'faces': [], 'last': None, 'more': 0}`	`{'count': 0, 'faces': [], 'last': None, 'more': 0}`	Passed

SHA-256 / f6cf70eb3935c0dd94b042c019c95bf9ba95be51f10469899a097e9a56eda839

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(messages, root):
    replies = sorted((m for m in messages if m['root'] == root and not m['deleted']), key=lambda m: m['seq'])
    seen = []
    for m in replies:
        if m['author'] not in seen:
            seen.append(m['author'])
    return {'count': len(replies), 'faces': seen[:3], 'more': max(0, len(seen) - 3),
            'last': replies[0]['seq'] if replies else None}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 10, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 10, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u4', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u0', 'u1'], 'last': 19, 'more': 2}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})], 2: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 11, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 11, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u1', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u5', 'u0'], 'last': 19, 'more': 3}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})], 3: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 12, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 12, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 6, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u5', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u5', 'u6'], 'last': 19, 'more': 4}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})], 4: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 13, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 13, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 7, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u7', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u7', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u3', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u5', 'u6'], 'last': 19, 'more': 5}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})], 5: [('root is not a reply', ([{'seq': 5, 'root': None, 'author': 'al', 'deleted': False}, {'seq': 6, 'root': 5, 'author': 'bo', 'deleted': False}, {'seq': 7, 'root': None, 'author': 'cy', 'deleted': False}], 5), {'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}), ('reply order by seq', ([{'seq': 14, 'root': 1, 'author': 'zed', 'deleted': False}, {'seq': 3, 'root': 1, 'author': 'amy', 'deleted': False}, {'seq': 4, 'root': 1, 'author': 'kim', 'deleted': False}], 1), {'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 14, 'more': 0}), ('few authors', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('newest reply deleted', ([{'seq': 2, 'root': 1, 'author': 'a', 'deleted': False}, {'seq': 8, 'root': 1, 'author': 'b', 'deleted': True}], 1), {'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}), ('alternating authors', ([{'seq': 1, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 2, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 3, 'root': 0, 'author': 'b', 'deleted': False}, {'seq': 4, 'root': 0, 'author': 'a', 'deleted': False}, {'seq': 5, 'root': 0, 'author': 'b', 'deleted': False}], 0), {'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}), ('many authors', ([{'seq': 4, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 5, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 6, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 7, 'root': 3, 'author': 'u7', 'deleted': False}, {'seq': 8, 'root': 3, 'author': 'u8', 'deleted': False}, {'seq': 9, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 10, 'root': 3, 'author': 'u1', 'deleted': False}, {'seq': 11, 'root': 3, 'author': 'u2', 'deleted': False}, {'seq': 12, 'root': 3, 'author': 'u3', 'deleted': False}, {'seq': 13, 'root': 3, 'author': 'u4', 'deleted': False}, {'seq': 14, 'root': 3, 'author': 'u5', 'deleted': False}, {'seq': 15, 'root': 3, 'author': 'u6', 'deleted': False}, {'seq': 16, 'root': 3, 'author': 'u7', 'deleted': False}, {'seq': 17, 'root': 3, 'author': 'u8', 'deleted': False}, {'seq': 18, 'root': 3, 'author': 'u0', 'deleted': False}, {'seq': 19, 'root': 3, 'author': 'u1', 'deleted': False}], 3), {'count': 16, 'faces': ['u4', 'u5', 'u6'], 'last': 19, 'more': 6}), ('no replies', ([{'seq': 1, 'root': None, 'author': 'a', 'deleted': False}], 1), {'count': 0, 'faces': [], 'last': None, 'more': 0})]}
for _label, _args, _expected in _CASES[N]:
    check(_label, solve(*_args), _expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
root is not a reply	`{'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}`	`{'count': 1, 'faces': ['bo'], 'last': 6, 'more': 0}`	Passed
reply order by seq	`{'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 3, 'more': 0}`	`{'count': 3, 'faces': ['amy', 'kim', 'zed'], 'last': 10, 'more': 0}`	Failed
few authors	`{'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}`	`{'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}`	Passed
newest reply deleted	`{'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}`	`{'count': 1, 'faces': ['a'], 'last': 2, 'more': 0}`	Passed
alternating authors	`{'count': 5, 'faces': ['b', 'a'], 'last': 1, 'more': 0}`	`{'count': 5, 'faces': ['b', 'a'], 'last': 5, 'more': 0}`	Failed
many authors	`{'count': 16, 'faces': ['u4', 'u0', 'u1'], 'last': 4, 'more': 2}`	`{'count': 16, 'faces': ['u4', 'u0', 'u1'], 'last': 19, 'more': 2}`	Failed
no replies	`{'count': 0, 'faces': [], 'last': None, 'more': 0}`	`{'count': 0, 'faces': [], 'last': None, 'more': 0}`	Passed

SHA-256 / 66f2c94707badd5c16e7bf33d10c9bd76d16e3037cdd82263420d27a737b3602

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

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.

Observations recorded using Python 3.12.14 at 2026-09-29T14:49:14.669873+00:00.

Case digest / 2aafb481bac2757b30da46e113e06e02004f6a15247bae8316203ada963c01f4