FA-76311 / Chat ordering and read receipts / Open access

Count unread mentions and choose the jump target: seq order · case 01

The jump button targets a later mention because messages are scanned in arrival order.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The seq order decision evaluates `messages` where the contract requires `sorted(messages)`.

THE FAILURE

The seq order decision evaluates `messages` where the contract requires `sorted(messages)`.

Unsuccessful approach: Sorting by author still does not order mentions by sequence. The attempted `sorted(messages, key=lambda m: m[1])` still disagrees with a fixture.

Case contract

messages are [seq, author, mentions]. A message after the marker, not written by me, counts when it mentions me directly or mentions "@everyone" while the room does not suppress @everyone. Messages are evaluated in seq order and the jump target is the earliest counted seq. Result {count, jump}.

Why this case matters

Mention counters and "jump to mention" buttons need the same filter as the unread state.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(messages, me, marker, suppress_everyone):
    hits = []
    for seq, author, mentions in messages:
        if seq <= marker or author == me:
            continue
        if me in mentions or ('@everyone' in mentions and not suppress_everyone):
            hits.append(seq)
    return {'count': len(hits), 'jump': hits[0] if hits else None}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('suppressed everyone', ([[6, 'bo', ['@everyone']], [7, 'bo', ['me']], [8, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 7}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[10, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 2, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})], 2: [('suppressed everyone', ([[7, 'bo', ['@everyone']], [8, 'bo', ['me']], [9, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 8}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[11, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 3, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})], 3: [('suppressed everyone', ([[8, 'bo', ['@everyone']], [9, 'bo', ['me']], [10, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 9}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[12, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 4, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})], 4: [('suppressed everyone', ([[9, 'bo', ['@everyone']], [10, 'bo', ['me']], [11, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 10}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[13, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 5, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})], 5: [('suppressed everyone', ([[10, 'bo', ['@everyone']], [11, 'bo', ['me']], [12, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 11}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[14, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 6, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})]}
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
suppressed everyone	`{'count': 1, 'jump': 7}`	`{'count': 1, 'jump': 7}`	Passed
own everyone ping	`{'count': 0, 'jump': None}`	`{'count': 0, 'jump': None}`	Passed
out of order arrival	`{'count': 2, 'jump': 10}`	`{'count': 2, 'jump': 4}`	Failed
everyone allowed	`{'count': 1, 'jump': 2}`	`{'count': 1, 'jump': 2}`	Passed
already read	`{'count': 0, 'jump': None}`	`{'count': 0, 'jump': None}`	Passed
direct mention when suppressed	`{'count': 1, 'jump': 7}`	`{'count': 1, 'jump': 7}`	Passed

SHA-256 / 03afbd90182368d36bb7fbc31afdea944b3d9396d4364656dcb23c1a4c7ae399

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(messages, me, marker, suppress_everyone):
    hits = []
    for seq, author, mentions in sorted(messages, key=lambda m: m[1]):
        if seq <= marker or author == me:
            continue
        if me in mentions or ('@everyone' in mentions and not suppress_everyone):
            hits.append(seq)
    return {'count': len(hits), 'jump': hits[0] if hits else None}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('suppressed everyone', ([[6, 'bo', ['@everyone']], [7, 'bo', ['me']], [8, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 7}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[10, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 2, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})], 2: [('suppressed everyone', ([[7, 'bo', ['@everyone']], [8, 'bo', ['me']], [9, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 8}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[11, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 3, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})], 3: [('suppressed everyone', ([[8, 'bo', ['@everyone']], [9, 'bo', ['me']], [10, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 9}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[12, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 4, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})], 4: [('suppressed everyone', ([[9, 'bo', ['@everyone']], [10, 'bo', ['me']], [11, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 10}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[13, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 5, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})], 5: [('suppressed everyone', ([[10, 'bo', ['@everyone']], [11, 'bo', ['me']], [12, 'cy', []]], 'me', 0, True), {'count': 1, 'jump': 11}), ('own everyone ping', ([[3, 'me', ['@everyone']], [4, 'bo', []]], 'me', 1, False), {'count': 0, 'jump': None}), ('out of order arrival', ([[14, 'bo', ['me']], [4, 'cy', ['me']]], 'me', 2, False), {'count': 2, 'jump': 4}), ('everyone allowed', ([[2, 'bo', ['@everyone']]], 'me', 1, False), {'count': 1, 'jump': 2}), ('already read', ([[1, 'bo', ['me']]], 'me', 6, False), {'count': 0, 'jump': None}), ('direct mention when suppressed', ([[7, 'bo', ['me', '@everyone']]], 'me', 3, True), {'count': 1, 'jump': 7})]}
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
suppressed everyone	`{'count': 1, 'jump': 7}`	`{'count': 1, 'jump': 7}`	Passed
own everyone ping	`{'count': 0, 'jump': None}`	`{'count': 0, 'jump': None}`	Passed
out of order arrival	`{'count': 2, 'jump': 10}`	`{'count': 2, 'jump': 4}`	Failed
everyone allowed	`{'count': 1, 'jump': 2}`	`{'count': 1, 'jump': 2}`	Passed
already read	`{'count': 0, 'jump': None}`	`{'count': 0, 'jump': None}`	Passed
direct mention when suppressed	`{'count': 1, 'jump': 7}`	`{'count': 1, 'jump': 7}`	Passed

SHA-256 / 46db130f4afe0629505bb61c5fff009fb98c38b841e397883bce18d425941798

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 6 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.

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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 2026-09-29T14:49:15.211701+00:00.

Case digest / 7c9ae987a3cf817b410f1581f118d8e6405f4804bc1ffa1b66bd955cc98b7db3