FAILURE MAP
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FA-75951 / Chat ordering and read receipts / Open access

Fold out-of-order delivery events into a recipient status: retry source · case 01

A retry signal resets a delivered message back to queued.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The retry source decision evaluates `'queued'` where the contract requires `'queued' if status == 'failed' else status`.

THE FAILURE

The retry source decision evaluates `'queued'` where the contract requires `'queued' if status == 'failed' else status`.

Unsuccessful approach: Protecting only read messages still lets a retry regress a delivered one. The attempted `'queued' if status != 'read' else status` still disagrees with a fixture.

Case contract

events are [seq, kind] with kind in queued, sent, delivered, read, failed, retry, processed in (seq, kind) order. Ranks queued<sent<delivered<read and status never regresses. failed only applies while queued or sent; retry moves failed back to queued; after a failure only delivered or read evidence (not a stale sent) replaces it. Result {status, history} where history lists every status change starting at queued.

Why this case matters

Per-recipient ticks are assembled from events that arrive out of order across transports.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(events):
    rank = {'queued': 0, 'sent': 1, 'delivered': 2, 'read': 3}
    status = 'queued'
    history = ['queued']
    for _, kind in sorted(events):
        if kind == 'failed':
            nxt = 'failed' if status in ('queued', 'sent') else status
        elif kind == 'retry':
            nxt = 'queued'
        elif status == 'failed':
            nxt = kind if rank[kind] >= rank['delivered'] else status
        else:
            nxt = kind if rank[kind] > rank[status] else status
        if nxt != status:
            status = nxt
            history.append(status)
    return {'status': status, 'history': history}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('arrival order differs', ([[4, 'read'], [2, 'sent'], [3, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[1, 'failed'], [2, 'retry'], [3, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [3, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [4, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [5, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})], 2: [('arrival order differs', ([[5, 'read'], [3, 'sent'], [4, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[2, 'failed'], [3, 'retry'], [4, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [4, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [5, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [6, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})], 3: [('arrival order differs', ([[6, 'read'], [4, 'sent'], [5, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[3, 'failed'], [4, 'retry'], [5, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [5, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [6, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [7, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})], 4: [('arrival order differs', ([[7, 'read'], [5, 'sent'], [6, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[4, 'failed'], [5, 'retry'], [6, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [6, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [7, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [8, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})], 5: [('arrival order differs', ([[8, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[5, 'failed'], [6, 'retry'], [7, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [7, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [8, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [9, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})]}
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 fixtureActualExpectedOutcome
arrival order differs{'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}{'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}Passed
failure after delivery{'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}{'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}Passed
failure while queued{'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}{'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}Passed
retry after read{'history': ['queued', 'read', 'queued'], 'status': 'queued'}{'history': ['queued', 'read'], 'status': 'read'}Failed
retry after delivery{'history': ['queued', 'delivered', 'queued'], 'status': 'queued'}{'history': ['queued', 'delivered'], 'status': 'delivered'}Failed
late delivery after failure{'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}{'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}Passed
stale sent after failure{'history': ['queued', 'sent', 'failed'], 'status': 'failed'}{'history': ['queued', 'sent', 'failed'], 'status': 'failed'}Passed
late sent after read{'history': ['queued', 'read'], 'status': 'read'}{'history': ['queued', 'read'], 'status': 'read'}Passed
failed then retried delivery{'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'}{'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'}Passed

SHA-256 / d5fd57fef655f1a33320f351d236606b06eaf64eef89b03d4c3f579ee2876fc3

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(events):
    rank = {'queued': 0, 'sent': 1, 'delivered': 2, 'read': 3}
    status = 'queued'
    history = ['queued']
    for _, kind in sorted(events):
        if kind == 'failed':
            nxt = 'failed' if status in ('queued', 'sent') else status
        elif kind == 'retry':
            nxt = 'queued' if status != 'read' else status
        elif status == 'failed':
            nxt = kind if rank[kind] >= rank['delivered'] else status
        else:
            nxt = kind if rank[kind] > rank[status] else status
        if nxt != status:
            status = nxt
            history.append(status)
    return {'status': status, 'history': history}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('arrival order differs', ([[4, 'read'], [2, 'sent'], [3, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[1, 'failed'], [2, 'retry'], [3, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [3, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [4, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [5, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})], 2: [('arrival order differs', ([[5, 'read'], [3, 'sent'], [4, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[2, 'failed'], [3, 'retry'], [4, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [4, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [5, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [6, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})], 3: [('arrival order differs', ([[6, 'read'], [4, 'sent'], [5, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[3, 'failed'], [4, 'retry'], [5, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [5, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [6, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [7, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})], 4: [('arrival order differs', ([[7, 'read'], [5, 'sent'], [6, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[4, 'failed'], [5, 'retry'], [6, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [6, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [7, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [8, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})], 5: [('arrival order differs', ([[8, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}), ('failure after delivery', ([[1, 'sent'], [2, 'delivered'], [3, 'failed']],), {'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}), ('failure while queued', ([[5, 'failed'], [6, 'retry'], [7, 'sent']],), {'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}), ('retry after read', ([[1, 'read'], [2, 'retry']],), {'history': ['queued', 'read'], 'status': 'read'}), ('retry after delivery', ([[1, 'delivered'], [7, 'retry']],), {'history': ['queued', 'delivered'], 'status': 'delivered'}), ('late delivery after failure', ([[1, 'sent'], [2, 'failed'], [3, 'delivered']],), {'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}), ('stale sent after failure', ([[1, 'sent'], [2, 'failed'], [8, 'sent']],), {'history': ['queued', 'sent', 'failed'], 'status': 'failed'}), ('late sent after read', ([[5, 'read'], [6, 'sent'], [7, 'delivered']],), {'history': ['queued', 'read'], 'status': 'read'}), ('failed then retried delivery', ([[2, 'failed'], [3, 'retry'], [4, 'delivered'], [9, 'failed']],), {'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'})]}
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 fixtureActualExpectedOutcome
arrival order differs{'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}{'history': ['queued', 'sent', 'delivered', 'read'], 'status': 'read'}Passed
failure after delivery{'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}{'history': ['queued', 'sent', 'delivered'], 'status': 'delivered'}Passed
failure while queued{'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}{'history': ['queued', 'failed', 'queued', 'sent'], 'status': 'sent'}Passed
retry after read{'history': ['queued', 'read'], 'status': 'read'}{'history': ['queued', 'read'], 'status': 'read'}Passed
retry after delivery{'history': ['queued', 'delivered', 'queued'], 'status': 'queued'}{'history': ['queued', 'delivered'], 'status': 'delivered'}Failed
late delivery after failure{'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}{'history': ['queued', 'sent', 'failed', 'delivered'], 'status': 'delivered'}Passed
stale sent after failure{'history': ['queued', 'sent', 'failed'], 'status': 'failed'}{'history': ['queued', 'sent', 'failed'], 'status': 'failed'}Passed
late sent after read{'history': ['queued', 'read'], 'status': 'read'}{'history': ['queued', 'read'], 'status': 'read'}Passed
failed then retried delivery{'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'}{'history': ['queued', 'failed', 'queued', 'delivered'], 'status': 'delivered'}Passed

SHA-256 / 240c11527a3c111f793ee09925dbfe3289303a8ee437ab6604151544e827797c

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 9 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 2026-09-29T14:49:11.919161+00:00.

Case digest / ade0d212b7d20daed217c32de3822a4fe763974def2252a59d31fdd1c9f7c6e3