FA-911 / Queues / Open access

Purge messages through a selected boundary: Purge crosses into another tenant queue · case 01

The queue purge operation is admitted even though purge crosses into another tenant queue.

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

ROOT CAUSE

The admission path omits the namespace match invariant while validating the other operation preconditions.

THE FAILURE

The admission path omits the namespace match invariant while validating the other operation preconditions.

Unsuccessful approach: Adding the namespace match check repairs the reported defect, but replacing the adjacent queue incarnation check loses that independent invariant.

Case contract

Return a Boolean admission decision for purge messages through a selected boundary. The record r must satisfy all of: r['boundary_fixed'][0] <= r['boundary_fixed'][1]; r['reserved_protected'] is False; r['namespace_match'][0] == r['namespace_match'][1]; r['queue_incarnation'][0] == r['queue_incarnation'][1]; r['retention_hold'] is False. Extra tracing fields are ignored; validation does not mutate the record.

Why this case matters

A deterministic local contract for queues. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(r):
    return (r['boundary_fixed'][0] <= r['boundary_fixed'][1]) and (r['reserved_protected'] is False) and (r['queue_incarnation'][0] == r['queue_incarnation'][1]) and (r['retention_hold'] is False)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
r = {'boundary_fixed': [100, 100], 'reserved_protected': False, 'namespace_match': ['t1', 't1'], 'queue_incarnation': ['g2', 'g2'], 'retention_hold': False}
check('valid operation', solve(r), True)
check('A moving purge boundary consumes messages published after purge began', solve(dict(r, **{'boundary_fixed': [101, 100]})), False)
check('Purge deletes an actively reserved delivery', solve(dict(r, **{'reserved_protected': True})), False)
check('Purge crosses into another tenant queue', solve(dict(r, **{'namespace_match': ['t2', 't1']})), False)
check('A delayed purge targets a recreated queue with the same name', solve(dict(r, **{'queue_incarnation': ['g1', 'g2']})), False)
check('Purge ignores an explicit retention hold', solve(dict(r, **{'retention_hold': True})), False)
check('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)
check('repeat validation is pure', solve(r), True)
invalid = {'boundary_fixed': [101, 100], 'reserved_protected': True, 'namespace_match': ['t2', 't1'], 'queue_incarnation': ['g1', 'g2'], 'retention_hold': True}
keys = list(invalid)
pair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}
check('two independent violations in variant', solve(dict(r, **pair)), False)
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
valid operation	`True`	`True`	Passed
A moving purge boundary consumes messages published after purge began	`False`	`False`	Passed
Purge deletes an actively reserved delivery	`False`	`False`	Passed
Purge crosses into another tenant queue	`True`	`False`	Failed
A delayed purge targets a recreated queue with the same name	`False`	`False`	Passed
Purge ignores an explicit retention hold	`False`	`False`	Passed
unrelated tracing metadata	`True`	`True`	Passed
repeat validation is pure	`True`	`True`	Passed
two independent violations in variant	`False`	`False`	Passed

SHA-256 / 5dff197aab188d35d93dbae7b355517166b815538876b1982957ea1568395ae0

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(r):
    return (r['boundary_fixed'][0] <= r['boundary_fixed'][1]) and (r['reserved_protected'] is False) and (r['namespace_match'][0] == r['namespace_match'][1]) and (r['retention_hold'] is False)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
r = {'boundary_fixed': [100, 100], 'reserved_protected': False, 'namespace_match': ['t1', 't1'], 'queue_incarnation': ['g2', 'g2'], 'retention_hold': False}
check('valid operation', solve(r), True)
check('A moving purge boundary consumes messages published after purge began', solve(dict(r, **{'boundary_fixed': [101, 100]})), False)
check('Purge deletes an actively reserved delivery', solve(dict(r, **{'reserved_protected': True})), False)
check('Purge crosses into another tenant queue', solve(dict(r, **{'namespace_match': ['t2', 't1']})), False)
check('A delayed purge targets a recreated queue with the same name', solve(dict(r, **{'queue_incarnation': ['g1', 'g2']})), False)
check('Purge ignores an explicit retention hold', solve(dict(r, **{'retention_hold': True})), False)
check('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)
check('repeat validation is pure', solve(r), True)
invalid = {'boundary_fixed': [101, 100], 'reserved_protected': True, 'namespace_match': ['t2', 't1'], 'queue_incarnation': ['g1', 'g2'], 'retention_hold': True}
keys = list(invalid)
pair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}
check('two independent violations in variant', solve(dict(r, **pair)), False)
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
valid operation	`True`	`True`	Passed
A moving purge boundary consumes messages published after purge began	`False`	`False`	Passed
Purge deletes an actively reserved delivery	`False`	`False`	Passed
Purge crosses into another tenant queue	`False`	`False`	Passed
A delayed purge targets a recreated queue with the same name	`True`	`False`	Failed
Purge ignores an explicit retention hold	`False`	`False`	Passed
unrelated tracing metadata	`True`	`True`	Passed
repeat validation is pure	`True`	`True`	Passed
two independent violations in variant	`False`	`False`	Passed

SHA-256 / 6bf1096446d470dda7e0b5ad12cb1185134835ee0d719413acf4d9efc1f8f757

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.

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

Verification & scope

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 2026-09-29T14:36:57.204496+00:00.

Case digest / 8f94bc400310646dfa5ee6d365c5d44dcceb8a065343bdc9e32e4aeb71ee2c76