FA-26971 / HTTP ranges / Open access
Partial cache admission publishes complete requested fragments atomically: commit removes old-generation cells outside the new sparse object · case 01
Partial cache admission publishes complete requested fragments atomically: commit removes old-generation cells outside the new sparse object.
ROOT CAUSE
The partial-admission-transaction-generation-replacement decision uses visible=dict(x[0]) pending=None reads=[] for event in x[1]: op=event[0] if op=='begin': if pending is not None: continue pending=[event[1],set(event[2]),{}] elif op=='put': if pending is None or event[1]!=pending[0]: continue at,char=event[2:] if at not in pending[1]: continue if at in pending[2] and pending[2][at]!=char: pending=None continue pending[2][at]=char elif op=='commit': if pending is None or event[1]!=pending[0]: continue if set(pending[2])!=pending[1]: continue visible.update(pending[2]) pending=None elif op=='abort': if pending is not None and event[1]==pending[0]: pending=None elif op=='read': reads.append(sorted(visible.items())) return [reads,sorted(visible.items()),pending[0] if pending is not None else None].
VERIFIED REPAIR
Apply the bounded decision exactly: visible=dict(x[0]) pending=None reads=[] for event in x[1]: op=event[0] if op=='begin': if pending is not None: continue pending=[event[1],set(event[2]),{}] elif op=='put': if pending is None or event[1]!=pending[0]: continue at,char=event[2:] if at not in pending[1]: continue if at in pending[2] and pending[2][at]!=char: pending=None continue pending[2][at]=char elif op=='commit': if pending is None or event[1]!=pending[0]: continue if set(pending[2])!=pending[1]: continue visible=dict(pending[2]) pending=None elif op=='abort': if pending is not None and event[1]==pending[0]: pending=None elif op=='read': reads.append(sorted(visible.items())) return [reads,sorted(visible.items()),pending[0] if pending is not None else None]
Unsuccessful approach: The partial repair uses visible=dict(x[0]) pending=None reads=[] for event in x[1]: op=event[0] if op=='begin': if pending is not None: continue pending=[event[1],set(event[2]),{}] elif op=='put': if pending is None or event[1]!=pending[0]: continue at,char=event[2:] if at not in pending[1]: continue if at in pending[2] and pending[2][at]!=char: pending=None continue pending[2][at]=char elif op=='commit': if pending is None or event[1]!=pending[0]: continue if set(pending[2])!=pending[1]: continue visible.update(pending[2]) visible={k:v for k,v in visible.items() if k<=max(visible,default=0)} pending=None elif op=='abort': if pending is not None and event[1]==pending[0]: pending=None elif op=='read': reads.append(sorted(visible.items())) return [reads,sorted(visible.items()),pending[0] if pending is not None else None], which still violates the stated contract.
Case contract
x is [old-visible-cells,events]. Events begin(id,expected-offsets), put(id,offset,char), commit(id), abort(id), read. One transaction at a time; unknown or mismatching ids ignored. A conflicting duplicate byte invalidates the active transaction. Commit succeeds only when every expected cell is present and replaces the old generation. Readers see committed cells sorted by offset. Return [read-snapshots,final-cells,pending-id].
Why this case matters
Range responses combine representation identity, conditional requests, framing, and partial-object state.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
visible=dict(x[0])
pending=None
reads=[]
for event in x[1]:
op=event[0]
if op=='begin':
if pending is not None: continue
pending=[event[1],set(event[2]),{}]
elif op=='put':
if pending is None or event[1]!=pending[0]: continue
at,char=event[2:]
if at not in pending[1]: continue
if at in pending[2] and pending[2][at]!=char:
pending=None
continue
pending[2][at]=char
elif op=='commit':
if pending is None or event[1]!=pending[0]: continue
if set(pending[2])!=pending[1]: continue
visible.update(pending[2])
pending=None
elif op=='abort':
if pending is not None and event[1]==pending[0]: pending=None
elif op=='read':
reads.append(sorted(visible.items()))
return [reads,sorted(visible.items()),pending[0] if pending is not None else None]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('generation-replacement fixture 0', json.loads(json.dumps(solve([[[0,'o'],[9,'z']],[['begin','a',[0,1]],['put','a',1,'b'],['read'],['put','a',0,'a'],['commit','a'],['read']]]))), json.loads(json.dumps([[[[0,'o'],[9,'z']],[[0,'a'],[1,'b']]],[[0,'a'],[1,'b']],None])))
check('generation-replacement fixture 1', json.loads(json.dumps(solve([[],[['begin','a',[0,1]],['put','a',0,'a'],['commit','a'],['read']]]))), json.loads(json.dumps([[[]],[],'a'])))
check('generation-replacement fixture 2', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','wrong',0,'x'],['put','a',1,'y'],['commit','a'],['read']]]))), json.loads(json.dumps([[[]],[],'a'])))
check('generation-replacement fixture 3', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','a',0,'a'],['put','a',1,'b'],['commit','a']]]))), json.loads(json.dumps([[],[[0,'a']],None])))
check('generation-replacement fixture 4', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','a',0,'a'],['put','a',0,'b'],['commit','a']]]))), json.loads(json.dumps([[],[],None])))
check('generation-replacement fixture 5', json.loads(json.dumps(solve([[],[['begin','a',[0]],['begin','b',[]],['abort','b'],['put','a',0,'a'],['commit','a']]]))), json.loads(json.dumps([[],[[0,'a']],None])))
check('generation-replacement fixture 6', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','a',0,'a'],['put','a',0,'a'],['commit','wrong'],['read'],['commit','a']]]))), json.loads(json.dumps([[[]],[[0,'a']],None])))
check('generation-replacement fixture 7', json.loads(json.dumps(solve([[],[['begin','a',[]],['commit','a'],['begin','b',[N]],['put','b',N,'p'],['commit','b']]]))), json.loads(json.dumps([[],[[N,'p']],None])))
check('generation-replacement fixture 8', json.loads(json.dumps(solve([[[0,'o']],[['begin','a',[0]],['put','a',0,'a'],['abort','a'],['read']]]))), json.loads(json.dumps([[[[0,'o']]],[[0,'o']],None])))
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 |
|---|---|---|---|
| generation-replacement fixture 0 | [[[[0, 'o'], [9, 'z']], [[0, 'a'], [1, 'b'], [9, 'z']]], [[0, 'a'], [1, 'b'], [9, 'z']], None] | [[[[0, 'o'], [9, 'z']], [[0, 'a'], [1, 'b']]], [[0, 'a'], [1, 'b']], None] | Failed |
| generation-replacement fixture 1 | [[[]], [], 'a'] | [[[]], [], 'a'] | Passed |
| generation-replacement fixture 2 | [[[]], [], 'a'] | [[[]], [], 'a'] | Passed |
| generation-replacement fixture 3 | [[], [[0, 'a']], None] | [[], [[0, 'a']], None] | Passed |
| generation-replacement fixture 4 | [[], [], None] | [[], [], None] | Passed |
| generation-replacement fixture 5 | [[], [[0, 'a']], None] | [[], [[0, 'a']], None] | Passed |
| generation-replacement fixture 6 | [[[]], [[0, 'a']], None] | [[[]], [[0, 'a']], None] | Passed |
| generation-replacement fixture 7 | [[], [[1, 'p']], None] | [[], [[1, 'p']], None] | Passed |
| generation-replacement fixture 8 | [[[[0, 'o']]], [[0, 'o']], None] | [[[[0, 'o']]], [[0, 'o']], None] | Passed |
SHA-256 / 19322094e83109340fea8e9f3189f3cbf97c8902e82490af75f3968843d1acb2
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
visible=dict(x[0])
pending=None
reads=[]
for event in x[1]:
op=event[0]
if op=='begin':
if pending is not None: continue
pending=[event[1],set(event[2]),{}]
elif op=='put':
if pending is None or event[1]!=pending[0]: continue
at,char=event[2:]
if at not in pending[1]: continue
if at in pending[2] and pending[2][at]!=char:
pending=None
continue
pending[2][at]=char
elif op=='commit':
if pending is None or event[1]!=pending[0]: continue
if set(pending[2])!=pending[1]: continue
visible.update(pending[2])
visible={k:v for k,v in visible.items() if k<=max(visible,default=0)}
pending=None
elif op=='abort':
if pending is not None and event[1]==pending[0]: pending=None
elif op=='read':
reads.append(sorted(visible.items()))
return [reads,sorted(visible.items()),pending[0] if pending is not None else None]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('generation-replacement fixture 0', json.loads(json.dumps(solve([[[0,'o'],[9,'z']],[['begin','a',[0,1]],['put','a',1,'b'],['read'],['put','a',0,'a'],['commit','a'],['read']]]))), json.loads(json.dumps([[[[0,'o'],[9,'z']],[[0,'a'],[1,'b']]],[[0,'a'],[1,'b']],None])))
check('generation-replacement fixture 1', json.loads(json.dumps(solve([[],[['begin','a',[0,1]],['put','a',0,'a'],['commit','a'],['read']]]))), json.loads(json.dumps([[[]],[],'a'])))
check('generation-replacement fixture 2', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','wrong',0,'x'],['put','a',1,'y'],['commit','a'],['read']]]))), json.loads(json.dumps([[[]],[],'a'])))
check('generation-replacement fixture 3', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','a',0,'a'],['put','a',1,'b'],['commit','a']]]))), json.loads(json.dumps([[],[[0,'a']],None])))
check('generation-replacement fixture 4', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','a',0,'a'],['put','a',0,'b'],['commit','a']]]))), json.loads(json.dumps([[],[],None])))
check('generation-replacement fixture 5', json.loads(json.dumps(solve([[],[['begin','a',[0]],['begin','b',[]],['abort','b'],['put','a',0,'a'],['commit','a']]]))), json.loads(json.dumps([[],[[0,'a']],None])))
check('generation-replacement fixture 6', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','a',0,'a'],['put','a',0,'a'],['commit','wrong'],['read'],['commit','a']]]))), json.loads(json.dumps([[[]],[[0,'a']],None])))
check('generation-replacement fixture 7', json.loads(json.dumps(solve([[],[['begin','a',[]],['commit','a'],['begin','b',[N]],['put','b',N,'p'],['commit','b']]]))), json.loads(json.dumps([[],[[N,'p']],None])))
check('generation-replacement fixture 8', json.loads(json.dumps(solve([[[0,'o']],[['begin','a',[0]],['put','a',0,'a'],['abort','a'],['read']]]))), json.loads(json.dumps([[[[0,'o']]],[[0,'o']],None])))
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 |
|---|---|---|---|
| generation-replacement fixture 0 | [[[[0, 'o'], [9, 'z']], [[0, 'a'], [1, 'b'], [9, 'z']]], [[0, 'a'], [1, 'b'], [9, 'z']], None] | [[[[0, 'o'], [9, 'z']], [[0, 'a'], [1, 'b']]], [[0, 'a'], [1, 'b']], None] | Failed |
| generation-replacement fixture 1 | [[[]], [], 'a'] | [[[]], [], 'a'] | Passed |
| generation-replacement fixture 2 | [[[]], [], 'a'] | [[[]], [], 'a'] | Passed |
| generation-replacement fixture 3 | [[], [[0, 'a']], None] | [[], [[0, 'a']], None] | Passed |
| generation-replacement fixture 4 | [[], [], None] | [[], [], None] | Passed |
| generation-replacement fixture 5 | [[], [[0, 'a']], None] | [[], [[0, 'a']], None] | Passed |
| generation-replacement fixture 6 | [[[]], [[0, 'a']], None] | [[[]], [[0, 'a']], None] | Passed |
| generation-replacement fixture 7 | [[], [[1, 'p']], None] | [[], [[1, 'p']], None] | Passed |
| generation-replacement fixture 8 | [[[[0, 'o']]], [[0, 'o']], None] | [[[[0, 'o']]], [[0, 'o']], None] | Passed |
SHA-256 / f7b0f356e756e8a0c1b3cc9ddcb15ab8b688605b076a3ee41229d45ace556743
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
visible=dict(x[0])
pending=None
reads=[]
for event in x[1]:
op=event[0]
if op=='begin':
if pending is not None: continue
pending=[event[1],set(event[2]),{}]
elif op=='put':
if pending is None or event[1]!=pending[0]: continue
at,char=event[2:]
if at not in pending[1]: continue
if at in pending[2] and pending[2][at]!=char:
pending=None
continue
pending[2][at]=char
elif op=='commit':
if pending is None or event[1]!=pending[0]: continue
if set(pending[2])!=pending[1]: continue
visible=dict(pending[2])
pending=None
elif op=='abort':
if pending is not None and event[1]==pending[0]: pending=None
elif op=='read':
reads.append(sorted(visible.items()))
return [reads,sorted(visible.items()),pending[0] if pending is not None else None]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('generation-replacement fixture 0', json.loads(json.dumps(solve([[[0,'o'],[9,'z']],[['begin','a',[0,1]],['put','a',1,'b'],['read'],['put','a',0,'a'],['commit','a'],['read']]]))), json.loads(json.dumps([[[[0,'o'],[9,'z']],[[0,'a'],[1,'b']]],[[0,'a'],[1,'b']],None])))
check('generation-replacement fixture 1', json.loads(json.dumps(solve([[],[['begin','a',[0,1]],['put','a',0,'a'],['commit','a'],['read']]]))), json.loads(json.dumps([[[]],[],'a'])))
check('generation-replacement fixture 2', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','wrong',0,'x'],['put','a',1,'y'],['commit','a'],['read']]]))), json.loads(json.dumps([[[]],[],'a'])))
check('generation-replacement fixture 3', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','a',0,'a'],['put','a',1,'b'],['commit','a']]]))), json.loads(json.dumps([[],[[0,'a']],None])))
check('generation-replacement fixture 4', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','a',0,'a'],['put','a',0,'b'],['commit','a']]]))), json.loads(json.dumps([[],[],None])))
check('generation-replacement fixture 5', json.loads(json.dumps(solve([[],[['begin','a',[0]],['begin','b',[]],['abort','b'],['put','a',0,'a'],['commit','a']]]))), json.loads(json.dumps([[],[[0,'a']],None])))
check('generation-replacement fixture 6', json.loads(json.dumps(solve([[],[['begin','a',[0]],['put','a',0,'a'],['put','a',0,'a'],['commit','wrong'],['read'],['commit','a']]]))), json.loads(json.dumps([[[]],[[0,'a']],None])))
check('generation-replacement fixture 7', json.loads(json.dumps(solve([[],[['begin','a',[]],['commit','a'],['begin','b',[N]],['put','b',N,'p'],['commit','b']]]))), json.loads(json.dumps([[],[[N,'p']],None])))
check('generation-replacement fixture 8', json.loads(json.dumps(solve([[[0,'o']],[['begin','a',[0]],['put','a',0,'a'],['abort','a'],['read']]]))), json.loads(json.dumps([[[[0,'o']]],[[0,'o']],None])))
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 |
|---|---|---|---|
| generation-replacement fixture 0 | [[[[0, 'o'], [9, 'z']], [[0, 'a'], [1, 'b']]], [[0, 'a'], [1, 'b']], None] | [[[[0, 'o'], [9, 'z']], [[0, 'a'], [1, 'b']]], [[0, 'a'], [1, 'b']], None] | Passed |
| generation-replacement fixture 1 | [[[]], [], 'a'] | [[[]], [], 'a'] | Passed |
| generation-replacement fixture 2 | [[[]], [], 'a'] | [[[]], [], 'a'] | Passed |
| generation-replacement fixture 3 | [[], [[0, 'a']], None] | [[], [[0, 'a']], None] | Passed |
| generation-replacement fixture 4 | [[], [], None] | [[], [], None] | Passed |
| generation-replacement fixture 5 | [[], [[0, 'a']], None] | [[], [[0, 'a']], None] | Passed |
| generation-replacement fixture 6 | [[[]], [[0, 'a']], None] | [[[]], [[0, 'a']], None] | Passed |
| generation-replacement fixture 7 | [[], [[1, 'p']], None] | [[], [[1, 'p']], None] | Passed |
| generation-replacement fixture 8 | [[[[0, 'o']]], [[0, 'o']], None] | [[[[0, 'o']]], [[0, 'o']], None] | Passed |
SHA-256 / 765cad2536d5f14986957dc06b63afc6d05c8623b6f7afcafd1ff547f1471364
Verification & scope
Deterministic simplified range service, with stipulated local policies and already parsed trusted inputs; not a complete HTTP 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 2026-09-29T14:41:20.651992+00:00.
Case digest / 2b9677502ba33b0032a5154fabb98da9dbd97f3ca0a6718d0a9460cbdbe77717