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FA-27806 / HTTP ranges / Open access

An object store maps upload part numbers and byte ranges onto stored parts: part numbers are one-based and positive · case 01

An object store maps upload part numbers and byte ranges onto stored parts: part numbers are one-based and positive.

Verified by executionVariant 1 · 14 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The part-number-range-map-part-number-domain decision uses sizes=x['parts'] total=sum(sizes) starts=[] acc=0 for s in sizes: starts.append(acc) acc+=s q=x['query'] if q[0]=='part': n=q[1] if not 0<=n<=len(sizes) or sizes[n-1]==0: return [416,'bytes */%d'%total] a=starts[n-1] return [206,'bytes %d-%d/%d'%(a,a+sizes[n-1]-1,total)] a,b=q[1],q[2] if not 0<=a<=b<total: return [416,'bytes */%d'%total] out=[] for i,s in enumerate(sizes): lo=max(a,starts[i]) hi=min(b,starts[i]+s-1) if lo<=hi: out.append([i+1,lo-starts[i],hi-lo+1]) return [206,out].

THE FAILURE

The part-number-range-map-part-number-domain decision uses sizes=x['parts'] total=sum(sizes) starts=[] acc=0 for s in sizes: starts.append(acc) acc+=s q=x['query'] if q[0]=='part': n=q[1] if not 0<=n<=len(sizes) or sizes[n-1]==0: return [416,'bytes */%d'%total] a=starts[n-1] return [206,'bytes %d-%d/%d'%(a,a+sizes[n-1]-1,total)] a,b=q[1],q[2] if not 0<=a<=b<total: return [416,'bytes */%d'%total] out=[] for i,s in enumerate(sizes): lo=max(a,starts[i]) hi=min(b,starts[i]+s-1) if lo<=hi: out.append([i+1,lo-starts[i],hi-lo+1]) return [206,out].

Unsuccessful approach: The partial repair uses sizes=x['parts'] total=sum(sizes) starts=[] acc=0 for s in sizes: starts.append(acc) acc+=s q=x['query'] if q[0]=='part': n=q[1] if not n<=len(sizes) or sizes[n-1]==0: return [416,'bytes */%d'%total] a=starts[n-1] return [206,'bytes %d-%d/%d'%(a,a+sizes[n-1]-1,total)] a,b=q[1],q[2] if not 0<=a<=b<total: return [416,'bytes */%d'%total] out=[] for i,s in enumerate(sizes): lo=max(a,starts[i]) hi=min(b,starts[i]+s-1) if lo<=hi: out.append([i+1,lo-starts[i],hi-lo+1]) return [206,out], which still violates the stated contract.

Case contract

x has stored part sizes in order and a query. ["part",n] (1-based) returns [206,bytes a-b/total] for that part, or [416,bytes */total] when n is outside 1..count or the part is empty. ["range",a,b] with inclusive bounds returns [416,bytes */total] unless 0<=a<=b<total; otherwise [206,rows] where each intersecting nonempty part yields [part-number,offset-within-part,count] in part order.

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):
    sizes=x['parts']
    total=sum(sizes)
    starts=[]
    acc=0
    for s in sizes:
        starts.append(acc)
        acc+=s
    q=x['query']
    if q[0]=='part':
        n=q[1]
        if not 0<=n<=len(sizes) or sizes[n-1]==0: return [416,'bytes */%d'%total]
        a=starts[n-1]
        return [206,'bytes %d-%d/%d'%(a,a+sizes[n-1]-1,total)]
    a,b=q[1],q[2]
    if not 0<=a<=b<total: return [416,'bytes */%d'%total]
    out=[]
    for i,s in enumerate(sizes):
        lo=max(a,starts[i])
        hi=min(b,starts[i]+s-1)
        if lo<=hi: out.append([i+1,lo-starts[i],hi-lo+1])
    return [206,out]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('part-number-domain fixture 0', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',2]}))), json.loads(json.dumps([206,'bytes 5-7/12'])))
check('part-number-domain fixture 1', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',3]}))), json.loads(json.dumps([206,'bytes 8-11/12'])))
check('part-number-domain fixture 2', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',0]}))), json.loads(json.dumps([416,'bytes */12'])))
check('part-number-domain fixture 3', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',-1]}))), json.loads(json.dumps([416,'bytes */12'])))
check('part-number-domain fixture 4', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',4]}))), json.loads(json.dumps([416,'bytes */12'])))
check('part-number-domain fixture 5', json.loads(json.dumps(solve({'parts':[5,0,4],'query':['part',2]}))), json.loads(json.dumps([416,'bytes */9'])))
check('part-number-domain fixture 6', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',3,9]}))), json.loads(json.dumps([206,[[1,3,2],[2,0,3],[3,0,2]]])))
check('part-number-domain fixture 7', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',4,5]}))), json.loads(json.dumps([206,[[1,4,1],[2,0,1]]])))
check('part-number-domain fixture 8', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',5,7]}))), json.loads(json.dumps([206,[[2,0,3]]])))
check('part-number-domain fixture 9', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',0,12]}))), json.loads(json.dumps([416,'bytes */12'])))
check('part-number-domain fixture 10', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',0,11]}))), json.loads(json.dumps([206,[[1,0,5],[2,0,3],[3,0,4]]])))
check('part-number-domain fixture 11', json.loads(json.dumps(solve({'parts':[5,0,4],'query':['range',4,5]}))), json.loads(json.dumps([206,[[1,4,1],[3,0,1]]])))
check('part-number-domain fixture 12', json.loads(json.dumps(solve({'parts':[],'query':['part',1]}))), json.loads(json.dumps([416,'bytes */0'])))
check('part-number-domain fixture 13', json.loads(json.dumps(solve({'parts':[N,N],'query':['part',2]}))), json.loads(json.dumps([206,"bytes %d-%d/%d"%(N,2*N-1,2*N)])))
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
part-number-domain fixture 0[206, 'bytes 5-7/12'][206, 'bytes 5-7/12']Passed
part-number-domain fixture 1[206, 'bytes 8-11/12'][206, 'bytes 8-11/12']Passed
part-number-domain fixture 2[206, 'bytes 8-11/12'][416, 'bytes */12']Failed
part-number-domain fixture 3[416, 'bytes */12'][416, 'bytes */12']Passed
part-number-domain fixture 4[416, 'bytes */12'][416, 'bytes */12']Passed
part-number-domain fixture 5[416, 'bytes */9'][416, 'bytes */9']Passed
part-number-domain fixture 6[206, [[1, 3, 2], [2, 0, 3], [3, 0, 2]]][206, [[1, 3, 2], [2, 0, 3], [3, 0, 2]]]Passed
part-number-domain fixture 7[206, [[1, 4, 1], [2, 0, 1]]][206, [[1, 4, 1], [2, 0, 1]]]Passed
part-number-domain fixture 8[206, [[2, 0, 3]]][206, [[2, 0, 3]]]Passed
part-number-domain fixture 9[416, 'bytes */12'][416, 'bytes */12']Passed
part-number-domain fixture 10[206, [[1, 0, 5], [2, 0, 3], [3, 0, 4]]][206, [[1, 0, 5], [2, 0, 3], [3, 0, 4]]]Passed
part-number-domain fixture 11[206, [[1, 4, 1], [3, 0, 1]]][206, [[1, 4, 1], [3, 0, 1]]]Passed
part-number-domain fixture 12[416, 'bytes */0'][416, 'bytes */0']Passed
part-number-domain fixture 13[206, 'bytes 1-1/2'][206, 'bytes 1-1/2']Passed

SHA-256 / 5af7859aaed053ebeb3acb67e1fea821f9e2949e0c2b1877e7d5eeb0e46d980c

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    sizes=x['parts']
    total=sum(sizes)
    starts=[]
    acc=0
    for s in sizes:
        starts.append(acc)
        acc+=s
    q=x['query']
    if q[0]=='part':
        n=q[1]
        if not n<=len(sizes) or sizes[n-1]==0: return [416,'bytes */%d'%total]
        a=starts[n-1]
        return [206,'bytes %d-%d/%d'%(a,a+sizes[n-1]-1,total)]
    a,b=q[1],q[2]
    if not 0<=a<=b<total: return [416,'bytes */%d'%total]
    out=[]
    for i,s in enumerate(sizes):
        lo=max(a,starts[i])
        hi=min(b,starts[i]+s-1)
        if lo<=hi: out.append([i+1,lo-starts[i],hi-lo+1])
    return [206,out]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('part-number-domain fixture 0', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',2]}))), json.loads(json.dumps([206,'bytes 5-7/12'])))
check('part-number-domain fixture 1', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',3]}))), json.loads(json.dumps([206,'bytes 8-11/12'])))
check('part-number-domain fixture 2', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',0]}))), json.loads(json.dumps([416,'bytes */12'])))
check('part-number-domain fixture 3', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',-1]}))), json.loads(json.dumps([416,'bytes */12'])))
check('part-number-domain fixture 4', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['part',4]}))), json.loads(json.dumps([416,'bytes */12'])))
check('part-number-domain fixture 5', json.loads(json.dumps(solve({'parts':[5,0,4],'query':['part',2]}))), json.loads(json.dumps([416,'bytes */9'])))
check('part-number-domain fixture 6', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',3,9]}))), json.loads(json.dumps([206,[[1,3,2],[2,0,3],[3,0,2]]])))
check('part-number-domain fixture 7', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',4,5]}))), json.loads(json.dumps([206,[[1,4,1],[2,0,1]]])))
check('part-number-domain fixture 8', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',5,7]}))), json.loads(json.dumps([206,[[2,0,3]]])))
check('part-number-domain fixture 9', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',0,12]}))), json.loads(json.dumps([416,'bytes */12'])))
check('part-number-domain fixture 10', json.loads(json.dumps(solve({'parts':[5,3,4],'query':['range',0,11]}))), json.loads(json.dumps([206,[[1,0,5],[2,0,3],[3,0,4]]])))
check('part-number-domain fixture 11', json.loads(json.dumps(solve({'parts':[5,0,4],'query':['range',4,5]}))), json.loads(json.dumps([206,[[1,4,1],[3,0,1]]])))
check('part-number-domain fixture 12', json.loads(json.dumps(solve({'parts':[],'query':['part',1]}))), json.loads(json.dumps([416,'bytes */0'])))
check('part-number-domain fixture 13', json.loads(json.dumps(solve({'parts':[N,N],'query':['part',2]}))), json.loads(json.dumps([206,"bytes %d-%d/%d"%(N,2*N-1,2*N)])))
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
part-number-domain fixture 0[206, 'bytes 5-7/12'][206, 'bytes 5-7/12']Passed
part-number-domain fixture 1[206, 'bytes 8-11/12'][206, 'bytes 8-11/12']Passed
part-number-domain fixture 2[206, 'bytes 8-11/12'][416, 'bytes */12']Failed
part-number-domain fixture 3[206, 'bytes 5-7/12'][416, 'bytes */12']Failed
part-number-domain fixture 4[416, 'bytes */12'][416, 'bytes */12']Passed
part-number-domain fixture 5[416, 'bytes */9'][416, 'bytes */9']Passed
part-number-domain fixture 6[206, [[1, 3, 2], [2, 0, 3], [3, 0, 2]]][206, [[1, 3, 2], [2, 0, 3], [3, 0, 2]]]Passed
part-number-domain fixture 7[206, [[1, 4, 1], [2, 0, 1]]][206, [[1, 4, 1], [2, 0, 1]]]Passed
part-number-domain fixture 8[206, [[2, 0, 3]]][206, [[2, 0, 3]]]Passed
part-number-domain fixture 9[416, 'bytes */12'][416, 'bytes */12']Passed
part-number-domain fixture 10[206, [[1, 0, 5], [2, 0, 3], [3, 0, 4]]][206, [[1, 0, 5], [2, 0, 3], [3, 0, 4]]]Passed
part-number-domain fixture 11[206, [[1, 4, 1], [3, 0, 1]]][206, [[1, 4, 1], [3, 0, 1]]]Passed
part-number-domain fixture 12[416, 'bytes */0'][416, 'bytes */0']Passed
part-number-domain fixture 13[206, 'bytes 1-1/2'][206, 'bytes 1-1/2']Passed

SHA-256 / 23f8cb1620030d0d3d1d0f040c0cb3904b7ef9ca81738a0cacd413660446518f

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 14 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

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 2026-09-29T14:41:28.344007+00:00.

Case digest / c9d68d5212ab7e00a0cfbbdf9e30e1cabdc74ae2d62b88671b29d3c10b9235ab