FA-27361 / HTTP ranges / Open access

A persisted partial-response cache record keeps byte coverage and revision metadata intact: persisted generations retain their high byte · case 01

A persisted partial-response cache record keeps byte coverage and revision metadata intact: persisted generations retain their high byte.

Verified by executionVariant 1 · 10 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The partial-cache-record-revision-byte-order decision uses wire=x if len(wire)<10 or any(not 0<=b<=255 for b in wire): return None if wire[:2]!=[82,71]: return None if wire[2]!=1: return None if wire[3]!=0: return None if sum(wire[:-1])%256!=wire[-1]: return None generation=wire[5]256+wire[4] total=wire[6]256+wire[7] count=wire[8] pos=9 parts=[] owned=set() for _ in range(count): if pos+3>len(wire)-1: return None offset=wire[pos]*256+wire[pos+1] size=wire[pos+2] pos+=3 if pos+size>len(wire)-1 or offset+size>total: return None if any(i in owned for i in range(offset,offset+size)): return None owned.update(range(offset,offset+size)) parts.append([offset,''.join(chr(b) for b in wire[pos:pos+size])]) pos+=size if pos!=len(wire)-1: return None return [generation,total,parts].

THE FAILURE

The partial-cache-record-revision-byte-order decision uses wire=x if len(wire)<10 or any(not 0<=b<=255 for b in wire): return None if wire[:2]!=[82,71]: return None if wire[2]!=1: return None if wire[3]!=0: return None if sum(wire[:-1])%256!=wire[-1]: return None generation=wire[5]*256+wire[4] total=wire[6]*256+wire[7] count=wire[8] pos=9 parts=[] owned=set() for _ in range(count): if pos+3>len(wire)-1: return None offset=wire[pos]*256+wire[pos+1] size=wire[pos+2] pos+=3 if pos+size>len(wire)-1 or offset+size>total: return None if any(i in owned for i in range(offset,offset+size)): return None owned.update(range(offset,offset+size)) parts.append([offset,''.join(chr(b) for b in wire[pos:pos+size])]) pos+=size if pos!=len(wire)-1: return None return [generation,total,parts].

Unsuccessful approach: The partial repair uses wire=x if len(wire)<10 or any(not 0<=b<=255 for b in wire): return None if wire[:2]!=[82,71]: return None if wire[2]!=1: return None if wire[3]!=0: return None if sum(wire[:-1])%256!=wire[-1]: return None generation=wire[5] total=wire[6]*256+wire[7] count=wire[8] pos=9 parts=[] owned=set() for _ in range(count): if pos+3>len(wire)-1: return None offset=wire[pos]*256+wire[pos+1] size=wire[pos+2] pos+=3 if pos+size>len(wire)-1 or offset+size>total: return None if any(i in owned for i in range(offset,offset+size)): return None owned.update(range(offset,offset+size)) parts.append([offset,''.join(chr(b) for b in wire[pos:pos+size])]) pos+=size if pos!=len(wire)-1: return None return [generation,total,parts], which still violates the stated contract.

Case contract

Decode this stipulated local binary cache envelope: magic RG, version1, flags0, two-byte big-endian generation, two-byte big-endian complete length, one-byte fragment count, then fragments [two-byte big-endian offset,one-byte count,ASCII payload], followed by one checksum byte equal to sum of preceding bytes modulo256. Reject malformed envelopes, bytes outside0..255, trailing bytes, overlapping fragment ownership, or spans outside complete length. Return [generation,total,[[offset,payload],...]]. This is an invented bounded persistence format, not a public protocol.

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):
    wire=x
    if len(wire)<10 or any(not 0<=b<=255 for b in wire): return None
    if wire[:2]!=[82,71]: return None
    if wire[2]!=1: return None
    if wire[3]!=0: return None
    if sum(wire[:-1])%256!=wire[-1]: return None
    generation=wire[5]*256+wire[4]
    total=wire[6]*256+wire[7]
    count=wire[8]
    pos=9
    parts=[]
    owned=set()
    for _ in range(count):
        if pos+3>len(wire)-1: return None
        offset=wire[pos]*256+wire[pos+1]
        size=wire[pos+2]
        pos+=3
        if pos+size>len(wire)-1 or offset+size>total: return None
        if any(i in owned for i in range(offset,offset+size)): return None
        owned.update(range(offset,offset+size))
        parts.append([offset,''.join(chr(b) for b in wire[pos:pos+size])])
        pos+=size
    if pos!=len(wire)-1: return None
    return [generation,total,parts]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('revision-byte-order fixture 0', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,1,N,1,2,2,0,0,2,97,98,1,0,2,99,100])))), json.loads(json.dumps([256+N,258,[[0,'ab'],[256,'cd']]])))
check('revision-byte-order fixture 1', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,0,0,0,0])))), json.loads(json.dumps([0,0,[]])))
check('revision-byte-order fixture 2', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,1,0,3,1,0,1,2,98,99])))), json.loads(json.dumps([1,3,[[1,'bc']]])))
check('revision-byte-order fixture 3', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,70,1,0,0,0,0,0,0])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 4', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,2,0,0,0,0,0,0])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 5', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,1,0,0,0,0,0])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 6', json.loads(json.dumps(solve([82,71,1,0,0,0,0,0,0,0]))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 7', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,0,0,1,1,0,0,2,97,98])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 8', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,0,0,2,2,0,0,1,97,0,0,1,97])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 9', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,0,0,0,0,99])))), json.loads(json.dumps(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
revision-byte-order fixture 0	`[257, 258, [[0, 'ab'], [256, 'cd']]]`	`[257, 258, [[0, 'ab'], [256, 'cd']]]`	Passed
revision-byte-order fixture 1	`[0, 0, []]`	`[0, 0, []]`	Passed
revision-byte-order fixture 2	`[256, 3, [[1, 'bc']]]`	`[1, 3, [[1, 'bc']]]`	Failed
revision-byte-order fixture 3	`None`	`None`	Passed
revision-byte-order fixture 4	`None`	`None`	Passed
revision-byte-order fixture 5	`None`	`None`	Passed
revision-byte-order fixture 6	`None`	`None`	Passed
revision-byte-order fixture 7	`None`	`None`	Passed
revision-byte-order fixture 8	`None`	`None`	Passed
revision-byte-order fixture 9	`None`	`None`	Passed

SHA-256 / 4dfb6d68e1f71b0c2dbd1d8be00965024caac5862454fc0d0572ef805632bfc1

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    wire=x
    if len(wire)<10 or any(not 0<=b<=255 for b in wire): return None
    if wire[:2]!=[82,71]: return None
    if wire[2]!=1: return None
    if wire[3]!=0: return None
    if sum(wire[:-1])%256!=wire[-1]: return None
    generation=wire[5]
    total=wire[6]*256+wire[7]
    count=wire[8]
    pos=9
    parts=[]
    owned=set()
    for _ in range(count):
        if pos+3>len(wire)-1: return None
        offset=wire[pos]*256+wire[pos+1]
        size=wire[pos+2]
        pos+=3
        if pos+size>len(wire)-1 or offset+size>total: return None
        if any(i in owned for i in range(offset,offset+size)): return None
        owned.update(range(offset,offset+size))
        parts.append([offset,''.join(chr(b) for b in wire[pos:pos+size])])
        pos+=size
    if pos!=len(wire)-1: return None
    return [generation,total,parts]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('revision-byte-order fixture 0', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,1,N,1,2,2,0,0,2,97,98,1,0,2,99,100])))), json.loads(json.dumps([256+N,258,[[0,'ab'],[256,'cd']]])))
check('revision-byte-order fixture 1', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,0,0,0,0])))), json.loads(json.dumps([0,0,[]])))
check('revision-byte-order fixture 2', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,1,0,3,1,0,1,2,98,99])))), json.loads(json.dumps([1,3,[[1,'bc']]])))
check('revision-byte-order fixture 3', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,70,1,0,0,0,0,0,0])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 4', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,2,0,0,0,0,0,0])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 5', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,1,0,0,0,0,0])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 6', json.loads(json.dumps(solve([82,71,1,0,0,0,0,0,0,0]))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 7', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,0,0,1,1,0,0,2,97,98])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 8', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,0,0,2,2,0,0,1,97,0,0,1,97])))), json.loads(json.dumps(None)))
check('revision-byte-order fixture 9', json.loads(json.dumps(solve((lambda w:w+[sum(w)%256])([82,71,1,0,0,0,0,0,0,99])))), json.loads(json.dumps(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
revision-byte-order fixture 0	`[1, 258, [[0, 'ab'], [256, 'cd']]]`	`[257, 258, [[0, 'ab'], [256, 'cd']]]`	Failed
revision-byte-order fixture 1	`[0, 0, []]`	`[0, 0, []]`	Passed
revision-byte-order fixture 2	`[1, 3, [[1, 'bc']]]`	`[1, 3, [[1, 'bc']]]`	Passed
revision-byte-order fixture 3	`None`	`None`	Passed
revision-byte-order fixture 4	`None`	`None`	Passed
revision-byte-order fixture 5	`None`	`None`	Passed
revision-byte-order fixture 6	`None`	`None`	Passed
revision-byte-order fixture 7	`None`	`None`	Passed
revision-byte-order fixture 8	`None`	`None`	Passed
revision-byte-order fixture 9	`None`	`None`	Passed

SHA-256 / daf6ef96329a47832c92557401ff0793b19fc926c000b4faf6eee3d3c616ee68

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 10 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

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 2026-09-29T14:41:24.490689+00:00.

Case digest / 6b388a11ecc343f328743543585098f1f7377fd231a77786aee996f86e144cb6