FAILURE MAP
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FA-26496 / HTTP ranges / Open access

Overlapping fragments must agree on their bytes · case 01

Overlapping fragments must agree on their bytes.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The cache-overlap-byte-conflict decision uses return sorted({s+i:c for s,b in fragments for i,c in enumerate(b)}.items()).

VERIFIED REPAIR

Apply the bounded decision exactly: seen={} for s,b in fragments: for i,c in enumerate(b): if s+i in seen and seen[s+i]!=c: return None seen[s+i]=c return sorted(seen.items())

Unsuccessful approach: The partial repair uses seen={} for s,b in fragments: for i,c in enumerate(b): if s+i in seen: return None seen[s+i]=c return sorted(seen.items()), which still violates the stated contract.

Case contract

Fragments are [absolute-offset,ASCII-body]. Return sorted [offset,char] cells; reject conflicting bytes with None. Identical overlap is permitted.

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(fragments):
    return sorted({s+i:c for s,b in fragments for i,c in enumerate(b)}.items())
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('cache-overlap-byte-conflict fixture 0', solve([[N,"ab"],[N+1,"x"]]), None)
check('cache-overlap-byte-conflict fixture 1', solve([[N,"ab"],[N+1,"b"]]), [(N,"a"),(N+1,"b")])
check('cache-overlap-byte-conflict fixture 2', solve([]), [])
check('cache-overlap-byte-conflict fixture 3', solve([[0,"a"]]), [(0,"a")])
check('cache-overlap-byte-conflict fixture 4', solve([[1,"b"],[0,"a"]]), [(0,"a"),(1,"b")])
check('cache-overlap-byte-conflict fixture 5', solve([[0,""]]), [])
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
cache-overlap-byte-conflict fixture 0[[1, 'a'], [2, 'x']]NoneFailed
cache-overlap-byte-conflict fixture 1[[1, 'a'], [2, 'b']][[1, 'a'], [2, 'b']]Passed
cache-overlap-byte-conflict fixture 2[][]Passed
cache-overlap-byte-conflict fixture 3[[0, 'a']][[0, 'a']]Passed
cache-overlap-byte-conflict fixture 4[[0, 'a'], [1, 'b']][[0, 'a'], [1, 'b']]Passed
cache-overlap-byte-conflict fixture 5[][]Passed

SHA-256 / 7f901776c0d5fe91ee9d5a62245624f6c78ae4dad9e99a6df67ceb1a0d41b265

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(fragments):
    seen={}
    for s,b in fragments:
        for i,c in enumerate(b):
            if s+i in seen: return None
            seen[s+i]=c
    return sorted(seen.items())
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('cache-overlap-byte-conflict fixture 0', solve([[N,"ab"],[N+1,"x"]]), None)
check('cache-overlap-byte-conflict fixture 1', solve([[N,"ab"],[N+1,"b"]]), [(N,"a"),(N+1,"b")])
check('cache-overlap-byte-conflict fixture 2', solve([]), [])
check('cache-overlap-byte-conflict fixture 3', solve([[0,"a"]]), [(0,"a")])
check('cache-overlap-byte-conflict fixture 4', solve([[1,"b"],[0,"a"]]), [(0,"a"),(1,"b")])
check('cache-overlap-byte-conflict fixture 5', solve([[0,""]]), [])
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
cache-overlap-byte-conflict fixture 0NoneNonePassed
cache-overlap-byte-conflict fixture 1None[[1, 'a'], [2, 'b']]Failed
cache-overlap-byte-conflict fixture 2[][]Passed
cache-overlap-byte-conflict fixture 3[[0, 'a']][[0, 'a']]Passed
cache-overlap-byte-conflict fixture 4[[0, 'a'], [1, 'b']][[0, 'a'], [1, 'b']]Passed
cache-overlap-byte-conflict fixture 5[][]Passed

SHA-256 / 83b31375f5cf1108fd51a277b07f5ae48fec66a3a080dc6fbf8726f6cabec04d

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(fragments):
    seen={}
    for s,b in fragments:
        for i,c in enumerate(b):
            if s+i in seen and seen[s+i]!=c: return None
            seen[s+i]=c
    return sorted(seen.items())
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('cache-overlap-byte-conflict fixture 0', solve([[N,"ab"],[N+1,"x"]]), None)
check('cache-overlap-byte-conflict fixture 1', solve([[N,"ab"],[N+1,"b"]]), [(N,"a"),(N+1,"b")])
check('cache-overlap-byte-conflict fixture 2', solve([]), [])
check('cache-overlap-byte-conflict fixture 3', solve([[0,"a"]]), [(0,"a")])
check('cache-overlap-byte-conflict fixture 4', solve([[1,"b"],[0,"a"]]), [(0,"a"),(1,"b")])
check('cache-overlap-byte-conflict fixture 5', solve([[0,""]]), [])
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
cache-overlap-byte-conflict fixture 0NoneNonePassed
cache-overlap-byte-conflict fixture 1[[1, 'a'], [2, 'b']][[1, 'a'], [2, 'b']]Passed
cache-overlap-byte-conflict fixture 2[][]Passed
cache-overlap-byte-conflict fixture 3[[0, 'a']][[0, 'a']]Passed
cache-overlap-byte-conflict fixture 4[[0, 'a'], [1, 'b']][[0, 'a'], [1, 'b']]Passed
cache-overlap-byte-conflict fixture 5[][]Passed

SHA-256 / cfd0e152f08b15419c8342d0b893b80cf9554c54febdc37d2060fd12bb9740d0

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 2026-09-29T14:41:16.452122+00:00.

Case digest / f3ff9c0c2f65cd2abd3cdbddf5f6b41299833a09f757186497b8a2c4547765b4