FA-26786 / HTTP ranges / Open access
Completed byte positions count once across duplicate downloaded fragments · case 01
Completed byte positions count once across duplicate downloaded fragments.
ROOT CAUSE
The resume-progress-union-not-sum decision uses return sum(map(len,completed)).
THE FAILURE
The resume-progress-union-not-sum decision uses return sum(map(len,completed)).
Unsuccessful approach: The partial repair uses return max(map(len,completed),default=0), which still violates the stated contract.
Case contract
Input is a list of explicit downloaded byte-offset lists, not intervals. Return count of distinct durable byte positions.
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(completed):
return sum(map(len,completed))
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('resume-progress-union-not-sum fixture 0', solve([[0,N],[N,2*N]]), 3)
check('resume-progress-union-not-sum fixture 1', solve([[0],[N]]), 2)
check('resume-progress-union-not-sum fixture 2', solve([]), 0)
check('resume-progress-union-not-sum fixture 3', solve([[N],[N]]), 1)
check('resume-progress-union-not-sum fixture 4', solve([[],[]]), 0)
check('resume-progress-union-not-sum fixture 5', solve([[0,N,2*N]]), 3)
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 |
|---|---|---|---|
| resume-progress-union-not-sum fixture 0 | 4 | 3 | Failed |
| resume-progress-union-not-sum fixture 1 | 2 | 2 | Passed |
| resume-progress-union-not-sum fixture 2 | 0 | 0 | Passed |
| resume-progress-union-not-sum fixture 3 | 2 | 1 | Failed |
| resume-progress-union-not-sum fixture 4 | 0 | 0 | Passed |
| resume-progress-union-not-sum fixture 5 | 3 | 3 | Passed |
SHA-256 / b941422c1764edd61cc76737cec744156d8d89efaeead1e5e4ce6b165f5bdab8
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(completed):
return max(map(len,completed),default=0)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('resume-progress-union-not-sum fixture 0', solve([[0,N],[N,2*N]]), 3)
check('resume-progress-union-not-sum fixture 1', solve([[0],[N]]), 2)
check('resume-progress-union-not-sum fixture 2', solve([]), 0)
check('resume-progress-union-not-sum fixture 3', solve([[N],[N]]), 1)
check('resume-progress-union-not-sum fixture 4', solve([[],[]]), 0)
check('resume-progress-union-not-sum fixture 5', solve([[0,N,2*N]]), 3)
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 |
|---|---|---|---|
| resume-progress-union-not-sum fixture 0 | 2 | 3 | Failed |
| resume-progress-union-not-sum fixture 1 | 1 | 2 | Failed |
| resume-progress-union-not-sum fixture 2 | 0 | 0 | Passed |
| resume-progress-union-not-sum fixture 3 | 1 | 1 | Passed |
| resume-progress-union-not-sum fixture 4 | 0 | 0 | Passed |
| resume-progress-union-not-sum fixture 5 | 3 | 3 | Passed |
SHA-256 / 1893c143cfe44f24a91601f3581b1063be177dbb83797d6cdd5bc26630b317b7
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 6 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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Sign in to the archive ↗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 2026-09-29T14:41:19.053968+00:00.
Case digest / 9cc5d3a064a4e77319832f91ed77959fea8bda4dcfa818f565658cfc674ec9d8