FA-26511 / HTTP ranges / Open access
A stitched response exposes the oldest contributing fragment age · case 01
A stitched response exposes the oldest contributing fragment age.
ROOT CAUSE
The cache-age-oldest-fragment decision uses return min(ages,default=0)+elapsed.
VERIFIED REPAIR
Apply the bounded decision exactly: return max(ages,default=0)+elapsed
Unsuccessful approach: The partial repair uses return sum(ages)//len(ages)+elapsed if ages else elapsed, which still violates the stated contract.
Case contract
Return max fragment age plus elapsed, or elapsed for no fragments. Inputs nonnegative integer seconds.
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(ages, elapsed):
return min(ages,default=0)+elapsed
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('cache-age-oldest-fragment fixture 0', solve([N,3*N],N), 4*N)
check('cache-age-oldest-fragment fixture 1', solve([3*N,N],0), 3*N)
check('cache-age-oldest-fragment fixture 2', solve([],N), N)
check('cache-age-oldest-fragment fixture 3', solve([0,0],N), N)
check('cache-age-oldest-fragment fixture 4', solve([N],N), 2*N)
check('cache-age-oldest-fragment fixture 5', solve([0,N,0],0), 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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| cache-age-oldest-fragment fixture 0 | 2 | 4 | Failed |
| cache-age-oldest-fragment fixture 1 | 1 | 3 | Failed |
| cache-age-oldest-fragment fixture 2 | 1 | 1 | Passed |
| cache-age-oldest-fragment fixture 3 | 1 | 1 | Passed |
| cache-age-oldest-fragment fixture 4 | 2 | 2 | Passed |
| cache-age-oldest-fragment fixture 5 | 0 | 1 | Failed |
SHA-256 / 9fe03f5b46127bc20cc80325b2681ddeffc88a49e0c0bc1b539afbcfdd6f0cef
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(ages, elapsed):
return sum(ages)//len(ages)+elapsed if ages else elapsed
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('cache-age-oldest-fragment fixture 0', solve([N,3*N],N), 4*N)
check('cache-age-oldest-fragment fixture 1', solve([3*N,N],0), 3*N)
check('cache-age-oldest-fragment fixture 2', solve([],N), N)
check('cache-age-oldest-fragment fixture 3', solve([0,0],N), N)
check('cache-age-oldest-fragment fixture 4', solve([N],N), 2*N)
check('cache-age-oldest-fragment fixture 5', solve([0,N,0],0), 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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| cache-age-oldest-fragment fixture 0 | 3 | 4 | Failed |
| cache-age-oldest-fragment fixture 1 | 2 | 3 | Failed |
| cache-age-oldest-fragment fixture 2 | 1 | 1 | Passed |
| cache-age-oldest-fragment fixture 3 | 1 | 1 | Passed |
| cache-age-oldest-fragment fixture 4 | 2 | 2 | Passed |
| cache-age-oldest-fragment fixture 5 | 0 | 1 | Failed |
SHA-256 / 8988481c2ab295527dd12e88be8dca8f78eae76669255d7320435ed0f1bf45c0
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(ages, elapsed):
return max(ages,default=0)+elapsed
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('cache-age-oldest-fragment fixture 0', solve([N,3*N],N), 4*N)
check('cache-age-oldest-fragment fixture 1', solve([3*N,N],0), 3*N)
check('cache-age-oldest-fragment fixture 2', solve([],N), N)
check('cache-age-oldest-fragment fixture 3', solve([0,0],N), N)
check('cache-age-oldest-fragment fixture 4', solve([N],N), 2*N)
check('cache-age-oldest-fragment fixture 5', solve([0,N,0],0), 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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| cache-age-oldest-fragment fixture 0 | 4 | 4 | Passed |
| cache-age-oldest-fragment fixture 1 | 3 | 3 | Passed |
| cache-age-oldest-fragment fixture 2 | 1 | 1 | Passed |
| cache-age-oldest-fragment fixture 3 | 1 | 1 | Passed |
| cache-age-oldest-fragment fixture 4 | 2 | 2 | Passed |
| cache-age-oldest-fragment fixture 5 | 1 | 1 | Passed |
SHA-256 / c9adfe8e6ecc5dda987ea5885f48be1c8e7ddce34489aebf0e38045c91d85aea
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 2026-09-29T14:41:16.696171+00:00.
Case digest / ca5ceb83f1ccf76aef3d15073a2f404bdbacdb8e3918d549bb7d77ebe45c8df9