FA-26581 / HTTP ranges / Open access
Representation checksum excludes multipart envelope bytes · case 01
Representation checksum excludes multipart envelope bytes.
ROOT CAUSE
The stream-checksum-body-only decision uses return sum(map(ord,"".join(payloads+headers)))%257.
VERIFIED REPAIR
Apply the bounded decision exactly: return sum(map(ord,"".join(payloads)))%257
Unsuccessful approach: The partial repair uses return sum(map(ord,"".join(payloads))), which still violates the stated contract.
Case contract
Local checksum is sum ASCII code points modulo 257 over payloads only. Framing headers are not representation data.
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(payloads, headers):
return sum(map(ord,"".join(payloads+headers)))%257
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('stream-checksum-body-only fixture 0', solve( ["z"*(N+3)],["Header"]), (122*(N+3))%257)
check('stream-checksum-body-only fixture 1', solve(["a"],["b"]), 97)
check('stream-checksum-body-only fixture 2', solve([],["header"]), 0)
check('stream-checksum-body-only fixture 3', solve([],[]), 0)
check('stream-checksum-body-only fixture 4', solve(["ab"],[]), 195)
check('stream-checksum-body-only fixture 5', solve(["z","z","z"],[]), 109)
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 |
|---|---|---|---|
| stream-checksum-body-only fixture 0 | 45 | 231 | Failed |
| stream-checksum-body-only fixture 1 | 195 | 97 | Failed |
| stream-checksum-body-only fixture 2 | 103 | 0 | Failed |
| stream-checksum-body-only fixture 3 | 0 | 0 | Passed |
| stream-checksum-body-only fixture 4 | 195 | 195 | Passed |
| stream-checksum-body-only fixture 5 | 109 | 109 | Passed |
SHA-256 / 92380ff7cfad2ad813f0ea98f0a9aeb565bb1a356a5253387b9a2b6be18916a3
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(payloads, headers):
return sum(map(ord,"".join(payloads)))
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('stream-checksum-body-only fixture 0', solve( ["z"*(N+3)],["Header"]), (122*(N+3))%257)
check('stream-checksum-body-only fixture 1', solve(["a"],["b"]), 97)
check('stream-checksum-body-only fixture 2', solve([],["header"]), 0)
check('stream-checksum-body-only fixture 3', solve([],[]), 0)
check('stream-checksum-body-only fixture 4', solve(["ab"],[]), 195)
check('stream-checksum-body-only fixture 5', solve(["z","z","z"],[]), 109)
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 |
|---|---|---|---|
| stream-checksum-body-only fixture 0 | 488 | 231 | Failed |
| stream-checksum-body-only fixture 1 | 97 | 97 | Passed |
| stream-checksum-body-only fixture 2 | 0 | 0 | Passed |
| stream-checksum-body-only fixture 3 | 0 | 0 | Passed |
| stream-checksum-body-only fixture 4 | 195 | 195 | Passed |
| stream-checksum-body-only fixture 5 | 366 | 109 | Failed |
SHA-256 / 292646ece0e94c5f859be937809529d3f3d7d10da04366f36b51b871d92880f5
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(payloads, headers):
return sum(map(ord,"".join(payloads)))%257
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('stream-checksum-body-only fixture 0', solve( ["z"*(N+3)],["Header"]), (122*(N+3))%257)
check('stream-checksum-body-only fixture 1', solve(["a"],["b"]), 97)
check('stream-checksum-body-only fixture 2', solve([],["header"]), 0)
check('stream-checksum-body-only fixture 3', solve([],[]), 0)
check('stream-checksum-body-only fixture 4', solve(["ab"],[]), 195)
check('stream-checksum-body-only fixture 5', solve(["z","z","z"],[]), 109)
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 |
|---|---|---|---|
| stream-checksum-body-only fixture 0 | 231 | 231 | Passed |
| stream-checksum-body-only fixture 1 | 97 | 97 | Passed |
| stream-checksum-body-only fixture 2 | 0 | 0 | Passed |
| stream-checksum-body-only fixture 3 | 0 | 0 | Passed |
| stream-checksum-body-only fixture 4 | 195 | 195 | Passed |
| stream-checksum-body-only fixture 5 | 109 | 109 | Passed |
SHA-256 / b9a758f3c6aa6f828d04678710d8d94e9b059f001b0b63bd3c5ec7e2699539dc
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 2026-09-29T14:41:17.319425+00:00.
Case digest / db5133d8a992d88ca501b9803ef430472fbcbe79ba1593f00c4863e00421c7f4