FA-6696 / HTTP ranges / Open access

A range set is unsatisfiable only when every requested start is beyond the representation · case 01

A range set is unsatisfiable only when every requested start is beyond the representation.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The faulty implementation uses `any(s >= length for s in starts)` for the range-unsatisfiable decision.

VERIFIED REPAIR

Apply the explicit range-unsatisfiable contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `all(s > length for s in starts)` and still violates a separate fixture.

Case contract

A range set is unsatisfiable only when every requested start is beyond the representation: return the result specified by the explicit input/output boundary fixtures.

Why this case matters

This deterministic http ranges model isolates the range-unsatisfiable policy at a network component boundary.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(starts, length):
    return any(s >= length for s in starts)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve([0, 9], 5), False)", "check('fixture 2', solve([5], 5), True)", "check('fixture 3', solve([], 5), False)", "check('fixture 4', solve([7, 9], 5), True)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
    exec(_line)
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
fixture 2	`True`	`True`	Passed
fixture 3	`False`	`False`	Passed
fixture 4	`True`	`True`	Passed
fixture 1	`True`	`False`	Failed

SHA-256 / 9d0cb7e285941cd8d91f3906379a6f5f6c2b99695becbb7042eeca92da558bb6

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(starts, length):
    return all(s > length for s in starts)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve([0, 9], 5), False)", "check('fixture 2', solve([5], 5), True)", "check('fixture 3', solve([], 5), False)", "check('fixture 4', solve([7, 9], 5), True)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
    exec(_line)
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
fixture 2	`False`	`True`	Failed
fixture 3	`True`	`False`	Failed
fixture 4	`True`	`True`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / 2a33c8b57f7287f7e0bdf06dd1ebe612a8619156bc1a4c98f80811ba31b6b0a3

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(starts, length):
    return bool(starts) and all(s >= length for s in starts)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve([0, 9], 5), False)", "check('fixture 2', solve([5], 5), True)", "check('fixture 3', solve([], 5), False)", "check('fixture 4', solve([7, 9], 5), True)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
    exec(_line)
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
fixture 2	`True`	`True`	Passed
fixture 3	`False`	`False`	Passed
fixture 4	`True`	`True`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / 9b804a2d8ac7c4245b9ca171a63337b397b8b6d68697c7582f05affec0d02350

Verification & scope

Bounded deterministic policy model over validated inputs; not a complete protocol stack or an interoperability claim. The five variants rotate the same explicit fixture set. 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 2026-09-29T14:38:04.382498+00:00.

Case digest / 2dd35e9a8160f6b09253f61da473bce741a7591c9f6a2ca12f688b374b85ca0d