FA-7001 / Proxy forwarding / Open access

Te forwarding allows trailers but not transfer codings · case 01

Te forwarding allows trailers but not transfer codings.

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

ROOT CAUSE

The faulty implementation uses `values` for the te-forwarding-allows-trailers-but-not-transfer-codings decision.

VERIFIED REPAIR

Apply the explicit te-forwarding-allows-trailers-but-not-transfer-codings contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `[]` and still violates a separate fixture.

Case contract

Bounded offline decision model: te forwarding allows trailers but not transfer codings. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.

Why this case matters

This deterministic proxy forwarding model isolates the te-forwarding-allows-trailers-but-not-transfer-codings 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(values):
    return values
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(['gzip', 'trailers']), ['trailers'])", "check('fixture 2', solve([]), [])", "check('fixture 3', solve(['Trailers']), ['Trailers'])", "check('fixture 4', solve(['gzip']), [])"]
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	`[]`	`[]`	Passed
fixture 3	`['Trailers']`	`['Trailers']`	Passed
fixture 4	`['gzip']`	`[]`	Failed
fixture 1	`['gzip', 'trailers']`	`['trailers']`	Failed

SHA-256 / 6f14c4bced4e6dbbe2455eb32cb98321ec800905b401343d9e999cab2cb69e91

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(values):
    return []
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(['gzip', 'trailers']), ['trailers'])", "check('fixture 2', solve([]), [])", "check('fixture 3', solve(['Trailers']), ['Trailers'])", "check('fixture 4', solve(['gzip']), [])"]
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	`[]`	`[]`	Passed
fixture 3	`[]`	`['Trailers']`	Failed
fixture 4	`[]`	`[]`	Passed
fixture 1	`[]`	`['trailers']`	Failed

SHA-256 / 7da8a11395b8f557686bb3a1f1f410166a281f1161ada2e8d46717fe53607be1

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(values):
    return [v for v in values if v.lower() == "trailers"]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(['gzip', 'trailers']), ['trailers'])", "check('fixture 2', solve([]), [])", "check('fixture 3', solve(['Trailers']), ['Trailers'])", "check('fixture 4', solve(['gzip']), [])"]
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	`[]`	`[]`	Passed
fixture 3	`['Trailers']`	`['Trailers']`	Passed
fixture 4	`[]`	`[]`	Passed
fixture 1	`['trailers']`	`['trailers']`	Passed

SHA-256 / 1747e65e9cb2628c23d49a47beda6c01377b012c9cb5022c98361df6cfc1507c

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 2026-09-29T14:38:07.383228+00:00.

Case digest / de4bd1e7330fd070de73297cd13232cd9d8a2d340d6dab40e80900240a6ec116