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FA-7076 / Proxy forwarding / Open access

Upstream attempt history preserves equal statuses · case 01

Upstream attempt history preserves equal statuses.

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

ROOT CAUSE

The faulty implementation uses `[{"attempt":i+1,"status":status,"elapsed":elapsed} for i,(status,elapsed) in enumerate(dict.fromkeys(attempts))]` for the upstream-attempt-history-preserves-equal-statuses decision.

VERIFIED REPAIR

Apply the explicit upstream-attempt-history-preserves-equal-statuses contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `[{"attempt":1,"status":attempts[-1][0],"elapsed":attempts[-1][1]}] if attempts else []` and still violates a separate fixture.

Case contract

Given attempts, upstream attempt history preserves equal statuses. Return the protocol decision or transformed value; fields are validated and fixtures state boundary outcomes.

Why this case matters

This deterministic proxy forwarding model isolates the upstream-attempt-history-preserves-equal-statuses 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(attempts):
    return [{"attempt":i+1,"status":status,"elapsed":elapsed} for i,(status,elapsed) in enumerate(dict.fromkeys(attempts))]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve([(502, 2), (502, 2), (200, 1)]), [{'attempt': 1, 'status': 502, 'elapsed': 2}, {'attempt': 2, 'status': 502, 'elapsed': 2}, {'attempt': 3, 'status': 200, 'elapsed': 1}])", "check('fixture 2', solve([]), [])", "check('fixture 3', solve([(200, 1)]), [{'attempt': 1, 'status': 200, 'elapsed': 1}])", "check('fixture 4', solve([(503, 2), (200, 3)]), [{'attempt': 1, 'status': 503, 'elapsed': 2}, {'attempt': 2, 'status': 200, 'elapsed': 3}])"]
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 fixtureActualExpectedOutcome
fixture 2[][]Passed
fixture 3[{'attempt': 1, 'elapsed': 1, 'status': 200}][{'attempt': 1, 'elapsed': 1, 'status': 200}]Passed
fixture 4[{'attempt': 1, 'elapsed': 2, 'status': 503}, {'attempt': 2, 'elapsed': 3, 'status': 200}][{'attempt': 1, 'elapsed': 2, 'status': 503}, {'attempt': 2, 'elapsed': 3, 'status': 200}]Passed
fixture 1[{'attempt': 1, 'elapsed': 2, 'status': 502}, {'attempt': 2, 'elapsed': 1, 'status': 200}][{'attempt': 1, 'elapsed': 2, 'status': 502}, {'attempt': 2, 'elapsed': 2, 'status': 502}, {'attempt': 3, 'elapsed': 1, 'status': 200}]Failed

SHA-256 / 3c2d54cb7860fa0f7b9ee89ade20d4fc031ae0edeeaa74bf1a9f8a93453b8802

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(attempts):
    return [{"attempt":1,"status":attempts[-1][0],"elapsed":attempts[-1][1]}] if attempts else []
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve([(502, 2), (502, 2), (200, 1)]), [{'attempt': 1, 'status': 502, 'elapsed': 2}, {'attempt': 2, 'status': 502, 'elapsed': 2}, {'attempt': 3, 'status': 200, 'elapsed': 1}])", "check('fixture 2', solve([]), [])", "check('fixture 3', solve([(200, 1)]), [{'attempt': 1, 'status': 200, 'elapsed': 1}])", "check('fixture 4', solve([(503, 2), (200, 3)]), [{'attempt': 1, 'status': 503, 'elapsed': 2}, {'attempt': 2, 'status': 200, 'elapsed': 3}])"]
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 fixtureActualExpectedOutcome
fixture 2[][]Passed
fixture 3[{'attempt': 1, 'elapsed': 1, 'status': 200}][{'attempt': 1, 'elapsed': 1, 'status': 200}]Passed
fixture 4[{'attempt': 1, 'elapsed': 3, 'status': 200}][{'attempt': 1, 'elapsed': 2, 'status': 503}, {'attempt': 2, 'elapsed': 3, 'status': 200}]Failed
fixture 1[{'attempt': 1, 'elapsed': 1, 'status': 200}][{'attempt': 1, 'elapsed': 2, 'status': 502}, {'attempt': 2, 'elapsed': 2, 'status': 502}, {'attempt': 3, 'elapsed': 1, 'status': 200}]Failed

SHA-256 / 26467563fbdb794944db75402ed66628028bc480922e8f4a567cbbd798d046fb

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(attempts):
    return [{"attempt":i+1,"status":status,"elapsed":elapsed} for i,(status,elapsed) in enumerate(attempts)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve([(502, 2), (502, 2), (200, 1)]), [{'attempt': 1, 'status': 502, 'elapsed': 2}, {'attempt': 2, 'status': 502, 'elapsed': 2}, {'attempt': 3, 'status': 200, 'elapsed': 1}])", "check('fixture 2', solve([]), [])", "check('fixture 3', solve([(200, 1)]), [{'attempt': 1, 'status': 200, 'elapsed': 1}])", "check('fixture 4', solve([(503, 2), (200, 3)]), [{'attempt': 1, 'status': 503, 'elapsed': 2}, {'attempt': 2, 'status': 200, 'elapsed': 3}])"]
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 fixtureActualExpectedOutcome
fixture 2[][]Passed
fixture 3[{'attempt': 1, 'elapsed': 1, 'status': 200}][{'attempt': 1, 'elapsed': 1, 'status': 200}]Passed
fixture 4[{'attempt': 1, 'elapsed': 2, 'status': 503}, {'attempt': 2, 'elapsed': 3, 'status': 200}][{'attempt': 1, 'elapsed': 2, 'status': 503}, {'attempt': 2, 'elapsed': 3, 'status': 200}]Passed
fixture 1[{'attempt': 1, 'elapsed': 2, 'status': 502}, {'attempt': 2, 'elapsed': 2, 'status': 502}, {'attempt': 3, 'elapsed': 1, 'status': 200}][{'attempt': 1, 'elapsed': 2, 'status': 502}, {'attempt': 2, 'elapsed': 2, 'status': 502}, {'attempt': 3, 'elapsed': 1, 'status': 200}]Passed

SHA-256 / 7d1f19651ea9848773c9e304039228417922c8aa24c060c2782508998adbf065

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 2026-09-29T14:38:08.062766+00:00.

Case digest / adea1382659483d39fb7f611d3000643ac34b46e116698adf327fdf4a3894d03