FA-6751 / HTTP caching / Open access

Must revalidate blocks stale use despite request allowance · case 01

Must revalidate blocks stale use despite request allowance.

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

ROOT CAUSE

The faulty implementation uses `not stale or permitted` for the must-revalidate-blocks-stale-use-despite-request-allowance decision.

VERIFIED REPAIR

Apply the explicit must-revalidate-blocks-stale-use-despite-request-allowance contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `permitted and not must` and still violates a separate fixture.

Case contract

Bounded offline decision model: must revalidate blocks stale use despite request allowance. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.

Why this case matters

This deterministic http caching model isolates the must-revalidate-blocks-stale-use-despite-request-allowance 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(stale, must, permitted):
    return not stale or permitted
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(True, True, True), False)", "check('fixture 2', solve(False, True, False), True)", "check('fixture 3', solve(True, False, True), True)", "check('fixture 4', solve(True, False, False), False)"]
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	`True`	`True`	Passed
fixture 4	`False`	`False`	Passed
fixture 1	`True`	`False`	Failed

SHA-256 / 83283386f564a87c6f73de0bac7c53fb5f0fda3f048ff3b782ec2c6daa659cd7

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(stale, must, permitted):
    return permitted and not must
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(True, True, True), False)", "check('fixture 2', solve(False, True, False), True)", "check('fixture 3', solve(True, False, True), True)", "check('fixture 4', solve(True, False, False), False)"]
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`	`True`	Passed
fixture 4	`False`	`False`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / ac2f2be33b1b577b998dfde54222ea18475c603689ebb7a59893711c75477e7b

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(stale, must, permitted):
    return not stale or (permitted and not must)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(True, True, True), False)", "check('fixture 2', solve(False, True, False), True)", "check('fixture 3', solve(True, False, True), True)", "check('fixture 4', solve(True, False, False), False)"]
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	`True`	`True`	Passed
fixture 4	`False`	`False`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / 01ebe5cb865cfb35d5cda699906da91c66f8c589d08c799040058fdf1787cf6f

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 2026-09-29T14:38:04.926602+00:00.

Case digest / 23cc696f35d14e824ac66b3139a6de424401d1534f79c21cfa82069050fa1c16