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FA-28951 / HTTP redirects / Open access

Account for a redirect chain using a monotonic deadline and separate response timing: drain latency · case 01

Account for a redirect chain using a monotonic deadline and separate response timing: the drain latency branch emits an incorrect decision.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The drain-latency decision uses 'released-started'; this violates the stipulated controller policy.

VERIFIED REPAIR

At this decision use 'released-headers', preserving the other controller outputs.

Unsuccessful approach: The partial repair uses 'now-headers' and still fails an explicit boundary or control.

Case contract

Account for a redirect chain using a monotonic deadline and separate response timing. The explicit fixture inputs and outputs define a bounded offline policy; request identity must accompany the decision.

Why this case matters

Models a redirect controller decision before following a target or exposing a redirect result.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from urllib.parse import urlsplit, unquote, quote
import posixpath
import re
N = 1
observations = []
def solve(request, started, headers, released, now, deadline, offset):
    return {'request': request, 'decision': [max(0,deadline-now), headers-started, released-started, now-started, now>=deadline, now+offset, deadline, now-released, headers==started, released-started]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', 10, 13, 15, 18, 20, 1000), {'request': '/requests/' + str(N) + '/0', 'decision': [2, 3, 2, 8, False, 1018, 20, 3, False, 5]})
check('fixture 2', solve('/requests/' + str(N) + '/1', 0, 0, 0, 0, 0, 500), {'request': '/requests/' + str(N) + '/1', 'decision': [0, 0, 0, 0, True, 500, 0, 0, True, 0]})
check('fixture 3', solve('/requests/' + str(N) + '/2', 20, 25, 29, 35, 30, -100), {'request': '/requests/' + str(N) + '/2', 'decision': [0, 5, 4, 15, True, -65, 30, 6, False, 9]})
check('fixture 4', solve('/requests/' + str(N) + '/3', 10, 11, 12, 12, 100, 0), {'request': '/requests/' + str(N) + '/3', 'decision': [88, 1, 1, 2, False, 12, 100, 0, False, 2]})
check('fixture 5', solve('/requests/' + str(N) + '/4', 5, 9, 10, 14, 15, 400), {'request': '/requests/' + str(N) + '/4', 'decision': [1, 4, 1, 9, False, 414, 15, 4, False, 5]})
check('fixture 6', solve('/requests/' + str(N) + '/5', 100, 105, 110, 120, 121, -500), {'request': '/requests/' + str(N) + '/5', 'decision': [1, 5, 5, 20, False, -380, 121, 10, False, 10]})
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 1{'decision': [2, 3, 5, 8, False, 1018, 20, 3, False, 5], 'request': '/requests/1/0'}{'decision': [2, 3, 2, 8, False, 1018, 20, 3, False, 5], 'request': '/requests/1/0'}Failed
fixture 2{'decision': [0, 0, 0, 0, True, 500, 0, 0, True, 0], 'request': '/requests/1/1'}{'decision': [0, 0, 0, 0, True, 500, 0, 0, True, 0], 'request': '/requests/1/1'}Passed
fixture 3{'decision': [0, 5, 9, 15, True, -65, 30, 6, False, 9], 'request': '/requests/1/2'}{'decision': [0, 5, 4, 15, True, -65, 30, 6, False, 9], 'request': '/requests/1/2'}Failed
fixture 4{'decision': [88, 1, 2, 2, False, 12, 100, 0, False, 2], 'request': '/requests/1/3'}{'decision': [88, 1, 1, 2, False, 12, 100, 0, False, 2], 'request': '/requests/1/3'}Failed
fixture 5{'decision': [1, 4, 5, 9, False, 414, 15, 4, False, 5], 'request': '/requests/1/4'}{'decision': [1, 4, 1, 9, False, 414, 15, 4, False, 5], 'request': '/requests/1/4'}Failed
fixture 6{'decision': [1, 5, 10, 20, False, -380, 121, 10, False, 10], 'request': '/requests/1/5'}{'decision': [1, 5, 5, 20, False, -380, 121, 10, False, 10], 'request': '/requests/1/5'}Failed

SHA-256 / 3a148477e019910a080b510b9932e8e27fefd80aaee1e6f75c2b2be2dbafaf38

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from urllib.parse import urlsplit, unquote, quote
import posixpath
import re
N = 1
observations = []
def solve(request, started, headers, released, now, deadline, offset):
    return {'request': request, 'decision': [max(0,deadline-now), headers-started, now-headers, now-started, now>=deadline, now+offset, deadline, now-released, headers==started, released-started]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', 10, 13, 15, 18, 20, 1000), {'request': '/requests/' + str(N) + '/0', 'decision': [2, 3, 2, 8, False, 1018, 20, 3, False, 5]})
check('fixture 2', solve('/requests/' + str(N) + '/1', 0, 0, 0, 0, 0, 500), {'request': '/requests/' + str(N) + '/1', 'decision': [0, 0, 0, 0, True, 500, 0, 0, True, 0]})
check('fixture 3', solve('/requests/' + str(N) + '/2', 20, 25, 29, 35, 30, -100), {'request': '/requests/' + str(N) + '/2', 'decision': [0, 5, 4, 15, True, -65, 30, 6, False, 9]})
check('fixture 4', solve('/requests/' + str(N) + '/3', 10, 11, 12, 12, 100, 0), {'request': '/requests/' + str(N) + '/3', 'decision': [88, 1, 1, 2, False, 12, 100, 0, False, 2]})
check('fixture 5', solve('/requests/' + str(N) + '/4', 5, 9, 10, 14, 15, 400), {'request': '/requests/' + str(N) + '/4', 'decision': [1, 4, 1, 9, False, 414, 15, 4, False, 5]})
check('fixture 6', solve('/requests/' + str(N) + '/5', 100, 105, 110, 120, 121, -500), {'request': '/requests/' + str(N) + '/5', 'decision': [1, 5, 5, 20, False, -380, 121, 10, False, 10]})
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 1{'decision': [2, 3, 5, 8, False, 1018, 20, 3, False, 5], 'request': '/requests/1/0'}{'decision': [2, 3, 2, 8, False, 1018, 20, 3, False, 5], 'request': '/requests/1/0'}Failed
fixture 2{'decision': [0, 0, 0, 0, True, 500, 0, 0, True, 0], 'request': '/requests/1/1'}{'decision': [0, 0, 0, 0, True, 500, 0, 0, True, 0], 'request': '/requests/1/1'}Passed
fixture 3{'decision': [0, 5, 10, 15, True, -65, 30, 6, False, 9], 'request': '/requests/1/2'}{'decision': [0, 5, 4, 15, True, -65, 30, 6, False, 9], 'request': '/requests/1/2'}Failed
fixture 4{'decision': [88, 1, 1, 2, False, 12, 100, 0, False, 2], 'request': '/requests/1/3'}{'decision': [88, 1, 1, 2, False, 12, 100, 0, False, 2], 'request': '/requests/1/3'}Passed
fixture 5{'decision': [1, 4, 5, 9, False, 414, 15, 4, False, 5], 'request': '/requests/1/4'}{'decision': [1, 4, 1, 9, False, 414, 15, 4, False, 5], 'request': '/requests/1/4'}Failed
fixture 6{'decision': [1, 5, 15, 20, False, -380, 121, 10, False, 10], 'request': '/requests/1/5'}{'decision': [1, 5, 5, 20, False, -380, 121, 10, False, 10], 'request': '/requests/1/5'}Failed

SHA-256 / 421725104471d0e9c21c9b254ec981dbc1a8a087cd7fa0467894445fce2f3c7b

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json
from urllib.parse import urlsplit, unquote, quote
import posixpath
import re
N = 1
observations = []
def solve(request, started, headers, released, now, deadline, offset):
    return {'request': request, 'decision': [max(0,deadline-now), headers-started, released-headers, now-started, now>=deadline, now+offset, deadline, now-released, headers==started, released-started]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', 10, 13, 15, 18, 20, 1000), {'request': '/requests/' + str(N) + '/0', 'decision': [2, 3, 2, 8, False, 1018, 20, 3, False, 5]})
check('fixture 2', solve('/requests/' + str(N) + '/1', 0, 0, 0, 0, 0, 500), {'request': '/requests/' + str(N) + '/1', 'decision': [0, 0, 0, 0, True, 500, 0, 0, True, 0]})
check('fixture 3', solve('/requests/' + str(N) + '/2', 20, 25, 29, 35, 30, -100), {'request': '/requests/' + str(N) + '/2', 'decision': [0, 5, 4, 15, True, -65, 30, 6, False, 9]})
check('fixture 4', solve('/requests/' + str(N) + '/3', 10, 11, 12, 12, 100, 0), {'request': '/requests/' + str(N) + '/3', 'decision': [88, 1, 1, 2, False, 12, 100, 0, False, 2]})
check('fixture 5', solve('/requests/' + str(N) + '/4', 5, 9, 10, 14, 15, 400), {'request': '/requests/' + str(N) + '/4', 'decision': [1, 4, 1, 9, False, 414, 15, 4, False, 5]})
check('fixture 6', solve('/requests/' + str(N) + '/5', 100, 105, 110, 120, 121, -500), {'request': '/requests/' + str(N) + '/5', 'decision': [1, 5, 5, 20, False, -380, 121, 10, False, 10]})
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 1{'decision': [2, 3, 2, 8, False, 1018, 20, 3, False, 5], 'request': '/requests/1/0'}{'decision': [2, 3, 2, 8, False, 1018, 20, 3, False, 5], 'request': '/requests/1/0'}Passed
fixture 2{'decision': [0, 0, 0, 0, True, 500, 0, 0, True, 0], 'request': '/requests/1/1'}{'decision': [0, 0, 0, 0, True, 500, 0, 0, True, 0], 'request': '/requests/1/1'}Passed
fixture 3{'decision': [0, 5, 4, 15, True, -65, 30, 6, False, 9], 'request': '/requests/1/2'}{'decision': [0, 5, 4, 15, True, -65, 30, 6, False, 9], 'request': '/requests/1/2'}Passed
fixture 4{'decision': [88, 1, 1, 2, False, 12, 100, 0, False, 2], 'request': '/requests/1/3'}{'decision': [88, 1, 1, 2, False, 12, 100, 0, False, 2], 'request': '/requests/1/3'}Passed
fixture 5{'decision': [1, 4, 1, 9, False, 414, 15, 4, False, 5], 'request': '/requests/1/4'}{'decision': [1, 4, 1, 9, False, 414, 15, 4, False, 5], 'request': '/requests/1/4'}Passed
fixture 6{'decision': [1, 5, 5, 20, False, -380, 121, 10, False, 10], 'request': '/requests/1/5'}{'decision': [1, 5, 5, 20, False, -380, 121, 10, False, 10], 'request': '/requests/1/5'}Passed

SHA-256 / 2c8b70faa2465ede3af43ff46ce46203f318a91151427625386a3dd9a06ede12

Verification & scope

Stipulated offline redirect policy, not a complete HTTP, browser, URL, cache, or security implementation. Numbered variants vary request correlation identity. 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 2026-09-29T14:41:38.544761+00:00.

Case digest / 1dfdbc94536beec7efbbd719f993bfeab4a8ec4e3feb706a3f0c8164eecd624d