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FA-28871 / HTTP redirects / Open access

Serialize a redirect response under an explicit server-side response policy: fragment location preserved · case 01

Serialize a redirect response under an explicit server-side response policy: the fragment location preserved branch emits an incorrect decision.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The fragment-location-preserved decision uses "target.split('#')[0]"; this violates the stipulated controller policy.

THE FAILURE

The fragment-location-preserved decision uses "target.split('#')[0]"; this violates the stipulated controller policy.

Unsuccessful approach: The partial repair uses "target.split('?')[0]" and still fails an explicit boundary or control.

Case contract

Serialize a redirect response under an explicit server-side response policy. 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, status, target, method, body, head, custom_headers):
    return {'request': request, 'decision': [dict(custom_headers, Location=target), '' if head else body, len(body.encode('utf-8')), status, target.replace('&','&'), target.replace(chr(34),'"'), target.split('#')[0], custom_headers, body == "", status == 303]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', 302, '/a?x=1&y=2', 'GET', 'move', False, {'X': 'v'}), {'request': '/requests/' + str(N) + '/0', 'decision': [{'X': 'v', 'Location': '/a?x=1&y=2'}, 'move', 4, 302, '/a?x=1&y=2', '/a?x=1&y=2', '/a?x=1&y=2', {'X': 'v'}, False, False]})
check('fixture 2', solve('/requests/' + str(N) + '/1', 303, '/a#part', 'POST', 'next', False, {}), {'request': '/requests/' + str(N) + '/1', 'decision': [{'Location': '/a#part'}, 'next', 4, 303, '/a#part', '/a#part', '/a#part', {}, False, True]})
check('fixture 3', solve('/requests/' + str(N) + '/2', 307, '/unicode/é', 'PUT', 'café', True, {'Content-Length': '999'}), {'request': '/requests/' + str(N) + '/2', 'decision': [{'Content-Length': '999', 'Location': '/unicode/é'}, '', 5, 307, '/unicode/é', '/unicode/é', '/unicode/é', {'Content-Length': '999'}, False, False]})
check('fixture 4', solve('/requests/' + str(N) + '/3', 308, '/', 'HEAD', 'moved', True, {}), {'request': '/requests/' + str(N) + '/3', 'decision': [{'Location': '/'}, '', 5, 308, '/', '/', '/', {}, False, False]})
check('fixture 5', solve('/requests/' + str(N) + '/4', 301, '/b', 'GET', '', False, {'Location': '/stale'}), {'request': '/requests/' + str(N) + '/4', 'decision': [{'Location': '/b'}, '', 0, 301, '/b', '/b', '/b', {'Location': '/stale'}, True, False]})
check('fixture 6', solve('/requests/' + str(N) + '/5', 302, '/a"b', 'GET', 'x', False, {'Content-Type': 'custom'}), {'request': '/requests/' + str(N) + '/5', 'decision': [{'Content-Type': 'custom', 'Location': '/a"b'}, 'x', 1, 302, '/a"b', '/a"b', '/a"b', {'Content-Type': 'custom'}, False, False]})
check('fixture 7', solve('/requests/' + str(N) + '/6', 303, '/e', 'GET', 'abc', False, {}), {'request': '/requests/' + str(N) + '/6', 'decision': [{'Location': '/e'}, 'abc', 3, 303, '/e', '/e', '/e', {}, False, True]})
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': [{'Location': '/a?x=1&y=2', 'X': 'v'}, 'move', 4, 302, '/a?x=1&y=2', '/a?x=1&y=2', '/a?x=1&y=2', {'X': 'v'}, False, False], 'request': '/requests/1/0'}{'decision': [{'Location': '/a?x=1&y=2', 'X': 'v'}, 'move', 4, 302, '/a?x=1&y=2', '/a?x=1&y=2', '/a?x=1&y=2', {'X': 'v'}, False, False], 'request': '/requests/1/0'}Passed
fixture 2{'decision': [{'Location': '/a#part'}, 'next', 4, 303, '/a#part', '/a#part', '/a', {}, False, True], 'request': '/requests/1/1'}{'decision': [{'Location': '/a#part'}, 'next', 4, 303, '/a#part', '/a#part', '/a#part', {}, False, True], 'request': '/requests/1/1'}Failed
fixture 3{'decision': [{'Content-Length': '999', 'Location': '/unicode/é'}, '', 5, 307, '/unicode/é', '/unicode/é', '/unicode/é', {'Content-Length': '999'}, False, False], 'request': '/requests/1/2'}{'decision': [{'Content-Length': '999', 'Location': '/unicode/é'}, '', 5, 307, '/unicode/é', '/unicode/é', '/unicode/é', {'Content-Length': '999'}, False, False], 'request': '/requests/1/2'}Passed
fixture 4{'decision': [{'Location': '/'}, '', 5, 308, '/', '/', '/', {}, False, False], 'request': '/requests/1/3'}{'decision': [{'Location': '/'}, '', 5, 308, '/', '/', '/', {}, False, False], 'request': '/requests/1/3'}Passed
fixture 5{'decision': [{'Location': '/b'}, '', 0, 301, '/b', '/b', '/b', {'Location': '/stale'}, True, False], 'request': '/requests/1/4'}{'decision': [{'Location': '/b'}, '', 0, 301, '/b', '/b', '/b', {'Location': '/stale'}, True, False], 'request': '/requests/1/4'}Passed
fixture 6{'decision': [{'Content-Type': 'custom', 'Location': '/a"b'}, 'x', 1, 302, '/a"b', '/a"b', '/a"b', {'Content-Type': 'custom'}, False, False], 'request': '/requests/1/5'}{'decision': [{'Content-Type': 'custom', 'Location': '/a"b'}, 'x', 1, 302, '/a"b', '/a"b', '/a"b', {'Content-Type': 'custom'}, False, False], 'request': '/requests/1/5'}Passed
fixture 7{'decision': [{'Location': '/e'}, 'abc', 3, 303, '/e', '/e', '/e', {}, False, True], 'request': '/requests/1/6'}{'decision': [{'Location': '/e'}, 'abc', 3, 303, '/e', '/e', '/e', {}, False, True], 'request': '/requests/1/6'}Passed

SHA-256 / 7972cba677e9659bbf89a8e475e478f8b1ccf4fd5ad8fadcbaa57423112994ba

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, status, target, method, body, head, custom_headers):
    return {'request': request, 'decision': [dict(custom_headers, Location=target), '' if head else body, len(body.encode('utf-8')), status, target.replace('&','&'), target.replace(chr(34),'"'), target.split('?')[0], custom_headers, body == "", status == 303]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', 302, '/a?x=1&y=2', 'GET', 'move', False, {'X': 'v'}), {'request': '/requests/' + str(N) + '/0', 'decision': [{'X': 'v', 'Location': '/a?x=1&y=2'}, 'move', 4, 302, '/a?x=1&y=2', '/a?x=1&y=2', '/a?x=1&y=2', {'X': 'v'}, False, False]})
check('fixture 2', solve('/requests/' + str(N) + '/1', 303, '/a#part', 'POST', 'next', False, {}), {'request': '/requests/' + str(N) + '/1', 'decision': [{'Location': '/a#part'}, 'next', 4, 303, '/a#part', '/a#part', '/a#part', {}, False, True]})
check('fixture 3', solve('/requests/' + str(N) + '/2', 307, '/unicode/é', 'PUT', 'café', True, {'Content-Length': '999'}), {'request': '/requests/' + str(N) + '/2', 'decision': [{'Content-Length': '999', 'Location': '/unicode/é'}, '', 5, 307, '/unicode/é', '/unicode/é', '/unicode/é', {'Content-Length': '999'}, False, False]})
check('fixture 4', solve('/requests/' + str(N) + '/3', 308, '/', 'HEAD', 'moved', True, {}), {'request': '/requests/' + str(N) + '/3', 'decision': [{'Location': '/'}, '', 5, 308, '/', '/', '/', {}, False, False]})
check('fixture 5', solve('/requests/' + str(N) + '/4', 301, '/b', 'GET', '', False, {'Location': '/stale'}), {'request': '/requests/' + str(N) + '/4', 'decision': [{'Location': '/b'}, '', 0, 301, '/b', '/b', '/b', {'Location': '/stale'}, True, False]})
check('fixture 6', solve('/requests/' + str(N) + '/5', 302, '/a"b', 'GET', 'x', False, {'Content-Type': 'custom'}), {'request': '/requests/' + str(N) + '/5', 'decision': [{'Content-Type': 'custom', 'Location': '/a"b'}, 'x', 1, 302, '/a"b', '/a"b', '/a"b', {'Content-Type': 'custom'}, False, False]})
check('fixture 7', solve('/requests/' + str(N) + '/6', 303, '/e', 'GET', 'abc', False, {}), {'request': '/requests/' + str(N) + '/6', 'decision': [{'Location': '/e'}, 'abc', 3, 303, '/e', '/e', '/e', {}, False, True]})
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': [{'Location': '/a?x=1&y=2', 'X': 'v'}, 'move', 4, 302, '/a?x=1&y=2', '/a?x=1&y=2', '/a', {'X': 'v'}, False, False], 'request': '/requests/1/0'}{'decision': [{'Location': '/a?x=1&y=2', 'X': 'v'}, 'move', 4, 302, '/a?x=1&y=2', '/a?x=1&y=2', '/a?x=1&y=2', {'X': 'v'}, False, False], 'request': '/requests/1/0'}Failed
fixture 2{'decision': [{'Location': '/a#part'}, 'next', 4, 303, '/a#part', '/a#part', '/a#part', {}, False, True], 'request': '/requests/1/1'}{'decision': [{'Location': '/a#part'}, 'next', 4, 303, '/a#part', '/a#part', '/a#part', {}, False, True], 'request': '/requests/1/1'}Passed
fixture 3{'decision': [{'Content-Length': '999', 'Location': '/unicode/é'}, '', 5, 307, '/unicode/é', '/unicode/é', '/unicode/é', {'Content-Length': '999'}, False, False], 'request': '/requests/1/2'}{'decision': [{'Content-Length': '999', 'Location': '/unicode/é'}, '', 5, 307, '/unicode/é', '/unicode/é', '/unicode/é', {'Content-Length': '999'}, False, False], 'request': '/requests/1/2'}Passed
fixture 4{'decision': [{'Location': '/'}, '', 5, 308, '/', '/', '/', {}, False, False], 'request': '/requests/1/3'}{'decision': [{'Location': '/'}, '', 5, 308, '/', '/', '/', {}, False, False], 'request': '/requests/1/3'}Passed
fixture 5{'decision': [{'Location': '/b'}, '', 0, 301, '/b', '/b', '/b', {'Location': '/stale'}, True, False], 'request': '/requests/1/4'}{'decision': [{'Location': '/b'}, '', 0, 301, '/b', '/b', '/b', {'Location': '/stale'}, True, False], 'request': '/requests/1/4'}Passed
fixture 6{'decision': [{'Content-Type': 'custom', 'Location': '/a"b'}, 'x', 1, 302, '/a"b', '/a"b', '/a"b', {'Content-Type': 'custom'}, False, False], 'request': '/requests/1/5'}{'decision': [{'Content-Type': 'custom', 'Location': '/a"b'}, 'x', 1, 302, '/a"b', '/a"b', '/a"b', {'Content-Type': 'custom'}, False, False], 'request': '/requests/1/5'}Passed
fixture 7{'decision': [{'Location': '/e'}, 'abc', 3, 303, '/e', '/e', '/e', {}, False, True], 'request': '/requests/1/6'}{'decision': [{'Location': '/e'}, 'abc', 3, 303, '/e', '/e', '/e', {}, False, True], 'request': '/requests/1/6'}Passed

SHA-256 / 345675622da7980e32bfe9af2f5d95011a7e37bd715b4a39bd635c303e4cfac3

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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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 2026-09-29T14:41:37.934037+00:00.

Case digest / 910b8305addf2cd1412d47c40404385837ed26d9f4aa3fe457cb72c573c0587a