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FA-28216 / HTTP redirects / Open access

Apply redirect interception to the current hop before validating and dispatching the selected target: synthetic stops network follow · case 01

Apply redirect interception to the current hop before validating and dispatching the selected target: the synthetic stops network follow branch emits an incorrect decision.

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

ROOT CAUSE

The synthetic-stops-network-follow decision uses "action == 'follow'"; this violates the stipulated controller policy.

VERIFIED REPAIR

At this decision use "action == 'follow' and not synthetic", preserving the other controller outputs.

Unsuccessful approach: The partial repair uses 'not synthetic' and still fails an explicit boundary or control.

Case contract

Apply redirect interception to the current hop before validating and dispatching the selected target. 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, original, current, location, override, action, status, callback_status, headers, synthetic, cached):
    return {'request': request, 'decision': [location if override is None else override, status, action == 'follow', current, headers, action == 'follow', action != 'error', True, urlsplit(location if override is None else override).scheme in ('','http','https'), callback_status if synthetic else None]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', 'https://a/x', 'https://b/y', '/next', 'https://c/z', 'follow', 302, 200, [['X', '1'], ['X', '2']], False, False), {'request': '/requests/' + str(N) + '/0', 'decision': ['https://c/z', 302, True, 'https://b/y', [['X', '1'], ['X', '2']], True, True, True, True, None]})
check('fixture 2', solve('/requests/' + str(N) + '/1', 'https://a/x', 'https://a/x', '/next', None, 'manual', 307, None, [], False, True), {'request': '/requests/' + str(N) + '/1', 'decision': ['/next', 307, False, 'https://a/x', [], False, True, True, True, None]})
check('fixture 3', solve('/requests/' + str(N) + '/2', 'https://a/x', 'https://b/y', '/next', '', 'follow', 303, 204, [['Y', 'v']], True, True), {'request': '/requests/' + str(N) + '/2', 'decision': ['', 303, True, 'https://b/y', [['Y', 'v']], False, True, True, True, 204]})
check('fixture 4', solve('/requests/' + str(N) + '/3', 'https://a/x', 'https://b/y', 'https://safe/x', 'file:/local', 'cancel', 301, 201, [], False, False), {'request': '/requests/' + str(N) + '/3', 'decision': ['file:/local', 301, False, 'https://b/y', [], False, True, True, False, None]})
check('fixture 5', solve('/requests/' + str(N) + '/4', 'https://a/x', 'https://b/y', '/next', None, 'error', 308, None, [['X', '1']], False, True), {'request': '/requests/' + str(N) + '/4', 'decision': ['/next', 308, False, 'https://b/y', [['X', '1']], False, False, True, True, None]})
check('fixture 6', solve('/requests/' + str(N) + '/5', 'https://a/x', 'https://b/y', '/next', '/custom', 'manual', 302, 202, [['Z', '1']], True, False), {'request': '/requests/' + str(N) + '/5', 'decision': ['/custom', 302, False, 'https://b/y', [['Z', '1']], False, True, True, True, 202]})
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': ['https://c/z', 302, True, 'https://b/y', [['X', '1'], ['X', '2']], True, True, True, True, None], 'request': '/requests/1/0'}{'decision': ['https://c/z', 302, True, 'https://b/y', [['X', '1'], ['X', '2']], True, True, True, True, None], 'request': '/requests/1/0'}Passed
fixture 2{'decision': ['/next', 307, False, 'https://a/x', [], False, True, True, True, None], 'request': '/requests/1/1'}{'decision': ['/next', 307, False, 'https://a/x', [], False, True, True, True, None], 'request': '/requests/1/1'}Passed
fixture 3{'decision': ['', 303, True, 'https://b/y', [['Y', 'v']], True, True, True, True, 204], 'request': '/requests/1/2'}{'decision': ['', 303, True, 'https://b/y', [['Y', 'v']], False, True, True, True, 204], 'request': '/requests/1/2'}Failed
fixture 4{'decision': ['file:/local', 301, False, 'https://b/y', [], False, True, True, False, None], 'request': '/requests/1/3'}{'decision': ['file:/local', 301, False, 'https://b/y', [], False, True, True, False, None], 'request': '/requests/1/3'}Passed
fixture 5{'decision': ['/next', 308, False, 'https://b/y', [['X', '1']], False, False, True, True, None], 'request': '/requests/1/4'}{'decision': ['/next', 308, False, 'https://b/y', [['X', '1']], False, False, True, True, None], 'request': '/requests/1/4'}Passed
fixture 6{'decision': ['/custom', 302, False, 'https://b/y', [['Z', '1']], False, True, True, True, 202], 'request': '/requests/1/5'}{'decision': ['/custom', 302, False, 'https://b/y', [['Z', '1']], False, True, True, True, 202], 'request': '/requests/1/5'}Passed

SHA-256 / 0feae9b7eed1858dd74cd2dc7894b8cab1911098d986dbfccdc3bd2066c12c07

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, original, current, location, override, action, status, callback_status, headers, synthetic, cached):
    return {'request': request, 'decision': [location if override is None else override, status, action == 'follow', current, headers, not synthetic, action != 'error', True, urlsplit(location if override is None else override).scheme in ('','http','https'), callback_status if synthetic else None]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', 'https://a/x', 'https://b/y', '/next', 'https://c/z', 'follow', 302, 200, [['X', '1'], ['X', '2']], False, False), {'request': '/requests/' + str(N) + '/0', 'decision': ['https://c/z', 302, True, 'https://b/y', [['X', '1'], ['X', '2']], True, True, True, True, None]})
check('fixture 2', solve('/requests/' + str(N) + '/1', 'https://a/x', 'https://a/x', '/next', None, 'manual', 307, None, [], False, True), {'request': '/requests/' + str(N) + '/1', 'decision': ['/next', 307, False, 'https://a/x', [], False, True, True, True, None]})
check('fixture 3', solve('/requests/' + str(N) + '/2', 'https://a/x', 'https://b/y', '/next', '', 'follow', 303, 204, [['Y', 'v']], True, True), {'request': '/requests/' + str(N) + '/2', 'decision': ['', 303, True, 'https://b/y', [['Y', 'v']], False, True, True, True, 204]})
check('fixture 4', solve('/requests/' + str(N) + '/3', 'https://a/x', 'https://b/y', 'https://safe/x', 'file:/local', 'cancel', 301, 201, [], False, False), {'request': '/requests/' + str(N) + '/3', 'decision': ['file:/local', 301, False, 'https://b/y', [], False, True, True, False, None]})
check('fixture 5', solve('/requests/' + str(N) + '/4', 'https://a/x', 'https://b/y', '/next', None, 'error', 308, None, [['X', '1']], False, True), {'request': '/requests/' + str(N) + '/4', 'decision': ['/next', 308, False, 'https://b/y', [['X', '1']], False, False, True, True, None]})
check('fixture 6', solve('/requests/' + str(N) + '/5', 'https://a/x', 'https://b/y', '/next', '/custom', 'manual', 302, 202, [['Z', '1']], True, False), {'request': '/requests/' + str(N) + '/5', 'decision': ['/custom', 302, False, 'https://b/y', [['Z', '1']], False, True, True, True, 202]})
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': ['https://c/z', 302, True, 'https://b/y', [['X', '1'], ['X', '2']], True, True, True, True, None], 'request': '/requests/1/0'}{'decision': ['https://c/z', 302, True, 'https://b/y', [['X', '1'], ['X', '2']], True, True, True, True, None], 'request': '/requests/1/0'}Passed
fixture 2{'decision': ['/next', 307, False, 'https://a/x', [], True, True, True, True, None], 'request': '/requests/1/1'}{'decision': ['/next', 307, False, 'https://a/x', [], False, True, True, True, None], 'request': '/requests/1/1'}Failed
fixture 3{'decision': ['', 303, True, 'https://b/y', [['Y', 'v']], False, True, True, True, 204], 'request': '/requests/1/2'}{'decision': ['', 303, True, 'https://b/y', [['Y', 'v']], False, True, True, True, 204], 'request': '/requests/1/2'}Passed
fixture 4{'decision': ['file:/local', 301, False, 'https://b/y', [], True, True, True, False, None], 'request': '/requests/1/3'}{'decision': ['file:/local', 301, False, 'https://b/y', [], False, True, True, False, None], 'request': '/requests/1/3'}Failed
fixture 5{'decision': ['/next', 308, False, 'https://b/y', [['X', '1']], True, False, True, True, None], 'request': '/requests/1/4'}{'decision': ['/next', 308, False, 'https://b/y', [['X', '1']], False, False, True, True, None], 'request': '/requests/1/4'}Failed
fixture 6{'decision': ['/custom', 302, False, 'https://b/y', [['Z', '1']], False, True, True, True, 202], 'request': '/requests/1/5'}{'decision': ['/custom', 302, False, 'https://b/y', [['Z', '1']], False, True, True, True, 202], 'request': '/requests/1/5'}Passed

SHA-256 / 18e6958cec3eda961f704f55d60ff11aa31340b5537a7d367c54aa6773c8e8d0

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, original, current, location, override, action, status, callback_status, headers, synthetic, cached):
    return {'request': request, 'decision': [location if override is None else override, status, action == 'follow', current, headers, action == 'follow' and not synthetic, action != 'error', True, urlsplit(location if override is None else override).scheme in ('','http','https'), callback_status if synthetic else None]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', 'https://a/x', 'https://b/y', '/next', 'https://c/z', 'follow', 302, 200, [['X', '1'], ['X', '2']], False, False), {'request': '/requests/' + str(N) + '/0', 'decision': ['https://c/z', 302, True, 'https://b/y', [['X', '1'], ['X', '2']], True, True, True, True, None]})
check('fixture 2', solve('/requests/' + str(N) + '/1', 'https://a/x', 'https://a/x', '/next', None, 'manual', 307, None, [], False, True), {'request': '/requests/' + str(N) + '/1', 'decision': ['/next', 307, False, 'https://a/x', [], False, True, True, True, None]})
check('fixture 3', solve('/requests/' + str(N) + '/2', 'https://a/x', 'https://b/y', '/next', '', 'follow', 303, 204, [['Y', 'v']], True, True), {'request': '/requests/' + str(N) + '/2', 'decision': ['', 303, True, 'https://b/y', [['Y', 'v']], False, True, True, True, 204]})
check('fixture 4', solve('/requests/' + str(N) + '/3', 'https://a/x', 'https://b/y', 'https://safe/x', 'file:/local', 'cancel', 301, 201, [], False, False), {'request': '/requests/' + str(N) + '/3', 'decision': ['file:/local', 301, False, 'https://b/y', [], False, True, True, False, None]})
check('fixture 5', solve('/requests/' + str(N) + '/4', 'https://a/x', 'https://b/y', '/next', None, 'error', 308, None, [['X', '1']], False, True), {'request': '/requests/' + str(N) + '/4', 'decision': ['/next', 308, False, 'https://b/y', [['X', '1']], False, False, True, True, None]})
check('fixture 6', solve('/requests/' + str(N) + '/5', 'https://a/x', 'https://b/y', '/next', '/custom', 'manual', 302, 202, [['Z', '1']], True, False), {'request': '/requests/' + str(N) + '/5', 'decision': ['/custom', 302, False, 'https://b/y', [['Z', '1']], False, True, True, True, 202]})
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': ['https://c/z', 302, True, 'https://b/y', [['X', '1'], ['X', '2']], True, True, True, True, None], 'request': '/requests/1/0'}{'decision': ['https://c/z', 302, True, 'https://b/y', [['X', '1'], ['X', '2']], True, True, True, True, None], 'request': '/requests/1/0'}Passed
fixture 2{'decision': ['/next', 307, False, 'https://a/x', [], False, True, True, True, None], 'request': '/requests/1/1'}{'decision': ['/next', 307, False, 'https://a/x', [], False, True, True, True, None], 'request': '/requests/1/1'}Passed
fixture 3{'decision': ['', 303, True, 'https://b/y', [['Y', 'v']], False, True, True, True, 204], 'request': '/requests/1/2'}{'decision': ['', 303, True, 'https://b/y', [['Y', 'v']], False, True, True, True, 204], 'request': '/requests/1/2'}Passed
fixture 4{'decision': ['file:/local', 301, False, 'https://b/y', [], False, True, True, False, None], 'request': '/requests/1/3'}{'decision': ['file:/local', 301, False, 'https://b/y', [], False, True, True, False, None], 'request': '/requests/1/3'}Passed
fixture 5{'decision': ['/next', 308, False, 'https://b/y', [['X', '1']], False, False, True, True, None], 'request': '/requests/1/4'}{'decision': ['/next', 308, False, 'https://b/y', [['X', '1']], False, False, True, True, None], 'request': '/requests/1/4'}Passed
fixture 6{'decision': ['/custom', 302, False, 'https://b/y', [['Z', '1']], False, True, True, True, 202], 'request': '/requests/1/5'}{'decision': ['/custom', 302, False, 'https://b/y', [['Z', '1']], False, True, True, True, 202], 'request': '/requests/1/5'}Passed

SHA-256 / e440e8dbb735e7c049eaa911949b23b67adda4efc9eacfdd4e61174256f30769

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 2026-09-29T14:41:31.951287+00:00.

Case digest / abf39703e244e56d12ec164e3a7420273f1b0ad8a4545a197c857b78a6f66620