FA-7491 / Multiplexed protocols / Open access
Http2 initial window change applies delta to existing streams · case 01
Http2 initial window change applies delta to existing streams.
ROOT CAUSE
The faulty implementation uses `new` for the http2-initial-window-change-applies-delta-to-existing-streams decision.
VERIFIED REPAIR
Apply the explicit http2-initial-window-change-applies-delta-to-existing-streams contract, including the tested boundary and negative cases.
Unsuccessful approach: The attempted repair uses `max(0,current+new-old)` and still violates a separate fixture.
Case contract
Bounded offline decision model: http2 initial window change applies delta to existing streams. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.
Why this case matters
This deterministic multiplexed protocols model isolates the http2-initial-window-change-applies-delta-to-existing-streams 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(current, old, new):
return new
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(3, 10, 5), -2)", "check('fixture 2', solve(7, 10, 20), 17)", "check('fixture 3', solve(0, 0, 0), 0)", "check('fixture 4', solve(4, 5, 5), 4)"]
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 | 20 | 17 | Failed |
| fixture 3 | 0 | 0 | Passed |
| fixture 4 | 5 | 4 | Failed |
| fixture 1 | 5 | -2 | Failed |
SHA-256 / 41564783c8a9702bda31fff7250cf470a8712e8595203f9b11a875bad252c3a6
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(current, old, new):
return max(0,current+new-old)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(3, 10, 5), -2)", "check('fixture 2', solve(7, 10, 20), 17)", "check('fixture 3', solve(0, 0, 0), 0)", "check('fixture 4', solve(4, 5, 5), 4)"]
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 | 17 | 17 | Passed |
| fixture 3 | 0 | 0 | Passed |
| fixture 4 | 4 | 4 | Passed |
| fixture 1 | 0 | -2 | Failed |
SHA-256 / 03483de441276442eae1d23b91a74fc0b207a75eacd3b7d178518f134355b09e
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(current, old, new):
return current+new-old
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(3, 10, 5), -2)", "check('fixture 2', solve(7, 10, 20), 17)", "check('fixture 3', solve(0, 0, 0), 0)", "check('fixture 4', solve(4, 5, 5), 4)"]
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 | 17 | 17 | Passed |
| fixture 3 | 0 | 0 | Passed |
| fixture 4 | 4 | 4 | Passed |
| fixture 1 | -2 | -2 | Passed |
SHA-256 / 67c531af2b9e53a1bf692bd53b73398788d593173a6cafdcfa2888931753227c
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 2026-09-29T14:38:12.578487+00:00.
Case digest / 86fbbaeab55645076dc4790ea9e9d6f71503d3a19223e9cba00c2e15f72bbbcc