FA-12211 / Navigation route constraints / Open access

Lane guidance invents a connection to an exit lane · case 01

Lane guidance invents a connection to an exit lane in the controlled route-policy fixture.

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

ROOT CAUSE

The target lane is checked without conditioning on the current lane.

VERIFIED REPAIR

Check the ordered current-to-target lane pair in the explicit connectivity table.

Unsuccessful approach: Treating lane links as undirected invents reverse connectivity.

Case contract

Return whether a directed lane transition exists; identity transitions are allowed only if explicitly present.

Why this case matters

Navigation policies depend on road context that a shortest-path cost alone does not encode.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(current, target, links):
    return any(b == target for a,b in links)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
a,b,c = N,N+10,N+20
links = [(a,b),(c,c)]
check('listed transition', solve(a,b,links), True)
check('wrong source lane', solve(c,b,links), False)
check('reverse link absent', solve(b,a,links), False)
check('explicit self link', solve(c,c,links), True)
check('implicit self link denied', solve(a,a,links), False)
check('empty connectivity', solve(a,b,[]), False)
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
listed transition	`True`	`True`	Passed
wrong source lane	`True`	`False`	Failed
reverse link absent	`False`	`False`	Passed
explicit self link	`True`	`True`	Passed
implicit self link denied	`False`	`False`	Passed
empty connectivity	`False`	`False`	Passed

SHA-256 / 20e1b3c4e6ff0f702c7a08925c34721664d4d97f623a35f1b269dbd7176bfab0

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(current, target, links):
    return (current,target) in links or (target,current) in links
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
a,b,c = N,N+10,N+20
links = [(a,b),(c,c)]
check('listed transition', solve(a,b,links), True)
check('wrong source lane', solve(c,b,links), False)
check('reverse link absent', solve(b,a,links), False)
check('explicit self link', solve(c,c,links), True)
check('implicit self link denied', solve(a,a,links), False)
check('empty connectivity', solve(a,b,[]), False)
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
listed transition	`True`	`True`	Passed
wrong source lane	`False`	`False`	Passed
reverse link absent	`True`	`False`	Failed
explicit self link	`True`	`True`	Passed
implicit self link denied	`False`	`False`	Passed
empty connectivity	`False`	`False`	Passed

SHA-256 / a59d9e62af795609f9cb86c8dda1f73a14a1774b9a593c899a966e316692bd96

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(current, target, links):
    return (current,target) in links
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
a,b,c = N,N+10,N+20
links = [(a,b),(c,c)]
check('listed transition', solve(a,b,links), True)
check('wrong source lane', solve(c,b,links), False)
check('reverse link absent', solve(b,a,links), False)
check('explicit self link', solve(c,c,links), True)
check('implicit self link denied', solve(a,a,links), False)
check('empty connectivity', solve(a,b,[]), False)
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
listed transition	`True`	`True`	Passed
wrong source lane	`False`	`False`	Passed
reverse link absent	`False`	`False`	Passed
explicit self link	`True`	`True`	Passed
implicit self link denied	`False`	`False`	Passed
empty connectivity	`False`	`False`	Passed

SHA-256 / 6d43c0c484a9818fa2017b0dd2354204dbf9573a9c0caab23c96f0255b211eb1

Verification & scope

Simplified deterministic offline policy model; not a production router or authoritative road guidance. 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 2026-09-29T14:38:54.923378+00:00.

Case digest / ba3739a0eed73283bf7369c41c41c679e2adea9d266ebec245a1e9a5ad5ae3f9