FA-89026 / Digital logic simulation / Open access

Released drivers still take part in resolution · case 01

A strong driver in high impedance beats an active weak driver and the net reads 'z' or 'x'.

Verified by executionVariant 1 · 11 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Drivers outputting 'z' are not removed before comparing strengths.

VERIFIED REPAIR

Drop every 'z' driver before resolution.

Unsuccessful approach: Keeping a lone released driver still bypasses the keeper when the bus has one tri-stated driver.

Case contract

Input [drivers, keeper]: drivers are [value, strength] with value in 0/1/x/z and strength weak < pull < strong. 'z' drivers are ignored. With no active driver the net is the keeper value, or 'z' when keeper is None. Otherwise only drivers at the highest present strength matter: a single agreed value wins, any disagreement (including x) gives 'x'.

Why this case matters

Resolved nets in switch-level and RTL simulators combine drivers by strength; mixing up strengths or keepers changes observed bus values.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(*args):
    drivers, keep = args
    rank = {'weak': 0, 'pull': 1, 'strong': 2}
    live = list(drivers)
    if not live:
        return keep if keep is not None else 'z'
    top = max(live, key=lambda d: rank[d[1]])[1]
    vals = sorted({v for v, s in live if s == top})
    return vals[0] if len(vals) == 1 else 'x'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong']], '1'], '1'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong']], '0'], '0'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong'], ['z', 'strong']], '1'], '1'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], '0'], '0'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak'], ['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], '1'], '1'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak'], ['1', 'weak'], ['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
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
strong beats weak listed first	`x`	`1`	Failed
pull beats weak listed first	`1`	`1`	Passed
strong contention	`x`	`x`	Passed
pull contention with weak agreement	`x`	`x`	Passed
released strong driver beside weak one	`z`	`1`	Failed
all released with keeper	`z`	`1`	Failed
single released driver with keeper	`z`	`1`	Failed
all released without keeper	`z`	`z`	Passed
weak driver disagrees with keeper	`1`	`1`	Passed
weak unknown under strong driver	`0`	`0`	Passed
pull unknown under strong driver	`1`	`1`	Passed

SHA-256 / 653de9f6368e670df89a6747bcc9f4a8b6f424390d54e101f464bb4d9d2ba405

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(*args):
    drivers, keep = args
    rank = {'weak': 0, 'pull': 1, 'strong': 2}
    live = [(v, s) for v, s in drivers if v != 'z' or len(drivers) == 1]
    if not live:
        return keep if keep is not None else 'z'
    top = max(live, key=lambda d: rank[d[1]])[1]
    vals = sorted({v for v, s in live if s == top})
    return vals[0] if len(vals) == 1 else 'x'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong']], '1'], '1'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong']], '0'], '0'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong'], ['z', 'strong']], '1'], '1'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], '0'], '0'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak'], ['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], '1'], '1'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak'], ['1', 'weak'], ['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
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
strong beats weak listed first	`1`	`1`	Passed
pull beats weak listed first	`1`	`1`	Passed
strong contention	`x`	`x`	Passed
pull contention with weak agreement	`x`	`x`	Passed
released strong driver beside weak one	`1`	`1`	Passed
all released with keeper	`z`	`1`	Failed
single released driver with keeper	`z`	`1`	Failed
all released without keeper	`z`	`z`	Passed
weak driver disagrees with keeper	`1`	`1`	Passed
weak unknown under strong driver	`0`	`0`	Passed
pull unknown under strong driver	`1`	`1`	Passed

SHA-256 / b7fd8df0d26ad356d01ce2843781f108b2c83cae98d9c43b1a6b294a568bc3c9

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(*args):
    drivers, keep = args
    rank = {'weak': 0, 'pull': 1, 'strong': 2}
    live = [(v, s) for v, s in drivers if v != 'z']
    if not live:
        return keep if keep is not None else 'z'
    top = max(live, key=lambda d: rank[d[1]])[1]
    vals = sorted({v for v, s in live if s == top})
    return vals[0] if len(vals) == 1 else 'x'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong']], '1'], '1'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong']], '0'], '0'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong'], ['z', 'strong']], '1'], '1'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], '0'], '0'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak'], ['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')], [('strong beats weak listed first', [[['0', 'weak'], ['1', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], None], '1'), ('pull beats weak listed first', [[['0', 'weak'], ['1', 'pull']], None], '1'), ('strong contention', [[['0', 'strong'], ['1', 'strong'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull'], ['1', 'pull']], None], 'x'), ('pull contention with weak agreement', [[['1', 'pull'], ['0', 'pull'], ['1', 'weak']], '1'], 'x'), ('released strong driver beside weak one', [[['z', 'strong'], ['1', 'weak']], None], '1'), ('all released with keeper', [[['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong'], ['z', 'strong']], '1'], '1'), ('single released driver with keeper', [[['z', 'pull']], '1'], '1'), ('all released without keeper', [[['z', 'weak'], ['z', 'strong']], None], 'z'), ('weak driver disagrees with keeper', [[['1', 'weak'], ['1', 'weak'], ['1', 'weak'], ['1', 'weak'], ['1', 'weak']], '0'], '1'), ('weak unknown under strong driver', [[['x', 'weak'], ['0', 'strong']], None], '0'), ('pull unknown under strong driver', [[['x', 'pull'], ['1', 'strong']], '0'], '1')]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
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
strong beats weak listed first	`1`	`1`	Passed
pull beats weak listed first	`1`	`1`	Passed
strong contention	`x`	`x`	Passed
pull contention with weak agreement	`x`	`x`	Passed
released strong driver beside weak one	`1`	`1`	Passed
all released with keeper	`1`	`1`	Passed
single released driver with keeper	`1`	`1`	Passed
all released without keeper	`z`	`z`	Passed
weak driver disagrees with keeper	`1`	`1`	Passed
weak unknown under strong driver	`0`	`0`	Passed
pull unknown under strong driver	`1`	`1`	Passed

SHA-256 / 11d65161a439fb144e29d24d4e3b05e3d2267d0bd545676d9e259f637309ef9d

Verification & scope

A deterministic bounded teaching model of one simulator rule set; the contract is stipulated and is not a claim of conformance to any HDL standard or commercial simulator. 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 2026-09-29T14:51:13.575081+00:00.

Case digest / 242e55abd25eff8bf9e979bf1e10718e7771f4fcd5faff50aa8797028857614e