FA-10686 / Rendering state / Open access

Color write mask channelwise · case 01

Any enabled color channel causes the entire pixel to be overwritten.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Any enabled color channel causes the entire pixel to be overwritten.

VERIFIED REPAIR

Use the stage contract: Old/new are four channels and mask contains four Booleans. Replace exactly the enabled channels.

Unsuccessful approach: Requiring all channels enabled suppresses valid partial-mask writes.

Case contract

Old/new are four channels and mask contains four Booleans. Replace exactly the enabled channels.

Why this case matters

A deterministic software graphics stage with explicit channel and coordinate conventions; no hardware, device profile or API behavior is inferred.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(old, new, mask):
    return list(new) if any(mask) else list(old)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*([1, 2, 3, 4], [9, 8, 7, 6], [True, False, True, False])), [9, 2, 7, 4])
check('fixture 2', solve(*([1, 2, 3, 4], [9, 8, 7, 6], [False, False, False, False])), [1, 2, 3, 4])
check('fixture 3', solve(*([1, 2, 3, 4], [9, 8, 7, 6], [True, True, True, True])), [9, 8, 7, 6])
check('fixture 4', solve(*([0, 0, 0, 0], [1, 2, 3, 4], [False, False, False, True])), [0, 0, 0, 4])
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 1	`[9, 8, 7, 6]`	`[9, 2, 7, 4]`	Failed
fixture 2	`[1, 2, 3, 4]`	`[1, 2, 3, 4]`	Passed
fixture 3	`[9, 8, 7, 6]`	`[9, 8, 7, 6]`	Passed
fixture 4	`[1, 2, 3, 4]`	`[0, 0, 0, 4]`	Failed

SHA-256 / ba1d273d4a441e2d85202323062360bf1b18b46d6b8ed8d4e42910296153145b

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(old, new, mask):
    return list(new) if all(mask) else list(old)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*([1, 2, 3, 4], [9, 8, 7, 6], [True, False, True, False])), [9, 2, 7, 4])
check('fixture 2', solve(*([1, 2, 3, 4], [9, 8, 7, 6], [False, False, False, False])), [1, 2, 3, 4])
check('fixture 3', solve(*([1, 2, 3, 4], [9, 8, 7, 6], [True, True, True, True])), [9, 8, 7, 6])
check('fixture 4', solve(*([0, 0, 0, 0], [1, 2, 3, 4], [False, False, False, True])), [0, 0, 0, 4])
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 1	`[1, 2, 3, 4]`	`[9, 2, 7, 4]`	Failed
fixture 2	`[1, 2, 3, 4]`	`[1, 2, 3, 4]`	Passed
fixture 3	`[9, 8, 7, 6]`	`[9, 8, 7, 6]`	Passed
fixture 4	`[0, 0, 0, 0]`	`[0, 0, 0, 4]`	Failed

SHA-256 / fc248f2112dadc1f86593ae684abd765353e22d701fed6012733ca16366d93a8

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(old, new, mask):
    return [n if enabled else o for o,n,enabled in zip(old,new,mask)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*([1, 2, 3, 4], [9, 8, 7, 6], [True, False, True, False])), [9, 2, 7, 4])
check('fixture 2', solve(*([1, 2, 3, 4], [9, 8, 7, 6], [False, False, False, False])), [1, 2, 3, 4])
check('fixture 3', solve(*([1, 2, 3, 4], [9, 8, 7, 6], [True, True, True, True])), [9, 8, 7, 6])
check('fixture 4', solve(*([0, 0, 0, 0], [1, 2, 3, 4], [False, False, False, True])), [0, 0, 0, 4])
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 1	`[9, 2, 7, 4]`	`[9, 2, 7, 4]`	Passed
fixture 2	`[1, 2, 3, 4]`	`[1, 2, 3, 4]`	Passed
fixture 3	`[9, 8, 7, 6]`	`[9, 8, 7, 6]`	Passed
fixture 4	`[0, 0, 0, 4]`	`[0, 0, 0, 4]`	Passed

SHA-256 / 6f5ff32d15dad3dc16f5d32e1a78c74dd57d7576f1096200ebd52e04c77a819b

Verification & scope

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 2026-09-29T14:38:41.249830+00:00.

Case digest / 32818ee34fc2d78a1557dbd73197a7eb0951e19d63e984278a39a36fc7829044