FA-98226 / Attention mask construction / Open access

Global keys remain hidden from earlier queries · case 01

Global keys remain hidden from earlier queries.

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

ROOT CAUSE

The mask applies causal order but never adds the global-key exception.

THE FAILURE

The mask applies causal order but never adds the global-key exception.

Unsuccessful approach: Applying global status to query positions lets those rows see future keys.

Case contract

Causal visibility plus globally visible key indices; special query positions still obey causality.

Why this case matters

A small explicit visibility matrix makes sequence-attention boundary behavior reviewable.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(length, global_keys):
    return [[j<=i for j in range(length)] for i in range(length)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
g=[0]
check('global keys only',solve(N+2,g),[[j<=i or j in g for j in range(N+2)] for i in range(N+2)])
check('global-key exception applies to a query row',solve(3,[1])[0],[True,True,False])
check('no globals',solve(3,[]),[[j<=i for j in range(3)] for i in range(3)])
check('empty',solve(0,[]),[])
check('singleton global key',solve(1,[0]),[[True]])
check('later global key visible early',solve(3,[2])[1],[True,True,True])
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
global keys only	`[[True, False, False], [True, True, False], [True, True, True]]`	`[[True, False, False], [True, True, False], [True, True, True]]`	Passed
global-key exception applies to a query row	`[True, False, False]`	`[True, True, False]`	Failed
no globals	`[[True, False, False], [True, True, False], [True, True, True]]`	`[[True, False, False], [True, True, False], [True, True, True]]`	Passed
empty	`[]`	`[]`	Passed
singleton global key	`[[True]]`	`[[True]]`	Passed
later global key visible early	`[True, True, False]`	`[True, True, True]`	Failed

SHA-256 / 4e07470bc0cb5583dc88fd493f018e03c344500fec1fed1c4af66082f6e25dcf

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(length, global_keys):
    return [[j<=i or i in global_keys or j in global_keys for j in range(length)] for i in range(length)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
g=[0]
check('global keys only',solve(N+2,g),[[j<=i or j in g for j in range(N+2)] for i in range(N+2)])
check('global-key exception applies to a query row',solve(3,[1])[0],[True,True,False])
check('no globals',solve(3,[]),[[j<=i for j in range(3)] for i in range(3)])
check('empty',solve(0,[]),[])
check('singleton global key',solve(1,[0]),[[True]])
check('later global key visible early',solve(3,[2])[1],[True,True,True])
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
global keys only	`[[True, True, True], [True, True, False], [True, True, True]]`	`[[True, False, False], [True, True, False], [True, True, True]]`	Failed
global-key exception applies to a query row	`[True, True, False]`	`[True, True, False]`	Passed
no globals	`[[True, False, False], [True, True, False], [True, True, True]]`	`[[True, False, False], [True, True, False], [True, True, True]]`	Passed
empty	`[]`	`[]`	Passed
singleton global key	`[[True]]`	`[[True]]`	Passed
later global key visible early	`[True, True, True]`	`[True, True, True]`	Passed

SHA-256 / 1a98423392fd29d4f700786e2e92b8fce89902bf7a299c26548d7522add6bba4

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 6 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

These are toy Boolean matrix contracts; they do not define a production model architecture or tensor library behavior. 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 2026-09-30T16:48:10.630274+00:00.

Case digest / 3554407f74413cac96fe0d3c95364a9aee59e803f445372d2b2304e952726127