FA-98143 / Attention mask construction / Member archive
Future keys leak through a reversed causal comparison · case 03
Future keys leak through a reversed causal comparison.
Case contract
For length L, return an LxL lower triangle including diagonal. L may be zero.
Why this case matters
A small explicit visibility matrix makes sequence-attention boundary behavior reviewable.
One recorded failure
Sample boundary fixtureThis sample comes from the broken implementation of a controlled reproducer.
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| middle row | [[true, true, true, true], [false, true, true, true], [false, false, true, true], [false, false, false, true]] | [[true, false, false, false], [true, true, false, false], [true, true, true, false], [true, true, true, true]] | Failed |
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