The feature detects an undefended empty square on the back rank (or 7th rank for black) that is attacked by at least one enemy piece.
SAE concept sae_25953 fires when the feature detects an undefended empty square on the back rank (or 7th rank for black) that is attacked by at least one enemy piece.. It appears in 3 of 9,950 Climbchess puzzles (0.0%), spanning ELO 1941–1941 (median 1941).
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This page documents The feature detects an undefended empty square…, one of 4,505 interpretable chess concepts extracted from Leela Chess Zero via sparse autoencoders. The full feature description from our SAE labelling pipeline reads:
The feature detects an undefended empty square on the back rank (or 7th rank for black) that is attacked by at least one enemy piece.
This pattern fires in 3 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 1941 to 1941, with a median rating of 1941. That distribution tells you whether this is a beginner cue or a master-level subtlety.
Pattern statistics
| Concept ID | sae_25953 |
|---|---|
| Puzzles where it fires | 3 |
| Min ELO | 1941 |
| Median ELO | 1941 |
| Max ELO | 1941 |
| Coverage | 0.03% of puzzle set |
Related concepts
The five concepts most often co-firing alongside this one (Jaccard similarity over the puzzle co-occurrence graph) are:
Example puzzles
Below are 3 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.
- Puzzle z1hh8 — ELO 1941, themes: mate, mateIn2, middlegame, side to move: Black
- Puzzle z1hh8_F — ELO 1941, themes: mate, mateIn2, middlegame, side to move: White
- Puzzle z1hh8_M — ELO 1941, themes: mate, mateIn2, middlegame, side to move: Black
How to use this page
If you want to train this pattern, open the Climbchess trainer and filter for puzzles tagged with this concept. The trainer surfaces them at the right difficulty for your current rating, and tracks how often you spot the cue versus miss it. You can also browse the related concepts above to see neighbouring ideas in feature space.
Climbchess concepts are not heuristics written by a human author. Each one corresponds to a single direction in the residual stream of Leela Chess Zero that activates on a specific board feature, then was labelled by reading the top-activating positions. This makes the catalogue exhaustive (every Leela-detectable pattern is in here somewhere) and falsifiable (you can replay our extraction).
Frequently asked
What is SAE concept sae_25953?
The feature detects an undefended empty square on the back rank (or 7th rank for black) that is attacked by at least one enemy piece. It is one of 4,505 interpretable features extracted from Leela Chess Zero's residual stream via sparse autoencoders, then labelled by reading the top-activating positions.
Where does this pattern appear?
In 3 tagged puzzles (0.0% of the set), spanning Lichess ELO 1941 to 1941 with a median of 1941.
How do I train it?
Open the Climbchess trainer and filter for puzzles tagged with this concept. The trainer adapts difficulty using your live recognition profile and tracks how often you spot the cue versus miss it.
Is it free?
Yes. Climbchess is free forever, with no account, email, or signup required. You can delete your data at any time.