A black pawn on the 6th or 7th rank, undefended by other black pieces, and not attacked by white pieces.
SAE concept sae_20849 fires when a black pawn on the 6th or 7th rank, undefended by other black pieces, and not attacked by white pieces.. It appears in 24 of 9,950 Climbchess puzzles (0.2%), spanning ELO 679–2562 (median 884).
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This page documents A black pawn on the 6th or 7th rank, undefended…, 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:
A black pawn on the 6th or 7th rank, undefended by other black pieces, and not attacked by white pieces.
This pattern fires in 24 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 679 to 2562, with a median rating of 884. That distribution tells you whether this is a beginner cue or a master-level subtlety.
Pattern statistics
| Concept ID | sae_20849 |
|---|---|
| Puzzles where it fires | 24 |
| Min ELO | 679 |
| Median ELO | 884 |
| Max ELO | 2562 |
| Coverage | 0.24% 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 10 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.
- Puzzle zSwQP — ELO 679, themes: crushing, defensiveMove, endgame, side to move: White
- Puzzle zSwQP_M — ELO 679, themes: crushing, defensiveMove, endgame, side to move: White
- Puzzle yhoJZ_F — ELO 828, themes: crushing, endgame, pawnEndgame, side to move: White
- Puzzle uApkg_F — ELO 835, themes: crushing, endgame, pawnEndgame, side to move: Black
- Puzzle zfyRp_M — ELO 835, themes: crushing, endgame, long, side to move: Black
- Puzzle 01HXY_M — ELO 884, themes: crushing, endgame, master, side to move: White
- Puzzle zXHxU_F — ELO 1156, themes: crushing, defensiveMove, endgame, side to move: Black
- Puzzle yuAEu_M — ELO 1748, themes: crushing, defensiveMove, endgame, side to move: Black
- Puzzle zuZWg_F — ELO 2531, themes: crushing, endgame, long, side to move: White
- Puzzle zx3xf — ELO 2562, themes: crushing, defensiveMove, endgame, side to move: White
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_20849?
A black pawn on the 6th or 7th rank, undefended by other black pieces, and not attacked by white pieces. 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 24 tagged puzzles (0.2% of the set), spanning Lichess ELO 679 to 2562 with a median of 884.
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.