Detects a white pawn on the 2nd rank that can advance to the 3rd rank, where it is attacked by exactly one white piece and no black pieces.

By Climbchess Research · 2026-05-08 · 3 min read · Updated May 8, 2026

SAE concept sae_8018 fires when detects a white pawn on the 2nd rank that can advance to the 3rd rank, where it is attacked by exactly one white piece and no black pieces.. It appears in 1 of 9,950 Climbchess puzzles (0.0%), spanning ELO 1004–1004 (median 1004).

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This page documents Detects a white pawn on the 2nd rank that can…, 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:

Detects a white pawn on the 2nd rank that can advance to the 3rd rank, where it is attacked by exactly one white piece and no black pieces.

This pattern fires in 1 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 1004 to 1004, with a median rating of 1004. That distribution tells you whether this is a beginner cue or a master-level subtlety.

Pattern statistics

Related concepts

The five concepts most often co-firing alongside this one (Jaccard similarity over the puzzle co-occurrence graph) are:

• Pawn endgame with king opposition where a central or passed pawn structure… — similarity 0.143
• A square in the central pawn structure attacked by Black with no White… — similarity 0.022
• Active king centralised in a pawn or minor-piece endgame, often deciding the… — similarity 0.004
• King active on central or near-central ranks (3rd–6th) in a king-and-pawn… — similarity 0.004
• Kings in opposition or near-opposition in a pawn endgame, with both kings… — similarity 0.002

Example puzzles

Below are 1 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.

• Puzzle zxAbw_M — ELO 1004, themes: advantage, endgame, long, 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).