White piece activity on a contested square in an endgame or simplified middlegame where a tactical capture or outpost is available.

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

SAE concept sae_18158 fires when white piece activity on a contested square in an endgame or simplified middlegame where a tactical capture or outpost is available.. It appears in 3 of 9,950 Climbchess puzzles (0.0%), spanning ELO 815–1418 (median 815).

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This page documents White piece activity on a contested square in an…, 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:

White piece activity on a contested square in an endgame or simplified middlegame where a tactical capture or outpost is available.

This pattern fires in 3 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 815 to 1418, with a median rating of 815. 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:

• A white rook is active on an open file or rank, threatening or delivering a… — similarity 0.007
• White has a piece exerting uncontested control over advanced territory, often… — similarity 0.003
• King on rank 2 or 7 in a simplified endgame, often with passed pawns or mating… — similarity 0.003
• King in an endgame position with no immediate threats, spanning pure pawn… — similarity 0.003
• Detects a king on the back rank in a position with active mating threats from… — similarity 0.002

Example puzzles

Below are 3 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.

• Puzzle zrGzR — ELO 815, themes: advantage, endgame, fork, side to move: Black
• Puzzle zrGzR_F — ELO 815, themes: advantage, endgame, fork, side to move: White
• Puzzle 01Xyq — ELO 1418, themes: crushing, endgame, fork, 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).