The feature detects a king on the target square that is attacked by at least one enemy piece and not defended by any friendly pieces.

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

SAE concept sae_16412 fires when the feature detects a king on the target square that is attacked by at least one enemy piece and not defended by any friendly pieces.. It appears in 5 of 9,950 Climbchess puzzles (0.1%), spanning ELO 1529–2309 (median 2309).

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This page documents The feature detects a king on the target 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 a king on the target square that is attacked by at least one enemy piece and not defended by any friendly pieces.

This pattern fires in 5 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 1529 to 2309, with a median rating of 2309. 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:

• polysemantic — similarity 0.057
• Detects an active black bishop in an endgame, typically on a central or… — similarity 0.017
• A black rook or queen is actively placed on the 7th or 8th rank, exerting… — similarity 0.015
• A black bishop defended by at least one black piece, not attacked by white, on… — similarity 0.008
• Detects a king on the back rank in a position with active mating threats from… — similarity 0.007

Example puzzles

Below are 5 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.

• Puzzle 01kWV — ELO 1529, themes: advantage, deflection, endgame, side to move: Black
• Puzzle 01kWV_F — ELO 1529, themes: advantage, deflection, endgame, side to move: White
• Puzzle zgDHX — ELO 2309, themes: discoveredAttack, discoveredCheck, endgame, side to move: White
• Puzzle zgDHX_F — ELO 2309, themes: discoveredAttack, discoveredCheck, endgame, side to move: Black
• Puzzle zgDHX_M — ELO 2309, themes: discoveredAttack, discoveredCheck, 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).