Detects a corner file square (a- or h-file) targeted by a queen in a tactical middlegame combination, often a discovered attack or check.

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

SAE concept sae_442 fires when detects a corner file square (a- or h-file) targeted by a queen in a tactical middlegame combination, often a discovered attack or check.. It appears in 3 of 9,950 Climbchess puzzles (0.0%), spanning ELO 1829–1829 (median 1829).

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This page documents Detects a corner file square (a- or h-file)…, 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 corner file square (a- or h-file) targeted by a queen in a tactical middlegame combination, often a discovered attack or check.

This pattern fires in 3 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 1829 to 1829, with a median rating of 1829. 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:

• Detects white rooks on their starting squares (d1, e1, f1) in middlegame… — similarity 0.006
• A queen on a contested square with White to move, under pressure from enemy… — similarity 0.005
• Black king on g8 or f8, sheltered by kingside pawns, in a middlegame or… — similarity 0.003
• Detects a knight posted on a central or near-central square (c3–f5 region)… — similarity 0.003
• Detects a king on a square with few (0-2) friendly defenders and no enemy… — 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 zvrcX — ELO 1829, themes: advancedPawn, crushing, discoveredAttack, side to move: White
• Puzzle zvrcX_F — ELO 1829, themes: advancedPawn, crushing, discoveredAttack, side to move: Black
• Puzzle zvrcX_M — ELO 1829, themes: advancedPawn, crushing, discoveredAttack, 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).