Passed pawn endgame with king opposition and advanced pawns racing to promote.

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

SAE concept sae_9049 fires when passed pawn endgame with king opposition and advanced pawns racing to promote.. It appears in 199 of 9,950 Climbchess puzzles (2.0%), spanning ELO 667–2683 (median 1832).

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This page documents Passed pawn endgame with king opposition and…, 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:

Passed pawn endgame with king opposition and advanced pawns racing to promote.

This pattern fires in 199 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 667 to 2683, with a median rating of 1832. 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 an empty square on the first rank that is attacked by a pawn and… — similarity 0.507
• Empty squares on the back rank in an active king endgame, relevant to king… — similarity 0.409
• The feature detects an empty square on the first rank that is not attacked by… — similarity 0.165
• A pawn (either colour) on the 2nd rank near the kingside, in a position… — similarity 0.164
• Pawn on the 3rd or 4th rank (from its side) that is undefended by its own side… — similarity 0.092

Example puzzles

Below are 10 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.

• Puzzle zmHOe — ELO 667, themes: advancedPawn, crushing, endgame, side to move: Black
• Puzzle zYIUi_M — ELO 952, themes: advantage, endgame, short, side to move: White
• Puzzle x568R_F — ELO 1456, themes: endgame, hookMate, master, side to move: White
• Puzzle 01T20 — ELO 1634, themes: crushing, endgame, short, side to move: White
• Puzzle zz8PU_M — ELO 1693, themes: crushing, defensiveMove, endgame, side to move: White
• Puzzle 025ip_M — ELO 1832, themes: advancedPawn, advantage, endgame, side to move: White
• Puzzle zxm0y_F — ELO 2022, themes: advantage, endgame, long, side to move: Black
• Puzzle 00ZSu — ELO 2143, themes: advantage, endgame, rookEndgame, side to move: Black
• Puzzle G4ijX_M — ELO 2392, themes: kingsideAttack, long, mate, side to move: Black
• Puzzle zz5DR_F — ELO 2458, themes: advancedPawn, crushing, endgame, 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).