AUTUMN 2026 // WEEK 02

The Winning Move

White to move and win. The tactical defense mainframe detected an adversary sacrifice trap on the c-file. Circumvent the deadlock and enter White's winning move in standard algebraic notation.

SYSTEM // MAINFRAME-1895STATUS // EVALUATION LOCK Closes September 21, 2026 at 00:00 UTC

Tactical endgame radar: White king on c2 and pawn on c7 vs Black king on a1 and rook on d4. Threat vector active on c-file; White to move.

MAINFRAME TELEMETRY // CORE REGISTER DUMP

SYSTEM 1895 · STATE // ADVERSARY DEADLOCK SINK

FEN RECORD: 8/2P5/8/8/3r4/8/2K5/k7 w - - 0 1

WP [c7] 0x0004000000000000

WK [c2] 0x0000000000000400

BR [d4] 0x0000000008000000

BK [a1] 0x0000000000000001

CRITICAL HAZARD // ADVERSARY SACRIFICE LOCK

Adversary rook is positioned to initiate a forced sacrifice on square c4. Standard high-value promotion (c8=Q) triggers an irreversible concurrency deadlock (stalemate sink):
1. c8=Q? Rc4+! 2. Qxc4 [0.00 / ZERO MOBILITY]
Identify the precise underpromotion move that circumvents the stalemate sink and forces a win.