user11144: Base: Queen first, lose (or draw) later
What is the most economical pawn endgame position where Black queens first but White wins, White pawns no higher than 4th rank on time of Black queening?
(FYI, Ke6 + 8 pawns on the 5th seem to win against Qd1+Ke1, but Ke5 + 8 on the 4th lose, trusting Stockfish)
(added so Noam can move his answer here, where it fits better. And I can post my rank 2 solution)

user11144: Not a record but even all-on-base-rank pawns can mate:
[FEN "8/8/8/4ppp1/1K2kpp1/8/p2PPP2/8 w - - 0 1"]

1.Kc4! and queening is immediate mate, f3 only delays a move.

user8860: 4th rank, 4+1 pawns:
[Title "White plays and wins"]
[FEN "8/8/8/8/kPP5/2P5/1P5p/K7 w - - 0 0"]

1. Ka2 h1=Q 2. b3#

(Also works with 3+2 pawns,
removing wPb4 or wPc4 and adding bPa5 or bPb5 respectively.
All of these are drawn with bPh2 moved to c2,
when Black answers 1 Ka2 with c1=N+!)

11144: <p>Base: <a href="https://chess.stackexchange.com/questions/40655/queen-first-lose-or-draw-later">Queen first, lose (or draw) later</a></p>
<p>What is the most economical pawn endgame position where Black queens first but White wins, White pawns no higher than 4th rank on time of Black queening?</p>
<p>(FYI, Ke6 + 8 pawns on the 5th seem to win against Qd1+Ke1, but Ke5 + 8 on the 4th lose, trusting Stockfish)</p>
<p>(added so Noam can move his answer here, where it fits better. And I can post my rank 2 solution)</p>
 11144: <p>Not a record but even all-on-base-rank pawns can mate:</p>
<pre><code>[FEN &quot;8/8/8/4ppp1/1K2kpp1/8/p2PPP2/8 w - - 0 1&quot;]
</code></pre>
<p>1.Kc4! and queening is immediate mate, f3 only delays a move.</p>
 8860: <p>4th rank, 4+1 pawns:</p>
<pre><code>[Title &quot;White plays and wins&quot;]
[FEN &quot;8/8/8/8/kPP5/2P5/1P5p/K7 w - - 0 0&quot;]

1. Ka2 h1=Q 2. b3#
</code></pre>
<p>(Also works with 3+2 pawns,
removing wPb4 or wPc4 and adding bPa5 or bPb5 respectively.
All of these are drawn with bPh2 moved to c2,
when Black answers 1 Ka2 with c1=N+!)</p>
