Where did you find this bug?

Gambit GUI

What operating system are you using?

macOS

What version of Gambit are you using?

16.5.0 (i.e., this is not in 16.4.0, and has been introduced with recent GUI changes).

What happened?

Load in the following game to the GUI:

EFG 2 R "Untitled Extensive Game" { "Player 1" "Player 2" }
""

c "" 1 "" { "1" 1/2 "1" 1/2 } 0
p "" 1 1 "" { "1" "1" } 0
p "" 2 1 "" { "1" "1" } 0
t "" 3 "" { -100, 100 }
t "" 1 "" { 100, -100 }
t "" 2 "" { -50, 50 }
p "" 1 1 "" { "1" "1" } 0
p "" 2 2 "" { "1" "1" } 0
t "" 4 "" { 500, -500 }
t "" 5 "" { 100, -100 }
t "" 6 "" { -50, 50 }

This is Fig 1 from https://arxiv.org/pdf/2504.09716.

Click on "Dominance" under the "Tools" menu and do one round of elimination. On 16.4 that produces:

Currently on master that produces:

Now, we are removing the Dominance toolbar for extensive games as part of issue #612, after which this bug can't be recreated in the same way, but it still may arise in other situations and so should likely be investigated nonetheless.