A word/expression for this?

Is there a word or slang expression for leaving out information
until the last minute so that another party looks foolish?

“dropped a bombshell” ?
“put in his pipe”
“turned the tables”

pfft sure there is in french

Well, “sandbagging” is one. “Left me out on a limb” is another.

The word “ambush”, attack from a concealed position, is applicable.

For example, legal discovery, the process of sharing information between opposing parties in a trial, is intended to prevent “trial by ambush”.

shanghied

Blindsiding, maybe?
ie, “He blindsided me.”
Actually, “to sabotage” seems an even closer choice.
Undercutting? Backstabbing?
Some version of “setting a trap”?
(What are those forest traps called that are covered over at the top, but you fall into?)

Let’s also include the phrase: “lying by omission”.