Why doesn't Avraham wait until escorting the angelic "men" out of the tent before having the conversation with Sarah about "laughing" - the pesukim (Bereishis 18:15-16) follow one after the other.
וַתְּכַחֵשׁ שָׂרָה לֵאמֹר לֹא צָחַקְתִּי כִּי יָרֵאָה וַיֹּאמֶר לֹא כִּי צָחָקְתְּ׃
Sarah lied, saying, “I did not laugh,” for she was frightened. But He replied, “You did laugh.”
וַיָּקֻמוּ מִשָּׁם הָאֲנָשִׁים וַיַּשְׁקִפוּ עַל־פְּנֵי סְדֹם וְאַבְרָהָם הֹלֵךְ עִמָּם לְשַׁלְּחָם׃
The men set out from there and looked down toward Sodom, Abraham walking with them to see them off.