Progress in the nasty divorce involving Kim Zolciak and Kroy Biermann … it appears they’ve hammered out a child custody agreement … but it’s only temporary.

The estranged couple sat down for a mediation session Tuesday last week, according to new legal docs obtained by TMZ … which resulted in a temporary custody agreement signed by Kim and Kroy.

It’s unclear what the custody agreement entails … all the docs say is they signed a deal.

Kim and Kroy have four minor children … sons KJ, Kash and Kane, plus daughter Kaia.

The ugly divorce has been dragging on for over 2 years now … but this appears to indicate some signs of progress. At one point last year, Kroy had even pushed for primary custody of all four kids.