How can I implement the Bayesian pairwise t-test using Stanfit object in R?

I fitted a hierarchical regression model using RStan and want to implement the pairwise t-test in a Bayesian way.
For example, my data involves 100 subjects and there are two conditions (say A, B).
I fitted a linear regression model for each condition.


, where i and j denotes the subject and the condition, respectively.
I fitted 200 Ks (100 subjects * 2 conditions) using the hierarchical model and Stan.
Therefore, I had 200 posterior distributions.
My purpose is to test whether Ks in the condition A is significantly different from Ks in the condition B.
In the classical statistics, the problem would be addressed by comparing the means of 100 Ks in the condition A with those of 100 Ks in the condition B using the pairwise t-test .
Then, what is the appropriate Bayesian way for testing the difference of Ks between the conditions and how can I implement it using Stanfit object?

Thanks in advance!

Bayesian point hypothesis testing is a fairly nuanced topic. This webpage (BEST: Bayesian estimation of groups) might be a good place to start.