According to the documentation ( data structures ), the commit round should always be greater than 0 but we are obtaining commit rounds of 0 from tendermint (v0.34.24). Since the light client's commit signature matches, it does not seem to be a question of an incorrect commit/block being sent to the light client. Moreover, the consensus spec indicates that a round value of 0 is valid.

Can the commit round indeed be zero or is there a different problem in this scenario?