US announces it will supply Ukraine with cluster munitions
On July 7 the US Department of Defense announced it would provide needed cluster bombs to Ukraine as a part of an 800M aid package shipment.

Ukraine deploys cluster bombs within 5 days
By July 17, there were several Telegram and Youtube news sources reporting that the Ukrainian army used HIMARS to bomb a forward Russian position in Tokmak. When Russian soldiers responded to clean up the damage, Ukrainian cluster munitions hit them. It’s unclear how many casualties this caused, but it comes less than 24 hours after the Russian defense ministry said it would escalate.
Russia takes notice
Now the Russian defense ministry says they are investigating the “shelling” of Tokmak, and if they “find cluster munitions were used, would have to respond with similar weapons”.
We don’t know if these cluster bombs were from the US (it seems unlikely), but what does seem likely is the promise of new bombs has allowed the Ukrainian military to use some of their current supply. Russia has said it will now have to escalate in response to the use of cluster bombs, but it is unclear how it intended to.