According to Odaily Planet Daily, the Polkadot-Kusama bridge has been launched recently, and is synchronized in real time by a permissionless relayer run by Parity. The consensus proof logic, parallel chain head proof logic, and message proof logic are all run on the BridgeHub runtime midchain, which is completely controlled by Polkadot/Kusama governance. This means that Polkadot and Kusama are currently tracking each other's chain progress and importing messages from each other in a trustless manner.
Initially, the bridge has an open "channel" serving XCM communications between the Polkadot Asset Hub and the Kusama Asset Hub. The PAH ＜＞ KAH (Polka Asset Hub ＜＞ Kusama Asset Hub) bridge channel supports basically any XCM, but currently, the PAH and KAH runtimes have been configured to only accept DOT and KSM transfers back and forth. Soon, they will also allow stablecoin transfers; and later, they will be open to any asset owner, allowing them to register assets as ForeignAssets on remote asset hubs.
