Polygon Issues Urgent Client Upgrade Notice After Austin and Kyoto Hardforks

Polygon Labs has issued an urgent client upgrade notice after the Austin and Kyoto hardforks. The company warned that any Polygon PoS node still running pre-hardfork Bor or Heimdall binaries past two specific activation heights will be out of canonical consensus. This means that these nodes must upgrade and catch up to follow the network's accepted history again.

The security review from August 27 described a client-compatibility consequence, which Polygon said it had not observed on mainnet. However, they framed the disclosed changes as proactive fixes. The company stressed that both hardforks are plain binary upgrades with no state migration or genesis change, and nodes that had not diverged require no resync.

The Austin hardfork addressed two client risks: capping gas consumed while Bor processes state-sync events from L1-to-L2 bridge deposits, and removing the TxDependency extra-data field to prevent a block producer from crashing peers with an oversized data field. The Kyoto hardfork targeted deeply nested google.protobuf.Any messages, among other changes.

Polygon emphasized that operators already past the relevant height on an older client should install the applicable release, roll back to a pre-hardfork point if needed, and resync under their guidance. The company's Heimdall release notice dates the mainnet activation of Kyoto to August 18 at 10:10:31 UTC.