The Avalanche network is set to activate the Helicon upgrade at 11 AM ET (3 PM UTC) on Tuesday, September 22, 2026. All Mainnet nodes must upgrade before that time to remain operational; failure to do so will result in a node shutdown. The upgrade also requires updating the node plugin to version 46, which is the only compatible version for the new core functionality.
Helicon activates a suite of Avalanche Community Proposals (ACPs) that will reshape how the network handles execution and staking. ACP‑194 introduces C‑Chain asynchronous execution, allowing transactions to be processed without waiting for immediate confirmation. ACP‑236 implements auto‑renewed staking, streamlining validator participation by automatically extending stakes when they approach expiration. Additional proposals—ACP‑267, ACP‑273, ACP‑283, and ACP‑285—raise validator uptime requirements, reduce the minimum validator staking duration, enable dynamic minimum gas prices, and lower the minimum consumption rate, respectively. These changes aim to improve network efficiency, reduce entry barriers for validators, and adapt gas pricing to real‑time demand.
Beyond the ACPs, Helicon adds a configuration option for Subnet‑EVM: the `InitialMinDelayMS` parameter can set the minimum block delay at genesis. This feature gives subnet operators finer control over block timing, potentially improving performance for specific use cases.
C‑Chain state sync will not be fully supported during the Helicon activation window. Nodes that begin state sync at the moment of activation may stall, and restarting a node mid‑sync will force a full restart from the beginning. If a node disables state sync after a partial sync, it may encounter an unrecoverable `FATAL` error. Nodes using the `firewood` state‑scheme cannot perform state sync, and new Firewood nodes on Mainnet or Fuji must set `state-sync-enabled` to `false` to avoid shutdown.
The upgrade also removes several RPC endpoints. The `avax.getAtomicTxStatus` RPC is deprecated in favor of `avax.getAtomicTx`. Namespaces such as `admin`, `warp`, and `personal` are removed, as are the `eth_accounts`, `eth_coinbase`, and `eth_etherbase` RPCs. Debug RPCs `debug_dumpBlock` and `debug_preimage` are also eliminated. Developers should update their tooling to accommodate these changes and ensure compatibility with the new API surface.
In summary, Helicon’s activation will bring significant protocol enhancements while imposing strict upgrade deadlines and temporary limitations on state sync and RPC functionality. Node operators and developers should plan their upgrade strategy accordingly to maintain network participation and application compatibility.