Solana Mainnet Upgrade: Block Time to Be Reduced to 350 Milliseconds

Solana core developer and Anza CEO Brennan Watt announced in a post that Solana is rolling out its first slot time reduction upgrade on the mainnet, which is expected to lower block generation time from the current ~400 milliseconds to 350 milliseconds, with the adjustment set to take effect starting at Epoch 1020. Watt cautioned developers about transition issues linked to the upgrade, noting that some SDK constants—including DEFAULT_MS_PER_SLOT—have not yet been updated to match the new parameters. The official team will release a version containing the latest values after the feature is activated. The upgrade uses a delayed activation mechanism: the feature will enter a pending activation state at Epoch E, activate at Epoch E+1, and become fully effective at Epoch E+2. For applications that rely on SDK constants to align with the mainnet’s actual slot time, Watt advised adding adaptation logic during the transition period, such as setting function switching mechanisms based on Epoch slot boundaries, to prevent service anomalies caused by parameter changes. Long-term, Solana plans to migrate these network parameters on-chain to allow direct queries by clients. For now, the team needs to complete this upgrade, describing the process as similar to Solana’s early "tough but fast iteration" development phase. Watt also revealed that the team expects the vast majority of nodes to meet the "two-slot latency" target in most scenarios; related restrictions will be further relaxed in the upcoming Anza v4.3 update.