Solana’s 350ms Mainnet target is set to take effect in epoch 1020, down from the current 400-millisecond target slot time. The feature activated at the start of epoch 1019, but a one-epoch delay means the network keeps its existing parameters until the next epoch. In practical terms, blocks get a shorter target production interval without receiving a larger compute allowance per second.
The rollout is already further ahead elsewhere. Testnet is at an effective 200ms target, while Devnet is at 300ms and has activated its 250ms gate without making it effective yet. Solana’s Aug. 6 changelog had listed only the 350ms step on the two test clusters, showing how quickly the later stages have advanced.
Mainnet’s 350ms feature account activated at slot 440,208,000, the first slot of epoch 1019. Under the delay in SIMD-0525, Mainnet stays at an effective 400ms target through that epoch and shifts to 350ms in epoch 1020.
SIMD-0525 remains a draft. Feature activation shows that a specific cluster change is moving through the network, not that the full 200ms design has become an accepted final standard. The figures are also target timings, which are distinct from observed block production, confirmation latency and economic finality.
The arithmetic keeps the compute ceiling flat
The proposal’s defining constraint is that less work fits into each slot as slots get shorter.
Solana’s July 30 changelog reported that Mainnet had already activated a maximum block limit of 100 million compute units. SIMD-0525 shows how that 400ms maximum would compose with the slot-time stages: 87.5 million CUs at 350ms, 75 million at 300ms, 62.5 million at 250ms and 50 million at 200ms.
Each row works out to approximately 250 million CUs of theoretical maximum block budget per second. Halving the target slot time therefore leaves the example’s block-compute ceiling roughly unchanged.
That ceiling is not a transaction-throughput forecast. Actual use depends on workload and network conditions, and the 100 million figure is a composition example for maximum block CUs rather than a universal baseline for every limit.
The proposal separately reduces per-slot account-write, vote,>0.8 SOL daily target. The available evidence does not establish that VAT collection is active on any cluster.
For Mainnet, the immediate change is 350ms in epoch 1020, not a jump straight to 200ms. Solana is trying to rotate scheduling opportunities sooner while keeping resource ceilings roughly constant. The remaining risk is whether validators and surrounding infrastructure can preserve their coordination margins as each stage shortens.
