100M CU Blocks

100M CU Blocks

July 2026 • Solana Foundation

Solana is raising the maximum block size from 60M to 100M compute units (CUs), a 66% increase in block capacity. The feature is scheduled to activate on mainnet on July 29, 2026, and is already live on testnet and devnet. The upcoming change is defined in SIMD-0286, authored by Jito Labs. Compute units are how Solana measures the work a transaction performs, and the block limit caps how much work a leader can pack into a single block. Raising that cap means more transactions land in every block, which adds headroom for high-volume use cases like trading and payments without changing how applications are built.

Current mainnet traffic is largely not constrained by block execution times, which is why the network can take a substantial step up in capacity and continue to maintain today's 400ms block times. (See reduced slot times for another upcoming improvement to block times on Solana.)

Technical Details

What Changes and What Doesn't

Solana enforces several block-level limits. SIMD-0286 raises exactly one of them:

Only max block compute units, the total CUs a block can contain, increases.

Demand for Block Capacity

The 60M CU limit is being tested by real traffic. Since it was enabled on July 22, 2025, 11.2% of blocks produced have had a CU usage of 56M CUs or more. That demand is not spread evenly: it arrives in spikes, typically during volatile market moments when traders most want to land their transactions.

Roughly one block in nine has been close to full capacity over the past year. Raising the limit to 100M CUs, about a year after the 60M increase, gives Solana the ability to handle those spikes in demand rather than forcing transactions to compete for nearly full blocks at exactly the moments blockspace matters most.

More Parallel Capacity

Max writable account units, the most CUs that can write to any single account within one block, stays at 12M. With the old 60M limit, a single hot account could consume up to 20% of a block. At 100M, that same 12M cap is only 12% of the block.

This means the added capacity is parallel capacity. A congested market or popular program still hits its 12M per-account ceiling at the same point, but the block has room for far more activity on unrelated accounts alongside it. One hot spot crowds out less of everything else.

An Aggressive Step After 60M

Block limits have been rising incrementally: 50M CUs to 60M CUs via SIMD-0256, which has been live on mainnet since July 2025. SIMD-0286 is deliberately more aggressive given the tremendous performance improvements that have gone into Solana validator clients over the past year. A smaller step to 80M CUs was considered and rejected in favor of the full jump to 100M.

Activation Schedule

The change ships behind the feature gate P1BCUMpAC7V2GRBRiJCNUgpMyWZhoqt3LKo712ePqsz. It is already active on testnet (since testnet epoch 983) and devnet (since devnet epoch 1100), and sits second in the pending mainnet activation queue. Mainnet feature gates activate one per epoch, and an epoch lasts roughly two days, which puts 100M CU blocks on mainnet on July 29, 2026.

Network Readiness

Larger blocks mean more data propagated to thousands of validators every slot, so block propagation had to speed up before the limit could rise safely. The key enabler is XDP, kernel-bypass networking for validators that is available in Agave 4.0.0+ and on by default in Firedancer. More than 70% of mainnet stake has enabled XDP. Additionally, XDP will be on by default in Agave 4.2. Core engineers have determined that activating the 100M CU feature gate now is safe given widespread XDP adoption across the network. See XDP on Solana for more information on XDP and how it relates to activating 100M CUs.

Performance Considerations

Bigger blocks take longer to execute. That can slow block replay for validators and lengthen catchup times for nodes that fall behind, which is why the limit only rises once propagation and execution performance have proven headroom. Infrastructure beyond validators — RPC providers, indexers, and exchanges — should also verify their systems handle sustained 100M CU blocks, even though no data formats change.

About This Upgrade

Block capacity is one of the most direct levers on Solana throughput: more CUs per block means more transactions per second at the same slot times. This upgrade continues a deliberate progression — 50M to 60M to 100M CUs — where each step is validated against the network's real ability to produce, propagate, and replay larger blocks.

Doubling capacity from the 50M starting point, while holding per-account write limits flat, pushes the network toward more parallel workloads and gives real-world use cases like trading and payments room to grow without competing for the same blockspace.

Learn more: Solana Upgrades