Solana's Head of Developer Relations, Jacob Creech, recently highlighted an upcoming change that could impact certain transaction patterns on the network.

In a thread on X, Creech first asked the community: "Does anyone load nonce accounts from an Address Lookup Table today?"

He followed up by stating that this specific functionality—loading durable nonce accounts directly from an Address Lookup Table (ALT)—will be disabled once SIMD-242 activates on mainnet.

What Are Address Lookup Tables (ALTs)?

Address Lookup Tables are a Solana feature (introduced via versioned transactions) that allow transactions to reference a larger number of accounts by storing addresses in on-chain tables rather than embedding them all in the transaction itself. This helps keep transaction sizes small while supporting more complex operations.

What Are Durable Nonce Accounts?

Durable nonces are Solana's mechanism for creating "nonce" or "queued" transactions that can be submitted later without expiring immediately. A durable nonce account holds the next valid blockhash, enabling offline signing and replay protection.

Why the Change?

SIMD-242 appears to be a proposal aimed at tightening security or simplifying the runtime. Allowing nonce accounts to be loaded via ALTs may introduce edge cases or potential vulnerabilities, so the activation will enforce that nonce accounts must be passed directly in the transaction's account keys list rather than looked up from a table.

What Developers Should Do

If your application or script currently relies on including nonce accounts only through an Address Lookup Table (without listing them explicitly in the transaction's account keys), you'll need to update your code before SIMD-242 goes live on mainnet.

• Always include the nonce account in the transaction's primary account list.
• Test your changes on devnet or testnet, where the feature may already be restricted or simulatable.

This is a relatively niche change, but as Creech's question suggests, it's worth double-checking if your tooling is affected. Solana continues to evolve rapidly, and staying on top of these runtime updates helps ensure smooth operation as the network scales.

For the full SIMD-242 details, keep an eye on official Solana Foundation announcements and the proposal repository. In the meantime, if you're using durable nonces with ALTs, now's the time to audit and adjust.