Solana’s Transaction v1 format is now available for local testing and is expected to reach mainnet in the coming weeks. Defined by SIMD-0296 and SIMD-0385, the upgrade expands the maximum transaction size from 1,232 bytes to 4,096 bytes, adds version byte 0x81, and moves compute and loaded-account limits into a TransactionConfigMask embedded in the message. V1 removes Address Lookup Tables, changes priority-fee units from micro-lamports per compute unit to total lamports, and requires RPC callers and indexers to adopt new handling before the first v1 transactions reach mainnet. The format can be tested with Solana CLI 4.2 or later and Surfpool 1.5 or later without a testnet or devnet feature gate. As of August 24, the txv1aq4pp281K9um3tnPgkfX8UqtFT6wcVW3hNezGLL gate was inactive on testnet, devnet and mainnet, while mainnet activation was expected in a couple of weeks. Legacy and v0 transactions will remain supported.