Agave 4.2: Transaction V1 Breaking Changes Checklist

Agave 4.2 was released on 11 August 2026, but it did not activate until epoch 1031 on 10 September 2026. This update raises the maximum transaction size to 4,096 bytes and introduces a new format that older client libraries cannot read. Only one change in this update throws an error; the rest allow the code to continue running while reporting incorrect values.

Several changes in Agave 4.2 require updates to code. First, all calls that return transactions should request version 1. Failure to do so results in an error code -32015. To fix this, set maxSupportedTransactionVersion: 1 on all calls. Second, the priority fee should be read from the transactionConfig object instead of looking for a ComputeBudget instruction, as v1 transactions do not have this instruction.

Third, accounts that were locked for writing but not changed will no longer send updates. Treat the missing update as the account not changing rather than an error. Fourth, add the new reward type DeactivatedStake to the list of accepted reward types. Fifth, handle changes in Token-2022 instructions and mint extensions, as some fields have been removed or have different formats. Finally, remove hardcoded slot times from timing logic, as they have changed to 350ms and 300ms.