{
  "id": 6502645,
  "title": "Agave 4.2: Transaction V1 Breaking Changes Checklist",
  "url": "https://urgent.news/2026/09/10/agave-4-2-transaction-v1-breaking-changes-checklist",
  "topic": "tech",
  "section": "Tech",
  "published": "2026-09-10T00:02:52.000Z",
  "source": {
    "name": "Dev.to",
    "slug": "dev-to",
    "url": "https://dev.to/orbitflarerpc/agave-42-transaction-v1-breaking-changes-checklist-50h"
  },
  "original_language": "en",
  "account": "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.\n\nSeveral 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.",
  "summary": "Transaction V1 activates on Solana mainnet on 10 September 2026, at the next epoch boundary. It raises the maximum transaction size from 1,232 bytes to 4,096 bytes, and it uses a new format that older client libraries cannot read. Only one item on this list throws an error. The rest let your code keep running while it reports the wrong numbers. Where each change stands Change SIMD Status…",
  "key_points": [
    "Agave 4.2 released on 11 August 2026, activated on 10 September 2026",
    "Transaction size increased to 4,096 bytes, new format incompatible with older clients"
  ],
  "editors_take": "The Agave 4.2 update requires developers to make targeted code changes to handle new transaction formats, reward types, and instruction changes, or risk errors and incorrect values.",
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}