> ## Documentation Index
> Fetch the complete documentation index at: https://berachain-422fce37-mintlify-1066267a.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Osaka1 Upgrade

> Validator and developer changes from the Osaka1 upgrade on Berachain Mainnet & Bepolia.

Osaka1 is a Berachain execution-layer hardfork that floors the **minimum base fee** and **minimum blob base fee** at **1 gwei** each after activation.

## Upgrade timing

| Network         | Activation Date (UTC)      | Binaries Available |
| --------------- | -------------------------- | ------------------ |
| Bepolia Testnet | 4pm / 16:00 July 22, 2026  | July 14            |
| Mainnet         | 4pm / 16:00 August 5, 2026 | July 29            |

## What changes

After the fork activates, Bera-Reth enforces configurable floors on the two EIP-1559 fee parameters:

* **Minimum base fee:** `1 gwei` (`1_000_000_000` wei). The next-block base fee can no longer decay below this value.
* **Minimum blob base fee:** `1 gwei` (`1_000_000_000` wei). The EIP-4844 blob base fee is lifted to this floor, shifting the entire exponential curve baseline.

Osaka1 is carried in the built-in `--chain bepolia` and `--chain mainnet` presets shipped with Bera-Reth v1.4.4. The Berachain genesis `berachain.osaka1` block for Mainnet is:

```json theme={null}
"osaka1": {
  "time": 1785945600,                 # 2026-08-05 16:00:00 UTC
  "minimumBaseFeeWei": 1000000000,
  "minimumBlobBaseFeeWei": 1000000000
}
```

## Upgrade instructions

1. Download the [recommended versions](/nodes/architecture/evm-execution) for your chain.
2. If you use the built-in chain preset, no genesis file change is needed:
   1. Mainnet
      1. `--chain mainnet`
   2. Bepolia
      1. `--chain bepolia`.
3. If you use `--chain <path>`, fetch the genesis files for each respective chain:
   1. Mainnet
      1. [Mainnet genesis from Beacon Kit main branch](https://raw.githubusercontent.com/berachain/beacon-kit/2059e2abea2a42513a0617a38cd7f758d1a1e6a1/testing/networks/80094/eth-genesis.json) and overwrite your current genesis file.
      2. Verify the md5: `d367b133f368367c3e973636ad059c79`.
   2. Bepolia
      1. [Bepolia genesis from Beacon Kit v1.4.2-rc.0](https://raw.githubusercontent.com/berachain/beacon-kit/refs/tags/v1.4.2-rc.0/testing/networks/80069/eth-genesis.json) and overwrite your current genesis file.
      2. Verify the md5: `f7d31d1039b0253f5f43336e55d28054`.
4. No changes are needed to BeaconKit options.
5. Start the new `beacond` and `bera-reth` binaries.