Input Output Hong Kong (IOHK), the blockchain engineering firm behind the Cardano network, has released some “disappointing news,” announcing a one-month delay to the long-awaited Vasil upgrade.

The Vasil upgrade is set to provide a “massive performance improvement to Cardano” and its smart contract capabilities, according to Cardano co-founder Charles Hoskinson. It was previously slated to go through on June 29. However, the latest estimate is now set for the last week of July.

IOHK’s head of delivery and project Nigel Hemsley noted in a Monday blog post that the core Input Output Global (IOG) team working on the upgrade “is extremely close to finalizing the core work” but there are still seven bugs that remain outstanding and require work. None of them are categorized as “severe,” he added.

“The work on Vasil has been the most complex program of development and integration to date, from several angles. It’s a challenging process that requires not only significant work from core teams, but also close coordination across the ecosystem,” Hemsley wrote.

As a result, the Cardano Foundation — the non-profit that oversees the development of Cardano — and the IOG team agreed to defer sending the Vasil hard fork to the Cardano testnet from June 20 until June 29.

Once the testnet has been hard forked, devs from Cardanao-based decentralized applications (DApps) and stake pool operators SPOs will have roughly four weeks “to carry out any required integration and testing work” before the Vasil hard fork is initiated on the mainnet in late July:

“This is only reasonable and should not be rushed. The working assumption should therefore now be a Cardano mainnet hard fork occurring during the last week of July.”

“We recognize that this news will be disappointing to some. However, we are taking an abundance of caution to ensure that we do this deployment correctly,” Hemsley added.

The Vasil hard fork is the biggest upgrade to Cardano since the Alonzo hard fork in September, which finally enabled smart contracts on the network. This latest upgrade is set to introduce four network improvements dubbed “CIP31, CIP32, CIP33, and CIP40.”

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In theory, these upgrades are designed to reduce the size of transactions, therefore increasing the network’s throughput and lowering transaction fees on the network.

Cardano is a proof-of-stake (PoS) blockchain platform aiming to provide competition to Ethereum as a smart contract network with lower fees. It is currently ranked seventh out of all crypto assets in terms of market cap at around $16 billion.