BNB Chain activated its Pasteur hard fork on BNB Smart Chain mainnet at 02:30 UTC on August 25, 2026, completing a mandatory network upgrade that tightens cross-chain bridge security, hardens validator governance, and lays groundwork for higher transaction capacity. Every node operator had to run client version 1.7.7 before the switch or lose connection to the network. A hard fork is a backward-incompatible change to a blockchain’s rules that requires all participating nodes to upgrade in coordination. Regular users and most application developers did not need to move funds or change software, according to BNB Chain’s release notes.
Key takeaways
- Pasteur went live on BSC mainnet at 02:30 UTC on August 25, 2026, bundling three proposals under meta-proposal BEP-673.
- BEP-682 blocks duplicate validators in cross-chain bridge verification; BEP-695 closes validator key-rotation gaps in staking and governance.
- BEP-675 lets block builders submit pre-executed blocks, cutting critical-path processing from 125 milliseconds to 15 milliseconds in internal tests.
- Test-environment throughput rose from 1,237 to 2,324 transactions per second, though BNB Chain says the gains are not guaranteed on live mainnet.
Published: August 25, 2026 09:30 UTC
What triggered the upgrade
Pasteur is the latest in BNB Chain’s run of scientist-named hard forks, following Pascal, Mendel, Fermi, and Maxwell. Where Maxwell mainly reduced block times, Pasteur targets security and capacity instead. The upgrade had run on the Chapel testnet since July 21, 2026, giving developers roughly five weeks of live data before mainnet activation.
The changes ship as one coordinated release under meta-proposal BEP-673. BNB Chain has said it wants to double mainnet throughput during the second half of 2026, and the system-contract changes in Pasteur are a step toward that target. Node operators were also told to remove the [Eth] EnableBAL field from their config files, or the updated client would fail to start.
How the security fixes work
The most consequential change for cross-chain users is BEP-682. A cross-chain bridge is software that moves assets or data between separate blockchains. BEP-682 changes how BSC validates blocks used for those transfers, checking that the required threshold of validator signatures approved a block before the network accepts it. The previous process did not confirm that each validator appeared only once in a submitted set, meaning a specially constructed set could theoretically count one validator’s voting power more than once. Pasteur rejects duplicate entries so the threshold reflects a genuine supermajority.
BEP-695 addresses validator key rotation. A validator is a network participant that stakes tokens to verify transactions and produce blocks. After Pasteur, an old consensus key loses its administrative authority once rotated, and pending slash penalties follow a validator to its new key rather than being shed. The proposal also blocks blacklisted addresses from using signature-based voting to bypass governance restrictions.
The capacity bet and what comes next
BEP-675 moves work off the time-sensitive block production path. Builders can submit blocks they have already executed, letting validators check the block against consensus rules, sign it, and broadcast it before completing full verification. On QANet, an internal test environment modeled on BSC’s cross-region validator setup, critical-path processing fell from 125 milliseconds to 15 milliseconds. Average block gas use climbed from 46.35 million to 84.15 million against the existing 100 million limit, and throughput rose from 1,237 to 2,324 transactions per second while the block interval held at 450 milliseconds.
BNB Chain cautioned that those numbers came from controlled testing, not live traffic, and no comparable mainnet gain is confirmed. Operators and developers will now watch whether the capacity improvements carry over. Builders that adopt the new path must run full nodes, since they produce fully executed blocks; legacy block bids remain available but give builders less time to fill each block. The upgrade lands during a firm week for the market, with Bitcoin trading near recent highs and BNB changing hands around $701. Security-focused upgrades also arrive against a backdrop of costly failures elsewhere, including recent protocol exploits that have kept validator and bridge design under scrutiny.
Frequently asked questions
What is the BNB Chain Pasteur hard fork?
Pasteur is a mandatory BNB Smart Chain upgrade activated on August 25, 2026, at 02:30 UTC. It bundles three proposals that strengthen cross-chain bridge verification, tighten validator key rules, and change how blocks are processed to allow higher transaction capacity.
Do BNB holders need to do anything?
No. Regular users and most application developers do not need to migrate funds or change software. Only node operators had to upgrade to client version 1.7.7 and adjust their configuration files before the activation time.
Will Pasteur actually double BSC throughput?
Not confirmed. Internal testing raised throughput from 1,237 to 2,324 transactions per second, but BNB Chain says those figures came from a controlled environment. Real mainnet performance will depend on live traffic and validator adoption of the new block-building path.
