Polygon’s proof-of-stake (PoS) chain is back online after a software glitch disrupted milestone finality and caused certain nodes to stall. The development team deployed an emergency hard fork to resolve the issue, ensuring block production and finality are now running as expected.
What Happened?
The disruption began on Wednesday when a faulty validator milestone proposal caused some Bor (block producer) and RPC nodes to diverge from the main chain. While block generation itself never stopped, many RPC services and validators were forced offline, leading to several hours of instability.
Polygon’s consensus engine, Heimdall, was identified as the source of the problem. A bug in its finality gadget delayed milestone processing, even though checkpoints to Ethereum continued every 20 minutes. This created a situation where the main chain kept producing blocks, but fast local confirmations (milestones) were stuck.
Emergency Hard Fork & Updates
To restore stability, developers rolled out updated versions of Bor (v2.2.11-beta2) and Heimdall (v0.3.1). The latter required a hard fork at 3 p.m. UTC, which deleted the faulty milestone and cleared it from node databases.
Soon after, Polygon confirmed that both milestones and checkpoints were finalizing normally again, with consensus restored across the network.
Polygon co-founder Sandeep Nailwal explained that the faulty milestone pushed some validators onto divergent forks, creating short-term instability. However, he emphasized that Ethereum checkpoints remained unaffected throughout the incident.
“Milestones provide faster local finality compared to checkpoints. The disruption was due to a faulty proposal, but fixes are now live and consensus is stable again,” Nailwal said.
Growing Pains in Scaling
Nailwal described the issue as part of Polygon’s ongoing scaling journey. “With any ambitious upgrade, there will be challenges. But each one strengthens Polygon PoS as we move toward GigaGas throughput,” he noted, highlighting upcoming upgrades focused on capacity and reliability.
Reliability Concerns & Market Impact
The outage temporarily affected exchanges, DeFi protocols, and wallets that rely on Polygon finality for deposits and withdrawals. Platforms like TokenPocket suspended transactions during the downtime, while some traders criticized the reliability of the network.
This incident comes shortly after Polygon’s Heimdall v2 upgrade, which aimed to cut finality times to just five seconds, and the July Bhilai hard fork that boosted throughput to 1,000 transactions per second. Despite such improvements, reliability concerns persist.
According to DeFiLlama, Polygon’s total value locked (TVL) has dropped sharply from its $9.43B peak in 2021 to around $1.2B today. Meanwhile, Polygon’s native POL token slipped 3.4% on the day, trading near $0.27, and remains down 30% year-to-date.
Wider Context
Interestingly, Polygon’s troubles coincided with a separate outage on Linea, another Ethereum Layer-2, where its mainnet sequencer stalled for over an hour. While Linea quickly patched its issue, developers are questioning whether there may be similarities between the two disruptions.
Both cases underscore the challenges of scaling Ethereum through sidechains and Layer-2s—networks that have become critical to the ecosystem but still face fragility under certain conditions.
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