Harmony, the independent blockchain that launched in 2019, is shutting down its mainnet and reissuing its ONE token on Ethereum as an ERC-20 token. The network announced the decision on September 6, 2026, following a catastrophic cross-shard exploit on August 12 that forged approximately 3.01 trillion ONE tokens, representing roughly 26 percent of the total 15.01 billion ONE supply. For most token holders, the migration is straightforward; for anyone with ONE locked in DeFi protocols, liquidity pools, or multisig wallets, the deadline is urgent: all smart contract positions must be withdrawn by September 9, 2026, or they will not migrate to Ethereum and will be lost.

What Triggered Harmony's Decision to Abandon Its Own Chain?

On August 12, 2026, Harmony fell victim to an exploit that struck at the consensus layer, the deepest level of the blockchain where validators agree on the valid state of the network. The attacker exploited a flaw in cross-shard verification, a mechanism Harmony uses to split its network into parallel sub-chains called shards that settle transactions among themselves via receipts. By redeeming valid receipts multiple times, the attacker created new ONE tokens with no offsetting entry, bypassing all smart contract protections entirely.

Harmony initially attempted a rollback, rewinding the chain to block 92,730,034 on Shard 0 and block 94,978,278 on Shard 1, both timestamped at 23:25:37 UTC on August 11, 2026, just before the first confirmed forgery. This rollback discarded more than 141,000 consecutive blocks and over 109,000 regular transactions, along with several hundred staking operations. However, the scale of the attack and the team's assessment of ongoing threats led to a more drastic decision: complete shutdown.

In its announcement, Harmony stated that "the threats posed by state actors and AI agents are too great," signaling that the team views the vulnerability as part of a broader security landscape that makes operating an independent layer 1 blockchain untenable. This reasoning extends beyond the single exploit and reflects a strategic pivot away from maintaining a standalone network.

Harmony

How Will ONE Tokens Migrate to Ethereum?

Harmony plans to take a snapshot of all balances at the final block of the mainnet and distribute new ONE as an ERC-20 token on Ethereum to the same addresses. ERC-20 is the technical standard that defines how tokens are transferred and queried on Ethereum, allowing wallets and exchanges to support the token without special handling. The total supply and issuance rate will remain unchanged, and newly issued tokens will be allocated to Harmony's new venture, an AI-assisted video production initiative the team describes as a "remix economy".

For the majority of holders, the migration is passive. Anyone holding ONE in a self-custodied wallet, meaning a wallet where they control the private key or seed phrase, will be automatically credited the new ERC-20 tokens on Ethereum without any claim process, form, or redemption deadline. Harmony uses two address formats, the familiar Ethereum format beginning with "0x" and its own format with the prefix "one1"; both denote the same cryptographic key, merely encoded differently, so the same private key that controls ONE on Harmony will control the new ERC-20 token on Ethereum.

Steps to Protect Your ONE Tokens Before the Deadline

• Exit All Smart Contracts Immediately: If your ONE is deposited in a liquidity pool, a multisig wallet, a lending protocol, or any other DeFi application on Harmony, you must withdraw it to a self-custodied wallet before September 9, 2026. Smart contract positions cannot be migrated because the program code behind those addresses will not exist on Ethereum, and no one can rebuild them for you.
• Verify Your Exchange's Migration Plan: If your ONE sits on a centralized exchange, the snapshot will capture your balance and the exchange is expected to credit you the new ERC-20 token once it completes the changeover. However, do not rely on this blindly; check your exchange's announcements section for specific migration details, as deposits and withdrawals are typically suspended during the transition.
• Move Funds Before the Cut-Off Window: The final blocks will be processed on September 9, 2026, with validators allowed to shut down their nodes afterward. Reports diverge on whether September 9 or September 10 is the hard boundary, so anyone holding a position on Harmony should unwind it safely by September 8 to avoid relying on whether the chain is still producing blocks.

What Happens to DeFi Positions and Liquidity Pools?

This is where the migration creates real friction for active DeFi participants. According to Harmony's announcement, multisig safes, liquidity pools, and on-chain applications cannot be migrated. A liquidity pool is a smart contract into which multiple users deposit two tokens so others can swap between them for a fee; your share is represented by a dedicated pool token. A multisig safe is a wallet that requires multiple signatures for a payout, technically also a smart contract rather than an ordinary address.

Both structures share a critical problem: program code sits behind the address instead of a private key. When the snapshot is taken on Ethereum, that contract does not exist on the new chain, and no one can rebuild it for you. This means any ONE locked in a liquidity pool, a lending protocol like Aave or Curve, or a multisig treasury will be permanently lost unless withdrawn before the deadline. Users must go through every application in which they have ever deposited anything on Harmony and pull the holdings back to an address whose key they hold themselves.

Why Does Harmony's Shutdown Matter for DeFi?

Harmony's decision to abandon its independent blockchain and migrate to Ethereum as an ERC-20 token represents a significant shift in DeFi infrastructure strategy. The network was designed as a layer 1 blockchain, meaning it settled and secured its own transactions independently rather than attaching itself to another chain. Its shutdown underscores the operational and security challenges of maintaining a standalone blockchain, particularly when facing sophisticated attacks at the consensus layer.

For DeFi users, the migration highlights the importance of understanding where tokens are held. Balances in ordinary wallets and on exchanges are captured by the snapshot and credited automatically; DeFi positions are not. This distinction creates a hard deadline for anyone with capital deployed in protocols, and the tight window between the announcement and the cut-off leaves little room for error. The incident also reinforces the ongoing tension in DeFi between decentralization and security, as Harmony's team concluded that the risks of operating an independent chain outweighed the benefits.