McCoy on Nostr: Replay details via Maple AI: Here’s exactly how it works: **Before the split:** ...

Replay details via Maple AI:
Here’s exactly how it works:

**Before the split:**
Both chains share the identical blockchain history and the identical UTXO set. Your coins live at the same address, with the same txid and output index, on both the Core chain and the BIP-110 chain.

**You sign and broadcast on Core:**
You create a standard transaction spending your pre-fork UTXO to some new address. You sign it and broadcast it to the Core network. It gets mined into a Core block.

**The replay step:**
Because BIP-110 is a soft fork, a standard, valid Core transaction is *also* a valid BIP-110 transaction. The transaction format hasn’t changed. The signatures are valid. The inputs exist on both chains.

So anyone — it could be the recipient, a miner, or literally any observer — can take the raw transaction hex from the Core block (or mempool), and just re-broadcast it to the BIP-110 network. BIP-110 nodes see it and say, “Yep, that’s a valid transaction spending a valid UTXO,” and mine it into a BIP-110 block.

**The result:**
Your UTXO moves to the destination address on *both* chains simultaneously. You never intended to move it on BIP-110, but it moved anyway because the transaction was valid there too.

**Why this matters:**
If you were trying to sell your “BIP-110 coins” to an exchange while keeping your “Core coins,” the replay means both get sent to the exchange. Or if you were trying to split your coins by sending them to different addresses on each chain, replay undoes that — the same transaction executes on both sides.

**The exception:**
This only works for pre-fork UTXOs. If a UTXO was created *after* the fork on only one chain (like a coinbase reward, or a transaction spending a post-fork UTXO), it can’t be replayed because it doesn’t exist on the other chain.

That’s why, without explicit replay protection, a chain split is so messy: every pre-fork coin is entangled across both chains until you deliberately “taint” or split them using techniques like mixing with coinbase outputs or `nLocktime` tricks.