Field notes
The tail fork is resisted. The sandwich is not.
MonadBFT is built so the next leader cannot throw away the block before his. That removes one way to steal a fill. It does not remove a loose minimum, a thin pool, or a gas limit you padded into a loss.
MONAF Desk · 25 October 2026 · 8 min
- Tail
- Resisted, by design
- Sandwich
- Still a loose minimum
- 1 slot
- A missed proposal
- Limit
- A loss with no attacker
Tail-fork resistance is a real property and it is easy to over-read. In a pipelined protocol the leader of the next block can sometimes discard the previous one and, with it, the order a searcher already paid to obtain. Monad’s documents list resistance to that move as a design property. A fill that was included is not supposed to vanish because the next leader wanted a different order. That is the end of the good news, not the end of the risk. The remaining risks are older than Monad and they like a fast chain.
What a fast slot changes about a sandwich
A sandwich is two orders around yours. It does not need a tail fork. It needs your minimum to be loose enough that the attacker’s move still clears, and it needs the attacker to land in the same block or the next one. A 300 millisecond slot does not make that harder for someone who is already on the network. It makes it harder for you to notice and replace the transaction. The defence is the same one as everywhere else, applied without nostalgia for a slower chain: a minimum close to the quote you actually saw, from two hosts, at the size you will trade. A minimum copied from “2 percent” because that was your Ethereum habit may be a fortune in a thin Monad pool and a nuisance in a deep one. Measure the pool. Then write the number.
The losses that do not look like MEV
A missed proposal is a hole of one slot. Your cancel does not land in a block that was not produced, and the order you meant to kill can still be alive. An oracle that updates every minute is silent for hundreds of slots and then loud in one of them. Liquidations cluster in that slot. None of this is a leader stealing the tail. All of it takes money from someone who sized their position for a chain that gave them a coffee break between blocks. And the gas limit remains a way to lose with no adversary at all. A searcher who clears 0.01 MON of edge and signs a limit that costs 0.02 MON has not been sandwiched. They have bid more than the trade. MONAF’s tape is full of that shape. Treat it as the base rate.
Ask what can still take the fill if the next leader is honest. That list is the job.