# Finality is a budget, not a switch

URL: https://www.caijing188.com/finality-as-a-budget/
Published: 2026-10-26T15:09:39+08:00 | Updated: 2026-10-27T22:09:45+08:00
Verified: 2026-10-27

## Quick answer
Finality is a trade of time for certainty, not a binary state. Ethereum.org's directory, as of October 2026, lists 7-day exits on Base and OP Mainnet, a 45,818-block dispute window on Arbitrum, about 6.4 days, and a 3-hour minimum on ZKsync Era. An exchange credits on a confirmation count; a bridge waits for the window.

## Summary
Every chain buys a kind of certainty with a fixed amount of time, and the size of that purchase is published. Ethereum.org's October 2026 directory shows 7-day exits on Base and OP Mainnet, 45,818 blocks (about 6.4 days) on Arbitrum, and a 3-hour minimum on ZKsync Era. An exchange credits after a confirmation count because it prices reorg risk on its own book, while a bridge waits out the full window because it moves a claim. Match the clock you accept to the size you are moving.

## Key takeaways
- Ethereum.org's October 2026 directory puts Base and OP Mainnet exits at 7 days
- Arbitrum's dispute window is 45,818 blocks, about 6.4 days, in the same listing
- ZKsync Era quotes a 3-hour minimum on Ethereum.org's October 2026 listing
- A confirmation count and a challenge window answer different questions, so they are not comparable

## FAQ
Q: Is a transaction final when the exchange credits my deposit?
A: No. The credit is the exchange's own promise, issued after a confirmation count it chose, and it is backed by the venue's balance sheet rather than by the chain. The chain's own settlement arrives later, which is why a deep reorg is an exchange problem before it is a user problem, as of October 2026.
Q: Why does a bridge take days when a deposit takes minutes?
A: A bridge moves a claim, not a balance on someone's ledger, so it has to wait until that claim is enforceable. On an optimistic rollup that means waiting out the challenge window. Ethereum.org's October 2026 listing shows 7 days for Base and OP Mainnet and 45,818 blocks, about 6.4 days, for Arbitrum.
Q: Does a shorter exit mean a weaker guarantee?
A: Not necessarily, but it means a different mechanism. ZKsync Era's 3-hour minimum, per Ethereum.org in October 2026, comes from proving state rather than waiting out a challenge. What changes is what you trust: a proof that is checked, or a window in which someone is allowed to object.