# \[Infra\] Kaia v2.1.0 MEV auction system (KIP-249) on Kairos testnet

**URL:** <https://devforum.kaia.io/t/infra-kaia-v2-1-0-mev-auction-system-kip-249-on-kairos-testnet/8983>\
**Category:** Kaia\
**Created:** [12월 4, 2025, 8:26오전 UTC](https://devforum.kaia.io/t/infra-kaia-v2-1-0-mev-auction-system-kip-249-on-kairos-testnet/8983 "2025-12-04T08:26:15Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![sean.lin](https://yyz1.discourse-cdn.com/flex035/user_avatar/devforum.kaia.io/sean.lin/32/3173_2.png) [@sean.lin](https://devforum.kaia.io/u/sean.lin)\
**Post date:** [12월 4, 2025, 8:26오전 UTC](https://devforum.kaia.io/t/infra-kaia-v2-1-0-mev-auction-system-kip-249-on-kairos-testnet/8983/1 "2025-12-04T08:26:15Z")

</div>

![20251202_MEV Article (EN)](https://canada1.discourse-cdn.com/flex035/uploads/klaytn/original/2X/e/e91c14ca00dba3de08bf21f0dbd4bd2d15b7f0ef.jpeg)

**TL;DR**  
Kaia v2.1.0 introduces an experimental **MEV auction system** (KIP-249 BidTx), now live on the **Kairos testnet** , that turns unstructured gas wars into sealed-bid auctions per block.

* * *

### What we shipped

- A new **BidTx** type that encodes the winning MEV bid for a block.

- An **auction RPC namespace** so an off-chain auction server can collect sealed bids from searchers and submit the winning BidTx to the proposer.

- Integration hooks so MEV searchers and infra partners can start wiring up their own infrastructure against Kairos.

This is currently **testnet-only** and intended for experimentation and feedback before any mainnet rollout.

* * *

### Why this matters to builders

**For searchers & infra operators**

- A clear, documented path to participate in MEV on Kaia without blind gas bidding.

- One structured, winning bundle per block, rather than many competing spam transactions.

- A more predictable interface (BidTx + auction RPC), you can build bots and services around.

**For app developers**

- A path to more predictable transaction ordering and latency for MEV-sensitive flows (DEX trades, liquidations, oracle updates, etc.).

- Better separation between “normal user flow” and MEV competition, which should help reduce surprise gas spikes over time.

* * *

**Full article (EN):** [https://medium.com/kaiachain/from-chaos-to-opportunity-94d32af4d5ee](https://medium.com/kaiachain/from-chaos-to-opportunity-94d32af4d5ee)

If you’re building searcher infra, DEXes, or indexers on Kairos and plan to experiment with the auction system, feel free to reply here with your use case or questions, and we’ll try to point you to the right docs and examples.

---

<div class="post-metadata">

**Author:** ![orange](https://yyz1.discourse-cdn.com/flex035/user_avatar/devforum.kaia.io/orange/32/3753_2.png) [@orange](https://devforum.kaia.io/u/orange)\
**Post date:** [12월 5, 2025, 8:44오전 UTC](https://devforum.kaia.io/t/infra-kaia-v2-1-0-mev-auction-system-kip-249-on-kairos-testnet/8983/2 "2025-12-05T08:44:49Z")

</div>

gKaia, excited to see how this improves efficiency moving forward 🔥

---

<div class="post-metadata">

**Author:** ![sean.lin](https://yyz1.discourse-cdn.com/flex035/user_avatar/devforum.kaia.io/sean.lin/32/3173_2.png) [@sean.lin](https://devforum.kaia.io/u/sean.lin)\
**Post date:** [12월 8, 2025, 8:00오전 UTC](https://devforum.kaia.io/t/infra-kaia-v2-1-0-mev-auction-system-kip-249-on-kairos-testnet/8983/3 "2025-12-08T08:00:02Z")

</div>

![MEV infographic](https://canada1.discourse-cdn.com/flex035/uploads/klaytn/original/2X/c/c4b729cb7c65dba42dc812875cf25475fe22fe2f.png)

**Concrete scenario:** you’re running a liquidation/arbitration bot on Kairos and want to plug into the auction instead of just spamming the public mempool.

Things to think about:  
– Use the auctioneer path for latency-sensitive bundles, and keep a normal-tx fallback for non-critical ops.  
– Model the worst-case delay between sending a BidTx and seeing the bundle executed; never assume “instant” inclusion.  
– Be explicit about which parts of your app break if your bundle loses the auction or gets reordered.

The current system is live on **Kairos testnet only** while we iterate with searchers and builders.  
Full write-up + details: [https://medium.com/kaiachain/from-chaos-to-opportunity-94d32af4d5ee](https://medium.com/kaiachain/from-chaos-to-opportunity-94d32af4d5ee)

If you’re considering building MEV-sensitive DeFi or searcher infrastructure on Kaia, drop your questions here, and we’ll group them into patterns and answers in follow-up posts.