# Engineering Update - 2025-09-19

**URL:** https://collective.flashbots.net/t/engineering-update-2025-09-19/5280
**Category:** BuilderNet
**Created:** [September 19, 2025, 10:51am UTC](https://collective.flashbots.net/t/engineering-update-2025-09-19/5280 "2025-09-19T10:51:27Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![metachris](https://collective.flashbots.net/user_avatar/collective.flashbots.net/metachris/32/6_2.png) [@metachris](https://collective.flashbots.net/u/metachris)
#### Post date: [September 19, 2025, 10:51am UTC](https://collective.flashbots.net/t/engineering-update-2025-09-19/5280/1 "2025-09-19T10:51:27Z")

</div>

Welcome back to another issue of BuilderNet engineering updates.

This post gives an overview of what happened in the weeks leading up to September 19, 2025, and what’s up next!

# Engineering

- **Forced Azure Gen6 upgrade**

- **Azure Gen6 TDX instance performance issues**

- **Reth root hash issue causing ecosystem-wide service disruptions**

- **Refunds API**

- **Heavy Node Egress**

- **Optimistic v3**

- **Heavy ongoing work on mkosi**

- **rbuilder updates**

- **BuilderHub updates**

- **[Fusaka Ethereum Upgrade](https://ethereum.org/roadmap/fusaka/) Ready**

# Upcoming

- mkosi end-to-end testing.
- Orderflow proxy
  - Return bundle hash + uuid as well as errors.
  - Networking and multiplexing performance improvements

- Automatic transfer of coinbase funds to multisig from inside rbuilder.
- Document `refundIdentity` and `replacementNonce`
- Move rbuilder-operator as a crate to rbuilder repo
- Remove non-optimistic key
- Remove more dead code and clean up unnecessary feature flags
- Refund API
- Architecture exploration document about scaling BuilderNet to 100x the nodes.
- We are exploring:
  - Bare-metal hosting: explore running builder nodes on [OpenMetal](https://openmetal.io/) instances.
  - Allowing `eth_sendBundle` without mandatory signature
  - Pull-based refunds
  - Smarter rate limiting with quality scoring
  - Multiplexing in BuilderNet
  - Reducing the amount of outgoing data
  - L2 compatibility.

# Other Highlights

- **New forum post** : [Combined refunds](https://collective.flashbots.net/t/combined-refunds/5270)
- **Second BuilderNet Community Call**
  - Happened last week, September 10th at 4pm UTC.
  - Key topics included an (a) engineering status update, (b) engineering roadmap, and (c) a deeper conversation about redistribution and refunds.
  - [Forum post](https://collective.flashbots.net/t/buildernet-community-call-2/5222), [Recording](https://drive.google.com/file/d/1W06NZp6CNNPraELHyVr0CMiK5NzLz9h5/view)