Unchained Podcast Episode 966 Summary

Title: Cheaper Fees and No More Free Lunch for Layer 2s? Inside Ethereum's Fusaka Upgrade
Date: December 3, 2025
Host: Christine Kim (Guest hosting for Laura Shin)
Guest: Preston Van Loon (Co-founder, Prismatic Labs; Core Developer, Ethereum / Prism Client)

Episode Overview

This episode dives deep into Ethereum’s upcoming “Fusaka” network upgrade, with a spotlight on how it impacts Layer 2s (L2s), data scaling, and the Ethereum developer and node operator communities. Host Christine Kim interviews Preston Van Loon, an Ethereum core dev at Prismatic Labs, about Fusaka’s new features, the technicalities behind the upgrade, practical implications for L2s, and how the pace of Ethereum development is accelerating.

Key Discussion Points & Insights

Fusaka: The Big Picture

• Major Focus: Scaling Ethereum’s data availability for L2s via blobs and the new PeerDAS (Data Availability Sampling) mechanism.
• Upgrade Scope: Around 12 EIPs (Ethereum Improvement Proposals), containing both maintenance and innovative scaling improvements.
• Momentum: It’s a milestone year—Ethereum is rolling out 2 (arguably 3) network upgrades in a single year, indicating increasing confidence and rhythm among core dev teams.

“Historically, we’ve moved quite slow by design, right? There’s just a lot of moving parts here. And the fact that we can get two [upgrades] in one year is really impressive.”
—Preston Van Loon (01:07)

Main Features of Fusaka

• PeerDAS (One-Dimensional DAS):
  • Improves blob data storage by enabling validators to retain only a fraction of blob data, using erasure coding (like in old CD players).
  • Immediate Impact: Reduced resource burden for node operators while maintaining security and data recoverability.
  • Incremental Blob Scaling:
    • Dec 3rd (Fusaka Fork): No immediate blob count increase.
    • Dec 9th: Parameter-only fork—targets up to 10 blobs/block.
    • Jan 7th: Further increased to a max of 21 blobs/block.
  • Result: More capacity for L2s, setting up for even lower fees and more scalability.

“Node operators... are storing less data and achieving the same goal. That’s a huge win. But right away, we can take advantage of that—say, well, now let’s increase the target blob count and the max blob count...”
—Preston (07:43)

• L1 Gas Limit Increase:
  • Default moves from 45 million to 60 million, lowering mainnet fees further (already observed pre-upgrade).
• New Precompile for Passkeys:
  • Allows hardware-backed authentication via phone biometrics, vastly enhancing wallet UX.

“If you have a phone... now you do [have a hardware wallet] because there’s a cryptography chip in there where you have your private key baked into the phone.”
—Preston (16:07)

What’s Still Missing?

• Not Full DAS (Proto-Danksharding Vision):
  • Current update is a stepping stone; multi-dimensional DAS enabling hundreds of blobs/block is future work.
• Backfilling Feature:
  • For L2s syncing new nodes and storing blob history, a “backfill” mechanism (retrieving historical blob data) is essential.
  • Prism client’s implementation is imminent (v7.1); other clients to follow.

“Backfill... is a really important feature that will allow nodes to retrieve data from blobs if they accidentally go out of sync with the network.”
—Christine (26:42)

Impact on Layer 2s

• Lower Fees, Higher Capacity:
  • L2s can post more data for less, further reducing user costs.

“Fees will go even lower, I imagine, which is kind of hard to imagine because fees are so low right now.”
—Preston (08:22)

• No More ‘Free Lunch’:
  • Blob minimum fees are set to at least cover node execution costs—blobs are no longer (nearly) free for L2s.

“The narrative of like L2s eating the L1s at lunch kind of goes away a little bit because... at least they're going to be paying for what they're using, which is fair.”
—Preston (20:42)

• Transaction Gas Limits:
  • New 30 million per-transaction gas cap could require L2s to tweak batching or settlement methods (unlikely to affect most users).
• Deterministic Proposer Lookahead:
  • Makes it easier for L2 sequencers to coordinate with L1 block producers, enabling potential cross-chain batch operations.

L2 Operator Challenges

• Breaking Changes:
  • L2s must keep up with new transaction formats (e.g. KZG proofs, blob handling); testnets provided a >1 month heads-up.
• Unexpected Changes:
  • Some L2s expressed concern over new blob transaction limits or client behavior changes. Core devs believe most major L2s are well-prepared.

“If you haven’t been running your chain in a testnet for the last six weeks then maybe you don’t know, but people should know by now.”
—Preston (24:51)

Developer & Client Team Experience

• Pace of Upgrades:
  • Shipping 2–3 major forks in a year is a historic achievement.
• Client Diversity & Readiness:
  • Some smaller clients had to rush out last-minute releases; discussion about possible risks to diversity if upgrade cycles get too tight.

“I feel a lot of pressure about being left behind... if people are like, ‘let’s just leave [a minority client] and see what happens’... that’s just a terrible feeling.”
—Preston (38:09)

• Internal Developer Organization:
  • Prism team uses A/B workstreams to parallelize work on consecutive forks.

Memorable Quotes & Moments

• “Now that hardware [your phone] can sign Ethereum transactions natively. That's huge. Like that's going to unlock... sign your transaction with your face, your Face ID.”
  —Preston Van Loon (16:07)

• “The more updates I see from [ETH Panda Ops], I feel really good that... our client is working well with other clients and they're testing it and they're giving us feedback constantly.”
  —Preston (44:30)

• “Usually these events, the upgrade is very boring because nothing happens and that's the way it's supposed to be.”
  —Preston (45:42)

Timestamps: Important Segments

• 01:07 — Accelerating dev cycle, two major upgrades in a year
• 03:44 — Fusaka’s headline EIPs and blob scaling
• 07:43 — PeerDAS, erasure coding, and direct user benefits
• 08:22/09:50 — Gas limit increases; immediate effects on network fees
• 10:45–13:07 — Incremental blob parameter upgrades and developer approach
• 16:00 — Passkey precompile/UX improvement
• 17:10–21:22 — L2-specific EIPs: gas caps, proposer lookahead, fair blob pricing
• 22:41–24:51 — L2 upgrade-readiness and testnet lessons
• 26:42–31:32 — Backfill and ‘semi-super node’ flag for historical blob retention
• 32:23–33:59 — Upgrade timing stress vs. ecosystem scaling need
• 35:35–38:52 — Client diversity, pressure, and resilience under tight timelines
• 42:48–44:02 — How to watch and follow the Fusaka upgrade
• 44:30–45:42 — Nervousness/technical risk relative to previous upgrades
• 47:26–49:23 — What node operators and L2s should monitor post-upgrade

How to Track the Upgrade and Its Effects

• For Users & Observers:

  • Run your own node, watch live streams (Ethereum Foundation channel), or join X (Twitter) Spaces.
  • Key success signals: Network finalization, new blob transactions appearing.

• For Node Operators:

  • Monitor hardware (esp. storage) after blob capacity increases—should be manageable if already running latest software.

• For L2 Operators:

  • Ensure support for new transaction formats, test on testnets, and consider running with “semi-super node” configuration for complete backup/retrieval.

Closing Thoughts

The Fusaka upgrade is a significant evolutionary step for Ethereum, especially its Layer 2 ecosystem. It makes data availability more scalable and robust, delivers practical fee reductions, and further enables “modular blockchain” visions. At the same time, it introduces more sustainable fee structures and sharper expectations for L2s, eliminating the “free lunch” dynamic.

Ethereum’s rapid pace this year, with a record number of EIPs and network upgrades, is both a testament to improved developer processes and a challenge to client diversity and coordination. The community is moving fast, but core devs remain confident that the ecosystem is overall well-prepared.

Resources & Links (as referenced in the episode)

• Join the Fusaka upgrade livestream (link in show notes)
• EF blog post for detailed Fusaka EIPs
• Christine’s newsletter and the Ready for Merge podcast for deep dives on protocol upgrades

“Always nervous because there could be a bug hiding somewhere. But we actually do, I think, a pretty good job of finding those well in advance and keeping the bugs out. So. Feeling good.”
—Preston Van Loon (45:42)