TLDR
Some Layer 2s have already acknowledged fee changes after Ethereums Fusaka upgrade. 1) bitcoin/">BOB said it now has lower fees and higher throughput after supporting Fusaka (BOB post). 2) OP Stack chains (ethereum/">Optimism and Base) signaled lower fees as blob capacity expands (Optimism post). 3) Mantle reported lower fees on its Sepolia testnet ahead of mainnet rollout (Mantle post).
Deep Dive
1. BOB Lowered Fees
BOB explicitly stated that after Fusaka went live, it is already supporting it and highlighted lower fees + higher throughput, citing PeerDAS and higher blob targets as the enabling changes. See the BOB update for details on how extra blob capacity translates to user-level fee relief on BOB (BOB post).
BOB users should see cheaper transactions now, with capacity gains coming from the increased blob space and sampling.
2. OP Stack Chains (Optimism, Base)
Optimisms team said OP Stack chains now have more blob capacity, lower fees, and a clear path to scale, reflecting the core aim of Fusakas PeerDAS and blob parameter upgrades (Optimism post). The Ethereum team also reiterated that PeerDAS enables more blobs and is being paired with blob base-fee tuning to improve cost predictability over time (Ethereum thread).
Optimism and Base are positioned for steadily lower, more predictable L2 fees as the ecosystem adapts to PeerDAS and the blob parameter schedule.
3. Mantle And Others (Arbitrum Readiness, Short-Term Noise)
Mantle reported its Sepolia Limb upgrade under Fusaka is live, promising lower fees on the path to mainnet support (Mantle post). Arbitrum signaled that Fusaka [is] coming soon to Arbitrum, but did not publish a specific fee change yet (Arbitrum post). Note that right after activation, blob base fees initially spiked as the new reserve-price mechanism took effect, with community observers noting sharply higher blob fees before capacity step-ups (BPOs) and tuning bring stabilization (market recap).
Expect fee paths to vary by chain. Some L2s may show immediate cuts, while others stabilize over days as parameters and rollup infrastructure adapt to the new blob market.
Conclusion
Right now, on-record fee changes are clearest on BOB, with OP Stack chains indicating lower fees as PeerDAS capacity ramps and Mantle showing testnet reductions. Arbitrum has signaled readiness but not a specific fee post yet. As blob parameters increase in the coming weeks, fees should trend lower across many L2s, though short-term variability is possible while each chain tunes its setup.
Confidence: moderate because most confirmations are project posts and the full impact depends on rollup adaptations and scheduled blob capacity increases.
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