PropAMM fills on Ethereum mainnet and PropAMM support for TEMBRI (toolbox): same-block quotes, a small spread, and flow taken from lagging AMMs

PropAMM Performance on Ethereum Mainnet

PropAMMs (maker‑controlled automated market makers) have emerged as a low‑cost, low‑latency alternative to traditional AMMs. By pushing quote state on‑chain and allowing fills to read that state within the same block, they achieve same‑block pricing, a narrow spread, and minimal adverse selection. This article distills findings from a month‑long analysis of 92,627 fills across nine Ethereum PropAMM venues, comparing their economics to centralized exchanges (CEXs) and Uniswap V3.

Same‑Block Quotes and Tiny Spreads

Three of the nine venues enforce that a maker’s quote must be stamped with the current block’s timestamp, guaranteeing that fills can only execute against an update in the same block. Across all venues, takers paid an average of 0.45 basis points (bp) per fill. Crucially, the price impact measured at +12 s, +60 s, and +300 s after the fill showed no upward drift, indicating an absence of adverse selection. In other words, the cost incurred at the fill remained stable for the rest of the observation window.

PropAMMs Track CEX Moves Faster Than Uniswap

When a CEX price moved more than 0.5 bp in the 12 seconds preceding a fill, 78.5 % of PropAMM trades moved against that shift (buying after a dip, selling after a rise). The PropAMM quote updated within the same block, while Uniswap’s price lagged behind. Consequently, PropAMMs consistently offered a better price in the direction opposite the CEX move, turning the lagging AMM into the arbitrage target.

Cost Comparison with Uniswap V3

For the same WETH‑stablecoin pairs, Uniswap V3’s 0.05 % pools incurred 5.3 bp cost for trades under $1k and 1.6 bp for $1k–$10k volumes (fees included). By contrast, PropAMMs maintained a flat ~0.45 bp cost across volume tiers and volatility terciles, demonstrating a 10‑fold reduction in fees for small trades and a modest edge for larger ones.

Flow Origin and Sandboxing

The majority of PropAMM fills originated from aggregators and arbitrage contracts that deliberately route trades through a fresh PropAMM quote before hitting a lagging AMM (e.g., Uniswap, Curve). Analysis of the Flashbots mempool showed that only 2.9 % of PropAMM fill transactions were publicly visible before block inclusion, and none were sandwiched on their PropAMM side. By contrast, public swaps on Uniswap were sandwiched in up to 27 % of $10k–$100k trades. This privacy advantage further protects takers from front‑running.

Practical Takeaways

• Same‑block pricing eliminates the latency penalty that hurts traditional AMMs.
• A 0.45 bp spread makes PropAMMs attractive for both retail and institutional traders, especially at low volumes.
• PropAMMs act as the fresh side of arbitrage loops, capturing the spread while the stale AMM absorbs the price lag.
• The privacy of fill transactions reduces sandwich attacks, a notable risk on public AMMs.

Closing Thoughts

PropAMMs demonstrate that on‑chain, maker‑controlled pricing can deliver ultra‑low spreads and robust protection against adverse selection. Their ability to mirror CEX price moves within the same block positions them as a compelling bridge between centralized liquidity and decentralized execution. As tooling like the tembri toolbox matures, we can expect broader adoption and deeper integration of PropAMMs into the Ethereum DeFi ecosystem.