The sandwich mental model does not transfer from Ethereum
On Ethereum mainnet, the retail MEV story is the public-mempool sandwich: a searcher watches your pending swap in the mempool, buys in front of it, and sells behind it. Robinhood Chain — chain id 4663, an Arbitrum-stack Ethereum L2 with mainnet live since 1 July 2026 — orders transactions first-come, first-served through its sequencer and has no public mempool, so that attack has nothing to observe. A sandwich needs to see your swap before it settles; here there is no public pending-pool to watch.
That is a different regime, not an absence of risk. The sequencer itself is a trust assumption — it decides ordering, and its behavior is not yet calibrated — and ordinary execution costs still apply in full. Routescore models Robinhood Chain without importing an Ethereum public-mempool sandwich rate; what its route check surfaces instead are the costs that are actually present — slippage against pool depth, thin liquidity, sequencer-ordering caveats, and token-registry state.
- No public mempool → the see-it-then-sandwich-it play has nothing to observe.
- First-come-first-served sequencer ordering → ordering power sits with the sequencer operator, a trust assumption rather than an open auction.
- The Ethereum sandwich rate does not belong in a Robinhood Chain model — Routescore sets that penalty near zero by construction and says so.
What can still cost you — and is checkable before you swap
Take the sandwich off the table and the remaining risks are more ordinary and easier to check. Each item below is either modeled in a Routescore route check or named as a caveat on the artifact, so a coverage gap never reads as a clean result.
- Slippage versus pool depth at your notional — thin, young liquidity means the same trade size pushes the price further than it would on a deep Ethereum pool.
- Oracle and reference-price freshness — tokenized stocks trade 24/7 onchain while their underlyings keep market hours, so the reference price a quote leans on can be hours stale.
- Sequencer-operator trust and finality — ordering and inclusion run through one operator; that is a structural assumption, named on the artifact rather than scored.
- Token authenticity — a registry-recognized token matches Routescore's address-level registry entry; an unverified one has not been confirmed. Recognition is not safety or sellability.
Modeled and uncalibrated — what the Robinhood Chain numbers mean
Routescore covers Robinhood Chain at support level modeled: route and slippage figures come from a launch-static catalog of two routes — Uniswap and 1inch — not a live on-chain feed. The modeled MEV penalty sits near zero by construction, because the chain is sequencer-ordered with no public mempool, so slippage and liquidity depth carry the result rather than a sandwich rate imported from Ethereum.
None of those figures has been reconciled against realized Robinhood Chain outcomes yet. That is what "uncalibrated" means here, and it is stated on every artifact rather than smoothed over: treat each number as a modeled, point-in-time comparison input until the calibration loop accrues real labels. A pre-sign check on this chain also carries a sequencer-ordering caveat instead of reading as clear.
For AI agents: the same answer, machine-readable
Everything above is available as a structured pre-sign read. An agent can call check_swap — REST, or the same tool in the published @routescore/mcp package — with chain_id 4663 and a notional, and get a verdict with machine-readable reasons (the schema is clear / caution / unsupported across chains; on Robinhood Chain today the result is caution or unsupported, because sequencer-ordered realized outcomes are not yet calibrated), the modeled slippage band, the token registry state, and the full trust envelope: methodology version, source freshness, and caveats included.
The boundary is the same for humans and agents: read-only, non-custodial, decision support only. Routescore never signs, submits, or moves funds — it hands over the evidence and the caveats, and the decision stays with you or your agent.