Zero-slippage fills: how 0x's RFQ works on herrenlos

herrenlos quotes several route providers at once and ranks them by what you'd actually receive (how swaps work here). One of those providers is 0x, the same-chain EVM specialist. The 0x on herrenlos post covers what it is and its lane in general; this one zooms in on a single, genuinely useful capability it brings — RFQ zero-slippage fills — how they surface in the app, and the honest conditions for when you'll see one.

What "RFQ" means here

Most on-chain swaps route through AMM pools, where the price you get depends on how much liquidity is in the pool at that moment — so a larger trade moves the price against you (that's slippage), and you set a tolerance for how much movement you'll accept.

RFQ — request-for-quote — works differently. Instead of quoting a pool, a professional market maker quotes you a firm price directly and commits to fill at it. 0x can source that RFQ liquidity alongside the usual AMM routes. When an RFQ quote wins, the fill is at a fixed price with no slippage — the number you agree to is the number you get, settled through 0x with MEV-protected settlement so the fill isn't sandwiched in the mempool.

How you see it in Routes

You don't have to know any of that to benefit from it. When you enter a same-chain EVM pair, herrenlos asks 0x for a quote in parallel with the other providers and ranks everything by executable output. If 0x comes back with an RFQ price, herrenlos flags that route with a "Zero Slippage · RFQ" marker, so you can see at a glance when a fixed-price fill is on offer rather than an AMM route with a slippage tolerance.

It's still just one competing line in the ranking. An RFQ route doesn't automatically win — if another provider would deliver more for your pair and size, that one is highlighted instead. The marker is information, not a thumb on the scale.

The honest conditions

RFQ zero-slippage isn't available for every trade, and it's better to be upfront about that than to imply it's always there:

• A wallet needs to be connected. Market makers quote a specific taker — so there has to be a real address to quote for. With no wallet connected, there's no RFQ price to fetch, and you'll see ordinary AMM routing.
• It's shown for the pairs where it's offered — in practice, liquid same-chain pairs (stablecoin routes are the common case) on the EVM chains herrenlos supports. Not every token or size will have an RFQ maker willing to quote.
• Same-chain EVM only. RFQ here is a 0x, same-chain feature. Cross-chain moves (Bitcoin, or chain-to-chain) go through other providers — Chainflip, LI.FI, Squid — which have their own settlement models.
• A quote is still a snapshot. An RFQ price is firm when quoted, but quotes expire and prices move; the figure you see is an estimate until you execute.

Non-custodial, the whole way

Nothing about RFQ changes the custody model. You sign in your own wallet, in-page — herrenlos never holds your funds, and there's no account or KYC. 0x execution uses Permit2: you sign a scoped EIP-712 approval and the swap transaction, both in your wallet. A same-chain swap that doesn't go through simply reverts on-chain and costs only gas.

Your keys never leave your wallet. Non-custodial isn't a mode you switch on — it's the only mode.

Try it

Open the swap page, connect a wallet, and pick a liquid same-chain EVM pair — if an RFQ maker quotes it, you'll see the zero-slippage marker on the 0x route as it's ranked against the others. For the general picture of 0x's role, see 0x on herrenlos; for how the parallel quoting and ranking work across every provider, see Swaps on herrenlos.