Router and the refused route

Creating basket shares with cash, and why the router refuses a pool that disagrees with Slate.

Most people do not hold five stock tokens. SlateRouter creates basket shares from one cash token (USDG on mainnet, TESTUSD on testnet) by buying each constituent through a swap venue, then calling create.

function createWithCash(uint256 shares, address to, Leg[] calldata legs, uint256 maxCashIn, uint256 deadline)
    external returns (uint256 cashIn);
function fairCash(uint256 shares) external view returns (uint256 total, uint256[] memory amounts);

A pool is not a price

Before a leg counts, the router measures its effective price, the cash that actually left its balance × cash/USD ÷ tokens received, and compares it with that constituent's SlateFeed price:

|effective − SlateFeed| / SlateFeed ≤ maxDeviationBps     (300 = 3% deployed; 20% is the hard ceiling)

Outside the band, the whole creation reverts with RouteRefused(leg, effectivePrice, feedPrice). Too expensive means a manipulated or illiquid pool. Too cheap means the pool is not the stock's market: the wrong token, a dead pool, or a broken price. Either way the router will not treat it as fair. The feed price is read through latestRoundData(), so a stale or mid-split feed also stops the creation.

The refused route, on a real pool

On Robinhood Chain testnet, a third-party Uniswap v3 clone (factory 0x911b4000D3422F482F4062a913885f7b035382Df) has a TSLA/USDC pool, 0xFfEf1147c3724a19AB7328F4e361C049ba452dA9, that sells TSLA for $0.0675. Slate's TSLA price at the time was $354.11. That is 99.98% off. A router that trusts the pool fills there; Slate's refuses:

cd contracts && SLATE_FORK=1 forge test --match-test test_thirdPartyV3Pool_isRefused -vv
#   third-party pool, USD per TSLA (8 dp): 6752677
#   Slate TSLA price  (8 dp): 35411000000

Accepted routes

Mainnet, real USDG: on a fork of Robinhood Chain mainnet, the router bought 0.1 AAPL through the live AAPL/USDG pool for 32.79 USDG against 32.71 fair, inside the band. See USDG integration.
Testnet, live: one SLATE-5 share for 50.33 TESTUSD against a NAV of $49.96, through Slate's seeded Uniswap v4 pools (transaction 0xe53384ae…7d03).

Venues

Venue	For	`route`
`UniswapV4Venue`	Uniswap v4's `PoolManager` (official on Robinhood Chain testnet)	`abi.encode(uint24 fee, int24 tickSpacing, address hooks)`
`UniswapV3Venue`	`SwapRouter02` (the official one on Robinhood Chain mainnet, for the stock/USDG pools)	`abi.encode(uint24 fee)`

The router never trusts a venue's return value: cash spent and tokens received are measured by balance. Leftover cash is refunded, and the router holds nothing between calls (fuzz-tested).

Testnet pools have no arbitrageurs. Left alone, a pool keeps its seed price while the market moves, and the router would (rightly) refuse it. Slate's publisher recenters the testnet pools to the Slate price through SlateV4Seeder.recenter. It acts as the missing arbitrageur, and it is labelled as testnet-only.