AMM Overview

The Lend AMM is a concentrated-liquidity AMM that runs on top of the Jupiter Lend Liquidity Layer. This guide is for routers, aggregators, and on-chain programs that want to swap against the AMM directly. The guide is self-contained: the on-chain behaviour relevant to swaps is described here, and the SDKs mirror it. You do not need access to the program source. It covers the two paths integrators build on:

• AMM SDK: request a quote, then execute the swap from a wallet or backend using the published TypeScript SDKs.
• AMM CPI Integration: call swap_in / swap_out from your own on-chain program via cross-program invocation.
• AMM Errors: the swap-path error codes, what triggers them, and how to avoid them.

REST endpoints for quoting and building AMM swaps are coming soon.

​

How the AMM works

A Lend AMM pool trades exactly one pair of tokens, token0 and token1. Liquidity is packed into a price range around a center price, so trades near the current price get much deeper liquidity than a constant-product pool of the same size. The tokens backing a pool are Liquidity Layer positions, not tokens the pool custodies. A pool can therefore exist in three shapes: For swapping you don’t need to care which shape a pool is. The program routes across whatever sides are enabled and returns a single input/output amount. The SDK quote does the same math off-chain.

​

The two swap instructions

• swap0to1 picks direction: true trades token0 → token1, false trades token1 → token0.
• amount_out_min / amount_in_max are your slippage guards, enforced on-chain. swap_in reverts if the output is below amount_out_min; swap_out reverts if the input exceeds amount_in_max. No funds move on a revert.
• Both instructions return the computed counter-amount as a u64 (Anchor return data), so a CPI caller reads the result directly.

​

Conventions that affect integrators

• token0 / token1 are ordered by public key. token0 is the mint whose address sorts lower. This is fixed per pool; compute swap0to1 from the mints you hold, not from a fixed slot.
• All amounts are native token units (base units of that mint’s decimals) at the API edge. Internally the pool works in a common 9-decimal representation and scales back to native decimals at the boundary. Token decimals above 9 are not supported.
• Rounding always favours the pool. Exact-in floors the output; exact-out ceils the input. Quote, then guard with slippage.
• Pools are addressed by a small integer dex_id (1..=totalDexes).

​

Program addresses

​

PDAs

The AMM’s own PDAs are derived against the Lend AMM program id; the Liquidity Layer accounts a swap touches are derived against the Liquidity Layer program id. Seeds (all strings are ASCII bytes; dex_id is a little-endian u16): Token vaults are the associated token account of the Liquidity root PDA for each mint (allow-owner-off-curve). The DexMetadata account stores the pool’s address lookup table (lookup_table), which you use to keep swap transactions under the size limit. The SDK derives all of these for you.

​

How a pool sits on the Liquidity Layer

An AMM pool holds no token balances of its own. It is registered as a protocol on the Liquidity Layer, and the tokens that back it are Liquidity Layer positions:

• The collateral pool is a pair of Liquidity Layer supply positions (one for token0, one for token1). Liquidity providers deposit, and the supplied tokens earn the lending supply rate while also serving swaps.
• The debt pool is a pair of Liquidity Layer borrow positions. Borrowers draw debt against the pool, and that outstanding debt is itself the liquidity a swap trades against.

Every swap drives this CPI flow: the AMM computes amounts, then calls the Liquidity Layer to move the actual tokens and update the positions. Because the reserves are Liquidity Layer positions, they carry exchange prices (interest accrual): the AMM converts raw position amounts into current-value amounts before doing any pricing math, so a pool reflects accrued interest automatically. Details that matter when you integrate:

• Pool state lives in one Dex account per pair (seeds ["dex", dex_id]), holding the pair identity, live pricing (center_price and the oracle’s last stored prices), mode switches, range configuration, fees, and share accounting. The optional center_price_address field points at an external price source; an all-zero value means the pool prices internally. This distinction matters for the accounts a swap must pass, see external center price.
• Liquidity provider stakes are shares, not token balances. Supply shares are a proportional claim on the collateral pool’s two reserves; borrow shares are a proportional obligation against the debt pool’s two reserves. Swappers never touch shares.
• Re-entrancy lock. Every user-facing entry point takes a per-pool re_entrancy lock and releases it at the end. A second entry while locked reverts with DexAlreadyEntered (6017), so you cannot swap the same pool twice inside one instruction.
• Pausing. Admins can pause a whole pool (pause_dex) or only swaps and the rebalance step (pause_swap_and_arbitrage). Paused swaps revert with DexSwapAndArbitragePaused (6050).
• Automatic arbitrage. Every operation on a two-sided pool ends with an automatic arbitrage step that re-syncs the collateral and debt prices. It runs inside the swap instruction; you don’t invoke it.

​

Integration paths

Both paths are the same three steps: quote → guard → execute. The only difference is where the code runs.