Curvefi metapools and access to base-pool liquidity

Shared reserves through a pool-share token

Base-pool liquidity-provider tokens, or LP tokens, package a share of pooled reserves into an asset another pool can hold and exchange. The metapool maintains its own reserves of the added token and those shares, connecting the added token to several underlying assets through a shared liquidity layer while each pool keeps separate balances and pricing rules. The outer pool can support these connections without storing every underlying coin directly. Its base-pool LP-token reserve represents only the shares it holds, so the connection does not grant ownership of the whole base pool.

Separate metapools can use the same base pool without holding one another’s added tokens. An underlying trade still encounters the balances and pricing of the pools involved. Substantial base-pool liquidity therefore does not remove constraints at the metapool level.

The registered base pool and supported interface

StableSwap-NG factory metapools require a registered base pool and a compatible pool implementation. Permissionless metapool creation operates within those supported choices. Adding a base pool to the factory registry is an administrative action, separate from deploying a metapool. Pool and token addresses establish the actual connection: the added coin, the base pool, and its LP token must match the selected deployment. A compatible helper must use that pool’s methods and coin ordering. A route available through one application therefore does not establish support in every interface.

Different generations expose different liquidity-operation signatures. A compatible router or deposit helper must support the selected pool implementation on the same network.

How does a metapool swap reach an underlying token?

An underlying swap converts between the added token and a base-pool asset using the base-pool share as the internal connection. In the added-token-to-underlying direction, the metapool exchanges the input for base-pool LP tokens. It then redeems those shares into the selected base-pool asset. The receiver obtains that underlying token when the supported combined operation succeeds.

In the reverse direction, the contract deposits the chosen base-pool asset into the base pool to obtain LP tokens, then uses those shares as input to the metapool exchange for the added token. StableSwap-NG exposes this behavior through exchange_underlying. Internal calls can complete within one transaction, so these conceptual stages do not require separate wallet transactions. Routers can also call compatible zaps for implementations that require them.

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A swap ending in shares or an underlying asset

A hypothetical metapool configuration offers only the direct share-token swap through the selected interface. The intended output is a coin its base pool contains. Which path reaches that coin? Both choices begin with the added token and target the same underlying asset.

The direct path ends with pool shares. Reaching the intended coin afterward requires a supported base-pool redemption, with its own output quote and minimum. An integrated underlying path coordinates the metapool swap and that redemption. It reaches the same asset without leaving the intermediate shares in the receiver’s wallet.

With integrated access absent from this interface, the fallback is a direct swap followed by base-pool redemption. Both operations must support the selected assets. Check the redemption quote before acquiring the shares. If redemption is unavailable, the displayed share-token swap cannot finish the intended conversion.

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A successful direct swap delivers base-pool LP tokens to the selected receiver. The completed redemption burns those shares and credits the selected underlying token to its receiver.

What do metapool liquidity tokens represent?

Metapool LP tokens represent shares of the metapool’s combined reserves, including its added token and holdings of base-pool LP tokens. In an already funded StableSwap-NG metapool, either top-level asset can supply new liquidity. Initializing an empty pool requires both. A compatible deposit zap can accept underlying base-pool coins and coordinate the needed deposit into each layer.

The metapool’s LP token is distinct from the base pool’s LP token. Each identifies a different claim on reserves. StableSwap-NG reads the base pool’s virtual price when valuing its LP-token reserve. This invariant-based accounting input relates pool value under its pricing model to the LP-token supply. A single-coin redemption amount also depends on the selected coin, pool balances, and fees.

The base-pool trading fees retained for its LPs contribute through the shares the metapool holds, while metapool trading fees arise at the outer layer and any active gauge rewards accrue separately to eligible staked positions. veCRV voting affects the allocation of eligible CRV emissions; it does not alter which assets the pool’s reserve shares represent.

Price impact across the connected pools

A quote for an underlying swap between the added token and a base-pool asset accounts for the relevant metapool exchange and base-pool deposit or redemption under their quoted conditions. Trade size and pool balances influence the final output. A deep base pool cannot compensate for every shortage in the outer pool or every shortage of the requested underlying asset.

StableSwap-NG uses an amplification parameter to shape pricing around the assets’ expected value relationship. Its dynamic fee mechanism uses rate-adjusted balances and a configured off-peg multiplier. Those parameters do not provide a fixed market price or a permanent fee for every trade. The pool’s fee and multiplier getters expose configuration values.

Minimum-output protection compares execution with an amount denominated in the final output token. A lower-than-required output makes the protected swap revert. Quotes can change before execution as reserves change. Network gas costs depend on chain conditions and the calls the route executes.

Exposure across the reserve layers

A loss of the added token’s peg can change a metapool’s reserve composition and redemption value. Metapool LPs inherit exposure to underlying base-pool assets through the base-pool shares their metapool holds. A failure in either asset layer can affect the outer position. Favorable swap pricing near an expected peg does not restore an asset’s external backing.

Base-pool providers do not directly hold the added token solely because a metapool uses their shares. Other metapools using the same base also keep their added tokens separate. Shared base-pool assets and shared infrastructure remain dependencies. A compatible zap coordinates contracts; it does not remove token-transfer restrictions, underlying-asset risks, or smart-contract failures.

Why does a metapool withdrawal return base-pool LP tokens?

A direct proportional metapool withdrawal returns base-pool LP tokens because those shares form part of the pool’s reserves. It also returns the corresponding portion of the added token. Amounts follow the current reserve proportions, including any imbalance created since the original deposit.

A single-asset metapool withdrawal into the base-pool LP token still ends in shares. An underlying-asset exit additionally needs base-pool redemption, through compatible helper logic or a supported separate operation. A minimum-output failure, an incompatible helper, or a token-transfer restriction can prevent that combined exit.

Proportional withdrawal can avoid a requested single-asset conversion when its direct reserve transfers remain functional. It does not repair a damaged underlying asset. Redeeming the returned base-pool shares remains a distinct dependency. For compatible deployments with StableSwap-NG base pools, MetaZapNG combines the metapool withdrawal with base-pool redemption.