StableSwap Deep Dive

Deep dive on StableSwap — how low-slippage stable swaps work, what minOut/deadlines protect, and why LP risk spikes on depegs

This page expands StableSwap concepts: where low slippage comes from, how minOut and deadlines protect you, and how stable‑pool LP risk behaves under stress.

Not investment advice — DEX swaps and LP positions carry depeg, slippage, and smart contract risk.

At a glance

• StableSwap curves are designed to keep price impact low when assets stay near the same price.

• As a pool becomes imbalanced, price impact increases quickly.

• minOut is your explicit “worst acceptable outcome” guardrail.

• LP risk is not “small” just because assets are “stable”: depegs can concentrate the worse asset into LP positions.

Why StableSwap can have lower slippage (conceptual)

StableSwap pools are designed specifically for pairs where:

• both assets are expected to be worth roughly the same (e.g., stable-to-stable), and

• the pool can assume prices stay near 1:1 most of the time

Many implementations use an amplification parameter that makes the curve behave “more linear” around the balanced point.

Practical consequence:

• small trades around the peg can have lower price impact than a constant‑product AMM

• large trades, or trades when the pool is imbalanced, can still have significant slippage

minOut and slippage (worked example)

When you submit a swap, you typically include:

• the input amount

• a minimum acceptable output (minOut)

• a deadline

If the swap would output less than minOut, the transaction reverts.

Example:

• quote says you should receive 995 token out

• you set a slippage tolerance of 0.5%

A rough mental model is:

$$minOut \approx quote \times \left(1 - \frac{slippageBps}{10{,}000}\right)$$

So minOut ≈ 995 × (1 - 0.005) ≈ 990.025.

This is a rough model. Exact quoting depends on pool math, fees, and route composition.

Deadlines and why they matter

A deadline limits how long your quote is allowed to be “valid.”

Without a deadline, a transaction can sit in the mempool and be mined later under worse conditions:

• pool state changed

• price moved

• MEV/searcher activity increased

A short deadline reduces the window for stale execution, but it can increase reverts during congestion.

LP risk in stable pools (what changes during a depeg)

Stable pools behave very differently when one asset deviates from its peg.

If token A depegs downward:

• arbitrage traders swap token B into the pool to buy token A cheaply

• the pool becomes heavily weighted toward token A

• LPs end up holding more token A and less token B

That is the mechanism behind “stablecoin LP losses under depeg”: the pool composition moves toward the weaker asset.

LP exposure under depeg — two numeric examples

Illustrative numbers — Real StableSwap math is not “constant product,” and real outcomes depend on pool parameters, fees, and trade paths. These examples show the directional effect: under depeg stress, LPs can end up holding mostly the weaker asset.

Example 1 — USDHN depegs down (LP ends up holding more USDHN)

Assume a pool starts balanced:

• 1,000,000 USDHN and 1,000,000 USDT

• prices: USDHN = $1.00, USDT = $1.00

• you own 10% of the pool

So your “starting” underlying exposure is:

• 100,000 USDHN + 100,000 USDT (worth $200,000)

Now assume USDHN trades at $0.90 for a period and the pool becomes very imbalanced:

• pool ends up at 1,800,000 USDHN and 200,000 USDT (illustrative)

Your 10% share is now:

• 180,000 USDHN + 20,000 USDT

USD value at the new prices:

• 180,000 × $0.90 + 20,000 × $1.00 = $182,000

Compare to “just holding” the original tokens:

• 100,000 × $0.90 + 100,000 × $1.00 = $190,000

The gap is the cost of being forced into more of the depegged asset as the pool rebalances.

Example 2 — USDHN depegs up (LP ends up holding less USDHN)

Assume the same starting pool and 10% share, but now USDHN trades at $1.05.

If the pool becomes imbalanced in the other direction (illustrative):

• pool ends up at 200,000 USDHN and 1,800,000 USDT

Your 10% share becomes:

• 20,000 USDHN + 180,000 USDT

USD value:

• 20,000 × $1.05 + 180,000 × $1.00 = $201,000

Compare to “just holding” the original tokens:

• 100,000 × $1.05 + 100,000 × $1.00 = $205,000

Again, the pool pushes your holdings away from the asset the market is bidding up.

Practical checklist (swaps + LP)

• Prefer deep liquidity pools and official routes.

• Use realistic minOut and short deadlines.

• Start with small sizes to validate routing and token behavior.

• Only LP if you are comfortable holding either asset in the pool, especially under stress.

Next reads

• Main guide: StableSwap DEX

• Automation caveats: Zapper Guide

• Full risk framing: Risk Disclosure