⏳ Pendle Internals

How Pendle works in 90 seconds

Pendle's job is to take any yield-bearing asset and turn its principal and its yield into two separately tradable tokens. Step one is to wrap the underlying into Standardized Yield (SY), Pendle's adapter interface that normalizes anything from wstETH to sUSDe to aUSDC into a single ERC-5115 shape. Step two is to split 1 SY into 1 Principal Token (PT) and 1 Yield Token (YT) with a hard maturity date. PT is a zero-coupon claim redeemable for exactly 1 unit of the underlying on that date; YT is a strip that captures every unit of accrued yield until maturity and decays to zero at expiry. The contract enforces PT + YT = 1 underlying as an arbitrage bound, so anyone can mint or burn the pair if the combined market price drifts above or below the SY.

The AMM that quotes PT against SY is purpose-built for assets whose price is converging toward a known terminal value. Pendle uses a yield-space invariant of the form x^(1−t) + y^(1−t) = k where t is the normalized time-to-maturity factor. At long maturities the curve looks like a moderately bonded pair, but as t approaches zero the exponent collapses and the pool flattens into stableswap-like geometry, which is what lets liquidity concentrate near par on a PT that is mathematically destined to settle at 1. Liquidity providers earn swap fees plus a share of YT yield, paid out as Pendle's vePENDLE-directed emissions and bribes from protocols competing for PT-pair liquidity.

A worked example makes the split concrete. Take 1 wstETH, wrap it into 1 SY-stETH, and mint into 1 PT-stETH plus 1 YT-stETH for the 31 December 2026 maturity. If the AMM quotes PT-stETH at 0.94 stETH, the implied fixed yield from today (assuming 250 days to maturity) is ((1/0.94)^(365/250) − 1) ≈ 9.4% APY locked in. Sell the PT and you have collected fixed income; sell the YT and you have given up future Lido rebase plus restaking yield in exchange for cash now; hold the YT and you are levered long stETH yield until expiry. Each of those three trades is a different bet expressed against the same SY.

Key concepts

Standardized Yield (SY)

SY is Pendle's adapter contract — an ERC-5115 wrapper that exposes any yield-bearing asset through a single deposit/redeem interface. wstETH, sUSDe, aUSDC, GLP, and points-bearing LRTs all sit behind SY adapters with identical mint and split semantics. Without SY, Pendle would need a bespoke contract per integration; with it, every new asset only needs a small adapter and inherits the entire PT/YT/AMM stack.

Principal Token (PT)

PT is a zero-coupon token redeemable for 1 unit of the underlying SY at maturity. It trades at a discount to its terminal value, and the implied fixed yield is APY = (1 / PT_price)^(365 / days_to_maturity) − 1. PT carries no rate-decay exposure once held to maturity, but it does inherit every risk of the underlying SY — depegs, slashing, withdrawal pauses — so PT-stETH at 0.94 is a fixed-income claim on stETH, not on ETH directly.

Yield Token (YT)

YT is the residual — every unit of yield the SY produces between mint and maturity. Its mark price decays toward zero on the maturity date because it has no claim on principal. YT is the levered way to express a view on yield: a small dollar amount of YT controls the entire yield stream of much larger underlying notional, so its return is roughly (realized_yield − implied_yield_at_purchase) over the holding period, levered by 1 / (1 − PT_price).

PT + YT = 1 underlying invariant

Pendle's mint and redeem functions guarantee that 1 PT plus 1 YT can always be combined back into 1 SY, and 1 SY can always be split into 1 PT plus 1 YT. That arbitrage bound pins the combined market price of a matched PT and YT pair to the underlying. Any deviation lets a flash-loan arbitrageur mint, sell, or buy the cheap leg and close the gap, which is what keeps the implied-yield curve well-behaved without an external market maker.

Yield-space AMM

Pendle's AMM uses an invariant of the form x^(1−t) + y^(1−t) = k where t is the normalized time-to-maturity factor. The exponent collapses toward zero as the market approaches expiry, flattening the curve into stableswap-like geometry around par. This concentrates LP capital exactly where PT trades most often and is the structural reason Pendle pools quote tighter spreads than a generic Uniswap V3 range as maturity approaches.

vePENDLE governance

PENDLE holders can lock for vePENDLE to vote on weekly emissions to specific PT-SY pools, exactly mirroring the ve(3,3) flywheel pioneered by Curve. Protocols launching new PT markets bribe vePENDLE voters to direct emissions toward their pool, which is why most stablecoin-yield and LRT markets on Pendle today have meaningful third-party bribe markets layered on top of native swap fees.

Why Pendle matters

As of April 2026, Pendle is the dominant fixed-income venue in DeFi, with markets live on Ethereum, Arbitrum, BNB Chain, Optimism, Mantle, Base, and Berachain across stablecoin yields (sUSDe, sDAI, aUSDC), liquid staking (stETH, weETH, rETH), restaking and points-bearing LRTs, and a tail of niche assets like GLP. The protocol's implied-yield curve has become a primary reference rate for DeFi fixed income — treasuries, structured products, and basis-trading desks all price duration off Pendle's PT discounts rather than synthesizing zero-coupon bonds themselves. That is a meaningful upgrade over the pre-Pendle era when fixed yields had to be assembled from bespoke options or off-chain agreements.

The deeper architectural contribution is showing that yield itself is tradable as a separate asset. Once the PT/YT split exists, every leveraged yield bet collapses into a YT trade and every fixed-income claim collapses into a PT trade, both routed through one AMM. That re-decomposition is what lets Ethena, Etherfi, Renzo, and the other points-and-yield markets attach Pendle as a hedging venue rather than building bespoke fixed-rate products in-house. The same primitive is now being copied for non-EVM chains (Berachain LSTs, Solana SPL-yield wrappers), which suggests yield tokenization is becoming a standard piece of DeFi infrastructure rather than a single-protocol experiment.

Frequently asked questions

What exactly does Pendle split a yield-bearing token into?

Pendle wraps any yield-bearing asset — stETH, sUSDe, aUSDC, GMX's GLP, even LP receipt tokens — into a Standardized Yield (SY) container, then splits 1 SY into 1 Principal Token (PT) and 1 Yield Token (YT) with a fixed maturity date. The PT is redeemable for exactly 1 unit of the underlying at maturity; the YT collects every unit of accrued yield until maturity and decays to zero on expiry. The protocol enforces PT + YT = 1 underlying so arbitrage keeps the two halves' combined price pinned to the SY.

Walk me through splitting an LST like stETH into PT and YT

Take 1 wstETH, wrap into 1 SY-stETH inside Pendle, then call mint to receive 1 PT-stETH plus 1 YT-stETH for a chosen maturity, say 31 December 2026. PT-stETH is now a zero-coupon bond redeemable for 1 stETH on that date; if you sell it for 0.94 stETH today you have locked in roughly 7-ish% annualized fixed yield, depending on time-to-maturity. YT-stETH keeps streaming the daily Lido rebase plus any restaking rewards your SY wrapper captures, but its mark price decays to zero by 31 December because it has no claim on principal.

How does Pendle's AMM handle the fact that PT keeps drifting toward 1?

Pendle's AMM uses a yield-space invariant of the form x^(1−t) + y^(1−t) = k, where t is the normalized time-to-maturity factor. When the market is far from expiry the curve looks like a moderately curved bonded-pair pool; as t → 0 near maturity the exponent collapses and the curve flattens into stableswap-like territory, concentrating liquidity around par. That is what lets a market-maker quote tight spreads on a PT that is mathematically guaranteed to settle at exactly 1 underlying.

Who buys PT vs YT and why?

PT buyers are fixed-income investors. They pay a discount today and lock in the implied yield no matter what the floating rate does — useful for stablecoin treasuries, structured products, and anyone who wants no-decay duration without options. YT buyers are leveraged-yield speculators: a small amount of capital buys exposure to the entire yield stream of much larger underlying notional, so YT is the levered way to bet that an asset's APY will rise (or to short yield by minting and selling). The same maturity therefore has both a yield-producer and a yield-consumer side, both routed through one AMM.

What does the implied yield number on Pendle's UI mean?

Implied yield is the annualized fixed rate you lock in by buying PT at the current market price and holding to maturity. The standard formula is APY = (1 / PT_price)^(365 / days_to_maturity) − 1. So a PT trading at 0.97 with 120 days to maturity implies ((1 / 0.97)^(365/120) − 1) ≈ 9.7% APY. The same formula run against a long-dated PT can imply a very different yield than a near-dated one on the same underlying — that gap is the term structure Pendle markets exposes.

Is buying PT actually risk-free?

PT has no impermanent loss and no rate-decay exposure once you hold it, but it carries every risk of the underlying SY plus Pendle's own contract risk. If stETH depegs, slashes, or pauses withdrawals, PT-stETH inherits the loss. If the underlying yield source (e.g., a restaking AVS or a money-market collateral) is exploited, the SY backing PT can become worth less than 1 underlying at maturity. Pendle's redemption is at most max(SY_actual, 0), not a hard guarantee of 1 unit of nominal asset.

How big is Pendle as of April 2026 and where does it run?

As of April 2026, Pendle is the dominant on-chain yield-tokenization market with deployments on Ethereum, Arbitrum, BNB Chain, Optimism, Mantle, Base, and Berachain. Markets routinely exist for stETH, weETH, sUSDe, sDAI, GLP, plus a long tail of restaking and points-bearing tokens. Most flow concentrates in stablecoin-yield and LST/LRT markets, where the implied yield curve has become a primary reference rate for fixed-income style allocations across DeFi.

Related reading

• Yield tokenization — walk through SY wrapping, the PT/YT mint, and the arbitrage bound that keeps PT + YT = 1 underlying.
• Fixed yield trading — see how to compute implied yield from a PT discount and how to compare maturities along the same SY's curve.
• Pendle's yield-space AMM — work through x^(1−t) + y^(1−t) = k, time-to-maturity decay, and why the curve flattens near expiry.
• Lido and stETH — the canonical SY underlying for PT-stETH and the source of the Consensus Layer rebase that YT-stETH harvests.
• Yield farming primitives — for context on swap fees, LP math, and how Pendle LP positions sit alongside other yield strategies.