Morpho Collateral vs Supply: Which Earns Interest?

In Morpho Blue, collateral does not earn the market's lending interest. Supplying the loan token creates supply shares that can gain asset value as borrowers accrue interest. A yield-bearing collateral token such as wstETH may still change its underlying conversion value, but that change comes from the token's own mechanism and does not create Morpho supply shares.

The word “supply” appears in both actions, which makes an account easy to misread. A wallet can deposit collateral, lend the loan token, or do both in the same market. Its records must show which action happened before any displayed yield can be explained.

This article follows Morpho's variable-rate Blue markets and the reference implementation at commit 8e26ca6, checked on 28 October 2026. Vault V1/V2 depositor accounting, older Morpho Optimizers and Midnight fixed-rate markets use different layers. A reference commit also does not identify the implementation or settings of a particular deployed market.

Identify the balance before attaching a yield

A Blue market specifies a loan token and a collateral token. Lenders provide the loan token that borrowers receive. Borrowers provide the collateral that secures their debt. Morpho's market-mechanics documentation describes separate market totals and a separate position for each account.

The position contains three fields: supplyShares, borrowShares and collateral. The first two are internal accounting units; collateral is recorded directly in collateral-token base units. These fields can coexist. Their names do not imply that one automatically cancels another. The pinned position interface defines each separately.

In the pinned core implementation, supply transfers the market's loan token and credits supply shares. supplyCollateral transfers its collateral token and increments the collateral field. It neither mints lending shares nor calls interest accrual.

That distinction prevents an Aave accounting rule from being carried into Blue. The Aave scaled-balance example follows an aToken claim through its income index. Blue's direct collateral record is a different object. Do not apply a lending-share conversion to it merely because both screens describe a deposit.

Follow collateral and lending through one account

Consider a hypothetical Blue market with U as its loan token and Lido Core wstETH as its collateral token. U is fictional and has six decimals; wstETH has 18. These are invented account and market observations, not live market data or an allocation recommendation.

Alice starts with no position. Other lenders have already supplied 9,000 U, represented by 9 × 10^15 raw supply shares. Use those totals after any interest accrual triggered by Alice's supply, immediately before her deposit is added. Assume the following transactions succeed, the market fee is zero, Alice is not the fee recipient, and no loss or unrelated flow occurs between the stated interest checkpoints. Alice does not borrow in this example.

First she deposits 10 wstETH through supplyCollateral. Her collateral record becomes 10 × 10^18 base units. Her supply-share record remains zero. She has supplied an asset that could secure borrowing, but she has not lent any U.

Next she supplies 1,000 U through supply. That is 1,000,000,000 U base units. This operation creates her loan-token supply position while leaving the 10 wstETH collateral record unchanged.

Calculate the lending shares with the actual constants

The pinned SharesMathLib adds 1,000,000 virtual shares and one virtual asset to the conversion. The virtual asset is one token base unit. For six-decimal U, it means 0.000001 U.

Let A denote the market's total supply assets in base units and T its total supply shares. Supplying an asset amount d creates shares rounded down:

new shares = floor(d × (T + 1,000,000) / (A + 1)).

Before Alice's supply, A is 9,000,000,000 and T is 9 × 10^15. Applying the formula to her 1,000,000,000-base-unit deposit gives exactly 10^15 new shares. Afterward, the market records 10,000 U of supply assets and 10^16 supply shares.

Converting Alice's shares back to an asset claim also rounds down:

asset claim = floor(shares × (A + 1) / (T + 1,000,000)).

At this checkpoint, that calculation returns exactly 1,000,000,000 base units, or 1,000 U. Her 10 wstETH does not enter either conversion.

Apply one stipulated interest checkpoint

Now assume a completed market accrual adds exactly 60 U of borrower interest. Total supply assets become 10,060 U. This stipulated amount has no assumed duration, APR or particular interest-rate model. There is no fee in the example, so total supply shares remain 10^16 and Alice still owns 10^15 of them.

The core accrual increases both total borrowed assets and total supplied assets; a nonzero fee can additionally create supply shares for the fee recipient. It does not increase the collateral field. This is accounting for interest on loans, rather than a new token transfer into Alice's wallet. Blue interest-accrual implementation.

Alice's new asset claim is 1,005,999,999 base units, or 1,005.999999 U. Its increase is 5.999999 U. A simple 10% share of 10,060 U would give 1,006 U; keeping the virtual constants and flooring produces the one-base-unit difference in this fixture.

The useful reconciliation is three separate facts: Alice contributed 1,000 U in cash, her unchanged supply shares now represent a larger U claim, and her collateral quantity is still 10 wstETH. Calling the whole account “10 wstETH earning the supply rate” would attribute the U interest to the wrong deposit.

A collateral token can change its own conversion value

wstETH makes the distinction visible. Lido describes Core wstETH as a wrapper whose token balance stays fixed through oracle reports while its stETH conversion value changes. Its getStETHByWstETH method returns the stETH corresponding to a specified wstETH amount. Lido wstETH contract reference.

Extend the illustration with two independently stipulated conversion observations. At the first observation, one wstETH corresponds to 1.20 stETH. Alice's 10 wstETH therefore corresponds to 12 stETH. At the second, one corresponds to 1.212 stETH, making the same quantity equivalent to 12.12 stETH.

The 0.12 stETH increase belongs to the wrapper conversion. Alice still has 10 wstETH in the Blue collateral record. It has not become 10.1 wstETH, and the conversion has not created another U supply position.

Keep the two gains in their own units: 5.999999 U from lending-account growth and 0.12 stETH from the illustrative wrapper-value change. Adding those numbers would mix denominations. Converting them to a common valuation currency requires separately chosen prices and a timestamp.

An underlying conversion is also distinct from the market oracle's valuation and an executable sale quote. Lido's unwrap returns stETH, so the example does not establish an immediate ETH exit or a guaranteed sale value. Nor does it promise that future conversion changes will be positive.

Lending supply does not replace collateral management

Morpho's collateral and LTV documentation makes collateral specific to each market. The supplied loan-token claim is not added to that collateral amount. If an account also borrows, keeping a supply position does not itself repay its borrow shares.

For example, a displayed U supply claim and U debt can coexist. A personal spreadsheet may subtract them to estimate net exposure, but the protocol's debt record changes through a completed repayment. Any plan to withdraw U and repay must also account for whether that U can be withdrawn. The borrow-shares and repayment-assets example follows the separate repayment conversion.

Collateral withdrawal instead depends on authorization and the resulting position's health. Loan-token withdrawal has its own liquidity check. Morpho's Blue function reference documents these distinct operations. Their different conditions matter when a wallet holds both kinds of position.

The general LTV comparison supplies useful vocabulary, but its Aave-style weighted-basket example does not define a Blue account. Use the market's oracle and LLTV for that account. The Morpho LLTV and liquidation-incentive guide separates the health boundary from collateral seized in a liquidation.

Validate what a yield display is measuring

For a real observation, first bind the chain, Morpho contract, market identifier, account and block. Then read the market parameters to identify the actual loan token, collateral token, oracle, IRM and LLTV. A token ticker or an interface's general “deposit” label cannot identify the accounting path by itself.

Stored supply totals can omit interest since the previous accrual. The pinned balance helper computes expected totals with pending interest and converts supply shares down to assets. It is an integration helper, separate from the core contract; its supplier helper also warns about fee-recipient share changes. Do not compare a pending-interest estimate with an older stored checkpoint and label the difference missing collateral income.

Finally, identify the source of each quoted rate. Blue borrowing interest comes from the chosen market IRM, as described in Morpho's interest-rate documentation. A collateral token's conversion mechanism and any separately advertised incentives need their own evidence. Retain those sources beside their quantities so another reader can reproduce which balance changed, in which token, and why.