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Borrow Blue to Midnight

BorrowBlueToMidnightCallback migrates a borrower from a variable-rate position on Morpho Blue into a fixed-rate position on Morpho Midnight in a single take.

Description​

The borrower has a variable-rate position on Blue and posts a sell (borrow) offer on Midnight with this callback as the receiver. When the sell (borrow) offer is taken, the Midnight proceeds (sellerAssets) land on the callback. The callback uses them to repay the Blue debt, withdraws the Blue collateral, and supplies it to Midnight on the borrower's behalf, so the borrower exits the take with a fixed-rate borrow position on Midnight.

Blue has no maturity, so the renewal window is anchored to the user's renewalCadence (for example, FourWeekCadence) rather than a source maturity timestamp.

Step-by-step callback execution​

The borrower posts a sell (borrow) offer on the Midnight target market with receiverIfMakerIsSeller set to this callback. The offer carries the callback wiring; the take triggers it.

BorrowBlueToMidnightCallback flow: a taker calls take() on the Midnight market, the proceeds (sellerAssets) repay the Blue debt, and the Blue collateral is moved to Midnight.
  1. Take: A taker fills the borrower's sell (borrow) offer on the Midnight target market by calling MORPHO_MIDNIGHT.take(). The Midnight proceeds (sellerAssets) land on the callback because the offer's receiverIfMakerIsSeller points at it, and Morpho Midnight invokes onSell on the callback.
  2. Validate: The Blue source market and the Midnight target market must share the same loanToken. The Blue market's single collateral token must appear somewhere in the Midnight market's collateral set; the matching slot is resolved automatically by the callback.
  3. Calculate and transfer fees: An effective-price fee is derived from the offer's tick and applied to the interest portion only, then transferred to the protocol fee recipient.
  4. Repay Blue: The callback repays the borrower's variable-rate debt with sellerAssets - fee. On the final fill the position is closed in shares (exactly zero); on partial fills the debt is repaid pro-rata in assets.
  5. Withdraw collateral: The matching amount of collateral is withdrawn from Blue (pro-rata on partial fills, in full on the final fill).
  6. Supply collateral: The withdrawn collateral is supplied to the matching slot on the Midnight market on the borrower's behalf.

Prerequisites​

  • The borrower must authorize the callback on Morpho Blue. Blue's authorization surface is distinct from Midnight's, so granting Midnight authorization is not sufficient.
  • The offer's receiverIfMakerIsSeller must point at this callback so sellerAssets lands here before onSell runs.
Single-collateral migration

Only the Blue market's single collateral token is migrated. If the Midnight target lists additional collateral slots, the borrower must supply those separately (for example, via Supply Collateral). They are not pulled by this callback.