PT721 — Principal NFT (arbitrary maturity)

PT721 is the non-fungible sibling of PT20. Each NFT represents one (principal, maturity) position, where maturity can be any future date (not restricted to month boundaries).

• Standard: ERC-721
• Symbol: PT721 (collection: "Kairence PT-721 kDIEM")
• Exchange rate: Fixed 1:1 — principal DIEM at maturity, no fees.
• Cardinality: One singleton contract for the whole Venice path — every PT721 lives in the same collection.

How you get a PT721

By calling Locker.lockPT721(amount, maturity, recipient). The Locker:

1. Stakes your DIEM into the vault.
2. Mints a new PT721 tokenId to recipient, recording _positions[tokenId] = (amount, maturity).

You receive a unique NFT representing your position. You can read the position back at any time:

pt721.position(tokenId) → (principal, maturity)

How you redeem

After your position's maturity, call Redeemer.redeemPT721AndRequestUnstake(tokenId, beneficiary).

This burns the NFT and queues principal DIEM for unstake. After Venice cooldown + sync, you claim DIEM from the queue.

When to use PT721 vs PT20

Need	Use
Maturity on the 1st of a month, want DEX liquidity	PT20
Maturity on any specific date	PT721
Concentrated DEX liquidity, fungible with other lockers	PT20
Per-position metadata, NFT-marketplace listing	PT721

See PT20 vs PT721 for a longer discussion.

Tradeable on NFT marketplaces

PT721 is a standard ERC-721. You can list it on OpenSea, Blur, etc., or use it as collateral in NFT lending protocols. The position data (principal, maturity) is readable from the contract, so marketplaces can display "principal: 10 DIEM, matures Aug 15 2026" alongside the listing.

Locker binding

PT721's locker is a single mutable address, set initially by setLockerInitial and rotated via a 7-day timelock (proposeLocker / activateLocker). Only the current Locker can call PT721.deposit — this enforces the invariant that every PT721 corresponds to a Locker-issued lock with paired DD emission.

Unlike PT20 (where each PT20 contract has an immutable Locker), PT721 shares one Locker across all positions because PT721 is a singleton — there's no per-maturity deploy.

DD issuance for PT721

DD minted on PT721 lock uses the same formula as PT20:

DD = principal × floor(seconds_to_maturity / 86400)   (min 1 day)

The floor (vs ceiling) closes an attacker-friendly rounding where locking 1 second before a UTC day boundary would have issued 2 × amount DD. With floor + minimum 1 day:

• Sub-day lock → 1 DD per principal.
• 1 day exact → 1 DD per principal.
• 1 day + 1 second → 1 DD per principal.
• 2 days → 2 DD per principal.

No way to game the timestamp for extra DD.

Why not just per-day fungible PT20?

Per-day PT20 means 365 ERC-20 contracts per year. Liquidity would shatter into dust pools. PT721 preserves the arbitrary-maturity functionality without fragmenting fungible markets.

Limits

• principal is uint128, allowing positions up to ~3.4 × 10^38 DIEM.
• maturity is uint64, valid through year ~2554.
• tokenId starts at 1 and increments forever.