ERC-7621 defines a multi-asset basket token standard. A conforming contract is an ERC-20 share token whose holders have proportional claims on a set of ERC-20 constituent tokens held at configurable target weights. A designated owner (via ERC-173) may update the constituent set and weights over time.
The standard covers:
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Queryable composition state (constituents, target weights, reserves)
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Multi-asset contribution with slippage protection
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Proportional multi-asset withdrawal with slippage protection
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Owner-managed rebalancing of constituents and weights
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Preview functions following ERC-4626 conventions
It intentionally does not standardize swap execution, oracle design, fee models, or valuation methodology, these are implementation concerns.
Relationship to existing standards: ERC-4626 standardizes single-asset vaults. ERC-7575 extends that to multi-asset entry points. Neither addresses manager-rebalanced weighted baskets where portfolio composition itself (constituent membership and target weights) is the primary standardized surface. ERC-7621 fills that gap. Where applicable, it follows ERC-4626 conventions (share-is-the-token, preview functions, rounding discipline).
PR: Website: Basket Token by AlvaraProtocol · Pull Request #1619 · ethereum/ERCs · GitHub
This replaces the earlier “Basket Token Standard (BTS)” proposal. The spec has been substantially rewritten with a new interface, new architecture (one basket per contract, ERC-173 ownership instead of mandatory ERC-721), formal specification with defined errors/events/edge cases, and complete rationale and security sections.
Feedback welcome, particularly on the interface surface area and the boundary between what is standardized vs. left to implementations.