Transaction Level Minter Pattern

This design pattern couples the spend and minting endpoints of a validator, in order to have minimal spend costs, in exchange for a single execution of the minting endpoint.

The Pattern

Spend logic only ensures the minting endpoint executes. It does so by looking at the mint field and making sure only a non-zero amount of its asset (i.e. with a policy identical to the validator’s hash) are getting minted/burnt.

The arbitrary logic is passed to the minting policy so that it can be executed a single time for a given transaction.

When It Helps

Useful for:

• Validators that need transaction-level validation through minting
• Protocols using beacon tokens to signal state changes
• Batch operations where minting/burning confirms execution
• Reducing spend validator complexity

Not suitable for:

• Protocols that don’t use minting/burning mechanisms
• Cases where spend validation must be independent
• When minting logic should not control spending

Implementation

The scalus-design-patterns package provides helper functions and examples of use.

Additional Resources

• Anastasia Labs: Transaction Level Validator  - Original pattern documentation
• Scalus Design Patterns  - Implementation and tests