Stacks Improvement Proposals.

A Proof of Transfer system integrating NFTs as dynamic rewards, aligning incentives, securing networks, and enhancing user participation through verifiable ownership.

X402 introduces a standardized framework for blockchain-native agent payments, enabling autonomous software agents to transact, coordinate, and compensate one another without relying on traditional financial rails. By embedding payment logic directly into agent interactions, X402 defines a permissionless, programmable payment layer where identity, execution, and settlement are unified on-chain. This proposal outlines how X402 can serve as a foundational primitive for agent economies—supporting microtransactions, streaming payments, and conditional execution across decentralized networks. The r…

Proposes allowing Stacks transactions (notably sBTC) to use native Bitcoin address formats (e.g. bc1…) instead of Stacks SP… addresses. The goal is to reduce UX friction for Bitcoin users by aligning address formats with what they already recognize, while preserving existing Stacks address semantics under the hood. This is primarily a tooling and ecosystem standard rather than a consensus-breaking change.

Proposes a standard trait extension to SIP-009 NFTs that supports encrypted or private metadata layers via on-chain commitments. The trait defines common methods and events so wallets, marketplaces, and indexers can recognize and interact with NFTs that include encrypted payloads, without requiring consensus changes. The aim is interoperability and consistent UX across encrypted NFT implementations.

Adapts the ERC-8004 agent registry standard from Ethereum to Stacks, enabling on-chain registries for agents, identities, or autonomous actors. The proposal defines discoverable and interoperable registry patterns that applications can rely on when interacting with agents. This SIP focuses on ecosystem standards for identity and agent coordination rather than core protocol changes.