New BIP: Deterministic Satoshi Indexing

This BIP proposes a deterministic scheme for assigning serial numbers to satoshis and tracking their movement across transactions.

The goal is to provide a consistent and reproducible method that independent implementations can use to identify and track individual sats. The proposal does not require any changes to Bitcoin consensus rules, transaction formats or network behavior.

Implementations of this scheme have been in use on mainnet, signet, and testnet, including wallets with sat-level control and indexers that track sat locations. These systems construct standard Bitcoin transactions and operate entirely within existing protocol rules.

Without a shared specification, different implementations may assign sats inconsistently, leading to interoperability issues between wallets, indexers, and other software. This document attempts to standardize the indexing method so that independent implementations can arrive at identical results.

This is my first BIP submission, so feedback on structure, scope, and content would be appreciated.

This document standardizes an indexing method already used in production, with the goal of ensuring consistent behavior across implementations.

An earlier draft of a similar proposal was discussed previously: https://github.com/bitcoin/bips/pull/1408

This version has been revised and reframed as an informational interoperability specification based on deployment experience.