wtf is solrail-core-sdk?

SolRail is a privacy tool for the Solana blockchain that lets someone shield their SOL or USDC tokens into a private pool, send them privately to someone else while they are inside that pool, and later unshield them back into a normal public wallet. The project is described as an early MVP covering just those three actions: shielding, private transfers, and unshielding. Under the hood it combines several pieces. The privacy guarantees come from zero knowledge circuits built with Circom and a proving system called Groth16, arranged in a join split pattern that takes two inputs and produces two outputs per private transaction. The on chain logic runs as Solana programs written with the Anchor framework, split into a pool program and a separate verifier program. A dedicated crypto package handles the underlying building blocks, including a hash function called Poseidon, the private notes that represent hidden balances, and a Merkle tree used to prove a note exists without revealing which one it is. On top of all this sits a TypeScript SDK for developers to build against, plus an indexer and a relayer service, and a React based wallet app for end users. The README lays out what stays private and what does not. While tokens sit inside the shielded pool, the sender's identity, the recipient's identity, and for private sends even the token type and amount are hidden. What remains visible on chain is the initial deposit into the pool, including who made it and how much, the final withdrawal out of the pool, the pool's total value locked, and general timing information about when transactions happen. Private addresses inside the system use a distinct zkSol prefix so they can be told apart from normal Solana addresses. Beyond a short quick start showing how to install dependencies, build the zero knowledge circuits and Anchor programs, and run the indexer, relayer, and web app locally for development, the README does not go into further detail about the project's design or its current state of completeness.