OpenKitx403 is an HTTP-native authentication protocol for Solana that uses standard HTTP 403 challenge-response flows and cryptographic wallet signatures to verify users without relying on opaque browser extensions or custom RPC middleware. It provides audited TypeScript and Python SDKs for both client and server, so web2 and web3 teams can plug in wallet-based sign-in, token-gated APIs, and NFT/FT ownership checks directly into their existing HTTP stack. The protocol is fully stateless on the server side, works with existing Solana wallets, and is designed to be transparent, verifiable, and self-hostable for production environments.