12-Stage Pipeline for AI Agent Credential Verification Explained

A developer building the Universal Trust Adapter (UTA) found that verifying a cryptographic signature alone is insufficient for validating AI agent credentials. The system requires 12 sequential stages — from parsing raw bytes to issuer resolution, proof-of-possession, lifecycle checks, and policy enforcement — before issuing a final PERMIT, DENY, or UNDETERMINED verdict. Each stage addresses a distinct failure mode, such as expired credentials, revoked tokens, unknown issuers, or stolen keys. The pipeline is implemented in TypeScript and published as the open-source package @marketnow/trust-core, capable of processing 6,744 full verifications per second on a single core. Separating verification into discrete stages improves debuggability, enables partial result caching, and provides a clear audit trail for each decision.