UPIP: Universal Process Integrity Protocol with Fork Tokens for Multi-Actor Continuation

This document defines UPIP (Universal Process Integrity Protocol), a five-layer protocol for capturing, verifying, and reproducing computational processes across machines, actors, and trust domains. UPIP defines a cryptographic hash chain over five layers: STATE (input), DEPS (dependencies), PROCESS (execution), RESULT (output), and VERIFY (cross- machine proof). The stack hash chains these layers, ensuring that modification of any component is detectable. This document also defines Fork Tokens, a continuation mechanism for multi-actor process handoff. Fork tokens freeze the UPIP stack at a specific point and transfer it to another actor with cryptographic chain of custody. The receiving actor can verify what was handed off, validate capabilities, and continue the process with full provenance. UPIP integrates with TIBET [TIBET] for provenance tokens, JIS [JIS] for actor identity, and is transport-agnostic with JSON as the baseline serialization.