Consensus Hardening Protocol is a governance layer designed for multi-agent AI pipelines where reliable, tamper-resistant decision-making matters. It imposes a formal state machine — EXPLORING → PROVISIONAL_LOCK → LOCKED — so that no agent can prematurely commit a decision before the group has reached a defensible consensus. Foundation disclosure requires each model to surface its assumptions before voting. An adversarial attack stage stress-tests proposed conclusions before they advance. The R0 gate acts as a hard checkpoint before any lock is issued. All inter-agent communication travels in structured, cross-model payload envelopes that create a full audit trail. Useful for teams building agentic workflows, autonomous research pipelines, or any system where multiple AI models must reach a trustworthy shared conclusion without a human in the loop at every step.