Consensus mechanisms enable multiple agents to reach agreement on outputs through voting or discussion. Why needed: Different agents may produce different answers, need systematic way to reconcile, reduce hallucination through agreement, increase reliability. Voting mechanisms: Simple majority, weighted by confidence, quorum requirements, ranked choice. Discussion-based: Agents debate until convergence, share reasoning, update positions, mediator facilitates. Implementation: Parallel agent generation, answer extraction, voting algorithm, tie-breaking rules. Threshold options: Unanimous agreement required, supermajority (2/3), plurality wins, no consensus triggers fallback. Confidence integration: Agents provide confidence scores, weight votes accordingly, reject low-confidence contributions. Debate vs voting: Voting faster but less nuanced, debate explores reasoning but slower, hybrid approaches combine both. Failure handling: No consensus → escalate to human, request more agents, defer decision. Use cases: Fact-checking, quality control, high-stakes decisions, content moderation. Trade-offs: Higher cost (multiple agents), latency (waiting for consensus), complexity. Critical for mission-critical agent applications requiring reliability.