Rerankers in practice: Cohere v3 vs bge-reranker vs Jina

Results on support-doc RAG: - Cohere Rerank v3: Strongest zero-shot; higher latency and cost. - bge-reranker-large: Competitive quality, great self-hosted option. - Jina Reranker: Fast and affordable; solid for short passages. Key: Use rerankers to cut k aggressively without hurting quality. Measure answer faithfulness, not just top-1 overlap. Cache rerank inputs to control cost. For multi-lingual, test per language; quality varies.