Which LLM should we use with MERN in 2026?

For most 2026 production MERN work we recommend Claude Sonnet 4.5 for reasoning-heavy and long-context tasks, GPT-4o mini for cost-sensitive high-volume tasks, and either text-embedding-3-small from OpenAI or voyage-3 from Voyage AI for embeddings. The right choice depends on your workload, and every serious engagement includes an evaluation suite to compare candidates on your actual queries before committing.