AssemblyAI Voice Agent API vs OpenAI Realtime API: Which should you use?
Dev.to AI
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Generative AI
AI Research
OpenAI's Realtime API was one of the first products to make building voice agents feel accessible. Stream audio in, get audio back - simple idea, big impact. But as developers move from prototype to production, a different set of requirements kicks in: speech accuracy on real-world entities, cost predictability, and a developer experience that doesn't fight you. AssemblyAI's Voice Agent API launched in April 2026 as a direct alternative - same simplicity, fundamentally different architecture. Here's an honest comparison of the two.