Claude 3.5 Haiku vs Sonnet vs Opus: which one should you actually use?

Claude 3.5 Haiku vs Sonnet vs Opus: which one should you actually use? There are five Claude models right now and picking the wrong one will either cost you 10x more than you need to spend, or give you outputs that are basically useless. Here's the actual breakdown. Haiku - when speed and cost matter more than depth Haiku is for volume. It's the fastest and cheapest option by a wide margin. Good for classification, routing, quick summarisation, anything where you're running thousands of calls and don't need the model to think hard. If you're building a pipeline that processes user inputs before handing off to a bigger model, Haiku is your first pass. It won't handle nuanced reasoning. Don't ask it to write complex code or work through anything ambiguous. It'll hallucinate confidently. Sonnet - just use this for most things Sonnet is the one I default to. It's where Anthropic has put most of the optimisation work - good reasoning, solid code generation, sensible context handling. The pr