Haiku is Anthropic’s small, fast tier. It answers quickly and costs a fraction of Opus, which makes it the right choice when you’re running many calls or the task is well-scoped: classification, extraction, routing, quick summaries.
It won’t out-reason Opus on an open-ended problem — that’s the trade. Used where it fits, it keeps a brain responsive and cheap.
Best for: high volume, low latency, well-defined tasks.