Claude Opus vs Sonnet vs Haiku: Which Should You Use?

OpenRouter compares Anthropic’s Claude Opus 5.5, Sonnet 5.5, and Haiku 5.5 as tiers sharing a one-million-token context window and multimodal input support but differing substantially in price and benchmark performance. Its tests found that all three models passed 11 hidden-test coding tasks and a Claude Code bug-fixing exercise, while Sonnet matched or exceeded Opus on its GPQA Diamond and τ-bench evaluations at roughly half the per-token cost, and Haiku handled routine, well-specified work at a fraction of either model’s cost. Based on these results, the article recommends Sonnet as a general default, Haiku for high-volume tasks, sub-agents, classification, extraction, and bulk edits, and Opus for long, ambiguous, or high-stakes work where errors may outweigh token costs. It cautions that the tests were limited and encourages teams to evaluate models against their own workloads using Ori Eval, while explaining that OpenRouter and Claude Code can switch models through model strings, environment variables, or routing tools.

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