Claude Opus 4

Overview

Anthropic's May 2025 Opus-tier release, built for complex reasoning, extended thinking, and sustained multi-step analysis. Claude Opus 4 has since been superseded by several Opus generations — the current tier is Claude Opus 4.8 — and is deprecated on the API.

Why it matters

Opus 4 marked the point where Anthropic's top tier became a serious agentic workhorse — multi-document synthesis, nuanced legal analysis, and workflows that run for minutes. Its extended-thinking mode let it 'show its work,' which mattered for regulated industries needing auditable AI decisions. Today it is a legacy model: Anthropic has shipped Opus 4.5 through 4.8 since, with larger context windows and lower prices, so new builds should target Claude Opus 4.8. Its main relevance now is historical — and as a reminder that 'flagship' status in this market lasts months, not years.