Anthropic logo, creators of Claude 4

Claude 4 / Opus 4: Frontier Reasoning

Product LaunchesThe Agentic Era
Impact

At a glance

Date
May 2025
Era
The Agentic Era (2025–2026)
Category
Product Launches
Impact
4 / 5
Organizations
Anthropic

What Happened

Anthropic released Claude 4 Opus, a model with significantly enhanced reasoning, extended thinking capabilities, and the ability to sustain complex multi-step problem-solving over long contexts. It excelled at agentic tasks, code generation, and nuanced analysis.

Why It Mattered

Pushed the frontier of what AI assistants could accomplish autonomously. Extended thinking allowed the model to 'work through' complex problems systematically, approaching human expert-level performance on challenging tasks.

Organizations

Tags

Part of the The Agentic Era (2025–2026) era · Browse all product launches · View all 2025 milestones

Featured in these guides

History guide

History of Anthropic and Claude

A grounded history of Anthropic, from its 2021 founding and Constitutional AI through the Claude model family to the Claude 5 launch and the Mythos-class tier.

Frequently asked questions

When did Claude 4 / Opus 4: Frontier Reasoning happen?+

Claude 4 / Opus 4: Frontier Reasoning took place in May 2025.

Who was behind Claude 4 / Opus 4: Frontier Reasoning?+

For Claude 4 / Opus 4: Frontier Reasoning, organizations involved were Anthropic.

Why was Claude 4 / Opus 4: Frontier Reasoning important?+

Pushed the frontier of what AI assistants could accomplish autonomously. Extended thinking allowed the model to 'work through' complex problems systematically, approaching human expert-level performance on challenging tasks.

Which era of AI history does Claude 4 / Opus 4: Frontier Reasoning belong to?+

Claude 4 / Opus 4: Frontier Reasoning is part of the The Agentic Era era (2025–2026) — a major breakthrough in the product launches category.

Related Milestones

Anthropic logo, creators of Claude 4.5 Opus
Product

Claude 4.5 / 4.6 Opus: Frontier Agentic Capability

Anthropic released Claude 4.5 and 4.6 Opus, representing the frontier of AI capability in early 2026. These models demonstrated unprecedented reasoning depth, coding ability, and capacity for autonomous multi-step work. They could sustain complex agentic workflows, manage entire projects, and collaborate with other AI agents.

Anthropic
Anthropic logo, creators of Claude Fable 5
Product

Claude Fable 5 and Mythos 5: A New Model Tier

Anthropic released Claude Fable 5 and Claude Mythos 5, the first models in the Claude 5 family and a new 'Mythos-class' tier positioned above Opus in capability. The two share the same underlying model: Fable 5 shipped for general availability with additional safeguards on dual-use capabilities, while Mythos 5 was restricted to approved organizations. The Mythos class had been introduced in April 2026 through Claude Mythos Preview, released via Project Glasswing to a limited set of cyberdefense and infrastructure organizations.

Anthropic
Anthropic logo, creators of Claude Opus 5
Product

Claude Opus 5: Frontier Capability at Half the Price

Anthropic released Claude Opus 5, approaching Claude Fable 5-level intelligence at roughly half the price. It introduced an 'effort' dial that let users trade off cost and capability per request, alongside stronger coding, agentic, and self-verification performance.

Anthropic
Anthropic logo, creators of Claude 3
Product

Claude 3: Approaching Human-Level

Anthropic launched the Claude 3 family (Haiku, Sonnet, Opus), with Claude 3 Opus matching or exceeding GPT-4 on most benchmarks. It featured a 200K token context window, strong reasoning, nuanced instruction-following, and a 'personality' that users found distinctively thoughtful and careful.

Anthropic
Anthropic logo
Product

Claude 3.5 Sonnet: A Leading Coding Model

Anthropic's Claude 3.5 Sonnet emerged as one of the strongest widely used models for coding tasks, with developers praising its code generation, debugging, and software engineering capabilities. It powered tools like Claude Code, enabling AI to work directly inside developer environments.

Anthropic

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