Claude Opus 4.8

• - 🏢 Anthropic's most capable generally available Opus model, released May 2026.
• - 📏 1M-token context window by default; 128K max output tokens.
• - 🧠 Adaptive thinking with effort control defaulting to high.
• - 🔧 Built for long-horizon agentic coding and tool use.
• - 👁️ Multimodal: accepts text, image, and file inputs.
• - 🎯 Anthropic reports ~4x less likely than Opus 4.7 to miss code flaws.
• - 🌐 Supports web search and function calling for autonomous agents.
• - ⚡ Adds a research-preview fast mode and lower cacheable-prompt minimum.

Anthropic

Anthropic is an American artificial intelligence company headquartered in San Francisco, focused on developing large language models under the Claude family. Founded with a strong emphasis on AI safety research, the company has become one of the most…

Claude Opus 4.8 is Anthropic's flagship generally available model, released May 28, 2026, positioned for complex reasoning, long-horizon agentic coding, and high-autonomy enterprise work. It supports a 1M-token context window by default on the Claude API, Amazon Bedrock, and Vertex AI (200K on Microsoft Foundry), 128K max output tokens, adaptive thinking, and multimodal inputs including images and files. It ships alongside Claude Opus 4.8 Fast, offered as a research preview on the API.

Anthropic frames Opus 4.8 as a direct build on Claude Opus 4.7, keeping the same pricing and context window while focusing on quality. The company's documentation lists targeted improvements in long-horizon agentic coding: better long-context handling, fewer compactions, and improved compaction recovery. It also addresses a known Opus 4.7 issue—skipping required tool calls—with better tool triggering, and lowers the minimum cacheable prompt length to 1,024 tokens.

On reported evaluations, Anthropic states Opus 4.8 is roughly four times less likely than Opus 4.7 to let a code flaw pass unflagged, and emphasizes improved honesty—avoiding overconfident claims of progress.

The model extends a steady cadence over Claude Opus 4.6 and Claude Opus 4.5. A new mid-task instruction-update feature lets developers adjust permissions, token budgets, or environment context as an agent runs, without breaking the prompt cache.