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, defaulting to high effort across all surfaces.
• 🔧 Better tool triggering and fewer agentic-coding compactions than Opus 4.7.
• 👁️ Multimodal: accepts text, image, and file inputs.
• 🎯 Roughly four times less likely than predecessor to leave code flaws unremarked.
• ⚡ Optional fast mode (research preview) reduces latency and cost.
• 🌐 Web search, function calling, and memory-driven long-horizon work.

Anthropic

Anthropic PBC is an American artificial intelligence company headquartered in San Francisco. Structured as a public benefit corporation, the lab develops large language models under the Claude name, with a research emphasis on building reliable, steerable,…

Claude Opus 4.8 is Anthropic's most capable generally available model, launched on May 28, 2026, and positioned for complex reasoning, long-horizon agentic coding, and high-autonomy knowledge work. It supports a 1M-token context window by default on the Claude API, Amazon Bedrock, and Vertex AI (200K on Microsoft Foundry), up to 128K output tokens, and adaptive thinking that defaults to high effort. It accepts text, image, and file inputs with text output.

The model is a direct upgrade to Claude Opus 4.7, itself following Claude Opus 4.6 and Claude Opus 4.5. Anthropic describes it as a "modest but tangible improvement," with gains concentrated in long-horizon agentic coding—better long-context handling, fewer compactions, and better compaction recovery—plus improved tool triggering, addressing an issue some users reported on Opus 4.7. Anthropic reports the model is about four times less likely than Opus 4.7 to leave flaws in its own code unremarked, reflecting a focus on honesty and coherence over many turns.

On developer experience, the minimum cacheable prompt length drops to 1,024 tokens, and developers can now update instructions mid-task without breaking the prompt cache. These changes target the iterative, tool-heavy workflows the model is built for.

This release also introduces a fast-mode research preview, mirrored by the separate Claude Opus 4.8 Fast variant, alongside siblings including Claude Sonnet 4.6 and the newer Claude Fable 5.