Claude Opus 4.8
Claude Opus 4.8 is Anthropic's most capable Opus-tier model with adaptive thinking and upgraded behavior for long-horizon coding-agent tasks.
Teams compare Opus 4.8 with Fable 5 and Mythos 5 when deciding whether they need public frontier capability, stronger refusal routing, or an invitation-only policy model.
Anthropic describes Claude Opus 4.8 as its most capable Opus-tier option and publishes launch, pricing, and behavior changes in the official Claude API docs. The model keeps Opus capabilities while improving long-horizon stability and adaptive thinking control.
- High-complexity coding and platform engineering.
- Long-horizon agentic orchestration with multi-step tasks.
- Hard bug investigation and autonomous change routing.
- Task escalation routing where cost and risk are both tightly managed.
Claude Opus 4.8 is positioned as the top Opus-tier model for complex reasoning and coding-heavy autonomy work. Official model docs confirm 1M context, 128k max output, adaptive thinking, and the same core tooling envelope as earlier Opus releases.
- Model ID and platform availability are covered in the Anthropic model-overview docs.
- Effort defaults to high, and prompt-caching behavior is improved versus Opus 4.7.
- Adaptive thinking is the supported reasoning mode; extended thinking budgets are not used on Opus 4.8.
In practice, Opus 4.8 is often the baseline for teams needing strong Opus-tier quality without moving to the public Fable 5/Mythos 5 frontier tier. This distinction matters most for risk profiles and runtime budget planning.
- Opus 4.8 improves agent loops where tool use and long-horizon consistency matter.
- Opus 4.8 uses a 1M context window by default on API/AWS/Vertex; Microsoft Foundry exposes a 200k context window.
- Teams should still benchmark against their own task mix before making it the default.
- Operational cost is controlled by effort and task routing, not only token throughput.
Claude Opus 4.8 FAQ
Page-level questions for Claude Opus 4.8.
When should I use Claude Opus 4.8 instead of Claude Fable 5?+
Use Opus 4.8 when you need Opus-tier quality and governance-friendly operational behavior in a known coding-or-agent workflow, and when your team is optimizing for robust long-horizon performance without needing the Mythos-class invocation model path.
Is Opus 4.8 publicly available?+
Yes, Opus 4.8 is part of Anthropic's current Opus family on Anthropic API and partner surfaces. Availability details should be confirmed per account and region in the official API and platform settings.