Claude Opus 4.8 is now generally available inside GitHub Copilot. Anthropic's latest flagship model brings meaningful gains in agentic coding, large-codebase navigation, and self-reported code reliability, and it lands at the same API price as Opus 4.7. The catch: it carries a 15x premium request multiplier in Copilot, making it the most expensive model in the picker by a wide margin.
What actually changed under the hood
Opus 4.8 builds on Opus 4.7 with improvements across benchmarks and is described by Anthropic as a more effective collaborator. The headline numbers back that up. On SWE-bench Verified, the model scores 88.6%, up from 87.6% on Opus 4.7 and 80.8% on Opus 4.6. On the harder SWE-bench Pro benchmark, it hits 69.2%, up from 64.3%. SWE-bench Pro is a benchmark that tests whether a model can autonomously resolve real GitHub issues, making it a strong proxy for practical coding ability.
Opus 4.8 is also the strongest computer-use and browser-agent model Anthropic has tested, scoring 84% on Online-Mind2Web, a meaningful jump over both Opus 4.7 and GPT-5.5. That said, Terminal-Bench 2.1 for agentic terminal coding still belongs to GPT-5.5 at 78.2%, with Opus 4.8 coming in at 74.6%.
The reliability story is the real headline
Raw benchmark scores are only part of the picture. The more interesting shift is in what Anthropic calls "honesty" -- the model's tendency to flag its own mistakes rather than silently ship broken code into your pipeline.
- Anthropic's evaluations found the model to be around four times less likely than its predecessor to leave flaws in its own code unremarked.
- Early testers found Opus 4.8 sharper in judgment when performing agentic tasks, more likely to flag uncertainty, and less likely to make unsupported claims.
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