Claude Opus 4.6 Review: Anthropic's Best-Aligned Frontier Model

Anthropic has always positioned itself as the safety-first AI company, and Claude Opus 4.6 is the strongest argument yet that safety and capability are not opposing forces. This model is simultaneously one of the most powerful and most trustworthy AI systems available, excelling in long-context reasoning, legal analysis, coding, and agentic workflows. After extensive testing, we believe it occupies a unique and important position in the current landscape.

Adaptive Thinking and Effort Controls

One of Opus 4.6's most distinctive features is its adaptive thinking system. Rather than offering discrete modes like GPT-5.2's Instant/Thinking/Pro split, Claude dynamically adjusts its reasoning depth based on task complexity. Ask it a simple factual question and it responds quickly. Present it with a multi-layered legal hypothetical and it automatically engages deeper reasoning chains.

The effort controls give users fine-grained influence over this behavior. You can explicitly request minimal, standard, or extended thinking, or let the model decide. In practice, the automatic mode works remarkably well. We found it correctly identifying when a problem required deeper analysis roughly 90% of the time. The explicit controls are useful for edge cases where you know a problem is harder (or easier) than it appears.

The 1M Context Advantage

Claude Opus 4.6 offers a 1 million token context window, and unlike some competitors, it actually uses it effectively. We tested retrieval accuracy with a 900K-token corpus of mixed legal documents and found the model could accurately locate and synthesize information from any position in the window. The "lost in the middle" problem that plagued earlier long-context models is largely solved here.

This matters enormously for professional workflows. Lawyers can feed in entire case files. Researchers can include dozens of papers. Developers can provide complete codebases. The model does not just store this context; it reasons over it coherently, drawing connections between documents that are hundreds of thousands of tokens apart.

Agent Teams and Delegation

Opus 4.6 introduces agent teams, a capability that allows the model to spawn and coordinate sub-agents for complex tasks. In our testing, we asked it to analyze a startup's complete financial documentation, legal agreements, and technical architecture simultaneously. The model delegated sub-tasks to specialized agents, coordinated their outputs, and synthesized a coherent final analysis.

This is not just a gimmick. For complex projects that span multiple domains, agent teams genuinely reduce turnaround time and improve output quality. The coordination overhead is handled internally, and the results feel more thorough than what a single-pass analysis would produce.

Legal Reasoning and Professional Use

Claude Opus 4.6 achieves 90.2% on BigLaw Bench, a benchmark designed to test the kind of nuanced legal reasoning that practicing attorneys perform daily. This is not just pattern matching on legal text; the model demonstrates genuine understanding of precedent hierarchies, jurisdictional nuances, and the interplay between statutory and case law.

We had a practicing attorney review Claude's analysis of several complex contract disputes, and the feedback was striking: the model's reasoning was "substantively correct and well-structured, comparable to a strong junior associate." It identified relevant issues, flagged risks, and suggested negotiation points that demonstrated real analytical depth.

Coding Capabilities

On coding benchmarks and real-world tasks, Opus 4.6 is a top-tier performer. It handles large refactoring projects with ease, maintaining consistency across dozens of files. Its understanding of software architecture is strong, and it excels at explaining design tradeoffs rather than just generating code.

Where Claude particularly shines is in code review and debugging. Present it with a complex bug report and a large codebase, and it methodically traces through the logic, identifies root causes, and proposes fixes that account for edge cases. The 1M context window means it can hold entire projects in memory while doing this work.

Safety and Alignment

This is where Anthropic's investment pays off most visibly. Claude Opus 4.6 outperforms GPT-5.2 by 144 Elo on GDPval, a benchmark measuring the model's tendency to produce harmful, biased, or misleading outputs. In practice, this means Claude is notably more careful about hedging uncertain claims, refusing genuinely harmful requests, and flagging when its knowledge might be outdated.

Importantly, this safety does not come at the cost of usefulness. Earlier Claude models were sometimes criticized for being overly cautious, refusing benign requests out of an abundance of caution. Opus 4.6 has largely solved this calibration problem. It is helpful when it should be helpful and cautious when caution is warranted.

Strengths and Weaknesses

Strengths:

• 1M context window with excellent retrieval across the full range
• Adaptive thinking automatically matches effort to task complexity
• Industry-leading legal reasoning and professional analysis
• Agent teams enable complex multi-domain workflows
• Best-in-class safety alignment without sacrificing usefulness
• Exceptional at large-scale code refactoring and architecture work

Weaknesses:

• Raw math performance slightly trails GPT-5.2 Pro mode on the hardest competition problems
• Agent teams feature has a learning curve and is not always intuitive to configure
• Pricing is premium, particularly for high-volume API usage
• Image understanding, while good, is not as strong as Gemini 3 Pro's vision capabilities
• Occasionally verbose in responses where conciseness would be preferred

Verdict: 9.3/10

Claude Opus 4.6 is the best model for long-context reasoning and safety-conscious deployments. It is the model you choose when accuracy, trustworthiness, and depth of analysis matter more than raw speed. For legal professionals, researchers, and engineering teams working on large codebases, it is arguably the single best option available. The adaptive thinking system is elegant, the 1M context window is genuinely useful, and the safety profile sets the industry standard. If your work demands reliability and nuance, Claude Opus 4.6 should be at the top of your list.