What Makes Opus 4.6 Different

Claude Opus 4.6 represents a fundamental leap in AI capability. It's not just incrementally better — it introduces entirely new categories of what's possible with language models.

The Key Breakthroughs

1. Extended Thinking

Opus 4.6 can "think" before responding. When enabled, the model performs chain-of-thought reasoning internally before generating its answer. This dramatically improves performance on:

• Complex mathematical proofs
• Multi-step logical reasoning
• Code architecture decisions
• Nuanced analysis of ambiguous situations

Think of it as the difference between answering a question off the top of your head versus taking time to work through the problem on paper.

2. One Million Token Context Window

With a 1M token context window, Opus 4.6 can process approximately:

• ~750,000 words of text (roughly 10 full-length novels)
• ~30,000 lines of code in a single request
• Hundreds of pages of documentation simultaneously

This eliminates the need for complex chunking strategies and RAG pipelines in many use cases.

3. Agentic Excellence

Opus 4.6 excels at agentic tasks — workflows where the AI needs to:

• Plan multi-step approaches
• Use tools and APIs
• Handle errors and adapt
• Maintain context across long interactions
• Make decisions with incomplete information

4. World-Class Code Generation

Opus 4.6 achieves state-of-the-art results on coding benchmarks:

• SWE-bench Verified: 72.5% — the highest score by any model
• Terminal-bench: #1 for real-world agentic coding tasks
• TAU-bench: Top performance on complex, multi-step tool use

Capability Comparison

Feature              | Opus 4.6  | Sonnet 4.6 | Haiku 4.5
---------------------|-----------|------------|----------
Max Context          | 1M tokens | 200K       | 200K
Extended Thinking    | ✅ Yes    | ✅ Yes     | ❌ No
Max Output           | 32K       | 16K        | 8K
Agentic Performance  | Highest   | High       | Moderate
Code Quality         | Best      | Very Good  | Good
Cost (per 1M input)  | $15       | $3         | $0.80

When to Use Opus 4.6

Choose Opus 4.6 when you need:

• Maximum accuracy on complex tasks
• Extended reasoning for hard problems
• Long-context document analysis
• Building reliable autonomous agents
• Code generation for complex systems

Consider Sonnet 4.6 when you need:

• Good performance at lower cost
• Faster response times
• High-volume applications

Consider Haiku 4.5 when you need:

• Maximum speed
• Simple classification or extraction tasks
• Cost-sensitive high-volume processing

Understanding these trade-offs is crucial for building cost-effective AI applications.