Claude Opus 4.6 Explained

Benchmarks, Long Context, and How to Use It in Practice

Anthropic positions Claude Opus 4.6 as better at planning, persistence, and agentic work.

True. But incomplete.

The real shift: Opus 4.6 manages effort explicitly now. It decides when to slow down, when to scan broadly, when to commit, and when to push through difficulty without asking permission.

Claude Opus 4.6 leads on GDPval-AA, an evaluation designed to measure performance on economically valuable knowledge work across domains like finance, legal, and research.

That changes how you should use it.

What’s in this article:

• What actually changed and why it matters

• A practical playbook for getting leverage from it

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What actually changed in Opus 4.6

Anthropic's claim:

“Across agentic coding, computer use, tool use, search, and finance, Opus 4.6 is an industry-leading model, often by a wide margin. The table below shows how Claude Opus 4.6 compares to our previous models and to other industry models on a variety of benchmarks.”

Here's what that means in practice:

Across agentic coding, tool use, search, and multidisciplinary reasoning, Claude Opus 4.6 consistently ranks at or near the top among frontier models.

1. Effort is now adaptive

Opus 4.6 decides how much reasoning to apply based on task complexity.

Hard problems get longer planning and revisited reasoning. Simple ones move faster.

This shows up through effort levels and adaptive thinking, but also in default behavior.

What this means for you: Stop treating all prompts the same. The model responds differently to ambiguous versus well-scoped work now.

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2. Long context is usable, not theoretical

Claude Opus 4.6 maintains strong retrieval performance deep into long sessions, demonstrating that its 1M token context window is usable rather than theoretical.

Opus 4.6 has a 1M token context window (beta). More importantly: performance holds deep into long sessions.

This fixes context degradation in large codebases, long documents, and multi-source research.

What this means for you: Front-load material instead of drip-feeding context. The model can handle it.

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3. Agentic stamina improved

Opus 4.6 sustains multi-step work without drifting or asking for reassurance.

It tries alternatives internally and commits to implementations faster.

This shows up in agentic coding, debugging, and complex research.

What this means for you: If you don’t define scope boundaries, it may do more than you expected.

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4. Writing quality holds over distance

Style matching, structural coherence, and intent persistence are materially better in long-form documents.

What this means for you: Claude can act as a true co-author if you treat voice and constraints as first-class inputs.

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When Opus 4.6 is the right tool

Opus 4.6 shines when tasks are:

1. Ambiguous rather than procedural

2. Large rather than isolated

3. High-stakes rather than disposable

4. Multi-artifact rather than single-file

If your task is trivial, dial effort down.

If it’s strategic, architectural, or analytical, Opus 4.6 is where gains compound.

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What’s behind the paywall

The premium section is a hands-on operating guide, not commentary.

1. A Simple Operating Model
   How to work with Opus 4.6’s adaptive effort system. When to let it run, when to constrain it.

2. Best Practices by Task Type
   Specific approaches for coding, research, writing, and analysis. What works, what doesn’t.

3. Do’s and Don’ts
   Clear rules that prevent overthinking and scope creep. Learned from 100+ hours using Opus 4.6.

4. Reusable Prompt Library
   Prompts designed specifically for Opus 4.6’s capabilities. Tested, refined, ready to use.

5. Copy-Pasteable Templates
   Adapt immediately. No guessing what to try first.

This is meant to be used, not read once.

The Claude Opus 4.6 Operating Guide