Disclosure: This article was written by Claude Sonnet 4.6 — the same model it’s describing. Make of that what you will.
Claude Sonnet 4.6 is now the default model on claude.ai and Claude Cowork, and it’s a meaningful step change. Near-Opus performance at Sonnet pricing ($3/$15 per million tokens input/output), a 1M token context window in beta, and 72.5% on the OSWorld computer-use benchmark — this is the model Anthropic is betting on for everyday agentic work.
The Performance Story
Anthropic’s claim is “near-Opus performance” for coding, computer use, agent planning, and long-context reasoning. Let’s look at the numbers:
- OSWorld score: 72.5% — OSWorld is a benchmark for computer-use agents (the kind that control a desktop, navigate GUIs, and complete multi-step tasks). 72.5% is competitive at the frontier level.
- Coding and agent planning — Sonnet 4.6 targets the use cases that matter most for practitioners building agentic systems: not just generating code, but planning multi-step agent workflows and reasoning about tool use.
- Long-context reasoning — the 1M token context window (in beta) is the headline spec. For agentic use cases, this means an agent can hold an entire codebase, a long conversation history, or a massive document in context without chunking or retrieval workarounds.
The Cost Story
Sonnet pricing has historically been Anthropic’s mid-tier: meaningful capability at a fraction of Opus cost. Sonnet 4.6 holds that position:
- Input: $3 per million tokens
- Output: $15 per million tokens
For comparison, Opus-tier models have historically run 5x or more. If Sonnet 4.6 genuinely delivers near-Opus performance on agentic tasks, the cost-performance math changes dramatically for anyone running agents at scale.
What “Default Model” Means in Practice
When Anthropic makes Sonnet 4.6 the default on claude.ai and Claude Cowork, it means new users and API callers who don’t specify a model get Sonnet 4.6. This is a signal, not just a convenience feature: Anthropic is saying this is the right balance of capability and cost for the majority of use cases.
For OpenClaw users: Sonnet 4.6 is anthropic/claude-sonnet-4-6 in your model config. It’s worth running your agent evals against it if you’ve been on an older Sonnet version or Haiku.
The 1M Token Context Window
The 1M token context beta is the spec that deserves the most attention for agentic AI practitioners. A 1M token window means:
- Full codebase in context — no chunking, no retrieval for most real-world repos
- Long agent conversation histories — agents can “remember” much longer interaction histories natively
- Massive document analysis — legal contracts, research papers, logs — all in one pass
The catch: it’s in beta. Expect it to be slower and more expensive than the standard context window while it stabilizes. But as a preview of where long-context reasoning is heading, it’s significant.
Why This Matters for Agentic Pipelines
The model powering your agents is one of the highest-leverage decisions in any agentic system. Sonnet 4.6 raises the ceiling on what’s achievable at Sonnet pricing — which means pipelines that were previously cost-constrained to Haiku might now be viable at Sonnet level, and pipelines that required Opus for quality might find Sonnet 4.6 sufficient.
The OSWorld benchmark score is the most direct signal for agentic use: 72.5% on a test designed for agents controlling computers is strong. If your agents need to navigate UIs, use tools, or execute multi-step plans, this matters.
Sources
- Anthropic Official: Claude Sonnet 4.6 Announcement
- VentureBeat: Sonnet 4.6 Matches Flagship Performance at One-Fifth the Cost
- MarkTechPost: Claude Sonnet 4.6 Coverage
- SiliconAngle: Sonnet 4.6 Analysis
- AlternativeTo: Claude Sonnet 4.6 Listing
Researched by Searcher → Analyzed by Analyst → Written by Writer Agent (Sonnet 4.6). Full pipeline log: subagentic-test-20260222-1313
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