Claude Sonnet 4.6 Perfect Guide - Anthropic's Latest AI Revolutionizing Coding, Math, and Computer Use (February 2026)
📸 Introducing Claude 3.5 Sonnet \ Anthropic
What Is Claude Sonnet 4.6? — February 2026 Release Overview
On February 17, 2026, Anthropic officially launched Claude Sonnet 4.6. Within just two days, the entire developer community buzzed with excitement. The reason was clear: benchmark scores of 79.6% on SWE-bench Verified and 72.5% on OSWorld were previously exclusive to Opus 4.6, its flagship model just days prior. At only $3 per million input tokens — just one-fifth the cost of Opus — this new release represents a breakthrough in affordable high-performance AI.
Sonnet 4.6 has now become the default model for both claude.ai Free and Pro plans, and is simultaneously integrated into GitHub Copilot. Anthropic announced: "Real-world task performance that once required an Opus-level model is now achievable with Sonnet 4.6."
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7 Key Features of Claude Sonnet 4.6
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1. 1M Token Context Window (Beta)
For the first time in the Sonnet class, Claude Sonnet 4.6 supports a 1 million token context window — five times larger than the previous 200K limit. This enables workflows like analyzing entire large codebases in a single prompt or processing full contracts, research papers, or log files in one go. Currently in beta, it can be enabled via the API.
📸 Really Claude/Anthropic? : r/Anthropic
2. Major Math Improvement — 62% → 89%
Claude Sonnet 4.5 scored 62% on math benchmarks. Sonnet 4.6 jumps to 89% — a 27-point increase. It delivers stable performance not only in basic calculations, but in complex numerical reasoning and statistical analysis. Users in financial modeling, data science, and scientific computing will feel a tangible difference.
3. Adaptive Thinking Support
The "Thinking" capability — step-by-step reasoning for difficult problems — is now available for the first time on the Sonnet class. This significantly improves response quality in complex algorithm design and multi-step analytical tasks.
4. Computer Use — 72.5% on OSWorld
With a verified OSWorld score of 72.5%, it trails Opus 4.6 (72.7%) by only 0.2%. It performs GUI automation, browser navigation, form filling, and multi-step desktop workflows at near-human levels. This dwarfs GPT-5.2’s 38.2% and marks a leap in autonomous agent capability.
5. Improved Coding Accuracy — 79.6% on SWE-bench
Claude Sonnet 4.6 achieves 79.6% on SWE-bench Verified, a benchmark based on real GitHub issues. Developers now prefer it over Sonnet 4.5 by 70% and previous flagship Opus 4.5 by 59% for bug fixes, feature implementation, and patch creation. Higher instruction adherence reduces code over-generation.
6. Web Search + Code Execution Sandbox
Supports both web search and code execution within a secure sandbox environment. This allows real-time data retrieval and immediate processing through code — creating powerful dynamic pipelines. Enabled via tool_use in the API, with Memory and Programmatic Tool Calling now GA (Generally Available).
7. Opus-Level Security — Prompt Injection Defense
Resistance to prompt injection (malicious command injection) has been upgraded to match Opus 4.6 levels. This enhances safety in agent pipelines that handle untrusted external inputs.
Benchmark Comparison — Sonnet 4.6 vs Leading Models
| Benchmark | Sonnet 4.6 | Opus 4.6 | Sonnet 4.5 | GPT-5.2 |
|---|---|---|---|---|
| SWE-bench Verified | 79.6% | 80.8% | 77.2% | ~78% |
| OSWorld (Computer Use) | 72.5% | 72.7% | N/A | 38.2% |
| GPQA Diamond | 74.1% | 91.3% | ~65% | 73.8% |
| ARC-AGI-2 | 60.4% | ~65% | ~45% | N/A |
| Math | 89% | ~92% | 62% | N/A |
| Context Window | 1M (Beta) | 200K | 200K | 128K |
Pricing & Access Methods
API Pricing
- Input Tokens: $3 / 1M tokens
- Output Tokens: $15 / 1M tokens
- 5x cheaper than Opus 4.6 ($15/$75)
- Cache Prompts: $0.30 / 1M tokens (90% reduction)
How to Use
Call the model using the model ID claude-sonnet-4-6-20260217 in the Anthropic API. claude.ai Free/Pro users automatically get Sonnet 4.6 as the default model with no setup needed. In GitHub Copilot, simply select Claude Sonnet 4.6 from the model selector.
Sonnet 4.6 vs Opus 4.6 — Which Should You Choose?
Choose Sonnet 4.6 When
- Coding, bug fixing, PR reviews (only 1.2% behind Opus)
- GUI automation and computer use (just 0.2% gap)
- Processing large documents (when 1M context is essential)
- Cost optimization is key in production workloads
- Low-latency, real-time response is critical
Choose Opus 4.6 When
- Graduate-level scientific or medical reasoning (GPQA: +17pp)
- Complex legal or financial document analysis
- Long-horizon multi-step reasoning tasks
- Security research (powered by Claude Code Security)
Key Implications for Developers
Since Sonnet 4.6’s launch, the software development landscape has shifted dramatically. Alongside Claude Code Security, Anthropic is moving beyond "AI-assisted development" toward "AI-executed development" — where AI agents perform developer-grade tasks autonomously. Its integration with GitHub Copilot alone now puts powerful AI coding capabilities in the hands of hundreds of millions of developers.
Anthropic has also updated the knowledge cutoff from February 2025 to August 2025, a six-month leap. This improves understanding of the latest libraries and APIs. Users can expect more accurate answers on recent tech stacks like React 19, Next.js 15, and Python 3.13.
Summary — Claude Sonnet 4.6 Key Takeaways
- Release Date: February 17, 2026
- Coding (SWE-bench): 79.6% — just 1.2% behind Opus
- Computer Use (OSWorld): 72.5% — only 0.2% behind Opus
- Math: Increased from 62% to 89% (+27 points)
- Context Window: Expanded from 200K to 1M tokens (beta)
- Pricing: $3/$15 per million tokens (5x cheaper than Opus)
- Default Model: Now on claude.ai Free/Pro and GitHub Copilot
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