Anthropic Releases Claude Sonnet 4.6 with Opus-Level Performance at 1/5th Cost
Claude Sonnet 4.6 achieves 79.6% SWE-bench and 72.5% OSWorld, matching Opus 4.6 capabilities while maintaining $3/$15 pricing.
Anthropic Launches Flagship-Class Sonnet
Anthropic released Claude Sonnet 4.6 on February 17, 2026—just 12 days after launching Opus 4.6. The new model delivers near-flagship performance at mid-tier pricing, fundamentally changing the cost-performance equation for AI applications.
Key Metrics
SWE-bench Verified: 79.6% (vs Opus 4.6's 80.8%) OSWorld-Verified: 72.5% (vs Opus 4.6's 72.7%) GDPval-AA: 1633 Elo (actually beats Opus 4.6's 1606) Finance Agent v1.1: 63.3% (beats Opus 4.6's 60.1%)New Features
1M Token Context Window (Beta)
Sonnet 4.6 supports 1 million tokens of context—roughly 750,000 words or 5-10 full codebases. This is paired with automatic context compaction that summarizes older content, enabling effectively unlimited conversations.
Adaptive Thinking
The new `effort` parameter replaces binary extended thinking. Options include low, medium, high, and auto—allowing developers to balance speed, cost, and reasoning depth per request.
Enhanced Computer Use
At 72.5% OSWorld, Sonnet 4.6 matches Opus 4.6's computer use capabilities within 0.2%, making sophisticated desktop automation accessible at Sonnet pricing.
Pricing
| Model | Input ($/M) | Output ($/M) |
| Sonnet 4.6 | $3 | $15 |
| Opus 4.6 | $15 | $75 |
Sonnet 4.6 delivers ~98-99% of Opus performance at 20% of the cost.
User Preferences
In early testing:
- 70% preferred Sonnet 4.6 over Sonnet 4.5
- 59% preferred Sonnet 4.6 over Opus 4.5
Users cited better instruction following, fewer hallucinations, and reduced over-engineering.
Availability
Sonnet 4.6 is the new default for Free and Pro users on Claude.ai. Available immediately via:
- Claude.ai (Free & Pro)
- Claude Code
- Claude Cowork
- Claude API (claude-sonnet-4-6-20260217)
- AWS Bedrock
- Google Vertex AI
- Microsoft Foundry
Industry Reaction
"This changes the economics of AI deployment," said one enterprise CTO. "We were budgeting for Opus-level costs. Sonnet 4.6 lets us do more with less."
VentureBeat notes: "Anthropic's Sonnet 4.6 matches flagship AI performance at one-fifth the cost, accelerating enterprise adoption."
What's Next
With both Opus 4.6 and Sonnet 4.6 released in February, attention turns to Claude 5 speculation. Prediction markets suggest Q2-Q3 2026 for the Claude 5 family.