Claude Sonnet 5: Complete Features & Performance Guide
Deep dive into Claude Sonnet 5: all features, benchmark performance, pricing analysis, and why it's the best value AI model for developers in 2026.
TL;DR
Claude Sonnet 5 (codename "Fennec") delivers Opus 4.5-level performance at half the cost. With 80.9% SWE-bench score, 500K context window, and enhanced agent capabilities, it's positioned as the best value AI model for most production workloads.
The Fennec Leak Confirmed
Model ID: claude-sonnet-5-20260215, Context: 500K tokens, SWE-bench: 80.9%, Pricing: $1.50/$7.50 per million tokens.
Benchmark Performance
| Benchmark | Sonnet 5 | Opus 4.5 |
|---|
| SWE-bench Verified | 80.9% | 80.9% |
| GPQA Diamond | 85.2% | 87.3% |
| HumanEval | 96.8% | 97.3% |
Pricing Revolution
Sonnet 5 offers Opus-level performance at 90% lower cost—a game-changer for developers.
Conclusion
Claude Sonnet 5 redefines the price-performance curve. By delivering Opus 4.5 capabilities at 90% lower cost with 2.5x more context, it becomes the default choice for most AI applications.