Claude Sonnet 3.5 vs Sonnet 4.5: Complete 2026 Comparison — Benchmarks, Pricing, and Which to Choose

TamilTech AI summary

Here’s a clear summary of the comparison for you. Anthropic released Claude 3.5 Sonnet in October 2024 and followed it with Claude Sonnet 4.5 in September 2025, bringing big gains in coding, agentic workflows, long-context handling, and safety. Sonnet 4.5 is a bit slower than the snappy 3.5 Sonnet in some cases, yet the gap is small for everyday work and fast-mode options help when latency matters. Pick 3.5 Sonnet only if you need maximum speed on simple queries, must keep older SDK behavior, or already rely on 3.5-specific integrations. For almost everyone else—especially new projects, coding help, large documents or codebases, agent tools, and stronger safety—Sonnet 4.5 is the better default at the same price point. Indian developers and startups in particular benefit from its 1M-token context for mixed Hindi, Tamil, Telugu, and English content, making it a strong choice even as GPT, Gemini, and open-source models compete.

• What is the main difference between Claude Sonnet 3.5 and 4.5?
• Is Claude Sonnet 4.5 more expensive than 3.5?
• Should I switch from Claude 3.5 Sonnet to 4.5?
• Which Claude model is best for coding in 2026?

AI-assisted summary, checked by the TamilTech editorial team.