Overview
Claude Sonnet 4.5 is the workhorse of the Claude family for vibe coding. It's roughly 5x cheaper than Opus while being significantly faster, and for most coding tasks the quality difference is small. This is the model powering Cursor's default Claude integration and the one most developers use daily.
Key Specs
| Spec | Details |
|---|---|
| Model ID | claude-sonnet-4-5-20250929 |
| Context Window | 200,000 tokens |
| Max Output | 16,000 tokens per response |
| Input Cost | $3 per million tokens |
| Output Cost | $15 per million tokens |
| Speed | Fast — noticeably quicker than Opus |
| Best For | Daily vibe coding, iteration, prototyping |
Why Sonnet is the Vibe Coding Favorite
- Speed + quality balance: Fast enough for rapid iteration, smart enough for complex code generation
- Cost-effective: At $3/$15 per million tokens, you can iterate extensively without burning through your budget
- Same context window: 200K tokens means you can still feed it large codebases
- Great for Cursor: The default Claude model in Cursor — optimized for IDE-based vibe coding
- Strong at all languages: Excellent with JavaScript/TypeScript, Python, Rust, Go, and more
When to Choose Sonnet Over Opus
Use Sonnet when: You're iterating quickly, prototyping, building standard web apps, or want to keep costs low. Sonnet handles 80% of coding tasks just as well as Opus.
Upgrade to Opus when: You hit a complex architectural decision, need to debug subtle multi-file bugs, or are building something with intricate business logic.
Example Prompt
Quick iteration prompt (perfect for Sonnet)
Add a search bar to the top of the page that filters
the card list in real time as the user types.
Make it case-insensitive and highlight matching text.