Claude 3.7 Sonnet: Complete Guide to Anthropic's Best Model

Claude 3.7 Sonnet: The Sweet Spot

Claude 3.7 Sonnet is Anthropic’s flagship model — the one most people should use. It balances intelligence, speed, and cost better than any other option.

Why Sonnet?

Model	Intelligence	Speed	Cost
Opus	Highest	Slowest	Most expensive
Sonnet 3.7	Very high	Fast	Moderate
Haiku	Good	Fastest	Cheapest

For 90%+ of tasks, Sonnet provides the best experience.

Key Capabilities

Coding (Best in Class)

• Top scores on coding benchmarks (SWE-bench, HumanEval)
• Powers Claude Code by default
• Excellent at Python, JavaScript, TypeScript, Rust, Go, Java, C++
• Strong at code review, refactoring, and debugging

Extended Thinking

Sonnet 3.7 supports Extended Thinking — it can “think step by step” internally before responding, producing better answers for complex problems.

200K Context Window

Process entire codebases, research papers, legal documents, or datasets in a single conversation.

Vision

Analyze images, screenshots, diagrams, and documents (PDFs).

Using Sonnet in Claude Code

Claude Code uses Sonnet by default. Just install and go:

curl -fsSL https://claude.ai/install.sh | bash
cd your-project
claude

Using Sonnet in the API

import anthropic
client = anthropic.Anthropic()

message = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=4096,
    messages=[{"role": "user", "content": "Your prompt here"}]
)

Sonnet vs Opus: When to Upgrade

Use Opus for:

• Extremely complex reasoning tasks
• Research-level analysis
• Tasks where accuracy matters more than speed
• Maximum capability regardless of cost

Use Sonnet for:

• Daily coding work
• Content creation
• Data analysis
• Most professional tasks
• When speed and cost matter

Sonnet vs Haiku: When to Downgrade

Use Haiku for:

• Simple classification tasks
• Quick summaries
• High-volume API calls
• When cost is the primary concern
• Real-time applications needing low latency

Pricing

Usage	Sonnet Cost
Pro plan	Included ($20/mo)
Max plan	Included ($100-200/mo)
API input	~$3/million tokens
API output	~$15/million tokens

Related Articles

• Claude 4 Release — What’s next
• Claude API Guide — Use Sonnet in apps
• Claude AI Review 2026 — Full assessment
• Install Claude Code — Get started with Sonnet