Claude Sonnet 4 (20250514): Model Guide (2026)

claude-sonnet-4-20250514 is Anthropic’s current recommended Sonnet model. Released May 14, 2025, it delivers the best balance of capability and cost in the Claude model lineup. This is the model most developers should use for everyday coding, analysis, and generation tasks.

What the Model ID Means

claude-sonnet-4-20250514
│      │      │ │
│      │      │ └── Release date: May 14, 2025
│      │      └──── Version: 4
│      └───────── Tier: Sonnet (mid-range)
└──────────────── Family: Claude

The full model ID with date suffix ensures you always get this exact model version. Use it in production code to avoid unexpected behavior when Anthropic updates default aliases.

Why Sonnet 4 Is the Default Choice

Sonnet 4 is the model Anthropic actively recommends for most use cases. It replaced Sonnet 4.5 as the standard recommendation because:

• Best-in-class instruction following: Sonnet 4 is measurably better at following complex, multi-part instructions
• Strong coding performance: competitive with Opus on many coding benchmarks at one-fifth the cost
• Reliable tool use: consistent and accurate function calling, critical for agent workflows
• Good cost-to-quality ratio: $3/$15 per million tokens delivers the most value per dollar

Model Capabilities

Context Window

• 200,000 tokens input context
• Handles full codebases, long documents, and extended multi-turn conversations
• Effective context utilization across the full window (no significant quality degradation at the edges)

Coding

• Generates, reviews, and debugs code across all major languages
• Handles multi-file edits and cross-reference analysis
• Strong at test generation and refactoring
• Understands framework conventions (React, Django, Rails, Spring, etc.)

Instruction Following

• Sonnet 4’s defining strength — reliably follows complex instructions
• Adheres to formatting requirements, output constraints, and multi-step processes
• Particularly important for CLAUDE.md rules in Claude Code projects

Extended Thinking

• Supports extended thinking for complex reasoning tasks
• Allocate a thinking budget to improve accuracy on math, logic, and architecture decisions:

message = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=16000,
    thinking={
        "type": "enabled",
        "budget_tokens": 10000,
    },
    messages=[{"role": "user", "content": "Design a distributed cache system"}]
)

Tool Use (Function Calling)

• Full support for tool definitions and multi-tool sequences
• Can call multiple tools per turn when appropriate
• Compatible with the Claude Agent SDK

Vision

• Accepts images alongside text
• Analyzes screenshots, diagrams, charts, and UI mockups
• Useful for front-end development and design review

How to Use Everywhere

Python API

import anthropic
client = anthropic.Anthropic()
message = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=4096,
    messages=[
        {"role": "user", "content": "Write a Python function to parse ISO 8601 dates"}
    ]
)
print(message.content[0].text)

TypeScript API

import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const message = await client.messages.create({
  model: "claude-sonnet-4-20250514",
  max_tokens: 4096,
  messages: [
    { role: "user", content: "Write a Python function to parse ISO 8601 dates" }
  ],
});
console.log(message.content[0].text);

Claude Code CLI

# Launch Claude Code with Sonnet 4
claude --model claude-sonnet-4-20250514
# Or use the shorthand alias
claude --model sonnet

CLAUDE.md Configuration

## Model
Default: claude-sonnet-4-20250514
Use this model for all implementation tasks. Escalate to Opus only for
architecture decisions or security reviews.

API Mode (Programmatic)

echo "Refactor the auth module to use middleware" | claude --model claude-sonnet-4-20250514 -p

For details on API mode, see our API mode vs interactive guide.

Pricing

Prompt Caching

Prompt caching is where Sonnet 4 becomes particularly cost-effective. When the same system prompt or context is sent across multiple requests, cached input tokens cost just $0.30 per million — a 90% reduction.

This matters most for:

• Agent loops (system prompt + conversation history cached across turns)
• Batch processing (same instructions, different data)
• Claude Code sessions (CLAUDE.md content cached)

Monthly Cost Estimates

For precise cost tracking, see our ccusage guide.

Comparisons

vs Sonnet 4.5 (Predecessor)

Sonnet 4 supersedes Sonnet 4.5 for nearly all use cases. Use Sonnet 4 for new projects. Only use Sonnet 4.5 if you have tested both and Sonnet 4.5 performs better on your specific workload. See our Sonnet 4.5 model guide for details.

vs Opus 4

Use Sonnet 4 for feature implementation, code generation, bug fixes, test writing, and standard development tasks. This covers the majority of daily work.

Use Opus 4 for system architecture decisions, complex debugging that resists simpler attempts, security audits, and tasks requiring deep multi-step reasoning.

For model routing strategies, see our router guide.

vs Haiku 4.5

Use Haiku for: typo fixes, formatting, boilerplate generation, tab completion, and any task where speed matters more than depth. At 75% less cost than Sonnet, Haiku is the right choice for simple operations.

Need the complete toolkit? The Claude Code Playbook includes 200 production-ready templates, decision frameworks, and team setup guides for every Claude Code workflow.

Best Practices

When to Use Sonnet 4

• Feature implementation: writing new code, endpoints, components
• Bug fixes: diagnosing and fixing reported issues
• Code review: analyzing code for quality and correctness
• Test generation: writing unit and integration tests
• Refactoring: restructuring code while preserving behavior
• Documentation: generating code comments, API docs, README content

When to Escalate to Opus

• The task involves designing a new system from scratch
• Previous Sonnet attempts produced incorrect solutions
• The task requires reasoning about security implications across multiple systems
• You need to analyze a complex bug involving race conditions or distributed systems

When to Downgrade to Haiku

• Fixing a typo or renaming a variable
• Generating boilerplate from a template
• Running a simple search-and-replace
• Quick classification or categorization tasks

Frequently Asked Questions

Is Sonnet 4 the same as Sonnet 4.5? No. Despite the version numbers, Sonnet 4 is the newer model (released May 2025 vs September 2025 for 4.5). Sonnet 4 is generally better at instruction following and coding tasks.

Should I always use the full model ID? In production code, yes. Use claude-sonnet-4-20250514 to ensure consistent behavior. In interactive Claude Code sessions, the shorthand sonnet is fine.

Does Sonnet 4 support streaming? Yes. Both the API and Claude Code support streaming responses from Sonnet 4.

What are the rate limits? Rate limits depend on your API tier (free, build, scale), not the model. Check console.anthropic.com for your current limits.

Can Sonnet 4 handle a 200K-token input? Yes. Sonnet 4 supports the full 200K context window. Performance remains strong across the full window, though costs scale linearly with input size.

How does Sonnet 4 compare to GPT-4o or Gemini? Sonnet 4 is competitive with GPT-4o on coding benchmarks and generally stronger at instruction following. Direct comparisons depend on the specific task. Test on your own workloads.

Related Guides

• Sonnet 4.5 model guide — predecessor model comparison
• Claude Code cost breakdown — pricing across all models
• Model routing strategies — when to use which model
• Reduce Claude Code costs — save money without losing quality
• Claude Agent SDK — build agents on Sonnet 4
• Cost tracking with ccusage — monitor spend per model
• Claude Code prompt engineering — optimize prompts for Sonnet

• The Claude Code Playbook — comprehensive reference

• Claude temperature settings guide — Configure temperature for Sonnet 4

  Can I use Sonnet 4 with extended thinking and tool use simultaneously?

Yes. Extended thinking and tool use work together. The model can think through a problem before deciding which tools to call.

Is Sonnet 4 available on Amazon Bedrock and Google Vertex AI?

Yes. Sonnet 4 is available through both cloud providers. Check their documentation for the exact model ID format used on each platform.

Does Sonnet 4 support image input in Claude Code?

Claude Code does not currently pass images to the model. Image input is available through the API and Claude.ai web interface.

How often does Anthropic update the Sonnet model?

Anthropic releases new model versions periodically. Always use the full model ID with date suffix in production to avoid unexpected changes when defaults are updated.