‘Claude Opus 4.5 vs Sonnet 4.5 In-Depth Comparison: The Optimal Strategy of

A detailed comparison of Claude Opus 4.5 and Sonnet 4.5 performance, pricing, and use cases, mastering the efficient pairing strategy of using Opus for reasoning and thinking, Sonnet for execution and implementation.

After the release of the Claude 4.5 series, many developers face a practical question: How to choose between claude-opus-4-5-20251101 and claude-sonnet-4-5-20250929? The answer is actually quite simple—Use Opus for reasoning and thinking, use Sonnet for execution and implementation.

Core Value: Master the differences and pairing strategies of these two models to achieve the best cost-effectiveness in Claude Code and API scenarios.

Core Differences: Claude Opus 4.5 vs Sonnet 4.5

Let's look at the most critical comparison data first:

One-Sentence Summary of Differences

• Opus 4.5: Most intelligent, strongest reasoning capability, suitable for complex thinking
• Sonnet 4.5: Best cost-effectiveness, faster speed, suitable for daily execution

This is why the best practice is "Use Opus for reasoning, Sonnet for execution."

Claude Opus 4.5 In-Depth Analysis

Opus 4.5 is currently the most powerful model in the Claude series, leading across multiple benchmarks.

Claude Opus 4.5 Core Advantages

1. Top-Tier Reasoning Capability

On the ARC-AGI-2 test (measuring a model's ability to solve novel problems), Opus scores 37.6%, nearly 3 times higher than Sonnet's 13.6%. This means Opus can make better reasoning and judgments when facing problems it has never encountered before.

2. Industry-Leading on SWE-bench

Opus 4.5 achieves 80.9% on SWE-bench Verified, the highest score among all AI models currently. This benchmark measures the ability to solve real-world software engineering problems.

3. More Efficient Token Usage

An interesting finding: although Opus is more expensive, it uses fewer tokens to complete the same tasks. Tests show that Opus uses 19.3% fewer total tokens than Sonnet when completing the same application development tasks.

4. Exclusive effort Parameter

Opus 4.5 is the only model that supports the effort parameter, allowing you to control how many tokens Claude uses when responding, flexibly balancing quality and cost.

Claude Opus 4.5 Use Cases

Usage Recommendation: Opus is suitable for the "thinking it through" phase. When you face complex problems and need to make important decisions, let Opus do the thinking. But don't use it for simple code modifications—that's overkill.

Claude Sonnet 4.5 In-Depth Analysis

Sonnet 4.5 is the "workhorse" of the Claude series, achieving the best balance between performance and cost.

Claude Sonnet 4.5 Core Advantages

1. Cost-Performance Champion

Sonnet's price is 60% of Opus ($3/$15 vs $5/$25), but the performance gap isn't that large. For most tasks, Sonnet is completely sufficient.

2. Faster Response Speed

Due to its lighter model, Sonnet's response speed is noticeably faster than Opus, which is very important in development scenarios requiring frequent interaction.

3. Supports 1M Context (beta)

Sonnet is currently the only Claude model supporting a 1M token context window, offering clear advantages when processing extremely large codebases.

4. Excellent Agent Capabilities

Sonnet 4.5 is specifically optimized for agent tasks, supporting browser operations, spreadsheet processing, cross-file debugging, and other complex workflows.

Claude Sonnet 4.5 Use Cases

Usage Recommendation: Sonnet is suitable for the "getting it done" phase. When you already know what to do and need to implement it quickly and efficiently, let Sonnet execute. 80-90% of daily development tasks should use Sonnet.

Opus vs Sonnet Combination Strategy in Claude Code

In Claude Code, flexibly switching between Opus and Sonnet is key to improving efficiency.

Claude Code Model Switching Commands

# Switch to Opus (reasoning mode)
/model opus
# Or full model name
/model claude-opus-4-5-20251101

# Switch to Sonnet (execution mode)
/model sonnet
# Or full model name
/model claude-sonnet-4-5-20250929

# View current model
/model

Claude Code Best Combination Workflow

Recommended workflow:

1. Start session (default Sonnet)
   $ claude --model sonnet

2. Switch to Opus when encountering complex problems
   > /model opus
   > Help me analyze the architecture issues of this system and design a refactoring plan

3. Switch back to Sonnet for execution after plan confirmation
   > /model sonnet
   > Following the above plan, start refactoring the src/api/ directory

4. Use Opus again for code review
   > /model opus
   > Review the recent changes and check for any security issues

Claude Code opusplan Hybrid Mode

Claude Code provides an intelligent hybrid mode—opusplan:

# Use opusplan mode
/model opusplan

How this mode works:

• Planning phase: Automatically uses Opus for architecture design and decision-making
• Execution phase: Automatically switches to Sonnet for code implementation

This is the officially recommended hassle-free solution, suitable for users who don't want to switch manually.

Claude Code Cost Optimization Results

Practical experience: As one developer aptly summarized—"Haiku for preparation, Sonnet for development, Opus for review." This combination works best in actual projects.

Opus vs Sonnet Combination in API Calls

In API scenarios, you can also flexibly combine the two models.

API Call Example

import openai

client = openai.OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://vip.apiyi.com/v1"
)

def ask_opus(prompt: str) -> str:
    """Use Opus for complex reasoning"""
    response = client.chat.completions.create(
        model="claude-opus-4-5-20251101",
        messages=[{"role": "user", "content": prompt}],
        max_tokens=4000
    )
    return response.choices[0].message.content

def ask_sonnet(prompt: str) -> str:
    """Use Sonnet for fast execution"""
    response = client.chat.completions.create(
        model="claude-sonnet-4-5-20250929",
        messages=[{"role": "user", "content": prompt}],
        max_tokens=4000
    )
    return response.choices[0].message.content

# Practical application: Plan with Opus first, then execute with Sonnet
plan = ask_opus("Analyze this requirement and design a technical solution: {requirement description}")
code = ask_sonnet(f"Generate code according to the following plan:\n{plan}\n\nRequirement: Generate complete runnable code")

import openai
from enum import Enum
from typing import Optional, List, Dict

class ModelType(Enum):
    OPUS = "claude-opus-4-5-20251101"    # Reasoning and thinking
    SONNET = "claude-sonnet-4-5-20250929" # Execution and implementation

class ClaudeClient:
    def __init__(self, api_key: str):
        self.client = openai.OpenAI(
            api_key=api_key,
            base_url="https://vip.apiyi.com/v1"
        )

    def chat(
        self,
        messages: List[Dict],
        model_type: ModelType = ModelType.SONNET,
        max_tokens: int = 4000,
        temperature: float = 0.7
    ) -> str:
        """
        Unified chat interface

        Args:
            messages: List of conversation messages
            model_type: Model type, default Sonnet
            max_tokens: Maximum output tokens
            temperature: Temperature parameter
        """
        response = self.client.chat.completions.create(
            model=model_type.value,
            messages=messages,
            max_tokens=max_tokens,
            temperature=temperature
        )
        return response.choices[0].message.content

    def think(self, prompt: str) -> str:
        """Use Opus for deep thinking"""
        return self.chat(
            messages=[{"role": "user", "content": prompt}],
            model_type=ModelType.OPUS,
            temperature=0.5  # Lower temperature for reasoning tasks
        )

    def execute(self, prompt: str) -> str:
        """Use Sonnet for fast execution"""
        return self.chat(
            messages=[{"role": "user", "content": prompt}],
            model_type=ModelType.SONNET,
            temperature=0.7
        )

    def plan_and_execute(self, task: str) -> Dict[str, str]:
        """Plan-Execute pipeline"""
        # Step 1: Opus planning
        plan = self.think(f"As a technical expert, analyze the following task and develop a detailed execution plan:\n{task}")

        # Step 2: Sonnet execution
        result = self.execute(f"Execute the task according to the following plan and generate specific code:\n{plan}")

        return {"plan": plan, "result": result}

# Usage example
client = ClaudeClient("YOUR_API_KEY")

# Individual use
analysis = client.think("Analyze the architectural differences between React and Vue")
code = client.execute("Write a quicksort algorithm in Python")

# Plan-Execute pipeline
output = client.plan_and_execute("Develop a user authentication system")
print(output["plan"])   # View plan
print(output["result"]) # View code

Platform recommendation: Through APIYI apiyi.com, you can uniformly call Claude Opus 4.5 and Sonnet 4.5, with free test credits and pay-as-you-go pricing, suitable for development scenarios that require flexible model switching.

FAQ

Summary

Core selection strategy for Claude Opus 4.5 vs Sonnet 4.5:

1. Use Opus for reasoning: Architecture design, security audits, complex reasoning, important decisions
2. Use Sonnet for execution: Daily coding, code generation, documentation writing, routine debugging
3. Smart combination saves costs: Flexible switching can save 60-80% in costs
4. Quick switching in Claude Code: /model opus and /model sonnet for instant switching

Remember this principle: Opus is responsible for thinking it through, Sonnet is responsible for getting it done.

Through APIYi (apiyi.com), you can call both models through a unified interface, with support for free testing and flexible pay-as-you-go pricing.

Author: Technical Team
Technical Discussion: Feel free to share your Opus/Sonnet combination experiences in the comments. For more AI development resources, visit APIYi apiyi.com

References:

• Anthropic – Introducing Claude Opus 4.5: anthropic.com
• ClaudeLog – Claude Sonnet 4.5 vs Opus for Claude Code: claudelog.com
• LLM Stats – Claude Opus 4.5 vs Sonnet 4.5: llm-stats.com
• Claude Code Docs – Model Configuration: code.claude.com