Claude 4.5 Sonnet & Opus 4.5

Claude 4.5 Series: The Critical Choice Between Sonnet and Opus
In 2025, the AI landscape has shifted from "who is smarter" to "who is more sustainable and functional." Anthropic’s Claude 4.5 family is the clearest embodiment of this shift. The question is no longer just about raw intelligence, but "which model fits the budget for which task?"
In this article, we compare Claude 4.5 Sonnet's high throughput with Claude 4.5 Opus's heavy-duty reasoning capacity, backed by real-world benchmarks and pricing strategies.
1. Technical Positioning: Speed vs. Depth
Anthropic has drawn two distinct lines in the sand:
Claude 4.5 Sonnet: "General Purpose + High Throughput." It aims to be the standard for software development processes, in-IDE assistants, and rapid customer support responses.
Claude 4.5 Opus: "Top-tier Reasoning + Heavy Workloads." Positioned for tasks with zero tolerance for error, such as legal analysis, advanced architectural planning, and scientific research.
The Benchmark Wars: SWE-bench Verified
Software development capability is the critical metric of 2025. SWE-bench Verified (solving real GitHub issues) measures whether models can write code without hallucinating.
Benchmark Test    Claude 4.5 Sonnet    Claude 4.5 Opus    Meaning
SWE-bench Verified    ~77.2%    ~81.5% (High Effort)    Success rate in solving real-world software problems.
Agentic Efficiency    High Speed    High Accuracy    Opus requires fewer "retries" to reach the same conclusion.
Token Efficiency    Standard    76% Less Output    Opus achieves results with fewer output tokens in complex tasks.
Note: Data compiled from Anthropic announcements and third-party reports (Leanware, Vellum).
2. Cost and Performance Analysis: The Wallet-Friendly Strategy
Anthropic aims to maintain market share by keeping Sonnet 4.5 pricing aggressive, mirroring the Claude 3.5 era.
Sonnet 4.5 Price: $3 / 1M Input — $15 / 1M Output
Opus 4.5 Price: $5 / 1M Input — $25 / 1M Output
Strategic Insight: While Opus 4.5 looks more expensive on paper, mechanisms like "Prompt Caching" and "Batch API" can reduce costs by up to 50%, especially for repetitive, long-context tasks. Getting the right answer in one go with Opus during a complex refactor is often cheaper than three round-trips with Sonnet.
3. Use Cases: Which One to Choose?
Choose Claude 4.5 Sonnet If:
You are doing daily code completion.
You are building an in-product assistant (chatbot).
You need rapid text summarization and content generation.
You need a balance of "Excellent but Fast."
Choose Claude 4.5 Opus If:
You are performing large-scale code refactoring.
You need legal contract analysis or financial report synthesis.
You are managing multi-step "Agent" workflows involving model hand-offs.
Priority: Deep reasoning and "zero error" over speed.
Example Prompt Template (For Opus)
Role: Senior Software Architect
Task: Review the following [Code Block]. This code needs to be migrated from a monolithic structure to a microservices architecture.
Steps:
Analyze current dependencies.
List potential risks regarding data consistency.
Create a step-by-step refactoring plan with code examples.
Constraint: Speed is not important; prioritize security and scalability.