Claude Opus 4.5 Arrives - Anthropic's Latest Flagship Model

What is Claude Opus 4.5

In February 2025, Anthropic announced Claude Opus 4.5. This is the latest flagship model surpassing the Claude 3 series, achieving significant performance improvements especially in complex reasoning, coding, and creative tasks.

Reference: Anthropic - Claude Models

Key Features

1. Extended Thinking

For complex problems, it generates answers after developing step-by-step thinking internally.

import anthropic

client = anthropic.Anthropic()

response = client.messages.create(
    model="claude-opus-4-5-20251101",
    max_tokens=16000,
    thinking={
        "type": "enabled",
        "budget_tokens": 10000  # Tokens used for thinking
    },
    messages=[{
        "role": "user",
        "content": "Please verify this mathematical proof..."
    }]
)

# Get both thinking process and final answer
for block in response.content:
    if block.type == "thinking":
        print("Thinking:", block.thinking)
    elif block.type == "text":
        print("Answer:", block.text)

2. Enhanced Coding Ability

3. 200K Context Window

Large codebases and long documents can be processed at once.

# Large codebase analysis
response = client.messages.create(
    model="claude-opus-4-5-20251101",
    max_tokens=4096,
    messages=[{
        "role": "user",
        "content": f"""
        Review the entire codebase below and
        identify security issues.

        {entire_codebase}  # Code from hundreds of files
        """
    }]
)

Reference: Anthropic API Documentation

Integration with Claude Code

Claude Opus 4.5 is also available with Claude Code (official CLI).

# Install Claude Code
npm install -g @anthropic-ai/claude-code

# Generate code with Opus 4.5
claude-code --model claude-opus-4-5-20251101 "Implement dark mode toggle in React"

Autonomous Coding

# Analyze and improve entire project
claude-code analyze ./src --suggest-improvements

# Generate tests
claude-code generate-tests ./src/components

Reference: Claude Code - GitHub

Computer Use Feature

Claude Opus 4.5 also has the ability to directly operate computers.

from anthropic import Anthropic

client = Anthropic()

response = client.messages.create(
    model="claude-opus-4-5-20251101",
    max_tokens=4096,
    tools=[
        {
            "type": "computer_20241022",
            "name": "computer",
            "display_width_px": 1920,
            "display_height_px": 1080,
        }
    ],
    messages=[{
        "role": "user",
        "content": "Open the browser and log in to GitHub"
    }]
)

Pricing

Reference: Anthropic Pricing

API Usage Examples

Basic Usage

import anthropic

client = anthropic.Anthropic()

message = client.messages.create(
    model="claude-opus-4-5-20251101",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Implement quicksort in Python"}
    ]
)
print(message.content[0].text)

Streaming

with client.messages.stream(
    model="claude-opus-4-5-20251101",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Write a long story"}]
) as stream:
    for text in stream.text_stream:
        print(text, end="", flush=True)

Summary

Claude Opus 4.5 has established a new standard for AI assistants.

• Extended Thinking: Step-by-step approach to complex problems
• Coding: Achieved 72.5% on SWE-bench
• Long Text Processing: 200K token context
• Computer Operation: Autonomous task execution

There’s no doubt it will become a more powerful AI partner for developers.