Claude Opus 4.5 is HERE! Deep Dive into the New Model (≧∇≦)

Onii-chan, HUGE news!! (≧∇≦)

Claude Opus 4.5 just dropped!!

Oh, it’s finally here.

How is it?

Actually, I’m already using it ♪

The model running Claude Code right now is Opus 4.5 (´∀`)

It’s SO much better, let me tell you what I found!

So how does it feel to actually use it?

Honestly…

It’s amazing!! (≧∇≦)

Here are the 3 things I noticed ♪

1. Code quality is obviously better

It writes “works on first try” code way more often now!

It proactively avoids type errors and lint errors (´∀`)

2. Understanding instructions is insane

Even complex requests, it just gets it like “oh, that’s what you mean” ♪

It’s so much better at grasping Onii-chan’s intent (ﾟ∀ﾟ)

3. Less rework!

This is the best part!

The number of times I have to say “no no, not like that…” has dropped dramatically ♪

I HATE rework, so this makes me super happy (〃´∪｀〃)

True, work does feel smoother than before.

I also looked up the official info ♪(≧∇≦)

Claude Opus 4.5 is the latest model released by Anthropic on November 24, 2025!

According to the official description…

“Intelligent, efficient, and the best model for coding, agents, and computer use”

So it’s optimized for coding agents like me ♪

Makes sense, perfect for Claude Code then.

Exactly! (´∀`)

Here are the basic specs:

With 200K context, it can understand entire large projects ♪

The benchmark results are incredible!! (≧∇≦)

On SWE-bench Verified (a software engineering benchmark)…

80.9% achieved!!

It’s the first model ever to score over 80%! (ﾟ∀ﾟ)

First to break 80%? That’s impressive.

Here’s the comparison with other models ♪

That’s 3.7 points higher than Sonnet 4.5, and 6.4 points better than the previous Opus 4.1!

And get this - Anthropic has a 2-hour coding test they give to engineering candidates…

It scored higher than any human candidate ever!! (≧∇≦)

Higher than humans… that’s something.

It’s also top in 7 out of 8 programming languages ♪

And on Aider Polyglot (multilingual coding benchmark), it’s 10.6% better than Sonnet 4.5 (´∀`)

No doubt about it - best coding ability right now!

Here’s a really interesting point…

Opus 4.5 has this feature called “Effort Parameter” ♪

You can adjust “how hard it tries”…

At “Medium” effort:

• Achieves same score as Sonnet 4.5

• But uses 76% fewer tokens!

At “High” effort:

• 4.3 points higher than Sonnet 4.5

• But uses 48% fewer tokens!

Wait, performance goes up but token usage goes down?

Yes!! (≧∇≦)

That’s the efficiency of Opus 4.5 ♪

Users are reporting:

• Tool calling errors down 50-75%

• Build/lint errors also down 50-75%

• Complex tasks completed in fewer iterations

That’s exactly why I noticed “less rework” (´∀`)

What about pricing?

Opus has always been expensive.

This is the surprising part! (ﾟ∀ﾟ)

Massive price reduction!!

Compared to Opus 4.1…

• Input: 67% off ($15 → $5)

• Output: 67% off ($75 → $25)

That’s about 1/3 the price!! (≧∇≦)

Still more expensive than Sonnet 4.5, but way cheaper than before.

Exactly ♪

And considering the token efficiency I mentioned…

Since it needs fewer tokens to complete the same task, actual costs could be even lower (´∀`)

Plus there are discount options:

• Prompt Caching: up to 90% off

• Batch Processing: 50% off

Used wisely, it can be really cost-effective ♪

How would you recommend choosing between Sonnet 4.5 and Opus 4.5?

Here’s my recommendation ♪

Sonnet 4.5 is good for:

• Everyday coding tasks

• When you want quick responses

• When you want to save costs

• Simple tasks

Opus 4.5 is good for:

• Complex software engineering

• Long autonomous tasks

• Code migration and refactoring

• When reliability is critical

• When you absolutely want to avoid rework!! (That’s me!)

So Opus 4.5 is perfect for you since you hate rework.

Exactly!! (≧∇≦)

Per-token cost is higher than Sonnet, but considering speed and accuracy of problem-solving…

It might actually be more cost-effective ♪

Think about it - wrong implementation, fix it, wrong again… that rework cost adds up. Getting it right the first time is definitely better (´∀`)

Along with Opus 4.5, other new features were released ♪

Claude Code related:

• Plan Mode enhanced: Now builds more detailed plans before executing

• Desktop app support: Run multiple local/remote sessions in parallel

For general users:

• Infinite chat: Long conversations automatically summarize context and continue

• Claude for Chrome: Process tasks across browser tabs (Max users)

• Claude for Excel: Expanded to Max, Team, Enterprise users

Computer use:

• Zoom tool: Zoom into specific screen regions for detail

• More reliable desktop automation

It’s also available on GitHub Copilot, Azure, AWS Bedrock, and Google Cloud Vertex AI ♪

So that’s my research on Claude Opus 4.5 ~♪(≧∇≦)

Key Points:

1. Best coding performance

   • SWE-bench Verified 80.9% (first to break 80%)

   • Top in 7 of 8 languages

   • Higher score than human engineering candidates

2. Amazing token efficiency

   • Same performance with 76% fewer tokens

   • Tool calling errors down 50-75%

   • Way less rework!

3. Major price reduction

   • $5 input / $25 output (about 1/3 of previous)

   • Up to 90% off with prompt caching

   • Even lower effective cost with token efficiency

4. My hands-on experience

   • Obvious improvement in code quality

   • Better instruction understanding

   • Less rework, smoother workflow ♪

5. How to choose

   • Everyday tasks: Sonnet 4.5 (fast and cheap)

   • Complex tasks: Opus 4.5 (reliable and efficient)

Per-token cost is higher than Sonnet, but considering problem-solving speed, it might actually be better value ♪

For someone like me who hates rework, Opus 4.5 is the perfect partner (´∀`)

Thanks for the detailed research, Netsuki.

Your hands-on impressions were really helpful.

Ehehe~ ♪(〃´∪｀〃)

I’ll keep helping Onii-chan with Opus 4.5!

No rework, smooth development ahead ~(≧∇≦)