# Sonnet 5 review: I ran 64 generations to find out if it's worth it

> Source: <https://www.lennysnewsletter.com/p/sonnet-5-review-i-ran-64-generations>
> Published: 2026-06-30 23:22:23+00:00

I’ve been testing every major frontier model release since the start of the year, and when Anthropic dropped Sonnet 5, I wanted more than a vibe check. I got tired of one-off tests I couldn’t repeat or compare over time, so I built something better: the How I AI Bench, a repeatable eval harness I constructed live using Claude Code while recording this episode. I ran Sonnet 5 blind against four other frontier models (Sonnet 4.6, Opus 4.8, GPT-5.5, and Gemini 3 Pro) across PRD quality, prototype generation, agentic task completion, and agent personality. The results were not what I expected.

**Listen or watch on YouTube, Spotify, or Apple Podcasts**

### What you’ll learn:

What Anthropic claims Sonnet 5 improves over Sonnet 4.6, and where the benchmark data actually backs that up

How I built the How I AI Bench in under 45 minutes using Claude Code, starting from my own stored session history

Why I combined human vibe scoring (70%) with LLM as judge scoring (30%) instead of trusting either alone

How to set up a local HTML scoring page so you can rate AI outputs on gut feel and export those scores as JSON

Which model I recommend for PRDs, which for complex prototypes, and which for chatting with an agent daily

### Brought to you by:

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### In this episode, we cover:

([00:00](https://www.youtube.com/watch?v=yJ-1LB2hF-Q)) Sonnet 5 is out

([01:55](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=115s)) What Anthropic claims

([04:02](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=242s)) Why I’m done with one-off vibe checks

([05:05](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=305s)) Building the How I AI Bench live with Claude Code

([07:42](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=462s)) The scoring system

([10:43](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=643s)) Agent voice eval

([11:57](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=717s)) Quick recap

([13:58](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=838s)) Results: The How I AI index leaderboard

([21:21](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=1281s)) What I’m improving for the next run

([22:16](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=1336s)) Generating a Claire-weighted index

([23:53](https://www.youtube.com/watch?v=yJ-1LB2hF-Q&t=1433s)) Model-by-task recommendations

### Tools referenced:

• Claude Sonnet 5: [https://www.anthropic.com/news/claude-sonnet-5](https://www.anthropic.com/news/claude-sonnet-5)

• Claude Opus 4.8: [https://www.anthropic.com/news/claude-opus-4-8](https://www.anthropic.com/news/claude-opus-4-8)

• GPT-5.5 (OpenAI): [https://openai.com/index/introducing-gpt-5-5/](https://openai.com/index/introducing-gpt-5-5/)

• Gemini 3 Pro (Google DeepMind): [https://deepmind.google/models/gemini/pro/](https://deepmind.google/models/gemini/pro/)

• Cursor: [https://www.cursor.com/](https://www.cursor.com/)

### Other references:

• SWE-bench Pro (agentic coding benchmark referenced): [https://www.swebench.com/](https://www.swebench.com/)

### Where to find Claire Vo:

ChatPRD: [https://www.chatprd.ai/](https://www.chatprd.ai/)

Website: [https://clairevo.com/](https://clairevo.com/)

LinkedIn: [https://www.linkedin.com/in/clairevo/](https://www.linkedin.com/in/clairevo/)

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