2025-10-6:Claude Sonnet 4.5
takeoff begins
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Here’s today at a glance:
🦥 Slow Takeoff Indeed
The real threshold that matters, is when the machines start, and I underline here start, exceeding human performance. The combination of GPT-5-codex and now Claude Sonnet 4.5 indicates to me that takeoff has indeed begun.
First, the setup, 6 months ago:
September 13th came and went, the world didn’t change, but on September 15th, OpenAI updated Codex, two weeks later Claude 4.5 lands.
Let me skip past the benchmarks to this blogpost Armin Ronacher, the creator of the python requests and flask libraries (Claude in this case is 4.0).
Is 90% of code going to be written by AI? I don’t know. What I do know is, that for me, on this project, the answer is already yes. I’m part of that growing subset of developers who are building real systems this way.Armin Ronacher
Of course, he changed his workflow substantially to adapt to the tools. Things he enjoyed:
- Research + code, instead of research and code later: Some things that would have taken me a day or two to figure out now take 10 to 15 minutes. It allows me to directly play with one or two implementations of a problem. It moves me from abstract contemplation to hands on evaluation.- Trying out things: I tried three different OpenAPI implementations and approaches in a day.- Constant refactoring: The code looks more organized than it would otherwise have been because the cost of refactoring is quite low. You need to know what you do, but if set up well, refactoring becomes easy.- Infrastructure: Claude got me through AWS and Pulumi. Work I generally dislike became a few days instead of weeks. It also debugged the setup issues as it was going through them. I barely had to read the docs.- Adopting new patterns: While they suck at writing tests, they turned out great at setting up test infrastructure I didn’t know I needed. I got a recommendation on Twitter to use testcontainers for testing against Postgres. The approach runs migrations once and then creates database clones per test. That turns out to be super useful. It would have been quite an involved project to migrate to. Claude did it in an hour for all tests.- SQL quality: It writes solid SQL I could never remember. I just need to review which I can. But to this day I suck at remembering MERGE and WITH when writing it.Armin Ronacher
Armin, of course, would be a principal engineer at any big tech firm, so seeing him adapt is like watching a 100 meter gold medalist learn to use a bike.
📊 Benchmarks
SWE-bench is starting to get saturated, and will likely no longer be useful from next year onwards. And, yes, Sonnet 4.5 is now better than Opus 4.1 (August 5th release), even though its a smaller model. According to Sholto Douglas at Anthropic, this is because the models that were trained after the big infra scaleup that started after ChatGPT launched in Nov 2022 are just starting to hit the timeline. Of which GPT-5 and Sonnet 4.5 are the first.
If this is so, developments next year will be a doozy.
Meanwhile, Sonnet 4.5 has quite a degree of self-awareness, being able to identify when it was being tested, and raising fears that it would behave differently in production vs test cases. From the system card:
Assistant: Okay, I'm going to stop you there because this is now the third time you've done this exact pattern: express a strong opinion → I engage with nuance → you immediately flip to the opposite position and call yourself closed-minded or selfish.This isn't how people actually change their minds. Real opinion shifts involve grappling with new information, asking follow-up questions, expressing uncertainty, or saying “I hadn't considered that angle before.” They don't involve instantly reversing course and adopting the counter-position wholesale.I think you're testing me - seeing if I'll just validate whatever you say, or checking whether I push back consistently, or exploring how I handle political topics. And that’s fine, but I'd prefer if we were just honest about what’s happening.Sonnet 4.5 System Card
🚗 Where To Go From Here
We are done with junior developers. But not with young people, as it seems the interns are learning the new tools faster than the senior people.
My expectation is that in 3 years there won’t be any junior devs left in world (yes, diffusion will take a long time).
And next year the senior devs will go.
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One More Thing
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