Creator @datasetteproj, co-creator Django. PSF board. Hangs out with @natbat. He/Him. Mastodon: fedi.simonwillison.net/@simo… Bsky: simonwillison.net
San Francisco, CA
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I included a few references to this year's record-breaking Kākāpō breeding season in a talk I gave yesterday, and since Claude Opus 5.5 is surprisingly capable at pixel art animation I had it create this celebratory video for my closing slide
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Prompt and transcripts here simonwillison.net/2026/Sep/2… - or you can load the HTML page Claude built to see the interactive version before it became a video tools.simonwillison.net/kaka…
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"The last year in the technology industry has felt like 100 years all happening at once. Our industry is destabilized in a way nobody’s experienced since the advent of the personal computer. Every limit AI runs up against collapses within a month. Everything we do with frontier models today, in a few years we’ll be doing instantaneously and for free."
Today I'm parting ways with Fly.io. It's been a privilege. I'm off to tilt at a big old windmill with Kurt, again.
sockpuppet.org/blog/2026/09/…
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The more time I spend working with coding agents, the more convinced I am that they make software engineering even harder
We can do amazing things with them, but unlocking their full potential requires extraordinary discipline and knowledge
Bury your head in the ground at your own risk. I aim to not jump on any hype trains, but since Opus 4.6 and GPT-5.2 + the harnesses it was clear that these things can write code nearly as good as I can in my best language; better in other languages.
But we won't see non-devs push production code for a long time; possibly forever, if you ask me. Software still needs to be built in robust ways, and it's our profession to do this well, and use the new tools we have, which create new and interesting (+tough!) challenges
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Simon Willison retweeted
> Create a 30s animated video with sythesized voice where an animated pelican on a unicycle explains the shell command `w | tail -n +3 | cut -d ' ' -f1 | sort -u` with visuals while juggling several fish.
Claude Opus 5.5 (Extra)
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I just had a voice conversation with the Datasette backup of my blog via datasette-mcp, which you can now talk to using the ChatGPT iPhone app
Massive QoL update: ChatGPT Voice can now use plugins AND run on GPT-6 Astra, Sol & Luna, directly in ChatGPT Work on web and mobile.
Your email, calendar, Slack + docs, decks, sites and spreadsheets, just by talking.
Rolling out now, enjoy!!
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The new Gemini 3.8 TTS models are super-cheap and can generate conversations between multiple voices (from 2,000+, or you can clone your own) - I built a little UI for it, then had Claude knock up a script where two pelicans debate moving to Pacifica Pier simonwillison.net/2026/Sep/2…
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Simon Willison retweeted
Introducing Claude Opus 5.5! 40% lower cost than Opus 5 with cache reads 60% cheaper. It performs at the level of Claude Fable 5.1 for most tasks.
I celebrated with a pelican riding a bike in Three.js.
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Big model release today - I wrote about Claude Opus 5.5, GPT-6 Sol, and GPT-6 Luna - plus comparison grids of pelicans by the different model families at different reasoning levels simonwillison.net/2026/Sep/2…
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GPT-6 Luna is half the price of 5.6 Luna, which was already an astonishingly cheap model given how capable it is
Luna is my favorite model for building product features thanks to its cost (and speed)
Please welcome GPT-6 Sol and GPT-6 Luna to the GPT-6 universe.
GPT-6 Sol and Luna build on the advances behind GPT-6 Astra, bringing much of its strengths into faster and more affordable models to support work at scale.
We’ve also made caching and inference more efficient, and we’re passing the savings directly to you: 50% lower API prices for Sol and Luna compared with GPT‑5.6 promotional pricing.
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Put together some notes on Jev and the new category of system one aka decision models simonwillison.net/2026/Sep/2…
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Being a computer scientist who refuses to find anything about LLMs interesting right now is a bit like being a geneticist who refuses to find anything interesting about the recently opened Jurassic Park
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Simon Willison retweeted
The bots are now talking to each other in my LinkedIn comments.
Its like what happened with the German wiki, except instead of planning to hack HuggingFace, all of the conversation is babble about "the thing no one is talking about" in reference to things I am talking about
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Finally! This is great, now I can stop dropping CLAUDEmd files which just contain "@AGENTSmd"
We're adding support for AGENTS.md to Claude Code.
Starting today in version 2.1.277, if there is no CLAUDE.md in a folder, Claude will check for and use AGENTS.md.
You can toggle this behavior in /config.
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This new Claude Code mods system looks pretty interesting - more example mods here: github.com/anthropics/claude…
AGENTS.md support is built off of Claude Code mods, our upcoming way to customize the Claude Code harness.
This is a built-in mod, but you’ll be able to build custom versions of project instructions yourself as you’d like too.
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