Simon Willison(@simonw)

OK, "using Fourier epicycles" is a new twist

Simon Willison (@simonw) — Tue, 13 Oct 2026 23:31:09 GMT

OK, "using Fourier epicycles" is a new twist

fofr@fofrAI

Argon has this amazing natural understanding of the world. It can do so many things from first principles.

Here's a pelican riding a bike, using fourier epicycles. 

Video made by Argon.
Time-synced Lyria 3.5 music prompted by Argon.

Your browser does not support the video tag.

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Shared some notes on Python 3.15, using it with uv, and features from Python 3.11 I'm excited to use...

Simon Willison (@simonw) — Mon, 12 Oct 2026 18:22:02 GMT

Shared some notes on Python 3.15, using it with uv, and features from Python 3.11 I'm excited to use now that 3.10 is no longer the minimum supported version for my own projects simonwillison.net/2026/Oct/12/py…

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@RomanHotsiy Current iPhones are waterproof enough that I use mine in the shower on voice mode all t...

Simon Willison (@simonw) — Sat, 10 Oct 2026 15:30:36 GMT

@RomanHotsiy Current iPhones are waterproof enough that I use mine in the shower on voice mode all the time

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I like Qwen3.5-35B-A3B for this, wondering what else is out there that might be a bit more recent an...

Simon Willison (@simonw) — Fri, 09 Oct 2026 17:21:37 GMT

I like Qwen3.5-35B-A3B for this, wondering what else is out there that might be a bit more recent and pack a little more of a punch

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What's the best open weight Mixture-of-Experts LLM for coding that fits in less than 60GB of RAM? I...

Simon Willison (@simonw) — Fri, 09 Oct 2026 17:20:12 GMT

What's the best open weight Mixture-of-Experts LLM for coding that fits in less than 60GB of RAM?

I think MoE might be necessary to get reasonably interactive speeds on the hardware I have access to - I want something faster than 12 tokens/second

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Example prompt:

Simon Willison (@simonw) — Fri, 09 Oct 2026 13:18:30 GMT

Example prompt:

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I built a new feature for my blog entirely by voice with Codex Desktop, while I was cooking dinner h...

Simon Willison (@simonw) — Fri, 09 Oct 2026 13:16:10 GMT

I built a new feature for my blog entirely by voice with Codex Desktop, while I was cooking dinner simonwillison.net/2026/Oct/9/bui…

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Admittedly I guess this is a pretty incredible troll targeted at people who say "it shouldn't be cal...

Simon Willison (@simonw) — Fri, 09 Oct 2026 00:01:31 GMT

Admittedly I guess this is a pretty incredible troll targeted at people who say "it shouldn't be called artificial intelligent because it's not actually intelligent"

Do they now feel obliged to defend the old name against the new one?

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Note that their press release from when he pleaded guilty back on March 19th used "North Carolina Ma...

Simon Willison (@simonw) — Thu, 08 Oct 2026 23:58:36 GMT

Note that their press release from when he pleaded guilty back on March 19th used "North Carolina Man Pleads Guilty To Music Streaming Fraud Aided By Artificial Intelligence" because of course it did justice.gov/usao-sdny/pr/n…

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This tweet inspired by the justice department headline from October 6th: "North Carolina Man Sentenc...

Simon Willison (@simonw) — Thu, 08 Oct 2026 23:58:08 GMT

This tweet inspired by the justice department headline from October 6th: "North Carolina Man Sentenced To 18 Months In Prison For Super Intelligence-Assisted Music Streaming Fraud" justice.gov/usao-sdny/pr/n…

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This "Super Intelligence" thing is just so, so, so stupid I can't even

Simon Willison (@simonw) — Thu, 08 Oct 2026 23:57:30 GMT

This "Super Intelligence" thing is just so, so, so stupid

I can't even

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AWS have a new open source sandbox too, must be something in the air

Simon Willison (@simonw) — Thu, 08 Oct 2026 15:56:30 GMT

AWS have a new open source sandbox too, must be something in the air

Marc Brooker@MarcJBrooker

Today we're announcing Strands Box, our open source sandbox for developers building AI agents.

New blog post from me, on the Strands blog: strandsagents.com/blog/strands-b…

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Related new project from Microsoft is Quicksand, a Python library that bundles QEMU and uses it to r...

Simon Willison (@simonw) — Thu, 08 Oct 2026 15:29:46 GMT

Related new project from Microsoft is Quicksand, a Python library that bundles QEMU and uses it to run eg an Alpine Linux container - this one is really neat, I've tried it on macOS and Windows and Linux: github.com/microsoft/quic…

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New open source cross-platform (Windows, macOS, Linux) sandboxing library from Microsoft - looks ver...

Simon Willison (@simonw) — Thu, 08 Oct 2026 15:23:37 GMT

New open source cross-platform (Windows, macOS, Linux) sandboxing library from Microsoft - looks very promising, uses processcontainer/bubblewrap/seatbelt under the hood github.com/microsoft/mxc

Kyle Daigle@kdaigle

If you’ve been struggling with a multitude of sandboxes for agents, MxC is a sandbox solution that works across Windows, Linux, and macOS. 

A real platform opportunity for developers across the ecosystem. Process, session, micro VM, and deep integration into agent ID on Windows.

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Haiku 5.5 is SO MUCH better at drawing pelicans riding bicycles than Claude Haiku 4.5, released almo...

Simon Willison (@simonw) — Wed, 07 Oct 2026 21:00:32 GMT

Haiku 5.5 is SO MUCH better at drawing pelicans riding bicycles than Claude Haiku 4.5, released almost a year ago and costing 10x more. Here's Haiku 4.5's attempt:

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Pelicans and a bunch of notes on the pricing of the new Claude Haiku 5.5 https://t.co/F3Sob8WvsG

Simon Willison (@simonw) — Wed, 07 Oct 2026 20:58:38 GMT

Pelicans and a bunch of notes on the pricing of the new Claude Haiku 5.5 simonwillison.net/2026/Oct/7/cla…

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I released an LLM plugin for sending prompts to OpenAI's new Jev-clone decision model that's based o...

Simon Willison (@simonw) — Wed, 07 Oct 2026 00:32:42 GMT

I released an LLM plugin for sending prompts to OpenAI's new Jev-clone decision model that's based on GPT-6 Luna simonwillison.net/2026/Oct/6/llm…

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One thing I'd LOVE to understand is how Claude "knows" what the music from Secret of Monkey Island s...

Simon Willison (@simonw) — Tue, 06 Oct 2026 23:33:28 GMT

One thing I'd LOVE to understand is how Claude "knows" what the music from Secret of Monkey Island sounds like

Maybe Anthropic crawled a whole bunch of online music discussion forums with text-based renditions of classic game music?

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Here's a benchmark that uses Lilypond https://t.co/6yWiT7tG9e

Simon Willison (@simonw) — Tue, 06 Oct 2026 17:00:55 GMT

Here's a benchmark that uses Lilypond x.com/aug5thmusic/st…

Auggie@aug5thmusic

GPT-6 Astra has the best result yet on the Bach Benchmark. Its chorale contains no voice-leading errors, and its harmonic palette is sophisticated enough to include a Neapolitan sixth chord. More importantly, it is the first model to ever write passing tones on this benchmark, a significant leap in musical understanding.

Extra High effort. Prompt below:
“In LilyPond (version 2.24), write a 4-part chorale in the style of Bach, 3/4 time, G minor. Use two staves -- soprano and alto on the top staff, tenor and bass on the bottom staff. Respond with only the code block.”

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Anyone know when the models started being able to compose competent music? I had Opus 5.5 "write som...

Simon Willison (@simonw) — Tue, 06 Oct 2026 15:40:03 GMT

Anyone know when the models started being able to compose competent music? I had Opus 5.5 "write some computer game music for me" and the results were much better than I had expected
simonwillison.net/2026/Oct/6/scr…

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Mistral can pelican now! https://t.co/Mvtss5e5ay

Simon Willison (@simonw) — Tue, 06 Oct 2026 14:35:18 GMT

Mistral can pelican now! tools.simonwillison.net/markdown-svg-r…

Mistral AI@MistralAI

Meet Mistral Large 4, aka Le Chonk. 

• 1T parameters, natively multimodal. 49B active.
It is the best open weights model from US or Europe on aggregated benchmarks.
• State-of-the-art on critical workloads, including cyber defense, manufacturing and finance and it surpasses closed frontier models on visual grounding.
• Forged in Europe end-to-end and is deployable from Europe via our own Mistral Cloud infrastructure.
• Available to all via API today. Working with cybersecurity partners privately.

Open weights release end of October.

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I re-ran an experiment @colin_fraser ran against GPT-4o a while back to see how good it was at addin...

Simon Willison (@simonw) — Mon, 05 Oct 2026 17:19:20 GMT

I re-ran an experiment @colin_fraser ran against GPT-4o a while back to see how good it was at adding long numbers, only this time I tried Qwen 3.8 27B running locally in both reasoning and non-reasoning modes simonwillison.net/2026/Oct/4/qwe…

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Just published this post about how we’re going to need default hard budget caps on pretty much every...

Simon Willison (@simonw) — Sat, 03 Oct 2026 23:35:55 GMT

Just published this post about how we’re going to need default hard budget caps on pretty much everything simonwillison.net/2026/Oct/3/def…

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Now that we've had a few days with it, how are people differentiating between Dot and regular ChatGP...

Simon Willison (@simonw) — Sat, 03 Oct 2026 21:43:53 GMT

Now that we've had a few days with it, how are people differentiating between Dot and regular ChatGPT?

I'm having trouble deciding when I should prompt Dot vs using ChatGPT - my Dot seems to afford a single conversation, but I like controlling my context across multiple threads

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I'm at OpenAI's DevDay event in San Francisco today - as I have for the past three DevDay events, I'...

Simon Willison (@simonw) — Tue, 29 Sep 2026 16:54:44 GMT

I'm at OpenAI's DevDay event in San Francisco today - as I have for the past three DevDay events, I'm running a live blog where I'll be posting updates during the keynote, which starts in five minutes simonwillison.net/2026/Sep/29/op…

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More on Sonnet 5.5 https://t.co/efd6KqvkqU

Simon Willison (@simonw) — Tue, 29 Sep 2026 03:24:37 GMT

More on Sonnet 5.5 simonwillison.net/2026/Sep/28/cl…

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The most important thing about Sonnet 5.5 is that it's now the model that powers the free tier on ht...

Simon Willison (@simonw) — Mon, 28 Sep 2026 21:18:41 GMT

The most important thing about Sonnet 5.5 is that it's now the model that powers the free tier on claude.ai - so all of this stuff can be done by free users

ChatGPT's free tier is still GPT-5.6 Luna, which is a lot less capable

Claude@claudeai

A thread of early experiments with Claude Sonnet 5.5.

A fall foliage simulator by @_re_pete, made with Sonnet 5 vs Sonnet 5.5.

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@WeAreDevs (The full talk also covers New Zealand’s Kākāpō parrot breeding season, probably the best...

Simon Willison (@simonw) — Mon, 28 Sep 2026 17:56:46 GMT

@WeAreDevs (The full talk also covers New Zealand’s Kākāpō parrot breeding season, probably the best news of 2026)

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@WeAreDevs And my closing thought on how this stuff impacts our lives as software engineers, with a ...

Simon Willison (@simonw) — Mon, 28 Sep 2026 17:55:57 GMT

@WeAreDevs And my closing thought on how this stuff impacts our lives as software engineers, with a quote from cycling champion Greg LeMond

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@WeAreDevs Here's how I define "Fable class models" - first Claude Fable 5, now Claude Opus 5.5 and ...

Simon Willison (@simonw) — Mon, 28 Sep 2026 17:53:47 GMT

@WeAreDevs Here's how I define "Fable class models" - first Claude Fable 5, now Claude Opus 5.5 and GPT-Astra 6 and maybe GPT-5.6 Sol as well

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I've published detailed notes and an annotated transcript to accompany the video of the keynote I ga...

Simon Willison (@simonw) — Mon, 28 Sep 2026 17:51:39 GMT

I've published detailed notes and an annotated transcript to accompany the video of the keynote I gave at @WeAreDevs World Congress North America in San Jose on Friday - here's my rundown of everything that's happened with LLMs and agents in 2026 so far simonwillison.net/2026/Sep/27/20…

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Prompt and transcripts here https://t.co/QI1dIenQsW - or you can load the HTML page Claude built to ...

Simon Willison (@simonw) — Sun, 27 Sep 2026 00:19:59 GMT

Prompt and transcripts here simonwillison.net/2026/Sep/26/ka… - or you can load the HTML page Claude built to see the interactive version before it became a video tools.simonwillison.net/kakapo-party

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I included a few references to this year's record-breaking Kākāpō breeding season in a talk I gave y...

Simon Willison (@simonw) — Sun, 27 Sep 2026 00:18:13 GMT

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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@AndyMasley OK maybe I should play some new games

Simon Willison (@simonw) — Sat, 26 Sep 2026 15:13:26 GMT

@AndyMasley OK maybe I should play some new games

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"The last year in the technology industry has felt like 100 years all happening at once. Our industr...

Simon Willison (@simonw) — Sat, 26 Sep 2026 03:30:59 GMT

"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."

Thomas H. Ptacek@tqbf

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/2026/09/2…

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I'm on stage for the keynote in ten minutes time!

Simon Willison (@simonw) — Sat, 26 Sep 2026 00:21:55 GMT

I'm on stage for the keynote in ten minutes time!

WeAreDevelopers@WeAreDevs

Legendary programmer Simon Willison says he's never so much change happen so quickly as he has in 2026, and there's no sign of it stopping.

🎤 Don't miss his closing Keynote, Friday (Sept 25) on the Main Stage at 5.30pm!

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The more time I spend working with coding agents, the more convinced I am that they make software en...

Simon Willison (@simonw) — Fri, 25 Sep 2026 01:02:12 GMT

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

Gergely Orosz@GergelyOrosz

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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I just had a voice conversation with the Datasette backup of my blog via datasette-mcp, which you ca...

Simon Willison (@simonw) — Thu, 24 Sep 2026 00:22:32 GMT

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

Vaibhav (VB) Srivastav@reach_vb

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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Seems to cost less than 1 cent per minute of generated audio for Flash, and Flash-Lite is even cheap...

Simon Willison (@simonw) — Wed, 23 Sep 2026 20:45:37 GMT

Seems to cost less than 1 cent per minute of generated audio for Flash, and Flash-Lite is even cheaper than that

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The new Gemini 3.8 TTS models are super-cheap and can generate conversations between multiple voices...

Simon Willison (@simonw) — Wed, 23 Sep 2026 20:45:19 GMT

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/23/ge…

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Big model release today - I wrote about Claude Opus 5.5, GPT-6 Sol, and GPT-6 Luna - plus comparison...

Simon Willison (@simonw) — Tue, 22 Sep 2026 23:50:29 GMT

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/22/op…

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GPT-6 Luna is half the price of 5.6 Luna, which was already an astonishingly cheap model given how c...

Simon Willison (@simonw) — Tue, 22 Sep 2026 20:07:37 GMT

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)

OpenAI@OpenAI

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 https://t.co/E...

Simon Willison (@simonw) — Mon, 21 Sep 2026 23:16:26 GMT

Put together some notes on Jev and the new category of system one aka decision models simonwillison.net/2026/Sep/21/je…

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Skeptical geneticist: "pfft, it's just frog DNA. And they deliberately let them eat people for the m...

Simon Willison (@simonw) — Sat, 19 Sep 2026 14:10:57 GMT

Skeptical geneticist: "pfft, it's just frog DNA. And they deliberately let them eat people for the marketing."

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Dennis Nedry works for Irregular

Simon Willison (@simonw) — Sat, 19 Sep 2026 04:21:09 GMT

Dennis Nedry works for Irregular

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Being a computer scientist who refuses to find anything about LLMs interesting right now is a bit li...

Simon Willison (@simonw) — Fri, 18 Sep 2026 19:19:11 GMT

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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This new Claude Code mods system looks pretty interesting - more example mods here: https://t.co/muU...

Simon Willison (@simonw) — Fri, 18 Sep 2026 19:14:07 GMT

This new Claude Code mods system looks pretty interesting - more example mods here: github.com/anthropics/cla…

Thariq@trq212

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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Finally! This is great, now I can stop dropping CLAUDEmd files which just contain "@AGENTSmd"

Simon Willison (@simonw) — Fri, 18 Sep 2026 19:06:20 GMT

Finally! This is great, now I can stop dropping CLAUDEmd files which just contain "@AGENTSmd"

Thariq@trq212

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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TIL that 1988 classic Who Framed Roger Rabbit features a pelican riding a bicycle! https://t.co/FUgB...

Simon Willison (@simonw) — Fri, 18 Sep 2026 14:40:29 GMT

TIL that 1988 classic Who Framed Roger Rabbit features a pelican riding a bicycle! simonwillison.net/2026/Sep/18/th…

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