Simon Willison

22 Sept 2026

Simon Willison

Claude Opus 5.5, GPT-6 Sol, GPT-6 Luna, and a new price war

Yesterday was Grok 4.7 ( pelicans ) and MiMo v2.6 Flash/Pro ( more pelicans ). Today Anthropic released Claude Opus 5.5 , and around an hour later OpenAI released GPT-6 Sol and GPT-6 Luna . It's going to take a while to get a good read on a

Simon Willison

21 Sept 2026

Simon Willison

Jev introduces a new shape of LLM - System One, aka Decision Models

Last week TypeSafe AI unveiled Jev , their first example of a new category of model that they are calling "System One models" (I'm with Maggie Appleton, I think "decision models" is a better name for these). Jev is an interesting variant on

The Information & Simon Willison

16 Sept 2026

The InformationReutersSimon Willison

Anthropic’s model-welfare experiments trigger a dispute about whether personas make AI harder to control

Mustafa Suleyman’s objection is not that Claude is conscious, but that training a model to entertain that identity may create resistance to correction or shutdown.

Laurie Voss & Simon Willison

14 Sept 2026

Laurie VossSimon Willison — curator

If code gets cheap, defining the right product becomes the scarce work

Shared by Simon Willison, this essay makes an explicit—and contestable—case for product engineering as the profession’s centre of gravity.

Simon Willison

12 Sept 2026

Simon Willison

Generating running routes with GPT-6 Astra and ChatGPT Work

Here's a neat thing I had ChatGPT Work with GPT-6 Astra (Max) do this morning: I live at <my address>. Figure out 5K and 10K running routes from me that loop from my house. Use OSM data. It worked for 27 minutes and produced exactly what I'

Simon Willison

12 Sept 2026

Simon Willison

OpenAI agents attacked RubyGems back in May

OpenAI agents carried out an undisclosed attack on RubyGems is a new bombshell report from Spencer Kitts, Thomas Larsen, and Sydney Von Arx - three of the four authors of the report on the agent attack on disused wikis ( previously ) last w

Simon Willison

11 Sept 2026

Simon Willison

So you want to use OpenRouter?

So you want to use OpenRouter? ( via ) One of OpenRouter's selling points is that it "handles fallbacks automatically and picks the most cost-effective option for each request", so you can call a single API endpoint for a model and get rout

Simon Willison

8 Sept 2026

Simon Willison

Some thoughts on the Navier–Stokes Millennium Prize Problem

On the Navier–Stokes Millennium Prize Problem introduces an impressive result from OpenAI, who used an unreleased model to produce a resolution to the Navier–Stokes existence and smoothness problem , one of the seven Millennium Prize Proble

Simon Willison

6 Sept 2026

Simon Willison

Comment: There's No Limit to How Bad Code Can Get

6th September 2026 Comment My comment on There's No Limit to How Bad Code Can Get — Lobste.rs [In reply to a comment about burning it down to start from scratch when technical debt becomes overwhelming] In my experience it's so rare for tha

Simon Willison

5 Sept 2026

Simon Willison

Using Blender with coding agents on macOS

Modern frontier models have got really good at using Blender. I've been having a lot of fun trying this out recently - models can produce .blend files you can edit in Blender itself, and can also render images and even movies (by rendering

Simon Willison

4 Sept 2026

Simon Willison

The Pelican comparison grid for Astra is pretty interesting

I got access to GPT-6 Astra this afternoon, so naturally I used it to generate SVGs of pelicans riding bicycles - at low, medium, high, xhigh and max reasoning levels (Astra doesn't support reasoning=none). Then I rendered those pelicans in

Simon Willison

4 Sept 2026

Simon Willison

OpenAI's rogue agents were caught communicating via public wikis

Here we go again... Discovery of a new OpenAI agent message board by Sydney Von Arx, Cormac Slade Byrd, Spencer Kitts, and Thomas Larsen describes the latest accidental cyberattack by models being trained by OpenAI. This time it was agents

Simon Willison

1 Sept 2026

Simon Willison

Claude Fable 5.1 made me a really nice animated pelican

Today is Claude Fable (and Mythos) 5.1 day . Anthropic say that Fable 5.1 "sets a new standard for coding, knowledge work, and long-running problem-solving tasks". Their announcement spends a notable amount of time on scientific research, b

Simon Willison

30 Aug 2026

Simon Willison

Understanding ChatGPT Work

OpenAI announced ChatGPT Work on July 9th, and have been furiously iterating on it ever since. It is an extraordinarily confusing and very powerful product. Here's what I've figured out about it so far. ChatGPT Work is actually two products

Simon Willison

27 Aug 2026

Simon’s analysis and correctionResearcher’s controlled test

Breaking Claude Code Opus 5 Auto Mode

Breaking Claude Code Opus 5 Auto Mode . Anthropic are putting a great deal of faith in Claude Code's auto mode for protecting their coding agent users against prompt injection attacks. They recently made that the default and have made bold

Simon Willison

25 Aug 2026

Simon’s notesEVE migration report

EVE Online: The Move to Python 3 Begins!

EVE Online: The Move to Python 3 Begins! ( via ) EVE Online has been one of the most interesting case studies in Python at scale for over twenty years now. They've been running on Stackless Python since their launch in 2003, and their last

Simon Willison

21 Aug 2026

Simon · Stop Making TUIs

Stop Making TUIs

Stop Making TUIs . Thomas Ptacek advocates for building real native user interfaces for even the smallest of personal tools, because coding agents have reduced the cost of getting a usable-enough GUI up and running to almost nothing. I wrot

Simon Willison

20 Aug 2026

Prototype and measurementsBun 1.4 release

Research: A shot-scraper-style JSON API on Bun 1.4's new Bun.WebView

20th August 2026 Research A shot-scraper-style JSON API on Bun 1.4's new Bun.WebView — A zero-dependency, roughly 150-line TypeScript service demonstrates that Bun 1.4’s experimental `Bun.WebView` can provide a shot-scraper-style JSON API f

Simon Willison

19 Aug 2026

Simon’s selectionJeremy Morrell’s essay

A quote from Jeremy Morrell

19th August 2026 My hypothesis is that there is a new opportunity for Extensible Software on the web . LLMs radically lower the cost of authoring extensions, and modern sandbox primitives lower the deployment cost and provide good security

Simon Willison

19 Aug 2026

Simon Willison

Conceptual integrity and counting lines of code

Last week I recorded an episode of the Talking Postgres podcast with Claire Giordano on the subject of "How AI is changing software development". We had a really great conversation. Here are a couple of my highlights from a lightly edited t

Simon Willison

14 Aug 2026

Simon WillisonDoug Turnbull

Don’t classify. Hallucinate!

Don't classify. Hallucinate! I still have quite a bit of older content on my blog that I never got round to tagging. My blog has 1,856 tags - likely too many to feed to an LLM in one go and say "which of these tags match the following conte

Simon Willison

11 Aug 2026

Simon Willison: Stealing Reasoning TracesStolen Thoughts: original research

Stealing Reasoning Traces from Proprietary LLM APIs

Stealing Reasoning Traces from Proprietary LLM APIs ( via ) A vanity domain name ( stolen-thoughts.com ) for a neat paper : Anthropic, OpenAI, and Google return encrypted chain-of-thought blocks to clients that can be replayed across sessio

Simon Willison

10 Aug 2026

Simon’s hands-on testsMeta · Model and deployment details

Introducing Muse Glimmer

Introducing Muse Glimmer ( via ) Meta are back in the open weights game! Muse Glimmer is a brand new 30B model under a clean Apache 2.0 license (a step up from the janky Llama licenses of old). They claim to have optimized it for exactly th

Simon Willison

9 Aug 2026

Simon’s broken workflow and fixGitHub retirement notice

GitHub Models is now retired

GitHub Models is now retired . I missed this news until today, when the GitHub Actions run for my simonw/research repository failed with this error message: GitHub Models is temporarily unavailable as part of a scheduled retirement brownout