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Simon Willison

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Sharp, daily notes on LLMs and building with them.

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SWSimon WillisonPro

A new feature for my blog, built using my voice

I shipped a new feature for my blog today: the Newsletters page, which offers an index of all of the newsletters I've sent out, both my free weekly Substack and my monthly sponsors only updates. I built the feature almost entirely using my voice, chatting away to my laptop while I cooked dinner. Codex voice mode I…

AI & ML6 min read
SWSimon WillisonPro

Claude Haiku 5.5

As previously promised , here's Anthropic's new fast, low cost model: Introducing Claude Haiku 5.5 . The previous Haiku, 4.5, was very much showing its age. It came out almost a year ago , and was priced at $1/million input and $5/million output relatively expensive even back then, and a full 10x the price of…

AI & ML3 min read
SWSimon WillisonPro

OpenAI DevDay 2026 live blog

I'm at OpenAI DevDay today, in Fort Mason, San Francisco. Same as last year I'll be live blogging the keynote and some other notes during the day. OpenAI gave me a free ticket and a seat in the "creator" area for the keynote. You are only seeing the long form articles from my blog. Subscribe to /atom/everything/ to…

AI & ML15 min read
SWSimon WillisonPro

2026 in LLMs (so far)

On Friday I gave the closing keynote at the WeAreDevelopers World Congress North America in San Jose. I tied together the key trends from the past year into a chronological exploration of everything that happened in 2026. The video is on YouTube ; here are my annotated slides and notes to accompany the talk. And as…

AI & ML22 min read
SWSimon WillisonPro

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 all of these new models, but here are my impressions so far. GPT 6 Sol and Luna…

AI & ML6 min read
SWSimon WillisonPro

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'd asked for, as both an embedded visualization and downloadable GPX file and…

AI & ML2 min read
SWSimon WillisonPro

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 week. This time they're noting that it looks very likely that an OpenAI agent…

AI & ML3 min read
SWSimon WillisonPro

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 Problems that have been subject to a $1,000,000 prize since May 24th, 2000. The…

AI & ML5 min read
SWSimon WillisonPro

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 a comparison grid with GPT 5.6 Sol, Terra, and Luna, and beyond being fun the…

AI & ML2 min read
SWSimon WillisonPro

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, boasting of a 52.6% score on the brand new Terminal Bench Science 0.1 benchmark…

AI & ML5 min read
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